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Aichi AB-4

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

A single engine biplane, the AB-4 was intended to carry out night reconnaissance for the Imperial Japanese Navy.

Six were built and accepted into service as the Experimental 6-Shi Night Reconnaissance Flying boat, three of which were converted to civil transports.

In 1931, the Imperial Japanese Navy instructed the Aichi Tokei Denki Seizo KK, who had been involved in aircraft manufacture, particularly for the Navy, since 1920, to design a small catapult launched night reconnaissance aircraft, intended to observe nocturnal shipping movements, spot naval gunfire during night engagements and to direct friendly submarines.

The resulting design, designated AB-4 by Aichi was a single-engine pusher biplane flying boat of all-metal construction.

Its single bay wings folded backwards for storage aboard ship, while its crew of 3 were housed in open cockpits.

It was powered by a single Gasuden Urakaze water-cooled six-cylinder inline engine driving a two blade propeller.

The first prototype flew in May 1932, and while handling was generally good, it had poor control during take-off and landing, and a poor view for the pilot.

Despite this, a further five prototypes were ordered for 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




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