Vultee XP-54

The Vultee Aircraft Corporation was very largely the brainchild of Gerard Vultee, formerly chief engineer at Lockheed Aircraft Corporation during the time that Lockheed was owned by Detroit Aircraft. When Detroit Aircraft went belly-up, Vultee was out of a job. Eventually, he went off on his own in pursuit of financial backing for some ideas he had for a single-engine passenger monoplane. Vultee attracted the attention of the "boy wonder" of Wall Street, Errett Lobban Cord, who already owned or controlled several airlines, automobile manufacturers, and aircraft companies. With $50,000 in cash (sounds like small potatoes today :-) ), Cord founded the Airplane Development Corporation in January 1932, as a subsidiary of the Cord Corporation. Vultee was established as chief engineer of this new company. In 1934, the ADC was reorganized as a division of the Aviation Manufacturing Corporation, which was in turn a subsidiary of the Aviation Corporation, which had recently been taken over by Cord in a stock deal. The Aviation Corporation is best known today as being the parent company of what later became American Airlines. Vultee became a vice-president of the ADC, but retained his title as chief engineer. In 1936, the ADC moved its plant to Downey, California. In 1937, this plant was renamed the Vultee Aircraft Division of the Aviation Manufacturing Corporation.

Gerard Vultee and his wife were killed in a plane crash in January of 1938. He was succeeded as chief engineer by Richard Palmer, who had worked for a time on the Hughes H-1B racer. A syndicate bought out Cord's interest in the company, and a California investment banker named Richard Millar was brought in as vice-president. He moved up as president when Vultee Aircraft Inc. was established in 1939 to acquire the assets of the Aviation Manufacturing Corporation.

On November 27, 1939 the USAAC issued Circular Proposal R-40C, which called for a fighter that would be much more effective than any extant--with a top speed, rate of climb, maneuverability, armament, and pilot visibility, all of which would be far superior to those of any existing fighter. In addition, the fighter was required to have a low initial cost and had to be easy and inexpensive to maintain. The Army specifically mentioned in R-40C that they would consider aircraft with unconventional configurations.

No less than 50 responses came in. Many of them were quickly ruled out, but by the end of 1940, four designs were considered sufficiently worthy of further study. These were designs submitted by Bell, by Curtiss, by Northrop, and by Vultee.

The Vultee Aircraft Corporation's only previous venture into fighter design had been the Model 48 Vanguard, which had been unsuccessful in attracting any Army production contracts. Nevertheless, Richard Palmer's team at Vultee came up with the proposal which was judged the best of the entrants. An initial Army contract covering engineering data and wind tunnel models was issued on June 22, 1940. A contract for one prototype was issued on January 8, 1941 under the designation XP-54. The serial was 41-1210. A second XP-54 was ordered on March 17, 1942, with the serial 42-108994 being assigned.

However, photographs of the second XP-54 exist with the tail number 11211 painted on the fins, which implies that its serial was 41-1211, which would make both planes having consecutive serial numbers, even when ordered more than a year apart. Moreover, 41-1211 conflicts with a serial number allocated to a BT-13A Valiant basic trainer. It appears that the explanation of the discrepancy is a simple printing error in painting the second XP-54 and that its serial really was 42-108994. According to Ray Wagner, the second XP-54 took off on its first flight with the faulty tail number 11211 painted on its fin. However by the time of the second flight, the serial had been replaced with the correct 2108994.

The first model designation for the Vultee XP-54 was actually Model 70, and the Model 84 designation was applied to the XP-54 design after design changes like elimination of the turtledeck behind the cockpit proposed for the Model 70, and change of armament to two 37 mm cannons and two 0.50 caliber machine guns in the nose (see Norton 2008). Moreover, as noted by Balzer (2008), the Model 78 was an XP-54 derivative designed for the export market. The XP-54, designated Model 84 by Vultee, was a twin-boom, low-mounted, inverted gull-wing monoplane powered by an engine mounted in pusher configuration. The engine was to be the Pratt & Whitney X-1800-A4G (military designation H-2600) twenty-four cylinder liquid-cooled engine offering a power output of 1850 hp and driving a set of contra-rotating pusher propellers. The Model 84 was actually an outgrowth of an earlier Vultee proposal known as Model 78, which had a similar configuration but was to be powered by a unsupercharged Allison V-1710 liquid-cooled engine. The single-seat cockpit was sited in the center section of the bullet-shaped fuselage. Magnesium alloy construction was to be used throughout the fuselage. A tricycle landing gear was fitted, with the nosewheel retracting into the fuselage and the mainwheels retracting into the booms.

