Tu-2 “Bat”: post-WWII service

The Tupolev Tu-2 “Bat” (it’s NATO reporting name) was one of the best warplanes of WWII, but is generally not well-known outside the USSR. A fast light bomber, it was remarkably agile, enough to out-maneuver lower tier fighters, and it’s closest comparison during WWII would probably be the German Ju-88. The Tu-2 also had a long and eventful career after WWII.

(Top: A Soviet air force Tu-2 “Bat” in combat during WWII. Bottom: A Polish navy Tu-2 “Bat” with Warsaw Pact Northern Group exercise markings in 1956.)

Origin

In April 1939, Josef Stalin mentioned a desire for a four-engined strategic bomber, which would have high speed and also somehow be capable of both dive-bombing missions and naval torpedo strikes. The requirement was range enough to hit the Royal Navy base at Scapa Flow, with enough speed to outrun fighters and accuracy to hit small targets in a dive. The Tupolev design bureau submitted it’s “samolet 57” (samolet means airplane in Russian) concept. Stalin’s request was, of course, absurd and none of the submitted designs were ever built. However the Soviet air force was impressed enough that it requested Tupolev rework it’s concept into a twin-engined tactical bomber, and this became the Tu-2.

(Andrei N. Tupolev and the Tu-2.)

Basic description

The Tupolev Tu-2 was 45’3″ long with a wingspan of 61’10”, and powered by two air-cooled Shvetsov ASh-82 radial piston engines, each delivering 1,850hp. The engines could self-start using the AK-50M compressed air system, or a ground starter. The Tu-2’s maximum speed was 281kts and the ceiling was 29,856′.

(The front of a Tu-4’s engine nacelle with maintenance doors opened. The nib in the center of the prop spinner is a Hucks dog for engaging backup ground starters.)

The “Bat” had a 4-man crew: pilot, navigator (who also manned the cockpit machine gun), radioman (who also manned the dorsal gun), and a fourth crewman nicknamed “strela” (the arrow) who manned the ventral tail gun position.

(A preserved Tu-2 at the Monino museum near Moscow. This plane has later-production features such as single rear windows instead of the three small ones, 4-bladed propellers, and two landing lights. This photo gives a good view of the engine nacelle design, with the air intake on top and oil cooler underneath. The landing gear retracted into the hollow rear of the nacelle by mechanical scissors.)

Except for fabric portions on the rudders and flaps, the Tu-2 was all-aluminum. The rear stabilizer had 7° dihedral, adding to the plane’s maneuverability. The wings had two internal spars and were strong. The underside of the wings had dive brakes for dive-bombing use, although this was not the Tu-2’s primary intended role. On Tu-2s built after WWII the dive brakes were omitted and others had them removed to lighten the plane.

(The lower portion of the nose allowed the pilot to observe below the plane.) (photo via Polish Aviation Museum)

(The Tu-2 was intended to be flown off rough grass airstrips so the landing light was moved from the gear strut to a flip-down position in the underside of the port wing. After WWII, a second light was added.) (Russian Federation archives photo)

The fuel was carried in 14 separate tanks, which were self-sealing. As the fuel was consumed, the tanks could be filled with engine exhaust to prevent a bullet hit from igniting vapors.

(Fuel system diagram of a Tu-2.) (Russian Federation archives photo)

The only real complaints was the lack of modern navigational gear which lessened the realistic range, and a high workload for the pilot and navigator. Otherwise the Tu-2 was regarded as a world-class warplane.

(The pilot sat offset to port and the navigator to starboard.)

The Tu-2 was rated to a maximum 3,300 lbs of bombs. The loadout options were 1) One FAB-1000 (2,205lbs) bomb in the bomb bay plus two FAB-250 (551 lbs) bombs externally 2) Two FAB-500 (1,100lbs) bombs or BRAB-500 bunker-piercing weapons externally 3) Six FAB-250 bombs; four in the bomb bay and two externally 4) Nine FAB-100 (221 lbs) bombs in the bomb bay plus four 55lb anti-personnel weapons under the wings 5) Four FAB-250 bombs in the bomb bay plus eight RS-132 rockets under the wings 6) Two torpedoes or sea mines externally. An OPB-1 bombsight was used.

(The BP-4 system on the “Bat” was a pair of handcranked chainfalls that attached to the landing gear axles and used the engine firewalls as fulcrums. By this, loads up to 1 ton (here a FAB-1000) could be manually loaded. After WWII, this was useful for rebuilding air forces in eastern Europe which were still short of ground support vehicles.)

(The unguided 45-36 entered Soviet navy service just before the start of WWII, and came in high- and low-altitude versions. It weighed 1 ton with a 441 lbs HE warhead, and ran at 39kts for 2 NM in the water. It was the Tu-2’s standard anti-ship weapon it’s entire career, both during and after WWII.)

Two ShVAK 20mm guns were in the wing roots, each with 150 rounds of ammunition. This full-auto gun fired the 20x99mm(R) cartridge and was an effective gun of it’s era. The 20mm wing guns were depressed 2° to make strafing runs easier. The defensive fit was three Berezin UB 12.7mm machine guns, one in the cockpit rear (the navigator had to wiggle around backwards to use it), one in the dorsal mount, and the “strela”s gun in the ventral mount.

