U-2, Po-2 trainer by N.N.Polikarpov

Po-2 photo from the European Airshow Page by .

This classic primary trainer has one of the world richest aircraft histories. Since the first series aircraft flight (January 7, 1928) it was widely used for more than 35 years. After death of N.N.Polikarpov U-2 was renamed as Po-2 (Polikarpov, the second model). Despite retirement of Po-2 started in June 1959, it service continued. Some even were built of spares by aeroclubs. The F-AZPO is still flying over Belgium with its original engine...

Dozens of production and experimental variants were built. Among them - several agricultural, paramedic and limousine. During The Great Patriotic War peaceful biplane turned into terrifying night bomber. German fighters were praised with Iron Cross for shooting down this small plane! All those roles (not planned during aircraft development!) prove superior quality of the design.

Aircraft F-AZPO in the 'Night Witches' bomber group camouflage is owned and flown by .
(Photo from the European Airshow Page by ).

As a trainer, it was intended to replace aging U-1 trainer and other old machines used in this role. As industry recovered from the Civil War wounds, unified primary pilot training schedule became a necessity. Old 120hp M-2 (used on the U-1) was unreliable and had too short lifetime. But new generation 100hp M-11 was in production since 1926, specially intended for trainer aircraft.

Requirements to new trainer were formulated by NTK UVVS under supervision of S.V.Ilyushin. Aircraft had to be safe to fly, with speed no more than 120km/h. This allowed to exclude non-productive high-speed taxing on U-1 with 'stripped' wing. After finishing the U-2 courses, pilots had to perfect advanced P-2 with 300hp engine.

Success came soon, but start was disappointing. First U-2 was built with thick wing (with high lift at low speed in mind), had very simple and strong airframe. But it turned into failure.

Aircraft was rebuilt. It had numerous similarities to other aircraft designed by N.N.Polikarpov team. The most distinctive difference was very large rudder. U-2 was also airdynamically refined compared to its predecessors.

46k b/w U-2 from "History of aircraft construction in the USSR", Vol.1 p.389

First flight was performed by M.M.Gromov on January 7, 1928. Standard skis from the U-1 were installed. Later other pilots tried U-2 in air, and everyone was impressed by excellent handling of new aircraft.

U-2 had feature absolutely new for the time - static longitudinal stability. In case of large climb angle and following speed lose aircraft normally stalled, with risk of lost control and spin. U-2 just dropped nose and than continued steady descent (in case of low engine power), or accelerated and continue climb. Aircraft could be send into spin only intentionally (and it was not so easy!). And it was enough to hold controls in neutral position to get out of spin. It was even possible to let U-2 fly without hands on controls...

In 1928 aircraft was presented on Berlin Airshow. Mass production started in 1930 at 'Krasnyj Letchik' (The Red Pilot) factory and ended in 1953, when requirements to primary pilot training changed again. More than 33,000 were build. Actual number is almost impossible to figure out, because many were built by aeroclubs, repair shops and even enthusiasts. Small scale production lasted at least until 1959! Undemanding to service, U-2/Po-2 could operate from any sufficient opening.

In September 29 - October 6 1932 U-2 flown by V.K.Gribovskij tugged G-9 glider (pilot V.A.Stepanchenok) along 1700km route Tambov - Voronezh - Ejsk in 19 flight hours.

Predecessor(s)	Modifications	Following Designs
U-2 with thick wing	So many... placed on separate page;	U-3	NV-5

References	Links
"History of aircraft construction in the USSR", Vol.1 p.387-391; 'Po-2 aircraft and its modifications' by V.M.Lipatov. Moscow, Aeroflot, 1953. 'Samoliot U-2' (U-2 aircraft) by N.M.Lebedev, Moscow, 'Voenizdat', 1936.	Po-2 at Virtual Aircraft Museum U-2 at Finland; Po-2, Polikarpov Polikarpov U-2	U-2, Polikarpov Completely operational Po-2 owned by Yves Dumortier! Soviet female pilots on WWII and their aircraft by Rolando Silva U-2 of Normandie-Niemen Picture gallery of museum treasures