It would be unthinkable today, but during World War II the burgeoning U.S. aircraft industry was able to design, develop, and test numerous warplanes that were not needed and never had a realistic prospect of reaching an operational squadron.
Some said it was also the ugliest.
U.S. Army “Request for Data R40-C” dated Feb. 20, 1940, authorized planemakers to build several experimental aircraft to test new concepts. The biggest and most unorthodox of the new aircraft was the Vultee XP-54 (or Model 84, in company parlance), the largest and heaviest single-engine American warplane to be flown during the war years.
The second prototype of the Vultee XP-54 during its sole flight on May 24, 1944. San Diego Air & Space Museum Archives photo
Some said it was also the ugliest.
The dimensions of the XP-54 tell only part of the story. It had a wingspan of 53 feet 10 inches. It was 54 feet 9 inches long, only ten feet less than a DC-3 airliner. At maximum takeoff weight, the XP-54 tipped the scales at 19,335 pounds, or more than half again the weight of a fully-loaded P-51 Mustang on a combat mission.
It was a single-seat, tricycle-gear fighter with a twin-boom configuration like that of the P-38 Lightning, but with a pusher engine. A little-noticed feature was the “inverted gull” configuration of the wing, like that of the F4U Corsair. Ordered in 1941, the Vultee fighter was designed around the 1,850-horsepower Pratt & Whitney XR-1800-A4G engine and was to have contra-rotating propellers. With this power, the craft was expected to reach a speed of 446 miles per hour. Neither the Third Reich nor the Japanese Empire had anything quite like it, although a much smaller aircraft of almost identical configuration was being developed in Sweden.
In an emergency, the pilot was supposed to be able to jettison the propeller twirling around behind his back and escape the aircraft via a downward ejection.
As happens so often, the intended powerplant of the big XP-54 ran into technical glitches and had to be canceled. The aircraft had to be completed instead with a 2,300-horsepower Lycoming XH-2470-1 24-cylinder liquid-cooled engine driving a single, four-bladed propeller instead of the planned contra-rotating blades.
Apart from the engine switch, the XP-54 faced other challenges. In the book Vultee Aircraft, Jonathan Thompson enumerated the strikes against the XP-54 before it ever flew: The XP-54 was, Thompson wrote, “burdened by unconventional engine, airframe, armament, pilot accommodation and ejection systems” and it would have been “unrealistic” to expect it to become “a successful operational airplane.” In an emergency, the pilot was supposed to be able to jettison the propeller twirling around behind his back and escape the aircraft via a downward ejection. The downward escape system was dictated by another revolutionary feature, a pressurized cockpit, something “engineers really didn’t know how to do in fighters,” at the time, said Dustin W. Carter, an engineer who worked at Vultee.
Vultee built two XP-54s. Frank Davis was the intrepid test pilot who completed the plane’s 31-minute maiden flight on Jan. 15, 1943, at Muroc Dry Lake (now Edwards Air Force Base), Calif. Just weeks later, the XP-54’s builder merged with Consolidated to become the Consolidated Vultee Aircraft Corporation, routinely but unofficially called Convair. With possibly reduced corporate backing, the camouflaged first ship made 86 flights in California before being ferried on Oct. 28, 1943 to Wright Field, Ohio, where further testing apparently occurred only on a limited basis.
The second XP-54, which remained in natural metal, reportedly made only one flight. The XP-54 was designed to carry an enormous arsenal: plans called for two 37-mm cannon and two .50-caliber machineguns. The aircraft was fitted with a nose section that could be tilted upward to “lob” its low-velocity cannon shells at their target, while its machineguns remained in depressed position. The guns were never fired in the air, but after the second XP-54 was scrapped its nose was retained and the armament tested at Eglin Field, Fla., in 1944.
Actual performance figures on the XP-54 with its second-choice powerplant speak of a maximum speed of 403 miles per hour, initial climb rate of 2,300 feet per minute, service ceiling of 37,000 ft and decidedly unimpressive range of 500 miles. As with so many of the experimental ships of the war era, these figures may reflect hope more than documentation.
An even bigger version with the same configuration, the Vultee XP-68 Tornado, progressed far in the design stage but was never built or flown.
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Tim
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Chuck Oldham (Editor)
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9:39 AM February 18, 2010
Interesting aircraft. Looks like it fell victim to the same things that affect today’s aircraft; trying to do too many cutting edge things in one package. The basic airframe looks pretty simple and easy to mass produce. The air-cooled power plant in back doesn’t make much sense to me as the required cooling ducts would cause drag. The weapons package could have been structured more in line with the P-38 using a combination of 50 cals and 20 MM avoiding the whole tilting nose thing. Some other combination of weapons might also have compatible muzzle velocities. With all guns on centerline it could have been a “dive strafer” used against lighter vessels, tanks, and vehicles.Staying away from pressurization avoids lots of combat problems when the aircraft starts acquiring holes and simplifies the ejection system. The gull wing sets up the airframe nicely for carrying big bombs, gun pods, belly tanks, or torpedoes under the belly. Not sure why the counter-rotating props were deleted with the new engine choice unless there were weight and balance issues. At its early stage of development engineering could have realigned the airframe to work with the new engine. Looks like it had good potential just fell victim to too much too soon.
10:59 AM February 19, 2010
Interesting thing about the Lycoming it was completed with: it was an H-24 engine, basically two opposed 12-cylinder engines sharing a common crankshaft. Hawker’s World War II Typhoon used basically the same set-up in its Napier Sabre engine, but with sleeve valves, which added massive complexity and made for early unreliability. I don’t know how reliable the Lycoming was, because it was never mass-produced and there don’t seem to be many records associated with its development.
The 37mm cannon had a trajectory like a rainbow (I’m exaggerating a little), which is probably why they felt they had to design such a needlessly complex nose. If you haven’t read Edwards Park’s Nanette or Angels 20, you should check them out. In addition to being great books, Park describes flying the P-39 Airacobra armed with that 37 mm cannon, and the problems with aiming and firing it. Pilots apparently preferred the P-400 variant’s 20mm instead of the 37mm, not least because of the 37mm’s propensity to jam.
I would bet that if development had continued, the XP-54’s weapons package would have become more like what you describe. What I don’t know, and wonder about, is the details of the ejection system.
Saab seems to have gotten the concept right with the Saab 21. They even managed to use the same airframe when they switched from prop to jet power!