(The UB 12.7mm machine gun behind the navigator. This is on an early-model Tu-2, the plexiglass flap had to be opened for using the gun. Later a round armored glass ready-use panel was fitted to the canopy.)

(The dorsal position UB machine gun. The dorsal canopy had to be opened for it’s use, and the gun raised into position. It was aimed by a glass deflection sight (the U shaped object) and fired by a handheld LU-68 trigger unit.)

(The LU-1 flexible belt feed system for the ventral UB machine gun, needed as the gun’s receiver was essentially ‘upside down’ of the intended ingestion direction. The “strela” crewman laid on his belly to use the gun, and aimed via a periscope which is shown as the lightly-drawn tube on the diagram.)

The small available number notwithstanding, the Tu-2 was extremely effective during WWII. It’s range and navigational systems limitations prevented long-range missions, but it was very effective against German rear-area installations such as rail yards and airbases during the 1943-1944 counteroffensive (including the Kursk battle), and the early 1945 push into East Prussia. Throughout the war, naval missions in the Baltic were flown with torpedoes and mines. In April and May 1945, Tu-2s took part in the final battle of Berlin. Adjusted out per capita for the total in use, the Tu-2 suffered the least combat losses of any Soviet warplane of any type in WWII.

The Tu-2 was also used in the USSR’s short participation in the Pacific war. There were at least two “Bat” squadrons in the 9th Air Army which supported the 1945 advance into eastern Manchukuo and northern Korea. Soviet Naval Aviation units flying torpedo-armed Tu-2s flew anti-shipping missions off the Kuril islands and South Sakhalin. Another Tu-2 bomber unit supported a smaller offensive from Mongolia into western Manchukuo. This squadron was remarkable in that it had participated in the battle for Berlin in May, then made an epic move halfway around the world, leapfrogging airstrips in eastern Europe, Russia, and Siberia to Mongolia in time for the August operation.

During WWII, a total of 80 planes were built before Stalin issued a temporary stop-work order in October 1942 to divert all available aircraft production to ground attack and fighter aircraft. In 1943 production was allowed to resume. The Tu-2 remained in production for the rest of WWII, and into the postwar period, with the 2,527th and last Tu-2 being delivered in early 1951.

POST-WWII SOVIET USE

Units of VVS (Frontal Aviation) loved the Tu-2, and it was one of the few WWII types which saw it’s numbers and usage actually increase after WWII’s end. The “Bat” was selected as the interim standard peacetime tactical bomber, and as such began to replace other types as soon as Japan had surrendered. The replacement priority was any remaining pre-WWII designs, then Lend-Leased bombers, then finally Pe-2 “Buck”s. Upgrades were done to the plane’s equipment; for example the AGK-47A artificial horizon was added and RSB-5 radios replaced the WWII RSB-3 sets. Some received spare Lend-Leased SCR-269 radiocompasses which the USSR failed to return to the USA after WWII. Later still, some had SCh-3 IFF systems added to identify them with Cold War-era radars.

(The AV-9VF-21K adjustable-pitch propeller which replaced the original 3-bladed design.)

(Soviet air force Tu-2 bombers two years after the end of WWII. These have the newer propeller design.)

(Soviet navy torpedo attack squadron flying Tu-2s in the mid-1940s.)

A specialized reconnaissance version, the Tu-6, had a protected enclosure for two cameras in the rear area of the former bomb bay but was otherwise the same as a late-war Tu-2. As time went on after WWII, daylight reconnaissance in a piston-powered plane was viewed as increasingly dangerous. The external bomb racks were then used for dropped nocturnal photoflashes; these produced an instant of extremely bright light. The cameras were rigged with photovoltaic cells that automatically operated the shutter when the light was sensed.

(Tu-6 reconnaissance plane in the post-WWII Soviet air force.)

(Line diagram of the Tu-6 reconnaissance version.) (from book OKB Tupolev by Yefim Gordon)

(Close-up of the protected enclosure for the Tu-6’s AFA-33 and AFA-100 cameras with the outer doors opened. The small square hatch to the rear is the radioman’s escape point.) (Tupolev PLC company photo)

The Tu-6 was successful and continued in Soviet use into the 1950s. It was also exported.

Besides frontline squadron use, WWII-veteran Tu-2s were used for a variety of miscellaneous tasks and experimental roles.

(One of the most bizarre warplanes ever was the Tu-2Sh, of which two were made. They carried a pallet of 88 PPSh-41 infantry submachine guns, each with the normal 71-round drum magazine. They also carried two external bombs and a 57mm anti-tank gun in the nose. This photo was taken after WWII in 1946, when experiments with the type were ending.)

Two “Bat”s were converted into Tu-2LL flying testbeds. These had their weapons removed and an attachment fitted to the starboard wing root for an external jet engine. The attachment point was flexible and had several hydraulic pistons, so that the attitude of the engine being tested relative to the plane could be adjusted.

