Curtiss XP-55 Ascender by MPM

1/72 scale
Kit No. 72020
Cost: $16.00
Decals: One version by Propagteam for a U.S. Army Air Force prototype
Comments: Engraved panel lines, photo etch details, vacuform canopy, nose weight required

History

The Curtiss-Wright XP-55 Ascender (company designation CW-24) was a fighter prototype, along with the XP-54 and XP-56, that was specifically built to fulfill a U.S. military request for unconventional fighter designs arising from the United States Army Air Corps (USAAC) proposal R-40C issued on November 27, 1939. A highly unusual design for its time, it made use of canards located well forward on the fuselage, a rear-mounted engine, swept wings, and two vertical tails. The canards were a revolutionary feature, taking the place of more conventional rear-mounted elevators. Due to its pusher design (the propeller was located at the rear of the fuselage), it was sarcastically referred to as the “Ass-ender.” Like the XP-54, the Ascender was initially designed for the Pratt & Whitney X-1800 engine and had to be re-designed when that engine project was cancelled. It was the first Curtiss fighter aircraft to use tricycle landing gear.

On June 22, 1940, the Curtiss-Wright company received a U.S. Army contract for preliminary engineering data and a powered wind tunnel model. The designation P-55 was reserved for the project. The USAAC was not completely satisfied with the results of these tests, and Curtiss-Wright took it upon itself to build a flying full-scale model which it designated CW-24B. The flying testbed was powered by a 275 hp (205 kW) Menasco C68-5 inline engine. It had a fabric-covered, welded steel tube fuselage with a wooden wing, and non-retractable undercarriage. The CW-24B was successfully flown 169 times at Muroc Dry Lake, California, pointing to several areas in the design needing improvement, and satisified the Air Corps as far as the design’s potential, enough to proceed with development.

On July 10, 1942, the United States Army Air Forces issued a contract for three prototypes under the designation XP-55. Serial numbers were 42-78845 through 42-78847. During this time, the Pratt & Whitney X-1800 H-block sleeve valve engine was experiencing serious developmental delays, and was eventually cancelled. Curtiss decided to switch to the 1,000 hp (750 kW) Allison V-1710 (F16) liquid-cooled inline engine because of its proven reliability. Armament was to be two 20mm cannon and two .50 caliber (12.7mm) machine guns. During the mock-up phase, it was decided to switch to the more powerful 1,275 hp (951 kW) V-1710-95 engine. The 20mm cannon were also replaced by two additional .50 caliber machine guns. A special feature of the XP-55 was a propeller jettison lever located inside the cockpit. This was for the pilot to use prior to bailout to avoid possibly fatal injury by hitting the rear-mounted propeller as he exited the aircraft.

The first XP-55 (42-78845) was completed on July 13, 1943 and had the same aerodynamic configuration as the final prototype CW-24B. The aircraft made its first test flight on July 19th from the Army’s Scott Field near the Curtiss-Wright plant in St Louis, Missouri. The pilot was J. Harvey Gray, Curtiss’ test pilot. Initial testing revealed that the takeoff run was excessively long. To improve the airframe’s lift during takeoff and solve this problem, the size of the nose-mounted canards was increased, and the aileron up trim was interconnected with the flaps so that it operated when the flaps were lowered. More test flights led to further modifications.

On November 15, 1943, test pilot Harvey Gray, flying the first XP-55 (S/N 42-78845), was testing the aircraft’s stall performance at altitude when the XP-55 suddenly flipped over on its back and fell in an uncontrolled, inverted descent. Gray was unable to right the airplane, and it fell out of control for 16,000 feet (4,900 m) before he was able to parachute to safety. The aircraft was destroyed.

The second XP-55 (Serial Number 42-78846) was similar to the first but with a yet larger canard, modified elevator tab systems, and a change from balance tabs to spring tabs on the ailerons. It flew for the first time on January 9, 1944. All flight tests were restricted so that the stall zone which had destroyed the first prototype was avoided. Between September 16 and October 2, 1944, the second XP-55 (42-78846), which had been modified to the same standards as the third aircraft, underwent official USAAF flight trials.

