Occupying a unique
position in Soviet aviation history, the Polikarpov U-2 primary trainer
biplane had an inauspicious start. The U-2TPK prototype, which appeared
in early 1927, had been built to achieve economy in repair and
maintenance, the wings comprising four identical thick-section
interchangeable rectangular panels with square tips. Similarly, a
common control surface was used for ailerons, elevators and rudder. The
result was a biplane with very poor flight characteristics. It had thus
to be re-designed, appearing as a neat, manoeuvrable biplane having
staggered single-bay wings with rounded tips, conventional cross-axle
landing gear, and tandem open cockpits for an instructor and pupil.
Most noticeable in the new aircraft was a much larger rudder. Powered
by a 100 hp (74.6 kW) radial engine, the new prototype made its first
flight on 7 January 1928 piloted by M.M. Gromov. An immediate success,
showing great longitudinal stability making it virtually impossible to
spin out in flight. It was placed in quantity production, with
deliveries starting in 1928, and by the time of the German invasion of
the Soviet Union in June 1941 over 13,000 had been completed.
Built in large numbers in Poland as the CSS-13, the Polikarpov U-2
(known as the Po-2 after the designers death in 1944) was used in a
wide variety of roles both military and civil. Built in greater numbers
and variants than any other aircraft in history.
Though its principal
role was primary training, the U-2 was soon modified as a light
passenger transport, air ambulance and agricultural aircraft.
Production continued on a massive scale during World War II, and the
U-2 took on an even wider range of duties, including liaison, light
attack, night nuisance raider and propaganda aircraft complete with
microphone and loud-speaker.
death, on 30 July 1944, the U-2 was redesignated Po-2 in his honour,
and post-war it continued in production in the Soviet Union for several
years. Trainer and ambulance variants were built on a large scale in
Poland from 1948 to 1953. Po-2s served with many Soviet allies and a
small number still remain in flying condition in the Soviet Union and
several other countries. The total number of aircraft built is credibly
reported to be in excess of 33,000, with a number possibly approaching
near 40,000. Actual numbers built are almost impossible to calculate
since many were built by aeroclubs, repair shops and even enthusiasts,
with small scale production continuing until at least until 1959.
The Night Witches
In 1942 the Soviet
Union formed three regiments of women combat pilots. The 586th Fighter
(IAP) Regiment (Yak-1s and later Yak-7Bs), the 587th Day Bomber
Regiment (Petylakov PE-2s) and the 588th Night Bomber Regiment (Polikarpov
Po-2s). The 'Night Witches' were the women of the 588th Night Bomber
Regiment. All of the mechanics and ordnance loaders of this regiment,
as in the 586th Fighter (IAP) and the 587th Day Bomber Regiment, were
Trained for six months
at the town of Engels on the River Volga near Stalingrad, they flew
obsolete Polikarpov Po-2 biplanes, that were otherwise used as
trainers. Generally unarmed they carried a variety of droppable
ordnance consisting of bombs/grenades (even Molotov Cocktails) thrown
from the aircraft by the observer, and on later aircraft, underwing
racks for up to 264 lbs (120 kg) of bombs or four RS-82 rockets. Like
most Night Bomber Regiments, they were nuisance raiders with targets
usually of little strategic importance, but the psychological effect of
the terror raids had a major effect on the Germans who soon gave the
women pilots the nickname of Nachthexen or Night Witches,
presumably because of the fact that they were women and flew wooden
aircraft at night.
Because of the
aircraft's wooden frame and fabric covering construction combined with
the low heat signature of the small 100 hp (74.6 kW) engine, and flying
very low to the ground, they were difficult (if not impossible) for
radar equipped night fighters to detect them. Flying close to the
target and then cutting their engines and gliding in to attack, also
added to their terrifying effect.
bombing was very difficult to do, considering the low performance of
the Po-2 biplanes was even less than most World War I fighters. Very
slow, but it was also very manoeuvrable. When a German fighter tried to
intercept it, the Russian plane could turn violently and nimbly at a
speed much less than the pursuing fighters stalling speed, requiring
that the German make a wide circle to come in for another pass. Then he
was again met with the same evasive tactic, time after time, hoping
that in frustration he would break off the attack altogether.
The Germans later
devised a defence to their attacks, that the Russians later called a
'Flak Circus' wherein searchlights and flak guns encircled probable
targets. The 'Night Witches' adopted a dangerous tactic in which,
flying in formations of three aircraft, the first two aircraft would
fly into the target drawing the searchlights and flak onto themselves
and away from the third aircraft that would attack the target. After a
successful attack they would regroup and switch places with each
aircraft taking its turn as the bait.
The Soviet women bomber
pilots earned in total 23 Hero of the Soviet Union medals and dozens of
Orders of the Red Banner. Altogether, the Po-2 pilots flew more than
24,000 sorties and dropped 23,000 tons of bombs earning their place in
(U-2AP/U-2AO) "Aeropyl" - A single-seat agricultural duster aircraft,
built in sub-types U-2AP and U-2AO from 1930, with 551 lbs (250 kg)
chemical hopper in rear fuselage. Modified landing gear incorporated
double wheels (usually a second rim welded to the original) to assist
the aircraft when operating on unprepared and often wet fields.
Post-1944 it continued in production and use as Po-2A powered by 115 hp
(86 kW) M-11K engine (9000 aircraft).
