Unnamed helicopter, A.S.Yakovlev

The first Yakovlev's helicopter. 24k b/w photo from the "History of aircraft construction in the USSR" Vol.2 by V.B.Shavrov, p.446

his helicopter was the first in the USSR of coaxial scheme. Its design started earlier than ones by N.I.Kamov. Original design had a tail stabilizer with two rudders, but it was removed during tests without harm to performance.

First series of test were 'on tie' (40 takeoffs, 5 hours), later series of flights were performed (75 flights,15 hours total). Helicopter did well on lift, hovering, turns, but during high speed flight tests some problems came out. Undesired loads on controls and pitch 'oscillations' appeared at speed above 30km/h and increased with the speed.

Not finished because bureau switched to single-rotor scheme.

Sources [6], Vol.2 p.443;

Technical data

Type

Function

Experimental

Year

1947

Crew

Engines

1*140/160hp M-11FR-1

Rotor diameter

10.0m

Length

6.53m

Empty weight

878kg

Loaded weight

1020kg

Rotor (disk) load

13.0kg/m²

Power load

7.28kg/hp

Maximum Speed (Expected)

150km/h

Maximum Speed (Achieved)

70km/h

Static Ceiling (Expected)

250m

Dynamic Ceiling (Expected)

2700m

Range

235km

Modified March 31, 1997
by Alexandre Savine;

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