Modern-Aviation

In order to understand something of the way aircraft were designed in the Soviet Union before the War a little explanation is needed here, since the design proces of the Pe-2 is the perfect role model.

Vladimir Petlyakov was one of the best assistants of Andrei Tupolev at the TsAGI (Tsentral'nyi Aerogidrodynamichesky Institut - Central Aerodynamics and Hydrodynamics Institute) from 1921, and played a major part in the creation of many Tupolev aircraft. Tupolev was a strong believer in the use of metal structures, and Petlyakov became an expert in light alloy structures after learning the basics of this science with Junkers, which was the world leader in light alloy structures for aircraft during the 1920s. Up to 1935 Petlyakov was largely responsible for the light alloy wings of aircraft such as the TB-1 and TB-3, and in Tupolev’s absence on the USA learning about American design concepts was wholly responsible for the development of the TB-4 and ANT-20. In 1936 Petlyakov was appointed manager of the ZOK, which was the factory for special construction attached to the TsAGI, and as such more or less designed the ANT-42 that was later renamed as the Petlyakov Pe-8.

In 1937 Petlyakov was arrested, possibly in relation to Tupolev’s similar arrest for allegedly selling the design of the VI-100 fighter to the Germans for transformation into the Messerschmitt Bf 110 heavy fighter. Petlyakov was imprisoned at a special unit and given the assignment of designing a high-altitude fighter under the auspices of the KB-100 design brigade with A.M. Izakson as his assistant. Such was the success of the design, which finally appeared as the VI-100 and formed the basis of the Pe-2, that Petlyakov was released and installed as head of his own design bureau in July 1940. Sadly, Petlyakov was killed in January 1942 when the second Pe-2 off the production line, which he was using as the bureau’s liaison aeroplane, caught fire in the air and crashed. Petlyakov was succeeded successively by Izakson, A.I. Putilov and, from 1943, V.M. Myasishchyev who were thus responsible for all later Pe-2 developments. The Petlyakov Design Bureau was closed in 1946.

The origins of the Pe-2 can be found in the VI-100 (Vysotnyi Istrebitel-100, or high-altitude fighter type '100') prototype that first flew in 1939 or 1940 as a cantilever low-wing monoplane of basically all-metal construction with with the exception of its fabric-covered control surfaces. It must be noted here that '100' is in no way a sequence number, but merely a reference to the bureau were it was developed: STO. STO is also the word for the numeral '100' in the Russian language. The office was placed inside a complex, and staffed with imprisonned designers like Petlyakov. The VI-100 was of conventional layout but an extremely advanced design with turbocharged engines, radiators installed in wing ducts with four upper-surface exits rather than in exterior baths, no hydraulics but a powerful 28-volt electrical system with some 50 actuators controlling most of the moving parts, a pressurized cockpit with tandem two-seat accommodation for the pilot and radio operator/gunner, a dihedraled tailplane carrying endplate vertical surfaces and fully retractable tailwheel landing gear including main units that retracted rearward into the underside of the nacelles for the two wing-mounted Klimov M-105 (later VK-105) Vee engines, rated at 1,050 hp (783 kW) for take-off each.

The VI-100 had a gun armament of four 0.3 inch (7,62 mm) ShKAS machine guns with 600 rounds per gun in the nose, and one 0.3 inch (7,62 mm) ShKAS trainable rearward-firing machine guns in the rear cockpit, which was located over the trailing edge of the wing roots at some distance from the pilot’s cockpit over the leading edge of the wing roots in an installation that was finally unpressurised because of delays in finalisation of the pressurised cockpit by M.N. Petrov’s brigade. The VI-100 revealed good performance and handling, but was difficult and expensive to produce.

In May 1940 its was therefore decided that further development would be concentrated on the PB-100 (Pikiruyushchii Bombardirovshchik-100, or dive-bomber type '100') with no provision for a pressurized cabin, provision for a prone navigator/bombardier below and ahead of the pilot in the nose below floor level, and the powerplant revised from the use of two TK-3 turbochargers to two TK-2 turbochargers. Two armament fits were proposed: one was based on the use of eight 0.3 inch (7,62 mm) ShKAS machine guns as a quartet of fixed forward-firing weapons in the nose and two pairs of trainable rearward-firing weapons installed in the dorsal and ventral positions; and the other was based on the use of two 20 mm ShVAK cannon and two 0.3 inch (7,62 mm) ShKAS machine guns trainably mounted in an underfuselage box so that the weapons (located in mixed pairs at the front and rear of the box with the cannon on the right and the machine gun on the left) could be fired obliquely forward/rearward and at any angle of depression to a maximum of -40°. The disposable armament was a maximum of 2,205 lb (1.000 kg) including 1,323 lb (600 kg) carried internally in a lower-fuselage weapons bay.

