The Harmon Der Donnerschlag ( en, Thunderclap) is an American

homebuilt aircraft Homebuilt aircraft, also known as amateur-built aircraft or kit planes, are constructed by persons for whom this is not a professional activity. These aircraft may be constructed from "scratch", from plans, or from assembly kits.Armstrong, Kenn ...

that was designed and produced by Harmon Engineering of

Howe, Texas Howe is a town in Grayson County, Texas, United States. The population was 3,451 in the 2020 U.S. Census. It is part of the Sherman– Denison metropolitan statistical area. History The first settlers in the area arrived around the time o ...

. The aircraft was intended for amateur construction.Plane and Pilot: ''1978 Aircraft Directory'', page 142-143. Werner & Werner Corp, Santa Monica CA, 1977.

Design and development

Der Donnerschlag features a wire-braced

shoulder-wing A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple planes. A monoplane has inherently the highest efficiency and lowest drag of any wing con ...

, a single-seat open cockpit, fixed

landing gear Landing gear is the undercarriage of an aircraft or spacecraft that is used for takeoff or landing. For aircraft it is generally needed for both. It was also formerly called ''alighting gear'' by some manufacturers, such as the Glenn L. Martin ...

and a single engine in

tractor configuration In aviation, the term tractor configuration refers to an aircraft constructed in the standard configuration with its engine mounted with the propeller in front of it so that the aircraft is "pulled" through the air. Oppositely, the pusher co ...

. The aircraft's span wing has two beam-type spars and employs a 16% airfoil at the

wing root The wing root is the part of the wing on a fixed-wing aircraft or winged-spaceship that is closest to the fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, o ...

, tapering to a 12% airfoil at the

wingtip A wing tip (or wingtip) is the part of the wing that is most distant from the fuselage of a fixed-wing aircraft. Because the wing tip shape influences the size and drag of the wingtip vortices, tip design has produced a diversity of sha ...

. The standard engine used is the

Volkswagen air-cooled engine The Volkswagen air-cooled engine is an air-cooled, gasoline-fuelled, boxer engine with four horizontally opposed cast-iron cylinders, cast aluminum alloy cylinder heads and pistons, magnesium-alloy crankcase, and forged steel crankshaft and ...

automotive conversion, driving a two-bladed wooden propeller. The aircraft has an empty weight of and a gross weight of , giving a useful load of . With full fuel of the payload is . The aircraft was later developed into the

Harmon Mister America __NOTOC__ The Harmon Mister America was a 1970s American single-seat light sports aircraft designed by James B. Harmon. Plans for home building were made available from the Harmon Engineering Company. It is a mid-wing cantilever monoplane with ...

Operational history

By October 2013 there were no examples registered in the United States with the

Federal Aviation Administration The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic ...

and none may exist anymore.

Specifications (Der Donnerschlag)

References

{{Harmon Engineering aircraft Der Donnerschlag 1960s United States sport aircraft Single-engined tractor aircraft Homebuilt aircraft Shoulder-wing aircraft