Copyright 2003 by Brandon Cope

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Curtis XP-55 Ascender

The XP-55 was one of three aircraft that won the Army’s R-40C Competition, which called for fighters of unconventional design. All used a pusher configuration, but the XP-55 may have been the most unorthodox, with swept wings and a tail-first design (technically, the XP-55 could be considered a flying wing with vertical control surfaces near the ends of the wings). All of the aircraft were supposed to use the Pratt & Whitney X-1800 engine, which was expected to develop 2000 (1492-kW) to 2200 (1641-kW) horsepower with a supercharger. Unfortunately, the engine was cancelled and each design had to make do with alternates. The XP-55 picked a 951-kW Allison engine, which drastically reduced the expected top speed from 509 mph to under 400.

The XP-55 did not fly until July 1943. Several problems were encountered, including a severe stall problem (the plane lost several thousand feet before control could be regained), low-speed instability and the engine tended to overheat. The stability problems could only be partially corrected and, given that by 1944 the performance was no better than any other U.S. fighter, the XP-55 was cancelled.

Only four XP-55 prototypes were built. It uses 43 gallons of aviation fuel per hour at routine usage.

Subassemblies: Medium Fighter chassis with Very Good streamlining+3, Heavy Fighter Wings +2, three retractable wheels +1.
Powertrain: 951-kW aerial HP gasoline engine with 951-kW prop and 110-gallon self-sealing fuel tanks [Wings].
Occupancy: 1 CS  Cargo: 1.1 Wings, 4.2 Body
 
 

Weaponry
4¥ Very Long Aircraft HMG/.50-cal M-2 [Body:F] (250 rounds each)*
* Linked to fire in pairs, plus additional link can fire all four guns at once

Equipment
Body: Short range radio transmitter and receiver, autopilot, IFF

Statistics

HT:  8
HP: 120 [body], 180 [each wing], 12 [each wheel]
 

Design Notes
Design speed was 403 mph. The historical speed has been used, as well as the actual wing area (235 square feet). Unloaded weight was increased 17% to better match historical weight.

Variants
Since the XP-55, did not enter production, there were no historical variants. The one below is fictional and assumes that the P&W X-1800 engine worked out.

P-55A: Assuming that the 1566-kW engine could have been made to work, top speed would have increased to around 509 mph. Fuel consumption would have been 70 gph (requiring one or two drop tanks, probably of 58-gallon capacity, be carried). Loaded weight would have been 4 tons. Other stats: aAccel 16, aDecel 32, aMR 8, Stall 83.

Source:
U.S. Fighters, Jones, Aero Publishers, 1975