An investigation of a 1/18-scale dynamically similar model of the North American B-45 airplane was made to observe the ditching behavior and determine the proper landing technique to be used in an emergency water landing. Various conditions of damage were simulated to determine the behavior which probably would occur in a full-scale ditching. The behavior of the model was determined from high-speed motion-picture records, time-history acceleration records, and visual observations. It was concluded that the airplane should be ditched at the maximum nose-high attitude with the landing flaps full down for minimum landing speed. During the ditching, the nose-wheel and bomb-bay doors probably will be torn away and the rear of the fuselage flooded. A violent dive will very likely occur. Longitudinal decelerations of approximately 5g and vertical accelerations of approximately -6g (including gravity) will be experienced near the pilots' compartment. Ditching braces installed in the bomb bay will tend to improve the behavior slightly but will be torn away along with the bomb-bay doors. A hydroflap installed ahead of the nose-wheel doors will eliminate the dive and failure of the nose-wheel doors, and substantially reduce the motions and accelerations

Fisher, Lloyd J.

Thompson, William C.

NASA Technical Reports Server

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NACA RM SL9L22a 
NATIONAL ADVISORY C O M M I T m  FOR AERONAUTICS 
RESEARCH MEMORANDUM 
fo r  the 
Air Materiel Command, U. S. A i r  Force 
DITCHING INlrESTIGATION OF A &-SCU MODEL 
OF THi3 NORTH AMEXICAN B-45 AIRPLP;NE 
By Lloyd J. Fisher and ~illi& C. Thompson 
SUMMARY 
An investigation of a scale dynamically similar model of the x- 
North American B-45 airplane was. made t o  observe the ditching behavior 
and determine the proper landing technique t o  be used i n  an emergency 
water landing. Various conditions of damage were simulated t o  deter- 
mine the behavior which probably would occur i n  a fu l l - sca le  ditching. 
The behavior of the model was determined from high-speed motion-picture 
records, time-history acceleration records, and visual observations. 
It was concluded tha t  the airplane should be ditched a t  the 
maximum nose-high a t t i tude  with the landing f laps  f u l l  down fo r  minimum 
landing speed. During the ditching, the nose-wheel and bomb-bay doors 
probably w i l l  be torn  away and the rear  of the fuselage flooded. A 
violent dive w i l l  very l i k e l y  occur. Longitudinal decelerations of 
approximately 5g and ve r t i ca l  accelerations of approximately -6g 
(including gravity) w i l l  be experienced near the p i l o t s '  compartment. 
Ditching braces ins ta l led  i n  the  bomb bay w i l l  tend t o  improve the 
behavior s l igh t ly  but w i l l  be torn  away along with the bomb-bay doors. 
A hydroflap ins ta l led  ahead of the nose-wheel doors w i l l  eliminate the 
dive and f a i lu re  of the nose-wheel doors,. and substantially reduce the 
motions and accelerations. 
INTRODUCTION 
A ditching investigation of a model of the North American B-45 a i r -  
plane was made t o  observe the behavior and determine the proper 
technique t o  be used i n  an emergency water landing. 
Restriction/Classification Cancelled
Restriction/Classification Cancelled
NACA RM SLgL22a 
The B-45 ditching model and information pertinent thereto were 
furnished by the A i r  Materiel Command, U. S. A i r  Force. A three-view 
drawing of the B-45 airplane i s  shown i n  f igure 1. The investigation 
was made i n  calm water a t  the Langley tank no. 2 monorail. 
APPARATUS AND PROCEDURE 
Description of Model 
1 The rn-scale dynamic model of the  B-45 airplane shown i n  f igure 2 
was used i n  the investigation. It was constructed of balsa wood and 
white cedar, and was bal lasted in terna l ly  t o  obtain scale weight and 
moments of ine r t i a .  The model had a wing span of 4.95 f e e t  and an 
over - a l l  length of 4.19 f ee t .  
