The Aichi Navy Type 2 Two-seat Reconnaissance Seaplane (HD-25) was an advanced biplane designed by Heinkel and produced by Aichi for the Japanese Navy.
Heinkel designed the HD-25 in 1926. It was an advanced design for the period, with a ply-covered fuselage, and thick wings with internal cantilever support that reduced the number of external supports needed for the wings. The prototype was designed with catapult launching in mind, but the Japanese asked for that to be removed and replaced with the ability to take off from a short ramp to be carried on top of a gun turret.
The HD-25 was tested in Germany during 1926, after making its maiden flight at Warnemünde, observed by two Japanese engineers. Two prototypes were produced in Germany and shipped to Japan, where they were used for take-off tests using a ramp mounted on the battleship Nagato. The HD-25 was in competition with the Yokosho Type 14, which was developed by the Japanese Navy, but the Heinkel design was judged to be superior and was accepted for production in Japan in March 1928 as the Type 2 Two-seat Reconnaissance seaplane.
Only sixteen Type 2s were built, all between 1926 and 1928. The aircraft served on a number of Japanese heavy cruisers, but had a short front-line service career and was quickly replaced by catapult-launched aircraft with better performance. Three of the now obsolete aircraft were released to the civil market where they were converted to transport aircraft as the Aichi Type 2 Transport (HD-25). The HD-25 was also the basis of the Aichi AB-1 Transport, of which one was produced in 1926, also for civil use.
The HD-25 was one of three Heinkel aircraft imported into Japan in 1926. The HD-26 was tested as the Type 2 One-seat Reconnaissance Seaplane and the HD-28 as the Experimental Three-Seat Reconnaissance Seaplane.
Engine: Napier Lion twelve-cylinder W-type water cooled engine
Span: 48ft 10in
Length: 31ft 9.5in
Empty weight: 3,747lb
Maximum take-off weight (from ships): 5,180lb
Maximum take-off weight (from water): 5,654lb
Max speed: 127mph at sea level
Climb Rate: 15min 14sec to 9,843ft
Range: 568 statute miles