Sunbeam Pathan
| Company type | Prototype aero engine |
|---|---|
| Industry | Aerospace engineering |
| Founded | 1928 |
| Founder | Louis Coatalen |
| Products | Aircraft diesel engines |
Design and development
In 1928, Louis Coatalen, the chief engine designer at Sunbeam, initiated the creation of a diesel aero-engine intended for airship applications. Drawing on his prior expertise with both aero and automotive diesel powerplants, he developed the P.1—subsequently named the Pathan—derived from the Dyak engine. A prototype was presented at the 1929 Olympia Aero Show; however, it did not attract any purchase commitments.
The Pathan maintained the same bore and stroke dimensions as the Dyak (120mm by 130mm) and was configured as a water-cooled, six-cylinder inline diesel engine with a total displacement of 8.8 litres (537 cubic inches). It produced 100 horsepower (74.6 kilowatts) at 1,500 revolutions per minute and featured an advanced fuel injection mechanism that allowed for cold starts without external aid.
Due to the termination of the British Airship Programme, this engine never progressed beyond prototype stage and was never mass-produced.
Following his departure from Sunbeam, Coatalen pursued further diesel engine innovations in France, developing the Coatalen V-12 Diesel. Nevertheless, development efforts were hindered by the German invasion in 1940.