Today we’re taking a look at the Vultee XP-54, unofficially nicknamed the Swoose Goose,
which was an experimental fighter that was developed at the start of the 1940s.
In 1939, the US Army Air Corps faced a bleak outlook. The most modern fighters
in the inventory, the Seversky P-35 and Curtiss P-36A, could barely break 300 mph,
comparing poorly with the German Messerschmitt Bf-109 or the British Supermarine Spitfire,
which were both approximately 50mph faster. There were better American designs under development,
such as the Curtiss P-40 and Lockheed P-38, but neither was in production, and designs submitted
for the 1939 pursuit fighter competition showed little improvement was forthcoming.
Seeking a solution, the Army, instead of hosting a traditional design competition in 1940,
decided to obtain preliminary engineering data from 13 manufacturers, this was done through an
informal request known as Data R-40C. The goal of R-40C was to encourage innovative designs
through a series of wind-tunnel tests, in the hope of leapfrogging the European competition.
The desired characteristics of these so-called innovative designs were outlined in Air Corps
Specification XC-622 in November 1939, This outlined requirements for a single-engine,
single-seat pursuit airplane. It had to be armed with at least four machine guns,
and the suggested engines included the 1,250-hp Allison V-1710, the 1,700-hp Continental V-1430
and the 1,850-hp Pratt & Whitney H-2600. The Army expected the designs would range
from lightweight conventional 425-mph airplanes powered by the V-1710, to more unconventional,
500-mph models, potentially in a pusher configuration powered by the H-2600. They
were to be mostly disappointed though, receiving 26 design proposals that only
represented eight unique concepts, and only some of those were acceptable.
But of those few, some companies had played into the Army’s hands with some truly unique designs.
Of these designs, four would pass the initial evaluation reports,
and thus progress onto the actual design and prototype phases. Interestingly, all four
of these designs were for pusher-propeller aircraft, and these were submitted by Bell,
Curtiss-Wright, Northrop, and Vultee. At the beginning of 1940, the only fighter
designed by Vultee had been the unsuccessful Model 48 Vanguard, which had not received a production
contract. Nevertheless, the Vultee proposal was selected as the winner of the R-40C competition,
and a contract was awarded to produce two wind-tunnel models, which would then
progress to a full-scale mock-up, and then a prototype providing each stage was successful.
As far as designs went, Vultee’s Model 70 certainly met the Army’s requirement for
innovation, seeing as it featured many of them. Firstly, and most obviously,
there was the design of the airframe itself. It was to be built as an inverted gull-wing
monoplane with a twin boom tail, with said tail flanking an 11-foot, four-blade propeller.
The centre wing section was designed around a newly developed NACA ‘ducted wing’,
where airflow was taken in via narrow slots in the leading edge, directed over the radiators
and intercoolers, and then fed into the engine via ducts in the trailing edge. Housing the
coolant radiators and intercoolers entirely within the wings was expected to provide a
significant reduction in total drag and a corresponding increase in speed.
The diameter of the propeller, along with the length of the fuselage and tail booms necessitated
a relatively tall landing gear, but this worked in the favour of another innovative design feature.
The single-seat cockpit, located in the centre section of the fuselage, was to be pressurised.
This was a very advanced feature for the time, and it would allow the pilot, and thus the aircraft,
to perform more comfortably at higher altitudes. However, producing an effective seal for a
pressurised cockpit was a challenge, even more so as traditional cockpit canopies opened outwards
or slid back to allow access. This problem would be overcome in the Model 70 by having
the pilot enter the cockpit from underneath. As the plane stood so high off the ground,
climbing in under their own strength would be almost impossible for the pilot, and so a system
was installed to electrically lower down the pilot seat for easier access. This was also to be used
as primitive ejection seat. With the propeller located behind the pilot, bailing out was a more
perilous affair, and the seat mechanism was also designed to catapult the pilot downward and away
from the propeller disc during an emergency. Its questionable as to how successful this
mechanism would have been, if at all, as it would have only worked in certain scenarios,
none of which involving low altitudes. And then there was also the equally questionable
decision of using magnesium to build the airframe, which, while saving weight, made for incredibly
poor odds in the event of any sort of accident on account of it being extremely flammable.
