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NASA TECHNICAL TRANSLATION NASA TT P-15,533 



RESULTS AND INFORMATION OBTAINED REGARDING AERODYNAMIC JET 
INTEREERENCE ASSOCIATED WITH THE Do 31 V/STOL JET TRANSPORT 
AIRCRAFT AND THEIR APPLICATION TO FUTURE V/STOL DEVELOPMENT 

D. Welte 

iIAS£-^I-J-15533) i<ESULiS AND INFORtiaTIOW 1374-20669 

OBIAItlED BEGAHDIWG AEiODYI^iAMIC JET 

IMIESFEJ^EHCE ASSOCIATED WITH THE Do 31 rmr^l ^r 

V/STCL JET T5AMSPCBT (Kanner (Leo) VfXtT 

associates) 14? p HC $10.50 CSCL OIC G3/02 _ 36288 



Translation of "Ergebnisse und Erfahrungen zur Aerodynamischen 

Strahllnterferenz belm VSTOL-Strahltransportflugzeug Do 31 und 

Ihre Anwendung auf zukiinftige VSTOL-Entwlcklungen," Dornler- 

Werke G.m.b.H., Priedrichshafen (W. Ger.)j 

BMVg-PBWT-72-22, 1972, I83 pages 




NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON, D,C. 205^6 APRIL 1974 



STANDARD TITLe PAGE 



1. Report No. 

NASA TT F-15.533 


3. Govarnnianl Accassion No. 


3. Rocipiant's Cofolog No. 


4. Tiri, and Subtiilo RESULTS AND INFORMATION OBTAINED 
REGARDING AERODYNAMIC JET INTERFERENCE ASSOCI- 
ATED WITH THE Do 31 V/STOL JET TRANSPORT AIR- 
CRAFT AND THEIR APPLICATION TO FUTURE V/STOL 
nFVPT.DPMFNT 


5. Report Data . 

April 1974 


A. Perfornning Orgoniiotidn Coda 


7, Author(s) 

D. Welte, 

Bonn Bundeswehramt 


8. Porforming Orgonitotlon Report No. 


10. Work Unit No. 


1). Contract or Grant No. 

NASw-2481 


9. Porforminj Organi lotion Nam* and Addreia 

Leo Kanner Associates 

Redwood City, California 94o63 


13. Type of Report and Period Covered 

Translation 


)2. Sponsoring Agancy Nome ond Addrai* 

National Aeronautics and Space Adminis- 
tration, Washington, D.C. 205^6 


14, Sponsoring Agvn^ y Cods 


]5, Supplemeniary Noivs 

Translation of "Ergebnisse und Erfahrungen zur Aerodynamls- 
chen Strahllnterferenz beim VSTOL-Strahltransportflugzeug 
Do 31 und ihre Anwendung auf zukiinftige VSTOL- 
Entwicklungen," Dornier-Werke G.m.b.H., Frledrichshafen 
(W. Ger.), BMVg-FBWT-72-22, 1972, 183 pages 


16. Ah.troct The most important results concerning jet interference 
effects for the Do 31 aircraft, resulting from wind tunnel 
model measurements and flight tests, are presented, and an 
estimation is given of Jet Interference effects for future 
V/STOL project studies. Calculations are based on a single 
semi-empirical method for determination of jet-induced lift 
loss in hovering for simple configurations such as the Do 31, 
and it is possible to calculate the lift loss to within 1% 
accuracy. The investigation of the Jet-induced flow field 
around the Do 31 during hovering with ground effect and in 
the transition flight regime yielded a rough estimation of 
the jet intereference effects for future V/STOL studies. 


17. Kay Words (Selected by Autti(»r(f)) 


IS. Distribution Statemant 

Unclassified-Unlimited 


19. Sacurity Clossif. (of this raport) 

Unclassified 


20, Sacurily Cloisif, {of thic pogo) 

Unclassified 


21. No. ofPogo* 

14^1 

1 


n. Prie.' 



NASA.HQ 



TABLE OF CONTENTS 

Page 

I. THE SIGNIFICANCE OF AERODYNAMIC JET INTERFERENCE TO 
V/STOL ENQINEERING, BASED ON EXPERIENCE OBTAINED 
FROM Do 31 DEVELOPMENT AND FLIGHT TESTING 1 

1. The Significance of Jet Interference Associated with 

V/STOL Aircraft 1 

2. Jet Interference Associated with the Do 31 ^ 

3. Jet Interference Associated with Future V/STOL 

Aircraft 8 



II. MAJOR RESULTS ON AERODYNAMIC INTERFERENCE OBTAINED 
PROM Do 31 DEVELOPMENT AND PLIGHT TESTING AND THEIR 
APPLICATION TO FUTURE V/STOL AIRCRAFT 

1. Jet Interference Model Measurements Performed During 

Do 31 Development and Testing 12 

2. Preparation of Measurement Data for the Balance of 

Forces and Torques In Do 31 Transitions 31 

3. Evaluation of Representative Do 31 Transitions with 
Respect to Jet-Induced Forces and Torques, and Compari- 
son with Model Measurements 47 

4. Guidelines for Model Tests for Future V/STOL 

Development 93 

5. Basic Material for Estimating Jet Interference In 

Hover and in Transition for Future V/STOL Aircraft 109 

6 . Summary 1 4 6 



R.3CK-::;WG .^KOrE BjjANK I^jCI' '::-llM-&) 



li 



RESULTS AND INFORMATION OBTAINED REGARDING AERODYNAMIC JET 
INTERFERENCE ASSOCIATED WITH THE Do 31 V/STOL JET TRANSPORT 
AIRCRAFT AND THEIR APPLICATION TO FUTURE V/STOL DEVELGFIVIENT 

Dieter Welte, 
Bonn Bundeswehramt 

I. THE SIGNIFICANCE.OF AERODYNAMIC JET INTERFERENCE TO V/STOL /2^ 
ENGINEERING, BASED ON EXPERIENCE OBTAINED FROM Do 31 
DEVELOPMENT AND FLIGHT TESTING 

1. The Significance of Jet interference Associated with V/STOL 
Aircraft 

In the design, development and operation of vertical or 
ultrashort takeoff aircraft, new types of problems, relative to 
conventional takeoff aircraft, occur which are based on the 
type of propulsion system or on the generation of thrust through 
the use of power plant jets directed downward. 

The flow fields ge.nerated by these downward-directed power 
plant Jets are the cause of effects associated with V/STOL air- 
craft takeoff s and landings, known as 

— recirculation 

— ground erosion 

— jet Interference. 

The Influence which these effects have on the operation, 
characteristics and performance of the aircraft is a function of 

— the configuration of the aircraft (aircraft geometry 
and arrangement of power plants) and 

— the type of power plant Jets (lift generated by 
rotor, propeller, lift fan, bypass or single-stage power 
plants of various Jet Intensity). 

Aerodynamic jet interference, or Jet interference for short, /3_ 
refers to the effect on external aircraft aerodynamics due to the 
power plant Jets. The cause of this effect is the secondary flow 
Induced by a jet and the interaction of several power plant Jets 
close to the ground. 

* Numbers In the margin Indicate pagination in the foreign text. 



Jet Interference produces different effects during various 

VIOL phases of flight, i.e. 

— in hover in the Immediate vicinity of the ground 
(first phase of takeoff, last phase of landing) 

— in hover above the ground effect (vertical takeoff 
and landing) 

— in transition flight (takeoff and landing transitions). 

In hover close to the ground, the jet effect is due to the 
three factors shown in the illustration below: 




— sink effect 

— fountain develop- 
ment 

— suction effect 
(not visible here) 



The sink effect is produced by turbulent jet mixing with 
the surrounding air and primarily generates an underpressure 
region on the underside of the aircraft. Between neighboring 
power plants or groups of power plants, energetic exhaust gas 
fountains from the ground flow against the underside of the air- 
craft and produce an upward force. Power plant Jets which flow 
between the ground and the underside of the aircraft produce an 
additional downward force due to the suction effect. The three 
effects are superimposed on one another in quite different 
manners in each individual case. 

In hover beyond the ground effect, only the sink effect 
occurs. 

In transition flight, beyond the ground effect. Jet inter- 
ference can be broken down into a near field and a far field 
effect. As outlined in the Illustration, 

— blockage, 

— the wake, and 

— the lowering effect 



/U 



are operant in the near field and 
— downwash Induction 



is operant in the far field. 




Key: a. Near field 
b. Far field 



ference generally causes a do 
torque during transition flig: 
their relatively high air thr 
the inlet flow must also be t 



The blockage of 
flow about the air- 
craft by the presence 
of the jet produces 
a relatively small 
change in pressure 
distribution in the 
near field. There is 
an area of reduced 
overall pressure in 
the jet wake, which 
primarily has its 
effect in a slight 
increase in aircraft 
drag. If the control 
surfaces are located 
in the jet wake, flight/ 
stability, is also 
Influenced. 
The sink effect pro- 
duces a downwash 
in the near field. 
A downwash field is 
induced in the far 
field by jet mixing 
and jet deflection. 
Overall, jet inter- 

wnward force and a tall-heavy /5. 

ht , When lift fans are used, with 

oughput , the interference effect of 

aken into consideration. 



All of the Jet interference effects described generally 
reduce the power and the controllability of a V/STOL configura- 
tion. During vertical takeoff, the balance of lift must be 
positive after the subtraction of all losses so that the aircraft 
can leave the ground. A second condition for vertical takeoff is 
provision for the failure of the critical power plant. The 
balanced residual lift must ensure a safe landing. Disruptive 
torques caused by jet Interference are generally small at zero. 
forward speed. 

In transition flight, lift loss and disruptive torque nor- 
mally increase linearly with aircraft speed at first, starting 
from the value for the hover state; these then become flatter and 
can decrease again toward the end of the transition phase. Since 



aerodynamic lift and aerodynamic control torque Increase as the 
square of air speed, a certain critical speed exists at which 
residual thrust and/or residual control torque reaches a 
minimum. 



4 



a 
Kraft in 
z-Richtuny 



d 



aerodynamischei 
Auftrieb 




(Vertikalschub + aer. A; ' rieb) 
- Gewicht 



Resthubkraft 
fUr ManOver 



strahllnduzlerter 
Hubverlust 



HubverlusI 
belm Schwfiben 



b Fluggeschwindlgkeit 

Key: a. Force in z-direction 

b. Aircraft speed 

c. Aerodynamic lift 

d. (Vertical thrust + aerodynamic lift - weight) 

e. Residual lift for maneuvering 

f. Jet-Jinduced lift loss 

g. Lift loss in hover 



Since a res 
sary for the exe 
aircraft approva 
AGARD), an exact 
tant. Aircraft 
relative to one 
tion are the slg 
of residual lift 
speed. 



Idual control torque and a residual lift neces- 
cution of flight maneuvers are defined in the 
1 regulations or recommendations (e.g. FAA, 

knowledge of Jet interference effects is impor- 
Gonflguration, the position of power plants 
another, power plant thrust ratio and jet direc- 
nlflcant parameters which determine the magnitude 

and residual control torque and the critical 



/6 



2. Jet Interference Associated with the Do 31 

The aerodynamic problems which occurred in connection with 
jet interference during Do 31 development were solved primarily 
by experimental means. The jet-induced forces and torques in 
hover and transition flight, with and without ground effect, were 
measured in the wind tunnel. 



Lift loss In hover outside of the ground effect Is about 
3.5% of gross thrust and Increases to a maximum of 8% as the ground 
Is approached. An important point Is the failure of a cruising 
power plant. Lift loss Is reduced to about 2% outside of the 
ground effect, since the cruising power plant which has failed, /?. 
mounted under the Inboard wing, induces greater losses than a 
lift power plant, suspended at the wing tips. Loss increases 
somewhat more steeply as the ground is approached, however. The 
jet-induced torques are small In hover with and without the ground 
effect as measured with the available control torques. 



Kubverlust 
AS ^ 




lOn 



20r' 



3 On 



Bodenabstand K (m] 



Key: a. Lift loss 

b. Ground distance 

c. Vertical takeoff 

d. Failure of cruising power plant 
S = Thrust 



The measured lift losses are taken Into consideration in 
compiling the balance of lifts and/or in determining maximum 
vertical takeoff weights. The cases indicated in the table below 
are decisive In the limitation of maximum vertical takeoff 
weight In the Do 31. 



In the first case, S% is used for lift loss due to jet 
interference. In addition, a lift loss due to the increase in 
inlet temperature caused by recirculation must be taken into 
consideration. The critical case is the failure of a cruising 
power plant during the takeoff process. Under the condition of 
an oblique point takeoff, a reliable emergency landing is ensured 
with a residual lift of 9^% of aircraft weight. During an oblique 
point takeoff, the aircraft climbs away from the takeoff point 
along a path inclined at 25°. In this case, the values outside 
the ground effected are used for loss figures. 



Case 



Thrust 
requirement 



Thrust loss 
due to Jet 
interfer- 
ence 



Increase in 
inlet tem- 
perature 



Max. verti- 
cal take^^ 
off weight, 
H = 600 m^ 
ISA 



1. VTO 

All power 
plants in- 
tact 



P 



tot 



max 



Wt 



= i.o: 



|^=8i 



ATcpp = 15*C 



ATj-pp = 5°C 



21i000 kg 



. VTO 

one cruising 
power plant 
fails 



F 



•Res 
Wt 



= 0.95 



r = =i 



Zero 



19,530 kg 



In Do 31 transition flight, the change in normal force and 
pitch torque due to Jet interference initially varies as a linear 
function of aircraft speed. The change in normal force becomes 
flatter with Increasing aircraft speed and reaches a value of 
10 to 12^ of total thrust at about the middle of the transition. 
The change in normal force during transition flight involves no 
limitation on the maximum vertical takeoff weight of the Do 31, 
since the above-mentioned. ^condition for vertical takeoff and for 
power plant failure Is appreciably less favorable for oblique 
point takeoff. 



/8 



0,12 




Fluarieschwindioheit v [n/s] 



Key; a. Aircraft speed; b. Lift loss; c. Change in 

pitch torque; d. Landing transition, wind tunnel 
measurements; S = thrust , 



Extreme control-surface positions are necessary to trim the 
jet-Induced pitch torque during the transition. The figure below 
shows the curve of elevator angle during the landing transition 
by the Do 31 E3. 



a 12 

Hohenruder- 
Aus^chlag 



n 



H 
lOJ 



Do 31- 


a 

E3 Flun 


247 




Landet 


ransitic 


n 






a 

— B 


/ 


^^9 




\ 


/ 









Key: 



O 20 40 60 BO 

t'lumeschwlndiqkeit v [n/sj 

a . Elevator angle j.*.' :-:-..:. aj ; 

b. Aircraft speed 

e. Plight 247, landing 
transition 



Elevator angle is 
coupled with the gate 
of the tail control 
nozzle. At rijj = 12. 5° j 
the tail control nozzle 
is wide open and 
delivers maximum control 
thrust. The elevator 
can be angled even 
farther. Its effective- 
ness drops off beyond 
about hh - 16°. We see 
that up to half of the 
available control 
torque is required to 
compensate for jet- 
induced pitch torque 
during transition. This 
example shows that jet 
interference Is a 
factor which is not to 
be underestimated in the 
design of future V/STOL 
aircraft. 



/9 



The measurement of jet-induced forces and torques in the 
wind, tunnel made the development of new test techniques neces- 
sary. Model and measurement engineering are presented with 
unconventional tasks. Two wind tunnel models were built and had 
measurements performed on them during the course of Do 31 develop- 
ment. One model was equipped with electrically driven model motors. 
In the second model, compressed air was discharged to simulate 
jets. The latter method proved to be the more effective. It is 
also to be recommended for interference studies on future V/STOL 
aircraft for the case of zero forward speed. 

A series of takeoff and landing transitions with the Do 31 E3 
test aircraft were analyzed with regard to forces and torques. 
Algorithms programmed for the IBM 3^0 were developed which 
calculate instantaneous thrusts, weight and aerodynamic quantities 
from the measured data. The thrust and torque balance yields the 
jet-induced forces and torques as residual terms. Since a 
relatively small difference between several larger numbers is 
involved, extremely high requirements are placed on the accuracy 
of the dataj- but are not always satisfied. 



/lO 










Agreement between the results of wind-tunnel and flight tests 
Is not satisfactory for all flight states; It Is justifiable to 
conclude, however, that wind tunnel measurements can be reliably 
applied to the large-scale design. 

A prerequisite for applicability is that, in addition to 
geometric similarity, the momentum densities of thrust and on- 
coming flow be proportional In 'the model and in the full-scale 
design. 



3. Jet Interference Associated with Future V/STOL Aircraft 

Due to their importance in the designing of a V/STOL air- 
craft, data on the effects of Jet Interference upon flight 
performance and characteristics are necessary -while still' In the 
early development stage. 

A generally valid calculation of jet-induced forces and 
torques Is possible only for the case of hover outside the ground 
effect. An empirically determined relation can be given between 
lift loss AP/F, the ratio of aircraft equivalent diameter D to 
nozzle diameter Dj , and the decrease In stagnation pressure along 
the jet axis. The Mach number effect in free Jet propagation is 
taken into consideration with an additional term In the form of 
the ratio of overall Jet pressure Pq to static ambient pressure 
p„. A value of about K = O.OI36 is obtained for the constant 
from model measurements. 

During vertical takeoff, vertical landing, or hovering close 
to the ground, the fountain effect is superimposed on the sink 
effect, and Its influence on the forces and torques can only be 



/ll 



given In terms of trends for a given V/STOL configuration. The 
pattern of flow on the ground, including the positions of stagna- 
tion points- or stagnation lines, and the directions of ascent of 
the fountains can be roughly determined from simple momentum con- 
siderations, so an estimate of the order of magnitude of negative 
or positive changes in lift and head- or tail-heavy torque- is 
also possible. The flow field close to the ground is relatively 
easily influenced by small changes in the nozzle angles or in 
aircraft inclination. Upwash and thus the balance of forces and 
torques can be effected with relatively small control surfaces on 
the fuselage. Thus we still have possible means of effecting 
changes even in advanced stages of development without having to 
basically alter configuration. In civilian applications, it is 
possible to use gratings as takeoff surfaces. These serve pri- 
marily to lead of the hot exhaust gases; in addition, however, 
they also cause interference to be reduced to the case of hover 
outside the ground effect region. 



-0,64 



&F 



= K 



5 r_o\ 



(P -p ) 



3(^ ) 



*D 



<- ) 



i max i w 



2:t 



jCJV^JT"^. D = -J [ (r{G)-|Dj)da 



1{x) 



—iD 



•■ 



p q (x) 

o 




The figure below shows the results of measurements performed 
on models: change in lift due to Jet interference on various 
VTOL aircraft as a function of altitude. 



/12 



We are so far still a long way from being able to give 
the design engineer satisfactory data on Jet Interference, with- 
out prior wind tunnel measurements, for the case of transition 
flight. Although there are a number of potential-theory formula- 
tions which include the blockage and sink effects of a Jet 



/13 






-f^ 



a 
HShs 

[ m 1 






OH 


I 
129 












i 














I 


^ 







1 Jaw 


>60 


li 














\ 





P1127 
I 




1 


1 

Bell 0188A 




[ 




• 




\ 


\ 


\ 








) 



5 10 IS -S 



5 to -5 



S 10 IS 



Hubonderung infolge StroMintirfer«nz C*A] 



Key: a. Altitude 

b. Change In lift due to jet Interference 



and yield the Induced velocity fields the model representations 

are still not quite true to reality, and the suction effect and 
deformation of the Jet must be knovm front measurements. This 
theory breaks down for power plants arranged in groups on the 
aircraft. Information is lacking with regard to the propagation 
of groups of Jets with different impinging flow. 

A summary of wind tunnel measurements performed on various 
V/STOL configurations by the British Aircraft Corporation and by 
Dornler is given in the figure below to provide an overview of 
the order of magnitude of aerodynamic Jet Interference In 
transition flight. 



10 



±^ Ju 



Do It 




eff. Fluggeschw.-Verh. (v»/Vj)g 



Key: a. Lift loss 

b. Effective velocity ratio 
S = thrust 



The closer to the margin of the airframe the power plants are 
located, the smaller jet Interference is. The jet-induced torques 
exhibit similar trends . The power plant component makes up about 
half of the overall change in torque in the Do 31 • 

Future V/STOL transport aircraft will: iprlmarily employ dual- 
stage power plants with high bypass ratios or lift fans for the 
generation of lift. Due to the relatively high air flow rate, 
not only the thrust Jet but also the inlet flow produces an 
interference effect. In hover, with or without ground effect, the 
Influence of inlet flow upon the balance of forces and torques is 
still small. Only In transition can changes in torque about the 
transverse axis and, during side slip, also about the longitudinal 
axis occur as the result of inlet flow. Interference tests in 
transition should therefore include not only the simulation of 
power plant jets but also that of inlet flow. On the basis of 
the present state of the art, it is recommended that power plants 
be simulated by means of fans driven electrically via extension 
shafts. 



/14 



11 



II. MAJOR RESULTS ON' AERQDYHAHIC INTEBFEREIICE- OBTAINED- FROM Do 31 /1 5 
DEVELOPMENT AKP PLIGHT' TESTING' AND' THEIR APPLTCATION TO 
FUTURE V/STOL AIRCRAFT 

1. Jet Interference Model Me'asurements Performed During Do 31 /l6 
Development and Te sting 

Overview of Contents 



1.1. Introduction 

1.2. Notation 

1.3. Measurement with the 1:6 Model 
l.H. Measurements with the 1:20 Model 
1.5. References 

Figures 

1.1. Do 31 1:6 jet interference model. 

1.2. Do 31 1:6 Jet interference model in the PKFS wind tunnel. 

1.3. Do 31 Jst interference in hover close to ground. Lift 
loss, pitch torque, roll torque. Configuration for 
vertical takeoff. 

1.4. Do 31 Jet interference in hover close to ground, with /17 
power plant failure. Starboard cruising power plant has 
failed. Residual thrusts in torque equilibrium. 

1.5. Do 31 Jet interference model, 1:20, three views. 

1.6. Test setup with the Do 31 Jet interference model, 1:20, 
in the Dornier wind tunnel, Immenstaad. 

1.7. Do 31 Jet interference in hover close to ground. Effect 
of cruising power plant nozzle angle on loss of 
thrust. 

1.8. Do 31 Jet interference in hover close to ground. Effect 
of cruising power plant nozzle angle 'on change in torque. 

1.9- Do 31 Jet interference in transition. Lift, pitch torque. 
All power plants on takeoff thrust. Angle of attach 
a = 0°. 

1.10. Do 31 Jet-induced downwash at location of lift power plant 
in transition. All power plants on takeoff thrust. 
Cruising power plant nozzle angle tjv[tt^ = 90°. Angle of 
attack a = 0° . 



12 



1.11. Do 31 Jet-induced neutral point shift, in transition. 
Conditions as in Fig. 1.10. 

1.12. Do 31 jet interference during short takeoff. Lift, 
drag, pitch torque. All power plants on takeoff thrust. 
Ground - to - landing gear distance H/b = 0.025 
Angle of pitch ^ Z ^° 

CPP nozzle angle t^MTW ~ 1°*^ 

LPP nozzle angle thtw ~ '^'^° 

Landing flap angle r\^ = iJ5° 

Angle of attack a = 0° 



13 



1.1. Introduction 



/18 



Wind tunnel measurements are an indlspenslble aid In the 
development of an aircraft. This Is particularly ti'^e for a 
V/STOL project, since certain flow processes can practically be 
determined here only by experimental means. In particular, the 
problem involves the phenomena known as jet interference and 
recirculation. 

Jet interference measurements yield the changes in forces, 
torques and points of force application in all phases of flight 
and all attitudes; these changes are important for the mechanics 
of flight. During the developmental phase of the Do 31, these 
measurements were carried out in the Stuttgart wind tunnel with 
a 1:6 model. A major portion of the measurements were devoted 
to the vertical takeoff and vertical landing phases, particularly 
important in flight testing, including a simulated power plant 
failure. The most important results are reported in Section 1.3. 

In a second phase of jet interference measurements which 
approximately coincided in time with the beginning of flight 
testing, the entire range of transition flight of the Do 31 was 
studied, particularly with regard to comparison with flight test 
results. The measurements were carried out in the Dornier wind 
tunnel with a 1:20 model. The most important results are reported 
In Section 1.4. 



1.2. Notation 


A 
b 


Cm 


P 
H 

M 




So 

Voo 
^j 




<v«Aj>e 


= 




2 




llvJPj 


1 





/19 



Aerodynamic lift 

Wing span 

Aerodynamic coefficients of lift, drag and pitch 

torque, respectively 

Reference area for wing 

Distance between landing gear and ground 

Mean aerodynamic wing chord length 

Roll torque 

Pitch torque 

Gross thrust 

Aircraft velocity 

Jet velocity 



Effective velocity ratio 



ct 



Angle of attack 



14 



b 


= 


2. 


.83^ 


m 


F 


= 


1. 


,581 


m^ 


^u 


= 


0, 


■ 570 


m 



(f) Angle of roll 

e Angle of pitch 

T Angle of power plant nozzle rotation (t = 0*^ for 

jet exhausting rearward) 
n^- Angle of split flaps 

1.3' Measurements with the 1:6 Model /20 

The 1:6 model of the Do 31 was designed for the large PKPS 
(Research Institute for Motor Vehicles and Vehicle Motors) wind 
tunnel, Stuttgart (4.8 x 7.2 m2 ) and had the following principal 
dimensions: 

Span (to center of lift power plant pod) 

Wind area 

Mean aerodynamic chord 

Fig. 1.1 shows two views of the model, and Pig. 1.2 shows a 
photograph of the model installed in the wind tunnel, including a 
wooden panel used for ground simulation. 

The cruising power plants were simulated with electrically 
driven axial compressors with a rated power of 20 hp each at 
20,000 rpm. The lift power plant pods were equipped with three 
outlet nozzles, corresponding to the earlier design. Thrust was 
generated by one crossflow fan per lift pod, driven by a medium 
frequency motor at a reduced speed of m = 8500 rpm. The tests 
were conducted primarily with the following thrusts: 

2 lift power plant pods = 9.36 kp Gl kp = 1 kg force] 

2 cruising power plant pods = 14.20 kp . 

The power plants were rigidly connected to the model. The 
electrical lines were led out of the tail of the fuselage via 
a system that followed the angle of attack. 

The lower portion of Fig. 1.2 shows a photograph of the 
power plants mounted on the calibrating frame. This made it 
possible to determine power plant thrusts outside the airframe. /21 
The jet-induced forces and torques were determined from the dif- 
ference between model measurement and thrust measurement. 

Pigs. 1.3 and 1.4 show the most important results from the 
measurements. Jet-induced lift loss, pitch torque and roll- torque 
are plotted against ground distance in Pig. 1.3- As long as the 
landing gear Is in contact with the ground, lift loss amounts to 
8% of gross lift. After liftoff, lift loss decreases relatively 
rapidly and remains constant at 3 to 3'5% at a distance of 1 wing 
span or more from the ground. 