The f l aps  were ins ta l led  so tha t  they could be held i n  the down 
position a t  approximately scale strength. They were hinged and held 
down by thread of such strength tha t  when a model load corresponding 
t o  the ful l -scale  ultimate load was applied t o  the f laps,  the thread 
would break and the f laps  would ro ta te  t o  the up position. The f u l l -  
scale ultimate strength of each inboard f l ap  w a s  9,640 pounds and of 
each outboard f l a p  was 10,300 pounds. 
To investigate the e f fec t  of damage, the bomb-bay doors and nose- 
wheel doors were removed, as shown i n  figure 3, and replaced by 
approximately scale-strength sections. The bomb-bay section was made 
i n  one piece of th in  aluminum f o i l  and no bulkheads or  s t r ingers  were 
used. The ful l -scale  ultimate strength of the bomb-bay doors a s  
determined from s t a t i c  load t e s t s  was 1 .4  pounds per square inch. The 
scale-strength nose-wheel section was made i n  one piece of t h i n  aluminum 
f o i l  glued on a balsa-wood frame. The fu l l - sca le  ultimate strength of 
the nose-wheel doors was 1.6 pounds per square inch. 
The airplane i s  equipped with a number of ditching braces t o  rein-  
force the bomb-bay doors a t  the locations shown i n  figure 4. These 
braces are designed to  take ver t ica l  loads but no fore-and-aft loads. 
Their e f fec t  on the ditching performance was investigated by simulating 
them on the model with scale-strength bomb-bay doors. Details of the 
model braces are shown i n  figure 5. 
In  order t o  improve the ditching character is t ics  of the model, a 
hydroflap was ins ta l led  ahead of the nose-wheel doors as  shown i n  
1 figure 6. The hydroflap on the model was a f l a t  surface of %-inch 
aluminum sheet and was not shaped t o  r e t r ac t  f lush into the fuselage 
bottom. 
NACA RM SLgL22a 
Test Methods and Equipment 
The model was ditched by catapul t ing i n to  the  a i r  t o  permit a 
f r e e  gl ide  onto t he  water. The model l e f t  t h e  launching carr iage at  
scale  speed and a t  the desi red landing a t t i t u d e .  The control  surfaces 
were s e t  so t h a t  t h e  a t t i t u d e  d id  not change appreciably i n  f l i g h t .  
The behavior was recorded by a motion-picture camera, a single- 
component t ime-history accelerometer, and from v isua l  observations. 
The accelerometer had a na tu ra l  frequency of 20 cycles per second 
and was damped t o  about 65 percent of c r i t i c a l .  The reading accuracy 
1 
I 
of t he  instrument was kFg. It was i n s t a l l e d  i n  the  p i l o t s '  compartment 
and both v e r t i c a l  and hor izontal  components of accelera t ion were 
measured by ro t a t i ng  t he  instrument and repeating the  runs. 
Test Conditions 
(Al l  values a r e  f u l l  scale .  ) 
Weight.- The design gross weight of 82,600 pounds was simulated 
i n  the  invest igat ion.  
Moments of i ne r t i a . -  The moments of i n e r t i a  corresponding t o  the  
design gross weight were specif ied a s  follows: 
. . . . . . . . . . . . . . . . . . . . . . .  ROU, s lug-feet2 540,000 
2 Pitch,  slug-feet  . . . . . . . . . . . . . . . . . . . . . .  310,000 
. . . . . . . . . . . . . . . . . . . . . . .  Yaw, slug-feet2 830,000 
A t  the  s t a r t  of the  t e s t s  the  model was ba l las ted  t o  obtain these 
values . 
Center of gravi ty . -  The center of g rav i ty  was located at  28.8 per-  
cent of the  mean aerodynamic chord and 18.5 inches above the  t h r u s t  
l i n e  of t he  engines. 
Landing a t t i t u d e . -  Two a t t i t u d e s  were used i n  the  invest igat ion.  
