Wilksch Airmotive WAM 120 / WAM 160
The Wilksch WAM series is a family of aero-engines for light and general aviation aircraft. WAM series engines are produced by Wilksch Airmotive in Gloucestershire, England. The engine outputs range between 100 hp (75 kW) and 190 hp (142 kW), and are suitable for both tractor and pusher configurations. Initially intended for homebuilt aircraft, the WAM engines may become certified for use on factory-built aircraft.
The WAM unit is a direct-drive two-stroke inverted inline triple with wet-sump, liquid cooling, supercharger, turbocharger and intercooler. Compression boost at startup comes via a supercharger, but once the engine is running, a turbocharger provides additional boost. Being inverted, the engine has its crankshaft at the top directly driving the propeller, and a camshaft at the bottom, immersed in sump oil. Charged air for combustion is introduced under pressure through a gallery of small ports, and exhaust gases are later expelled through a poppet valve in the cylinder head.
The intake ports are small enough to ensure that piston rings do not need to be pegged. Instead of using a gudgeon pin, each piston is connected to its connecting rod via a ball and socket joint, to enable the piston to rotate. This feature may be abandoned in favour of conventional gudgeon pins.
Fuel is filtered, and then supplied by a high pressure feed, surplus fuel being returned to the tank. Fuel injection is by IDI (indirect injection), whereby fuel is injected into a prechamber. A rather old-fashioned system, IDI was adopted for its simplicity and robustness.
Initial development was assisted with a UK government (DTI) grant. The prototype was a two-cylinder model capable of 80 hp (60 kW). The three-cylinder WAM120 produced 100–120 hp (75–89 kW), and the factory intended to produce a follow-up four-cylinder 160 hp (119 kW) motor to compete with engines such as the Lycoming O-360. However, funding proved problematic, and it became expedient to extend the product range by developing a larger capacity version of the three-cylinder motor. Wilksch are said to be still working on a four-cylinder motor.
The testbed aircraft for air trials were a Piper Cub a Shaw Europa and a Thorp T211. To date, some 20 aircraft have flown with WAM power, and one engine has been installed (in pusher mode) in a Staverton-based Rutan Long-EZ. In July 2009, Liberty Aerospace installed a WAM in the USA-built Liberty XL2 aircraft, and the company has agreed to assist Wilksch Airmotive in obtaining FAA certification for the WAM series. This cooperative effort bodes well for the future of Wilksch Automotive, and is expected to lead to the WAM engine becoming a specified option for the Liberty XL2.