15 



Pitch torque Is slightly nose-heavy in the immediate vicinity 
■of -the ground but has a' stabilizing effect when changes in the 
angle of pitch occur. It drops off rapidly upon liftoff and 
yields a constant, relatively low tail-heavy torque beyond 4 or 
5 m. Maximum available Jet control torque Is 



M/CSq-A^) = ±0.125. 

Roll torque has an unstabilizing effect when an angle of 
roll exists, but is relatively small compared to the maximum 
available control torque of L/Sq • b/2 = ±0.17 and decreases with 
altitude above ground. The zero point shift at (|> = 0*^ is due to 
the asymmetry of the flow field. Pig. 1.4, analogous to Pig. 1.3, 
shows conditions accompanying failure of the critical power plant, 
i.e. the cruising power plant in the case of the Do 31 • The 
thrusts of the remaining power plants are suitably throttled or 
increased to emergency thrust levels in order to maintain torque 
equilibrium. ,Llft loss outside the ground effect has dropped to 
about 2%. The reason for this is that the lift power plant jets 
produce less lift loss, in relative terms, than the cruising power 
p lant . 

The measurement results have been incorporated into the /22 
balances of lifts which were used to determine maximum vertical 
takeoff weights. Aside from a strength limit, two requirements 
had to be met here: 

a) Por vertical takeoff, excess thrust was to amount to 
at least 3% of takeoff weight; among other things, the loss 
for jet Interference was taken to be B%. 

b) Upon failure of a cruising power plant,, a balanced 
residual thrust of at least 95% of takeoff weight was to 
remain; among other things, the loss due to jet interference 
was taken to be 2% ^ since this case was assumed to occur out 
of ■ ground effect only. 

The corresponding wind tunnel test reports are presented in 
[1-4]. 

1.4. Measurements with the 1:20 Model /23 

The 1:20 model of the Do 31 was built for the Dornier wind 
tunnel (2.20 x 3. 20 m2) and had the following principal 
measurements : 



16 



Span b = 1.24 m 

2 
Wing area P = 0.22 m 

Mean aerodynamic chord Z^ = 0.186 m. 

Fig. 1.5 shows three views of the model. Compressed air 
was blown out of nozzles to simulate the power plant Jets, The 
nozzles, with compressed air lines, were rigidly connected to a 
system which followed the angle of attack and did not make con- 
tact with the Do 31 model. Fig. 1.6 shows the test setup. A 
base panel, 3 m in diameter, adjustable in height and inclination, 
was used for ground simulation. 

A detailed report on the measurements can be found in [5]. 

A summary of the most Important results is given for hover 
in Figs. 1.7 and 1.8, for transition flight in Figs. 1.9 through 
1.11, and for short takeoff in Fig. 1.12. 

Pigs. 1.7 and 1.8 show the curves of lift and torque varia- 
tion with ground distance for three angles of rotation T^pp = 60° j 
90° and 120° for the cruising power plants. The effect of 
angles of pitch which occur in practice during the takeoff and 
landing processes (-10° < 9 < +10°) is indicated by hatched regions. 
The effects of nozzle angle of rotation and the angle of pitch 
are on the same order of magnitude. Overall, however, the dis- 
turbances are no greater than those measured with the 1:6 model 
and can be easily controlled. 

Pig. l.g shows the curves of changes in lift and torque ver- /24 
sus effective velocity ratio. The latter is a parameter commonly 
used in Jet interference studies and is the root of the ratio of 
momentum densities in the oncoming flow and power plant jets. 
The angle of nozzle rotation on the cruising power plants appears 
as an additional parameter. 

At (v„/vj)g = 0, the familiar losses associated with hover 
occur. 

The interference effects of power plant Jets exhausting 
normally from a wing can, in highly simplified terms, be broken 
down into a near field and a far field. In the near field, the 
stagnation of oncoming flow upstream from the nozzle Jet, the 
dead-water region in the lee of the Jet, and the suction effect of 
the Jet lead primarily to a change in the pressure distribution on 
the wing and cause a change in lift and torque. In the far field, 
which might be defined as the region where the Jet is already 
deflected into the oncoming flow to a large degree, the suction 
effect of the Jet induces a downwash field which contributes to the 
change in torque primarily at the elevator. The change in down- 
wash angle at the location of the Do 31 lift power plants was 



17 



determined by the probe-surface method and is plotted against 
effective velocity ratio in Fig. 1.10. 

Fig. 1.11 shows the curves of neutral point shift versus 
velocity. 

Finally, Fig. 1.12 shows the effect of the coefficient of 
thrust upon the aerodynamic coefficients of longitudinal motion 
close to the ground, as required for short takeoff calculations. 

An exact description of the tests is given in [5]. 



18 



REFERENCES 

1. Esch, P., "Do 31 2 Bv wind tunnel tests ^ measurement period II: /25 

measurements with and without thrust," Dornler VW 313-B2. 

2. Esch, P., "Do 31 2 B wind tunnel tests, measurement period III: 

measurements with thrust," Dernier VW 313-B3. 

3. Eschj P.J "Do 31 2 B wind tunnel tests, measurement period IV: 

ground effect measurements," Dornler VW 352-B2. 

4. Esch,"P,, "Do 31 2 B wind tunnel' tests, ■measurement period V: 

ground effect measurements," Dornler VW 352-B6. 

5. Esch, P. and Joes, R., "Do 31 2 B interference and ground 

effect measurements in the DW wind tunnel," Dornler 
VW 537-Bl. 



19 



/26 




^^-o-e- 0> 3 



Pig. 1.1. Do 31 1:6 jet Interference model. 

Key: a. Suspension point 
b. Reference point 



20 



/27 










-r 



r 






f 








.J 












i 








1 










. 




.£^,^ 




liiici 


J 



■■ 





Fig. 1.2. Do 31 1:6 Jet Interference model in the 
PKPS wind tunnel. 



21 




05 



b 1.0 

^^tlTGeitPANNwtilE b 



/28 




S c "JO 15 

liKGSKEtSUNO 4- t*l 



e 0.025 

ROUHOHEHT 

t 
%,' b/1 



-0.025 




f S 

MJUtQEWlKKCl f t*l 



Fig. 1.3. Do 31 jet interference in hover close to 
ground. Lift loss, pitch torque, roll torque. Con-r 
figuration for vertical takeoff. 

Key: a. Lift loss 

b. (Ground- to - landing gear distance)/ (wing span) 

c. Angle of pitch 

d. Pitch torque 

e. Roll torque 

f. Angle. 'Of roll 

g. Unstable 



22 



to 



HUSVERLUST 
-AS 



^T 



t%l 



_ 



/29 




S C 10 15 

lAHSSNEIGUNO ^ 1*1 




S f W - IS 

hAhccwinkcl y r*i | 

Fig. 1.4. Do 31 jet interference in hover close to ground, 
with power plant failure. Starboard cruising power plant 
has failed. Residual thrusts in torque equilibrium. 

Key: a. i iLif t loss 

b. (Ground - to - landing gear distance) 

c. Angle of pitch 

d. Pitch torque 

e. Roll torque 

f. Angle of roll 



23 



IV) 





/30 




1— c-cmasEJ^ id 



Pig. 1.5. Do 31 Jet Interference model, 1:20, three 
views. 

[Note: Commas in numerals are equivalent to decimal points.] 



I ,. 




f^i 



.■<(■ 



_ _^^ I - '■ ■ ■ ■ ' ■ . j. ■•-.*■;* ,, 



w::^^-^ 




Fig. 1.6. Test setup with the Do 31 Jet interference model, 
1:20, in the Dornler wind tunnel, Immenstaad, 



/31 






Key: a. Wind tunnel nozzle 






Abstond Baden- Fahrwerk H/b 

l.t 1j6 18 2.0 




{32 



Fig. I.7. Do 31 Jet Interference in hover close to ground. 
Effect of cruising power plant nozzle angle.. All power plants 
on takeoff thrust. Angle of pitch: -10*',< < +10''. 



Key: a. Lift loss; ti . Ground - to - landing gear distance; 
c. Cruising power plant nozzle angle 



0.03 



^ 0.02 
Momcnten- 
onderung 

AM 

^'^»* OJOl 



■ 0J)1 



-0X12 



-a03 



■OJOt. 




/33 



IV) 



pig, 1,8» Do 31 jet interference In hover close to ground. 
Effect of cruising power plant nozzle angle. 

Key:, a. Change in torque 

b. Ground - to - landing gear distance 
c^ All power plants on takeoff thrust. Angle of 
pitch: . . . 



MTW-Dusenwinkcl tf-^TW ~ 




/34 



0.30 



0.10 OJS 0.20 02$ 

^ GtschwifidigJteitsvefhaltnis (v«,/vj)^ 

Pig. 1.9. Do 31 Jet interference in transition. Lift, 
pitch torque. All power plants on takeoff thrust. Angle 
of attack a = 0^. 

Key: a. Lift loss 

b. Change in pitch torque 

c. Velocity ratio 

d. Cruising power plant nozzle angle 



03Q 



28 



a 10 

Abwindwinkel- 




0.1 b 0-2 

GeschwindigkeitsverhiiUnis {Veo/Vj ]f 



02 



Pig. 1.10, Do 31:. jet-induced downwash at location of lift 
power plants In transition. All power plants on takeoff 
thrust. Cruising power plant nos:zle angle Tjyfrp^ = 90° • 
Angle of attack a = 0°. 

Key: a. Change in downwash angle 
b. Velocity ratio 



/35 



0.1 



"Cm 
dCA 




■0.1 



0.2 



0.3 



at a Q2 

Ceschwindigkcitsverhiiltnis ( Vo) /Vj ), 



f"'t HLW 




Bezugspunkt in 22.5 % l^ 



( ^*o / ^ j )# ■ « -• 



Fig. 1.11. Do 31 Jet-induced neutral point shift, in 
transition. Conditions as in Pig. 1.10. 

Key: a. Velocity ratio 

b. Without lift power plants 

c. With lift power plants 

d. Reference point at 22.5% S'^ 



29 



/36 



t.3 



0.6 



0.4 



0.2 



•0.2 



-0.4 



■0.6 





sis« Ca 












""^ 




\ 


\ 






^ 




/ 


^ 


Cw 


N 


N 


. ^ 


^ 










^ 


V 
















N 


\ 
















\ 


\ 
















\ 



a 10 12 

Schubbetwert 



U 



J_ 



^^ '^ 



16 



_L 



a2oo auo o.ns o.ioo- ooss ooqi cu>75 

Geichwindi^keitsverhoUnis ( v^ / v: ) 



Q070 



Pig. 1.12. Do 31 Jet interference during short 
takeoff. Lift, drag, pitch torque. All power plants 
on takeoff thrust. 

Ground - to - landing gear distance 

Angle of pitch 

CPP nozzle angle 

LPP nozzle angle 

Landing flap angle 

Angle of attack 

Key: a. Coefficient of thrust 
b. Velocity ratio 



H/b = 0.025 
6 = 0° 
TMTW = 10° 
^HTW - 75^ 

a - 0° 



30 



2. Preparation of Measurement- Data for' the' Balance-s' of Forces /37 
and Torques In' DC 31' Transitions 

Overview of Contents 

2.1. Introduction 

2.2. Notation 

2.3. Data Preparation 

2.4. Calculation of Jet Interference 
References 



Tables 



2.1. Do 31 geometry and moments of Inertia 

2.2. Aerodynamic coefficients 



Figures 

2-1. Do 31 E1/E3 test aircraft In flight and on ground. 

2-2. Comparison of gross thrusts for cruising power plants and 
thrust power plants determined by various methods of com- 
putation. Do 31 E3 trial 243, takeoff phase. 

2-3. Comparison of measured and smoothed acceleration in 

z-direction (coordinates fixed relative to aircraft). 
Do 31 E3 trial 243, takeoff phase. 

2-4. Comparison of measured, smoothed and corrected angles of 
attack. 



31 



2.1. Introduction /39. 

The development of a new aircraft generally requires a large 
number of model tests in both the Initial and advanced stages, 
and it provisionally terminates in the testing of a prototype. 
One goal of this testing is also to check information obtained in 
model tests with regard to its usability for the full-scale version. 
This is particularly applicable if new engineering is employed. 

During the course of Do 31 development, jet interference 
proved to be an important factor Influencing VTOL performance and 
flight characteristics. An evaluation of the flight tests 
initially encountered serious problems, however, which stemmed in 
part from the measurement system and in part from the methods of 
evaluation. In the course of time, however. Improvements were 
achieved in both areas, so it was possible to undertake an evalua- 
tion with some promise of success. 

2.2. Notation /M 

C^, C^j Cjy[ Aerodynamic coefficients of lift, drag, and 

torque, respectively 

E Inlet momentum 

F Reference area for wing 

G Instantaneous gross aircraft weight 

g Acceleration due to gravity 

I Moment of inertia 

I Mean aerodynamic wing chord 

'^inter Jet-induced pitch torque 

Mg Pitch torque due to power plant thrust 

Mg • Pitch torque due to inlet momentum 

qn Dynamic pressure in flight, from Pitot tube 

Sq Gross thrust from power plants 

^tot> ^tot Normal accelerations 

q Angular acceleration 

Xg , Zg Distance between center of gravity and reference 

point 

a Angle of attack 



32 



Subscripts 


X,vY, 


Z 


HTW 




MTW 





Cooi?dlnates fixed with respect to the aircraft 
(positive downward and forward) 

Lift power plants 

Lift/thrust power plants (cruising power plants) 

2.3- Data Preparation /^l 

The evaluation of flight tests with regard to jet inter- 
ference proved to be so difficult because the Jet-induced forces 
and torques were obtained as differences between several large 
quantities Cl]. In order to keep error in Jet interference 
small, all measured quantities involved in the calculation had to 
be known with the highest possible accuracy. In addition, it is 
possible to improve the results by suitable mathematical and 
statistical methods. This entire approach is of course also 
applicable to wind tunnel tests and was likewise practiced in the 
initial period, but in the separation of model and power plants 
we find the much simpler possibility here of directly measuring 
Jet interference, at least in hover. 

Reference has already been made to the importance of a high- 
quality measurement system. Decisive improvements could then 
also be made during the course of flight testing, not least of 
all through our own developments. As an example of this. 
Fig, 2-1 shows the Do 31 with attached Dornler Fluglog ["flight- 
log"] for the combined measurement of angle of attack, angle of 
sideslip, and aircraft speed. 

Unfortunately, the Fluglog, in the form In which It was used 
with the Do 31> is also an example of poor data acquisition. In 
the acquisition of aircraft speed, excessive Integration time and 
Imprecisely known access time result ', in time lags 
which are no longer tolerable for this evaluation. For the 
^evaluation of Jet interference, we therefore relied on the deter- 
mination of aircraft speed from dynamic pressure measurements 
which were also carried out, in conjunction with the measurement 
of ambient pressure and ambient temperature. 

Due to its exposed position well ahead of the nose of the c' ■ /42 
fuselage, angle measurements with the Log are inaccurate if the 
aircraft executes rotary movements about its transverse or 
vertical axis. This Inaccuracy is of course particularly serious 
at low aircraft speeds and was therefore corrected during data 
preparation. The effect of this correction is clear in Pig. 2-4, 
about which more will be said in another connection. 

The success of Jet Interference calculations depends upon the 
accuracy of the method for calculating thrust. In the course of 

33 



testing the Do 31, two methods were developed for each type of 
power plant; although these do not agree completely , their accuracy 
is such an Improvement over earlier methods that an evaluation 
appears reasonable. Pig. 2-2 shows a comparison of the various 
methods. In the case of lift power plants, only the rpM method 
can tie considered for jet interference evaluation, since the thrust 
of each power plant is required for the balance of torques, not 
just overall pod thrust as provided by the fuel flow method. In 
the case of cruising power plants, the rpm method yield a some- 
what flatter thrust curve, so the rpm method was selected for 
calculating thrust both for this reason and for the sake of 
uniformity . 

A second important factor in the calculation of jet inter- 
ference is the determination of weight. Weight is determined from 
known takeoff weight and fuel consumption. Unfortunately, a 
shortcoming must be mentioned here, too, as the measurement of 
consumption by the right thrust power plant pod occasionally 
involves error; a slight consumption level is indicated with the 
power: plants not running. Since the evaluation of Jet inter- 
ference is made for relatively short phases of flight, on the 
order of 2 or 3 mln, the errononeous consumption figures were 
taken, and the initial weight for the corresponding phase of 
flight, manually corrected by the difference in consumptions 
between left and right lift pods, was just inserted into the pre- 
paration program. 

In each set of measurements, the data exhibit a certain dis- /43 
persion, and stray values are also possible. The principal goal 
of data preparation is thus to ensure a certain degree of balance. 
If only occasional stray values occur, an appreciable improvement 
can be expected if an adapted smoothing method is used to eliminate 
roughness in the data. The method used here (cf. [2]) uses a 
cubic parabola for smoothing, the coefficients for which are deter- 
mined by the method ®'f least squares. The measured data 
to the left and right of the position being considered are made 
use of here, with all values being assigned a weight corresponding 
to the Gaussian error function. For this purpose, in turn, the 
number of points is preselected, and the interval thereby deter- 
mined is assigned to the so-called 3cr limits. The weights have 
then thereby been determined. Test calculations with different 
numbers of points naturally yielded a smoother curve as the num- 
ber of points was increased. It must be noted, however, that 
actual effects are then also obliterated; for example, rotation 
of the cruising power plants begins with a discontinuity which is 
no longer manifested after smoothing. The number of points was 
taken at 31 for preparation; at a data frequency of 5 Hz — most 
of the recordings earmarked for evaluation are available in this 
form — this corresponds to a time interval of 3 sec before and 
after the point in time which is under consideration. More is 
probably no longer reasonable, since changes in the state of 



34 



flight can be made during this time span by the pilot for which 
the approximation with a cubic parabola is no longer adequate. 

A continuous curve is obtained by smoothing the data. This, 
In turn, eliminates the need r for an evaluation at the frequency 
with which the data are available. The e^caluations, to be dis- 
cussed below, were made at a frequency of 1 Hz, which has proven 
to be a usable value. On the other hand, unnecessary computations 
are avoided — unnecessary because the state of flight has changed 
too little; on the other hand "fast" changes in the state of flight / 
are still covered with a sufficient number of points. /^^ 

Smoothing is done without regard to whether data which are 
related to one another also match. For example, no attention was 
paid to whether smoothed acceleration, once integrated, yields 
the smoothed velocity. It Is simply assumed' that the measured 
data are dispersed about the correct value. 

As an example of smoothing. Fig. 2-3 first shows measured 
acceleration, with the aircraft as a fixed reference. In the 
Z-direction as compared with the smoothed value. The evening 
effect of smoothing Is quite discernible, but so is the fact that 
pronounced obliteration has not yet occurred. The same applies 
to Fig. 2-4, in which smoothing of the angle of attack Is shown. 
The angle of attack correction described above is also shown. 

All measured data which are required for calculating thrust 
and weight were excluded from smoothing. In these cases, the 
calculation was first made and then the results smoothed. In the 
calculation of weight, it makes no difference what approach we 
use, since the consumption data are already relatively smooth. 
In the calculation of thrust, a still more precise study would be 
necessary, although here, too, the calculated values are already 
rather smooth, as Pig. 2-2 also shows. The reason for this approach 
lies in the assumed lower time consumption..' 

These extensive measures taken for data acquisition and the 
abundance of data themselves can only be handled by a program for 
an electronic computer, quite aside from the fact that the initial 
values are stored on magnetic tape. One FORTRAN program each was /45 
therefore written for the described preparation procedure and 
for the evaluation which followed. These programs are supported 
by three others which are not necessary for the actual calculations 
but do offer certain opportunities for control and further 
processing. The entire program [3] is designed for use on an 
IBM/360 computer. 

2.4. Calculation of Jet Interference 



The equations of motion in six degrees of freedom form the 
basis for calculating Jet interference from the flight test data. 



35 



since lift loss and jet-lnduced torque, only, are of primary 
interest for vertical takeoff and landing engineering, it is suf- 
ficient to make the calculations in the verticaL plane. It is 
also sufficient to calculate the aerodynamic components in the 
remaining three equations with simplified coefficients, since 
velocity is low in the transition region, so the effect of com- 
pressibility can be ignored. The nonsteady derivatives are also 
neglected, due to their normally small effect. Instantaneous 
total gross thrust was chosen as the reference quantity for jet- 
induced f^orces, so that interference parameters in a coordinate 
system fixed relative to the aircraft can be calculated from the 
following equations [1]. 



inter 



G 



tQt - „ — ■■ 



+■ (C^* sina - C^ coso) 



.% 



HL 



. F 



inter 



w 



. tot - ^2 " ^ * ®^"° 



rc^ • cosa + C„ slna) * ^|i2L 



. F 



/46 



M 



inter 



>^. *§(&■*<>.■) 



q . 1, 




The torque reference point is the aerodscnaijiic.. reference point 
corresponding to 22.5^ £„ . These equations form the content of 
a computer program which makes use of the measurement values 
prepared as described in the preceding section and the data com- 
piled in Tables 2.1, 2.2 and 2.3 for aircraft geometry, moments 
of inertia and aerodynamic coefficients. 



The results of these calculations are given as computer 
printouts in list form. In addition, a certain level of inter- 
pretation of the results can immediately be made by the computer. 

36 



For this purpose, certain classes were introduced for the two most 
important parameters of Jet Interference in the case of the Do 31, 
the angle x of nozzle rotation of the crulsln:g power plants and 
the ratio S^tw/^TW °^ ^^^''^ Po^^^ plant thrusts to cruising power 
plant thrusts, and dlmensionless Jet-induced lift or Jet-induced 
torque was expressed as a function of effective velocity ratio 
(V„/Vj)gff in the form of a print plot. 

Ten Do 31 E3 flights were available for evaluation, with a 
total of three vertical takeoffs, eight vertical landings and 
nine simulated landing approaches and other flight maneuvers, on 
whose results a report will be given in Section 3. 



37 



2.5. REFERENCES 

1. "The calculation of Jet interference for the Do 31 from flight 

tests," EA-31/2429. 

2. "Method for smoothing series of equidistant data," EA-31/24il9. 

3. "Program description for the program system L1DA31, DAUF31j 

DALP31, SAP31, PL0S31 for calculating jet interference for 
the Do 31 from flight tests," EA/P-0182/71. 



38 



F 


= 


57.0 


m2 


b 


= 


17.0 


m 


A 


= 


5.07 


— 


^ 


= 


^3.^3:5 


m 


Xme 


= 


: 1.60 


m 


^ME 


= 


-0.39 


m 


^MBC 
^MBC 


— 


0.30 
0.267 


m 

m 


^MBH 
^MBH 


= 


-1.70 
-0.267 


m 
m 



TABLE 2.1. Do 31 GEOMETRY AND MOMENTS OF INERTIA /M 

Wing area 

Span 

Aspect ratio 

Reference chord length 

Distance of cruising power plant inlet 
momentum from transverse plane 

from horizontal plane 

Distance of cruising power plant 

gross thrust, cold, from transverse plane 

from horizontal plane 

Distance of cruising power plant 

gross thrust, hot, from transverse plane 

from horizontal plane 

Distance of lift power plant inlet momentum 

from transverse plane 

Lift power plants 1 and 5 -^EEl 5 ^ 0.55 m 

Lift power plants 2 and 6 %E2,6 ^ -0.26 m 

Lift power plants 3 and 7 %E3,7 ~ -I.07 m 

Lift power plants 4 and 8 ^HE4 8 ~ -1.88 m 

from horizontal plane Zj^g = -2.06 m 

JDlstance of lift power plant gross thrust 

from transverse plane 

Lift power plants 1 and 5 x^-q-^ c = 0.25 m 

Lift power plants 2 and 6 Xhb2*6 = -0-56 m 

Lift power plants H and 8 %B3*7 = -1-37 ^ 

Lift power plants 4 and 8 ^34' 8 = -2.18 m 

from horizontal plane 

Distance of tail control nozzle 

from transverse plane 

from horizontal plane 
[Table 2.1 continued on following page.] 



39 



^HB 


= -0.78 m 


^HD 


= -12.569 m 


2hd 


= -1.655 m 



TABLE 2.1. (CONTINUED) 



/49 



Coordinates of Center of Gravity from the Following Equations 



Landing gear retracted; 



17250 < C < 18-550 



184 50 - G • 19670 



19670 < G < 24 500 



X = U . 10 
s 

z^ " 4 7 . lO' 



y = 20 . 10 

s 

z_ = 47 . lo' 



11 . 10 



34 . 10 



-6 



G - 0,157 IP 
G - 0,713 m 

G - 0,286 I? . 
G - 0,713 n 

G - 0,1085 r 
C - 0,457 jn I 



Landing ,gear extended: allowances for all weight ranges 



AXg « -3,4 . lO"^ , G + 0,13 HI 
AZg c -4,o . 10*^ . G * 0,17 P 



Moments of inertia from the following equations: 
Landing gear extended: 
Landing gear retracted: 



I = 0,1125 . G + 25 900 rJtps' 



I = 0,0734 . G + 26 130 n-Jecs^ 



40 



rdc 



TABLE 2.2. AERODYNAMIC COEFFICIENTS 
CF^ = FLAPS, Lg = LANDING GEAR) 

dc 



= i^ ^ ^ (hTtIfJ • (« - ^„ - Ac^ pji- Aa^ lJ 



A Ma 



o F£ ""o Lg 






St = (S^ + *=^Mo FJl + ^^^noLg) +(a-^" + ^ td?>Lg)x 



dc. 



( a - a^ - Aa^ |jj^ - A«^ Lg ) + dT^ 1 



/50 



where 



"o 




s: 


-2.13° 


^«o 


Fi 


= 


-3.52° 


^''o 


Lg 


= 


0.34° 


da 




= 


5.127 


dc., 









H—] = 0.36 
^da k 
So =0-042 

^^WFZ ~ 0.05B 



45^ 



45^ 



Ac, 



WLg = 0.073 
'^'^WHTW " 0.018 with lift pod flaps open \ 



K =-(0.290 + 0.861 



Kj : . 



-Mo 



(1.304 + 0.267 
0.058 



^'^MoFJt = 0.13 ■ 450 



Ac 



HoLg » -0.015 



M 



-0.50s 



dc, 

da 
dcu 
^tdT^^Lg - -0.125 

HIT " -^-^^ 



45^ 




[Table 2.2. continued on following page] 



^41 



TABLE 2.2 (CONTINUED) 

in the range of validity 

- (4° \ + 10°) < a < (13*' .+ 3° i^ ) 
45° - - 45O 

^^^ Ma < 0.3 

The values listed above were obtained from flight tests; 
Ca and Cy are trimmed values. The elevator component Is there+4 
fore also absent. The C]y[ values were subjected .to preparation 
and represent Cm values for dh = Oj ^^us the additional term for 
elevator torque. 



42 



/52 




o 

t^P^ 0-9530 




l' 



y'^ _r^V*S.* *'■ ~t^ 











If 



iT'''-:^ y" \-M ><^;^ p,^ ..^ ,. 