The PB-100 prototype was produced as a conversion of the second VI-100 prototype, and made its maiden flight in June 1940. Later in the same month the decision was taken for the PB-100 to be placed in immediate production with a number of minor changes as the Petlyakov Pe-2, and in the following month Petlyakov and the other members of his design team were released from detention.

The Pe-2 used basically the same airframe as the PB-100 but had revised accommodation, M-105R Vee engines without turbochargers and installed in different nacelles, a hydraulic actuation system for the main landing gear units, enlarged vertical tail surfaces, and improvements to the protection for the crew and fuel tanks. The opportunity was also taken to revise the airframe structure as a means of facilitating mass production.

The Pe-2 was of basically all-metal construction, and its core was a fuselage of nearly circular cross section. This carried the flying surfaces, which comprised a dihedraled tailplane with endplate vertical surfaces, and a low-set wing that was based on a flat center section that was tapered in thickness and slightly in chord (the leading edges were straight and the tailing edges marginally tapered), and carried dihedraled outer panels that were tapered in thickness and chord. The moving surfaces on the wing comprised the standard trailing-edge combination of outboard ailerons and inboard flaps (the latter of the Shrenk type) and underwing dive brakes of the Venetian blind type. These last were controlled by the AP-1 automatic dive-control system that was later removed to allow direct control of these surfaces by the pilot. This automatic dive-control system is likely derived from purchased Junkers Ju 88A dive bombers. The airframe was completed by the tailwheel landing gear, which was fully retractable with main units that folded rearward into the underside of the nacelles for the two wing-mounted engines.

The accommodation was centered on a large and comfortable cockpit under a framed, glazed canopy. The cockpit was set farther forward along the upper part of the fuselage than had been the case in the VI-100 and PB-100, and provided accommodation for the pilot on the left with the navigator/bombardier behind him and to the right. The navigator/bombardier was seated facing the rear, and operated the 0.3 inch (7,62 mm) ShKAS trainable machine gun that was the Pe-2’s main defensive weapon against attacks from above and the rear, and for the attack phase of the mission moved to a prone bombardier position in the glazed lower part of the extreme nose. The other member of the crew was the radio operator/gunner in a separate compartment to the rear of the fuselage fuel tank under a glazed roof panel and with an oval window on each side: the defensive weapon controlled by this man was a 0.3 inch (7,62 mm) ShKAS trainable rearward-firing weapon in a retractable installation. The rest of the gun armament comprised two 0.3 inch (7,62 mm) ShKAS fixed forward-firing weapons on the sides of the forward fuselage in an installation controlled by the pilot.

The disposable armament was normally four 220 lb (100 kg) FAB-100 bombs in the lower-fuselage weapons bay and/or four 551 lb (250 kg) FAB-250 bombs carried on four hardpoints under the inner wing panels, but there was also provision for two 220 lb (100 kg) FAB-100 bombs in the rear of each engine nacelle.

The powerplant initially comprised two Klimov M-105RA Vee engines, rated at 1,100 hp (820 kW) for take-off each, and driving a three-blade VISh-61 metal propeller of the constant-speed type. These engines were supplied with fuel from five rubberized fabric tanks (one in the fuselage, two in the inner wing panels and two in the outer wing panels) that were inerted by cooled engine exhaust gases (against fire or explosions). The fuel capacity originally totaled 239 Imp gal (287 US gal, 1.086 liters) but was later increased to a total of 326 Imp gal (392 US gal, 1.484 liters) by enlarging the fuselage tank and adding three new tanks (one in the center section and two in the outer wing panels outboard of the original tanks).

The nickname 'Peshka' ('Little Pe' or 'Pawn') was applied to the aircraft both by the industry and the air force. I can only guess for the real reason of the name, except that the other major design of Vladimir Petlyakov was the Pe-8 (TB-7). This four-engined bomber was huge, dwarfing the Pe-2 (and Pe-3 which had the same ancestor as the Pe-2).