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The XP-13 Viper was a prototype biplane fighter aircraft designed by the American company Thomas-Morse Aircraft Corporation. The airplane was delivered to the United States Army in 1929, but they did not adopt it.
| XP-13 | |
|---|---|
.jpg) Thomas-Morse XP-13 | |
| General information | |
| Type | Fighter |
| Manufacturer | Thomas-Morse |
| Designer | B. Douglas Thomas[1] |
| Primary user | United States Army Air Service |
| Number built | 1[2] |
| History | |
| Introduction date | June 1929 |
.jpg)
This aircraft was one of several B. Douglas Thomas designs built in hopes of a production contract from the Army, following the successful Thomas-Morse MB-3 of 1919. Financed by the company, and named the "Viper", it was officially purchased by the Army in June 1929 and designated "XP-13".
The XP-13 fuselage had a corrugated aluminum skin built over a metal frame; the flying surfaces were also metal-framed, but covered with the traditional fabric. While designed to use the 600 hp Curtiss H-1640-1 Chieftain engine, (a novel 12-cylinder two-row air-cooled radial with the rear cylinders directly behind the front cylinders rather than staggered as normal in a two-row radial[3]) for which the XP-13 incorporated a complex system of baffles to direct cooling air over the engine, the engine simply would not stay cool enough, and in September 1930 it was replaced with a Pratt & Whitney SR1340C Wasp of 450 hp. Ironically, the lower-power engine actually resulted in a speed increase of 15 mph, at least partly because of the weight savings.[4]
In the end, the Army decided against production, Thomas-Morse was acquired by Consolidated Aircraft, and the prototype was lost to an inflight fire.
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- XP-13
- Prototype, serial number 29-453 with 600 hp (448 kW) Curtiss H-1640-1 Chieftain hex engine[2]
- XP-13A
- The XP-13 modified with a 525 hp (391 kW) Pratt & Whitney SR-1340-C enclosed in a NACA cowling, along with a revised fin and rudder[5]
- XP-14
- This designation was used for a proposed Curtiss version of the Viper with the Curtiss H-1640-1 Chieftain hex engine
Data from William Green; Gordon Swanborough (1994). The Complete Book of Fighters: An Illustrated Encyclopedia of Every Fighter Aircraft Built and Flown. Salamander. ISBN 978-0-86101-643-3.
General characteristics
- Crew: 1
- Length: 23 ft 6 in (7.16 m)
- Wingspan: 28 ft 0 in (8.53 m)
- Height: 8 ft 5 in (2.56 m)
- Wing area: 189 sq ft (17.6 m2)
- Empty weight: 2,262 lb (1,026 kg)
- Gross weight: 3,256 lb (1,477 kg)
- Powerplant: 1 × Curtiss H-1640-1 Chieftain 12-cyliner two-row air-cooled radial engine, 600 hp (448 kW)
Performance
- Maximum speed: 150 kn (172 mph, 277 km/h) (at sea level)
- Cruise speed: 113 kn (130 mph, 209 km/h) [6]
- Range: 168 nmi (193 mi, 312 km) [6]
- Service ceiling: 20,775 ft (6,300 m)
- Rate of climb: 1,700 ft/min (8.6 m/s) [6]
Armament
none
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