Armstrong Siddeley Viper
|Preserved Rolls-Royce Viper Turbojet|
|First run||April 1951|
|Major applications||BAC Jet Provost
|Developed from||AS Adder|
The Viper is a British turbojet engine developed and produced by Armstrong Siddeley and then by its successor companies Bristol Siddeley and Rolls-Royce Limited. It entered service in 1953 and remained in use with the Royal Air Force, powering its Dominie T1 navigation training aircraft until January 2011.
Design and development
The design originally featured a seven-stage compressor based on their Adder engine — the Viper is in effect a large-scale Adder.
Like the similar J85 built in United States, the Viper was developed as an expendable engine for powering production versions of the Jindivik target drone, but, again like the J85, the limited-life materials and total-loss oil systems were replaced with standard systems for use in manned aircraft.
Because it was initially developed as an expendable engine, the Viper was subject to many recurring maintenance issues. This led to the development of the first Power by the Hour program in which operators would pay a fixed hourly rate to Bristol Siddeley for the continual maintenance of the engines.
Data from Jane's All the World's Aircraft 1962-63.
- Viper 8
- (Mk.102 / Mk.104): Engines for the Hunting-Percival Jet Provost TMk.3 (Mk.102} and GAF Jindivik Mk.102B target drone (Mk.104}.
- Viper 9
- (Mk.103): Powered the Bell X-14 and Handley Page HP 115 among others.
- Viper 11
- (Mk.200): Powered the Hunting-Percival Jet Provost TMk.4 and GAF Jindivik Mk.3 among others.
- Viper 20
- (Mk.500 series): Powered the Hawker Siddeley HS.125 and Piaggio-Douglas PD.808 among others.
- Viper 22
- Built under licence by Piaggio for the Aermacchi MB.326
- Mk.500 series
Engines on display
Preserved Viper engines are on public display at the following museums:
- Aerospace Museum of California
- AeroVenture (South Yorkshire Aircraft Museum)
- Midland Air Museum
- Newark Air Museum
- Royal Air Force Museum Cosford
- UniKl MIAT
- Solent Sky
- South African Air Force Museum
- Wings of a Dream Museum (TAM Airlines Museum)
- Aermacchi MB-339
- Aermacchi MB-326
- Atlas Aircraft Impala
- Avro Shackleton
- BAC Jet Provost
- BAC Strikemaster
- Bell X-14
- Dassault M.D.550 Mystere-Delta
- Embraer AT-26 Xavante
- Folland Midge
- GAF Jindivik
- Hawker Siddeley Dominie
- Handley Page HP.115
- IAR 99
- Piaggio PD.808
- Saunders-Roe SR.53
- Soko J-22 Orao/IAR-93
- Soko G-2 Galeb
- Soko G-4 Super Galeb
Specifications (Viper ASV.12)
Data from 
- Type: Turbojet
- Length: 64.0 in (1,625 mm)
- Diameter: 24.55 in (624 mm)
- Dry weight: 549 lb (249 kg)
- Compressor: Seven stage axial
- Combustors: Annular, 24 burners
- Turbine: Single stage
- Fuel type: AVTUR, AVTAG
- Oil system: scavenge, metered
- Maximum thrust: 2,700 lb (12 kN) at 13,800 rpm
- Overall pressure ratio: 4.3:1
- Specific fuel consumption: 1.09 lb/hr/lb
oil consumption=1.25 pints/hr (0.7l/h)
- Thrust-to-weight ratio: 4.9:1
- Related development
- Comparable engines
- Related lists
- Taylor, John W.R. FRHistS. ARAeS (1962). Jane's All the World's Aircraft 1962-63. London: Sampson, Low, Marston & Co Ltd.
- Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
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