The 6' a t t i t u d e  i s  near the  s t a l l  angle and t he  2' a t t i t u d e  i s  approxi- 
mately the  s t a t i c  ground a t t i t u d e .  The a t t i t u d e  was measured between 
t h e  fuselage reference l i n e  and the  smooth-water surface.  
Flaps.-  A l l  t e s t s  were made with the  landing f l a p s  i n  the  down 
pos i t ion  at tached at  scale  s t rength .  The'model was not t e s t ed  with 
f l a p s  up decause of the  correspondingly higher landing speed. 
4 NACA RM SLgL22a 
Landing speed.- The landing speeds a s  computed from design lift 
curves are  l i s t e d  i n  table  I. The model was airborne when launched and 
within 510 miles per hour of these speeds. 
Landing gear.- A l l  t e s t s  simulated ditchings with the  landing gear 
retracted.  
Model configurations. - The model was tes ted  i n  the conditions 
l i s t e d  below: 
( a )  No damage simulated. 
(b) Nose-wheel doors and bomb-bay doors approximately scale 
strength. 
( c )  Nose -wheel doors and bomb-bay doors approximately scale 
strength and ditching braces ins ta l led  i n  the bomb bay. 
(d) Nose -wheel doors and bomb-bay doors approximately scale 
strength and the hydroflap instal led.  
RESULTS AND DISCUSSION 
A summary of the r e su l t s  of the investigation i s  presented i n  
tab le  I. The notations used i n  the table  a re  defined as  follows: 
Dived violently - the en t i re  model submerged i n  the water with the 
angle between the water surface and the fuselage reference l i n e  
greater than 20'. 
Ran smoothly - made no apparent osc i l la t ion  about any axis  with the 
model gradually se t t l i ng  in to  the water a s  the forward velocity 
decreased. 
Porpoised - made an undulating motion about the transverse axis  i n  
which some part  of the model remained i n  contact with the water. 
Skipped - made an undulating motion about the transverse axis  i n  which 
the model cleared the water completely. 
Trimmed up - the a t t i t ude  of the model increased immediately a f t e r  
contact with the water. 
Photographs showing character is t ic  behavior are  given in  figure 7. 
Typic:al time h is tor ies  of longitudinal and ve r t i ca l  accelerations are  
NACA RM SLgL22a 5 
shown i n  f igures  8, 9, 10, and 11. A photograph of representative 
damage t o  the scale-strength sections i s  shown i n  figure 12. 
Effect of Landing Flaps 
The inboard f l aps  always f a i l e d  on contact with the water and the 
outboard f laps  f a i l e d  intermittently.  There was no noticeable d i f fe r -  
ence i n  behavior when the outboard f laps  f a i l e d  and when they did not. 
Since the f laps  had no apparent detrimental e f fec t  on behavior it i s  
therefore desirable tha t  they be used i n  a ditching i n  order t o  provide 
the minimum landing speed. 
Effect of Damage and Attitude 
When the model was ditched with no damage simulated it trimmed up 
immediately a f t e r  contact and made a smooth run; the t r i m  decreased as  
the forward velocity decreased. The model made the same type of run 
a t  both the 6' and 2' landing a t t i tudes .  
When the model was tested with scale-strength bomb-bay doors and 
nose-wheel doors it usually dived violently.  A t  the 6' landing a t t i t ude  
( f i g .  7 ( a ) )  the dive occurred about 300 f e e t  ( f u l l  scale) a f t e r  contact. 
The maximum longitudinal deceleration was almost 5g, as  shown i n  
f igure 8 (a ) .  The maximum ver t ica l  acceleration was about -6g as  shown 
i n  f igure l l ( a ) .  (ver t ica l  acceleration i s  l g  due t o  gravity when the 
airplane i s  a t  r e s t .  Negative ve r t i ca l  acceleration i s  i n  a direction 
tending t o  throw the p i l o t s  out of t h e i r  sea ts . )  A t  the 2' landing 
a t t i t ude  the behavior was similar but the dives were more violent and 
usually occurred about 200 f e e t  ( f u l l  scale)  a f t e r  contact. A t  t h i s  
1 
a t t i t ude  the maximum longitudinal deceleration was about 92g, a s  shown 
i n  f igure 8(b) .  A t  both a t t i t udes  the scale-strength bomb-bay doors 
and nose-wheel doors were usually torn away ( f i g .  12 ) .  
