TYPE: Observer, reconnaissance aircraft

ACCOMMODATION: Pilot only

POWER PLANT: One Hirth HM 502 six-cylinder inverted inline engine, rated at 160 hp

PERFORMANCE: 106 mph

COMMENT: Designed from the outset for use on U-boat “cruisers”, like the Type XI B, the Ar 231 was a light parasol-wing aircraft. The aircraft was powered by an inline engine, weighed around 2,200 lb, and had a 33ft wingspan. The design led to a simple and compact aircraft that could be fitted into a storage cylinder only 6.7 ft in diameter. For ease of storage, the Ar 231’s wings featured detachable sections that two operators could remove in less than six minutes. One unusual feature was an offset wing design, with the right wing root attaching to the wing’s tilted center section (elevated above the fuselage, as on all parasol-wing designs) and lower than the left wing root, to allow the wings to be quickly folded up. Testing soon revealed the Ar 231s to be fragile, underpowered, and difficult to fly even during calm weather, and as a result, development ended in favour of the Focke-Achgelis Fa 330 gyro glider. Some of the testing was done on the auxiliary cruiser “Stier”. Only six prototypes were built (Ref.: 24).

Noteworthy is the fact that the Imperial Japanese Navy (IJN) made similar attempts for submarine-borne aircraft, e. g. the Aichi M6A1 Seiran (Mountain Haze).