The Yermolayev Yer-2, a Soviet medium bomber utilized during World War II, was derived from the Bartini Stal-7 prototype airliner prior to the war.
Its operational use included bombing Berlin from airbases in Estonia following the commencement of Operation Barbarossa in 1941.
Production of the aircraft was halted in August of that year to prioritize the construction of Ilyushin Il-2 ground-attack aircraft.
However, production resumed at the end of 1943 with the implementation of new, fuel-efficient Charomskiy ACh-30B Diesel engines.
Despite its intended use as a long-range medium bomber, the Yer-2 was employed in tactical ground-attack missions during the Battle of Moscow, resulting in significant losses.
The remaining aircraft were gradually phased out until August 1943, when the last examples were transferred to schools.
Nevertheless, the resumption of production in 1943 enabled the aircraft to recommence combat operations in April 1945.
The Yer-2 remained in service with Long-Range Aviation until it was eventually replaced by four-engined bombers, such as the Tupolev Tu-4, at the conclusion of the 1940s.
Roberto Bartini, the former chief designer at the ZOK NII GVF “Factory for Special Constructions at the Scientific Test Institute for the Civil Air Fleet,” designed and constructed the Stal-7 airliner.
The aircraft’s exceptional performance, particularly in terms of its payload, was noteworthy, with over 56% of the total weight being payload at gross overload weight.
However, during flight trials with maximum all-up weight, the prototype crashed on take-off in early 1938, leading to Bartini’s arrest and imprisonment in a Siberian Gulag in February 1938.
After Bartini’s arrest, Vladimir Yermolaev was appointed as the new chief designer at OKB-240, with the task of transforming the Stal-7 design into a long-range bomber.
The Stal-7 remained unrepaired until Yermolaev’s appointment, and the design was modified to include a bomb bay in the fuselage.
After repair, the Stal-7 continued with the flight-test program, including a record-breaking nonstop flight on 28 August 1939, covering a distance of 5,086 km (3,160 mi) at an average speed of 405 km/h (252 mph) from Moscow to Sverdlovsk to Sevastopol and back to Moscow.
The DB-240, the bomber version of the Stal-7, was designed by the beginning of 1939, and two prototypes were constructed in July of that year.
The DB-240 retained only the general layout of the Stal-7, as the structure was almost entirely redesigned.
The pilot’s cockpit was offset to port to improve his downward view, and the navigator/bomb aimer sat in the extensively glazed nose with a 7.62-millimeter (0.300 in) ShKAS machine gun.
The radio operator sat below and to starboard of the pilot, and the dorsal gunner was in a partially retractable turret with one 12.7-millimetre (0.50 in) Berezin UBT machine gun.
Another ShKAS was fitted in a ventral hatch.
The DB-240 could carry up to 2,000 kg (4,409 lb) of bombs in the bomb bay and two 500-kilogram (1,102 lb) bombs externally.
Up to 4,600 kg (10,141 lb) of fuel could be carried.
The DB-240 was designed to use the experimental Klimov M-106 V12 engines, but the less-powerful Klimov M-105 engine had to be substituted because the M-106 was not available.
The DB-240 prototype made its first flight on 14 May 1940 and began its state acceptance tests on 27 September 1940.
However, the weaker engines prevented the DB-240 from reaching its designed performance, and its defensive armament was deemed inadequate.
Other problems included an excessively long take-off run and engine defects.
Despite these issues, the DB-240’s heavy bomb load and long-range capabilities (4,100 kilometres (2,548 mi) carrying 1,000 kg (2,205 lb) of bombs) were noteworthy.
The DB-240 was ordered into production at Factory No. 18 in Voronezh as the Yermolayev Yer-2, with approximately 50 aircraft delivered by 22 June 1941.
These aircraft were about 5–8 km/h (3.1–5.0 mph) slower than the prototype, and their normal weight increased 1,220 kg (2,690 lb) to 12,520 kg (27,602 lb).
Production was terminated in August 1941, with only 128 built to allow the factory to concentrate on the higher-priority Ilyushin Il-2 ground-attack aircraft.
In 1941, a Yer-2 was modified with experimental Mikulin AM-37 engines, a reinforced undercarriage, armoured seats for the navigator and gunner, and 12.7 mm UBT machine guns in place of its original ShKAS weapons.
It was able to reach 505 km/h (314 mph) at 6,000 m (19,685 ft), but the range was reduced to 3,500 km (2,175 mi) carrying 1,000 kg (2,205 lb) of bombs.
However, the engine was unreliable and had cooling problems that the Mikulin OKB did not have the resources to resolve, leading to its cancellation in October when the factory was forced to evacuate from Moscow by the German advance.
The Charomskiy M-40F Diesel engine was also evaluated in a Yer-2 in 1941.
This engine offered a greatly reduced fuel consumption compared to a standard gasoline-powered engine, but at a great penalty in weight.