-i> ' / ^'/T ' ,^ far . .^isaa»^ 



ttaiQBa?i 




Pig. 2-1. Do 31 E1/E3 test aircraft in flight and 
on ground. 




^3 



■X=r 
4=r 



Cruising power plant 
cold thrust 

• rpm method 

+ nozzle pressure 
method 



scoo 
S tkpl 



2000 









1000 

16** 11* 16.02" t« 20 12 2t 2* 

t Ci»c] 



Cruising power plant 
hot thrust 

• rpm method 

X nozzle pressure 
method 




II to 2Z 2( 3« 

t tstcl 



Lift power plant thrust; 
(pod) 

o rpm method 

X nozzle pressure method 



/53 



• 000 

S tkpl 

7 000 
6000 
SOOO 
«0Q0 
J 000 



-■■ i ll V*- 



.w^»<*s.>rts,^<'. 



1« 1B SO 32 It 26 

t (Stc] 



Pig. 2-2. Comparison of gross thrusts for cruising power plants and 
thrust power plants determined by various methods of computation. 
Do 31 E3 trial 243, takeoff phase. 



M 



/54 






-i.t ■ 



u 



at 



OJ 



- a? 













IS . « * .isj 


•• • 

X * ••• * » * ^^v^ 




• 




^ l.r»<-^ 


32 2« 26 2« N 


k 30 33 


li 36 39 io/*'* 41. *A 




• 








\ 








a 

• Menwcrtc ]^ 
•— mtt 31 Punkttn gtglottet 





Pig. 2-3. Comparison of measured and smoothed acceleration In 
z-directlon (coordinates fixed relative to aircraft). Do 31 E3 
trial 243, takeoff phase. 

Key: a. Measured values 

b. Smoothed with 31 points 

Baf = acceleration in z-directlon of coordinate system 
fixed relative to aircraft 



VJl 



/55 



a 



D0 31-E3 VERSUCH 243 . STARTPHASE 



•la 



.It 




• Menwtrtc 

— mit 31 Punkten gigloHit'^ 

. m!t 31 Punhtd^ geglottet und ' 

hinttehtl. Drchcc3Chwindigl(Ctt 
gm die y-Achse korrigicrt 



Fig. 2-4. Comparison of measured, smoothed and cor- 
rected angles of attack. 

Key: a. Trial 243, takeoff phase 

b . Measured values 

c. Smoothed with 31 points 

d. Smoothed with 31 points and corrected with 
respect to angular velocity about the 
y-axis 



46 



3 . Evaluation of Represe'ntat:ive-Do ■■31 Tr'aris.'lt'ions ■ wl't^^ Respect /56 

to Jet'^Triduce'd' Forces' and Torques ,' .'a'n'd 'Comparison with Model 
Meas ur e'men't s 

Overview of Contents 

3.1. Introduction 

3.2. Notation 

3.3. Evaluation of Do 31 Transitions 

3.4. Comparison of Test Flight and Wind Tunnel Measurements 

Tables 



3.1. Listing of Do 31 flights evaluated with respect to Jet 
interference 

3.2. Jet interference evaluation. Do 31 E3, trial 2^7, takeoff 

Figures /57 

3.1. Jet-Induced normal force. Do 31 E3 trial 247- 

3.2. Jet-induced torque. Do 31 E3 trial 247. 

3.3« 'Time curves of a number of data for a portion of the 
landing phase, Do. 31 E3 trial 247- 

3.4. Jet-induced normal force. Do 31 E3, all flights listed In 
Table 3-1. 

3'5' Jet-induced torque. Do 31 E3. 

3.6. Do 31 E3 flights, mean Jet-induced normal force from 
Fig. 3.4. 

3.7. Jet-induced normal force. Do 31 E3 trial 247 with a^ 
correction . 

3.8. Jet-induced torque. Do 31 E3 trial 247 with a^ and cjvjq 
correction . 

3.9. Do 31 E3 trial 247: Jet-induced normal force coefficient 
versus angle of attack. 

3.10. Do 31 : jet-induced normal forces during vertical 
landing. Comparison between wind tunnel and flight test. 



47 



3.11. Do 31: jet-induced pitch torque during vertical landing. 
Comparison between wind tunnel and flight test. 

3.12. Do 31: jet-induced normal force due to ground effect /58 
during four vertical landings. 

3.13. Do 31: Jet-induced pitch torque due to ground effect 
during four vertical landings. 



48 



3.1. Introduction /59. 

This Is not the first time that VTOL flights by the Do 31 
have been studied with regard to jet interference. Back toward 
the end of Do 31 flight testing In 1968, an attempt was made to 
determine the Jetr-lnduced forces and torques from measurement data 
stored on magnetic tape. The data for interference evaluation 
were at that time more or less byproducts of the actual test 
assignments, for which reason the required accuracy of certain 
measured quantities, particularly thrusts, was inadequate. The _ 
results of Jet interference evaluation were therefore likewise 
unsatisfactory. The dispersion of the results was sometimes so 
great that no conclusions could be drawn. 

A method for more accurately determining thrust was developed 
by Dornler for the study of Do 31 VTOL landing techniques carried 
out in the years 196gf/70 under a NASA contract. 

Reprocessing of the aerodynamio coefficients on the basis of 
conventional flights by the Do 31 E3 was accomplished as part of 
the Do 31 simulation program at NASA. 

A considerable improvement in starting conditions for a re- 
newed jet interference evaluation was thereby obtained. Addi- 
tional measures for improving accuracy and for smoothing the data 
were carried out as part of these studies and are explained in 
Section 2. 

3.2. Notation /60 

B Wing span 

Og Coefficient of normal forces (positive: downward) 

CM Coefficient of pitch torque (positive: tail-heavy) 

F Wing area 

H Distance between landing gear and ground 

a Mean aerodynamic chord length 

M Pitch torque 

q Plight dynamic pressure 



loo 



Stt Thrust of Do 31 lift power plants 

Sjyj Thrust of Do 31 cruising power plants 

S Gross thrust of power plants 

v Aircraft speed 

00 

V. Initial velocity of nozzle jet 



^9 



^eff 



iv. P 



Effective velocity ratio 



X Tangential force (coordinates fixed relative to 
aircraft) positive forward 

Z Normal force (coordinates fixed relative to 

aircraft) positive downward 

a Angle of attack 

T Angle of cruising power plant noszle rotation; 

T = when Jet is directed rearward 

rij^ Angle of special flaps 

6 Aircraft angle of pitch 

3.3. Evaluation of Do 31 Transitions /6I 

This evaluation is limited to so-called NASA flights per- 
formed in 1970, since usable magnetic tapes of measured data are 
still available only for these flights and, moreover, the method 
of thrust determination is usable only for these flights, as 
already mentioned. The test program at that time was oriented 
almost exclusively toward the study of landing methods for verti- 
cal landings, so the parameters which are Important for Jet 
interference processes cover only a relatively narrow range. 
Table 3.1 shows a compilation of the evaluated Do 31 E3 flights. 
Including time intervals and flight maneuvers. 

The measured data are treated by the method described in 
Section 2. The results are available for each flight in the form 
of a list which contains the most important flight data and the 
jet-induced normal forces ZI = AZ/Sq, tangential force 

XI = AX/Sq and pitch torque MI = AR/SqZ^j referred to instantaneous 
gross thrust Sq and mean aerodynamic chord length S,y , at inter- 
vals of 1 sec. In addition, AZ/Sq and AM/SQ*Jly are plotted over 
effective velocity ratio 




in a print plot. The angle t of cruising power plant nozzle 
rotation and the ratio Sj{/S]y[ of lift and cruising power plant 
thrusts are divided into different classes here. Altitudes of 
H/b < 0.8 are eliminated in the print plot, since the ground ef- 
fect is treated separately. 



50 



Table 3.2 shows the vertical takeoff and vertical landing in 
trial 247 as an example. Pigs. 3.1 and 3.2 show jet-induced 
normal force and pitch torque in a print plot. Pig. 3-3 shows the 
time curves of the most Important parameters of the state of 
flight during a portion of the landing phase to touchdown. 

The takeoff phase to lift power plant shutdown lasts only _, /62 
about 20 sec. After vertical liftoff, the flight path is rather 
flat, so the aircraft is not entirely outside the ground effect 
(H/b > 0.8) until 13 sec have elapsed. This is the reason for the 
small number of measurement points for the takeoff phase in 
Figs. 3.1 and 3.2. At H/b < 0.05, the aircraft is standing on the 
ground. A conspicuous feature in the list is that a dynamic 
pressure of about 4 kp/m^, corresponding to a Veff = 0.03, is 
indicated both prior to takeoff and after landing. 

The average behavior of jet-induced normal force in Fig. 3.1 
corresponds qualitatively to the wind tunnel results. The level 
in flight measurements is higher, however. A conspicuous feature 
is the constant behavior of torque in Fig. 3-2. Otherwise, the 
dispersion in measured data is relatively small compared to 
earlier evaluations. Individual stray values can be ascribed to 
highly unsteady phases of flight (increase in thrust, rotation of 
nozzles), as one can see from the list. 

The print plots for all evaluated flights are collected in 
Figs. 3.4 and 3.5- Unfortunately, the concentration of measurement 
points about a mean value which was hoped for under equivalent 
conditions did not occur; rather, the range of dispersion was 
enlarged considerably. In order to obtain a qualitative Impres- 
sion of the effect of the principal parameters t and 3^/3^, the 
means are taken from Fig. 3.4 and plotted as curves in Fig. 3.6. 
Jet-induced normal force is always smaller for throttled 
cruising power plants; this is reasonable, since the cruising 
power plant jets exhausting under the inboard wing cause con- 
siderably more Interference than the lift power plants mounted on 
the wing tips. The predominant effect of the cruising power 
plants on AZ/Sq can also be seen from the pronounced dependence 
upon angle of rotation. 

Analysis of the lists of VTOL landings for all evaluated 
flights yields the following information: 

a) After touchdown on the ground (H/B < 0.05), dynamic /63 
pressure is still q^ = 4 to 10 kp/m^, corresponding to a Vg-f-j- = 
= 0.03 to 0.05; see table below. 

Since no statements are made in the flight records con- 
cerning wind velocities, it is assumed that a shift in the zero 
point Is involved and that the actual value is V^ff = 0. 



51 



b)' At H/B = 0,8, Vgff Is approximately the same as at 
H/B = 0.05. The considerations discussed under item a) thus 
apply. At the same time, Jet-Induced normal force fluctuates 
over 0.036 < AZ/Sq < O.097 from one flight to another. Since 
the value of AZ/Sq would have to be the-same for all flights under 
the-'.glven identical boundary conditions, a. shift In zero points is 
assumed to have occurred for one or more measured values. An 
error on this order of magnitude is eliminated in the case of 
weight determination. An error in normal acceleration Is elimi^ 
nated for the reasons to be presented under Item c). A shift In 
the level of thrust is supported by the fact, presentedrln 
Section 2, that appreciable differences in magnitude exist between 
cruising power plant thrust as determined by the rpm method and 
by the nozzle pressure method and/or between lift power plant thrust 
as determined by the rpm method and by the fuel flow method. 



VTOL ■landings 



Trial 


H/B = 


,05 




H/B 


= 0,8 


No. 


^eff 




^eff 




AZ/S^ 


231 


0,047 




0,033 




0,035 


240 


0,031 




0,027 




0,036 


243 


o,050 




0,054 




0,097 


247 


0,042 




0,037 




0,072 



It follows from the wind tunnel measurements that a thrust 
loss of AZ/Sq = 0.036 must be expected in hover outside the 
ground effect. 

c) For the state of flight at the beginning of the landing /64 
phase, prior to starting the lift power plants, ,t = 10°, riK ~ ^5°, 
landing gear extended, the aerodynamic coefficients were deter- 
mined from earlier Do 31 El flights under the assumption, as 
mentioned earlier, that no jet interference occurs. In the pre- 
sent evaluation, five different flights yield a Jet-induced 
normal force of AZ, ^ 1200 to l400 kp at q = 320 to 350 kp/m2 
dynamic pressure for the specified phase of flight;.; Similar 
conclusions apply to Jet-induced pitch torque. Since a deviation 
which is approximately constant for several flights is involved, 
a correction can. be used for the aerodynamic coefficients. Since 
a dependence upon a cannot be detected (to be sure, the range of 
stagnation pressures and thus the range of a are very narrow), 
a shift in the zero-point direction of lift and zero-point torque 
is suspected. 



52 



In contrast to the Do 31 E3, the flaps of the lift power 
plant pod and the deflection cascade on the lift power plant In- 
let were not extendible in the El, so the aerodynamic coefficient^ 
determined with the El do not include these, effects. In particu- 
lar, a shift in cmo Is Justified for this reason. 

d) Highly nonsteady phases of flight, produced during 
changes ±n thrust or during nozzle rotation, for example, produced 
stray values in spite of smoothing of the data and should be 
omitted from evaluation. 

Trial 24? was reanalyzed, taking items a) through d) into 
consideration. In accordance with Item c), residual force Is 
AZ = 1250 kp for q = 350 kp/m2 . This corresponds to a normal force 
coefficient of AC2; = -0.0626 which is neutralized as a shift in 
the zero-point lift direction by Aao = -0.75°. Accordingly, a 
shift by AC]y[o = -O.O67 is Introduced. Thus the Interference 
computation for flight 2^7 yields freedom from Interference on 
the basis of the assumptions in the conventional landing state of 
flight. Evaluation of the vertical landing with modified co- 
efficients is shown in Fig. 3,7 and 3.8. As was to be expected, 
the effects of the change were in the form of an Increase in nor- /65 
mal force and in torque with increasing dynamic pressure. 

On the basis of a dispersion In the AZ/Sq values observed, in 
particular, at higher values of Veff , it was suspected that jet 
interference is a function of angle of attack. For this reason, 
the Jet-induced normal force coefficient ACg is plotted in 
Fig. 3.9 against angle of attack for various phases of flight In 
flight 247. The plot indicates a dependence upon a, A change in 
the increase in lift has already been observed in wind tunnel 
measurements, for which reason the wind tunnel results are given 
for a = 0*^. The' measured data plotted in Fig. 3.9 are not suitable 
for correcting the flight measurements to a = 0°, since dispersion 
is too great and, moreover, a portion of the dependence upon a 
may be credited to a correction in the conventional aerodynamic 
coefficients. 

Regarding the evaluation of Jet interference in the flight 
tests, it can be stated, In closing, that usable values for the" 
magnitude of Jet-induced normal force and of pitch torque were 
obtained both for the transition outside the ground effect and 
for vertical landings. The values associated with hover outside 
the ground effect (H/B > 0.8) are the least reliable. There Is 
apparently an error in the method for determining thrust. At 
the higher aircraft speeds, toward the end of the transition. 
Inaccuracies In the interference-free aerodynamic coefficients used 
as input become highly noticeable* A more precise evaluation of 
Jet interference for future flight tests is only possible if 



53 



a) the determination of thrust is further Improved, 

b) the Interference-free aerodynamic coefficients are 
determined as precisely as possible from flights with the 
test aircraft, 

c) special flight maneuvers are flown r'f or Jet inter- 
ference studies, 

d) wind velocity and direction are determined precisely 
during the takeoff and landing processes. 

3.4. Comparison of Tesf Flight and Wind' Tunnel Measurements /66 

Due to the difference in magnitude of AZ/Sq in hover outside 
the ground effect mentioned under item b) In Section 3.3> this 
flight state was selected as a reference point for comparison. 

In Pigs. 3.10 and 3.11, the normal force induced In transi- 
tion and pitch torque are plotted over Vgff . The uncorrected 
values and those corrected:'for a^ and cjvio are higher for the 
flight test values than for the wind tunnel. The uncorrected 
torque curve was not drawn In, since there is no dependence upon 
Vgff. The corrected torque curve, on the other hand, is not far 
from the wind tunnel curve. From this example we see how marked- 
ly a relatively small change in the aerodynamic coefficients 
affects the determination of Jet interference, particularly at 
high aircraft speeds. 

For comparison, the maximum available control torque, con- 
sisting of Jet control and aerodynamic elevator control, is 
plotted in the lower portion of Pig. 3.11. 

The effect of ground distance upon jet-induced normal force 
and pitch torque is shown in Figs. 3.12 and 3.13. Results from 
four vertical landings are plotted. The state associated with 
hover outside the ground effect (H/B > 0.8) has been chosen as a 
reference point. 

The reason for the great band width of the; plotted wind 
tunnel measurements Is that the angle of pitch was varied over 
-10° < e < 10°. A finer breakdown of the 6 effect is not 
profitable, since the unstable flow field close to the ground 
reacts sensitively to changes in 6, and nonreproducible measure- 
ment results exist in some cases. 

The figures provide an impression of the disturbances in 
normal force and In pitch torque occurring during vertical landings 
and exhibit satisfactory agreement with the wind tunnel 
measurements . 



54 



TABLE 3.1. LISTING OF Do 31 E3 FLIGHTS EVALUATED WITH RESPECT 

TO JET INTERFERENCE 



Trial No. - 
231 


16^ 


t 
2 


Time 
From 

54.02' 


-interval 
16^^ 5- 


to 

57.02" 


237 


is'^ 


1 
24 


38.02" 


le'^ 


r 

26 


51.02" 




16*^ 


1 
30 


51.02" 


ig'^ 


1 
22 


10.02" 


238 


lo'^ 


1 
2 


23.02" 


10^ 


• 

3 


54.02' 




10*^ 


t 
6 


3S.02" 


10^ 


1 
7 


53.02" 


239 


12^ 


1 
8 


30.02" 


12*^ 


10' 


31.02" 




12^ 


14* 


39.02" 


12^ 


17* 


0.02" 




12^ 


21' 


II 
1.02 


12'^ 


23' 


37.02" 


240 


14^ 


49' 


15.02" 


14*^ 


52' 


15.02 


243 


16^ 


is' 


13.02" 


16^ 


19' 


0.02" 




is'^ 


18* 


19.02" 


.6*^ 


19' 


II 

57.02 


■ ■ ■ ' 


16^ 


27' 


2.22" 


16^ 


28* 


57.22" 




16^^ 


36* 


45.02" 


16^ 


38 


■I 
30.02 


244 


11^ 


19' 


21.02" 


11^' 


21' 


H 

31.02 




11^ 


25* 


50.02" 


11^ 


27' 


53.02" 


246 B 


lo'^ 


51' 


22.02" 


10^ 


53 


10.02" 


247 


14^ 


18* 


50.02" 


14^^ 


19 


n 

20.02 




14^ 


32' 


2.02" 


14^ 


35 


0.02 


24B 


16^ 


• 
4 


15.02" 


16*^ 


4 


41.02" 




16^^ 


10' 


0.02" 


16^ 


11 


1 n 

13.02 




16^ 


16* 


0.02" 


le'^ 


le 


1 « 
10.86 



Flight maneuver 

Vertical landing 
Simulated landings 

Simulated landings 
Simulated landings 

Vertical landing 
Vertical landing 
Vertical takeoff 

Climb without lift 
power plants 

Vertical landing 

Simulated landing 

Vertical landing 

Vertical landing with 
forward speed 

Vertical takeoff 
Vertical landing 

Vertical takeoff 

Simulated landing 
Vertical landing 



Three vertical takeoffs 
Eight vertical landings 
Nine simulated landings 



55 






TABLE 3.2a. JET INTERFERENCE EVALUATION, Do 31 E3, TRIAL 24?, TAKEOFF 



/68 















*KL1, 


KH3* 










Feb. 


4, 1972 




, p: 


O 




(0 




rt 


CB 






^ 

•^ 










Landing 
gear 


fn-H 




bO 
•H 


3 


• in 


•g, 


4J 
<1> 


XI 


3 


*4H 












(U 


.c 


rH 


x: 


'^ 


cfl 


X 


O 


1— 1 


1— 1 


kH 






s 


H 


QCU 


< 


f- 


DC 


H 


w 


> 


ts) 


X 


E 




I'O.CZ 


21024. 


2)**9. 


3.44 


9. a 




0.05 


74.0 


1.495 


0.026 


0. 0521 


-0.0440 


0.07J9 


.Extended 




11.02 


2101T. 


2)SE<.. 


i.i> 


4,1 


1*5 


0.06 


73.1 


1.4T6 


0.034 


0.0447 


-0.0?56 


0.0750 


i 




;2.o2 


21011. 


21J*.4. 


T.41 


t.2 


2* ^ 


0.10 


•65.V 


1.497 


0. C3ff 


0.0457 


-0.0'4i 


0.0)i« 




;).a2 


210Ci. 


22«1C. 


14.34 


2.6 


3*2 


0.!5 


■ !n.6 


l.'^^l 


0.05) 


0.0477 


0.0119 


0.094O 




:«.o2 


204 <)g. 


226)4. 


26.11 


1.3 


i» 9 


0.19 


40,2 


1.500 


0.0^! 


0.1451 


-o.ojBa 


0.0951 


— 




•S.Ol 


2a9<>2. 


22Sfl». 


34. *2 


1.7 


5»T 


0.22 


36.0 


1.472 


0.0S5 


0.0546 


-0.0)04 


0.OS90 


O j^-4' .w*«^ i*i ^ n 




:4.o? 


20<ie9. 


?2tlC. 


4».*7 


4.1 


^» 3 


0.22 


J*. 9 


T.4A7 


0.065 


O,0!95 


-0.1130 


0.0697 


_ Retract e 




9T.02 


iMT"}, 


225TO. 


55.9a 


4.2 


^•fl 


0.22 


34,3 


1.467 


0.105 


0.04 TO 


-0.0)70 


0,56*0 








!«.C2 


2C^T2. 


126*3. 


66.26 


3.3 


7*1 


0.24 


3).» 


1.460 


0.U3 


0.0464 


-0. 0107 


0.0i79 








i'>,OZ 


2':9e(>. 


2241)2. 


T6.e3 


3.3 


5* 3 


0.29 


3).0 


1.46! 


0.124 


0.Q446 


-o,04Z4 


0.'3M9 








0.02 


20"»»'J. 


2<924. 


90.77 


3.0 


9 •fr 


0.)fl 


23 .4 


1.464 


0.134 


0. 04 64 


-i.csoo 


0.0646 








I. 01 


20<);3. 


2230!. 


ics.-s^ 


2.1 


5a A 


O.tl 


27.3 


1.462 


0.144 


0.O42O 


-0.0445 


0.0*37 








2.02 


20'>*T. 


221 ^B. 


120.66 


O.T 


9*4 


0,-64 


25,4 


1.461 


0.J55 


0.0)93 


-0.05^5 


0.3743 








1.C2 


2C«*C. 


2l°«l. 


116.02 


0.4 


9*1 


C.B4 


22.2 


1.461 


0.1*7 


O.04OO 


-0. n«77 


0,0'<:9 








4.CZ 


20')}4. 


21607. 


149. T« 


0,7 


5.1 


l.U 


i9.e 


1.445 


0,174 


O-O*")!) 


-0.0T18 


0.0554 








3.02 


2092 T. 


21317. 


161.33 


t.O 


5« 3 


I.3» 


14.9 


1.467 


0.115 


0,0446 


-0.07»» 


0.0592 








*.02 


20'>;i. 


212ec. 


173. 4T 


1.1 


1* * 


1.4B 


11.9 


1.4)0 


0,192 


0.0)27 


-0.0110 


0.0696 








T.02 


20<)l*. 


21697. 


191,90 


0.2 


5*4 


1.69 


n.o 


1.3iJ 


0.200 


0.0116 


-O.OI'O 


0.0666 








8.C2 


2C<iCT. 


22063. 


216.3$ 


-0.4 


5* 3 


1.06 


11.1 


1.315 


0.210 


0.0009 


-0.0-'19 


0.0641 








4.02 


20<)(ro. 


22263. 


24V, 67 


• 9.6 


^« 2 


2.26 


11.1 


1.313 


0.221 


0.0215 


-O.DS*6 


0.06 44 








10.02 


20SO*. 


22417. 


267,25 


•1.1 


?»0 


2.5'? 


it.o 


1.321 


0,232 


0. 041 5 


-0.0664 


0.045) 








It. 02 


20diT. 


21747. 


2S5.SJ 


-t.) 


4« 4 


2.95 


10.9 


1.235 


0.24T 


0.0749 


-0.07*t 


0.0564 








12.02 


2oesi. 


l^T")"), 


32). 41 


-1.0 


4* 8 


3.31 


11. 


1.025 


0.271 


0.0S16 


-0.0541 


0.344O 








1J.02 


■ 2Ct75. 


ia»f4. 


345.42 


-0.6 


5*0 


3.69 


10.9 


0.906 


0.21*9 


0.0»7} 


-O.CflT 


0.0076 








14.02 


JOtTO. 


17'>63. 


364.92 


0.2 


T* 3 


4.02 


10.9 


0.S4H 


t.302 


n.l2Ti 


-0.1 (•04 


-0.052> 








19.02 


2cs&b. 


1S4^4. 


191.4} 


1,0 


>*o 


4.1) 


10.9 


0.553 


0.533 


3, 1270 


-0.1755 


-0.055) 








16.02 


2oat2. 


12*7*. 


JSS.51 


2.0 


6« 


4.60 


10.9 


0.155 


0.375 


0.0243 


-0,1'7' 


-0.0092 








17.02 


2O«60. 


USfi2. 


416,13 


2.7 


A« 4 


4.ao 


10.9 


0.O09 


0.397 


-0.0774 


-0.0O27 


0.0 06) 








1).02 


2CSfS. 


lia<)3. 


4)3.S6 


2.9 


ft* ' 


4.9a 


10.9 


0.010 


0.405 


-0.0953 


-0,1157 


0.0251 








If. 02 


20a5». 


11937. 


447.20 


2.9 


7* 


3.20 


lo.s 


o.ooi 


0.411 


-0.1023 


-0.t)6« 


0.0219 








20.02 


20a$4. 


11454, 


462. JS 


1.2 


T»T 


3.43 


lO.S 


0.0 


0.291 


-0.OT97 


-o.n* 


0.0026 


^ r 



TABLE 3.2b. LANDING 



/69 



''KL1,KH3* 



Feb. 4, 1972 



ui 



a o 




4-1 


1 


rt 


nJ 
















Landing 
gear 




tiO 
•H 


3 
U 




Xi 


4-1 


XI 


3 


<4H 










0) 


Xi 


.-1 


X 


•^ 


05 


K 


lU 


t—t 


h-t 


^~i| 




s 


fr- 


; Q&. 


< 


H 


ac 


H 


en 


> 


M 


X 


S 




























Extended 


14 it 2.02 


1*157. 


4**e. 


3tl.l4 


5,2 


2.} 


26.96 


10.5 


0.0 


0.144 


-0.1665 


-3.1 605 


-0.2171 




H 32 1.02 


I'll 55. 


b674. 


159. OB 


5.1 


Z.J 


26.94 


10.6 


0.0 


0.143 


-0.1440 


-0.17)5 


-0.225* 




14 j; *.02 


1^154. 


till. 