With ditching braces in s t a l l ed  i n  the scale-strength bomb bay the 
model continued t o  dive, although the length of run before the dive 
was increased and the deceleration was s l igh t ly  l e s s  ( f i g .  9 ) .  The 
doors and ditching braces were nevertheless usually torn away. 
The maximum nose-high a t t i t ude  resul ted i n  lower accelerations 
and l e s s  violent motions than did the near-level a t t i tude .  Diving 
occurred with or without the ditching braces; however, the braces 
tended t o  make the dives l e s s  violent.  It was observed from the model 
investigation tha t  the a f t  par t  of the fuselage f i l l e d  with water before 
there was appreciable lo s s  of motion. Personnel i n  t h i s  section of the 
airplane probably would not have suff ic ient  time t o  escape safely. 
NACA FW SLgL22a 
Effect of Hydroflap 
With the  hydroflap instal led,  the model usually made one skip and 
a continued porpoising run; hence the dive was eliminated. Sequence 
photographs of typica l  runs are  shown i n  f igures  7(b)  and 7(c) .  The 
scale-strength bomb-bay doors were usually to rn  away completely. The 
scale-strength nose-wheel doors, however, remained in tac t .  
A maximum longitudinal deceleration of about 3% f o r  both a t t i t udes  
;c: 1 
was obtained a s  compared with about 5g a t  the 6 O  a t t i t ude  and about %g 
a t  the  2' a t t i t ude  without the hydroflap. These values are  shown on 
the time-history deceleration curves i n  f igures  10 and 8. The maximum 
ver t i ca l  acceleration with the hydroflap was about +3g t o  -1g and 
without the hydroflap was about +3g t c  -6g. These values a re  shown i n  
figure 11. Although the ditching behavior with the hydroflap was about 
the same a t  both the 6' and 2' a t t i tudes ,  the maximum nose-high a t t i t ude  
would be preferable because of the slower landing speed. 
CONCLUSIONS 
1 From resu l t s  of the investigation of a =-scale model of the North 
American B-45 airplane, the following conclusions were drawn: 
1. The airplane should be ditched a t  the maximum nose-high a t t i t ude  
with the f laps  down fo r  minimum landing speed. 
2. During the ditching, the nose-wheel and bomb-bay doors probably 
w i l l  be torn  away and the rear  of the fuselage flooded. A violent dive 
w i l l  very l i k e l y  occur. Longitudinal decelerations of approximately Tg 
and ve r t i ca l  accelerations of approximately -6g (including gravity) w i l l  
be experienced near the p i l o t s '  compartment. i 
3. Ditching braces in s t a l l ed  i n  the bomb bay w i l l  tend t o  improve 
the behavior s l igh t ly  but w i l l  he torn away along with the bomb-bay 
doors . 
b 
a 
e NACA RM SLgL22a 
B 
4. A hydroflap ins ta l led  ahead of the nose-wheel doors will 
L 
9 eliminate the dive and f a i lu re  of the nose-wheel doors and substant ial ly  
e reduce the motions and accelerations. 
B 
0 
e 
B 
Langley Aeronautical Laboratory 
National Advisory Committee f o r  Aeronautics 
Langley A i r  Force Base, Va.  
