Junkers Ju 88 A-4

The Junkers Ju 88 is a German World War II ''Luftwaffe'' twin-engined multirole combat aircraft. Junkers Aircraft and Motor Works (JFM) designed the plane in the mid-1930s as a so-called ''Schnellbomber'' ("fast bomber") that would be too fast for fighters of its era to intercept. It suffered from technical problems during its development and early operational periods but became one of the most versatile combat aircraft of the war. Like a number of other ''Luftwaffe'' bombers, it served as a bomber, dive bomber, night fighter, torpedo bomber, reconnaissance aircraft, heavy fighter and at the end of the war, as a flying bomb.

Despite a protracted development, it became one of the ''Luftwaffe''s most important aircraft. The assembly line ran constantly from 1936 to 1945 and more than 15,000 Ju 88s were built in dozens of variants, more than any other twin-engine German aircraft of the period. Throughout production the basic structure of the aircraft remained unchanged.Angelucci and Matricardi 1978 p. 118.Angelucci and Matricardi 1978, pp. 118–119.

Design and development

In August 1935, the German Ministry of Aviation submitted its requirements for an unarmed, three-seat, high-speed bomber with a payload of .Dressel and Griehl 1994, p. 71. Design of the Ju-88 began with a study (EF59) which evolved into two parallel designs, Ju-85 and Ju-88. The Ju 85 was a twin-engined bomber aircraft prototype, designed by Junkers in 1935. The Ministry of Aviation requested the aircraft, which differed from the Ju 88 due to the use of a twin fin tail unit. The aircraft was never put into service.

Design was initiated by Junkers Chief Designer Ernst Zindel. He was assisted by Wilhelm Heinrich Evers and American engineer Alfred Gassner. Evers and Gassner had worked together at Fokker Aircraft Corporation of America where Gassner had been Chief Engineer. Junkers presented their initial design in June 1936, and were given clearance to build two prototypes (Werknummer 4941 and 4942). The first two aircraft were to have a range of and were to be powered by two DB 600s. Three further aircraft, Werknummer ''4943'', ''4944'' and ''4945'', were to be powered by Jumo 211 engines. The first two prototypes, Ju 88 V1 and V2, differed from the V3, V4 and V5 in that the latter three models were equipped with three defensive armament positions to the rear of the cockpit, and were able to carry two bombs, one under each inner wing panel.

The aircraft's first flight was made by the prototype Ju 88 V1, which bore the civil registration D-AQEN, on 21 December 1936. When it first flew, it managed about and Hermann Göring, head of the Luftwaffe was ecstatic. It was an aircraft that could finally fulfill the promise of the ''Schnellbomber'', a high-speed bomber. The streamlined fuselage was modeled after its contemporary, the Dornier Do 17, but with fewer defensive guns because the belief still held that it could outrun late 1930s-era fighters. The fifth prototype set a closed-circuit record in March 1939, carrying a payload at a speed of .

The first five prototypes had conventionally-operating dual-strut leg rearwards-retracting main gear, but starting with the V6 prototype, a main gear design debuted that twisted the new, single-leg main gear strut through 90° during the retraction sequence, much like that of the American Curtiss P-40 Warhawk fighter. This feature allowed the main wheels to end up above the lower end of the strut when fully retracted and was adopted as standard for all future production Ju 88s, and only minimally modified for the later Ju 188 and 388 developments of it. These single-leg landing gear struts also made use of stacks of conical Belleville washers inside them as their main form of suspension for takeoffs and landings.

By 1938, radical modifications from the first prototype began to produce a "heavy" dive bomber. The wings were strengthened, dive brakes were added, the fuselage was extended and the number of crewmen was increased to four. Due to these advances, the Ju 88 was to enter the war as a medium bomber.

The choice of annular radiators for engine cooling on the Ju 88, which placed these radiators immediately forward of each engine and directly behind each propeller, allowed the cooling lines for the engine coolant and oil-cooling radiators (integrated within the annular design) to be as short as possible, with integral port and starboard air intakes for cooling the exhaust headers, the starboard inlet also supplying the inlet air for the supercharger.

As the outbreak of WW II in Europe approached, by the time Luftwaffe planners like Ernst Udet had their opportunities to have their own "pet" features added (including dive-bombing by Udet), the Ju 88's top speed had dropped to around . The Ju 88 V7 was fitted with cable-cutting equipment to combat the potential threat of British barrage balloons, and was successfully tested in this role. The V7 then had the Ju 88 A-1 "beetle's eye" faceted nose glazing installed, complete with the ''Bola'' undernose ventral defensive machine gun emplacement, and was put through a series of dive-bombing tests with bombs, and in early 1940, with bombs. The Ju 88 V8 (''Stammkennzeichen'' of DG+BF, Wrk Nr 4948) flew on October 3, 1938. The A-0 series was developed through the V9 and V10 prototypes. The A-1 series prototypes were Wrk Nrs 0003, 0004 and 0005. The A-1s were given the Jumo 211B-1 or G powerplants.

Dr. Heinrich Koppenberg (managing director of Jumo) assured Göring in the autumn of 1938 that 300 Ju 88s per month was definitely possible. Göring was in favour of the A-1 variant for mass production.

Production was delayed drastically by developmental problems. Although planned for a service introduction in 1938, the Ju 88 finally entered squadron service (with only 12 aircraft) on the first day of the invasion of Poland in 1939. Production was painfully slow, with only one Ju 88 manufactured per week, as problems continually kept cropping up. The Ju 88C series of heavy fighter was also designed very early in 1940, but kept secret from Göring, as he only wanted bombers.

Dive bomber

In October 1937 ''Generalluftzeugmeister'' Ernst Udet