159.15 


5.3 


2.1 


24.96 


10.4 


0.0 


0.341 


-0,1246 


-0.1*4" 


-0.2300 




14 12 ;.02 


ms3. 


4M7, 


15^,10 


4.8 


2,3 


26,99 


10,5 


0,0 


0.3*1 


-0.1904 


-0.1769 


-0.2168 




1* 32 4.e2 


i';ii2. 


6595, 


153,80 


4,* 


2.0 


25.71 


10.6 


0,0 


0,1*1 


-0.2029 


-0.18*1 


-0.2043 




14 12 T.02 


19151. 


6609, 


352,91 


4,* 


1. K 


26.28 


10,6 


0,0 


0.14? 


-0.2021 


-0.1952 


-0.2(152 




14 12 «.02 


19150. 


6599. 


350.59 


4.B 


1.6 


26.22 


10.5 


0.0 


0.3*1 


-0.2137 


-0.10)7 


-0.2097 




14 K «.02 


191*9. 


44C3. 


350.61 


5.1 


1. T 


26.44 


10,6 


0.0 


0.34' 


-0-2141 


-0.'.f47 


-0.209T 




14 12 to.02 


19149. 


6605, 


550. Rl 


5,2 


2.0 


26.49 


10.6 


0.0 


0.)4» 


-0,202* 


-O.f-H 


-0.2072 




14 12 11.02 


1S14T. 


6602. 


150.16 


5.1 


2.3 


25.35 


1C.6 


0.0 


0.341 


-0.1961 


-0. 1919 


-0.1987 




14 1^ 12.02 


19145. 


64 19. 


150.44 


4.9 


2.4 


?4,20 


10,6 


0.0 


0.1*0 


-O.t"*? 


-".2003 


-0.1O50 




14 32 11.02 


19145. 


66^1. 


,l*lt.56 


4.4 


2,4 


2fi,08 


10.5 


n.o 


0. J*0 


-C. 2*60 


-O.IC84 


-0.1999 




14 12 14.02 


19144. 


66IC. 


3*t.H 


4.T 


2.4 


25.94 


10.5 


0.0 


0.139 


-0.2t29 


-0.1915 


-0.1970 




14 12 15.02 


191*1. 


6622. 


J44.2T 


5.2 


2.6 


25.74 


10.6 


0.0 


0,177 


-0.2081 


-0.196* 


-0.1078 




14 12 1«.C2 


191-2. 


6r>16. 


3*1.34 


5.9 


1.1 


25.5* 


IC.6 


O.OOl 


0.*57 


-0.1798 


-0.1519 


-0.1955 




1* 12 17.02 


19141. 


6565. 


3*2.29 


5. ( 


3.1 


2'.1* 


10.5 


O.OOT 


0.*"* 


-0.2**0 


-0.1290 


-0.1892 




14 12 1S.02 


191*0. 


6592. 


,3*5.25 


S.4 


1.1 


25.18 


10.6 


0.007 


0.*«6 


-fl.-.l28 


-O.l'ifll 


-o.pol 




14 12 19.02 


1913S. 


6096, 


13*5.74 


4.9 


3.1 


24.<»6 


to. 5 


O.lOl 


0.475 


-0.2751 


-0,104* 


-0.1^94 




14 32 20,02 


19134, 


7496. 


3*7.41 


4.6 


3.4 


2*.>il 


10.5 


0.261 


0.457 


-0.1560 


-o.o-'ti 


-0.(4C« 




14 12 21.02 


19134. 


8*79. 


148.82 


4.1 


1.) 


24.75 


10,6 


0.415 


0,413 


-0.O917 


-O.P53A 


-0.1297 




14 32 22.02 


19131. 


10172. 


3*6.51 


3.0 ' 


3.3 


24.72 


10. ^ 


0.825 


0.392 


-0.0557 


-B.O'H* 


-0.0774 




14 12 2J.C2 


19127, 


11879. 


1*6,69 


1.9 ■ 


2.9 


24.69 


10.6 


1.134 


0.36 2 


-0.0123 


-0.0461 


-0.0**7 




14 !2 24.02 


1S12*. 


12508. 


35C.44 


1.1 


1.9 


24. 5« 


10.6 


1.240 


0.15* 


0.0104 


-0.0733 


-0-C*03 




14 12 2i.02 


1«120. 


12713. 


153.59 


1.5 


1.7 


2*. 43 


lO.S 


1.279 


0.'5* 


0,0394 


-O.0»t4 


-0.0*22 




14 3.' 26. c; 


1914(1, 


1275(. 


353,58 


1.7 


2.0 


24.32 


10.6 


1.2fl3 


0,353 


0.0575 


-0.0791 


- r. C406 




14 32 2r.02 


1911;. 


12792. 


310.67 


1.5 


2.1 


24.2* 


10.4 


1.2S8 


0.351 


0.0507 


-0.091? 


-0.0324 




14 3^ 2e.C2 


19ioa, 


12736. 


1-7,73 


1.1 


2.0 


24.13 


10.5 


1.2'>9 


0.350 


0.1448 


-0.0002 


-0,0279 




1* 12 2'».02 


19104. 


12767. 


3*9.91 


1.2 


1.8 


34.01 


10.2 


1.2A9 


0.351 


0.0S29 


-0.0531 


-0.0159 




14 32 30.02 


19100, 


12757. 


350,51 


1.3 


1.9 


23.97 


9.7 


1.2fll 


0.352 


l^.oii* 


-0. 0572 


-0.0*05 




14 32 )1.02 


19C<t. 


11073. 


1*9.^4 


9.9 


2.0 


2^.90 


l*.T 


1.291 


0.1*7 


o,n:>r9 


-0.0705 


-0.03)1 




14 12 12.02 


1^092. 


138*9. 


3)4.14 


O.l 


1.9 


2>,54 


27,9 


1.112 


0.339 


O.OOJ!^ 


-0,0«.7J 


-0,OT59 




14 32 33.02 


19008. 


1*426. 


355.05 


-0.2 


1.5 


2i.9S 


19.2 


1.108 


0.331 


0,Q»H 


-0.0607 


0.01*8 




14 32 34,02 


19064. 


l*47f. 


3)2-17 


-0.9 


1.2 


23.59 


4T.9 


i.ns 


0.129 


D.0295 


-0.0707 


0.0284 




14 32 3S.C2 


1^090. 


l*l»74. 


344.56 


-2.0 


O.T 


22. 69 


58.8 


1.324 


0.321 


-0.0173 


-0. 0759 


0.0*2* 




14 32 3*. 02 


1^074, 


1*034. 


113.12 


-2.4 


o.;" 


23.19 


54.0 


1.317 


0.317 


-n,0102 


-0.0795 


0.0459 




14 12 1/.02 


190?i. 


1*928. 


324. TT 


-2.4 


-0.2 


21.53 


67.2 


1.314 


0.3)4 


0.0257 


-0.0719 


0.0**0 




14 32 38.02 


1906O. 


1493S. 


324.56 


-2.1 


-O.S 


23.66 


4cS.9 


1.H7 


0.311 


0.08 79 


-0.0555 


0.0*97 




14 32 39.02 


190AS, 


i*9c:. 


315.80 


-l.J 


-0.4 


21.55 


66.; 


1.116 


0.309 


0.124* 


-0,0711 


0.05*1 




14 32 40. C2 


19041. 


14933, 


309.98 


-l.l 


-0.7 


ri,*4 


64.9 


1.309 


0. 304 


0,0566 


-0,077( 


0.0508 




14 32 41.02 


19CS7. 


15022. 


912.10 


-1.7 


-0.9 


2J.41 


47. 2 


1.30* 


P. 306 


0.02-'3 


-O.OT?. 


0-05*4 




14 32 42.02 


1«051. 


1**71, 


307.30 


-0.0 


-0,4 


23.19 


65.9 


1.320 


0,'>07 


CI 704 


-0.0'" 


0,0389 




I* 32 41.02 


190*9. 


117*7. 


299.29 


2.3 


1.4 


2».34 


61.0 


1 .160 


0.113 


0.3718 


-0. 1000 


-0.0228 




14 12 44.02 


1<;0*5. 


13fl9?. 


2';2.*C 


-0.1 


1.0 


21.29 


61.9 


1.14B 


0.3Q'! 


0.1050 


-0.0?S1 


-0.5085 




14 12 45.02 


190-2. 


14696. 


2^6.65 


-1,1 


-O.T 


23,17 


44,5 


1.106 


0.2O6 


0. O'lO 


-0.06 ■■8 


o.0'l3 




14 32 46.02 


l9S38. 


1*901. 


2ei.i9 


-0.6 


-0.8 


22.90 


67.2 


1 .296 


n.292 


n.o'"* 


-0. 0**6 


0.04 05 




14 tl 47.02 


1903*. 


1*6(19. 


274.38 


-0.5 


-0.6 


72.60 


66.8 


1.24B 


0.290 


0.0511 


-0.07** 


0.0570 




14 a 4S,02 


19030. 


1*630. 


268.22 


-l.O 


-0.7 


22.42 


66.7 


1.296 


0.297 


0.0*2) 


-0.0722 


C. 0581 




14 12 49.02 


19026. 


14631. 


263. B6 


-0.9 


-l.l 


22.30 


66. B 


1.790 


0.2'<5 


0.0812 


-0.05*3 . 


0.0406 




14 12 30. C2 


19022. 


1*621. 


257.)* 


0.4 


-l.l 


22.07 


66.9 


1.786 


0.2«2 


0.1049 


-0.07*7 


0.0*71 




14 32 St. 02 


ifCH. 


i*593. 


255.18 


0.9 


-0.4 


21. *6 


64,8 


l.J«5 


0.2SI 


0,0''«4 


-0.07 71 


0.0505 




14 32 »2.02 


19014. 


145ei. 


2;e.66 


0.7 


0.1 


'0.85 


66.8 


1.261 


0.281 


0.09«* 


-O.0'»l 


0.0524 




14 12 S3. 02 


190lC. 


1*469, 


2 52.42 


0.3 


0.6 


20.79 


66.8 


V.269 


0.280 


0,0494 


-0.0711 


0, 0403 




14 32 S4.02 


19007. 


1*662. 


,247.67 


-1.4 


-0.3 


21.14 


66.2 


l.'OT 


0.27«. 


-0.0015 


-O.O'OJ 


O-O'lS 




14 12 15. C2 


1^002. 


16221. 


2*9.45 


-3.9 


-2.7 


21.45 


66.2 


1.518 


0.261 


-0.0229 


-0,0515 


0.0846 




14 32 fb.02 


iSfse. 


1S63S. 


1249.65 

■J^^ 


-5.2 


-5.1 


21.18 


73,5 


1.824 


0.246 


0.0251) 


-0.0595 


0.0898 





Ul 

: oo 



TABLE 3.2c. LANDING (CONTINUED) 



/70 



*KL1,KH3* 



Feb. 4, 1972 



c o 



+-> 


*J 


x; 


<n 


bO 


3 


■H 


fH 


(D 


^ 


s 


H 



- 


rt 


cd 






S 




• trt 


j:i 


+J 






W 


t*H 


^^ 


PL. 


<u 


J3 


3 


•^ 


tH 


.—1 


x: 


-^ 


nj 


X 


(U 


QfL. 


< 


H 


X 


E- 


w 


> 



M 



X 



(30 

■H 
■3 

c 






Extended 



14 K ST. SI 


1S<)92. 


20298. 


Z48.ZT 


-5.Z 


-6.3 


Zl.Zl 


90.0 


1.751 


0.235 


0.0803 


-0.0683 


0.083) 


14 iZ 58. OJ 


IS9ST. 


20996. 


246.89 


-4.9 


-6.6 


Zl.OT 


102.0 


1.545 


0.7 30 


0.1151' 


-0,0441 


0.07)1 


1* 31 59.01 


IB^St. 


21086. 


239.68 


-4.7 


-6.4 


20.88 


104.3 


1.493 


0.226 


0.1)11 


-0.0179 


0,0718 


14 1} Q.Q2 


letTa. 


21038. 


Z29.5Z 


-4.T 


-6.2 


Z9.61 


103.6 


1.^01 


0.222 


i).1282 


-0.05*0 


0,S7)S 


1« 3J 1.02 


lesTC. 


21007, 


21B.1T 


.-4.7 


-t.2 


20. 3t 


101.4 


1.502 


0.216 


0. 1241 


-0,0521 


0.0763 


I* a Z.02 


H')t.4. 


20974, 


206.76 


-4.8 


-6.5 


20.03 


103. J 


1.417 


0.2it 


0.1269 


-0.04 72 


0.0772 


14 )J 3.CZ 


18959. 


20897, 


198.63 


-5.1 


-7.1 


19.78 


104.4 


3,499 


0.207 


O.'IST 


-C. 0479 


O.O'C) 


14 33 4.02 


18953. 


207CC. 


192.86 


-5.3 


-7.9 


19.;> 


109.3 


1.503 


0,Z05 


0.1349 


-0.0470 


0.079<t 


14 3J 5.01 


Hi)*T. 


20570. 


187.29 


-4,7 


-8.3 


19.25 


110.0 


1.501 


0.202 


0.1509 


-0.0429 


0,0764 


14 a b.CZ 


18942. 


203 75. 


181.87 


-1,9 


-7.9 


19.83 


109.3 


1.473 


0.200 


fl.l54l 


-0.044 4 


0,0T1T 


14 13 T.OZ 


I89 3t. 


19795. 


176.29 


-J. 3 


-T. 5 


IC.41 


100.9 


. 1,402 


0.2 DO 


1.1568 


-0.01R8 


0.0703 


14 )3 e. 02 


19931. 


1920*, 


171,24 


-2.8 


-7.4 


18.05 


1'79 . 


1,330 


0.200 


U.lfr25 


-0.0341 


0. 019ft 


14 JJ 9.0J 


1692t. 


lesct. 


147,88 


-2.3 


-7.3 


17.46 


105.4 


1.2T8 


0.200 


0.1639 


-0.0470 


0.06 81 


14 33 10.02 


1»921. 


18409. 


164.02 


-1.9 


-7.4 


17.22 


107.2 


J. 235 


0.20" 


0.1554 


-0.0555 


0.J657 


14 33 11. CZ 


is<;i6. 


18303. 


158,83 


-1.7 


-7.5 


16.79 


107.8 


1.226 


0.198 


0.1540 


-0.0400 


0,0673 


14 33 12. OZ 


18911. 


18280. 


155,10 


-1.9 


-T. 6 


16.36 


toa.9 


1.223 


0,195 


0,H77 


-0.0I»9 


0.0680 


14 ]J 13.02 


18906. 


1912!. 


153. CI 


-t.9 


-r.9 


15.91 


109.9 


1.207 


0.195 


0. 1'549 


-0,0112 


0.0695 


14 33 14.02 


1S902. 


1B05C. 


i;c.42 


-1.2 


-8.1 


15.47 


106.8 


1.196 


0.194 


0.16^0 


-0.0')7 


C,0712 


14 33 15.02 


18897, 


182 86, 


147. OZ 


-O.l 


-7.6 


15.00 


lOA.e 


1.216 


0.190 


0.t7l« 


-0.0)31 


0.3690 


14 33 S&.C2 


18892. 


18723. 


143.66 


0.4 


-7.0 


14.49 


108.8 


1,269 


0.I8A 


0.1726 


-O.OTfi* 


0.061? 


14 33 17.02 


l8»fT. 


13955. 


140.06 


1.0 


-6.4 


14.01 


108.7 


l,J05 


0.182 


0.1796 


-9.0)21 


0.0^24 


14 33 16.02 


issai. 


19108. 


135.52 


1.1 


-5.9 


13.59 


106, n 


1.321 


0.179 


0.1715 


-O.Oi)* 


0.0714 


14 31 19.02 


ISS76. 


19364, 


13C.87 


0.2 


-5.3 


13.26 


108.8 


1.354 


0.174 


0.158* 


-O.OJ«Q 


0.0702 


14 33 20.02 


18071. 


19526. 


126.76 


-0.5 


-5.2 


13.01 


109.7 


1.381 


0.171 


0.1569 


-O.OJto 


0,3725 


14 33 21. C2 


l«(«b. 


19551. 


123.14 


-0.9 


-5.5 


12.77 


105. T 


1.312 


0.168 


0.1524 


-0.0?t8 


0.0753 


14 33 22.02 


13860. 


19568. 


119.26 


-1.3 


-5.7 


12.52 


IOS.7 


1.377 


0.166 


0.1516 


-0.0255 


0.07)7 


14 33 23.02 


18855. 


19570. 


115.63 


-1.4 


-5.6 


12.25 


108.7 


1.376 


0.163 


0.1529 


-0, 0267 


0.0705 


14 33 24.02 


1^850. 


1946?. 


111.66 


-l.S 


-5.7 


11.99 


IDS. 7 


1.371 


0.J61 


n.l563 


-0.0295 


0.0731 


14 33 2i.02 


188^4. 


193:3. 


10i.B5 


-0.6 


-5.9 


11.74 


108.7 


1.362 


0.158 


0.1459 


-0.1305 


0.37<I 


14 13 26.cz 


18639. 


19342. 


104.04 


0.2 


-4.0 


11.50 


108. T 


l.3'-T 


O.l'it, 


0.t6')9 


-0.07(17 


0.074A 


14 33 2J.02 


18834. 


19348. 


103.08 


-0.2 


-6.2 


11.26 


100.7 


1.357 


0.154 


0.14TI 


-O.0291 


0.0744 


14 33 2e.02 


16829. 


1''31S. 


101.36 


-0.8 


-6,3 


11. 03 


103.7 


1.355 


0.154 


0.1520 


-0.0287 


0.07)9 


14 33 20.02 


18823. 


19294. 


96.62 


-0.2 


-6.2 


10.53 


105.7 


1.35a 


0.150 


0.1614 


-0.0?69 


0,0735 


14 33 34.02 
14 33 31.02 


18.118. 


19262. 


91.12 


1.1 


-5,9 


10.63 


IDB.T 


1.362 


C,146 


O.lMfl 


-0.D553 


COlJi 


18813. 


1898:, 


88,45 


O.- 


-*.o 


10.42 


108.7 


1.331 


0.145 


0.1362 


-0.0365 


0.0750 


t4 13 32.02 


IdOOS. 


18488. 


88.7) 


-i.a 


-6.4 


10.19 


109.7 


1.764 


0.147 


O.U'I 


-0.02 79 


0.0T47 


14 33 33.02 


1880). 


18J74. 


90.94 


-i.i 


-6.6 


9.95 


ma. 7 


1.221 


0.150 


0.1441 


-0.0770 


0.07)0 


14 33 34.02 


UT98. 


1806C. 


9C.92 


0.8 


-6.5 


4.71 


10S.7 


1.213 


0.151 


0.'671 


-0.0794 


0.0715 


14 33 35.02 


18793. 


18055, 


88.05 


1.9 


-6,4 


9.46 


10.1.7 


1.211 


0.149 


0.15*7 


-0.0530 


0.0727 


14 33 3«.C2 


te7e8. 


180T6. 


86,4 3 


1.6 


-«.3 


9.21 


108.7 


1.209 


0.147 


n.1449 


-0.0-07 


0.0745 


14 33 3T,02 


1«TB3- 


18U8S. 


e*,«) 


0.6 


-6.3 


8.93 


108. 7 


1.206 


O.UT 


0.1355 


-0.0231 


0.0J52 


14 33 3S.02 


18778. 


18059. 


95. 2T 


0.3 


-6.2 


9.62 


108.7 


1.199 


0.146 


0.1410 


-0,0?T0 


0.0564 


14 33 3«.a2 


18773. 


1811!. 


(4,24 


0.8 


-5.8 


8.31 


lOS.T 


1.705 


0.145 


0.1359 


-0.0371 


0.0':24 


14 33 40.02 


lATbD. 


JfliOO. 


eft. 28 


1.6 


-5.4 


7.99 


108.7 


1,250 


Q.144 


0.1454 


-0.o:-76 


0.38J5 


14 33 41. C2 


18763. 


19343. 


87.53 


3.2 


-4.9 


7.66 


108.7 


1.324 


0.14) 


0.1637 


-0.0313 


0.072, 


14 33 42.02 


18T53. 


19500. 


84.43 


3.0 


-4.6 


T.i7 


IOS.7 


1.361 


0.140 


0.l44t 


-0.0)21 


0.0733 


14 33 43.02 


18752, 


19248. 


80.57 


0.9 


-5.0 


7.13 


108.6 


1.356 


0.137 


0.12)5 


-0.0293 


0.0754 


14 33 44.02 


187*7. 


I9I42. 


81.64 


-1.1 


-5.5 


6.9Z 


108. & 


I. 339 


0.139 


0.1-'3» 


-0.0265 


0.0748 


14 33 45.02 


18742. 


19165. 


84.24 


-1.1 


-5.9 


6.71 


ioe.7 


1.3)7 


0.1.' 


0.*'?4 


-0.0245 


0.3742 


14 33 4&.Q2 


16737. 


19148. 


84.0! 


0.9 


-s.e 


6.49 


108.6 


1.341 


0,141 


O.ltSO 


-0,C272 


O.O'Sl 


14 33 47.02 


18732. 


19068. 


82.92 


1.0 


-5.5 


6.24 


108. 5 


1.33\ 


0.140 


0.147) 


-0,0258 


0.0727 


14 33 4».02 


lST2b. 


18887. 


81,53 


-0.3 


-5.4 


6,01 


105.6 


1.309 


0.139 


0.1*12 


-0. 0?2T 


0.0727 


14 33 44.02 


18721, 


leitc. 


T9,9T 


-0.2 


-5.6 


5.92 


112.2 


1.300 


0.139 


0,1536 


-0.0266 


0.074B 


14 33 50.02 


lB7ia. 


18277. 


TT.40 


l.D 


-S.» 


5.61 


HT.T 


1.295 


D.138 


9.L555 


-0.0223 


0.0745 


14 33 51.02 


18711. 


182(4. 


.74,61 


2.1 


-5,5 


5.36 


119.1 


1.302 


0.136 


0.1524 


-0.0313 


0.0717 



TABLE 3- 2d. LANDING (CONTINUED) 



/71 



''KL1,KH3* 



Feb. 4, 1972 






I* 33 «;.07 
14 31 33.02 
i* 33 S^.CZ 

1* 33 js.c: 

1* 31 S^..C2 
1* 33 ST.02 

1* 33 ie.ce 

I* 31 5fl,02 
I* 3* 0.02 



•H (-, 



Op, 



I« 34 
U 34 

14 34 
14 34 
14 34 
14 14 
14 34 
14 34 
14 14 



1.02 
2.0i 
3.C2 
1.02 
3.02 
6. C2 
T.02 

a.c2 

9.02 






14 34 10.02 
l4 34 il.OI 
14 34 12.02 
14 31 13. C2 

14 3* 14.02 
14 34 IS.b* 
14 }4 16.02 
14 34 ^7.02 

14 34 te.C2 

14 34 J9.02 
14 34 29.02 
14 34 2L.02 
14 14 22.02 
14 34 23. C2 

14 34 24.02 
14 34 2S.02 
14 1* 2i.02 
t4 14 27.02 
14 34 2e.C2 
14 14 It, 01 
44 34 10.02 
|4 34 31. C2 
14 34 32.02 
14 34 33.C2 
14 34 34,02 
14 14 ii.OZ 
14 34 3C.C2 
14 14 37,02 

14 )4 JS.02 
14 14 39.02 
14 34 40.02 
14 34 41.02 
14 3* 42.02 
14 34 43. C2 
1* 34 4%. 02 
14 34 43.02 
14 34 4«.C2 



1*704 


> 1«401. 


72.04 


l«7Cl. 1947*. 


69. A4 


ist.'ii 


, lt'.7'. 


66.«ll 


ies9o 


> 18420. 


61.64 


l«4«S, 


1S407. 


57.47 


ISbBO. tSS9*. 


51.69 


le674. 


19301. 


S0.19 


Ittt,^. 


202<!3. 


4 7.M 


ia4«>j. 


20761. 


44, H 


t263». 


20664. 


41.56 


ia6»2. 


204 72. 


39.01 


lft4T. 


20109. 


37.57 


I0«4l. 


11*C3. 


36.01 


leiib. 


18785. 


34.13 


16631. 


18524. 


34.16 


lSb2«. 


18530. 


34.11 


ieii2i. 


16766. 


33.93 


Iffcl*. 


i<;044. 


31.45 


tS!>ll. 


isaii. 


31.70 


IffcCb. 


18412. 


29.72 


16601. 


183P7. 


24.06 


IBitb, 


18957. 


26.01 


les^i. 


l':544. 


25.75 


1«*B4. 


l")-)!). 


26.00 


intc. 


I<;ie7. 


26.44 


Uiti. 


18753. 


28,0* 


ia*7o. 


13738. 


24,96 


1916). 


l'!123. 


20.67 


lesad. 


1*336. 


19.46 


ISiSi. 


l')4?l. 


18.64 


1654". 


19506. 


17.10 


it;44. 


1«17T. 


16.52 


l°53<:. 


l-iJCi. 


14.52 


I85J4. 


1916S. 


16.91 


ie52i. 


19219. 


18.47 


taS24. 


I<!147. 


18.17 


16519. 


iC0J7, 


16.45 


l«41?. 


20258. 


15.71 


I not. 


23186. 


15.42 


ItiCZ. 


19921. 


14.66 


194'»7. 


19569. 


14.15 


ia4«. 


I9;i6. 


14.03 


18466. 


n05t. 


13.28 


18401. 


14100. 


12.49 


1*4 7*. 


19293. 


11.62 


l«47l. 


19618. 


10,19 


1(^66. 


19720, 


0.26 


18460. 


194 i7. 


■.91 


l^-S*. 


19169. 


9.24 


1«45C. 


19242. 


(1.67 


lf*4». 


19124. 


7.6> 


16440. 


18927. 


T.I 7 


!«*3>. 


19050. 


T.O* 


19430. 


19212. 


5.97 


t»!42». 


193(8. 


