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 (2,500–3,000 kW). It was used mostly on the Fairey Gannet anti-submarine aircraft developed for the Fleet Air Arm of the Royal Navy.

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.

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

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.

Preserved Double Mamba engines are on public display at the:

Data from Flight

...
Wikipedia