(Tu-2LL with a WWII captured Junkers Jumo 004 jet engine. The nacelle barely cleared the runway by inches and it was challenging to takeoff or land these loads.) (Tupolev PLC company photo)

(The Tumansky RD-10 was a Soviet near-copy of the Jumo 004. The prototype was tested on a Tu-2LL This engine design was later used on the Yak-15.) (Tupolev PLC company photo)

(In this airbrushed Cold War photo, a Tu-2LL is carrying a prototype Klimov VK-1 which was used on a number of types including the MiG-15, Il-28, and the Tu-2’s naval replacement, the Tu-14 “Bosun”.)

The Tu-2LLs were also used for flight trials with the 16Kh cruise missile. This was powered by two pulsejets, and was developed in the late 1940s by the Chelomei bureau using captured German V-1 buzz bombs. The Tu-2 itself was never considered as an operational plane for this missile, just a trials testbed. The 16Kh was eventually rejected by the Soviet military.

(Tests with the 16Kh were even more dangerous to the two Tu-2LL planes than engines. Engines being tested were shut off for takeoff and landing and were then just metal objects. But with the missile, which was just as close to the runway, at takeoff it was full of flammable jet fuel.)

(Tu-2LL testing an aerodynamic shape in 1948.) (Russian Federation archives photo)

Besides the 16Kh, the Tu-2LLs were used to test less exotic new bombs and rockets, and also to launch supersonic scale models. The two planes were quite useful.

One Tu-2 was converted after WWII into a prototype commando insertion plane. The former bomb bay was modified to carry a GAZ-67 jeep, which could be paradropped. It was proposed that a three-plane formation of these aircraft could insert a specops platoon; one carrying the jeep and the other two paratroopers (the jeep could not be paradropped with people inside it). The Tu-2s, then devoid of all combat weight, could make a fast escape. Tests in 1949 showed that the jeep caused an unacceptable amount of drag and the idea was dropped.

(Tupolev PLC company photo)

At least two, and maybe three, Tu-2s were converted into air-to-air refueling planes. For certain, two were converted into both tankers / recipients using the probe & drogue method. Another (it may have been a reconversion of one of the first two) was modified for the tip-to-tip method. Air-to-air refueling was an extremely new and uncharted technology in the early post-WWII era and the knowledge gained was valuable.

(One of the Tu-2 probe & drogue tankers refueling the other in the late 1940s.)

(A Tu-2 tanker refueling a Yak-15 “Feather” fighter using the tip-to-tip method in 1949. No fuel was actually transferred during this test, it was just an experiment to see if the method was suitable.)

Other one-off, ad hoc modifications were also done. For example, one Tu-2 was used as the tow plane for gliding trials of captured German Me-163 Komet interceptors after WWII.

VVS regiments actively flying Tu-2s began converting to other types in 1950. The Tu-2 lingered on in reserve formations through the 1950s, and served in miscellaneous test and support roles. The last Soviet “Bat” was retired in 1955.

(Tu-2s of the post-WWII Soviet military during a 1947 exercise.)

FOREIGN USERS AFTER WWII

Bulgaria

Bulgaria was a major user of the Tu-2 after WWII. Deliveries from the USSR began in 1946 and eventually, 30 planes were imported. All were assigned to the 25th Mine & Torpedo Regiment, flying out of Balchik airbase. Curiously, into the early 1950s, this regiment also still flew five WWII ex-Luftwaffe Fw-189 Uhu reconnaissance planes to find targets for the “Bat”s, and four Fw-58 weather planes.

(Bulgarian Tu-2 in early-1950s camouflage.) (artwork from Wings Palette website)

In the Warsaw Pact’s general war plan, this regiment was assigned anti-shipping strikes in the western Black Sea. In the late 1940s and early 1950s, opposition there was judged to be moderate, as the Turkish air force was flying Spitfires and P-47 Thunderbolts, themselves WWII-vintage designs.

Despite it’s increasing obsolescence, the WWII-vintage Tu-2 “Bat” was liked by Bulgarian pilots. They served until 1955, when they were replaced by MiG-17 “Fresco” jet fighters at the same time WWII-style anti-ship torpedo attack training was discontinued in Bulgaria.

(photo by Joop de Groot)

China

The Chinese PLAAF (People’s Liberation Army Air Force) received 62 Tu-2s in 1949, all of them coming from the withdrawing Soviet garrison in Manchuria and about half of them being trainers. This batch was the type used in the final stages of the Chinese civil war on the mainland.

In 1949, the PLAAF’s 829th Mixed Regiment at Nanking was flying 10 Tu-2 “Bat” bombers alongside 25 Il-10 “Beast” attack planes. These were used in combat against nationalist forces. One PLAAF “Bat” was shot down by a Soviet “joint anti-aircraft training unit” near Shanghai after the gunners mistook it for a nationalist B-25 Mitchell. After the nationalists had been driven off the mainland, PLAAF Tu-2s were used in anti-shipping missions in the Straits Of Formosa.