The center wing section was designed around the newly-developed NACA "ducted wing", in which the airflow was taken in via narrow slots in the wing leading edge and directed over the oil and coolant radiators and then to the intercoolers and eventually fed into the engine via ducts in the wing trailing edge. The landing flaps were so designed that their secondary function was to regulate the airflow through the coolers. This innovation made it possible to house the coolant radiators and the intercooler entirely within the wings.

The original mission of the XP-54 was envisaged to be low- and medium-altitude combat. Six 0.50-inch machine guns were to be mounted in the nose. The estimated maximum weight was 11,500 pounds, and maximum speed was expected to be no less than 510 mph at 20,000 feet, taking six minutes to reach that altitude.

On September 7, 1940, the USAAC announced to Vultee that they were changing the mission of the XP-54 from that of low-level combat to that of high-altitude bomber interceptor. This change necessitated the development of a pressurized cockpit and the installation of turbosupercharging equipment. Armament was changed to a pair of 37-mm T-12/T-13 cannon with 60 rpg and twin 0.50-in M2 machine guns with 500 rpg, all mounted in the nose. The Army also required the fitting of heavy armor protection for the engine and pilot. All of these changes caused the estimate gross weight to creep up to 18,000 pounds.

The pressurized cockpit requirement, combined with the considerable height of the aircraft from the ground, made cockpit entry and exit a problem. In order to attack these problems, a unique solution was evolved--a pilot seat which functioned as an elevator. In order to enter the aircraft, the seat was electrically lowered from the bottom of the aircraft by a switch mounted on the outside of the plane. The pilot would sit down on the seat, throw a switch, and the seat would electrically raise itself up into the aircraft until it reached the flight position. Flight control cables were routed around the opening in the floor, and an inverted U-column was used to support the pilot's control wheel. This ventral access was also valuable in that it made possible the design of a fixed cockpit canopy, which simplified the problem of making a pressure-tight seal. In an emergency (assuming sufficient altitude were available), the elevator seat assembly would be catapulted downward clear of the propeller, making the XP-54 the first American fighter to be fitted with an ejector seat.

The nacelle-type fuselage incorporated yet another unusual feature. Because of the different muzzle velocities of the cannon and machine guns, the entire nose section was moveable so that direction of fire of the machine guns could be elevated by as much as three degrees or depressed by as much as six degrees without changing the flight attitude. The cannon were fixed and did not move. The movement of the nose section and the machine guns was controlled by a special compensating gunsight. The management of these differentially- pointing guns probably would have been a real nightmare.

In October 1940, Pratt & Whitney discontinued all work on its X-1800 engine, and Vultee decided to substitute the 2200 hp twenty-four cylinder liquid-cooled Lycoming XH-2470 in its place. The Lycoming engine was still under development for the Navy at the time. The Lycoming engine was to be fitted with a turbosupercharger, in view of the XP-54's newly-assigned high-altitude role.

With all of these changes, it came as no surprise that the delivery date slipped substantially from the promised date of July 1942. The first XP-54 (41-1210) did not, in fact, fly until January 15, 1943, when test pilot Frank Davis took it for a 31-minute flight from Muroc Dry Lake (now Edwards AFB). This flight went fairly uneventful except for the malfunction of the Curtiss propeller. The faulty propeller was subsequently replaced by a Hamilton-Standard unit. By March 11, ten flights had been made, but it was clear that performance was substantially below that which was guaranteed. In addition, the engine showed metal traces in the oil, and the aircraft was returned to Downey for an engine change. 86 more flights were carried out at Ontario AFB, California, and on October 28, the XP-54 was flown to Wright Field for service testing. However, the Lycoming engine again developed serious problems, and the entire engine had to be returned to the manufacturer for repairs. Repair costs turned out to be prohibitive, and the engine had to be scrapped.

