Aichi AB-4

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title: "Aichi AB-4" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["1930s-japanese-military-reconnaissance-aircraft", "1930s-japanese-airliners", "flying-boats", "aichi-aircraft", "single-engined-pusher-aircraft", "biplanes", "aircraft-first-flown-in-1932"] description: "Japanese reconnaissance flying boat prototype" topic_path: "geography/japan" source: "https://en.wikipedia.org/wiki/Aichi_AB-4" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Japanese reconnaissance flying boat prototype ::

::data[format=table title="Infobox aircraft"]

Field	Value
name	AB-4
image	File:Aichi_AB-4.png
aircraft_type	Night reconnaissance flying boat
national_origin	Japan
manufacturer	Aichi Kokuki
primary_user	Imperial Japanese Navy
more_users	Nippon Koku Yuso Kenkyusho
number_built	6
first_flight	May 1932
::

| name = AB-4 | logo = | logo_size = | image = File:Aichi_AB-4.png | alt = | caption = | long_caption = | other_names = | aircraft_type = Night reconnaissance flying boat | aim = | outcome = | related = | national_origin = Japan | manufacturer = Aichi Kokuki | design_group = | designer = | builder = | issuer = | status = | owners = | primary_user = Imperial Japanese Navy | more_users = Nippon Koku Yuso Kenkyusho | service = | major_applications = | proposals = | prototypes = | number_built = 6 | construction_number = | civil_registration = | military_serial = | radio_code = | requirement = | aircraft_carried = | flights = | total_hours = | total_distance = | construction_date = | introduction = | retired = | first_flight = May 1932 | initiated = | in_service = | last_flight = | expected = | developed_from = | variants = | developed_into = | preservation = | fate = | predecessors = | successors = | concluded = The Aichi AB-4 was a Japanese flying boat of the 1930s. A single engined 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.

Development and design

In 1931, the Imperial Japanese Navy instructed the Aichi Tokei Denki Seizo KK. (Aichi Watch and Electric Machinery Company, Ltd), 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 ("Aichi Biplane") by Aichi was a single-engined pusher biplane flying boat of all-metal construction. Its single-bay wings folded backwards for storage aboard ship, while its crew of three 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.

Operational history

The six prototypes, designated Experimental 6-Shi Night Reconnaissance Flying Boat were subject to extensive testing and evaluation by the Japanese Navy. While the Navy decided not to order further production of the AB-4, it had a continued requirement for a dedicated night reconnaissance aircraft, which resulted in the Specification that led to the Aichi E10A, which entered service in 1936.

In 1935, three of the six AB-4s were sold to the Japanese Airline Nippon Koku Yuso Kenkyusho, (NKYK). The first aircraft was converted to a cargo transport, while the second and third aircraft were converted to passenger airliners, with the pilot's cockpit moved to the extreme nose (replacing the existing gunners position) and an enclosed passenger cabin, for five and six passengers respectively, added. The third prototype replaced the Gasuden engine with a more powerful Napier Lion.

The three AB-4s were used by NKYK in scheduled services from Osaka, and for sightseeing flights. One crashed into a factory chimney on 27 May 1937, killing all five aboard.

Specifications (Experimental 6-Shi Night Reconnaissance Flying boat)

|ref=Japanese Aircraft 1910-1941 |prime units?=met General characteristics

|crew=3 |length m=9.75 |length note= |span m=13.5 |span note= |height m=3.94 |height note= |wing area sqm=47.1 |wing area note= |aspect ratio= |airfoil= |empty weight kg=1610 |empty weight note= |gross weight kg=2350 |gross weight note= |max takeoff weight kg=2600 |max takeoff weight note= when catapult-launched |fuel capacity= |more general= Powerplant

|eng1 number=1 |eng1 name=Gasuden Urakaze |eng1 type=6-cylinder water-cooled inverted in-line piston engine |eng1 note=300 -

|prop blade number=2 |prop name=wooden fixed-pitch pusher propeller |prop dia m= |prop dia note= Performance

|max speed kmh=164 |max speed note= |max speed mach= |cruise speed kmh=113 |cruise speed note= |stall speed kmh=84 |stall speed note=at 1000 m |never exceed speed kmh= |never exceed speed note= |minimum control speed kmh= |minimum control speed note= |range km= |range note= |combat range km= |combat range note= |ferry range km= |ferry range note= |endurance= |ceiling m=3500 |ceiling note= |g limits= |roll rate= |climb rate ms= |climb rate note= |time to altitude=2800 m in 60 minutes 50 seconds |wing loading kg/m2=50 |wing loading note= |fuel consumption kg/km= |power/mass=0.058 hp/lb |more performance= Armament

|guns= 1× 7.7 mm machine gun on a flexible mount in the bow cockpit |bombs= Flares

References

• Mikesh, Robert and Abe, Shorzoe. Japanese Aircraft 1910–1941. London:Putnam, 1990. .

References

1. Mikesh and Abe 1990, pp.70–71.
2. In the Japanese Navy [[Japanese military aircraft designation systems. designation system]], specifications were given a ''Shi'' number based on the year of the Emperor's reign the specification was issued. In this case 6-''Shi'' stood for 1931.
3. Mikesh and Abe 1990, pp.76–77.
4. Mikesh and Abe 1990, pp.71–72.
5. Mikesh and Abe 1990, p.72.
6. Mikesh and Abe 1990, p.71.

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