Petlyakov Pe-8 (TB-7)
Long-Range Strategic Heavy Bomber Aircraft
The Petlyakov Pe-8 was the only Soviet-made, four-engined strategic bomber to serve in World War 2.
Authored By: Dan Alex | Last Edited:
During the lead-up to World War 2 (1939-1945), the Soviet Union joined Germany and Italy in providing a reduced focus on capable, four-engined strategic heavy bombers. As a result, the only Soviet-originated design to carry this quality became the largely forgotten Petlyakov "Pe-8". The Pe-8 was designed to a specific Soviet Air Force requirement that emerged in 1934 calling for a replacement to the outgoing Tupolev TB-3 series. This bomber was ancient-looking even by 1930s standards despite being introduced as recently as 1932. It saw a rather healthy production run of 818 aircraft.
Soviet authorities now turned their attention to a more modern aircraft with a 4,400 lb bomb load capability while reaching speeds of 270 miles per hour with a range out to 2,800 miles. This gave rise to the preliminary aircraft designation of ANT-42 with design attribution given to Vladimir Petlyakov and his team. A working prototype achieved first flight December 27th, 1936 and was eventually adopted under the Soviet Air Force designation of "TB-7". It formally entered service in 1940. However, back in October of 1937, Petlyakov was imprisoned (with others) during Stalin's "Great Purge" which only added delays to the program. The purge served to repress communist officials who threatened Stalin's control with many lives ending in either imprisonment or execution.
While the Soviet Union played its part in the dismantling of Poland during the German invasion of September 1939 (to officially begin World War 2), the former allies became enemies when German forces invaded the Soviet Union in June of 1941 through Operation Barbarossa. The German advance was swift and terrible for the retreating Soviets who pressed any manner of weaponry against the aggressors but lost thousands of men, vehicles, and aircraft to the scourge.
The Pe-8 program labored on though it would be permanently dogged by a lack of available - or capable - engines (the aircraft required four). Original aircraft were to be fitted with superchargers for better performance at altitude but only four production aircraft managed these engine types. Another two airframes were settled with Mikulin AM-34FRNV series engines while a stock of eighteen airframes would be powered by Mikulin AM-35A engines. Though was also being given to Mikulin M-30B diesel-fueled engines though these, while providing better fuel economics, never supplied the required performance results. The Mikulin M-82FN was another engine version, this offering fuel-injection.
On January 12th, 1942, the TB-7's lead designer, Petlyakov himself, was killed in a crash involving his Pe-2 dive bomber. As a result, the TB-7 was redesignated in his honor as the "Petlyakov Pe-8" - which is the designation the heavy bomber is largely recognized for today (December 2013). The change occurred on aircraft arriving from 1942 onwards.
Manufacture of the Pe-8 was handled out of Kazan Factory No. 124 and production spanned from 1936 to 1944. However, engine reliability, performance and availability were never completely solved and dogged the aircraft for the entirety of its service career. Indeed, many were lost simply to mechanical failures than enemy guns. In a late 1942 initiative, the aircraft received new Shvetsov ASh-82 radial piston engines of 1,850 horsepower output which improved reliability to an extent. Other refinements included removal of the nacelle-mounted defensive machine guns.
Base Pe-8s featured a crew of eleven personnel. Length measured 76 feet with a wingspan of 128.3 feet and height of 20.3 feet. When empty, the aircraft weighed in at 40,940lbs and featured an MTOW of 77,000lbs. Power was typically served through 4 x Mikulin AM-35A series, liquid-cooled V12 engines developing 1,340 horsepower each. This provided a top speed of 275 miles per hour, a range of 2,300 miles and a service ceiling of 30,500 feet. Rate-of-climb was listed at 1,150 feet per minute. In terms of the period, the Pe-8 could be compared to the Avro Lancaster of Britain or the Boeing B-17 Flying Fortress of the United States.
Outwardly, the Pe-8 carried a conventional heavy bomber shape for the period. Its wide-spanning wings fitted the four engines along their leading edges with the inboard mount receiving a retractable, single-wheeled main landing gear leg unit. The fuselage was aerodynamically contoured and includes a stepped cockpit with framing and a heavily glazed nose assembly. The empennage carried a single vertical tail unit and low-set horizontal tailplanes.
Beyond its offensive-minded internal bomb load of 11,000lbs, the aircraft featured defensive-minded armament. 2 x 20mm ShVAK cannons were fitted to dorsal and tail turrets. 2 x 12.7mm UBT heavy machine guns were added to the rear of the engine nacelles to counter the threat posed by trailing aircraft behind the wings (these were removed in some re-engined models). 2 x 7.62mm ShKAS machine guns were installed in a nose turret to complete the defensive network of guns.
In practice, the Pe-8 served in its intended long-range strategic bombing role, engaging "exceptional" enemy targets such as airfields and railway yards in an attempt to expose the weaknesses of the enemy defense. In turn, successful missions were drummed up through the Soviet propaganda machine which was intended to lift local morale during the fighting on the ground. The missions were often daring and suicidal and enemy pilots were keen to locate, engage and destroy these large, ponderous aircraft at any opportunity. Such a targeting led to many losses of the existing Pe-8 stock.
With mounting losses, missions were scaled back in number. During 1944, many were beginning to see replacement by incoming Allied bombers types available through Lend-Lease. Pe-8 use therefore dwindled and some saw extended use as converted VIP transports by war's end. In the post-war years, the Pe-8 served as a technology testbed or in non-military roles. Beyond the base Pe-8 designation, there was the Pe-8ON VIP model and the Pe-8LL piston-engined trial bed. All Pe-8s were soon retired as more advanced large bomber designs appeared in the Soviet Air Force inventory.