Armstrong Siddeley Double Mamba

Double Mamba
	Preserved Double Mamba at the Imperial War Museum Duxford
Type	Turboprop
Manufacturer	Armstrong Siddeley
First run	29 September 1949 (First flight)
Major applications	Fairey Gannet
Developed from	Armstrong Siddeley Mamba

The Armstrong Siddeley Double Mamba is a turboprop engine design developed in the late 1940s of around 3,000–4,000 hp (2,200–3,000 kW). It was used mostly on the Fairey Gannet anti-submarine aircraft developed for the Fleet Air Arm of the Royal Navy.

Design and development

The Double Mamba (rarely known as the Twin Mamba) was a development of the Armstrong Siddeley Mamba with two Mambas driving contra-rotating propellers through a combining gearbox.^[1]

Engine starting was by cartridge, however, forced air restart was achieved in flight. One engine could be shut down in flight to conserve fuel. Shutting down one engine also stopped one of the propellers.

Variants

Fairey Gannet flying with one half of its Double Mamba engine shut down

ASMD.1: 2,950 shp (2,200 kW) (2 x ASMa.3) used on Fairey Gannet A.S. Mk.1 and Blackburn B-88
ASMD.3: 3,145 shp (2,345 kW) (2 x ASMa.5) used on Fairey Gannet A.S. Mk.4
ASMD.4: 3,875 hp (2,890 kW) (2 x ASMa.6) used on Fairey Gannet AEW Mk.3
ASMD.8: 3,875 hp (2,890 kW) (2 x ASMa.6) used on Fairey Gannet AEW Mk.3

Applications

The Double Mamba engine was also proposed for the Westland Westminster, a 30-seat helicopter that was later built as a prototype powered by a pair of Napier Eland E220 turboshaft engines.

Engines on display

Preserved Double Mamba engines are on public display at the:

Specifications (ASMD.3)

Cut away of a double mamba power unit at The Flambards Experience in Cornwall

Double Mamba in a non-display aircraft at the Fleet Air Arm Museum (Australia).

Data from Flight^[2]

General characteristics

Type: Turboprop engine
Length: 102.25 in (2,597 mm)
Diameter: 52.8 in (1,341 mm)
Dry weight: 2,170 lb (984 kg)

Components

Compressor: 10 stage axial (x2)
Combustors: Six combustion chambers (x2)

Performance

Maximum power output: 2,960 eshp (2,207 kW)
Overall pressure ratio: 5.35:1
Air mass flow: 18.5 lb/sec (8.4 kg/s) per single Mamba unit
Specific fuel consumption: 1.71 lb/(lbf·h)
Power-to-weight ratio: 1.36 eshp/lb

References

Notes

^ Gunston 1989, p.20.
^ Aero Engines 1954 Flight International magazine, Flight Global/Archives, 9 April 1954, on www.flightglobal.com. Retrieved: 29 October 2016

Bibliography

Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9

External links

Original Armstrong Siddeley Double Mamba advertisement - Flight, 29 June 1950

[1] Gunston 1989, p.20.

[2] Aero Engines 1954 Flight International magazine, Flight Global/Archives, 9 April 1954, on www.flightglobal.com. Retrieved: 29 October 2016

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