# Armstrong Siddeley Viper

The Armstrong Siddeley 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 originally developed as an expendable engine for production versions of the Jindivik target drone. Like the J85, the limited-life components and total-loss oil systems were replaced with standard systems for use in crewed 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.
In the 1970s, Turbomecanica Bucharest and Orao Sarajevo acquired the license for the Viper engine, which propelled various Romanian and Yugoslav built aircraft.

## Variants

Data from:Jane's All the World's Aircraft 1955-56, Jane's all the World's Aircraft 1959-60, Jane's All the World's Aircraft 1962-63

### ASV.1

    Short life design study; 1,145 lbf (5.09 kN).

### ASV.2

    Developed short life version, first run in April 1951; 1,145 lbf (5.09 kN).

### ASV.3

    (Mk.100) Short life for missile/target applications, flight-tested in the tail of an Avro Lancaster November 1952; 1,640 lbf (7.30 kN).

### ASV.4

    Short life for missile/target applications first run in 1952, 1,750 lbf (7.78 kN).

### ASV.5

    (Mk. 101) Extended life version for crewed aircraft.

### ASV.6

    Short life for missile/target applications; 1,900 lbf (8.45 kN).

### ASV.7/R

    ASV.7 with re-heat; 2,470 lbf (10.99 kN).

### ASV.8

    (became Viper 8 and Mk.102); Long-life version rated at 1,750 lbf (7.78 kN) for Jet Provost T Mk.3.

### ASV.9

    (became Viper 9 and Mk.103) Similar to ASV.8 with improved turbine materials; 2,000 lbf (8.90 kN).

### ASV.10

    Long-life version with re-designed Sapphire-style compressor first run in January 1956; 1,900 lbf (8.45 kN).

### ASV.11

    (became Viper 11 and Mk.200) ASV.10 with increased mass-flow; 2,500 lbf (11.12 kN).

### ASV.12

    (became Viper 12) up-rated ASV.11 with higher JPT and rated at 2,700 lbf (12.01 kN)

### 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(Mk202) and GAF Jindivik Mk.3 among others.

### Viper 12

    see ASV.12 above

### 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.100

    see ASV.3 above

### Mk.101

    see ASV.5 above

### Mk.102

    see ASV.8 above

### Mk.103

    see ASV.9 and Viper 9 above

### Mk.104

    see ASV.12 above

### Mk.200

    see Viper 11 above

### Mk.202

    see Viper 11 above

### Mk.632

    Built under licence by Turbomecanica and Orao, as the non-afterburning engine for the IAR-93 Vultur A/MB versions, Soko J-22 Orao 1 version, IAR-99 Standard/Șoim versions, and Soko G-4 Super Galeb.

### Mk.633

    Built under licence by Turbomecanica and Orao, as the afterburning engine for the IAR-93 Vultur B version, and Soko J-22 Orao 2 version.

### M.D.30 Viper

    Engines licence-built and developed by Dassault Aviation

### M.D.30R Viper

    2,200 lbf (9.8 kN) with afterburner.

## Applications

* Aermacchi MB-339
* Aermacchi MB-326
* Aero L-29 Delfin (prototype only)
* Atlas Aircraft Impala
* Avro Shackleton
* BAC Jet Provost
* BAC Strikemaster
* Bell X-14
* Blue Origin Charon
* 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 Vultur
* Soko G-2 Galeb
* Soko G-4 Super Galeb

## Specifications (Viper ASV.12)

Data from

#### General characteristics

* Type: Turbojet
* Length: 64.0 in (1,625 mm)
* Diameter: 24.55 in (624 mm)
* Dry weight: 549 lb (249 kg)

#### Components

* Compressor: Seven stage axial
* Combustors: Annular, 24 burners
* Turbine: Single stage
* Fuel type: AVTUR, AVTAG
* Oil system: scavenge, metered

#### Performance

* Maximum thrust: 2,700 lbf (12 kN) at 13,800 rpm
* Overall pressure ratio: 4.3:1
* Air mass flow: 44 lb/s (20 kg/s)
* Specific fuel consumption: 1.09 lb/(hr lbf)
* Oil consumption:1.25 pt/h (0.7 L/h)
* Thrust-to-weight ratio: 4.9