4.21 



x: 

Oh 



2.3 

2.1 
1.8 
3.3 

7.6 
11.8 
12.4 
«. 8 
6.3 
3.2 
1.6 
1.5 
2.T 
3.9 
4.8 
7.0 
9.0 
9. J 
9.6 
9.2 
7.9 
3.2 
11.0 
12.1 
5.5 
1.0 
1.3 
6.1 
7.9 
10.3 
12.0 
H.7 

5. 6 

6. I 
«.« 

12. 5 
10,6 

7.4 
7.2 
6.6 
6.8 
6.7 
6.9 
9.5 
11.2 
10.6 

«.o 

7.7 

T.9 

t.i) 

6,4 

«.4 

9.8 
II. e 
10.3 



H 



-3.1 

-4.9 

-S. 1 

-5.2 

-4.2 

-1.7 

1.0 

2.3 

2.2 

t.8 

1.6 

1.3 
1.3 
1.2 
1.3 
2.2 
2.7 
2,4 
' 2.3 
2.7 
1.2 
3.5 

4.0 
4.6 

*.o 

2.4 
1.0 

4.4 

4.7 

4.8 

4,9 

4.9 

5.1 

3.4 

3.6 

5. f 

5,9 

5.9 

6.1 

6.4 

6.4 

6.4 

6.2 

6.1 

6.2 

6.3 

6.1 

5.9 

5.8 

6.( 

6.0 

6.2 

6.4 

*.T 

6.9 



3,08 
4. S3 

4.59 

••30 

4,(0 

1.71 

3.'-7 

!.)'> 

3.18 

3.11 

3.10 

3.10 

3.08 

1.04 

2.97 

2.87 

2. 78 

2.70 

2.63 

2.37 

2.51 

2.42 

2.11 

2,25 

2.19 

2.17 

2.15 

2.12 

2.07 

2.91 

1.95 

1.91 

1.87 

1.B2 

1.76 

I. 70 

1.63 

t.5e 

1.55 
1.53 
1,51 
1.49 
1.3) 
I. 58 
1.47 
1,27 
1.22 
1.18 
1.13 
1.0« 
t.03 
0.97 

0.91 

0.83 
0.76 



13 



ii«.fr 

115.5 

111.6 
118.6 
115.9 
118.2 

112.3 

101,7 

too. 3 

99.2 

99,0 

93.9 

9a .9 

95.9 

98.9 

94,8 

98. m 

9,1.8 

98.7 

98.8 

93, S 

98,9 

91.8 

95,8 

98.8 

95.6 

97.2 

95.2 

94. J 

94.1 

93,9 

94.0 

94.0 

93.9 

9J.9 

93,8 

91.8 

93.9 

93.9 

41.8 

93-9 

91.8 

9J.7 

93.8 

91.8 

91,7 

4?. a 

91,8 
93.7 
93.7 
93.7 
43.6 
43.7 
43.8 
93,7 






1.324 
1.131 
1,?25 
1.117 

1.310 
1.332 

1.401 
1.45'5 
1.478 
1.461 

1.440 
1.404 

1.320 
1.2J7 
1.2J7 
1.219 
1.249 
1.249 
1.748 
1.204 
1.194 
1.248 

1.12* 
1.161 

1 .197 
1.451 
I. i54 
1.255 
1.261 
1.102 
1.313 
l.ita! 

l.>63 
1.264 
1.268 

l.loa 

1.164 
1.377 

1.3T2 
1.350 
1.301 
1.264 
1.211 
1.226 
1,260 
1,108 
1.320 
1.279 
1,248 

1.2)2 
1.243 
1.21S 
1.215 
1.246 
1.381 






0.113 
0.110 

0.127 
C.121 
0.114 

0.1)4 

0. toi 

0.103 

0.O99 
0.045 
0.041 
0. 092 
0.091 
0,041 
0.041 
D.04t 
0, 040 
0.^8? 
0.097 

0. on> 

O.OS) 

0.079 

0,077 

0.07 7 

C.Ofil 

0,0^> 

0.077 

O.DTO 

0.047 

0.066 

n.O"!! 

O, 062 

0.062 

0.063 

0.06 6 

0.3i5 

C.06) 

0.0"i9 

0.059 

0.05S 

0.057 
0. 15 7 

0-056 

0.044 

0.C52 

0.049 

0.046 

0.045 

0.0*7 

0.045 

0.O4; 
0.042 
0,041 
0. 01T 
0.013 









bo 








C 








■H 








T) ^1 








C CO 


1— 1 


1— 1 


t— 1 


nj ID 


M 


X 


S 


.J (SO 

.Extended 


0.t»4T 


-0.O306 


0.0618 




0.1402 


-0.0175 


0.0647 




0.1475 


-0.0t)« 


0.0718 




0.16H 


-0.0261 


0,0722 




O.l-SAT 


-0.0376 


0. C^ft 




0.2144 


-0.0416 


0.0'.5' 




o.T9n 


-0.04(14 


O.C'>28 




0,1518 


-0,0391 


O.Oliflfl 




0.1413 


-0.0)06 


0.0734 




0. 1 140 


-0. 0281 


0.07)2 




0.1127 


-0.0?0* 


0,0-20 




0. I 3 76 


-0, 0317 


0.0710 




0.1406 


-0.0107 


0.0720 




0.1328 


-»,0?!'7 


0.0729 




o.ini 


-0.0*1* 


0. 07*0 




O.lllB 


-o.oio* ■ 


0.0115 




0,1277 


-0.0170 


O.C4<i< 




O.MJl 


-0.0403 


0.07)4 




0.1336 


-0.0)9n 


0.0'4I 




0, 1315 


-0.0400 


0.07 21 




o.:249 


-O.0?fc? 


0.0702 




0.12'* 


-0.010! 


0,07|o 




o.mi 


-0.0179 


0.0719 




0.1370 


-0,0177 


O.J'OI 




0.09 99 


0,001 fl 


0.C''29 




o.»9nj 


o,oa(.') 


0.0790 




1.1319 


0. 010? 


O.OTftl 




0.125* 


-0. mo? 


0,0702 




0.1162 


-0.0'6* 


0.07O) 




0.1H7 


-0.0143 


0.0721- 




9-1116 


-0.0?55 


0.0''J4 




0. U02 


-0. 0313 


0.0'2O 




0.1000 


-o.ni2j 


0.0704 




0.1053 


-0.0244 


O.OI168 




0.11J5 


-O.CP37 


0.0675 




J-1349 


-0.0298 


0.0695 




0. '.0 73 


-n. 02»* 


C, OTO! 




0.1045 


-0.0?17 


U.0709 




0,1143 


-0.022', 


0.5179 




0,1116 


-0.0*U» 


0, 04 6 




O.IU'- 


-0,0?04 


0.0680 




0.1071 


-0.024 


O.Ct4 




0.1017 


-0.0240 


0.D6 62 




0.1041 


-0.0713 


0.0665 




0.09'* 


-0.0227 


0. 5461 




a.0B65 


-0.0740 


0,9666 




0. oeoo 


-0. 0?2B 


0.0650 




0,014* 


-0.021T 


0.0661 




o.cai 


-O.P'fll 


0.;^>J 




0.1662 


-0. 0176 


COM) 




n.06»i 


-o.o»7e 


0.0429 




0.0729 


-0.0172 


0.0604 




0.0761 


-0.0700 


0,04*4 




0.0761 


-0.0252 


0.0613 




0.0701 


-0.021O 


0.0619 





o 



TABLE 3.2e. LANDING (CONTINUED) 



/72 















*KL1,KH3* 












jj 


4-' 














, c 


u 


X 


in 


+ 


nJ 


tfl 




S 




U-H 


0) 


to 


3 


•V) 


j:: 


+j 




LO 


t4H 


3:s 


CT) 






^s 


1-H 




3 


X 


M-i 






s 


H 


QO, 


<i 


H X 


H 


to 


> 



Nl 



Feb. 4, 1972 



•H 






























Extended 


I* »+ 


«r.oz 


U*)L9. 


HTJi. 5 


JO 5 


k£ Am 9 


0.6^ 


93. T 


1.317 


0.034 


0.0**0 


-0.0197 


0.0&36 


14 14 


4«.at 


lB4t4. 


10066, $ 


.20 


iZ 6« r 


0.61 


SJ.T 


t.isi 


o.r34 


0.0711 


-D.01S7 


0.0636 


14 14 


**.02 


Le404. 


ZOOfl. s 


11 -J, 


9 B* 9 


0.!6 


<J3.» 


l.'ST 


0.014 


O.OTT* 


-0.014J 


0.0651 


1« 34 


SO. 02 


L9401. 


IffZl. * 


88 -T 


») fr.4 


O.Jl 


ti.r 


1.341 


0.033 


0.07TB 


-0.0' SB 


0.0643 


14 3* 


Sl.OZ ] 


lS34a. 


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STDAWIKCUIlEJtTC NOKHALKtAfT 



/73 



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i 9 


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o.to 



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a.2ft 



n.zi 



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to < TAtI < 

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T»U < 



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«0 C>AO 
iO C'AO 
9? Cl»*0 



ao < T*u < loft CPiAO 



ITHeOt 4 fNTSPBICMT 110 < T*V < IZO GPAO 



Fig, 3.1. a. Jet-induced normal force. Do 31 E3, trial 24?. Thrust 
ratio SH/S]y[ of 1.000 to 1.400, without ground effect (H/b > 0.8). 

Key; a. Jet-induced normal force; b. Corresponds to; c. Degrees 



o^ 






/74 



a 

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0.1« 



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,)...i...i...i...i...i...i...r...(...i...t...i...i...(...i. 



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o.e 



.)...!. 



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.t...i. 



0.0 



e.os 



0.10 



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e.ic 



5.»> 



0.19 



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< 


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STi^SQL 




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ro 


< 


T*U 




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< 


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itwot 




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00 


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80 


< 


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ion 


caikD 


STWOC 




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100 


< 


T«U 




110 


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Pig. 3.1.t>, 
Sn/Sp^ of 1, 



Jet-Induced 
400 to 2.100, 



normal force. Do 31 E3j trial 247. 
without ground effect (H/b > 0.8). 



Thrust ratio 



Key: a. Jet-induced normal force 

b. Corresponds to 

c . Degrees 



/75 



STPAMLlWUIieftTU NOftfNT 
0.20 »...l..*l...l...l.* 



.I...1...1...1...I...I...1. 



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a. It 



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9 



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9 5 > 9 



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6 66 6 6 6 666 

6 
b 



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6 4 6 
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.t...l...l...l..il I...l...l..il...l.. 



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0.13 



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stwoi 



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JO 
\0 
60 

an 

100 






20 CXAC 
40 COAO 

60 co*o 

BO GRJhO 
ICO CB40 
IZO G*AD 



Pig. 3.2, 
Sh/Sm of 



a. Jet-induced 
1.000 to 1.400, 



torque. Do 31 E3, trial 24?. 
without ground effect (H/b > 



Thrust ratio 
8). 






Key: a. Jet-induced torque 

b. Corresponds to 

c. Degrees 



o\ 



ne 



STiAKIKCUtlEKTES HOHEMT 
0.» *...)... I. .. I. ..].. 



>|...t. 



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o.» 



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< 


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?o 


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JYNTOl 




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iO 


< 


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to 


C»AO 


it«oi. 




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< 


T«U < 


ftO 


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< 


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Fig. 3.2,b. Jet-induced torque. Do 31, E3, trial 24?. Thrust ratio 
Sh/% °f 1.400 to 2.100, without ground effect (H/b > 0.8). 

Key: a. Jet-induced torque 

b. Corresponds to 

c . Degrees 



I}-Vt*S.I4T 



•<tU .t<Mi* 






iiitt.iz 

S2'««C.U 
11*01.0? 

sr+ei.oz 

42*ei.Q2 

);*ii.o; 

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il*Jt.C2 
il*.2i.<l2 

»j42T.a7 

J24J«.02 

•.2*it.67 
)I4)T.02 

S2*J*.02 




ru>n*f<)>«2 



Pig. 3. 3. a. Dynamic pressure q kp/m^. Do 31 E3 trial 247, landing phase, 






Key: a. E3 trial 2^6; b. Time, sec 






a 






ti-vtn.j'.t 


4 i 


1 I.I -...f ....t. . 


12381.02 • 


••••{••••I 


■ •••■•••*|a«*Bl«*«*l «*•*).* 


17!^2,ez * 






S23«3.« < 






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iiitt.Qf. < 






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S239<i.02 < 






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;23?t.'.2 






»23fT.(}2 < 






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123fl<>,CZ 






<2\CS.C2 






32^01. Ci 






5;*02.02 






»2*(j3.e2 






52*0*. 02 






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;2406.02 






12*C7.C2 






s:»o».o2 






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$;tii.c2 






»2tl2.fi2 






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• 


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* 


. 52*10.02 




M 


92*21.02 




* 


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* 


52*23. t2 




* 


52*2*. D2 




• 


;2*2:.c? 




• 


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« 


52*27.02 




* 


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• 


52*2».C2 




• 


:2*3:.02 




• 


92*31.02 




* 


92*3^.02 




• 


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« 


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* 


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• 


:2*3i.c2 




• 


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• 


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• 


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* 


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• 




• *• •!•««■ 


....U...t....l....t....l. 


t 


.0 

H 


I. 000 



l....t....l....1....l...u....t. 



.I....1..,.1. 



.f....l. 



/78 



I,(!On 3.0'*o *.5M»lS*»l 



Pig. 3.3.t). Altitude H m. 



Key: a. E3 Trial No. 24? 
b. Time, sec 



Z«lt 
S*k 



e3-VCFS.Z4T 


«KU«KH3* 










I*a*«j44 


..l....l.*«>l •••.!. .••!..• 


.!• 


•••t ••••■••••(■•••l« 




.(.... I....I....I 


szjat.ez ♦ 








• 




42]«2.07 ♦ 










* 1 


» SiSSJ.M • 










• f 


32}««.C2 ♦ 










• f 


SZ3S}.02 * 










* 1 


$23S«.C2 « 










• 1 


SjJUT.Oi ♦ 










« 1 


iriae.oz ♦ 










* 1 


iiifi.QZ * 










• 1 


S23ic.cz ♦ 










• i 


52391.02 + 










• 1 


J2392.cz • 










• i 


J23«.a2 ♦ 










* 1 


5239^.02 ♦ 










• 1 


3I3")J.OZ ♦ 






• 






S2]lt.C2 ♦ 






• 






siJ'iT.ai ♦ 






• 






323^«.or ♦ 




• 








mii.oz * 






• 






32*00.02 ♦ 






• 






?2«1.IJZ » 






• 






52*a2.02 ♦ 






« 






9;^4«3.02 * 


' 




• 






•2A&v,0Z ♦ 






* 






)2t0S.O2 ♦ 






• 






5Z«CiS.oz • 






* 






12*01.02 ♦ 






* 






iz*ct.i2 * 






• 






!2M)«.Q2 • 






• 






92410. SZ ♦ 






• 






SZ4It.C2 * 






« 






:24l2.C2 ♦ 










• t 


t24t3.0Z • 










• j 


52*1*. C2 ♦ 










• j 


52*is.ca ♦ 






• 






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'• 






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* 1 


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* i 


)24i4.e2 * 








• 




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• 






52*21. M » 




• 








;2*22.02 ♦ 


• 










S242).S2 ♦ 






t 






•2 43*. 02 * 






* 






:2*2J.0I » 










• 1 


!2*24.0Z • 






• 






52*27. M • 






■ 






i2-.2e.02 * 








ft 




12*29.02 • 










• t 


52*30.02 • 










• i 


52*31.02 • 








p 




■ ,12*32.02 ♦ 
%243}.0Z * 






• 










* 






92*3*. 02 » 








• 




52*19.02 ♦ 








• 




12*3«.F2 » 






• 






92*1T.C2 * 






* 






•2*}e.02 ♦ 


• 










9**J«.« • 


• 










924*0.01 • 


• 












..i.....i....t....i....t... 


• l*< 


..t •••• (••••■••••l> 




■t ••••( ••••(•••> t 


-14.300* " 


-H.0W1 




-lo.ooo 




-^.onn* 


a2 





















/79 






Pig. 3.3.C. Normal acceleration BZ" m/s' 
Key: a. E3 trial No. 24? i b. Time, sec 



t5-¥£»S.l*T 



•«U,«MJ» 



oo 






vzsauoz 
12191. e; 

WlJt.CI 

si;s7.o? 

SiJICM 

lil1?.« 

5fl'>}.CZ 
i219*.0I 

»iH7.0Z 

);V)3.02 

t24C6.0; 

)I*07.M 

•1*11. C2 
4Itl2.0I 

fj'tli.c; 

iHlt.ti 

■*J4«.02 

. Ji.oi 

S2^24.C2 

12*27.01 

12*]C.CZ 
12*11. « 
12*?2,C2 
5:*3].02 

!2*J«.o; 

92*11. C2 

;2«)».« 

;2*it.o2 
12439.0: 

12440.02 




noo*io**z 



JJLVL 



Fig. 3-3.d.- Angle of nozzle rotation. t 



Key; 



E3 trial no. 2 47i t) • Time, sec 



/8l 



»-«i:»s.»T 



•Kit ,«H»« 



I>tt 






«:;:», (U 

??)*!. Ci 
t7}t7.02 

5;vi.o2 

52*0*, CI 
•2*0>.CI 

»J*<JI.02 

•2«(.'ji 

»2*<^.C2 

12*1). or 

•I«l*.02 
»?*!>. CI 

t2*(4.ej» 

»2*U-0» 

f2*is.e2 

J2*11.02 
•242e. C2 
*2*21.02 
52*22-02 

»i*jj.e2 

!i*2*.C2 
J24J5.C2 

»2*2t.C2 

5J*2e.02 
»1*2».0I 
1243C.02 
il*11.02 
52*J2.«» 
i:*]1.i}2 

)2*>4.a2 
;2*ij.t2 

!24}».C2 
i2*)T.0P 

«*)e.i2 

M«40.C2 



.r....i....i....i. 



• t ....I, 



.i....t. 



.N...l....t. 



i....t. ...)....>. 



ITtH 



.1.... I.. ..(.... I. ...I. ...I. 



...t....l„..t..,.l„„I....I, 



I,nnt«ID**I 



Fig. 3.3.e. Elevator angle n. 

Key: a. ES.trial No. 2^7; l3. Time, sec 



a 



t>>vt*S.Z«T 



•Kit ,K»0» 



b^* 



mil. at 
su^.ci 

17*07.01 

S?»K.C? 
12*11. CI 
W*li.«H 

41*11. ;i 
»j*i*.;7 
;j*i*.e 

)7*11.0t 
•IilCU 

Si*l*.02 

S;*1KM 
JiWl.Cf 

S2*:}.02 

ii*?*.«I 

»7*7i.ej 
'.i*7r.ef 

11*7^.01 

t;<]i<oz 

JI*J|.H 
ft*)*. 01 
11*1».CZ 

::*)e.ci 

»*}I.OZ 



I....I....I....1....1. 



.t....1....|....l ••■•(• 



/82 



-•.OOI -4.T0O -*.0'W -2.B00 ")•» I.OBO 



Pig. 3.3.f. Angle of pitch 6. 

Key: a. E3 trial no. 247; b. Time, sec 



C>-Vt>S.14T 



•ntl ,«»*»• 



.I....I. 



.|....|..»t....l....l<....t'»'l....l....l. 



bit 



SMS). 

»;}«* 

»»;*» 

UtCO 
lite* 

*:»:» 



« 

.02 
01 

.« 
.01 

.0/ 

I 07 
.02 

1 01 

,» 

.01 

u 

.01 

.ct 

.02 
,C2 

.02 

.c; 

.02 

.« 

.01 

.u 
■(■I 

.at 

.02 
.C2 
,02 
,02 
,C2 
.02 
.07 
,C2 
.02 
,02 
,« 
.02 
,02 
.02 
.02 
.02 
>«2 
.02 
,02 
,C2 
.C2 
,6» 
.M 
.02 
.02 
,C2 
.02 
.02 
,C2 
.02 
,CI 
.« 
.02 

.at 



/83 



•l.IOi 






..I. ...I.. ..(.... !.•..>• 

1.100 



l.OOO*!'***! 



U'A 



Fig. 3.3.g. Angle of attack a. 

Key: a. E3 trial no. 2^17; b. Time, sec 



^t>-W»l.«» 



•«U ,M1* 






bi*it 



ixttr.oi 
utt't.cz 

tf46*.0t 

4t«*r.u 

t2m.et 
utr«.ai 
»j*T7.ai 

«*.?■*.« 
i.'t<3.a2 

«*»!.« 
Ii*»).nl 



.I....I....I. ...l....t.... I.. ..t....l....l....l...>f ••••)•••• (••••(••;-1""1 ' 



.t....l....t....l.». I. •..!.. •.!.•• 



CO 



1.000 



I.«0 



.(.... I... .|....t....l..»U*..t....1....1. 

1.000 ••eoo 



».fl09»10»*l 



Fig- S-S-h- Dynamic pressure q kp/m . 
Key: a. E3 trial no. 247; b. Time, sec 



■ »-tCtt,t«T 



*KLl*UO* 



/85 



b Ml 



tiMi.cz 

it*ii.ot 

12«tr.cz 

>:*!*. *1 

ii'-<n.ct 
fIV t.oi 

If***. Si 

»i*i>s.et 

•J***.M 

»*«'«. ti 

»J»rj.tf 

fi«t4.C3 

li*T».OZ 

t;*«o.« 

^;*84.Ct 

i2*t*..et 
ii*n,ti 

•:««.« 

»*«1.U 

•;*«}. CI 

3J*t1.U 

;!*<*.« 




4.000*t0**l 






Fig. 3.3.1. Altitude H m. 

Key: a. E3 trial no. 247; b- Time, sec 



t>-W»l.**T 



•■It •■><)• 






b£i 



It 




/86 



-IltOfiQ 



•10.030 



-V.IOJtlJ***! 



W 



Fig. 3.3.k. Normal acceleration BZ m/s' 
Key: a. E3 trial no. 247; b. Time, sec 



t>-«Ut.4«f 



•u.l.o<i« 



huti 



SI4tl 

!»*»* 

•?•.*! 
it*ii. 

iKTV 

«*«r 

!l4fr4. 
fJ4«), 

•.I'-tt. 

»*»«:. 
ti*ti. 

«♦**. 



CI 

.a 

lit 

.07 
.CI 

.ai 

.CI 

.« 

.01 

.o 

.01 
.«! 
01 

.ct 

01 

.01 

.ez 

.02 

.01 
■ M 
.01 
.<U 
01 
Xi 

.or 

.CI 

ei 

01 

oz 
.n 

DI 

CI 
01 

a 

CI 
CI 
01 

01 

01 
M 
01 

u 

01 
CI 
01 
CI 
SI 
01 
01 
CI 
CI 



>l....l. 



I.. 

c.a 



..I.... 

t.ooo 



z.o«> 



t.ooo 



..l....t. 

4><»0 



5.000 



4. MO 



i.oon 



..I.... 



TAtIL 






Fig. 3.3.1. Aiigle of nozzle rotation t, 
Key: a. E3 trial no. 247; t>, Tlmej sec 



(>-«t*S.2«T 



«Kll ,«H)* 



.I....1....I. 



.I....|....|....)..*>t*..>l""l- — I< 






b2>it 



*!**». '-i 

1/44). CI 

;:44i.ct 

tJ4«0.OJ 
•i»»l.Oi 

!i*»4.C2 

«i4f a.oi 
Si4)T.a 

•J4tl.Cf 

•tvif.CI 
)J4»).C2 

J!*t7.9I 

iKbl.Ot 

*I4f9,M 
l'.4H.0» 

*:4Tr.M 

Si4T*,« 

•;4T7.0i 
«4T#.(IJ 

i;4»o.of 
!j4iue; 

5I4S2.0I 

•1-4(4.02 
•}4«1,0I 
;i41»,M 
9/411, o; 

ijttt.o: 

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11444.0Z 

iitii.at 

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/88 






•000' 



...i....l....r....i...-i....»...lt.-.i....i....t..vi""<—'<"" 

-4.004 -z.oco 0.0 2.000 4,000 6. wo i.OSO 



Pig. 3.3-ni. Elevator angle r\. 

Key: a. E3 trial no. 2^7; b. Time, sec 



1>-W»».I*T 



•«U ,wo» 



b '♦»* 



•!**», 
!?4*», 

il**«, 

ll*»o, 
«**l 
*z*??. 
1J*)J. 

iJ»5*, 
«*iS 

«I*5J. 
■I*l(< 

»i**». 

»J**0, 

;j**r 
»i*«i 

92*6). 

5^*4* 

»i*ti 
»i*fri 

51*41, 

',!*Te 

S2*Tl 
W*TI. 
»J*T3 
•.?*'* 
SI*JS 

•1*1* 

•i*I« 

»?*»S 

«*:: 
5:*e* 

»J*a» 

«*«7 

M*»0 

*!*»? 
SJ*«I 

•I*** 

»;*'» 

ii*^b 

M**l 
»!*«* 
»!*" 

41 IOC 



.CI 

cz 

« 

9Z 

.oz 
ei 

.01 
.07 
CI 
.CI 

.oz 

.01 

.01 
.02 
.01 
,01 

,01 

,ej 

,02 

.at 
.ei 

,01 
.01 

.« 

,01 
.03 
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'■I 
.» 
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02 
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CI 
01 
.01 
.02 
02 
02 
« 

ri 

.02 

.02 

01 

02 
02 
02 
02 
.02 

cz 

.02 

.02 

.02 

CI 




/89 



1.000 



I. BOO J.ooo ♦.000 *.ooo ♦.ooo i.ooo 



nr* 



Fig. 3.3.n. Angle of pitch 6. 

Key: a. E3 trial no. 247; b. Time, sec 



-J 
CO 



a 






it-nn.t^i 



eiCU fHH)* 



*!<.*». 

»!***. 

iit>i 
»:*»* 

•1*4'- 

52*71 
>J*T2 
5i*»> 

SZ*It 

it*** 

»I*«T 

;**«• 

»!»-! 

42*»t 



CI 

02 
,02 

.cz 
,u 

,02 
,C1 

,01 
.04 
,02 
,02 

,r.z 

.02 

,02 
.S2 
,C2 
.02 

-ir 

.02 
.02 

.02 
.01 

.d 

C2 
C2 

0! 

.ot 

02 
.02 
.02 
.CI 

.02 

.02 
02 
02 
02 
C2 

.02 

.02 
02 
02 
02 
02 

.02 
C2 

.07 
C2 
02 
02 

.02 
02 
02 
22 
02 

•ex 
01 

.02 

.02 
CZ 



.1 ....!....(.... I. 



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.l....f. 



/90 



I.... 

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,|....t....|. 
0.0 



,f....|....t....l....U...t....l.<**t< 

t.ooe 



i.3oo*ie*«i 



U'« 



Fig. 3.3.0. Angle of attack a. 

Key: a. E3 trial no. 24?; b. Tlme^ sec 



ST««iCIWUtl£»Tt fOtUlHitFT 



e.ze 



•I. 



.|...|...|...l...1...t...l...l...l...l...>...l...)<..1> 



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/91 



0.15 * 



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o.te * 



A.OI * 



ft 
6 « 



4 



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44 4 

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44 4 

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1 
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1 4 

4) 
*** 



t 

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t 

4 



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.l..,l...l,..l. 



. I... I... I... I. ..I. ..)...!. ..I. ..I. 



.I...l...t..,t. 



.1...t. 



.i...t..«a. 



0.0 



o.os 



O.IO 



O.IS 



O.IO 



y-gM 



t.iS 



STxHOt 1 i-NTSPHCHT 

S*«(n, 4 INTSPt tCMT 
iT«90l » £NTJil|CMT 



20 C^AB 

40 of*o 

HO C'AO 



( T«U < 

ZO < T»U < 

40 < ''AU < 

«0 < Tly < 



tviQoi * eft^sctttHT too < »iu < 129 c»»o 



Fig. 3. 4. a. Jet-induced normal force. Do 31 E3, all flights listed In 
Table 3.1. Thrust ratio Sh/Sm of 0.725 to 1.000, without ground effect 
(H/b > 0.8). 