Aeronautical Research Scient is t  
crO, 
W i l l i a m  C. Thompson 
Aeronautical Research Scient i s t  
Approved : 8 
C/ John B. Parkinson 
Chief of Hydrodynamics Division 
I 
TABLE I.- SUMMARY OF FLEXXJLTS OF DITCHING 7NVESTIGATION I N  CALM WATER OF A z-SCALE 
DYNAMIC MODEL OF THE NORTH AMEBICAIi B-45 AIRPLANE 
bross  weight, 82,600 lb;  landing f laps,  f u l l  down; a l l  values, f u l l  scale 3 
- - 
Hydroflap ins ta l led  with 
scale -strength bomb- 
bay door s and nose - 
wheel doors $i 
Ditching braces ins ta l led  
with scale-strength 
bomb-bay doors and 
nose -wheel doors 
Dived 
violently 
0. 
.. e 
* e  e NACA RM SL9L22a 
e.. . 
2__- Static ground l ine  
Figure 1. - Three-view drawing of the North American B-45 airplane. 


NACA FM 
SZgL22a 
NACA RBI SLgL22a 
A f t  bomb-bay bulkhead 
Ditching brace stations 
Forward bomb-bay bulkhead 
Figure 4.- Bottom view of fuselage sh~wing locations of ditching braces 
i n  the bomb bay. Dimensions are i n  inches; a l l  values are  full 
scale. 
0  
.a* 
0  
o w e  
0 e  
0  .I 
me.* 
Figure 3 . -  Cross section of model fuselage showing typical  ditching brace. 
- - 
.. . 
..a 
I... 
NACA RM SL9L22a 
Figure 6.- Side view of nose section showing location and s ize  of 
hydroflap. Dimensions are  i n  inches; all values are  full scale. 
NACA FM SLgL22a 
Near contact 
150 f e e t  
300 f e e t  
( a )  Landing at t i tude,  6' 
Figure 7. - Sequence photographs of model pitching with scale-strength 
bomb-bay doors and nose-wheel dsors ins ta l led .  A l l  values a re  -full 
scale.  
NACA RM SLgL22a 
NACA RE4 SL9L22a 
NACA RM SLgL22a 
D... 
. 
. 
Be. 
Time, sec 
(a) Landing at t i tude,  6'; landing speed, l.37 mph. 
Time, sec, 
(b) Landing att i tude, 2'; landing s p e d ,  151 mph. 
Figure 8.- Longitudinal decelerations fo r  typical  ditchings with scale- 
strength bomb-bay doors and nose-wheel doors ins ta l led .  A l l  values 
are  fu l l  scale. 
e. 
. e 
0 e 
NACA RM SL9L22a 
Time, sec 
Figure 9.- Longitudinal decelerations f o r  typica l  ditchings with ditching 
braces, scale-strength bomb-bay doors and nose-wheel doors instal led.  
Landing at t i tude,  6'; landing speed, 137 mph. All values are f u l l  
scale,  
NACA RM SLgL22a 
4 
3 
2 
1 
w 
2 0 0 
.ri o 1 2 3 4 5 '  6 
c, 
rd Time, sec 
!3 
rl 
8 (a) l ~ n d i n g  attitude, 6'; landing s p e d ,  U7 mph. 
a" 
rl 
d 
a 3 
c, 
0 1 2 3 4 5 8 
Time, sec 
(b) Landing attitude, 2'; landing speed, 151 mph. 
Figure 10.- Longitudinal decelerations fo r  typical  ditchings with 
hydroflap, scale-strength bomb-bay doors and nose-wheel doors 
instal led.  A l l  values are f u l l  scale. 
NACA RM SL9L22a 
0 1 2 3 
Time, sec 
(a) Without hydroflap. 
Time, sec 
(b) With bydrof lap instal7.e.de 
Figure 11.- Vertical accelerations for  typical  ditchings with scale- 
strength bomb-bay doors and nose-wheel doors instal led.  Landing 
at t i tude,  6'; landing speed, 137 mph. All values are f u l l  scale. 
e 'e 
B D i B  'e 
~ B P  rp NACA BM SL9L22a 
cacrree 
12, - Rqesendat%ve $0 the s c d e - s t r e ~ B  bomb-bay &wrs 
and nose-wheel doors, 


Ditching Investigation of a 1/18-Scale Model of the North American B-45 Airplane

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