In 1952, 311 refurbished Tu-2s, all of the bomber version, were delivered. These joined those of the 1949 batch which had not been destroyed in the Chinese civil war or Korean War.

(This PLAAF Tu-2 “Bat” took part in combat against nationalist island garrisons after they had been driven off the mainland.) (artwork from Wings Palette website)

China formally the Korean War in late October 1950. The PLAAF used the Tu-2 in combat almost immediately. By now, American forces were largely using postwar jets, and the “Bat” was obviously at a serious disadvantage. Typically, they were used in one- or two-plane escorted raids, and did not really accomplish much.

(Artwork showing a North Korean Yak-9 “Frank” fighter – itself a WWII design – escorting a Chinese Tu-2 “Bat” bomber during the Korean War.)

The USA claimed 9 Tu-2s shot down in air-to-air combat over Korea. Because Chinese (and occasionally, Soviet) crewmen sometimes flew in North Korean-marked planes, and North Koreans in PLAAF-marked planes, no country was assigned to shootdowns. The last confirmed downing of a Tu-2 was on 30 November 1951, by a F-86 Sabre jet fighter of the US Air Force’s 335th Fighter Squadron. From 1952 until the war’s end in July 1953, Tu-2s were rarely seen.

(A PLAAF Tu-2 in 1953 wearing the “Manchurian” color scheme which used throughout the Korean War.) (artwork from Wings Palette website)

In the 1990s, a joint Russian-American team tried to reconcile reports of Korean air combat. It determined that four of the nine Tu-2 kills were certain, and the other five possible.

(Chinese Tu-2 “Bat” crewmen during the Korean War.)

The “Bat” was still to see more combat in Chinese colors. In September 1954, the mainland communists began bombarding the small offshore island of Quemoy, in preparations for an invasion. Around two dozen Tu-2s were assigned to the Quemoy strike force. At the same time, a smaller number of “Bat”s were assigned to bomb an even smaller offshore island, Yijiangshan. These few Tu-2s were busy, flying 72 missions against Yijiangshan in October and November, before the nationalists withdrew what remained of their garrison from the island to Taiwan and abandoned it to to the communists.

In March 1959, a large anti-Chinese insurrection broke out in Tibet. This barely-known brief conflict actually resulted in significant Chinese casualties in the eastern part of Tibet. Now 14 years past the end of WWII, Tu-2s were instrumental in a massive series of air raids against Chagra Pembar which destroyed most of the guerilla units.

(A Chinese Tu-2 on the runway in the 1950s; note the MiG-15 fighter jets in the background.)

By the mid-1960s, the Tu-2 was still in Chinese use, now alongside H-5  jet bombers, and long overdue for replacement. The last four planes of the original 1949 delivery were mercifully retired in 1965. Mao’s disastrous Cultural Revolution, which began in 1966, retarded modernization of the Chinese military and the old WWII bombers delivered in 1952 continued in service, now hopelessly obsolete.

(Derelict PLAAF Tu-2. On this example, the WWII ventral gun position was deleted and the rear fuselage observation windows covered with sheet aluminum. The WWII wire antenna running from the pitot tube over the cockpit to the rudder is gone, probably because more modern radios had been installed. This plane was later donated to a museum and refurbished.)

There were still PLAAF squadrons flying the “Bat” as late as 1976. Thereafter it was only used in reserve, secondary, or test roles. The final Chinese Tu-2 overall was finally retired in 1982. China was the last country in the world to retire the “Bat”.

(Probably taken in the 1980s or early 1990s, this airstrip near Tangshan, China housed a collection of obsolete types including a Tu-2, to the left of the transport’s nose. Other types seen are La-9, MiG-9, Yak-11 and MiG-15 aircraft of the Korean War era, along with MiG-17, MiG-19, and J-7 fighters of the later Cold War, plus a P-61 Black Widow and P-47 Thunderbolt captured from the nationalists.)

Hungary

The postwar Hungarian air force received 35 Tu-2s in 1951. Hungarian pilots called the Tu-2 “túzok”, Hungarian for the flightless bustard bird. Túzok was both a word pun on Tu-2 and a commentary on these WWII planes themselves, which were in bad shape when they arrived. All were warehoused veterans of WWII operations, few had been overhauled prior to transfer, and at least two had unrepaired damage from German AA guns.

(A “túzok” undergoing repairs.) (Hungarian MoD photo)

(This OD green / sky blue scheme is how the Hungarian Tu-2s appeared at the time of the 1956 Soviet invasion.) (artwork from Wings Palette website)

Hungary’s Tu-4s did not take part in the November 1956 anti-Soviet uprising. The Hungarian air force in general limited itself to reconnaissance flights. The commander of the bomber squadron kept his pilots in their barracks so his unit wouldn’t get involved at all.  After the Soviet invasion quashed the uprising, the USSR completely disbanded the Hungarian air force. Although they had not attacked the invading Soviets, the USSR felt the whole air force was “politically suspect” for either taking a wait-and-see attitude, or actively ignoring communist calls for air support. It was not until almost a year later that an army air wing was reformed, but by then, the Tu-4s had sat unattended almost a year including a winter, and had deteriorated beyond repair.