Key: a. Jet-induced normal force 

b. Corresponds to 

c. Degrees 



vo 



a 



o 



STUAHLINOUIIEATC NOAMLKNAFT 



0«Z0 



.t...1...l...|. 



■ t. 



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o.is • 



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S S 4A> 65 6 6666 6 6 6 66 6 6 6 6666 6 6 66 

i i fS6 6 6 5 566666 6 6666 666666 6666 6(>6 
S ;) ; 6 6 66666 666 66 (6 66 6 66 

6 6) SIS » 56 666 6666666 66 66 66 6 66 6 6 6 6 6 



6 
66 



0.10 



O.CS ♦ 



S ;J1 f 66666666666666666 

9 9> S 9$} !5ISS S IS 16 66666 6666666 666 
nn 3 f S S S 666 6 666 66 6 

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6 



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6 66 

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I 1 



/92 



0.0 



0.03 



O.IO 



0.19 



P. 19 



0.30 



V-EFF 



StPBCJl. 




C>ITSPP ICHT 





< 


TAU « 


zo 


CPiD 


SfFjlJL 




ENTSfP ICM' 


zo 


< 


f/iy r- 


*0 


GfiD 


SYfBCU 




EUTSPmcHT 


40 


< 


»«U '■ 


60 


0»*0 


StHBC 




E'lTSPP ICHT 


60 


< 


Till 


ITI 


CiO 


SYfiaci 




E-iTSCalC+T 


60 


< 


T*!J .. 


A 10 


r.pia 


STTJOL 




T-.NT^imrCMT 


lao 


^ 


•til 


■-e 


"■Pi!? 



Fig. 3.M.b. Jet-induced normal force. Do 31 E3. Thrust ratio 
Sfj/Siyj of 1.000 to 1.400, without ground effect (H/b > 0.8). 



Key: a. Jet-induced normal force 

b. Corresponds . to 

c. Degrees 



STKAHLJftCjIIUTE NOKNALKltAPT 



OtZO 



.t...|...|...t. 



,.u..t.6. i...i6..r...i...i...t...(...i< 

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»6 6 6 

66 « 6 6 

66 6 6 6 



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/93 



6 
66 



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o.ie * 



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9 66 64 

9 6f) 6 6 

5 ) 6 19 

s ii 

9 3 9 

3 * 9 

99 9 6 6 

9 

959 
ȣ 9 
99 9 6 

59 99 

99 999 9 
9 9 J 

99 
9S 
9 
9 



66 6 6 69 

666 6 6 6 9 6 
9 6 6 66 6 66 6 6 66 

6 6 66 69 66 666 

6 66 6!6 66 6 

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6 464 666 66 6 66 6 666 66 66 6C6 6 66 6 6 

4 6 ^666 6666666 66666 6ft 66ft 6 6 

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ft 6 66 6666666666 6 6 6 6 6 6 696 



6 6 

6 
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6 66 66 6 

6 6 6 6 66 

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6 6 6 6 6 6 



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.\.,.u 



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0.09 



o.ia 



0.19 



a.f.ii 



3.79 



0.9» 



V, 



v-irr 



STlfSOL 


t 


CMTS^^KKT 





< 


TJU 


^: 


-JO 


CflAO 


STcaoL 


? 


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SO 


< 


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< 


hO 


C»«0 


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< 


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* 


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60 


< 


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• 


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tJso 



^'TC! 4 EWTSPBIC"* irtO < T".( 



■1 <1P*0 



Pig. 3.4.C. Jet-induced normal force. Do 31 E3. Thrust ratio 
Sh/Sm of 1.4oO to 2.100, without ground effect (H/b > 0.8). 



Key: a. Jet-induced normal forces 

b. Corresponds to 

c. Degrees 



OO 
H 



CD 

ru 



a 

STII«HI.IhDUtICItTES HCHENT 
0.10 «...!. ..I... I. ..I.. 



.I...I...I. 



,l...t...t...l...1...l. 



.1. ..!...)...). 



,t...l...l...l».t...l. 



0.1» * 



o.to * 

♦ 



+ 
e.es * 



» 6 



« «» 



«a 



S 55 



4 4« 444* 4 
44 44444444 4 1 44 
4 44 4 441 I 4 
4444 2444 4 
4 4 4 4 

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/94 



0.0 



9. OS 



0. 10 



o.ts 



o.zo 



9-J5 



0.13 



V-tff 



SYKOOL 

S'rraoL 

SYMJOL 

SYnac;. 

StUSDU 



ENTSCRICHT 
EWSPCICMT 
ENTSPRICHT 
fNTSP'iCHT 

EUTSPPICMT 



EMTSCITCHT 100 



TAW 

TAU 

TiU 
TAU 



?a GB4D 

40 amo 
60 c«*o 

80 C*tO 
100 GDAO 



Fig. 3. 5. a. Jet-induced torque. Do 31 E3. Thrust ratio 
Sh/Sm of 0.725 to 1.000, without ground effect (H/b > 0.8) 

Key: a. Jet-Induced torque 

b. Corresponds to 

c . Degrees 



a 

ST*AH|.tKCUI(E>lTE$ NOnENT 
e.» *...t...|...|...|.>.|< 



/95 



O.IS 



0.10 



0.03 



0.0 



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s» 



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t 6 2 



2 « 



t S 4 I 

6 « 6 6t 6M6 « 



6 I 
66 6 



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66 



5 
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S9333 3333533 33 3 36 3 36 66 662 6 I 

S S -66 16 

33 6 6 6 

66 ( 

6 6 
6 



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6 1 



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.I...I. 



,l...t...|...|...t...t...I<>..t...t...t...l...l...l. 



0.03 



0.10 



0.13 



o«;ft 



C.Z3 



0.39 



b 



V-EFT 



straoL 


I 


ENTSPaKKT 







T»U 


< 


zo 


MAD 


SYfaoi. 


z 


SKTSORICHT 


zo 




T*U 


< 


40 


CfiO 


srnnot. 


3 


ENTSlKtlCfil 


40 




TiU 


< 


60 


CP40 


STrSui. 


4 


ErttSiTlCMI 


60 




tJIU 


< 


BO 


CI>AD 


STKICL 


s 


tUf^POICMT 


80 




•'»u 


< 


100 


C»4D 



sri^aoL 6 ENTj^PicHT IOC < ftM < no cpto 



Pig. 3.5.b. Jet-Induced torque. Do 31 E3. Thrust ratio 
Sh/Sm Of 1.000 to 1.400, without ground effect (H/b > 0.8) 



QO 



Key: a. Jet-induced torque 

b. Corresponds to 

c. Degrees 



oo 

■ir 



StOAHLIMMIIEIkTES MOHENT 



e.to 



.|...|..,I...1...|...I...I...I. 



.1...). 



,i...t...i...i...i...t...i...t...r».i...i...i...i...i...i...i. 



«.15 



4.10 * 



4 M « 



0.0) * 



S 5S 55 ♦ 

3 J J 5S 3 « 

9S 5?S 5 556 ^itt «fr M6 6 « 6666A 66&!&6«666btb6?4<iMA6 
59 S995SS555 5969«5999» »« «45SM AAA 6« 666ft«A«6C>6&«66S« « 

55 3)5155555 » ft 5 5«& AMt « fr 66i 6»6» 

5 96 « 69« « « 6 95 

» 9 6 



Z 6 

3 3 2 2 2 

♦J i 5 » ? I 1 

44 49 3 )Z2 161 1 

346 3 16111 199 

4 4 3 61611 66 II 

4 464136 6 1 614!4 

4 4fr b 66 6 66 66 26A 6 66 66 6 66 4 4 

4&4666666«&£66666ta6«66 6A666666&666666bb666666<>96& 6 

6 6666666 66666666665565 66 4 
6 6 666 6 69 65 666 



1 6 66 



'6 



6 6 



I 4 
9 
6 
6 9 

4 6 4 
666 99 6 



0.0 



.t...l...l. 



.t...1...t. 



.t...9...1. 



e.e 



0.09 



O.IO 



0.19 



O.ZO 



4.29 



0.30 



STKJCl 1 ^NTliPPICMT 


< TAU < 


ZD CP4D 


Stf^QL 2 ENTSfPtCHf 


2P3 T Tllll < 


40 O'iO 


^ynaOL 3 E'<TS»RtCHT 


*0 < TAU < 


60 GP*0 


5ifT,ot. 4 enTSPPicMr 


60 '• T>'r < 


*I0 CAP 


StKaai, 5 ENTSfRICKT 


to < T.l'. f 


(tlO C*iO 


tTviri. 6 «HTSoi>t»:t" 


100 ' T/ii' • 


^?0 r,|i»o 







Fig. 3.5.C. Jet-Induced torque. Do 31 E3. Thrust ratio 
S^/Sji/f of 1.400 to 2.100, without ground effect (H/b > 0.8) 



Key: a. Jet-induced torque 

b. Corresponds to 

c. Degrees 



20 



AZ 



15 



10 




/97 



Fig. 3.6. Do 31 E3 flights, mean Jet-induced normal force 
from Pig. 3.4. 

Key: a. Open symbols 
t) . Solid symbols 



CO 



STKlfttlKDUIIEIkTe N9HAI.KrtfT 



CO 

en 



«.te 



.1 1...I...I...I...1. 



. r. .. f.. . t. . ei. .. u. .»... r. ..)... I. ..i...t. ..!...(. ..I. 











4 « 


464 










6M 6 M 












6 t«M 












* * « 


6 6 








6 


6ft (• 


6 6 6 










4 6A AM 6 












4 4 










» 


4 




0.1 s 






» 












4 5 S » 


6 








5 


* SiSJ 


6 4 










» » 










• » 


» 






















n > 












»SJ 












»»» » 












4 » 


i5 






0.10 
















> > f 




1 








s 




} 


1 






» 5 


















J 


























e.o) 










1 1 



/98 



0.0 



.l...t...l. 



.t...l. 



.I...I...I...I. 



.1...). 



.t...I...1...l. 



.I...I...I. 



,t...l...t. 



CO 



O.M 



O.IO 



o.n 



O.T^ 



.?» 






9 < TJU < 

;n < 'du < 

*0 < Til; < 

ftr < TiJ <■ 

10 < T*U < 



C 
at ao 



?T»t»(]!. b imsoncMT |ir v; TAij f ij(> ctir- 



D.ll 



V-f" 



Pig. 3.7. Jet-Induced normal force. Do 31 E3 trial 24? with 



0L( 



correction. Thrust ratio S^/Sp^ from 1.100 to 1.550, 



without ground effect (H/b > 0.8) 



Key: a. Jet-induced normal force 

b. Corresponds to 

c. Degrees 



a 
mtMft.li 

o.te 



iDuricrres hcwht 



/99 



.t...i...i. ..(... I 



«.xs 



«.10 



S 9 



» 9 f 9 1* 

»»» * J a 



• I 

» 6 1 



A 4 » » * 1 
♦ t 

t*ft « t 



4 
4 * « 

« 4 

4 



«.«S 



a.e 



.i...t...t...j...r. 



.1...1...1... 



0.0 



o.os 



.U. *!...)... I. ..I. ..I... I. ..I... I. 



0.10 



0>)S 



e.ir 



.i...t...i...l».i...i...l.. 



t.ti 



o.» 



*.iM 



st"eOL 




D 

EMTSl>»tCMT 







T*(l 




10 


C 


ST"B01. 




exTjppic"' 


»? 




T*V 




*0 


ceto 


Sr'dOt. 




CNTjmtMT 


*n 




'i'J 




♦-) 


c««o 


!*«5CL 




iffTsmtM' 


»o 




tAU 




no 


c»*o 


Srj^OL 




THTSPP I tut 


«0 




T«U 




lOfl 


C*tt> 


tY«OL 




mTSfUftHT 


100 




T«) 




ra-' 


t«iO 



Pig. 3.8. Jet-induced torque. Do 31 E3 trial 247. with Mq and 
a^ correction. Thrust ratio Sj^/Sjyi from 1.100 to 1.550, 
without ground effect (H/b > 0.8). 



00 



Key: a. Jet-induced torque 

b. Corresponds to 

c. Degrees 



CO 



O • =^ 



^ 






o 



a 
a 



♦ 



:^ 



as- 

o 

at 



0.1 



■ for 



O 



0.1 



04 



-*^ 



A. 



/lOQ 



C.330-0.3St 



lis 



1.18 



0.3U-Q.5J9) 1C.6 



011J-0]C& GE 



0.I17-0J75 BT 



O.rJO-OlO? ICI 



a.ics- 0.179 loa 






a t»j 



<£> 



Fig. 3.9. Do 31 E3 trial 247 
versus angle of attack. 



jet-induced normal force coefficient 



1 3J 



1.19 



1.50 



l.tO 



CIS 







/lOl 



1) Vq jfjj^i^ = Indicated velocity at H/b = 0.8. 

Fig. 3.10. Do 31: jet-Induced normal force during 
vertical landing. Comparison between wind tunnel 
and flight test. . 

Key: a. Plight 

b. Corrected 

c. Uncorrected 

d. Wind tunnel measurements 



89 




/102 



ai 






t 



OlI 



u 



y 



y^ 



y 



/ 



./ 



0.1 



V«rfu9bor«( Stcyermom«ftt 
b4i ^tx Londttronsition 



0.1 



V.ff. 



OJ 



Pig. 3'11« Do 31: Jet-induced pitch torque 
during vertical landing. Comparison between 
wind tunnel and flight test. 

Key: a. Wind tunnel measurements 

b. Flight 

c . Corrected 

d. Available control torque during 
landing transition 



90 






a 



Schwc^kwinkel T»«9 3* 
Schuur>;vtou t.l 6 5^/5^ - 1.5 



oo( 



u 



00 1 



«ji) 



M) 



aioi 









—c — 



c 
rius Kf. 

JO 






^ A/ / / /n V ' \' Ky ' ^' ■''1' ^ // /\^ 



■ act 











<:yf^'''''\y//)\ 






01 



— 

0.i 



1 b^ 



!/ 



/ 




o« 



W.....— - 10 



H/B 



u 



Fig. 3.12. Do 31: Jet-Induced normal force due 
to ground effect during four vertical landings. 

Key: a. Angle of nozzle rotation 

b. Level of thrust 

c. Flight number 

d. Wind tunnel measurements: all power 
plants on takeoff thrust 



/103 



91 



/104 



Schwenkwinkel Tw93* 
Schubniveou 1.1 * Sh/ Sm «1.5 



FLUC Nf. 
2 47 



— ■Q a 3 ) 

— ^ tLS 

.~..\^_.. 14 



AM / AM \ 




t.2 1.( 

H/B 



-0.«»»T 



Pig. 3.13. Do 31: jet-Induced pitch torque due 
to ground effect during four vertlcaLi landings. 



Key: a. Angle of nozzle rotation 

b. Level of thrust 

c . Flight number 

d. Wind tunnel measurements 
plants on takeoff thrust 



all power 



92 



4. Guidelines for No'del' Tests' for Future' V/STOL' Development /105 
Overview of Contents 

4.1. Introduction [not included with German document] 

4.2. Notation 

4.3. Principles Pertaining to Models 

4.4. Test Method 

4.5. References 

Figures 

4.1. Jet-induced pressure distritiutlon on the underside of a 
panel with a central Jet. Mach number effect. 

4.2. Effect of jet Mach number on jet-induced force in Do 131 
hover close to ground. 

4.3. Effect of Jet Mach number on Jet-induced pitch torque in /IO6 
Do 31 hover close to ground. 

4.4. Do" 31 interference measurements. Effect of air feed lines 
on the aerodynamic coefficients. 

4.5. Interference from inlet and outlet flows on a partial 
wing/fuselage model. 

4.6. Effect of nozzle position, in the longitudinal direction, 
upon pressure distribution on the wing. 

4.7. Compilation of practical methods for power plant simula- 
tion in model tests. 



93 



4.1. Introduction 

[Section 4.1 not Included with German document.] 

4.2. Notation /I 08 

AA Change in lift due to jet interference 

b Wing span 

C^,C]yij,Cy ■• Aerodynamic coefficients of llft^ torque and drag, 
respectively 

Cp Pressure coefficient 

Dj Diameter of thrust nozzle 

H Ground distance 

Ay Mean aerodynamic chord depth 

AM Change in pitch torque due to jet Interference 

Ma Mach number of thrust jet 

Pq Total pressure in thrust Jet 

p^ Ambient pressure 

Sqs ^MTW Gross thrust 

v^ Aircraft speed 

v-g Power plant inlet velocity 

V. Power plant jet velocity 

AZ Change in lift thrust due to jet Interference 

a Angle of attack 

p Density 

4. 3- Principles Pertaining to Models /109 

4.3.1. Inlet Flow 

The simulation of inlet flow with a model must be done in 
such a manner that the flow conditions associated with the full- 
scale version are set up, both in the power plant inlet and in the 
region surrounding it. Certain conditions with regard to pressure 
drop, dynamic pressure recovery and uniformity of flow must be 
satlsifed at the inlet for efficient and disturbance-free operation 
of the power plants. Maintaining the same ratio V„/Ve between 
free stream velocity and inlet velocity can be considered the 
most important principle pertaining to models. Since separation 
phenomena at the lip of the inlet or at the hub are a function of 
Re number, approximately similar conditions to those associated 

94 



with the full-scale version must be created by artificial transi- 
tional means if the ratio is not maintained with the model. Mach 
number effects are not so important., in contrast, since the 
usual mean inlet velocities do not exceed 150 m/s. 

The external flow field of the inlet flow is governed by the 
sink effect, which, if compressibility efffe^'cts are neglected, is 
determined only by maintenance of the kinematic flow condition 
in the form of velocity ratio V„/Vg. 

^.3.2. Power Plant Jet 

The model principles which apply to Jet simulation are 
governed by the principles of free jet propagation in quiescent 
or moving air surrounding the Jet. The most important similarity 
parameter is the ratio of the momentum densities of the oncoming 
flow and the Jet (pooV«/pj-Vj ) . From this is derived the so-called 
effective velocity ratio 






/llO 



which has generally been adopted as a useful characteristic quan- 
tity in Jet interference processes. Temperature effects can 
thereby be neglected for all cases encountered in practice. Mach 
number plays a certain role in free Jet propagation; the drop in 
dynamic pressure along the axis of the Jet takes place more 
slowly at high Mach number than at low Mach number. 

Measurements in [4], Pig. 4.1, show the corresponding effect 
upon the Jet-induced pressure distribution on a panel with a 
central Jet. Measurements with the 1:20 model of the Do 131 in 
hover close to the ground likewise show that jet-induced force 
decreases slightly with increasing Mach number. Pig. 4.2. The 
Mach number effect will probably become insignificant for future 
V/STOL aircraft with fan power plants of relatively low Jet Mach 
number . 

The effect of the Re number of both the free stream and the 
Jet can be neglected. However, initial conditions in the nozzle 
outlet have a considerable effect on free Jet propagation. They 
Include the distribution of static pressure and total pressure, 
as well as the degree of turbulence. The latter was not taken 
into consideration in those jet interference studies known to us. 
Its importance will increase, however, as more is done in the 
future in the way of measures aimed at the rapid decay of the Jet 
due to noise and erosion considerations. For fan power plants, too. 



95 



?T?^?^*?*TS5 



I* ^^^•iJf ^•■(^■Ki^v^^^'if^^ 



rei ^^yg y^ ^y^jB jjg -g jj^gj** " y *q7 



M 







It is necessary to attend to this point, since attention must be 
devoted to blockage by the relatively; large hub and to a residual 
spin In the Jet. 

4.4. Test Method /HI 

The decisive point for a reliable V/STOL test method is 
power plant simulation. The first generation of V/STOL aircraft, 
including the Do 31, for example, was equipped with single-stage 
power plants which were installed in engine' pods on the wings. 

Due to the location at 
which they were Installed, 
and because the inlet 
momentum of these lift 
power plants amounted to 
only about 20-25^ of 
Jet momentum, the 
interference forces 
associated with inlet 
flow are negligibly small, 
and only the pure momen- 
tum components in drag 
and in pitch torque need 
be considered. Thus the 
simplest method of power 
plant simulation could 
be applied to Jet inter- 
ference measurements in 
the wind tunnel, namely 
the discharging of com- 
pressed air. An addition- 
al advantage of this setup was that the entire discharge system 
was svispended separately from the model and wind tunnel balance, 
on a system which follows the angle of attack. Power plant 
thrust and aerodynamic forces on the aircraft were thus measured 
separately, allowing very precise measurements of the Interference 
forces. The design of the wind tunnel model and the test setup 
have already been shown in Section 1, Pigs. 1.5 and 1.6, with 
the Do 31 serving as an example. A color photograph of the 1:20 
Jet interference model of the Do 31 In the Dornier wind tunnel 
is shown ■ above. 

The colors show the following: . /112 

Red; 1:20 model, suspended on the wind tunnel balance. 

Blue: Air-line and follower system, mounted on the turn- 
table independently of the model 

Yellow: Support column for the point of rotation of the com- 
pressed air follower system. 







I* lwtMii.tW#{t fTiilrfinrir^iVl -^'■--'^- ■-■-*■■-'- ^^'■-*'^' ^ l.^'i-^'^'^ 




96 



The effect of the air feed lines on the aerodynamic coeffi- 
cients was determined from two comparative measurements with and 
without pipeline. The effect on drag is considerable, that on 
lift is negligible, and zero torque' must be corrected by 
Aciv[ = +0.02 J see Pig. 4^ii. As was shown in Sections 1 and 3, the 
Do 31 Interference measurements yielded good results. 

For future V/STOL aircraft with fan power plants or two- 
stage power plants of high bypass ratio, inlet momentum is almost 
as high as outlet momentum. The contribution of inlet flow to 
Interference is thus on the same order of magnitude as that of 
the Jet. Pig. 4.5, taken from [6], is an extreme example of this. 
The force in the lift direction induced by inlet flow far ex- 
ceeds the lift Induced by the Jet. Inlet flow Induces a con- 
siderable tail-heavy torque. 

Although the larger component of the force Induced by the Jet 
Is operant on the underside of the wing, the effect on the pres- 
sure distribution at the upper surface of the wing is not 
inconsiderable, as Fig. 4.6 from [5] shows. Now if the power 
plant inlet is located close to or on the upper surface of the 
wing, an interaction of Jet and inlet flows occurs. 

The necessity of simultaneously simulating inlet and outlet 
flows in future V/STOL model tests can be seen Just from these 
two examples. 

The figure shown below provides an overview of the power 
plant simulation methods which are available, and Fig. 4.7 gives 
a compilation of practical methods for power plant simulation in 
model tests. 



/113 



_a_ 



DRUCKLUFTSTRAKL 



Druckluttiytttm beriiru 
r\ngtfrct gegtnub«r 
Fiugieugtelle b 



EJtKTOR-TRIEBWERK 




CEBLASE MIT F..-MOT0?i TU=!eiHefjr.LSl>£f 



$ 



[^. Motor 




i 



7^^ 



r?-L 



Possible methods for power plant simulation in 
model tests. 

Key: a. Jet of compressed air 

b. Compressed air system makes not contact 
with airframe 

c. Ejector power plant 

d. Blower with electric motor 

e. Turbine blower 

f. Compressed air 



97 



The discharge of . a , compressed air Jet at the location of 
the power plant nozsle is the simplest type of power plant simula- 
tion. Inlet flow is not simulated. As already mentioned, this 
method was applied successfully to the Do 31. The list in 
Fig. 4.7 also shows that a relatively large number of jet Inter- 
ference studies were performed in England and at NASA with this 
technique. However, these always Involved VTOL configurations 
with Jet power plants of high momentum density or measurements in 
hover with the ground effect, in which cases Inlet flow is 
unimportant. 

In the case of the ejector power plant, the high-energy 
primary Jet sucks air from the inlet by turbulent Jet mixing, and 
a multiple of the quantity of air which was blown in Is discharged 
at the outlet. A relatively long mixing length is necessary for 
this, however (at least five mixing duct diameters). Structural 
length can be considerably reduced through the use of multiple 
nozzles for the primary Jet, so that approximately the size ratios /ll^ 
associated with bypass power plants can be realized, as can be 
seen from the list in Fig. ■4.7. This method has recently been 
successfully applied by Dornier for recirculation measurements, to 
simulate lift fans whose height is smaller than their diameter. 
No empirical Information is available for jet interference 
measurements. 

Blowers driven by electric motors to simulate lift fans have 
been used by the RAE and AVA (see Fig. 4.7) in several Jet inter- 
ference studies on VTOL components. Depending upon space 
conditions, the electric motor was connected with the blower via 
a short shaft, an angular drive system or an extension shaft. 
Guide vanes eliminate rotation, so outlet flow is quite similar 
to the large-scale version. Inlet measurements are also possible 
at the same time, and the measurement of power and torque provide 
information concerning the fan characteristics in transition 
flight. i:in the case of blowers driven by extension shafts, 
vibration problems must be expected. The effect of extension 
shaft blockage upon flow about the model is highly dependent upon 
the aircraft's configuration. This point is not considered to be 
critical. The AVA Gottlngen provides a tested series of high- 
speed three-phase motors, with blower rotors. 

The blowers with blade-tip drive used to simulate lift fans 
are in some cases still under development (AVA), or they are 
already available as complete units. Although no prices are 
available, it is estimated that the price is to be a multiple of 
that for the blower with electric motor, to say nothing of main- 
tenance expense and maintenance requirements. 

In summary, the following recommendations can be made con- 
cerning the test method to be selected for future V/STOL aircraft 
with lift jets: 



98 



1. The Interference effect of power plant jets Cjet power 
plants with or without bypass and fan) in hover, with and without /115 
ground effect, can be measured with sufficient accuracy in model 
tests using the simple method of compressed air discharge, 

2. Interference between cell and power plant in transition 
flight can be determined reliably only through the simultaneous 
simulation of Inlet and outlet flows in the case of V/STOL 
configurations with lift fans. At present, wind tunnel models 
with blowers driven by electric motors are best suited for this 
pu'rpose. 



33 



4.5. REFERENCES 

1. Trebble, W.J. a., '^ The aerodynamics of V/STOL aircraft. /Il6 

Part G: Techniques for the aerodynamic testing of V/STOL 
models," Von Karman Institute for Fluid Dynamics, Lecture 
Series 9, May 13-17, 1968. 

2. Melzer, E. and Wulf, R., "Possibilities for jet simulation in 

the 3 m wind tunnel of the DFVLR-AVA G'ottingen," 
DGLR Paper No. 70-04?. 

3. Thiel, E., "V/STOL jet Interference: study of suitable 

measurement methods for future V/STOL transport aircraft 
development," Dornler Test Report VW 630-Bl, 1969- 

4. Genty, C. L. and Margason, R. J., "Jet-induced lift losses on 

VTOL configurations hovering in and out of ground effect," 
NASA TN D-3166, 1966. 

