Petlyakov Pe-8

https://en.wikipedia.org/wiki/Petlyakov_Pe-8

The Petlyakov Pe-8 (Russian: ???????? ??-8) was a Soviet heavy bomber designed
before World War II, and the only four-engine bomber the USSR built during the
war. Produced in limited numbers, it was used to bomb Berlin in August 1941. It
was also used for so-called "morale raids" designed to raise the spirit of the
Soviet people by exposing Axis vulnerabilities. Its primary mission, however,
was to attack German airfields, rail yards and other rear-area facilities at
night, although one was used to fly the People's Commissar of Foreign Affairs
(Foreign Minister) Vyacheslav Molotov from Moscow to the United States in 1942.

Originally designated the TB-7, the aircraft was renamed the Pe-8 after its
primary designer, Vladimir Petlyakov, died in a plane crash in 1942. Supply
problems complicated the aircraft's production and the Pe-8s also had engine
problems. As Soviet morale boosters, they were also high-value targets for the
Luftwaffe's fighter pilots. The loss rate of these aircraft, whether from
mechanical failure, friendly fire, or combat, doubled between 1942 and 1944.

By the end of the war, most of the surviving aircraft had been withdrawn from
combat units. After the war, some were modified as transports for important
officials, and a few others were used in various Soviet testing programs. Some
supported the Soviet Arctic operations until the late 1950s.

The maiden flight of the unarmed prototype, piloted by M. M. Gromov and without
the ATsN installation, occurred at Khodynka Aerodrome on 27 December 1936. After
successful initial trials, the ATsN system was installed for the State
acceptance trials in August 1937 and the AM-34RNB engines were fitted during the
tests. Gromov reported that the rudder was ineffective and that the outer
engines overheated. Subsequent wind tunnel testing identified a problem with the
aerodynamics of the radiators and nacelles. To solve this problem, the outer
engines' radiators were moved into deep ducts under the inner nacelles. The Pe-8
now featured only two pronounced radiator intakes, one under each inner engine,
each shared by both inner and outer engines, one of the distinctive and unique
features of the aircraft. The rudder was also enlarged and redesigned with a
smooth skin.

Construction of a second prototype began in April 1936, incorporating lessons
from the first aircraft and feedback from the VVS. Designers widened the
fuselage by 100 mm (3.9 in); the 'beard' was also widened and the tail section
was modified to lessen resistance and improve rudder function. A reconfigured
control system included an autopilot and the engineers redesigned portions of
the electrical system. The engines were changed to the more powerful AM-34FRNVs
and a redesigned undercarriage was fitted to the airframe. Two additional fuel
tanks increased the craft's range. The defensive and offensive armament was
revised, and the bomber's weaponry expanded to twin ShKAS guns in the nose,
nacelle barbettes and tail turrets and a dorsal turret with a ShVAK; this design
eliminated the ventral gun. The bomb bay was modified to allow for a single
5,000-kilogram (11,000 lb) FAB-5000 bomb to be carried and provisions were added
to carry VAP-500 or VAP-1000 poison gas dispensers under the wings.

The arrests of both Tupolev and Petlyakov in October 1937, during the Great
Purge, disrupted the program and the second prototype did not make its first
flight until 26 July 1938. Although this prototype served as the basis for the
series aircraft, further modifications were made to the armament. New weaponry
included a retractable ShVAK in the MV-6 dorsal turret, another ShVAK in a KEB
tail turret and a 12.7-millimeter (0.50 in) Berezin UBT machine gun in each ShU
barbette in each inner engine nacelle, on the underside of the wing covering he
lower rear arc of fire to left and right, respectively. Another fuel tank
further increased the range, and the 'beard' was removed entirely, replaced by a
more streamlined nose. Authorization for production was slow for several
reasons, including the Great Purge, but also due to the scarcity of resources,
and a shortage of workers. Although production facilities in the Kazan Factory
No. 124 were ready as early as 1937, the order to begin was not given until
1939.


Role
Heavy bomber

National origin
Soviet Union

Design group
Petlyakov OKB

First flight
27 December 1936

Introduction
1940

Status
Retired

Primary user
Soviet Air Forces

Produced
1936–1944

Number built
93

Removal from combat

The loss of Pe-8s to all causes—mechanical, combat, friendly fire—had steadily
increased from one aircraft per 103 flights in 1942 to one per 46 sorties in
1944. Despite the losses, production kept pace with need. The number of aircraft
belonging to the 45th DBAD continued to rise; 20 were on hand on 1 January 1944
and 30 on 1 June. The Pe-8s flew 276 sorties in 1944 against such targets as
Helsinki, Tallinn and Pskov. Aviation historian Yefim Gordon maintains that the
Pe-8 flew its last mission on the night of 1–2 August 1944, but the Statistical
Digest of the VVS contradicts this claim, showing 31 Pe-8s assigned to 45th DBAD
on 1 January 1945 and 32 on hand on 10 May 1945. However, during this period the
45th DBAD only had three regiments, none of which used the Pe-8 as their primary
aircraft, so while the 45th DBAD may have had Pe-8s, these may not have been in
use as the primary combat aircraft.

The 890th began to fly Lend-Lease B-25 Mitchells in the spring of 1944 and was
itself re-designated as the 890th Bomber Aviation Regiment on 26 December 1944.
The 362nd APDD was formed in early 1944 with four Pe-8s received from the other
two regiments, but these were returned in the spring of 1944, when the regiment
began to convert to the Lend-Lease Mitchells.

Specifications (Pe-8/AM-35A)

General characteristics
Crew: 11
Length: 23.2 m (76 ft 1 in)
Wingspan: 39.13 m (128 ft 5 in)
Height: 6.2 m (20 ft 4 in)
Wing area: 188.66 m2 (2,030.7 sq ft)
Airfoil: root: TsAGI-40 (19%) ; tip: TsAGI-40 (15.5%)
Empty weight: 18,571 kg (40,942 lb)
Gross weight: 27,000 kg (59,525 lb)
Max takeoff weight: 35,000 kg (77,162 lb)
Powerplant: 4 × Mikulin AM-35A V-12 liquid-cooled piston engines, 999 kW (1,340
hp) each
Propellers: 3-bladed constant-speed propellers

Performance
Maximum speed: 443 km/h (275 mph, 239 kn)
Range: 3,700 km (2,300 mi, 2,000 nmi)
Service ceiling: 9,300 m (30,500 ft)
Rate of climb: 5.9 m/s (1,160 ft/min)
Wing loading: 143 kg/m2 (29 lb/sq ft)
Power/mass: 0.140 kW/kg (0.085 hp/lb)

Armament

Guns: ** 2 × 20-millimeter (0.79 in) ShVAK cannons (dorsal and tail turrets) 2 ×
12.7-millimeter (0.50 in) UBT machine guns (engine nacelles)
2 × 7.62-millimeter (0.30 in) ShKAS machine guns (nose turret)

Bombs: Up to 5,000 kg (11,000 lb), including the FAB 5000 5,000 kg bomb




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