Indonesia

In 1958, the USA imposed an arms embargo on Indonesia, and the USSR and China (still about a year and a half before their split) stepped in. The Soviets provided  modern Tu-16 “Badger” strategic bombers and a cruiser for the Indonesian navy. Meanwhile the Chinese contribution was more modest, much of it WWII-era equipment including a dozen Tu-2 “Bat” bombers. The Tu-2s were delivered to the Indonesian air force’s 1st Squadron, where the Chinese intended they would replace WWII-veteran B-25 Mitchell tactical bombers bought from the USA before the embargo.

(Indonesian Tu-2 “Bat” just after it’s delivery to the 1st Squadron.)

The Tu-2’s Indonesian career was extremely brief. The planes had all sorts of problems. Much of the Indonesian ground support equipment was American-made and incompatible with Soviet systems. Manuals provided by the Chinese were written under the assumption the planes would be flown at high altitude in cool weather, but Indonesia’s hot, tropical climate altered things like engine RPM settings and fuel consumption. The intense humidity also accelerated deterioration of these WWII aircraft.

(An Indonesian Tu-2 “Bat” in 1954. The national pentagon emblem was applied over the Chinese star with the Chinese bar being hand-painted out. The one- or two-digit Indonesian serial numbers were just painted on top of the four-digit Chinese ones.) (artwork from Wings Palette website)

Only a year after they entered service, the Indonesian Tu-2s were withdrawn. The B-25 Mitchells they were supposed to have replaced, had been maintained in use alongside them and were kept in use after they were gone.

North Korea

North Korea received an unknown number of Tu-2s, probably two dozen, in the late 1940s. They took part in the initial 1950 attack which started the Korean War, bombing South Korean airfields. Several were shot down by AA fire and more were bombed on the ground. One was claimed as shot down by an American jet but this is disputed. For certain, however many were in service didn’t accomplish much.

(North Korean Tu-2 “Bat” with the color scheme in use at the start of the Korean War.) (artwork from Wings Palette website)

Piecemeal replacements were delivered from either China or the USSR (or both) throughout the war, however the type was never numerous. One private intelligence estimate said that 35 Tu-2s were at least nominally in use until 1968. This may however have been confusion with the Il-10 “Bark” which definitely was in service at that time.

(A Chinese museum displays what is shown as a North Korean Tu-2. More likely, it is an ex-PLAAF plane of the early transfers (note the 3-bladed propellers) repainted in North Korean markings. This photo shows the muzzle of the port side 20mm gun in the wing root.)

Poland

The postwar Polish air force received two WWII-veteran Tu-2s from the Soviet Union in 1945. These two planes had been assigned to Soviet units which rolled westward towards Berlin the previous year, and were transferred as-is.

(Polish Tu-2 “Bat” in the late 1940s.)

In early 1950, the Polish navy received it’s first three Tu-2s. They were assigned to the 30th Squadron at Gdynia, and used for maritime reconnaissance over the Baltic sea. One of these crashed, the other two remained in use until 1955 and then as target-towing planes for another two years.

(Polish navy Tu-2 in the mid-1950s.) (artwork from Wings Palette website)

In 1949-1950, a larger buy for 33 “Bat”s was delivered to the Polish air force. These had been refurbished in the USSR prior to transfer and were to the best postwar upgrade standards. Eight of the planes were factory-new. These Tu-2s were assigned to the 3rd and 7th Aviation regiments. At the same time, three Tu-2UTB trainers were delivered to the 1st Bomber Training Squadron of the Polish air force academy at Deblin.

(Polish air force Tu-2 in 1957. The ventral machine gun had been removed from it’s position by this point. This plane has all the postwar upgrades including the new propeller, single round fuselage window, and second landing light.)

(Polish navy Tu-2 aircrew in 1957.)

The Tu-2 was moderately regarded in Poland. There were few complaints with the aircraft itself, however there was a general desire to move on to more modern types and by the mid-1950s, the “Bat” was viewed as a retrograde step. The two planes which had been delivered in 1945 amazingly were kept going until 1957. Of the larger 1950 order, some (along with the naval planes) remained in use until 1962. The replacement in Polish service was the Il-28 “Beagle” jet bomber.

(A disarmed Tu-2 which was used as a training plane at Deblin for air force officers headed to jet bombers. All weapons are removed and a Cold War-era RARK-5 radiocompass is fitted under the cockpit.) (artwork from Wings Palette website)

(The Polish air force ejection seat training Tu-2.)

(This was the Polish navy’s final “Bat”, which was used as an AA target tow in the end. It was then donated to a museum.) (photo via Polish Aviation Museum)

Romania

Romania received only a tiny number, six in all, of Tu-2s after WWII. Two were bombers, two were Tu-2UTB conversion trainers, and two were of the Tu-6 reconnaissance version. All were used ex-Soviet air force planes, and all were delivered in 1950.

