Sunbeam Pathan

The Sunbeam Pathan, also known as the Sunbeam P.1, was a 1920s British diesel aero engine.¹²

Louis Coatalen, Sunbeam engine designer, started work on a diesel powered aero-engine, that would be suitable for use in airships, in 1928.² Using his experience with both aero-engines and auto-mobile diesel engines, the result, given the company designation P.1, was based on the Dyak.² Given the name Pathan, a prototype engine was displayed at the 1929 Olympia Aero Show, but attracted no orders.²

Using the same bore and stroke of the Dyak (120mm x 130mm - 4.72in x 5.12in ), the Pathan was a water-cooled six-cylinder in-line diesel engine with a cubic capacity of 8.8l (537cu in). Rated to give 100 hp (74.6 kW) @ 1,500rpm the engine was fitted with a new type of fuel injection system allowing cold starts without other assistance.¹

The engine did not enter production as the British Airship Programme was cancelled, and with no need for the engine only prototypes were built.¹²

Coatalen continued the development of Diesel engines after he left Sunbeam and returned to France, developing the Coatalen V-12 Diesel engine with limited success, due to the German invasion of 1940 halting further work.¹

Data from ¹

General characteristics

• Type: 6-cylinder, inline diesel engine
• Bore: 4.72 in (120 mm)
• Stroke: 5.12 in (130 mm)
• Displacement: 537 cu in (8.8l)

Components

• Fuel system: Direct fuel injection
• Fuel type: Diesel oil
• Oil system: Dry sump, pressure fed
• Cooling system: Liquid-cooled

Performance

• Power output: 100hp at 1,500 rpm
• Specific fuel consumption: 0.169 L/kW/hr (0.4 pints/hp/hr)
• Oil consumption: 0.0127 L/kW/hr (0.03 pints/hp/hr)