Kayaba Ka-1 / O-1 (茅場Ka-1)

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Kayaba Ka-1
The Kayaba Ka-1 was a Japanese gyroplane that initially served as an artillery observer and then as an anti-submarine aircraft.
In the 1930s, many armies around the world were interested in gyroplanes. Japan did not avoid this interest, so in 1932 it purchased 2 British Sierva gyroplanes, which were used for research and air shows. Unfortunately, both crashed a few years after the purchase. The second attempt at gyroplanes was in December 1939, when the Japanese Army bought a Kellett KD-1A gyroplane from the USA, unfortunately it crashed in February 1940.The wreck was abandoned in the hangar and the gyroplanes were forgotten for more than half a year. In November 1940, the Japanese investigated the reason for their defeat during the fighting with the USSR at Khalkhin Gol and concluded that the observation balloons for artillery did not meet the requirements of a modern battlefield. Therefore, the Technical Department of the Army Command (Rikugun Koku Hombu) assumed that the best candidate for an artillery observer would be a gyroplane.They decided to hand over the wreckage of the Kellett KD-1A to Kayaba, which was to repair it and study the technologies used in it. The KD-1A was repaired in April 1941 and began testing on 26 May. During the same period, Kayaba and Kobe Seikosho were commissioned to build similar aircraft.This is how gyroplanes named “Ni-Go-ki” and “San-Go-ki” were created, which means the second and third prototypes. The Technical Department of Rikugun Koku Hombu, after reviewing these prototypes, decided to take the best features from both prototypes and so the hull was to be produced by Kayaba, and the engine, which was a licensed copy of the Jacobs L-4MA-7 engine with a power of 225 hp, along with the rotor, was to be built by the Kobe company. In November 1942, the first prototype was ready.It was tested in the same month on the banks of the Tamagawa River, where it took off without any problems. The Army immediately adopted it without conducting all the tests under the name “Kansoku-ki” or Ka-1 (カ-1), but in 1944 it was renamed “O-Go” (O-Go) due to its similarity to the secret operation “Ka-Go”. Initially, an order was placed for serial production of the Ka-1, but due to raw material shortages, production did not run smoothly and about 98 Ka-1s were produced.Out of 98 machines, the army probably received 60 gyroplanes, 10 of which went down with transport on the way to the Philippines. There were no more than 30 machines in active service, of which about 20 were used for anti-submarine patrols, and the rest were used for training.In 1944, 50 Ka-1 pilots were trained in Hiroshima and the 2nd Ship Squadron (船舶飛行第2中隊) was formed to conduct anti-submarine patrols. For this purpose, the crew was reduced to 1 person, the pilot sat in the back seat, and in the place of the front seat mounts for two depth charges weighing 60 kg were attached. The Ka-1 served as anti-submarine warfare aircraft until the end of the war.The Ka-1 did not sink any U.S. submarines, although sources say that there was at least one attack on an enemy ship, but it was not a successful attack. Although the Ka-1 had been operating since 1944, the Americans did not give it any code name.

Photo and Art


R (1)


Structure description
The Kayaba Ka-1 was a single-engine, two-seater gyroplane of mixed construction. The crew consisted of a pilot and an observer in open cockpits in a tandem arrangement. The gyroplane had a classic, fixed landing gear with a tail wheel. The rotorcraft was powered by air-cooled 8-cylinder Argus As 10C in-line V8 engine with 240 hp with a biplane propeller, the main rotor was triplane.The Kayaba Ka-1 measured 6.95 m in length, with a main rotor diameter of 12.2 m. The curb weight of the gyroplane was 750 kg, and the maximum take-off weight was up to 1170 kg. The rotorcraft could reach a speed of 162 km/h, its cruising speed was 115 km/h, and its range was up to 240 km.

Technical sketches



  • Depth Charges : 120kg (1x60kg , 2x60kg , 1x100kg)

General characteristics

  • Crew: 1 in the bomber version or 2 in the recon version
  • Length: 6.95 m (22ft)
  • Width: 3,02 m (9ft)
  • Overall height: 3.10 m (10ft)
  • Empty weight: 750 kg (1,653 lb)
  • Max takeoff weight: 1,170 kg (2,579 lb)
  • Powerplant: 1 × Argus As 10c inverted V-8 air-cooled piston engine, 180 kW (240 hp)
  • Main rotor diameter: 12.2 m (40 ft 0 in)
  • Main rotor area: 116.9 m2 (1,258 sq ft) 3-bladed auto-rotating rotor
  • Propellers: 2-bladed wooden fixed-pitch propeller


  • Maximum speed: 162 km/h (100 mph, 87 kn)
  • Cruise speed: 115 km/h (71 mph, 62 kn)
  • Range: 240 km (170 mi, 150 nmi)
  • Service ceiling: 3,500 m (11,500 ft)
  • Rate of climb: 5 m/s (980 ft/min)
  • Time to altitude: 1,000 m (3,300 ft) in 3 min 26 seconds, 2,000 m (6,600 ft) in 7 min 49 seconds

The Kayaba Ka-1 would be a very interesting rank 1 aircraft or helicopter, especially as submarines are added. This vehicle can also be used for reconnaissance, but unfortunately there is no such function for air vehicles yet. An interesting feature of the Ka-1 is that it can hover in the air for a while without falling, so you can bomb unaware tanks by surprise from above.Feel free to leave your own opinion on the subject.
Finally, I apologize for the linguistic and logical errors because unfortunately English is not my main language and I had to use google translator.

Ka-1 on video

Japanese Autogyro Autogiro WWII footage KD-1a Kayaba KA-2 KA (youtube.com)

Possible camouflages for the Ka-1



Zakątek nieba ¦ Kayaba Ka-1(2) (airwar.ru)
Japanese reconnaissance autogyro Ka-1 (topwar.ru)
Kayaba Ka-1 : Japan (JPN) (armedconflicts.com)
The Pacific War Online Encyclopedia: Ka-1, Japanese Autogyro (kgbudge.com)
WildEagles: Kayaba Ka-Go & IJAAF Autogyros (arawasi-wildeagles.blogspot.com)
田畑義雄軍曹オートジャイロ部隊物語 (archive.md)
カ号観測機 (かごうかんそくき)とは【ピクシブ百科事典】 (pixiv.net)
Kayaba Ka-1 - Wikipedia
カ号観測機 - Wikipedia