This small number was nowhere near enough to equip even a single squadron, and it’s unknown why a nonsensical quantity was added to the Romanian air force’s spare parts burden. The planes were assigned to Divisia 68 at Tecuci airbase, near the Soviet border. They served in an odd mixed unit which included two WWII-vintage German He-111 bombers, still in Romanian service in 1950, and ten Il-28 “Beagle” jet bombers.

The Romanian “Bat”s were almost never displayed or photographed. They were withdrawn from service in 1955, having accomplished very little.

POST-WWII DEVELOPMENTS

The SDB

The SDB (a Russian acronym for “fast day bomber”) was an effort to keep the Tu-2 current against improvements in Axis fighters. Two prototypes were built. The first was completed during WWII using a used Tu-2 airframe mated with AM-39 engines. It was only 2% faster than a regular Tu-2 but the idea showed promise. A second prototype was built and tested as WWII was ending. It had a number of new features. The landing gear struts were wider apart, and half-axles replaced the Tu-2’s forks. The fuselage was made as narrow and streamlined as possible. The result was that the second SDB was almost 20% faster than a standard Tu-2.

(The second SDB.)

(The second SDB’s fighter-style cockpit and canopy.)

The SDB project’s final months overlapped the start of the Tu-10 project (described below) and Tupolev cancelled it to avoid duplication. The first SDB prototype was discarded, while the second SDB prototype was recycled as the airframe of the prototype Tu-1 “Frosty”.

The “samolet 67”

With Germany nearing defeat in early 1945, the Tupolev bureau started work on a longer-ranged version of the Tu-2. It was hoped to have at least some ready for the USSR’s entrance into the Pacific war, which Stalin had planned for the autumn of 1945.

The main difference was the use of ACh-30BF engines, which had greater fuel economy than the ASh-82. An AP-2 autopilot was fitted for planned over-water missions, and the crew’s oxygen setup was improved. The dorsal gun was changed to a Berezin B-20 20mm gun.

(The prototype “samolet 67”.) (Tupolev PLC company photo)

A prototype was nowhere near ready by the time the USSR declared war on Japan in August 1945, and flight tests did not start until February 1946, well after WWII’s end. The plane (which never received an official designation) was plagued with constant problems. Also, with WWII’s end, designers were moving on to other projects or retiring. In January 1947 this project was cancelled.

The Tu-1 and Tu-10 “Frosty”: intelligence confusion

These were two separate and distinct aircraft which NATO intelligence erroneously conflated into one, and gave the reporting name “Frosty”.

NATO’s reporting name system predated the alliance itself by a year. During WWII, the USA had assigned a forcewide system of reporting names for Imperial Japanese aircraft, which would be easy for English-speakers to pronounce over a radio and would eliminate confusion from the Japanese type systems. The system came into use in 1942 and was quickly adopted by the Australians and British as well. The system assigned male names to fighters (ex. Nakajima Ki-27 “Clint”, Kawasaki Ki-45 “Nick”), female names to bombers and attack planes (ex. Tachikawa Ki-74 “Patsy”, Nakajima Ki-49 “Helen”), and forestry names to miscellaneous types (ex. Mitsubishi K3M “Pine”, Yokosuka K5Y “Willow”).

This was successful during WWII in the Pacific. After WWII, with the Cold War starting, Soviet military aviation presented a similar issue to the west. Russian names were hard to pronounce for English speakers, and the Soviets themselves did not always publicize the designation of an aircraft at all. Additionally, during WWII and after the various Western allies each had their own way of designating Soviet planes. In 1948, the USA, Canada, and UK formed the Air Standardization Coordinating Committee. ASCC revived the reporting name system, now for Soviet planes. Each Soviet type was given a name, a random word in the English language. The first letter designated it’s role; F for fighters, B for bombers, H for helicopters, and so on. The number of syllables denoted propeller (one) or jet (two). The words selected were (in theory) understandable in English through heavy accents of NATO’s original “core” languages; English, French, and German. The system was successful and continues in use in 2016.

While the system was successful, it depended on the underlying intelligence, which in this case was not altogether correct.

The Tu-1 “Frosty”

In August 1944, the first of three American B-29 Superfortress bombers made an emergency lading in the eastern USSR. As the Soviets were still neutral vs Japan at the time, the bombers were interred (and eventually copied as the Tu-4 “Bull”). This gave the Tupolev bureau a prime opportunity to study the heaviest American bomber up-close. With an eye towards the upcoming rivalry with the USA, work began on an all-weather, day/night “heavy fighter”-type interceptor, similar in concept to the P-61 Black Widow, to take down B-29s in any future war.

The basic WWII Tu-2 airframe made a prime candidate as it’s agility was excellent. In February 1946, the Kremlin granted Tupolev permission to further proceed with it’s project, initially designated “samolet 63P” and later, Tu-1. (In the Soviet system, odd numbers are used for fighters and even for bombers, hence going “backwards” a digit.)

