via Wikipedia infobox
The PTO-4 was an Estonian-designed military training aircraft of World War II.
In 1938, the Estonian aviation engineers Voldemar Post, Rein Tooma and Otto Org, previously responsible for the PON-1 trainer, designed and built the PTO-4 training aircraft. It was a two-seat low-winged monoplane powered by a De Havilland Gypsy of 120 hp, with a fixed undercarriage that could be fitted with wheels or skis. The aircraft could fly at a maximum speed of 245 km per hour and had a ceiling of 5,000 meters. On 12 October 1938, the PTO-4 was taken into service of the Air Force.
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