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Bristol Siddeley/SNECMA M45H
Rolls-Royce/SNECMA M45H



The Rolls-Royce/SNECMA M45H was a medium bypass ratio turbofan produced specifically for the twin-engined VFW-Fokker 614 aircraft in the early 1970s. The design was started as a collaborative effort between Bristol Siddeley and SNECMA.

The single-stage fan, together with a five-stage LP compressor, was driven by a three-stage LP turbine, whilst the seven-stage HP compressor was driven by a single-stage, air-cooled, HP turbine. An annular combustor and an unmixed exhaust, with a plug-type primary nozzle, were other design features.
The engine was developed at the time of the Rolls-Royce bankruptcy which resulted in delays in developing the engine.

The M45SD-02 or RB.410 was a derivative of the M45H-01 turbofan, designed to demonstrate ultra-quiet engine technologies, needed for STOL aircraft operating from city centre airports.

A geared, variable pitch, fan replaced the first stage of the low pressure (LP) compressor. A modest fan pressure ratio, consistent with the high bypass ratio, meant a low fan tip speed could be employed. A low hot jet velocity was another major design feature.

In reverse thrust, intake air entered the bypass duct, via a gap in the cold nozzle outer wall, and went through the fan, to be expelled through the intake. A small proportion of the bypass duct air entered the IP compressor, via a special diverter valve, to sustain the gas generator. Reverse thrust was obtained by the fan going through fine (rather than feather) pitch. Engine testing took place in the mid 1970s.



M45H Mk.501
Type: Turbofan
Length: 2,600 mm (102.4in)
Diameter: 909 mm (35.8 in)
Dry weight: 673 kg (1,483 lb)
Compressor: 5-stage intermediate pressure and 7-stage high-pressure axial compressor with a single-stage fan
Bypass ratio: 3:1
Combustors: Annular
Turbine: 3-stage low pressure and single-stage high pressure turbines
Maximum thrust: 7,300 lbf (32.4 kN)
Overall pressure ratio: 16.5:1
Thrust-to-weight ratio: 4.9:1



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