The Gnome-Rhône 9K Mistral was a nine-cylinder 550 hp (405 kW) to 700 hp air-cooled radial engine, that started life as an enlarged Gnome-Rhône 7K with two extra cylinders.
Design and development
The Gnome-Rhône 7K itself was an enlarged version of the Gnome-Rhône 5K which was derived from a licensed version of the Bristol Titan . A redesign of the cylinders is indicated by the K suffix. The 9K was followed by the larger and more powerful 14-cylinder twin row Gnome-Rhône 14K.
The 9K was license produced by Hungarian company Weiss Manfréd Repülogép- és Motorgyár Rt. (WM Rt, the aircraft engine factory of Manfred Weiss). The engine was used successfully in the MÁVAG Héja and Weiss WM-21 Sólyom aircraft. The 9K was also produced in the Soviet Union as the M-75 at GAZ-29 in Zaporozhye. Only small numbers were built and it was dropped in favor of the M-25 a version of the Wright Cyclone and the M-85 a version of the Gnome-Rhône 14K Mistral Major.
9K
9Kbr
9Kdr
9Kdrs
9Kers
9Kfr
I.A.R. 9KIc40
Licence production in Romania by Industria Aeronautică Română (IAR).
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Data from
Type: Nine-cylinder air-cooled radial engine.
Bore: 146 mm (5.75 in)
Stroke: 165 mm (6.50 in)
Displacement: 24.9 l (1,520 cu in)
Length: Kdr 0.5 reduction gear - 1,295 mm (50.98 in)
Kdr 0.666· reduction gear - 1,297 mm (51.06 in)
Kdrs 0.5 reduction gear - 1,323 mm (52.09 in)
Kdrs 0.666· reduction gear - 1,325 mm (52.17 in)
Diameter: 1,299 mm (51.14 in)
Dry weight: Kdr 0.5 reduction gear - 355 kg (783 lb)
Kdr 0.666· reduction gear - 360 kg (790 lb)
Kdrs 0.5 reduction gear - 369 kg (814 lb)
Kdrs 0.666· reduction gear - 374 kg (825 lb)
Valvetrain: Two valves per cylinder, pushrod operated
Supercharger: Kdrsd - single stage centrifugal blower
Fuel system: Carburetor
Fuel type: Gasoline
Cooling system: Air-cooled
Reduction gear: Direct drive, 0.5:1 or 0.666·:1
Power output: Kdr - 370 kW (500 hp) at sea level
Kdrs - 370 kW (500 hp) at 1,500 m (4,900 ft)
Kdrs - 340 kW (450 hp) at 4,000 m (13,000 ft)
Compression ratio: 5.5:1
