World War II , and subsequently captured by German troops, 1941. From the beginning, the U-2 became the basic Soviet civil and military trainer aircraft, mass-produced in a "Red Flyer" factory near Moscow. It was also used for transport, and as a military
liaison aircraft, due to its
STOL capabilities. Also from the beginning it was produced as an agricultural aircraft variant, which earned it its nickname
Kukuruznik. Although entirely outclassed by contemporary aircraft, the
Kukuruznik served extensively on the
Eastern Front in
World War II, primarily as a liaison,
medevac and general-supply aircraft. It was especially useful for supplying
Soviet partisans behind the German front line. Manufacturing of the Po-2 in the USSR ceased in 1949, but until 1959 a number were assembled in Aeroflot repair workshops. The first trials of arming the aircraft with bombs took place in 1941. During the
defence of Odessa in September 1941, the U-2 was used as a
reconnaissance aircraft and as a light, short-range, bomber. The bombs, dropped from a civil aircraft piloted by Pyotr Bevz, were the first to fall on enemy
artillery positions. From 1942 it was adapted as a light night ground attack aircraft. Nikolay Polikarpov supported the project, and under his leadership, the U-2VS (
voyskovaya seriya – Military series) was created. This was a light night bomber, fitted with bomb carriers beneath the lower wing, to carry 50 or 100 kg (110 or 220 lbs) bombs up to a total weight of 350 kg (771 lb) and armed with
ShKAS or DA machine guns in the observer's
cockpit. Luftwaffe
fighters found it extremely hard to shoot down the
Kukuruznik because of two main factors: the pilots flew at treetop level where they were hard to see or engage and the
stall speed of both the
Messerschmitt Bf 109 and the
Focke-Wulf Fw 190 was similar to the U-2s maximum speed, making it difficult for the fighters to keep a Po-2 in weapons range for an adequate period of time. The success of the Soviet night harassment units inspired the Luftwaffe to set up similar
Störkampfstaffel "harassment combat squadrons" on the Eastern Front using their own obsolete 1930s-era, open cockpit biplanes (most often the
Gotha Go 145 and
Arado Ar 66 biplanes) and parasol monoplane aircraft, eventually building up to larger
Nachtschlachtgruppe (night attack group) units of a few squadrons each. The U-2's 5-cylinder engine had an unusual exhaust manifold arrangement that gave the engine a peculiar rattling or popping sound which made the airplane easily identifiable even at night. German soldier Claus Neuber listed in his war diary six different German nicknames for the plane, the most common of which were
Nähmaschine (sewing machine) or
Kaffeemühle, (coffee mill), both due to the distinctive engine sound. The fabric and wood construction of the airplane made it extremely vulnerable to catching fire when hit by tracer rounds, resulting in a Russian nickname of
Kerosinka, or kerosene lantern. Finnish troops called it
Hermosaha (Nerve Saw) as the engine sound was similar as a band saw.
Korean War North Korean forces used the Po-2 in a similar role during the
Korean War. A significant number of Po-2s were fielded by the
Korean People's Air Force, inflicting serious damage during night raids on
United Nations bases. During one such attack, a lone Po-2 attacked
Pyongyang Air Base. UN forces named the Po-2's nighttime appearance
Bedcheck Charlie and had great difficulty in shooting it down – even though
night fighters had
radar as standard equipment in the 1950s. The wood-and-fabric material of the Po-2 had only a small radar cross-section, making it hard for an opposing fighter pilot to acquire their target. As Korean war U.S. veteran Leo Fournier remarked about "Bedcheck Charlie" in his memoirs: "... no one could get at him. He just flew too low and too slow." On 16 June 1953, a
USMC AD-4 from
VMC-1 piloted by
Major George H. Linnemeier and
CWO Vernon S. Kramer shot down a Po-2, the only documented Skyraider air victory of the war. The Po-2 is also the only biplane credited with a documented jet-kill, as one
Lockheed F-94 Starfire was lost while slowing down to – below its stall speed – during an intercept in order to engage the low flying Po-2. ==Variants==