Focke-Wulf Fw 61

https://en.wikipedia.org/wiki/Focke-Wulf_Fw_61

The Focke-Wulf Fw 61 is often considered the first practical, functional
helicopter, first flown in 1936. It was also known as the Fa 61, as Focke began
a new company—Focke-Achgelis—after development had begun.

Professor Henrich Focke, through his development of the Fw 186, and through his
work on the C.19 and licence-built C.30 autogyros, came to the conclusion that
the limitations of autogyros could be eliminated only by an aircraft capable of
vertical flight, the helicopter. He and engineer Gerd Achgelis started the
design for this helicopter in 1932. A free-flying model, built in 1934 and
propelled by a small two-stroke engine, brought the promise of success. Today,
the model can be seen in the Deutsches Museum in Munich.

On 9 February 1935, Focke received an order for the building of a prototype,
which was designated the Fw 61; Focke referred to it as the F 61. Roluf Lucht of
the technical office of the RLM extended the order for a second aircraft on 19
December 1935. The airframe was based on that of a well-tried training aircraft,
the Focke-Wulf Fw 44 Stieglitz.

Using rotor technology licensed from the Cierva Autogiro Company, a single
radial engine drove twin rotors, set on tubular steel outriggers to the left and
right of the fuselage.[2] Each main rotor consisted of three articulated and
tapered blades, driven by the engine through gears and shafts. Longitudinal and
directional control was achieved using cyclic pitch and asymmetric rotor lift.
The counter-rotation of the two rotors solved the problem of torque-reaction as
also shown by Louis Bréguet. The small horizontal-axis propeller directly driven
by the engine was purely to provide the necessary airflow to cool the engine
during low speed or hovering flight and provided negligible forward thrust.

Only two aircraft were produced.[1] The first prototype, the V 1 D-EBVU, had its
first free flight on 26 June 1936 with Ewald Rohlfs at the controls. By early
1937, the second prototype, V 2 D-EKRA, was completed and flown for its first
flight. On 10 May 1937, it accomplished its first autorotation landing with the
engine turned off.


Role
Helicopter

Manufacturer
Focke-Achgelis

First flight
26 June 1936

Introduction
1936

Primary user
Nazi Germany

Number built
2

In February 1938, the Fw 61 was demonstrated by Hanna Reitsch indoors at the
Deutschlandhalle sports stadium in Berlin, Germany.[6] It subsequently set
several records for altitude, speed and flight duration culminating, in June
1938, with an altitude record of 3,427 m (11,243 ft),[2] breaking the unofficial
605 meter altitude record of the TsAGI 1-EA single lift-rotor helicopter from
the Soviet Union set in August 1932, and a straight line flight record of 230 km
(143 mi).

Neither of these machines appear to have survived World War II, although a
replica is on display at the Hubschraubermuseum in Bückeburg, Germany.

Specifications (Fw 61)

General characteristics
Crew: one
Length: 7.3 m (23 ft 11 in) fuselage only
Height: 2.65 m (8 ft 8 in)
Empty weight: 800 kg (1,764 lb)
Max takeoff weight: 950 kg (2,094 lb)
Powerplant: 1 × Bramo Sh.14A 7-cyl. air-cooled radial piston engine, 119 kW (160
hp)
Main rotor diameter: 2× 7 m (23 ft 0 in)
Main rotor area: 76.97 m2 (828.5 sq ft)

Performance
Maximum speed: 112 km/h (70 mph, 60 kn) at sea level
Cruise speed: 90 km/h (56 mph, 49 kn)
Range: 230 km (140 mi, 120 nmi)
Service ceiling: 3,427 m (11,243 ft)
Rate of climb: 3.50 m/s (689 ft/min)




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