The Arado Ar-66 was German WW2 two-seat, single-engined biplane trainer of mixed construction designed by Walter Rethel’s. It was last Rethel’s completed design for Arado before his transfer to Messerschmitt.
The tailplane was mounted on a raised rear fuselage fairing, ahead of the vertical tail surface which comprised a wholly movable rudder, there being no fin. The first prototype, the Arado Ar-66-a of 1932, was powered by a 240 hp (180 kW) Argus As IOC inline engine. The second prototype, designated Arado Ar-66-b, was generally similar except that it had twin wooden floats, the rudder being extended beyond the bottom of the sternpost and faired into the rear fuselage by the addition of a ventral fin. Ten production Arado Ar-66-b aircraft were built subsequently. When Rethel left to join Bayerische Flugzeugwerke, as the Messerschmitt company was then named, Dipl. Ing. Walter Blume assumed responsibility for development of the Arado Ar-66-a, which entered series production as the Arado Ar-66-c, initial deliveries being made to the Luftwaffe in 1933. The Arado Ar-66-c continued to serve with Luftwaffe training schools after the outbreak of World War II, and as late as 1943 it was pressed into service, together with the Gotha Go-145 trainer, to equip the night ground-attack Storkungkampfstaffeln on the Eastern Front, armed with 4 lb and 9 lb (1.8 and 4 kg) anti-personnel bombs.
Maximum speed of Arado Ar-66 (66c version) was 210 km/h (130 mph or 100 knots). Service ceiling was 4,500 meters (14,800 feet). Range was 716 kilometers. Wingspan was 10.10 meters (33 ft 1 in) and length was 8.30 meters (27 ft 3 in). It was powered (66c version) by single Argus As 10 C eight-cylinder air cooled inverted V-8 engine (240 hp or 180 kW).
source. Axis Aircraft WWII, Malooney 1984, WWII Ekciklopedia – 1999, Zaporozje