Leaving the risks of immolation to one side, the aircraft was expected to be highly manoeuvrable,
and it was designed to deliver a heavy punch. Mounted in the nose were a pair of 50 calibre
machine guns and a pair of 37mm T-9 automatic cannons, and this is where another innovative
design feature can be found. The machine guns were installed on flexible mounts, and the
cannons on fixed mounts; the nose was hinged and could be moved vertically through three degrees,
this allowed the pilot to adjust the angle of fire for the cannons with the aid of a gunsight
that compensated for the movement of the nose. This meant that the pilot could better lead his
shots with the lower velocity cannons without large alterations to the planes attitude,
while not affecting the aim of the machine anguns, and this, combined with high altitude performance,
would make the model excellent bomber hunter. Preliminary engineering data predicted a gross
weight of just 9,000 pounds, a top speed of 510 mph at 20,000 feet, and a climb to 20,000 feet
of just six minutes. This data was well received, and on the 19th of August 1940 the Army issued a
half-million-dollar amendment to the contract, authorising more advanced wind tunnel tests
and the manufacture of the first prototype, which would be designated as the XP-54. This,
unfortunately, is where the first of a whole litany of problems began.
Almost as soon as the contract was signed, Vultee announced delays in the production of
the prototype, owing to the complexity of the pressurised cabin. In September the Army agreed
to eliminate the pressurised cabin requirement from the design, with the caveat that Vultee
would design the XP-54 in a way that would facilitate the fitting of said cabin later on.
Nine days later, Vultee instead proposed building a second prototype without pressurisation,
armament, or other equipment not essential for flight testing. This would be produced
more quickly, and then followed by a fully equipped first prototype later on. This
plan was approved, and the contract was modified again to included the
second prototype which was known as the XP-54A. In what was rapidly becoming a trend of bad luck,
the project immediately hit another major snag. As it was becoming more and more apparent that
the United States would find itself at War sooner rather than later, Pratt & Whitney
were given permission to cancel development of their H-2600 engine, with their full focus being
shifted onto the air-cooled radial engines that would become the backbone of Wartime US aircraft.
This left the Army’s experimental program in a bit of a bind as it was now without an engine. But,
two weeks later the Navy approached the army about cooperating on the development of a
different engine that might prove suitable. The engine in question was the 2,200hp Lycoming
XH-2470. During the 1930s, Lycoming developed the 12-cylinder I-1230 as a private venture,
but when its power output was deemed insufficient they decided to mount two of them together, bottom
to bottom, to create a new 24-cylinder engine. On the 8th of October the Army confirmed their
interest in said engine, and much to their surprise, in a field known for countless
delays, they received installation and performance details on the same day.
Vultee was then directed to re-design the XP-54 around this new engine, which necessitated an
increase in overall weight to just over 16,000 pounds. Vultee estimated a top speed of 480 mph,
which whilst slower than the previous design, could be expected to maintain such speed at a
much higher altitude of 27,000 feet. As a result of the engine change, the redesigned aircraft was
known within the company as the Vultee model 78. The full-scale mockup of the plane was completed
by the Spring of 1941, though not without further problems and delays. Over the previous winter,
it had become obvious that the pressurised cockpit was still causing numerous problems,
and it had been agreed that both prototypes would be completed without this feature. By the time of
the inspection, Vultee was confident that their design, having been modified numerous times by
now, would be approved, but reviewers of the US Army Material division had other ideas.
Concerns were raised about the use of supercharges with the new engine, and the Chief of the Material
Division directed that the XP-54 should instead be equipped with turbochargers. This, combined with
numerous other minor requests meant that Vultee was forced to largely redesign the XP-54 again.
