Bratukhin B-11

B-11
	Top view of a B-11.
Role	Transport helicopter
National origin	Soviet Union
Manufacturer	Bratukhin
First flight	1948
Number built	2

The Bratukhin B-11 was a prototype Soviet twin-rotor transport helicopter and the last design of the Bratukhin aircraft design bureau to be built.^[1]

Development

The B-11 was similar to the design bureau's earlier B-5, a twin-rotor helicopter, with each rotor driven by an Ivchenko AI-26 radial engine.^[1] Each engine was housed in a pod on an outrigger with the related rotor above.^[1] Designed for a 1947 air force design competition for a general-purpose helicopter. Two prototypes were built and flown in June 1948, test flights showed a problem with rotor-blade stall at high speed and high resonant vibrations in the whole helicopter.^[2] In August 1948 the first prototype was grounded for investigation, but limited testing carried on with the second to find the causes of the problems.^[2]

On 13 December 1948 a blade on the right-hand rotor of the second prototype broke, and the subsequent crash killed the two crew.^[2] The prototype was then re-designed and re-built to overcome the problems, but when flying resumed in 1949 the stall occurred again.^[2] Bratukhin further modified the helicopter in May 1950 with new rotor blades, but development was soon abandoned, and soon after the design bureau was closed down.

Specifications

Data from ^[1]

General characteristics

Crew: 3
Length: 9.76 m (32 ft 0 in)
Empty weight: 3,398 kg (7,491 lb)
Max takeoff weight: 4,510 kg (9,943 lb)
Powerplant: 2 × Ivchenko AI-26G(F) radial piston engine
Main rotor diameter: 2 × 10.00 m (32 ft 10 in)
Main rotor area: 74.71 m² (804.2 sq ft)

Performance

Maximum speed: 155 km/h (96 mph, 84 kn) at 1500m (4920ft)
Range: 328 km (204 mi, 177 nmi)
Service ceiling: 2,550 m (8,370 ft)

References

Notes

^ ^a ^b ^c ^d Orbis 1985, p. 839
^ ^a ^b ^c ^d Nemecek 1986, pp. 386-387

Bibliography

Nemecek, Vaclav (1986). The History of Soviet Aircraft from 1918. London: Willow Books. ISBN 0-00-218033-2.
The Illustrated Encyclopedia of Aircraft (Part Work 1982-1985). Orbis Publishing.

[orbis-1] Orbis 1985, p. 839

[nemecek-2] Nemecek 1986, pp. 386-387

[1]

[2]