XP-13 Viper

Infobox Aircraft
name = XP-13
type = Fighter
manufacturer = Thomas-Morse


caption = Thomas-Morse XP-13
designer = B. Douglas Thomas"The Complete Book of Fighters" [http://ec1.images-amazon.com/images/I/21RSY79BDHL.jpgcover] Editors: William Green & Gordon Swanborough (Barnes & Noble Books New York, 1998, ISBN 0760709041), 608 pp.]
first flight =
introduced = June 1929
retired =
status =
primary user = United States Army Air Service
more users =
produced =
number built = 1"U.S. Army Aircraft 1908-1946" by James C. Fahey, 1946, 64pp.]
unit cost =
variants with their own articles = The XP-13 Viper was a prototype biplane fighter aircraft designed by the United States company Thomas-Morse Aircraft Corporation. The airplane was delivered to the United States Army in 1929.

Design and development

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 of 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 bhind the front cylinders rather than staggered as normal in a two row radial Gunston 1986, p.46.] ) 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. ["U.S. Fighters", by Lloyd S. Jones, (Aero Publishers, Inc. ISBN 0816892008, 1975) pp. 46-47]

In the end, the Army decided against production, Thomas-Morse was acquired by Consolidated Aircraft, and the prototype was lost to an inflight fire.

Variants

;XP-13:Prototype, serial number 29-453 with 600 hp (448 kW) Curtiss H-1640-1 Chieftain hex engine"U.S. Army Aircraft 1908-1946" by James C. Fahey, 1946, 64pp.]

;XP-13A:The XP-13 modified with a 525 hp (391.5 kW) Pratt and Whitney SR-1340-C enclosed in a NACA cowling, along with a revised fin and rudder ["The American Fighter", Enzo Angellucci and Peter Bowers, (Orion Books ISBN 0517565889), 1987]

;XP-14:This designation was used for a proposed Curtiss version of the Viper with the Curtiss H-1640-1 Chieftain hex engine

Operators

;flag|United States|1912
United States Army Air Service

pecifications (XP-13 (Chieftain engine))

aircraft specifications
plane or copter?= plane
jet or prop?= prop
ref="The Complete Book of Fighters" [http://ec1.images-amazon.com/images/I/21RSY79BDHL.jpgcover] Editors: William Green & Gordon Swanborough (Barnes & Noble Books New York, 1998, ISBN 0760709041), 608 pp.
crew= 1
capacity=
length main= 23 ft 6 in
length alt= 7.16 m
span main= 28 ft 0 in
span alt= 8.53 m
height main= 8 ft 5 in
height alt= 2.56 m
area main= 189 ft²
area alt= 17.6 m²
airfoil=
empty weight main= 2,262 lb
empty weight alt= 1,026 kg
loaded weight main= 3,256 lb
loaded weight alt= 1,477 kg
useful load main=
useful load alt=
max takeoff weight main=
max takeoff weight alt=
more general=
engine (prop)= Curtiss H-1640-1 Chieftain
type of prop= 12-cyliner two-row air cooled radial engine
number of props= 1
power main= 600 hp
power alt= 448 kW
power original=
max speed main= 150 knots
max speed alt= 172 mph, 277 km/h
max speed more= (at sea level)
cruise speed main= 113 knots
cruise speed alt= 130 mph, 209 km/h Dorr and Donald 1990, p.43]
never exceed speed main=
never exceed speed alt=
stall speed main=
stall speed alt=
range main= 168 NM
range alt= 193 mi, 312 km
ceiling main=20,775 ft
ceiling alt=6,300 m
climb rate main= 1,700 ft/min
climb rate alt= 8.64 m/s
loading main=
loading alt=
thrust/weight=
power/mass main=
power/mass alt=
more performance=
armament= none
avionics=

References

*Dorr, Robert F. and Donald, David. "Fighters of the United States Air Force". London:Temple, 1990. ISBN 0 600 55094 X.
*Gunston, Bill, "World Encyclopedia of Aero Engines".London:Guild Publishing, 1986.

External links

* [http://home.att.net/~jbaugher1/p13.html Berliner-Joyce XP-13 Viper]
* [http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2229 National Museum of the USAF page, with photo]

aircontent
related=
similar aircraft=
lists=
* List of military aircraft of the United States
* List of fighter aircraft