Aviation of World War II
High-Speed Heavy Bomber
Designer Hans Wocke initiated the creation of Ju 287. Design efforts began in 1943 and, on 16 August 1944, the aircraft made its maiden flight. The Ju 287V-1 experimental prototype was fitted with four Jumo 004B turbojet engines with 900 kg thrust each; two were placed on either side of the fuselage and two were on pylons under the wings. Rocket boosters were used to facilitate take-off. In all, 17 flights were made at speeds of up to 550 km/h.
The aircraft featured a sweepforward wing. Wocke proposed this form to prevent the stall at the tips of the airfoil common for conventional swept wings. However, in this case, there could be some problems with wing stiffness (aero-elasticity) at high speeds, but Wocke believed that certain design changes would eliminate this problem. In particular, he moved the engine nacelles forward with respect to a wing stiffness line.
Ju 287V-1 was damaged during a bombing raid on the Junkers plant and, by the end of the war, Junkers was working on the Ju 287V-2 variant with six turbojet engines, three under each wing. This aircraft had to develop a speed of 800 km/h and accommodate up to 4 tons of bombs. Its take-off weight was 21,200 kg.
Design team in Dessau (OKB-1). Its task was to develop Ju 131 and 132 bombers, Ju 126 ground-attack aircraft (in documents they often were designated EF-131, EF-132, and EF-126, from Entwicklungs Flugzeug-"Experimental Aircraft"), Jumo 004 and Jumo 01 jet engines, and the Jumo 224 aircraft diesel engine.
To fulfill these tasks, two large sections were set up at OKB-1-aircraft and engine. The aircraft section comprised 433 employees, including 276 designers and 157 people working in scientific research laboratories. There were 402 specialists in the engine section, 235 at the design bureau, and 167 at scientific research laboratories. In all, 2992 employees worked at the Dessau plant in May 1946, including 20 representatives of the USSR Ministry of the Aviation Industry.
B. Baade was appointed chief designer of the Aircraft Section, with a monthly salary of 2000 marks. Aerodynamics engineer F. Freitag became his deputy'. P. N. Obrubov, a Plant No. 240 engineer who came to the former Junkers Company from the USSR in April 1946, was section chief. Dr. Scheibe, former chief of the Junkers piston engine bench test section, headed the Engine Section.
The unfinished Ju 287V-2 also became the foundation for the EF-131 prototype jet bomber. F. Freitag and Hans Wocke were responsible for its development, with B. Baade exercising overall supervision.
Since no drawings or test materials were found in Dessau, all the documentation had to be reconstituted. It delayed the effort but, nevertheless, by January 1946 preparations for the assembly of a prototype example began. Some components (wing sections, in particular) were taken from Ju-287V-2 but most had to be redone. The work was labor intensive and the decision was to stop after the manufacture of three examples: two (V-l, V-3) for flight testing and one (V-2) for strength tests.
In May wind tunnel tests of the airplane model began. Simultaneously, the operation of the power plant was tested on a specially made bench.
In July a full-size airplane mockup was ready and an Air Forces commission headed by Lieutenant General V. A. Ushakov arrived to inspect it. The commission drew the following conclusion: "The EF-131 jet bomber... is of interest to the Air Forces of the Armed Forces and could be employed for research and assimilation of: flight, piloting procedures, and combat employment at high speeds and altitudes, as well as for gaining experience in operating a jet bomber..."18 The Mockup Commission recommended that the armament be upgraded and the canopy jettison and ejection systems improved.
A month later, the first EF-131 (V-l) was ready.
Design team in the USSR. Development of the EF-140 began in 1947 as Baade's initiative and, after a mockup was inspected in 1948, the government approved the work. The second EF-131 flying prototype was used in building the aircraft and it sped up manufacturing. In September 1948 the machine was completely ready to fly.
On 5 October during the second flight, some defects in engine operation were discovered. The so-called "automatic fuel flow meter" mounted on the AM-TKRD-01 engine was unsatisfactory and it proved very difficult to control engine thrust manually. The engine was spontaneously changing rpm and the aircraft jerked and rocked in flight. After the seventh sortie, flight-testing had to be stopped.
In 1949 the engines were replaced and flights went on. On 24 May plant testing was completed. The aircraft reached a speed of 904 km/h and range of 2000 km.
For some reason (possibly in connection with successful testing of the Tu-14 tactical bomber), no official testing of the EF-140 was conducted. Instead, in May 1948 OKB-1 was tasked to convert the plane into a long-range reconnaissance aircraft. This version was designated "140-R".
To obtain the required range (3600 km) and altitude (14,100 m), the aircraft was fitted with new more fuel-efficient VK-1 engines that V. Ya. Klimov designed (a modification of British Nene-1 turbojet engine). In addition, the wingspan was increased from 19.4 to 21.9 m and external fuel tanks were mounted on the wing tips, thus increasing total fuel capacity to 14,000 liters.
The aircraft was armed with two remotely operated gun turrets with 23mm paired cannon. Targeting was carried out with the aid of periscope gun sights and the gun turrets were electrically operated. In case the upper gunner was killed or wounded, his turret could be connected with the lower turret gun sight and fire control system.
The "140-R" was fitted with equipment for performing day and night reconnaissance (photo cameras, illuminating bombs, and so on) placed in the forward part of the cargo bay and aft fuselage.
The first flight of the "140-R" was made on 12 October 1949. On 20 October the aircraft took off for the second time. Both flights were interrupted due to excessive wing vibration and the aircraft was returned to the plant.
Test flights resumed the next spring, after structural changes were made. The testing was stopped after the second flight on 24 March because the wing buffeting continued. TsAGI specialists were brought in to solve the problem. It was assumed that the flutter was caused by the wing-tip fuel tanks. On 18 July 1950 all work on the 140-R aircraft was stopped by government decree.
The same decree canceled testing of the "140-B/R" variant that could be employed both as a reconnaissance aircraft and bomber. Baade's OKB had been tasked with developing it in August 1948. The aircraft differed from the "140-R" mainly in its having a different "filling". The fire control system was improved and the crew reduced to three. The plane was estimated to have a range of 3000 km, maximum speed of 866 km/h, ceiling of 12,000 m with a bomb load of 1500 kg, and a fuel capacity of 9400 liters.
By the time the decree was issued, the aircraft had been built and partially ground tested. That was the last aircraft with a sweepforward wing in the USSR. After unsuccessful testing of the "140-R" reconnaissance aircraft, TsAGI specialists concluded that it was undesirable to use such wing in aircraft manufacturing.