5. Carter, A. W. , "Effects of jet-exhaust location on the 

longitudinal aerodynamic characteristics of a jet V/STOL 
model," NASA TN D~5333, 1969. 

6. Williams, J., "The aerodynamics of V/STOL aircraft. Part E: 

Turbo jet/turbof an aircraft," Von Karman Institute for 
Fluid Dynamics, Lecture Series 9, May 13-17, 1968. 



100 



.0016 



.001? 



.OOOS 



.OOOi 




/117 



r/R 



Fig. 4.1. Jet-induced pressure distribution on 
the underside of a panel with a central jet. 
Mach number effect. 



101 



H/b 



/118 




-o.u 



Fig. H.2. Effect of jet Mach number on Jet- 
induced force in Do 131 hover close to 
ground. 



102 



/119 




-0.02 



Fig. 4.3. Effect of Jet Mach number on Jet- 
Induced pitch torque In Do I3I hover close to 
ground. 



103 



mit 
ohne 



Rshrleitung 





Ca 

1 ** 




Ca i"-^ 














nn 


; 








ri r 


/ 








' 


1/ 








L7 






k 


_< 


/) 


f "^ ) 

c 

i : 


,0 ''^vv^f'l 



2k =*s* 



/120 




104 



Fig. 4.4. Do 31 interference measurements. 
Effect of air feed lines on the aerodynamic 
coefficients. 

Key: a. With, without pipeline 
WE = horizontal plane 
riK = flap angle 



So 



l.i 



1.3 - 



1.2 - 



1.1 ■ 



VO 



0.9 - 



0^ 



0.7 - 




/121 



0.7S (ohne Fltjgel) / t 



r — v-i — iv""^ y^-^-^ J- 







V« /V^ 



Fig. 4.5. Interference from Inlet and outlet 
flows on a partial wing/ fuselage model. 

Key: a. With Inlet and outlet flow 

b. Outlet flow only 

c . Aspect ratio 

d. Without wings 



10 5 



o 



a KlappenausscMog 40* 
Strahlaustrittswinkel 90* 
Ousenhochtage z/l a -0.64 

1,0 



AC, 



ACp 



0.S 

-0.5 
-1.0 
-l.S 
-2.0 
l.S 
1.0 
O.S 

•O.S 
-1.0 
-l.S 
•J.O 
-15 





















„_,_ 




--.V 




f 


■^ 


























1 °' 


JKnla 




2.00 




































^" 


V 












/ 

1 


.^ 


'"■'■" 


--li. 


^c^ 


. 


^ 


i 
































% 


'e » 


! 
0.50 1 

































1 






—TTii-J b.u 


,-^ -^ 


" ^ 


/'v 














> 


*^,^__ 





■»— I- 


; 


\„ 


f 










i.'-' 




\ 














\ 




■ 


0.50 































1 














iX- 


r 


_** 


"I 


li-c: 


^"■^s 


1 














1 
■ 


— 












x/ 


1 

c = 0.75 



































02 a< OjE 08 UO 12 \L 



02 Di 05 09 1.0 12 l.i 
x/c 



OCERSEITE b 

UKTERSEITE 

(V. / Vj )^ = 0.10 



/122 



^^^^ 
















^"^r 


I? 


/ 










;.' 




/ 


















X 


ti = 0.25 










. 





















> 












1 


\ 




P 


■"7" 


.,'" 


""^-...- 




^ 












y 






















1 

x/c = 1.00 



































PS Oi6 PS ae lii 1.2 i/> 
x/f; 



Pig. ^.6. Effect of nozzle position, in the longitudinal direction, 
upon pressure distribution on the wing. 

Key: a. Flap angle, jet exhaust angle, nozzle position (height) 

b. Uppsr? ...'Surface, lower surface 

c. Nozzle position 



Fig. 4.7. Compilation of practical methods, for power plant 
simulation in model tests. 



Firm/Institute 



Project 



Literature 

'r.e.f.er.enc.e. . 



/I23 



1. Compressed air Jet 
Dornler 



Do 31 V/STOL transport aircraft VW 537 
with jet lift and lift/thrust 
power plants 



Hawker 

Slddeley Av, 

NASA 



RAE 



DFVLR 



PII27 VTOL combat aircraft 
with Jet lift/thrust power 
plants 

VTOL configuration model with 
Jet lift power plants 



VTOL component model with 
Jet lift power plants 

V/STOL transport aircraft, 
principal model with Jet 
lift/thrust power plants 



2. Injector power plant 
NASA 



AVA 



MBB 



VTOL configuration model with 
Jet lift and lift/thrust 
power plants 

Airbus with bypass power 
plants 

VTOL combat aircraft with 
lift and lift/thrust bypass 
power plants 



zfw 15/7 



NASA TN D-3166 
NASA CR-1297 
NASA TN D-^2380 
NASA TN D-3213 
NASA TN D-1400 

RAE TN AERO 2971 
ARC CP 718 

DFVLR Report 70-28 



NASA TN D-4812 
NASA TN D-5727 
NASA TM X-1758 

DLR Report 70-28 



DLR Report 70-28 



/124 



Blower with electric motor 



Dornier 



AVA 



Do 31 V/STOL transport 
aircraft 

VTOL half-model with lift 
fans 



VW 313 



DLR Report 70-28 



107 



Pig. ^.7. (continued) 
Firm/Institute 



Project 



Literature 

re.fer.en.ce. . 



3. Blower with electric motor 

RAE Wing with lift fans 



RAE 



VTOL component model with 
lift fans 



RAE TR 67302 
RAE TN AERO 26^13 

ARC CP 597 



4. Blower with blade-tip drive 
NASA , /: 



/1 2 5 



AVA 
Dowty-Rotol 



V/STOL transport aircraft 
model with six lift fans 
In wing 

Project for a turbine blower 

Blower with blade-tip drive 



Tech. Develop- Blower with blade-tip drive 

ment Inc . , 

Ohio 



Douglas Air- 
craft Co. 



DC 10 



NASA TN D-5695 

DLR Report 70-28 
[1] 

Manufacturer's 
prospectus 

J. Aircraft 8(7) 



108 



5. Basic Material' for' Es'tlinatln'g Jet- Interference' in' Hover' and /1 2 6 

' In 'Tra'n's'lt'l'o'n' 'for' Fut'u'r'e V/'S'TOL' 'Aircraft- 

Overview of Contents 



5.1. Introduction 

5.2. Notation 

5.3. Jet Interference In Hover Outside Ground Effect 
5.^. Jet Interference in Hover Close to the Ground 

5.5. Jet Interference in Transition for V/STOL Transport Air- 
craft with Jet Power Plants 

5.6. References 



Figures 

5.1. Alternative models for treatment of change In lift in 
Do 31 hover with cruising power plants only. 

5.2. Decrease in dynamic pressure along axis of Jet. Measure- 
ments taken from [2]. 

5.3. Change in thrust close to ground as a function of ratio /127 
of rectangular panel area to nozzle area. 

5.4. Change in lift close to ground, based on suction effect 
measurements . 

5.5. Jet interference measurements on a medium-range V/STOL 
airliner in hover close to ground, taken from [10], 

5.6. Change in thrust close to ground, fountain effect pre- 
dominating. Model measurements. 

5.7. Dropoff in max. velocity of upward flow between a pair 
of nozzles, from measurements taken from [7]. 

5.8. Change in shift close to ground. Do 31 and Do 131 
model measurements. Suction and fountain effects 
superimposed . 

5.9. Do 31: change in thrust in hover as a function of ground 
distance. All power plants on takeoff thrust. 

5.10. Stagnation points and stagnation lines in ground flow 
field during Do 31 vertical takeoff. 

5.11. BAG models and Do 31 models with lift arid lift /thrust 
power plants in transition. 



109 



5.12. Jet Interference for a rectangular wing, from measure- 
ments taken from [1] and [2]. 

5.13' Jet interference for a rectangular wing, from measure- 
ments in [1]. 

5.14. Do 31 jet Interference with cruising + thrust power 
plants. Comparison between measured and calculated 
values . 



110 



5.1. _Introduction /I 2 8 

So far, it Is not yef possible to determine the jet-Induced 
forces and torques of an aircraft configuration In closed form 
by theoretical means, due to the complex flow processes. 

Usable computational methods are available only for the 
simplest cases such as a panel with a central Jet In hover in and 
out of ground effect, as well as formulations for solving the 
problem In oncoming flow. In addition, a large number of measure- 
ments, primarily wind tunnel measurements, exist for a great 
variety of aircraft configurations and also for slmpllifled basic 
models. To be sure, the available measurement results are far 
from adequate for setting up empirical relations by means of which 
jet interference in hover and in flight, in and out of ground 
effect, can be determined for any aircraft configuration. 

Estimating jet interference for a new aircraft probject 
amounts to extrapolation on the basis of more or less well-known 
influencing factors, starting with a similar aircraft for which 
measurements have been taken. 

With a view toward future V/STOL transport aircraft, an 
attempt is made in the following to indicate the most important 
influencing factors on the basis of experience gained during Do 31 
development and through the evaluation of outside work, and to 
give the project engineer points of reference for estimating the 
Jet Interference effect. 

Unfortunately, studies could not be performed systematically 
enough during Do 31 development that all Influencing factors are 
known quantitatively. Suitable wind tunnel measurements cannot 
be dispensed with in a new project. 

5.2. Notation /129 

A ' Aerodynamic effect 

B, b Wing span 

Cp Pressure coefficient 

Da Diameter of thrust nozsle 

^e> ^ie Equivalent nozzle diameter 

F Area of aircraft planform 

Fj Area of thrust nozzle 

H, h Ground distance 

hpy Distance between landing gear and ground 



111 



o 

Poo 

q 

So 

X 

PJ 



Total pressure in thrust nozzle 

Ambient pressure 

Dynamic pressure In thrust jet 

Nozzle thrust 

Aircraft speed 

Initial velocity of jet 

Coordinate in direction of power plant axis 

Jet density 



5.3. Jet Interference in Hover Outside Ground Effect 



/1 30 



A power plant Jet exhausting from the underside of an air- 
frame causes a loss in lift. The lift loss is caused by the 
underpressure on the underside of the aircraft, which in turn Is 
produced by mixing of the '.turbulent power plant Jet with the sur- 
rounding air. Close to the ground, the jet interference effect 
can change both in magnitude and in sign, depending upon ground 
distance and aircraft configuration. The ground effect is treated 
below in Section 5.4. 

There have so far been a few dozen studies on the Jet Inter- 
ference effect on certain aircraft configurations. Systematic 
studies to determine the parameters are known only from [1] and 
[2], however; these, too, possess no general validity, since only 
fighter configurations are covered. In purely empirical terms, 
a relationship is found between lift loss, on the one hand, and, 
on the other, the ratio of the aircraft surface area F surrounding 
the Jet(s) to Jet area Fj , the drop in dynamic pressure along the 
axis of the jet, and the static pressure of the Jet: 



- 6S 



/3 ^ (X) 
• 1 3 t^ ) 



I 
P- 



3 max 



V 

, 1 



{^r''' 



(1) 



The significance of the second square root expression Is made 
clear by the following diagram: 



112 



3fiM ) 




/f- 



E^-ir 



P^ 9<x) 



For a fighter configuration with lift power plants mounted in /131 
the center section of the fuselage^ model measurements In [1] 
yielded the following for approximately critical discharge : 



p -0,64 



0.009 



A conspicuous feature in (1) is that the static pressure 
ratio for the jet appears as a parameter. If we look at the ex- 
tensive studies in [9] on free Jet propagation, for example, 
the effect of Mach number on jet propagation become s clear. 

The constant K In (1) is by no means universally applicable. 
It Is valid only if the configuration does not deviate too much 
from the arrangement under discussion. 

Considerable differences in the magnitude of K can occur 
between central and peripheral arrangements of jets. In particular, 
power plant pods with a series of lift power plants, which are 
often mounted outboard on the wings of VTOL transport aircraft, 
can result in a considerable reduction in jet-induced lift loss, 
since a relatively small wing area is located in the immediate 
vicinity of the jets. Thus in the case of the Do 31* the four 
power plants Installed In a pod at the wing tip caused about 
2.22^ lift loss, whereas the four nozzles of the Pegasus cruising 
power plants located inboard under the wing produced 3.6^ lift 
loss (referred to Inherent thrust). In both cases, jet area was 
approximately the same and jet propagation from each set of four 
nozzles was probably likewise about the same. 

The effect of the distribution of the area surrounding the 
jet will be covered in the following 'discussion. The force 
exerted on the underside of the aircraft Is expressed as follows: 



AS 



■\r. 



.is. 



"J^ 



m 



113 



where Cp is the local pressure coefficient on the underside of the /132 
aircraft. It Is now assumed that Cp decreases linearly with the 
reciprocal dlmensionless. distance from the center of the Jet, 



•p - r-7D. 



an assumption which proves to be reasonable, as will be shown 
below. 

For lift loss we thus obtain 



r Oj 



2tt 






d r d 



2fl 



J 2it 



(0) - D 



•^j/z ^' 



in] ^ ^ 



•v 



- 2 Kj /[r (G) - D, .j] d 



If we set 



It 



3 



3t 



I / Ir (0) - D^/jl d - 5 




then 



^ - - 2Ki 






C2) 



Here, Dj Is nozzle diameter, and D can be conceived of as the 
equivalent diameter of the aircraft's planform. 

For the special case of the round panel with a central jet, 
we can Integrate and obtain 



11^4 



^ - - 2K ^ 



J 



Where D is panel diameter. 

Converted to the ratio of areas, this becomes 



■ /1 3 3 



s 



1^ = - 2 Kj • If F . 



C3) 



The same relation exists in (1) and C3) between lift loss 
and area ratio, thus indicating the assumption regarding .the 
dependence of Cp to be reasonable. The constant K]_ is a function 
only of Jet characteristics, and these are taken into considera- 
tion in relation (1). Relation (1), expanded to cover any 
aircraft configuration, thus reads as follows: 



s_ 



= K 



U 

D, 



3 


*? ( 


x)l 


^o- 


•P- 


L^ 




' 



(5) 



/ 






-0,64 



C4) 



Like (1), relation (4) can only be used to convert lift loss 
from a known configuration to one which is somewhat similar, 
since the constant K does not possess general validity. 

The progress which (4) represents over (1) consists of the 
fact that deviations in the ' planform of the aircraft 
and in the arrangement of power plants can be covered. Example: 



Circular panel 



Quarter- c ircl e 





F = It R* 

j r dG « 2 Ti R 





F »» It R' 



2ir 

f r d© = It R 



115 



The circular panel and the quarter-circle of the same sur- /13^ 
face area F differ in size ^ 

j- r dG 
o 

by a factor of two. The same lift loss would be obtained from 
(1) for the two cases, whereas on the basis of (4), lift loss for 
the circular panel would be twice as large as that for the 
quarter-circle, which is reasonable. 

Unfortunately, no systematic measurements are available to 
demonstrate the usability of relation (4). An attempt will be 
made, however, to calculate lift loss with (1) and (4) in the 
example of the Do 31 lift power plants and the cruising power 
plants, oriented vertically in the downward direction, and to com- 
pare it with wind tunnel measurements. Although the configuration 
of the Do 31 differs considerably from that studied in [1], we 
shall adopt the value K x (Po/P»)"0-^^ = 0.009. 

The four Do 31 lift power plants, arranged in a line, and 
the four cruising power plant nozzles, arranged in a square, can 
be treated in relations (1) and (4) on the basis of three dif- 
ferent model representations; Pig. 5-1 provides an overview. 

Model I 

The four individual nozzles are treated as one normal 
nozzle of equivalent diameter, with the dynamic pressure drop 
of a normal nozzle. 

Model II 

The four individual nozzles are treated as a quadruple 
mixing nozzle of equivalent diameter with the dynamic pressure 
drop of a mixing nozzle. 

Model III 

The four individual nozzles are treated in isolation, 
each nozzle being surrounded by the entire aircraft surface 
and possessing the dynamic pressure drop of the individual 
nozzle. The overall effect is obtained by linear 
superposition. 



(4), 



116 



All three models are treated both with relation (1) and with /I 3 5 



Unfortunately, values for maximum dynamic pressure drop in 
the jet are not available, for Do 31 model measurements. Measure- 
ment results from Cl) [sic] are used here; these are plotted in 
Fig. 5.2. They are from measurements performed on a group of 
four which are arranged much like the Do 31 cruising power plants, 
In the case of the single nozzle, Dj represents the diameter of 
the single nozzle, whereas for the group of four, Dj corresponds 
to the equivalent diameter. 

The results for changes in lift determined in this manner 
are given in Pig. 5.1 and are repeated in the table below. 



CRUISING'POWER' PLANTS: r^LS/S^ IN % 





Model representation 
I II III 


Relation (1) 
(4) 


1.97 3.94 3.94 
1.68 3.36 3.36 



As already mentioned, the lift loss measured in the wind 
tunnel for the cruising power plants is - AS/Sq = 3.6^. 

The same approach was applied to the lift power plants. The 
table below shows the results of computation. 



LIFT POWER PLANTS: -AS/Sq IN % 





Model representation 
I II III 


Relation (1) 
(4) 


1.98 3.96 3.96 
1.2 2.4 2.4 



The lift loss measured in the wind tunnel for the lift power 
plants is -AS/Sq = 2.22%. Since the parameter K3 for the dynamic 
pressure drop in this case is exactly twice as large as for the 
individual nozzle, lift loss as indicated by equation (4) will be 
exactly identical in cases II and III and exactly half as large 
;in case I. 



/r36 



117 



Model representations II- and III yield good agreement with 
the wind tunnel measurements for the cruising power plants, as 
determined both with relation (1) and with (if), whereas only (4) 
yields good agreement for the lift power plants. This is 
reasonable J since the lift power plants have an extremely outboard 
position, where the considerations which led to relation (4) are 
quite applicable. Relation (4) can be recommended on the 
basis of these positive results. That model representation I 
greatly underestimates lift loss is clear and reasonable, since 
the equivalent individual noszle in I has completely different 
jet propagation from that associated with a group of four. 

Thus the use of model representation II or III can be re- 
commended for groups of nozzles. If the behavior of . the dynamic 
pressure drop is known, II is probably to be preferred, since the 
superposition principle used with III has not been validated. 

5.4. Jet Interference In Hover Close to the Ground 

In hover close to the ground, other changes in force and 
torque besides jet-induced secondary forces of free hover act 
upon the airframe. 

A single jet directed; perpendicularly or obliquely at the 
ground, or a line of Jets, is deflected at the ground and flows 
off in the form of a wall jet.- Like the free jet, the wall jet 
draws air from the surroundings and generates an underpressure on 
the underside of a panel perpendicular to the ground. When a 
pair of jets or pair of rows of jets is aimed at the ground, an 
upward current (fountain) develops between the pair which 
generates an overpressure on the underside of the panel. 

In an aircraft configuration with a particular power plant /I37 
arrangement, both effects, namely the suction effect and fountain 
effect, are superimposed on one another and affect each other. A 
theoretical solution is not yet possible for this complex 
process. We will first determine the approximate flow pattern, 
particularly stagnation points and lines of flow, from informa- 
tion on the individual effects and also on the basis of personal 
experience, and then attempt to also obtain quantitative informa- 
tion regarding secondary forces and torques by superimposing the 
individual effects. 

As a basis for this approach, an attempt will be made below 
to analyze the individual effects;- this is followed by the 
analysis of a complex configuration, using the example of the 
Do 31. 



118 



3.4.1. Analysis of Jet Interference Close to the Ground 

The process of Jet interference close to the ground can be 

analyzed in simplified form as shown below and broken down Into 
several basic configurations. 



H0KF1CURA1I0N 



a 



StttundOfkroH 



Etnlel St roM , 
von Ploltc 

umgeben S 




-<>- 



-J^ 



GfStlwflndiS'rtits- 
Obnohtv* <wt dfT 
Wonditronitinit G 
biw im Ayf slrxrn 



k 

Sougtllckt 



Strahlreihe 
od.&lrdhtspoU 
von Platte 
umgebcn 

h 



Elrohlrrihen- 
Poor mit do- 

gender PUrtte 

i 



t 

•o- 



Jl 



^B»: 



*«H^^^P»WIW 



I— A 



SoustHekt 



Uj 



K 

r/D, 



d SCHUBAUDHRUHG tt; BODttUAKE 



!;■ 



Su. 



L 




1 
Fontonen- 
eltekt 



U, ' lr/D,r 

tlweidirncri»i)no<.) 



Strohl-Poor 

mi datwi- 
ichenliest"' 
der Plotte . 

ij 



Sougetfekt 

u.Fonlbntn 
tff«kt 

k + U 



H/poltitse: n 
K 



U/0,) 



T7T 



Urn.. 

(iwcidimenvonaO 

m 



Q.012 ( 



H/Oi 



a994iF;F,r-i 



^f 







^ 


H/D, 


•^ ff ^ 


<?^ 


SS=- 


^«.« 


?>><'' 






i 


f 







Kypotheje. ri 



AS 



h/0, 



(iwtidimensionol) 

m 




-*h^, 






— fc H/D, 



Key: 



Reproduced from 
bes> available copy. 

a. Configuration 

b. Cause of secondary force 

c. Velocity drop along wall flow line or 
in upward flow 

d. Change in thrust close to ground 

e. Analytical relation 

f. Qualitative curve (s) 

g. Individual jet, surrounded by panel 

h. Row of Jets or -'slotted jet surrounded by 

panel 
i. Two rows of Jets with panel between them 
J. Two Jets with panel between them 
k. Section effect 
1. Fountain effect 
m .Two-dimensional 
n. Hypothesis 



119 




a> Individual jet exhausting normally from a panel and oriented 
normally with respect to the ground 

A jet exhausting from a nozzle Is propagated In accordance 
with the known empirical principles governing free jet propaga- 
tion and, after deflection at the ground. In accordance with 
those governing wall Jet propagation. The region close to the _ 
stagnation point, with a radius of ahout one nozzle diameter. Is 
excluded here. The drop In the characteristic velocity of the 
free or wall Jet occurs linearly with distance from the nozzle or 
stagnation point, respectively. The decrease in maximum velocity 
In the wall jet Is governed by the propagation law 

K 
' r/D. ' 



In which the nozzle's distance from the ground does not appear. 
The constant K has various values in the literature. The reason 
for this lies primarily In the different initial conditions in the 
nozzle. 

The natural flow toward the free or wall jet is obstructed in 
the case of a jet exhausting from a panel parallel to the ground. 
The surrounding air is sucked in along the underside from the 
margin of the panel and produces an underpressure. If the panel 
is very large or the distance between nozzle and ground is very 
small (H/Dj < 1), this flow pattern no longer applies. This case 
Is of no practical Interest, however. 

The underpressure on the underside of the panel and thus the 
total force acting upon the panel can be calculated with the aid 
of potential theory If assumptions are made regarding the air 
sucked in by the free and wall jets. In Seibold [10], the Jets 
are represented here by coverage with sinks, the panel by coverage 
with vortices, and the ground by reflection. The comparison 
between calculations and measurements is unfortunately shown only 
to a ground distance of H/Dj < 0.5 in [10]. 

In [11], an empirical relation, obtained from measurements 
with circular panels of various size, is given between relative 
thrust loss and ground distance, which is made dlmenslonless with 
the difference between, panel diameter and nozzle diameter. 

/ 



120 



The reference quantity on the right side, which can be con- 
ceived of as the equivalent diameter .of the panel area surrounding 
the nozzle i ',1s interesting and is physically meaningful. Panel 
area and nozzle area are thereby eliminated as independent 
variables. This relation is also applicable to configurations 
with fan power plants, for which the ratio of nozzle area to 
panel area is an order of magnitude larger than in the case of jet 
configurations. It is suggested that in the case of noncircular 
panels, panel diameter Dp be replaced with an equivalent^ diameter 
Dp in analogy to the considerations discussed in Section 5.3- 

A likewise empirical relation, almost identical to (4a), is 
given in [4]: 



s. 



H/D. 



S = J\=.1 - 0,012 ^ ; — -rjZ 

Sjj S^ L 0.994 (F/Pj) ^' -1 



, -2.3 



(4b) 



Expression (4b) differs from (4a) by a factor of only 0.994 
in the case of the circular panel. Relation (4b) is handier for 
first approximations than (4a) and is shown in Pig. 5-3 as a 
working graph. A comparison between (4b) and measurements per- 
formed on various rectangular panels in Pig. 5.4 shows 
acceptable agreement for project estimates. 

b) Row of Jets or slotted jet, exhausting from a panel and 
oriented perpendicular to the ground 

A notable feature in Pig. 5.4 is that a slot noszle with 
an aspect ratio of about 9 generates a smaller secondary force than 
a round nozzle of equal area. The difference is in the different /l40 
propagation laws governing the three-dimensional single jet and 
the quasi-two-dimensional slotted jet. As already mentioned, the^ 
linear propagation law applies to the round Jet for velocity: 



V t . 

max _ K \ , 

whereas the square-root law applies to the two-dimensional case 

V 

iTax _ K 






121 



It is reasonable to formulate relation '(^1^:) as follows for 
the two-dimensional case: 

c) Two rows of Jets with panel between them 

In the case of two rows of Jets or two slotted Jets oriented 
perpendicular to the ground, a stagnation line is generated in the 
plane of symmetry above which the wall Jets coming from opposite 
directions proceed in the form of an upward vertical current. A 
body lying transverse to this upward current experiences a force 
in the direction of oncoming flow similar to the drag of the 
particular body in a free stream. 

Now the drag of various bodies differs considerably. An 
infinitely long circular cylinder has a coefficient of drag of 
about 0.4 at a Reynolds number greater than 5*105, whereas an 
infinitely long panel in perpendicular oncoming flow has a coeffi- 
cient of about 2.0. Just this numerical comparison is enough -to 
show how problematic it is to estimate the force acting on the /l^l 
body of an aircraft located in an upward flow with all possible 
flaps extended for takeoff. 

Due to the same facts, on the other hand. Influence can be 
exerted by relatively simple means, such as auxiliary flaps. An 
example of this is provided by the measurements from [10] shown 
in Fig. 5-5, obtained with a medium-range V/STOL airliner. 

In Fig. 5.6, the thrust acting upon the aircraft close to the 
ground is plotted against ground distance. Reference quantities 
include operant thrust out of ground effect and the diameter of a > ^ 
single nozzle. The curves came from measurements performed on 
the Do 31 and its successor, the Do 131- The measurements confirm 
the predominance of the fountain effect, which is reasonable on the 
basis of the arrangement of Jets and the planform. 

It is conspicuous that the curve for the Do 31 lies consider- 
ably below that for the Do 131- Various factors play a part here, 
such as different Inclinations of the .power plant Jets and dif- 
ferent fuselage shapes, including extended landing gear doors, 
and the like. The inflection point for the Do 131 is conspicuous. 

