The Nelson H-44 is an American single ignition, four-cylinder, horizontally opposed, direct drive, two-stroke aircraft engine that was developed by the Nelson Engine Company for use in motorgliders.^[1]

The H-44 was designed in the period following the Second World War and a specially designed motor glider was created by Hawley Bowlus to utilize the engine, the Bowlus/Nelson Dragonfly.^[1]

The engine was not certified. Under the CAR 5 regulations then in place in the US for gliders, a certified auxiliary power glider could be flown with a non-certified engine and propeller. The engine is instead described on the Dragonfly type certificate.^[1]

The four-cylinder engine runs on a 12:1 mixture of 80 octane gasoline and SAE 30 oil. It is equipped with a single Carter WA1 carburetor and a recoil starter.^[1]

Employed in the Dragonfly the H-44 proved underpowered, which led to the design of the H-49 version. The engine family was not a success and few were produced.^[2][3]

H-44

Original design with a 2.25 in (57 mm) bore and 2.75 in (70 mm) stroke, producing 25 hp (19 kW) at 3900 rpm.^[1]

H-49

Upgraded design with E-225 cylinders giving a 2.375 in (60 mm) bore and 2.75 in (70 mm) stroke, producing 28 hp (21 kW) at 4000 rpm.^[1]

• Bowlus/Nelson Dragonfly^[2][3]

Data from FAA Type Certificate Data Sheet^[1]

• List of aircraft engines