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Mistral Major
Gnome-Rhône 14Ks in a hangar in North Africa, 1943
Type	Radial engine
Manufacturer	Gnome et Rhône
First run	1929
Developed into	Gnome-Rhône 14N

The Gnome-Rhône 14K Mistral Major was a 14-cylinder, two-row, air-cooled radial engine. It was Gnome-Rhône's major aircraft engine prior to World War II, and matured into a highly sought-after design that would see licensed production throughout Europe and Japan. Thousands of Mistral Major engines were produced, used on a wide variety of aircraft.

In 1921 Gnome-Rhône purchased a license for the highly successful nine-cylinder single-row Bristol Jupiter radial engine and produced it until about 1930, alongside the smaller five-cylinder Bristol Titan. Starting in 1926, however, they used the basic design of the Titan to produce a family of new single-row radial engines, the so-called "K series". With increasing numbers of cylinders, these started with the 5K Titan, followed by the 7K Titan Major and 9K Mistral. By 1930, 6,000 of these engines had been delivered.

However, the aircraft industry at that time was rapidly evolving and producing much larger aircraft that demanded larger engines to power them. Gnome-Rhône responded by developing the 7K into a two-row version that became the 14K Mistral Major. The first test examples were running in 1929.

As the Jupiter had set the pattern for one-row radials in the 1920s, the Mistral Major became a canonical design for twin-row radials of the 1930s. It was widely licensed and formed the basis for many successful designs. Among the licensees were Industria Aeronautică Română in Romania, Manfred Weiss in Hungary, Alvis of the UK, Tumansky in the USSR, Walter of Czechoslovakia, and Isotta Fraschini and Piaggio in Italy. Nakajima in Japan also licensed it, but did not put it into production, developing their own designs based on features taken from the Mistral and other designs.

14Kbr

Reduction gearing

14Kbrs

Supercharged with reduction gearing

14Kdr

Reduction gearing

14Kds

Supercharger

14Kdrs

Supercharged with reduction gearing

14Kes

Supercharged (LH rotation)

14Kfs

Supercharged (RH rotation Kers)

14Kirs

Supercharged with reduction gearing (LH rotation)

14Kjrs

Supercharged with reduction gearing (RH rotation Kirs)

14Knrs

Supercharged with reduction gearing (LH rotation)

14Kors

Supercharged with reduction gearing (RH rotation Knrs)

Alvis Pelides

Development of engine with British fasteners. 15 built before project abandoned with start of Second World War as no suitable use in Air Ministry plans.

Isotta Fraschini K.14

license-built in Italy by Isotta Fraschini

IAM K14

licensed derivative produced in Yugoslavia

IAR K14

licensed derivative produced in Romania

Manfréd Weiss WM K-14

licensed derivative produced in Hungary

Piaggio P.XI

licensed derivative produced in Italy

Piaggio P.XIX

higher compression development of Piaggio P.XI

Tumansky M-85

license-built in USSR by Tumansky

Tumansky M-86

960 hp (715 kW) development of M-85 through increased supercharging and a higher compression ratio.^[1]

Tumansky M-87

Tumansky M-88

Walter Mistral Major

ИАМ K.14

Data from ^[2][3]

• Type: Fourteen-cylinder two-row air-cooled radial engine
• Bore: 146 mm (5.748 in)
• Stroke: 165 mm (6.496 in)
• Displacement: 38.673 L (2,360.0 cu in)
• Length: Kds - 1,317 mm (51.85 in)

  Kdr - 0.5 reduction gear - 1,528 mm (60.16 in)

  Kdr - 0.666· reduction gear - 1,530 mm (60.24 in)

  Kdrs - 0.5 reduction gear - 1,554 mm (61.18 in)

  Kdrs - 0.666· reduction gear - 1,556 mm (61.26 in)

• Diameter: 1,288 mm (50.71 in)
• Dry weight: Kdr 0.5 reduction gear - 503 kg (1,109 lb)

  Kdr 0.666· reduction gear - 508 kg (1,120 lb)

  Kdrs 0.5 reduction gear - 523 kg (1,153 lb)

  Kdrs 0.666· reduction gear - 528 kg (1,164 lb)

  Kds 502 kg (1,107 lb)

• Valvetrain: Two Overhead valves per cylinder operated by pushrods
• Supercharger: (Kds / Kdrs - Single-speed centrifugal type supercharger)
• Fuel system: Stromberg carburetor
• Fuel type: 87 octane rating gasoline
• Cooling system: Air-cooled
• Reduction gear: Direct drive, 0.5:1 or 0.666·:1

• Power output: Kdr - 600 kW (800 hp) at sea level

  Kdrs - 580 kW (780 hp) at 1,500 m (4,900 ft) at 2,400 rpm

  Kdrs - 510 kW (680 hp) at 4,000 m (13,000 ft) at 2,400 rpm

  Kds - 560 kW (750 hp) at 1,500 m (4,900 ft) at 2,300 rpm

  Kds - 480 kW (650 hp) at 4,000 m (13,000 ft) at 2,300 rpm

• Specific power: Kdr 15.5 kW/L (0.34 hp/in³)
• Compression ratio: 5.5:1
• Specific fuel consumption: 328 g/(kW•h) (0.54 lb/(hp•h))
• Oil consumption: 20 g/(kW•h) (0.53 oz/(hp•h))
• Power-to-weight ratio: 1.52 kW/kg (0.92 hp/lb)

• 
  A Piaggio P.XI engine at the Malmohus Technical Museum, Malmo, Sweden.
• 
  A Tumansky M-85 at the Aviation Museum of Central Finland.
• 
  Walter Mistral Major.
• 
  A Walter Mistral Major at the Polish Aviation Museum in Krakow.

Related development

• IAR 14K
• Piaggio P.XI
• Tumansky M-87

Related lists

• List of aircraft engines

Wikimedia Commons has media related to Gnome et Rhône 14K.