Another outcome of the mockup inspection was a desire to re-engine the second prototype with
a 42-cylinder, 2,350hp Wright R-2160 Tornado, which would drive a set of
contra-rotating propellers. And so, along with re-designing the first prototype, again,
Vultee got to work re-engining the second. The second prototype was to be re-designated
as the XP-68, but then, in a decision that would have driven lesser designers to madness,
the development of the XP-68 was terminated owing to delays on the Tornado engines development.
It was then ordered to be redesigned back to, and completed as, an XP-54
to be powered by another Lycoming engine. Finally, after months upon months of delays,
re-designs, assessments, re-designs, wind-tunnel tests, re-designs, and no doubt the occasional
mental breakdown of the draughtsmen, the first XP-54 was finally completed in late 1942.
After a static assessment, where much to the relief of all the army deemed it acceptable,
it was disassembled and transported to Muroc Air Force Base for initial testing. Though it was
the predecessor to Edwards Air Force Base, the home to many an experimental project,
the flight test facilities during the 1940s were significantly less sophisticated than
those of Cold War. Essentially, there was an empty (and hopefully, dry) lakebed,
a tent with a generator, and a radio, and a couple of support vehicles, and that was about it.
In the company of said sparse facilities, in a plane built from highly flammable magnesium,
Vultee test pilot Frank Davis took the XP-54 on its maiden flight on the 15th of January 1943.
The 31-minute flight was uneventful, except for a malfunction of the Curtiss propeller, which
was subsequently replaced by a Hamilton-Standard unit. Davis took the plane on its second flight on
the 27th of January, and by the 11th of March ten flights had been successfully completed.
During said flights Davis reported that it had excellent handling, and particularly it had
very good stall recovery, but there was one noticeable problem. It became apparent that
the expected top speed of 480mph was not going to be achieved, nor anything close,
with the highest speed achieves thus far being only 381 mph. Even worse, it appeared that
something in the engine was beginning to break, as after the last test flights an alarming amount
of metal was being detected in the oil, and the aircraft was sent back for an engine change.
With a new, less broken engine installed, the XP-54 continued its flight tests before being
sent to Wright Field for more advanced performance testing. It was around this time that it appeared
with the name “Swoose Goose” painted on its nose, a name apparently coined by somebody
working at Vultee, no doubt a reference to its elegant, albeit unorthodox appearance.
Unfortunately, this Goose was not going to see its luck improved. As the performance tests were
wrapping up in late 1943, continual problems with the Lycoming engine led the Navy to cancel
its development, and this was pretty much a deathblow to the XP-54 as there weren’t any
other suitable engines available within budget. As a result of this, the two XP-54 prototypes
would be the only examples built. The second prototype was largely similar to the first,
except that it was fitted with armament and an improved turbocharger. It made its first flight
on the 24th of May 1944, rather embarrassingly featuring an incorrect serial number painted on
the tail, which claimed that the aircraft flying was in-fact a Vultee BT-13 Valiant, which to be
fair should be considered an insult to the valiant as it was actually a very successful aircraft.
After some disappointing flights that showed the new turbocharger wasn’t playing nicely
with the engine, the result being the mutual damage of both, the second prototype was
eventually cannibalised for parts to keep the first prototype in a flying condition.
This it did, with the first prototype logging 63 hours across 86 flights before it was grounded,
after which it had the inglorious fate of being tested to destruction at the
structural test labs at Wright Field. In consequence of this,
nothing of this strange aircraft survives today, only photographs.
Similar degrees of failure would be found in the three competing designs that initially
lost out to the XP-54: the Bell XP-52, the Curtiss-Wright XP-55, and the Northrop XP-56.
However, unlike the Vultee model, an example each of both the Curtiss and Northrop designs
still exist today. And all of these examples will get their own videos in the near future.
As always thank you all so much for watching, and a special thank you of course to the patreons,
with a special shoutout to Kevin, Delliardo, Bane, FB, Christopher R,
Tronathon, Erik Hindman, John Austin Jr, Ray Culotta, Keith Tarrier, Greenseaships,
Northlincsweb, MCT, and Ted Parsons for their support as Wing Commander Tier Patreons.