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Yokosuka R2Y (Keiun)

Reconnaissance / Heavy Fighter Prototype [ 1945 ]

Just one flyable prototype - eventually destroyed by American bombs - was witnessed for the Yokosuka R2Y fighter project.

Authored By: Staff Writer | Last Edited: 08/24/2020 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

Heading into 1945, the Imperial Japanese military services were hard-pressed to find viable fighters and turn the tide of the war in the Pacific. Many aircraft projects were undertaken but very few were actually realized, mainly due to the quickly deteriorating situation in Japan proper (caused largely by the American bombing effort on major Japanese infrastructure and weapons-producing facilities). Just prior to the end of the war - which came in August of 1945 for the Japanese Empire - the concern of Yokosuka undertook work on a new fighter platform with reconnaissance capabilities. This product turned out to be the short-lived R2Y "Keiun" ("Cirrus Cloud") which existed only in prototype form before its own end came. A first flight was recorded on May 8th, 1945.

The R2Y was intended for service with the Imperial Japanese Navy (IJN) and followed the unsuccessful, underperforming, R1Y development. The newer design seated a crew of two and carried a pair of coupled engines (2 x Aichi Atsuta of 1,700hp, collectively designated the Aichi Ha-70) driven by a single gearbox. Output power was 3,400 horsepower and a six-bladed propeller unit was fitted at the nose. The cockpit was set well-forward along the tubular fuselage which shifted the engine installations to midships and aft. A retractable tricycle undercarriage gave the R2Y a very modern appearance. The tail unit incorporated a single fin with traditional horizontal planes. Dimensions included a length of 42.9 feet, a wingspan of 45.10 feet and a height of 13.8 feet - the R2Y was a large aircraft for its intended operating class. Empty weight was 13,260lb and Maximum Take-Off Weight (MTOW) reached 20,725lb.

Performance-wise, the design could manage a maximum speed of 480 miles per hour, a range out to 2,250 miles and a service ceiling up to 38,375 feet. Rate-of-climb reached 3,610 feet-per-minute.

The aircraft's armament suite appears to not have been finalized but it most likely would have revolved around automatic cannons fitted to the nose section.

The prototype was made available as soon as April (1945) and this example was the one taken into the air in May. The flight was of short duration and the vehicle was parked when it was caught under the bombs of an American air raid - proving a total loss for the project. This effectively killed any future the R2Y program had. A short-lived jet-powered offshoot, the R2Y2 "Keiun-Kai", was also considered but the proposal was not furthered beyond an incomplete prototype by war's end.©MilitaryFactory.com
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Service Year

Imperial Japan national flag graphic
Imperial Japan

Development Ended.


National flag of modern Japan Imperial Japan
(OPERATORS list includes past, present, and future operators when applicable)
Air-to-Air Combat, Fighter
General ability to actively engage other aircraft of similar form and function, typically through guns, missiles, and/or aerial rockets.
Intelligence-Surveillance-Reconnaissance (ISR), Scout
Surveil ground targets / target areas to assess environmental threat levels, enemy strength, or enemy movement.
X-Plane (Developmental, Prototype, Technology Demonstrator)
Aircraft developed for the role of prototyping, technology demonstration, or research / data collection.

42.8 ft
(13.05 m)
45.9 ft
(14.00 m)
13.9 ft
(4.25 m)
Empty Wgt
13,261 lb
(6,015 kg)
20,723 lb
(9,400 kg)
Wgt Diff
+7,463 lb
(+3,385 kg)
(Showcased structural values pertain to the Yokosuka R2Y production variant)
Installed: 1 x Aichi Ha-70 inline piston engine (2 x Aichi Atsuta of 1,700 horsepower each) developing 3,400 horsepower driving a six-bladed propeller unit at the nose.
Max Speed
478 mph
(770 kph | 416 kts)
41,667 ft
(12,700 m | 8 mi)
2,243 mi
(3,610 km | 6,686 nm)
3,610 ft/min
(1,100 m/min)

♦ MACH Regime (Sonic)
RANGES (MPH) Subsonic: <614mph | Transonic: 614-921 | Supersonic: 921-3836 | Hypersonic: 3836-7673 | Hi-Hypersonic: 7673-19180 | Reentry: >19030

(Showcased performance specifications pertain to the Yokosuka R2Y production variant. Performance specifications showcased above are subject to environmental factors as well as aircraft configuration. Estimates are made when Real Data not available. Compare this aircraft entry against any other in our database or View aircraft by powerplant type)
2 OR 4 x Automatic cannons fitted to the nose or wing assemblies.

Supported Types

Graphical image of an aircraft automatic cannon

(Not all ordnance types may be represented in the showcase above)
Hardpoint Mountings: 0

R2Y - Base Series Designation; single prototype destroyed in Allied air raid.
R2Y2 - Proposed twin turbojet-powered form; incomplete prototype.

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Image of the Yokosuka R2Y (Keiun)
Image from the Public Domain.

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