(This painting shows the Tu-1’s radiators for the liquid cooling system in the wing roots, outboard of the 23mm gun muzzle.) (artwork from wp.scn.ru website)

The actual physical airframe was that of the WWII second SDB prototype, which was recycled for the Tu-1 project.The nose of the plane was completely changed to a solid, streamlined shape holding the autocannons and planned Gneis-5S radar. The crew was reduced to three (pilot, radar operator, and rear gunner). The bombsight and much of the bomb bay equipment was deleted, however in an emergency two FAB-500 bombs could be carried. The ceiling was 33,300′ which was about the limit of human endurance in a non-pressurized cockpit and the altitude which the Soviets observed the B-29 often operating over Japan during WWII.

The Tu-1 was powered by two Mikulin AM-43V piston engines with new (AV-9K-22A) four-bladed, high performance propellers. Each engine delivered 1,950hp and the Tu-1 had a top speed of 347kts, only about 90kts slower than a single-seat P-51 Mustang. Development of the AM-43V engine lagged behind the rest of the project, and the two finally delivered in early 1947 were hand-assembled, one-of-a-kind prototypes; still with bugs to be worked out.

The main armament was two Nudelman-Suranov NS-45 45mm autocannons in the nose, each with 50 rounds.

(The Tu-1’s NS-45 autocannons.) (Tupolev PLC company photo)

The secondary armament was two VYa-23 23mm guns in the wing roots, each with 130 rounds. Ideally, the 45mm autocannons would be used against bombers, and the 23mm guns against smaller planes or bombers as well. The two ammunition sizes had different ballistic arcs so it would have been difficult to use them simultaneously. Finally, two Berezin UB 12.7mm machine guns were retained as rearwards armament. In a production version, one of the two would have possibly been deleted to further lighten the plane.

The Tu-1 was 44’8″ long with a wingspan of 61’11”. It first flew on 22 March 1947 and, from a mechanical standpoint, was successful. However the integration of the Gneis-5S radar was problematic and a WWII captured German FuG 220 Lichtenstein radar was installed, with poor results. The Tu-1 met it’s speed requirement and showed both excellent agility and rate-of-climb for a piston plane, with time from runway to 18,500′ being 11 minutes. The runway requirements were 1,837′ for takeoff and 1,984′ for landing.

Tests with the Tu-1 ran throughout the summer of 1947. The intended radar was never fully tested, and the biggest problem was the prototype AM-43V engines. The test team ran them hard and by early October, they were falling apart. On 3 October 1947 the prototype Tu-1 was grounded due to engine concerns. The Mikulin bureau had little interest in continuing the AM-43V as the Tu-1 was it’s only intended mount and jets were clearly the future in any case. While the Tu-1 project was ongoing, the USA was testing the B-36 Peacemaker, which was 13kts faster than the Tu-1 and had a 10,000′ ceiling advantage.

(The Tu-1 “Frosty” fighter.) (Tupolev PLC company photo)

The Tu-1 project was never restarted and the prototype eventually scrapped. However during the flight tests, NATO intelligence became aware of it. Due to it’s fairly advanced nature, and hazard to still-operational WWII vintage bomber designs, it was mistakenly regarded as a likely mass-production type and assigned the “Frosty” reporting name. It was not until after the Korean War that it was realized this fighter had never entered service.

The Tu-10 “Frosty”

Completely unrelated to the ‘first’ “Frosty”, the Tu-10 actually predated the Tu-1. During the final months of WWII, the Soviet air force expressed interest in a “fast tactical daylight bomber” along the lines of the RAF’s Mosquito DH.98 or the Luftwaffe’s Me-410. This plane would perform level bombing missions with agility and raw speed as it’s main survival techniques.

In February 1945, with Germany nearing defeat, a standard Tu-2 “Bat” was re-engined with two liquid-cooled AM-39FNV piston engines in streamlined nacelles, with the radiators buried in the wings. This new engine model was fuel-injected and had a supercharger. It was also selected by MiG for their Iz-234 fighter (which never entered production).

The Tu-2’s rearwards-facing gun mounts were changed to the new VUS-1 and VUB-65 designs. These modifications were successful and tests were continuing as WWII in Europe ended in May.

Because of the country’s communist economic system, the changeover from war to peace was less pronounced in the USSR’s warplane industry than in the USA or Great Britain. Many projects, including this one, continued uninterrupted. In February 1946, the Kremlin gave Tupolev permission to fully proceed with the project, now designated “samolet 68” and later, Tu-10.

(The Tu-10 “Frosty” bomber prototype.) (Tupolev PLC company photo)

The plane was remodeled again. The cockpit was redesigned, and a new, high-strength tail was fitted. The bombardier’s position was redesigned with reduced windows. The newest models of radio and compass were fitted. The engines had been run hard during the early tests and were rebuilt; additionally 4-bladed propellers were fitted. More test flights were successful and in June 1946, a production order was placed.

The Tu-10 was the same length as a Tu-2 but had slightly shorter wingspan. It had the same 4-man crew however the Tu-10 could carry an additional 2,200 lbs of bombs and yet was much faster than a Tu-2, 343kts vs 281kts. The runway requirements were 1,680′ for takeoff and 1,850′ for landing.

