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 was a turboprop engine design developed in the late 1940s of around 3,000–4,000 hp (2,500–3,000 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 (also known as the Twin Mamba) was a development of the Armstrong Siddeley Mamba with two Mambas driving contra-rotating propellers through a combining gearbox.

Engine starting was by cartridge, however, forced air restart was achieved in flight. One engine could be shut down in flight to conserve fuel.

Variants and applications

The numbering system for these engines reflects the obvious linkage to their Mamba lineage:
AS = Armstrong Siddeley
M = Mamba
D = Double
num = model

Table 1. ASMD Models and Aircraft

Model	Thrust (ehp)	Component engines	Aircraft fitted
ASMD.1	2,950	2 x ASM.3	Fairy Gannet A.S. Mk.1 Blackburn B88 (prototype)
ASMD.3	3,145	2 x ASM.5	Fairy Gannet A.S. Mk.4
ASMD.4	3,875	2 x ASM.6	Fairy Gannet AEW Mk.3

The Double Mamba engine was also proposed for the Westland Westminster, a 30-seat helicopter that was later prototyped with another engine.

Engines on display

Preserved Double Mamba engines are on public display at the:

• Deutsches Museum Flugwerft Schleissheim
• Imperial War Museum Duxford
• Midland Air Museum

Specifications (ASMD.3)

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

Data from Flight

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
• Power-to-weight ratio: 1.36 eshp/lb

See also

Related development

• Armstrong Siddeley Mamba
  

Comparable engines

• Allison T40
  

Related lists

• List of aircraft engines
  

References

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