|Hewland AE75 aero-engine|
|Type||Piston aero engine|
|National origin||United Kingdom|
The Hewland AE75 is a lightweight aircraft engine that was manufactured in the mid-1980s by Hewland in Maidenhead, United Kingdom. The engine, a two-stroke inverted inline triple of 750 cc (46 cu in) displacement, is liquid-cooled and yields 75 hp (56 kW)
Design and development
Th AE75 was developed from Hewland's own 500 cc (31 cu in) twin-cylinder microlight engine. The engine was designed specifically for the ARV Super2, a lightweight two-seater shoulder wing aircraft. The AE75's design is compact and light at 49 kg (108 lb) and yields a power-to-weight ratio of 1.14 kW/kg. Lubrication is via 40:1 pre-mix two-stroke oil.
Each of the engine's three cylinders has its own carburetor, with an alternate air device to provide carburetor heat. Each cylinder has twin spark plugs, the sparks being provided by a dual ignition system using engine-triggered amplifiers and coils, rather than the more common aviation magneto. The ignition circuit redundancy is such that if one circuit should fail, all three cylinders will still run. Even if two circuits fail, the engine will still fire on two out of three cylinders.
The engine has a 2.7:1 Propeller Speed Reduction Unit (PSRU) with helical gears in an oil bath. Final drive to the wooden 63 in (160 cm) diameter 2-blade Hoffman propeller was via a rubber “doughnut” coupling. The PSRU design sited the axis of the propeller below that of the crankshaft. This feature allowed a more pointed nose on the ARV, at the cost of slightly reduced propeller clearance.
The Hewland AE75 was never fitted to any aircraft apart from the ARV Super2, and when ARV production ceased, Hewland stopped AE75 production also. The rights to the AE75 were bought by MidWest, who were developing their AE100 twin-rotor Wankel aero-engine. MidWest had intended to restart production of the AE75 near Stroud, Gloucestershire, but this never materialised. MidWest based the AE100's gearbox on the AE75's PSRU, amending it so that the propeller axis was above the eccentric shaft's axis. This increased propeller clearance, but also raised the ARV's thrust line.
MidWest was bought by Diamond Aircraft Industries of Wiener Neustadt, Austria, but MidWest's rights to the Hewland AE75 engine were sold to a Manchester, UK private buyer. The new owner has made some modifications to the AE75, including increasing output from 75 to 90 hp (56 to 67 kW). Also being addressed is one of the AE75's identified deficiencies, the water-pump belt drive which, should the belt break when airborne, can lead to overheating and piston seizure. Resumed production of this modified Hewland engine is uncertain.
- Valvetrain: none (two-stroke piston ports)
- Fuel system: three carburetors, one for each cylinder, with carb heat
- Fuel type: Avgas 100/130 or Auto Gas 91 Octane Minimum
- Oil system: two-stroke pre-mix
- Cooling system: Liquid cooled
- Power output: 75 hp (56 kW) at 6750 rpm
- Fuel consumption: 14 litres/h at 75% power
- Power-to-weight ratio: 1.14 kW/kg
- “Pilot” magazine February 1986 page 32
- ARVSuper2 Pilot's Operating Handbook (POH) section6 page2
- “Pilot” magazine February 1986 page 34
- Super2 Maintenance manual chapter 74 page1
- Super2 Maintenance manual chapter 74 page2
- "Air Pictorial" magazine April 1986
- Light Aircraft Association (March 2011). "LAA Propeller Type List PTL/1" (PDF). Retrieved 31 August 2011.
- Air Accidents Investigation Branch (August 2006). "ARV1 Super 2, G-BMWE". Retrieved 31 August 2011.
- Austro Engine gmbh brochure Nov2 009