Mamba
Mamba engine on display at Sheffield Hallam University
Type	Turboprop
National origin	United Kingdom
Manufacturer	Armstrong Siddeley
First run	April 1946
Major applications	Boulton Paul Balliol A.W. Apollo Short Seamew
Developed into	Armstrong Siddeley Double Mamba Armstrong Siddeley Adder

The Armstrong Siddeley Mamba was a British turboprop engine produced by Armstrong Siddeley in the late 1940s and 1950s, producing around 1,500 effective horsepower (1,100 kW).

Armstrong Siddeley gas turbine engines were named after snakes.

Design and development

The Mamba was a compact engine ^[1] with a 10-stage axial compressor, six combustion chambers and a two-stage power turbine. The epicyclic reduction gearbox was incorporated in the propeller spinner. Engine starting was by cartridge. The Ministry of Supply designation was ASMa (Armstrong Siddeley Mamba). The ASMa.3 gave 1,475 ehp and the ASMa.6 was rated at 1,770 ehp. A 500-hour test was undertaken in 1948^[1] and the Mamba was the first turboprop engine to power the Douglas DC-3, when in 1949, a Dakota testbed was converted to take two Mambas.

The Mamba was also developed into the form of the Double Mamba, which was used to power the Fairey Gannet anti-submarine aircraft for the Royal Navy. This was essentially two Mambas lying side-by-side and driving contra-rotating propellers separately through a common gearbox.

A turbojet version of the Mamba was developed as the Armstrong Siddeley Adder, by removing the reduction gearbox.^[2]

Variants and applications

ASMa.3 Mamba

^[3]

Armstrong Whitworth Apollo

Avro Athena

Boulton Paul Balliol

Breguet Vultur

Miles M.69 Marathon II

Douglas C-47 Dakota

Short SB.3

ASMa.5 Mamba

Development engine for Armstrong Siddeley ASMD.3 Double Mamba^[3]

ASMa.6 Mamba

^[3]

Short Seamew

ASMa.7 Mamba

A version for civil applications^[3]

Swiss-Mamba SM-1 (aft turbofan variant)

EFW N-20

Mamba 112

(ASMa.6)

Engines on display

An Armstrong Siddeley Mamba is on static display at the Midland Air Museum, Coventry Airport, Warwickshire, at the Royal Air Force Museum Cosford and at the East Midlands Aeropark.

A Mamba is also on display at the Aviation Heritage Museum (Western Australia).^[4]

A Swiss-Mamba SM-1 is on display at the Flieger-Flab-Museum Dübendorf.

A Mamba is also on display at the Hertha Ayrton STEM Centre, Sheffield Hallam University, UK.

Specifications (ASMa.6)

Data from Aircraft engines of the World 1957^[5]

General characteristics

• Type: Turboprop
• Length: 90.2 in (2,290 mm)
• Diameter: 33 in (840 mm)
  
• Frontal area: 5.9 sq ft (0.55 m²)
• Dry weight: 850 lb (390 kg)

Components

• Compressor: 11 stage axial flow
• Combustors: Annular combustion chamber with 24 vapourising burners
• Turbine: 3 stage axial flow
• Fuel type: Aviation Kerosene / JP-4

Performance

• Maximum power output: 1,650 shp (1,230 kW) plus 320 lbf (1.4 kN) thrust ; 1,770 shp (1,320 kW) (equivalent) at 15,000 rpm
• Overall pressure ratio: 6:1
• Air mass flow: 21.5 lb/s (9.8 kg/s) at 15,000 rpm
• Specific fuel consumption: 0.69 lb/(hp⋅h) (0.42 kg/kWh) (equivalent shaft horsepower)
• Power-to-weight ratio: 2.08 hp/lb (3.42 kW/kg) (equivalent shaft horsepower)