The third XP-55 (S.N. 42-78847) flew for the first time on April 25,1944. It was fitted with four machine guns, and incorporated some of the ideas learned from the loss of the first XP-55. It was found that the aircraft’s stall characteristics could be greatly improved by the addition of four-foot wingtip extensions, and by increasing the sweep of the canard travel. The third and last prototype was ultimately was lost in an accident on May 27, 1945 during the closing day of the Seventh War Bond Air Show at Wright Field in Dayton, Ohio.

Despite its relatively high speed, the overall performance of the XP-55 was not very impressive and was often inferior to that of more conventional fighter aircraft already in service. The XP-55 handled well during normal flight at cruising speeds, but at low speeds became overly sensitive. Other flaws continuing to plague the design, even after modifications, was the engine’s tendency to overheat, and overall stability problems. Meanwhile, truly outstanding conventional fighters such as the Vought F4U Corsair and North American P-51 Mustang had entered service since the Army’s 1939 request for unconventional fighter designs, and by 1944 jet-powered fighter aircraft such as Germany’s Me 262 had appeared, pointing to the possiblity that before long even the P-51 would be obsolete. Development of the XP-55 was therefore cancelled late in 1944. This was the end of a unusual if ultimately unsatisfactory aircraft design, that nonetheless generates interest among aviation enthusiasts to this day. The second prototype XP-55 is on display at the National Air & Space Museum.

Specifications

Length: 29 ft. 7 in. (9.0 m)
Wingspan: 40 ft. 7 in. (12.4 m)
Height: 10 ft. 0 in. (3.0 m)
Wing area: 235 ft² (21.83 m²)
Empty weight: 6,354 lbs. (2,882 kg)
Loaded weight: 7,710 lbs. (3,497 kg)
Maximum takeoff weight: 7,930 lbs. (3,600 kg)
Powerplant: Allison V-1710-95 liquid-cooled V-12 engine of 1,275 hp (951 kW)

Performance
Maximum speed: 390 mph at 19,300 ft. (628 km/h)
Range: 635 miles (1,020 km)
Service ceiling: 34,600 ft. (10,500 m)
Rate of climb: 2,350 ft/min (11.9 m/s)
Wing loading: lb/ft² (kg/m²)
Power/mass: 0.16 hp/lb (0.27 kW/kg)
Armament: 4 × .50 caliber (12.7 mm) machine guns in the nose

The Kit

The XP-55 Ascender comes in a trademark early-MPM red-sided, side opening box. There is no copyright date, but the box proudly proclaims that the kit is made in Bohemia (Czech Republic), probably in the early 1990’s. The kit is injection molded in grey and has engraved panel lines. It consists of 34 plastic parts on a single sprue, 22 metal parts on two photo etch frets, two film transparencies for the cockpit instrumentation, and a single vacuform canopy. The cockpit has relatively good detail including a seat, control stick, photo-etch instrument panel and rudder pedals.

The Curtiss XP-55 on display at the National Air & Space Museum in Dayton, Ohio.

Seat straps are not included, so the modeler will have to add that bit of detail. The kit has a small amount of flash, most notably on the swept back wings, that will have to be trimmed or sanded off. The two canards that appear on either side of the nose are a single part with a connector rod that runs through the nose section. Another part, a nose cap, must be cemented on once the canard is mounted, so filler and sanding will definitely be required to conceal the join seam. The instructions recommend a nose weight be installed just forward of the nose wheel well, otherwise the swept back wings helping to place the center of gravity aft of the cockpit will cause the XP-55 to rest on its tail.

The photo etch parts include an instrument panel (to be used with the film instruments), rudder pedals, nose wheel well, landing gear detail, and realistically thin landing gear doors. The engraved detail on the landing gear is fairly good, but as is often the case with these older MPM kits, there is no internal wheel well detail. In addition, the wheel well openings on the bottom wing will require careful clean-up with an X-acto blade, as there is a bit of flash there. The engine exhausts do not look particularly detailed, and are molded as a single part with the respective halves of the fuselage. The Propagteam decals appear to be thin, with good color depth and perfectly in register.

Conclusion

An impressive kit of an unusual fighter design. Kudos to MPM for providing a limited run kit of a fascinating X-plane. Highly recommended.

References

  • XP-55 instruction sheet
  • U.S. National Air & Space Museum website
  • www.wikipedia.org
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