These engines increased the aircraft’s range, but also decreased its speed and manoeuvrability.
Despite these challenges, the Yermolayev Yer-2 proved to be a valuable asset for the Soviet Union during World War II, serving as a long-range bomber and reconnaissance aircraft.
Its heavy bomb load and long-range capabilities made it a formidable weapon against enemy targets, and its durability and reliability allowed it to operate in harsh conditions and withstand enemy fire.
The Yer-2 played a significant role in the Soviet Union’s air campaign against Nazi Germany, and its legacy as a pioneering long-range bomber continues to be recognized in aviation history.
The Yer-2 bomber aircraft was not operational in squadron service at the time of Germany’s invasion on 22 June 1941.
However, the 420th and 421st Long-Range Bomber Regiments were established shortly thereafter, although neither regiment conducted any operational missions until later in the summer.
On 10 August, Yer-2s from the 420th DBAP, accompanied by Petlyakov Pe-8s from the 432nd DBAP, attempted to bomb Berlin from Pushkino Airfield near Leningrad.
Despite the airfield being too short to accommodate a fully loaded Yer-2, three bombers managed to take off, with two successfully bombing Berlin or its outskirts.
However, only one aircraft returned, as the other was shot down by ‘friendly’ Polikarpov I-16s upon re-entering Soviet airspace, and the third aircraft went missing.
During the nights of 28–29 and 30 August – 1 September, three crews from the 420th DBAP bombed Königsberg from Ramenskoye Airport, southeast of Moscow.
By 1 October 1941, 63 Yer-2s were in service, but only 34 were operational.
The 420th DBAP had flown 154 sorties by the beginning of November, with 30 of its 40 aircraft lost, over half of which were due to non-combat losses.
The autumn and winter saw extremely high losses, as the aircraft were inappropriately committed against German tactical frontline targets during the Battle of Moscow at low altitudes.
By 18 March 1942, only 12 Yer-2s were in service.
On 4 August 1942, the 747th DBAP had only ten Yer-2s available and was briefly committed during the Battle of Stalingrad.
The survivors were flown in ever-dwindling numbers until August 1943, when the last few aircraft were transferred to schools by the 2nd Guards DBAP and the 747th DBAP.
Although the Yer-2 was placed back into production at the end of 1943, none of the new bombers had been issued to combat units by 1 June 1944.
However, by 1 January 1945, 42 Yer-2s were in service, and this number increased to 101 by 10 May 1945, after the war ended.
The first combat mission undertaken by Yer-2s after their return to production was a raid on Königsberg on 7 April 1945 by the 327th and 329th Bomber Aviation Regiments.
The Yer-2 remained in service with Long-Range Aviation units until it was replaced by four-engined bombers such as the Tupolev Tu-4 in the late 1940s.
Two prototypes of the Yer-2 series with two 1,050 hp M-105 engines.
Production version with two M-105 engines, 128 built.
One aircraft re-engine with two prototype 1,380 hp Mikulin AM-37 engines, the fastest of all Yer-2s.
The first diesel-powered Yer-2, with modified wings.
One converted with two 1,500 hp Charomskiy M-40F diesel engines.
Production model of the diesel-engine version.
Performance was excellent despite the poor reliability and rough running of the Charomskiy ACh-30B diesel engines.
Range increased 1,500 km (930 mi) from the version with M-105 engines.
Two aircraft from the Yer-2/ACh-30B production line were modified with a 12-seat VIP cabin, military equipment removed and long-range fuel tanks in the bomb-bay.
A third aircraft was converted from a Yer-2 and used for shuttle flights between Irkutsk and Moscow.
One aircraft was modified as an engine testbed for captured Argus As 014 pulse jet engines.
One production aircraft used as a testbed for the 2,200 horsepower (1,600 kW) Dobrotvorskii MB-100 engine in 1945.
The final model of the Yer-2 series was a 1941 production aircraft re-engine with ACh-30BF engines and redesignated as the Yer-4.
It had a slightly larger wingspan, increased take-off weight and improved armament.
The prototype was tested in December 1943 but did not enter production.
1 x 12.7 mm UBT machine-gun in nose flexible mount.
1 x 12.7 mm UBT machine-gun in ventral flexible mount.
1 x 20 mm ShVAK cannon in a TUM-5 dorsal turret.
Up to 5,000 kg (11,023 lb) of bombs in the internal bomb-bay.
The Osprey Encyclopaedia of Russian Aircraft 1875–1995-Bill Gunston. Soviet Airpower in World War 2-Yefim Gordon. The History of Soviet Aircraft from 1918-Vaclav Nemecek. Red Stars 1939-1945, Soviet Air Force in World War Two-Carl Fredrik Geust, Kalevi Keskinen & Kari Stenman. Soviet Combat Aircraft of the Second World War, Vol 2, Twin Engined Fighters, Attack Aircraft & Bombers-Yefim Gordon, Dmitri Khazanov & Alexander Medved.