https://en.wikipedia.org/wiki/G%C3%B6ppingen_G%C3%B6_9

The Göppingen Gö 9 was a German research aircraft built to investigate the
practicalities of powering a plane using a pusher propeller located far from the
engine and turned by a long driveshaft.

In 1937, Claudius Dornier observed that adding extra engines and propellers to
an aircraft in an attempt to increase speed would also attract a penalty of
greater drag, especially when placing two or more engines within nacelles
mounted on the wings. He reasoned that this penalty could be minimized by
mounting a second propeller at the rear of an aircraft. In order to prevent
tail-heaviness, however, the engine would need to be mounted far ahead of it.
Dornier patented this idea and commissioned a test plane to evaluate it.

The aircraft was designed by Dr Ulrich Hütter as a 40% sized, scaled-down
version of the Dornier Do 17's fuselage and wing panels without the twin-engine
nacelles, and built by Schempp-Hirth. The airframe was entirely of wood and used
a retractable tricycle landing gear – one of the earliest non-Heinkel-built
German airframe designs to use such an arrangement. Power was supplied by a
Hirth HM 60 inverted, air-cooled inline four-cylinder engine mounted within the
fuselage near the wings. Other than the engine installation, the only other
unusual feature of the aircraft was its all-new, full four-surface cruciform
tail, which included a large ventral fin/rudder unit of equal area to the dorsal
surface. This fin incorporated a small supplementary tailwheel protruding from
the ventral fin's lower tip that assisted in keeping the rear-mounted,
four-blade propeller away from the ground during take-off and landing. The Gö 9
carried the civil registration D-EBYW.

Role
Research aircraft

National origin
Nazi Germany

Manufacturer
Schempp-Hirth

Designer
Ulrich Hütter

First flight
1941

Number built
1

Initially towed aloft, flight tests began in June 1941, but later flights
operated under its own power. The design validated Dornier's ideas, and he went
ahead with his original plan to build a high-performance aircraft with
propellers at the front and rear, producing the Dornier Do 335. The eventual
fate of the Gö 9 is not known.

Specifications (Gö 9)

General characteristics
Crew: 1
Length: 6.80 m (22 ft 4 in)
Wingspan: 7.20 m (23 ft 7 in)
Gross weight: 720 kg (1,587 lb)
Powerplant: 1 × Hirth HM 60 4-cyl. inverted air-cooled in-line piston engine, 60
kW (80 hp)
Propellers: 4-bladed pusher propeller turned via an extension shaft

Performance
Maximum speed: 220 km/h (137 mph; 119 kn)




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