In the annals of American military aviation there is no shortage of aircraft that promised much and delivered little. But few stories are as rich in technical audacity and institutional frustration as that of the Vultee XP-54 "Swoose Goose" — a radical twin-boom pusher fighter that won its design competition fair and square, flew beautifully, and then died on the drawing board of its own engine.
The XP-54 was one of three revolutionary designs selected from over 100 proposals responding to the Army Air Corps' Circular Proposal R-40C, issued in 1939-40. The other two were the Curtiss XP-55 Ascender and the Northrop XP-56 Black Bullet. All three were radical departures from conventional fighter design. None of them entered production. Together they represent one of the most fascinating dead ends in the history of American military aviation — a moment when the Air Corps invited engineers to imagine what a fighter could be, and then found that the answers, while imaginative, arrived too late to be useful.
The R-40C Competition: Dreaming Big in 1940
By the late 1930s, the Army Air Corps was watching events in Europe with increasing anxiety. The Luftwaffe's performance in Spain and over Poland made it clear that the United States needed fighters that could outperform anything in the German inventory. In late 1939, the Air Corps issued Circular Proposal R-40C, inviting manufacturers to submit proposals for an advanced high-performance fighter with ambitious specifications for speed, ceiling, armament, cost, and maintainability. Crucially, the specification stated that unconventional configurations would be considered.
Vultee Aircraft took that invitation seriously. Their design team, working on what they designated Model 84 (a descendant of the earlier Model 78), produced a twin-boom, pusher-engine, inverted-gull-wing aircraft unlike anything then flying in American service. The proposal beat out the competition and was awarded a prototype contract on January 8, 1941. A second prototype was ordered on March 17, 1942.
On paper, the XP-54 was a remarkable machine. In practice, the gap between the paper and the flight line would prove fatal.
The Configuration: Pusher, Twin Booms, and an Elevator Seat
The XP-54 was designed around a pusher engine mounted in the aft fuselage, driving a 12-foot propeller positioned between two mid-wing tail booms. The wing itself was of inverted gull configuration, incorporating a NACA-developed "ducted wing section" through which cooling airflow for radiators and intercoolers was ducted — a technically elegant solution to the thermal management problem posed by a rear-mounted liquid-cooled engine.
The aircraft was built largely of magnesium to reduce weight and featured a tricycle landing gear: the nose gear retracted backward, while the main gear retracted into the tailbooms.
The pressurized cockpit required an entry system unlike anything in production American aviation. The pilot could not simply climb up the side of the fuselage. Instead, the pilot's seat acted as an elevator: it was lowered electrically to ground level, the pilot sat in it, and was raised up into the pressurized cockpit. It was a clever solution to a genuine engineering problem — and a vivid reminder of how much complexity the XP-54's configuration demanded.
The bail-out procedure was equally unconventional. With a pusher propeller directly behind the cockpit, a conventional upward ejection would send the pilot directly into the propeller arc. The XP-54 therefore used a downward ejection system — the pilot and seat were ejected downward and forward to clear the propeller. This made the XP-54 one of the earliest American aircraft to incorporate an ejection seat of any kind, years before ejection seats became standard.
The Nose That Moved
Perhaps the most unusual feature of the XP-54 was its armament installation. The entire nose section could pivot — three degrees upward and six degrees downward — while the aircraft maintained level flight. In the nose were two 37mm M4 T-12/T-13 cannons in rigid mounts and two .50-caliber machine guns in movable mounts, all aimed by a special compensating gun sight. The practical effect was that the pilot could elevate the cannon trajectory to lead a climbing or diving target without changing the aircraft's flight attitude — a genuinely innovative fire-control concept that anticipated later developments in flexible-armament fighters.
It was this large, distinctive nose section, bulbous and oddly shaped relative to the sleek twin-boom fuselage, that inspired the aircraft's nickname. A popular song of the era described a character named Alexander who was "half-swan and half-goose" — a swoose. The XP-54, with its swan-like booms and goose-like nose, became the Swoose Goose. The name was already in American consciousness: the oldest surviving B-17 Flying Fortress, which had survived the Philippines campaign, bore the same nickname.
The Engine Problem: Three Powerplants and None of Them Right
The XP-54's engine history is a story of compounding misfortune that ultimately decided the aircraft's fate before it ever flew in anger.
The original powerplant specified was the Pratt & Whitney X-1800 — a promising liquid-cooled engine. It was discontinued before the XP-54 could use it. The Wright R-2160 Tornado, an air-cooled radial of enormous power, was briefly considered but Vultee was denied access to it. The fallback was the Lycoming XH-2470 — an H-configuration 24-cylinder liquid-cooled engine that was essentially two Lycoming O-1230 engines joined at a common crankshaft. It produced approximately 2,200–2,300 horsepower and was, on paper, adequate for the task.
In September 1941, the XP-54's mission was changed from low-altitude to high-altitude interception — the result of changing threat assessments. This required the addition of twin Wright B turbo-superchargers and heavier armor plating. Empty weight climbed to approximately 18,000 pounds — an enormous figure for a single-engine fighter of the era. The Lycoming engine, never a robust or reliable unit, was now being asked to push an increasingly heavy aircraft to increasingly demanding altitudes.
Lycoming had a terrible time making the XH-2470 work reliably. The H-configuration was mechanically complex, the cooling demands severe, and the reliability elusive. By the time the aircraft actually flew, engines of comparable or greater power were already in volume production for far more conventional aircraft.
