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The Cheetah X
Part 1: Performance and Design, Machining the Crankshaft and Master Connecting Rod
By J. A. Oates, M.Inst.Met., A.M.I.E.I.

Extensively employed as the power unit for trainer aircraft, the Armstrong-Siddeley seven-cylinder Cheetah engine of 13.66 liters is of simple design and has proved exceptionally reliable and durable. It is required to operate under difficult conditions and stand up to rough treatment by trainee pilots under widely varying climates. The official time between overhauls is the remarkable figure of 1,200 hours. In this first of a series of articles we describe the manufacture of the crankshaft and master connecting rod at one of the Armstrong-Siddeley factories.

This article first appeared in the Volume 5, Number 58 (August, 1943) issue ofAircraft Production magazine, and is presented here through the kind permission ofFlight International. Thanks also to Bruce Vander Mark for furnishing volumes ofAircraft Production for scanning.



Used widely on R.A.F. trainer aircraft and in the Empire Training Scheme, the Armstrong-Siddeley Cheetah X engine of 375 bhp at take-off has an excellent record for reliability and endurance. For example, in Canada the period between overhauls for the Cheetah X has been approved at 1,400 hours, while in this country it has officially stood at 1,200 hours for the past two years. Great credit is due to the firm’s designers for producing an engine that over the years has proved consistently successful under the arduous operating conditions associated with training aircraft.

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