Some sources assert that the XP-54 was dubbed "Swoose Goose" because of its inverted gull wing and cigar-like fuselage. The name was inspired by the 1941 song "Alexander the Swoose", which wa about Alexander who was half-swan and half-goose, Alexander the Swoose (one B-17 was called The Swoose).".

By late 1943, the continual troubles with the Lycoming H-2470 engine had led the Navy to abandon the entire program. The XP-54 was therefore left without an engine. A proposal to adapt the Wright R-2160 Tornado radial engine to fit the XP-54 airframe was briefly considered, the project being redesignated P-68. However the Tornado engine also failed to achieve production, and the P-68 project was abandoned. Although it appeared possible to install the Allison V-3420 in the XP-54 without major structural changes, the delay and expense involved in making such a change resulted in the decision being made not to try to introduce the XP-54 into quantity production. There was even thought given to the installation of a jet engine in the XP-54 airframe, but such a proposal was rejected on the grounds of cost. The projected delay and high costs resulted in a decision not to consider production. The first prototype aircraft continued to be used in an experimental program until problems with the Lycoming engines and lack of spare parts caused termination.

The second XP-54 (42-108994) was delayed by the need to change from two Wright turbosuperchargers to a single experimental General Electric XCM model. Consequently, by the time it was ready for flight, all hope of quantity production of the XP-54 had been abandoned. The second XP-54 finally took to the air on May 24, 1944, when it was taken on a 20-minute flight from Downey to Ontario, California. It flew nine more times, its last flight being on Apr 2, 1945. The engine/turbosupercharger combination was found to be unsatisfactory and they were returned to the manufacturer. Although another engine was fitted to the second XP-54, it was never flown again. The nose section was sent to Elgin AFB for armament tests (the guns were never fired from the air). The rest of the airframe was scrapped.

Vultee proposed a carrier-based version of the XP-54 for the US Navy, the Model 79, which was rejected by the Navy for the SD-112-18 competition in favor of the Grumman F7F Tigercat (Buttler and Griffith 2015).

The first XP-54 was static tested to destruction at Wright Field.

The XP-54 was the last project that the Vultee corporation carried out for the USAAF under its own name. In June 1943, Vultee Aircraft, Inc. merged with Consolidated to form Consolidated Vultee Aircraft Corporation. Although the name of the new conglomerate was contracted to "Convair" internally, this name was not officially registered until 1954 when Convair became a division of General Dynamics.

Specs of the XP-54:

Maximum speed: 381 mph at 28,500 feet, 290 mph at sea level. Initial climb rate: 2300 feet per minute. Climb to 32,100 feet in 27.7 minutes. Service ceiling: 37,000 feet. Weights were 15,262 pounds empty, 18,233 pounds normal loaded, and 19,337 pounds maximum. Dimensions were wingspan 53 feet 10 inches, length 54 feet 8 3/4 inches, height 14 feet 6 inches, and wing area 455.5 square feet.

Sources:

1. The American Fighter, Enzo Angelucci and Peter Bowers, Orion, 1987.
   
   
2. General Dynamics Aircraft and their Predecessors, John Wegg, Naval Institute Press, 1990.
   
   
3. War Planes of the Second World War, Fighters, Volume Four, William Green, 1964.
   
   
4. E-mail from Vahe Demirjian on correct serial of the second XP-54 and the origin of the name "Swoose Goose".
   
   
5. Ray Wagner, American Combat Planes of the 20th Century, Bacon, 2004 on serial number mixup on second XP-54 prototype.
   
   
6. E-mail from Vahe Demirjian on second XP-54 and on Swooze Goose name and original model name and on carrier-based version.
   
   
7. Balzer, G., 2008. American Secret Pusher Fighters of World War II: XP-54, XP-55, and XP-56. North Branch, MN: Specialty Press.
   
   
8. Buttler, T., and Griffith, A., 2015. American Secret Projects 1: Fighters, Bombers, and Attack Aircraft, 1937 to 1945. Manchester, UK: Crecy Publishing.
   
   
9. Norton, W., 2008. U.S. Experimental & Prototype Aircraft Projects: Fighters 1939–1945. North Branch, MN: Specialty Press.