Subject: Number Seventy-Seven in the Series--Bell XP-77

From: [email-masked]
Date: 4 Jun 93 16:25:09 GMT

>From [email-masked]

The Bell XP-77 had its origin in a prewar USAAF request for a study of 
the feasiblity of an ultralight fighter that would be smaller, faster, 
and more maneuverable than any fighter then in existence.  The USAAF 
was particularly interested in exploring the possibility of using 
non-strategic materials such as wood, fearing that a shortage of 
aluminum might materialize.  

On October 30, 1941, the USAAF formally requested Bell's Chief 
Designer, Robert J. Woods, to study the problem.  Six month later, 
Woods submitted a design for a low-wing monoplane with a tricycle 
landing gear and a laminar-flow wing equipped with manually-operated 
flaps.  The structure was to be almost entirely of wood, but with a 
metal laminate skin.  

Bell gave the project the company designation Tri-4, the designation 
being a shorthand for the USAAF requirement for "400 hp, 4000 pounds, 
400 mph".  The engine originally chosen for the Tri-4 was the 
twelve-cylinger Ranger XV-770-9 inverted-vee air-cooled supercharged 
engine which offered 500 hp.  It was estimated that a top speed of 410 
mph at 27,000 feet could be attained with this engine.  Armament was 
to have been a pair of 0.50-inch machine guns in the fuselage plus a 
single 20-mm cannon firing through the propeller hub.  

The USAAF authorized the procurement of 25 Tri-4s on May 16, 1942.  
The USAAF requested that provisions be made to carry either a 
300-pound bomb or a 325-pound depth charge.  However, delays in the 
delivery of the supercharged Ranger XV-770-9 engine caused the USAAF 
to reduce the order to only six aircraft on August 20, at which time 
the designation XP-77 was selected.  

At that time, it was decided to install the unsupercharged XV-770-6 
engine (which offered the same power up to 12,000 feet altitude) as a 
temporary measure for initial flight test trials.  It soon became 
apparent to the Bell design team that the XP-77 as originally planned 
would be seriously overweight, which if left uncorrected would result 
in an aircraft which offered no appreciable advantage in performance 
over aircraft already in production.  Consequently, the Bell engineers 
undertook a drastic reduction program to cut the weight of the 
aircraft down to 3000 pounds.  This rework caused costs to rise and 
the date of delivery of the first prototypes to be delayed.  Because 
of the incessant delays and cost overruns, the USAAF cut the XP-77 
order back to only two examples on August 3, 1943.  The USAAF agreed 
that the engine was to be the V-770-7, the AAF designation for the 
Navy's V-770-6.  No further consideration was given to the 
supercharged V-770-9.  

The two XP-77s were finally delivered in the spring of 1944.  Serial 
numbers were 43-34915 and 43-34916.  The low-mounted cantilever wing 
had a single-spar structure with stressed skin.  The wing and the 
fuselage were largely constructed of resin-bonded laminated wood.  The 
tricycle landing gear was electrically-operated.  The nosewheel 
retracted rearwards into the fuselage, and the main landing gear 
retracted inwards into wheel wells in the wing.  The flaps were 
manually controlled.  

Test pilot Jack Woolams took the first XP-77 on its maiden flight on 
April 1, 1944 (April Fool's Day, no doubt a portent of things to 
come).  Test flights showed that the performance was disappointing, a 
speed of only 330 mph at 4000 feet being attained.  The takeoff run 
was excessively long, and test pilots complained that there were some 
unfavorable vibrations at certain engine rpm because of the total lack 
of engine support vibration-damping mounts.  

The second XP-77 went to Elgin Field for fuel consumption and 
operational suitability trials.  On October 2, 1944, this aircraft 
crashed after getting into an inverted spin as the result of a botched 
Immelmann maneuver.  The pilot survived this mishap, but the aircraft 
was destroyed.  

Flight trials continued with the first XP-77, but the USAAF was 
disappointed by the aircraft's relatively poor performance.  The 
performance of the XP-77 was actually inferior to that of aircraft 
already in service.  In addition, by that time in the war, any danger 
of an aluminum shortage had passed.  Consequently, the ultralight 
fighter project was officially abandoned on December 2, 1944.  

After cancellation, the first XP-77 went to Wright Field, then back to 
Elgin, then to Wright again.  It seems to have survived until at least 
1948, since I have a photo of it bearing post-1947 national markings.  
It was seen at various postwar airshows, wearing spurious markings.  
Presumably it was scrapped shortly thereafter, although I am unaware 
of its eventual fate.  Anyone know if it still exists? 

Specification of the XP-77: One Ranger XV-770-6 twelve-cylinder 
inverted-vee air-cooled engine, 520 hp.  Maximum speed 330 mph at 4000 
feet, 328 mph at 12,600 feet.  Initial climb rate was 3600 feet per 
minute, and an altitude of 9000 feet could be attained in 3.7 minutes.  
Service ceiling was 30,100 feet, and maximum range was 550 miles.  
Weights were 2855 pounds empty, 3583 pounds gross, 4028 pounds maximum 
takeoff.  Dimensions were wingspan 27 feet 6 inches, length 22 feet 10 
inches, height 8 feet 2 inches, wing area 100 square feet.  Armament 
was two 0.50-inch machine guns mounted in the fuselage nose, 
synchronized to fire through the propeller arc.  In addition, a 
300-pound bombload could be carried.  

Sources: 

  War Planes of the Second World War, Fighters, Volume Four, William 
  Green, Doubleday, 1964.  

  The American Fighter, Enzo Anguluci and Peter Bowers, Orion Books, 
  1987.  

  United States Military Aircraft since 1909, Gordon Swanborough and 
  Peter M. Bowers, Smithsonian Institution Press, 1989.  

  Fighters of the United States Air Force, Robert F. Dorr and David 
  Donald, Temple Press Aerospace, 1990.  

Joe Baugher		AT&T Bell Laboratories   	
2000 North Naperville Road      Naperville, Illinois 60566-7033