First Flight: January 15, 1943
The first prototype, serial number 41-1210, made its maiden flight on January 15, 1943 at Muroc Dry Lake — the California desert test facility that would later become Edwards Air Force Base. Test pilot Frank Davis of Vultee Aircraft flew a half-hour first flight that revealed something important and something deeply frustrating in equal measure.
The important finding: the XP-54 handled beautifully. For all its mechanical complexity and unconventional layout, the aircraft was pleasant to fly. Its handling characteristics were praised by every pilot who flew it. The twin-boom configuration gave it good stability; the tricycle gear made ground handling straightforward; the pusher arrangement provided excellent forward visibility.
The frustrating finding: performance was substantially below the guarantees Vultee had made in winning the competition. The top speed was nowhere near what had been promised. The climb rate was disappointing. The high-altitude performance — the entire reason the mission had been redefined in 1941 — was not what was needed.
The second prototype, serial number 42-108994 (mistakenly painted as 42-1211 on the airframe), was fitted with an experimental GE XCM single turbo-supercharger in place of the twin Wright units on the first aircraft. This airframe made only ten flights before being relegated to a parts source to keep the first prototype airborne.
The Program Collapses
Development of the Lycoming XH-2470 engine was discontinued while the XP-54 program was still in testing. The obvious alternative — the Allison V-3420, a 24-cylinder liquid-cooled engine of proven reliability — could theoretically have been substituted, but doing so would have required substantial airframe changes. The time and cost of that redesign, added to the already significant delays and budget overruns that had accumulated since 1941, made the arithmetic impossible to justify.
By mid-1944, the program's end was clear. Conventional fighters — the P-51D Mustang and the P-47D Thunderbolt — were in mass production, performing superbly in combat, and available in the thousands. The P-51D was faster than the XP-54's projected maximum speed and had a combat radius that dwarfed anything the XP-54 could have offered. The specialized high-altitude interceptor role that had motivated the R-40C program was being handled effectively by conventional aircraft with conventional engines.
The two XP-54 prototypes continued to be used in experimental testing until problems with the Lycoming engines and the absence of spare parts caused the program to be terminated entirely. Both prototypes were eventually scrapped. No examples of the XP-54 survive.
The R-40C Trio: A Judgment in Retrospect
The three R-40C survivors — the XP-54, XP-55, and XP-56 — are often grouped together as aviation's most spectacular failures. That verdict is too harsh. They were not failures so much as missed windows. The aviation-history.com assessment says it well: they "just missed the window when they would have made a difference." Had R-40C begun two years earlier, had the engines been ready, had the war's pace been different, any of the three designs might have been an effective combat aircraft. The XP-54 in particular had genuinely promising handling qualities and a sophisticated armament concept that was ahead of its time.
Of the three, only the XP-55 Ascender (serial 42-78847, now at the Kalamazoo Air Museum) and one XP-56 Black Bullet (serial 42-38353, at the National Air and Space Museum) survive. The XP-54 exists today only in photographs, test reports, and the memories of the men who flew it.
Walter Boyne, who later wrote the foreword to Gerald H. Balzer's definitive study American Secret Pusher Fighters of World War II, put the broader lesson simply: in aviation, timing is everything. A revolutionary design that arrives when the war has already found its answer is not a revolution — it is an expensive education.
Vultee XP-54 "Swoose Goose" — Technical Profile
| Characteristic | Specification |
|---|---|
| Manufacturer | Vultee Aircraft Corporation |
| Designation | Model 84 / XP-54 |
| Role | High-altitude heavy fighter / interceptor |
| Crew | 1 pilot |
| First flight | January 15, 1943 (Muroc Dry Lake, CA) |
| Test pilot | Frank Davis (Vultee Aircraft) |
| Number built | 2 prototypes |
| Length | 54 ft 9 in (16.69 m) |
| Wingspan | 53 ft 10 in (16.41 m) |
| Height | 14 ft 6 in (4.42 m) |
| Wing area | 456 sq ft (42.4 m²) |
| Empty weight | 15,262 lb (6,923 kg) — increased to ~18,000 lb after high-altitude respec |
| Gross weight | 18,233 lb (8,270 kg) |
| Max takeoff weight | 19,337 lb (8,771 kg) |
| Engine | 1 × Lycoming XH-2470-1, H-24 liquid-cooled, 2,200–2,300 shp |
| Propeller | 12 ft pusher, rear-fuselage mounted |
| Supercharger | Twin Wright B turbo-superchargers (prototype 1); single GE XCM (prototype 2) |
| Construction | Primarily magnesium alloy |
| Landing gear | Tricycle; nose gear retracted aft, mains retracted into tailbooms |
| Top speed (projected) | ~510 mph (821 km/h) — actual performance substantially below guarantee |
| Service ceiling | 37,000+ ft (high-altitude interceptor spec) |
| Primary armament | 2 × 37mm M4 T-12/T-13 cannon (rigid nose mounts) |
| Secondary armament | 2 × .50 caliber M2 machine guns (movable nose mounts) |
| Nose section | Pivoting: 3° up / 6° down, independent of flight attitude |
| Bail-out system | Downward ejection seat (to clear pusher propeller arc) |
| Cockpit entry | Electrically lowered seat as external elevator |
| Program cancelled | 1944 (engine discontinued; costs and delays prohibitive) |
| Survivors | None — both prototypes scrapped |