Armstrong Siddeley Double Mamba

The Armstrong Siddeley Double Mamba is a turboprop engine design developed in the late 1940s of around 3000-4000 hp. 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.

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

 * ASMD.1:2,950 shp (2 x ASMa.3) used on Fairey Gannet A.S. Mk.1 and Blackburn B-88
 * ASMD.3:3145 shp (2 x ASMa.5) used on Fairey Gannet A.S. Mk.4
 * ASMD.4:3875 hp (2 x ASMa.6) used on Fairey Gannet AEW Mk.3
 * ASMD.8:3875 hp (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.
 * Blackburn B-88
 * Fairey Gannet

Engines on display
Preserved Double Mamba engines are on public display at the:
 * Australian National Aviation Museum
 * Deutsches Museum Flugwerft Schleissheim
 * Gatwick Aviation Museum
 * South Yorkshire Aircraft Museum
 * Imperial War Museum Duxford
 * Midland Air Museum
 * Queensland Air Museum
 * East Midlands Aeropark
 * Museum of Berkshire Aviation