Besides the converted Tu-2 and a pre-production example, a total of ten Tu-10s were built in 1946-1947 at the Kuibyshev #1 Zavod factory. The first operational unit began converting from WWII-vintage Tu-2s in April 1947 and the Tu-10 seemed set for a good career.

(The Tu-10 “Frosty” bomber prototype.) (Tupolev PLC company photo)

The Tu-10’s abrupt cancellation was bizarre and is still poorly-documented today. All surviving records show the planes were performing very well. At some time in the early summer of 1947, a “stop work” order was issued from Moscow. There wouldn’t seem to be any military reason. One theory was that the Mikulin bureau was over-worked and viewed the AM-39FNV as expendable, and, in a sort of political “horse trading”, the Tupolev bureau cancelled the Tu-10 airframe to spare Stalin’s wrath on the engine bureau. According to one source in the 1990s, there were an additional three dozen Tu-10s at Kuibyshev in 1947 awaiting backordered engines, so this theory is plausible. A different possibility is that the Soviet air force itself was not thrilled about being issued a souped-up WWII plane in the postwar era, and quietly pulled  strings behind the scenes to kill the Tu-10 without formal documentation that would attract Stalin’s attention.

In any case, the few completed planes continued in service until about 1949-1950 and were then discarded. Meanwhile, NATO intelligence had become aware of the Tu-10 about the same time as the Tu-1. Based on the fact that both were streamlined, high-speed adaptations of the Tu-2 with 4-bladed propellers, it was mistakenly felt certain that the Tu-10 was also a fighter and possibly the prototype of the Tu-1.

Another source of possible intelligence confusion was Tupolev’s own numbers. The “samolet 68” had briefly been designated Tu-4 before Tu-10. The Tu-10 number originally matched with the “samolet 64”; a totally unrelated and never-built WWII design for a long-range heavy bomber in the B-29 category; meanwhile the Tu-4 designation was transferred to the Superfortress clone project which entered service as the Tu-4 “Bull”.

Hence both the Tu-1 fighter and Tu-10 bomber were designated “Frosty” by NATO in 1949 (by which time both projects were already dead, unknown to NATO). It was not until the early 1990s that the error was discovered.

The Tu-8

The post-WWII Tu-8 project, which started in 1946, sort of brought the Tu-2 full-circle to it’s original pre-WWII concept as a long-range bomber. The Tu-8, was supposed to mount the new, powerful Shvestov M-93 engine. However this was not yet ready so ASh-82 engines were used on the prototype.

(artwork from Wings Palette website)

As the firepower of American fighters had greatly increased during WWII the defensive armament was changed to Berezin B-20 20mm guns in the existing positions. The cockpit and dorsal guns were manually controlled while the ventral gun was remote-controlled in a powered turret. Two more B-20s were fixed firing forward.

The prototype’s actual physical airframe was pre-existing. It was the fuselage and wings of a cancelled WWII naval adaptation of the Tu-2 which Tupolev had kept in storage.

The nose of the 5-man Tu-8 differed greatly from the Tu-2. It was enlarged and elongated, to give the bombardier a seated position to use with a OPB-4S bombsight (the unlicensed Soviet clone of the WWII American Norden design). The cockpit was widened, so that the pilot and navigator sat side by side. The dorsal gunner was given a wider area, and the belly gunner was moved to the fuselage interior, operating the remote-controlled ventral turret through two enlarged hemispherical windows, streamlined into the fuselage.

The nose changes shifted the plane’s centre-of-gravity far forward and an enlarged tail was needed. The wings were fitted with de-icing equipment. The engine nacelles were designed with new exhausts, and the late-war 4-bladed propeller was used.

(The trouble-prone Tu-8. This shows the streamlining ‘scallops’ behind the observation blisters used for aiming the remote-control lower turret.) (Tupolev PLC company photo)

The Tu-8 first flew in May 1947. Twelve months of factory test flights were needed as the aircraft exhibited constant problems. On 20 April 1948, the Tupolev bureau felt it had all the bugs worked out and delivered the prototype Tu-8 to the Soviet air force on 23 August 1948. The air force’s tests did not last long. On 30 November 1948, the Tu-8 was rejected. The air force pilots said that the centre-of-gravity shift made it unstable, and that the Tu-2’s landing gear was dangerously stressed with bomb weight onboard. Unbeknownst to either the test pilots or the Tupolev bureau, the USSR’s top secret nuclear team also had determined that the RDS-1, the upcoming first Soviet atomic bomb, wouldn’t fit in the Tu-8. The Tupolev bureau halfheartedly worked on fixing the Tu-8’s issues for a short while, but in the long run really could have cared less because the postwar Tu-14 “Bosun” jet bomber was already flying. The Tu-8 was soon forgotten about. It was the final development of the Tu-2.

Legacy

The Tu-2 secured the Tupolev bureau’s place as the USSR’s main designer of bombers. The bureau’s next design, the Tu-14 “Bosun”, was basically an enlarged, jet-powered offshoot of the Tu-2.

Although it is relatively obscure in the rest of the world, the “Bat” is still well-regarded in Russia for it’s role during WWII and the early part of the Cold War.