For the two rows of Jets or two slotted Jets oriented per- 
pendicular to the ground, the same propagation laws apply, in 
qualitative terms, as in the case of the free and wall Jets of the 
corresponding individual configurations up to about the point at 



122 



which the wall jets form a stagnation line. In the vicinity of the 
stagnation line, the wall Jets parallel to the ground are deflected 
into a vertically rising fountain. If secondary factors are 
neglected, the fountain can be viewed as a continuation of the 
wall Jets. The plane of symmetry takes the place of.'the wall here. 
Just as a propagation law which is independent of nozzle height 
applies to the wall, Jet, an analogous propagation law which is 
independent of nozzle height H and nozzle separation A can be 
derived for the fountain. 

J [sic] 

In analogy to the linear law governing the drop in velocity, 
the following would apply to the fountain between a pair of 
nozzles : 

V V 

i [sic] 

Measurements of maximum upward flow velocity along the axis 
of symmetry of a pair of nozzles presented in [7] confirm, to a 
certain extent, the linear relationship and the subordinate 
effect of nozzle separation A beyond a ground distance of 
Z/Dj > 3 (Fig. 5.7). 

The discussion of principles presented here applies only if 
the distance between the pair of Jets is not too small compared 
to ground distance. In this case, the two free Jets merge^even 
before they impinge on the ground and thus obstruct the development 
of a fountain. S. Harmsen [8] shows this effect very clearly by 
means of momentum measurements between a pair of nozzles and by 
means of flow pictures taken by the light section method and finds 
that no fountain occurs between a pair of nozzles if the distance 
between them is not at least one or two times the distance between 
the nozzles and the ground. 

The following can be written formally for the aerodynamic 
force on a body located in the upward flow: 

^S = c^-q^-P 

or, referred to nozzle thrust,. 



123 



is „ 1 ^ . £ . t !^ 

s; 2 ""w p^ ^i ' ^ C6) 

where v^ is mean velocity in fountain, c^^ is the body's coeffl- /1^3 
clent of drag, F is the aircraft qirea which, is -located in the 
upward flow. The density effect is of subordinate importance in 
jet propagation and is neglected. 

For Vm, we assume Vj^ = ^'^xaaxy ^'^^ ^^ ^^^ ^^^ distance of the 
underside of the fuselage from the ground be Z = h, whereupon 
we obtain the following relation with (5) and (6) 

In Fig. 5.6, measured Jet-induced force is plotted against 
ground distance for the Do 31 and Do 131 with the cruising power 
plants in two rows of nozzles each. The linear relation is valid 
in terms of trend. The different levels of the curves can be 
explained by the different shapes and sizes of the fuselage under- 
sides. 

d) Two Jets with panel between them 

The flow pattern in case d) is a mixture of case a) and case 
b) and is therefore difficult to determine even qualitatively. 
As in case c), a stagnation line does develop at the ground, in 
one of the planes of symmetry. A vertical fountain is formed^only 
near the axis of symmetry, however. The fountain flows off to the 
side over the; remainder of the ground stagnation line. Thus the 
fountain effect is operant only In the vicinity of the axis of 
symmetry, whereas the suction effect prevails over the rest of the 
panel. Fig. 5.8 shows model measurements of the change in thrust, 
close to the ground, on the Do 31 and Do 131 with Just the cruising 
power plants running. The configuration of the Do 131 corresponds 
roughly to the case under consideration, whereas a fountain effect 
clearly occurs at low altitude in the case of the Do 31. 

5.^.2. Application of the Analysis in 5.^.1 to the Example of the 
Do 31 

The most important features relating to Jet interference in 
hover close to the ground are as follows for the case of the Do 31: 



124 



high-wing configuration 

lift power plants at wing tips 

cruising power plants inboard under wing. 

First, the jet interference associated with the different 
groups of power plants Is estimated separately. The lift power 
plants of the Do 31 contribute little to the change in thrust, due 
to their peripheral location. The lift loss due to the suction 
effect outside of the ground effect is only about 1% of overall 
takeoff thrust. Even close to the ground, no appreciable addi- 
tional suction effect or fountain effect occurs because of the high-^ 
wing configuration and the peripheral location. These statements 
agree with the model measurements plotted in Pig. 5>9. Only at a 
landing gear to ground distance of less than 2 A (hp^f/Dj ) does a 
weak fountain effect become operant. 

The cruising power plants of the Do 31 produce a thrust loss 
of 2% of overall takeoff thrust outside the iground effect. Close 
to the ground, the cruising power plants represent a mixture of 
cases c) and d) as treated in Section 5.3-2, for which reason their 
Jet interference effect can only be estimated quite roughly. The 
model measurements in Pig. 5.9 show that a slight suction effect 
exists between values of li/^eWFvl ~ 7 and 1. 

Next, the ranges of influence of the lift and cruising power 
plants under takeoff and landing dondltlons are delimited, for 
which purpose we estimate the ground stagnation lines. In the 
case of the Do 31, the ground stagnation lines are available from 
flow patterns taken in model measurements (Pig. 5.10). It can be 
seen from the ground stagnation lines that the range of Influence 
of the lift power plants is markedly limited close to the ground.l 
The one appreciable contribution from the lift power plants comes 
from the stagnation line between the lift and cruising power plants. 

This stagnation line causes the deflection of a large portion of 
the cruising power plant J)ets in the direction of the fuselage 
underside. The effects of the cruising power plants are thereby 
enhanced: instead of 360°, the central angle of jet propagation 
amounts to only about 220°, so we must expect the effect to be 
increased by a factor of 1.64. The fountain rising above the 
ground stagnation line between the lift and cruising power plants 
is directed against the underside of the wing. Since the distance 71^5 
between ground and underside of the wing is already 10 Djjtw (in- 
dividual nozsle) with the aircraft standing on the ground, the 
fountain effect is neglected. 

The addition of lift and cruising power plant thrusts outside 
the ground effect and the 1.64-fold change in cruising power plant 
thrust close to the ground yields the curve of thrust versus ground 
distaxice plotted in Fig. 5.9. The : curve, obtained by superposition, 
lies below the measured value but provides a satisfactory ^picture 
of the distribution and order of magnitude of the jet interference 
effect. 

125 



5.5. Jet Interference' in Transition for' V/STOL Transport Aircraft 
tfit'Il Jef power Plants ■ 

For V/STOL aircraft with pure jet power plants or with fan 
power lilants of low bypass ratio (less than 1), the effect on 
aircraft aerodynamics caused by the power plant ; Jets far exceeds 
the effect of inlet flow. This applies particularly to lift, 
while the drag component of inlet flow is known from inlet 
momentum, and the torque component can likewise be estimated from 
the momentum vector of inlet flow. But the effect of the Jets 
can be treated separately from that of inlet flow for a first 
approximation of interference for aircraft configuration s'./with fan 
power plants of high bypass ratio, too, so the following statements 
also apply to these cases. 

In hover. Jet interference from a nozzle Jet is based only on 
its suction effect due to turbulent mixing of the Jet with sur- 
rounding air. In transition, an interaction occurs between oncoming _ 
flow and the power plant Jet, which in turn affects flow about 
the airframe. The resulting flow field Is of a complex nature, 
and only a few simplifying model representations are known so far 
for theoretically treating quite simple configurations such as /1^6 
that of a simple Jet in a wing, exhausting downward. Calculations 
and measurements exhibit satisfactory agreement in this case 
[12-14]. Two nozzle Jets positioned behind one another are 
covered in [15]. These model representations do not apply to Jet 
positions close to the wing forward edge or trailing edge or close 
to the extended landing flap, under the wing or in the fuselage as 
they occur in V/STOL transport aircraft, so we must rely entirely 
upon measurements. 

The Jet interference forces on V/STOL transport aircraft known 
from the literature and from our own measurements are reported in 
the following section. An attempt is made in a subsequent section 
to apply the interferences known from systematic measurements on 
single nozzles to the Do 31 configuration by superposition and to 
compare these with our own wind tunnel measurements. 

5.5.1. Determination of Jet Interference from Wind Tunnel 
Measurements 

In order to be able to convert from a configuration knownr 
from measurements to a new one, we must know the influencing fac- 
tors. As was already shown in the introduction, no such function 
is known for the general case. But no exact conversion function 
Is even known for the ;special case of geometric similarity in the 
planform and''iBlmilarit.y. in pAwer jt.lant nozzle position, but with 
a different ratio of nozzle area to planform area. Williams [I6] 
presents a conversion function: 






1/2 „ ... Vi 



J 

126 



- Function [(^) (''"^''j^j '] 



which is obtained from a dimensional analysis of the Jet propaga- 
tion process and the long-range effect of the jet deflection 
process, approximated with a vortex model. Since this simplified 
model representation no longer applies to complex configurations 
such as those of V/STOL transport aircraft, as mentioned in the 
Introduction, the conversion function derived from this Is like- /li7 
wise very questionable. Since nothing better is known, however, 
we will still have recourse to this formula in case of need, if 
Jet Interference affecting a new configuration must be estimated 
with the aid of the measured data for representative V/STOL 
transport aircraft compiled below. 

Jet Interference measurements performed on V/STOL transport 
aircraft are quite sparse. Most of the published jet interference 
measurements cover aircraft which can be classified as combat 
aircraft on the basis of configuration and arrangement of jets. 
Williams [l6] offers an excellent summary of the most Important 
measured data, including an extensive bibliography. V/STOL jet 
transport aircraft with such typical characteristics as high- 
wing configuration, large aspect ratio, large fuselage diameter 
and a relatively large number of lift power plants (at least 
eight) arranged in rows or groups of jets have only been studied 
by the British Aircraft Corporation (BAG) with a simple variation 
model. Aside from our own measurements with the Do 31 model, we 
know of no additional measurements. 

Pig. 5.11 shows a compilation of the BAG measurements 
(taken from [l6]) and the Dornler measurements, with lift re- 
ferred to static thrust, plotted over effective velocity ratio. ^ 

Configuration A., with the lift power plants mounted out- 
board on the wings, exhibits the smallest lift loss. Rows of 
lift power plants on the sides of the fuselage (configuration B) 
are enough to cause more than 10% loss, and the configuration of 
the Do 31, with lift power plant pods mounted outboard on the 
wings and the pivoting nozzles of the cruising power plants 
located inboard, likewise causes up to 10% lift losses. Very 
high losses are produced by rows of lift power plants in the 
central section of the fuselage (configuration C) or inboard on 
double delta wings (configurations D and E). In an extremely 
unfavorable case, more than 50% of static thrust can be lost. 
A comparison of the Various configurations lets us state, in 
qualitative terms, that loss Increases with the area surrounding 
the jets. 

In hover, lift loss is proportional to the square root of the /iH 8 
area ratio. This simple relationship does not apply in transi- 
tion, since the aircraft surface area surrounding the Jet makes 
a variable contribution to Jet-induced force,' depending upon its 
position relative to the direction of oncoming flow. 



127 



Nothing is known from tti.e BAC models rega,raing momentum 

change due to the '^et effect. - The torque curve of the Do 31 was 

covered In Section 3- Additional Information can unfortunately 
not tie provided. 

5.5.2. Superposition. of -Jet : Interference from TndlVldUal Jets 
" m the Example of the' Vd 31 

Since good results were obtained In Section- 5.3 In the deter- 
mination of jet interference in hover through superposition of the 
effects of Individual nozzles in the example of the Do 31, this 
principle will te checked In transition flight. For Jet-induced 
force in hover. It was possible to state an empirical relationship 
to geometric dimensions and the decrease In dynamic pressure along 
the axis of the jet. As was already established in the Introduc- 
tion, this Is not possible for the general case of the individual 
jet in transition, so we must have recourse to measurements per- 
formed on a basic model with a single jet. Such measurements are 
known from [17] and [I8], in which the position of the single 
nozzle in a rectangular wing was varied systematically. 

A prerequisite for fruitful superposition is that geometric 
conditions be approximately equivalent with regard to the position 
and size of the jet on the basic model and on the aircraft and that 
the reciprocal effects of the individual jets remain relatively 
small. By chance, the first condition is satisfied approximately 
for the lift and cruising power plants of the Do 31 In [6], while 
the second condition is probably not adequately satisfied by the 
nozzle jets, which are located close beside or behind one another 
in the case of the Do 31 under consideration. Only the results 
at the end of the following discussion will provide some 
information. 

The jet-Induced forces and torques on a rectangular wing with /IH9 
a single nozzle are studied systematically In the wind tunnel in 
[17] and [18]. In [17], the single nozzle lies in the plane of 
symmetry of a rectangular wing of aspect ratio 5 at a distance of 
zd/H = -0.25 under the plane of the wing. The forward or rearward 
position of the nozzle lies between -0.5 < xd/JI<< +Q.75 (zero 
point at 1/4 £ positive to the rear), the jet exhausting vertically, 
in the downward direction, among other things. The configuration 
of the wind tunnel model In [I8] consists of a wing/fuselage 
combination, rectangular wing of aspect ratio 4.6, with a single 
nozzle under each half of the wing separated by 1/4 of the span. 
Among other things, the forward or rearward positions were varied 
between -2.25 < Xp/Jl < +1.0 for nozzle le.vels (In terms of height) of 
z^/i = -0.64 and -0.84, with the jets exhausting vertically, in 
the downward direction. The data plotted in Fig. 5-12 are supposed 
to Indicate the effect. of the nozzles' forward position upon jet- 
induced force, with the nozzles' position on the vertical axis and 
the velocity ratio as parameters. 

128 



While the effect is approximately constant, for a nozzle loca- 
tion in the forward portion of the wing, the .^^jet flap effect" 
occurs if the nozzle is located to the rear, causing a positive 
component In Jet-induced lift due to superclrculation effects. 
The position of the nozzle along, the vertical axis influences both 
the magnitude of the interference and the rise In the curves due 
to the Jet flap effect. It must be mentioned, however, that the 
curves for zd/1 = -0.64 and -0.89. come from [l8], in which a wing 
with a single 30^ split flap at an angle of 60° was used. The 
crossover plot in Fig. 5.12 shows no reasonable trend for the 
effect of nozzle location along the vertical axis, for which reason 
the results in [17] are used for the application of superposition 
to the Do 31. The positions of the cruising and lift power plant 
nozzles of the Do 31 along the vertical lie in the range 
-0.3 < z^/l < -0.4, whereas z-^/i = -0.25 in [17]. The ratio of 
the area of individual cruising power plant nozzles to the area of 
the half wing lying outside the fuselage is Fj/F = 1/133, whereas 
Fj/F = 1/145 in [17]. The ratio of the area of individual 
cruising power plant nozzles to the area of the outboard wing up 
to the cruising power plant side wall is Fj/F = 1/65- Since the 
lift power plants at the wing tip of the Do 31 can be assumed to 
be lying in the plane of symmetry of a rectangular wing, the ef- /150 
fective area ratio is Fj/F = 130 [sic], and is thus a value which 
is applicable to [17]. The ratio of diameter to chord is 
probably just as important as the area ratio. This ratio is 
Dj/L = 5.7 in [17], while in the case of the Do 31, Dj/Jl =5-7 
for the lift power plants and Dj/£ =7-7 for the cruising power 
plants. 

Superposition is based on Fig. 5.13, which is an extension 
of Fig. 5.12 to Vb/Vj = 0.77. Superposition was applied only to 
the cruising power plants in one case and, in another, to the 
lift and cruising power plants, since comparable wind tunnel 
measurements were available for this. The results of superposition 
are shown in Fig, 5.14. The calculations agree satisfactorily with 
the measurements for low V«>/Vj , from about 0.1 to 0.15, while the 
calculated values are almost twice as large as the measurements for 
large Voo/Vj . 

The mutual interaction or obstruction of the propagation of 
individual Jets in the group of nozzles is probably being mani- 
fested here. The superposition of pitch torque is not possible, 
since the curves in [17] are too discontinuous and contain too 
few data points. " 

In summary, it can be said that for complex power plant con- 
figurations with rows and groups of jets such as in the Do 31, 
the principle of superimposing the effects of individual nozzles 
yields usable values for first approximations only in the case of 
a small velocity ratio, up to about V„/Vj =' 0.15. Systematic 
measurements on basic mo.dels with rows and groups of Jets are 
necessary to permit the preparation of generally valid working 
data for the project engineer. 

129 



5.6. REFERENCES 

1. aentry, G, L, and Margason, R. J., "Jet-induced lift losses /I 51 

on VTOL configurations hovering in and out of ground 
effect," NASA TN D-3166, I966. 

2. Shumpert, P. K. and Tibbetts, J, G., "Model tests of jet- 

Induced lift effects on a VTOL aircraft In hover," 
NASA CR-1297, 1969. 

3. Vogler, R. D., "Interference effects of single and multiple 

round or slotted jets on a VTOL model In transition," 
NASA TN D-2380, 196^. 

4. Hall, G. R., "Scaling of VTOL aerodynamic suckdown forces," 

J. Aircraft 4(4) (I967). 

5. Esch, P. and Joos, R., "Do 31 2B interference and ground 

effect measurements in the DW wind tunnel," Dornler 
Report VW 537-Bl. 

6. Esch, P. and Bartalszky, H., "Do P-362 Interference measure- 

ments in the DW wind tunnel," Dornier Report VT 483-Bl. 

7. Hoscher et al., "Systematic studies of free jets, ground /152 

jets and hot gas fountains for VTOL configurations with 
jet power plants, lift fans and propellers," Dornier 
Report VT 483-B5, 1969- 

8. Harmsen, S., "Experimental studies on the upward flow caused 

by two lift jets .close to the ground," Engineering 
University of Berlin Report on Aircraft Construction 54/8. 

9. Warren, W. R., An Analytical and Experimental Study of 

Compressible Free Jets , University of Prlncetown [sic] , 
New Jersey, 1957- 

10. Seibold, W., "Studies on the secondary forces generated by 

lift jets on VTOL aircraft," Jahrbuch d. WGLR [Yearbook 
of the Scientific Association for Aeronautics and 
Astronautics], I962. 

11. Wyatt, L. A., "Static tests of ground effect on planforms 

fitted with centrally located round lifting jets," 
ARC CP No. 749, 1964. 

12. Bradbury, L.J.S, and Wood, M,, N., "The static pressure 

distribution around a circular jet exhausting normally 
from a plane wall into an axr stream," ARC CP 827, 1964. 



130 



13. Wooler, P, T., "On the, flow past a circular Jet exhausting 

at rlgtit angles from a flat plate, or wing,": 'J'.' Roy.' Aer. 
Soc . '71 CMarch 196? )» 

14. Wooler, P, T., Burghart , G. H. and Gallagher, J. T,, /153 

"Pressure dlstrxhutlon on a rectangular vring with a jet 
exhausting normally Into an alrstream," J.' Aircraft 
4(6) C1967). 

15. Ziegler, H. and Wooler, ■?. T. , "Multiple jets exhausting Into 

a crossflovf."' jr.' Alrcraff 8(6) (1967). 

16. Williams, J,, "The aerodynamics of V/STOL aircraft. Part E: 

Turbo jet/turbofan aircraft," Von Karman Institute for 
Fluid Dynamics Lecture Series 9, May 13-17, 1968. 

17. Baumert, W. and Harms, L. , "Effect of a nozzle Jet on the 

aerodynamic coefficients of wings located above the Jet 

nozzle," DGLR Report 70-28, Report on the Symposium on 

Aerodynamic Interference Between Aircraft and Power Plant 
Jet, Dusseldorf, Dec. 3, 1970. 

18. Carter, A. W., "Effects of jet-exhaust location on. the 

longitudinal aerodynamic characteristics of a jet V/STOL 
model," NASA TN D-5333, 1969 . 



131 



F/2 » 1630,7 cm Fj « 3.04cm' 

Of/1 " 36.7 cm Dj = 2.21. cm 



* Data on. wind 

tunnel model 



Case 



Model 
representa- 
tion 



H 



12 



31 





Change in j,^^^^^, 



0.0Q9 
~5~ 



^s, IW 







0009 ,, 



f F/2 

4 IJ-TT 



Ks 



as/So 



0.2125 



0.425 



OJD09 



/ F/2 
KSi 1^ — pp 



QDQ9 



2^ KSi "i^ 



cii 



/I 



w 



0-2125 



0.0197 



0.0394 



00334 



a2125 



0009 ., Ova 



"3oa uya 

2 Ks4 -|5|- 



0009 Ksi ^^ 



0.425 



Q2125 



QD168 



00336 



a0335 



/15^ 



Fig- 5'1« Alternative models for treatment of the 
change in lift in Do 31 hover with crui sin© -power 
plants only. 



132 



Quadruple noZ' 
zle for 
measurements 



r 



/155 




Do 31 

Cruising "T" 
nozzle e 



4 



ft-SO— *-| 

4 ^ 



Parameters for Jet Propagation: 



Ks • 



d 


<tfx) 1 

p.-p- 


d( 


x/Dj,) 



1 



a «* 



mox 



Ix/Di*), 



Quadruple 
nozzle 



Kst 



V"2l 



1 



232 2^6 



- 0.425 



Single 
nozzle 



Ks, • y- Ks* • a2125 



Fig. 5.2. Decrease in dynamic pressure along 
axis of jet. Measurements taken from [2]. 



133 




/156 



Fig. 5.3. Change In thrust close to ground as a 
function of ratio of rectangular panel area to 
nozzle area. 



134 



Hp/Dj, 7^5 




/157 



IS \ 

Hp » panel-to-ground distance 



Pig. 5.4. Change in lift close to ground, based 
on suction effect measurements. 



135 



AS. 
s. 

oat 



-ojo; 



V4 'l* 








Ah t 








1 

t 
1 








1 

4 








Va **<i. 


^£^ 


I 



0( 



01 



H/b 



Secondary 
<Sovce 



AS 






\ 



a — - mit a 

Abreinkonten 

A ohne 






000] 

Mx/SJb/21 

oow 

CC01 



-^ 



mit a 

Abreiflkanten 
ohne 



Rollmoovtnt i»t b 
dtftoIiiLttiertnd 



C • 10 



(1(31 S 



Ojoio 



dOOS 



■6.00S 















f 




.0 


















L 


/ 


t 










/ 












7 












kiJ^ 


^■i 


-.A^ 


L 




^■^ 


W¥ 




-ftrwri 

















01 ox ce 



M 10 

H/b 



Roll torque M^^ of aircraft 
In horizontal hover at al- 
titude h = 14.4% of span b. 



Pitch torque My of 
aircraft In horizontal 
hover . 



Fig. 5.5. Jet Interference measurements on a medium- 
range V/STOL airliner in hover close to ground, 
taken from [10]. 

Key: a. With, without spoilers 

b. Roll torque is destabilizing 



136 




Do 31 



ru^ 



''PP7<:7'^''7^^/A/r/?j7777y7J'jr;^, 



Do 131 




',v///A '/:> ' / rA^//7:7?A^ 



/159 






Pig. "0,^, Change In thrust close to ground, fountain effect predominating. 
Model measurements. 

Key: a. Only lift power plants operating; b. Ground -r to - fuselage 
underside distance; c. Diameter of individual lift power plant 
nozzle 



CD 



/160 




Fig. 5-7- Dropoff in max. velocity of upward flow between a 
pair of nozzles, from measurements taken from [7]. 



Key: a. Max. velocity of upward flow 
Id . Ground distance 



/161 



1.00 r-V 



^r/Omtw 10.0 



t25 



Sh>c 



OSS 



OSO 




Fig. 5,8. Change in shift close to ground. Do 31 and Do 131 model 

measurements. Suction and fountain effects superimposed. 

Key: a. Equivalent diameter of the two cruising power plants 

b. Only cruising power plants operating 






/162 



XT 

o 



^Ja 



18 20 



2_ 



0.9a 



0.9 S 



094 



as 2 




hpY/ ~ Landing gear - to - 
ground distance 

DmtW = Equivalent diameter of 
the two cruising power 
plants 



^ges 



= Takeoff thrust of all 
power plants 



Fig. 5.9. Do 31- change In thrust In hover as a function of ground 
distance. All power plants on takeoff thrust. 8= 0°. Cruising 
power plant nozzle angle t = 90°/ 

Key: a. Lift power plant measurements 

b. Cruising power plant measurements 

c. Modified superposition of lift + cruising power plants 

d. Lift + cruising power plant measurements 



7163 




Pig. 5.10. Stagnation points and stagnation 
lines In ground flow field during Do 31 
vertical takeoff. 



I4l 



/164 



A. 



4 



T 



Z3B 



c 



1 



Do 31 



• • • • ^7 r« 

. . . . _^ ■- 





0.1 



a2 



0.3 



Pig. 5.11. BAG models and Do 31 model with lift 
and lift/thrust power plants in transition. 



1^2 



/l65 



S„ 



a2- 



0.1 



-Q2S 



^-"0.lf-y^ 






-0.2 




V. /Vj . 



'- 0.22 
-- O.tS 



\l/_ 



M] 



^=a=^ 



C2J 



Zp/l « -0.25 



Zp/l « -0.54 / -0.89 



Fig. 5.12. Jet Interference for a rectangular 
wingj from measurements taken from [1] and [2]. 



143 



/166 




Fig. 5 .IS. Jet interference for a rectangular wing, 
from measurements In [1]. 



144 



/167 




Ses 



a25 



aso 



(v«/vj )^ 



0.7 £ 



Fig. 5.1^. Do 31 jet Interference with cruising + 
thrust power plants. Comparison between measured 
and calculated values. 



IH5 



6 . Summary /I 6 8 

This report contains all of the know-how associated with the 
problems that were solved In connection with jet Interference during 
the development and testing of the Do 31 V/STOL transport aircraft. 
The most Important results of model measurements, covering the 
complete V/STOL. flight profile, are presented. From 1 to ^^ lift 
loss was measured In hover; this Increases to a maximum of 8% close 
to the ground. Jet-Induced torques are not appreciable. In 
transition, the change in normal force can amount to as much as 12^ 
of gross thrust, and the Jet-Induced tall-heavy torque requires up 
to 50% of available pitch control torque for compensation under the 
most unfavorable conditions. 

The various model method were critically evaluated. The 
relatively simple principle of simulating power plant jets by the 
discharge of compressed air has proven itself in the case of the 
Do 31 and can also be recommended for future V/STOL development for 
measurements without forward speed. Due to the relatively high 
inlet momentum of up-to-date lift fans, both the thrust Jet and 
inlet flow should be simulated for future V/STOL aircraft in Jet 
interference measurements in transition flight. 

A series of VTOL transitions by the Do 31 E3 test aircraft 
are analyzed with respect to Jet-induced forces and torques. The 
data stored on magnetic tape are evaluated with a computer program. 
More than 120 measurement points had to be interrogated at a 
frequency of 5 Hz. The precision required for jet interference 
evaluations cannot always be satisfied, particularly In the measure- 
ment of thrusts. Nevertheless, the agreement between model and 
flight measurements is satisfactory, and It was possible to confirm 
the model principles which were applied. 

The one known semiempirical method for calculating jet-induced /169 
normal force in hover Is extended to complex configurations. ^such 
as the Do 31. Points of reference are given for estimating jet 
Interference close to the ground and in transition for future 
V/STOL aircraft. Model measurements cannot be dispensed with in 
the future, either. 



146