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Aichi AB-4

The Aichi AB-4 was a Japanese flying boat from the 1930s.

Designed as a single-engine biplane, the AB-4 served the Imperial Japanese Navy for night reconnaissance missions.

Six units were constructed and entered service as the Experimental 6-Shi Night Reconnaissance Flying Boat, with three later converted into civil transports.

In 1931, the Imperial Japanese Navy commissioned Aichi Tokei Denki Seizo KK, an aircraft manufacturer since 1920, to create a compact, catapult-launched aircraft for night reconnaissance.

This aircraft was intended to track nocturnal shipping activities, aid in spotting naval gunfire during night battles, and direct friendly submarines.

The design that emerged, the AB-4, was an all-metal, single-engine pusher biplane flying boat.

It featured single bay wings that could fold back for shipboard storage and accommodated a crew of three in open cockpits.

A Gasuden Urakaze water-cooled six-cylinder inline engine, driving a two-bladed propeller, powered the aircraft.

The first prototype took flight in May 1932 and exhibited generally good handling but suffered from poor control during take-off and landing, as well as limited visibility for the pilot.

Nevertheless, an additional five prototypes were commissioned for further evaluation.





9.75 m (32 ft 0 in)


13.5 m (44 ft 3 in)

AB-4 transport

14 m (46 ft)


3.94 m (12 ft 11 in)

AB-4 transport

3.9 m (13 ft)

Wing area

47.1 m2 (507 sq ft)

AB-4 transport

46.02 m2 (495 sq ft)

Empty weight

1,610 kg (3,549 lb)

AB-4 transport

1,740 kg (3,836 lb)

Gross weight

2,350 kg (5,181 lb)

AB-4 transport

2,550 kg (5,622 lb)

Max take-off weight

2,600 kg (5,732 lb) when catapult launched


1 × Gasuden Urakaze,

6-cylinder water-cooled inverted inline piston engine

224–246 kW (300–330 hp)


2-bladed wooden fixed-pitch pusher propeller


Maximum speed

164 km/h (102 mph, 89 kn)

Cruise speed

113 km/h (70 mph, 61 kn)

Stall speed

84 km/h (52 mph, 45 kn) at 1,000 m (3,281 ft)

Service ceiling

3,500 m (11,500 ft)

AB-4 transport

Time to altitude

2,800 m (9,186 ft) in 60 minutes 50 seconds

AB-4 transport

2,000 m (6,562 ft) in 23 minutes 20 seconds

Wing loading

50 kg/m2 (10 lb/sq ft)

AB-4 transport

49.2 kg/m2 (10 lb/sq ft)


0.095 kW/kg (0.058 hp/lb)

AB-4 transport

0.1027 kW/kg (0.0625 hp/lb)



1× 7.7 mm (0.303 in) machine gun on a flexible mount in the bow cockpit




Japanese Aircraft 1910–1941-R C Mikesh & A Shorzoe.

The Xplanes of Imperial Japanese Army & Navy 1924-1945-Illustrated Warplane History.


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