The Hummel Non-Certified aircraft engines include 4-stroke two or four-cylinder opposed direct drive, air cooled engines of different power outputs based on conversions of the original VW engine. The original Hummel conversion has been refined over time, allowing larger displacement and the options of NiCom aluminum cylinders, dual ignition, alternator and electric start. The aluminum NiCom cylinders come as standard with 2-cylinder 45 hp engine and as option for the other 2-cylinder and 4-cylinder engines.

All engines feature a clockwise direction of rotation (facing propeller). No TBO has been set by the manufacturer.

2-cylinder engines are offered in displacements of 840 to 1200 cc with rated horsepower from 28 to 45 hp. Engine weight for the 2-cylinder engines varies from 81 to 103 lbs. 

Offered options (supplied with the engine at additional cost) include a new case, battery ignition, dual ignition, bed, radial or mosler mounting, aluminum NiCom cylinders (for 28/32/37 hp engines), starter and alternator.

These engines power Hummelbird, Ultra Cruiser and other experimental amateur built and ultralight aircraft. 

while the respective horsepower for the 4-cylinder engines is between 50 and 85 hp.

4-cylinder engines are offered in displacements of 1600 to 2400 cc with rated horsepower from 50 to 85 hp. Compression ratio: 7.6- 8 to 1. Engine weight for the 4-cylinder engines varies from 137 to 167 lbs. 

They are based on Type 1 VW crankcase with slick magneto, new case  and hand start and feature pressure lubrication, magneto primary, fixed electronic secondary ignition, 11.32 Amps generator, geared 12v starter and automotive style or shielded aircraft magneto system spark plugs. Different options are offered depending on the selected engine which can be supplied with the engine at additional cost. They include starter, alternator, accessory case, dual ignition and aluminum NiCom cylinders.

The four-cylinder engines have been used as powerplant for aircraft designs like the Sonerai, Sonex, Ultracruiser Plus, Aerosport Quail, Avid Flyer, Corby Starlet and others.

More information are included in the Product Description section.