Polikarpov U-2G - A
one-off experimental model with all controls linked to the control
Polikarpov U-2KL - Two
special aircraft with rear cabin having a bulged canopy appearing in
(U-2VOM-1) - Light Shturmovik. A large number of pre-war aircraft
converted for close-support military role from 1941 onwards, plus new
production. Armed with one 7.62 mm (0.30 in) ShKAS machine-gun on a
ring mounting over rear cockpit, and racks for 264 lbs (120 kg) of
bombs, plus rails for four RS-82 rockets. It had a high reputation
among Soviet troops and earned nickname Kukuruznik or
corn-cutter, resulting from its successful low-level operations. An
alternative designation was U-2VOM-1.
Polikarpov U-2LNB - A
wartime production from 1941 onward with the offensive load raised to
441 lbs (200 kg). The designation translates as light night bomber, and
the type often carried flares or a searchlight and usually had a
silencer attachment for engine exhaust.
Polikarpov U-2LPL - A
prone-pilot research development of 1935.
Polikarpov U-2M (MU-2)
- Alternative designation MU-2 tested in 1931. The first of several
floatplane versions with large central float and two wingtip
stabilising floats. No version built in large numbers.
Polikarpov U-2NAK -
Light artillery observation and reconnaissance variant with an observer
and provided with an army radio.
Polikarpov U-2S (U-2S-1
and U-2SS) - Limited series built from 1934 with the rear cockpit being
replaced by enclosed cubicle for medical attendant and compartment for
stretcher case, with hinged top decking over patient. Later had windows
installed. Other versions known as U-2S-1 and U-2SS (Sanitamyi
Samolyet, or ambulance aircraft).
Polikarpov U-2SP -
Third open cockpit installed with other cockpits relocated. Built
between 1934 and 1939, mostly for Aeroflot for use as passenger and
mail delivery aircraft. Survivors were impressed in wartime service for
liaison duties (861 aircraft).
Polikarpov U-2SPL - A
limousine model with rear cabin for two passengers in place of rear
Polikarpov U-2UT -
Built in limited numbers from 1941, mainly for training and powered by
the 115 hp (86 kW) Shvetsov M-11D engine.
Polikarpov U-2VS - A
basic Soviet air force aircraft with large numbers produced and used by
senior personnel for wartime liaison flights. Over 9,000 were in
service for liaison duties in 1945, by then redesignated Po-2VS.
Polikarpov U-3 - A
development by N.G. Mikhelson and A.I. Morshchikhin in 1934 as a better
flying training model with 200 hp (149 kW) M-48 engine. In no way
superior to basic U-2.
Polikarpov U-4 - A
cleaned-up model of U-2 with slimmer fuselage developed by N.G.
Mikhelson but not built in quantity.
Polikarpov Po-2GN - A
'voice from the sky' propaganda aircraft with loudspeaker for
addressing enemy ground troops, built from 1944.
Polikarpov Po-2L - A
limousine version with enclosed passenger cabin and access door on port
Polikarpov Po-2P - A
wartime floatplane, built in limited numbers only.
(Po-2S-1/2/3) - A wartime ambulance aircraft, Po-2S-1 was similar to
pre-war ambulance aircraft. The Po-2S-2 had the M-11D engine, and
Po-2S-3 carried two underwing containers each with stretcher patient.
Alternative designation for this last variant was Po-2SKF.
Polikarpov Po-2ShS - A
staff liaison machine built from 1943 onwards with a new fuselage with
an enclosed cabin for pilot and two or three passengers.
Polikarpov Po-2SP - A
specialised post-war version, used for geographic survey and air
Polikarpov RV-23 - An
N.G. Mikhelson float derivative of the U-2 for seaplane altitude record
attempts in 1937. Built in small numbers with the 710 hp (529 kW)
Wright R-1820-F3 Cyclone radial engine.
Polikarpov CSS-13 - The
designation for the Polish version, some with glazed cabin over crew
Polikarpov CSS-S-13 -
The Polish ambulance version with a canopy over the cockpits for pilot
and medical attendant and an enclosed section for a stretcher patient
to the rear.
Polikarpov E-23 - A
1935 research version for inverted flight testing.
Experimental - Many
experimental versions were built including one to the Rudlicki
'butterfly' tail and another aircraft re-engined with a Siemems Sh 14
Type: Two Seat
Multi-Purpose, Liaison, Night Nuisance Raider, Ground Support,
Ambulance & Trainer
Pilot & Gunner/Observer
Nikolai Nikolayevich Polikarpov
State Industries (Polikarpov Design Bureau)
100 hp (74.6 kW) Shvetsov M-11 5-cylinder air-cooled radial engine
driving a two-bladed fixed pitch wooden propeller.
Maximum speed 97 mph (156 km/h) at sea level; service ceiling 13,125 ft
(4000 m); landing speed 40.3 mph (65 km/h); flight endurance 3 hours 30
Range: 249 miles
(400 km) on internal fuel.
equipped 1,400 lbs (635 kg) with a maximum take-off weight of 1,962 lbs
(890 kg). Wing loading 5.3 lbs/sq ft (25.8 kg/sq m); power loading 18.9
lbs/hp (8.6 kg/hp)
37 ft 4 3/4 in (11.40 m); length 26 ft 9 3/4 in (8.17 m); height 10 ft
2 in (3.10 m); wing area 356.86 sq ft
(33.15 sq m).
(Optional) One 7.62 mm (0.30 in) ShKAS machine-gun on ring mounting in
flight (U-2TPK) early 1927; first flight (redesigned prototype) 7
Soviet Union, Poland.