Junkers Ju 87
The Junkers Ju 87, popularly known as the "Stuka", is a German dive bomber and ground-attack aircraft. Designed by Hermann Pohlmann, it first flew in 1935. The Ju 87 made its combat debut in 1937 with the Luftwaffe's Condor Legion during the Spanish Civil War of 1936–1939 and served the Axis in World War II from beginning to end.
The aircraft is easily recognisable by its inverted gull wings and fixed spatted undercarriage. Upon the leading edges of its faired main gear legs were mounted ram-air sirens, officially called "Lärmgerät", which became a propaganda symbol of German air power and of the Blitzkrieg victories of 1939–1942, as well as providing Stuka pilots with audible feedback as to speed. The Stuka's design included several innovations, including automatic pull-up dive brakes under both wings to ensure that the aircraft recovered from its attack dive even if the pilot blacked out from the high g-forces, or suffered from target fixation.
The Ju 87 operated with considerable success in close air support and anti-shipping roles at the outbreak of World War II. It led air assaults during the Invasion of Poland in September 1939. Stukas proved critical to the rapid conquest of Norway, the Netherlands, Belgium, and France in 1940. Though sturdy, accurate, and very effective against ground targets, the Stuka was, like many other dive bombers of the period, vulnerable to fighter aircraft. During the Battle of Britain of 1940–1941, its lack of manoeuvrability, speed, or defensive armament meant that it required a heavy fighter escort to operate effectively.
After the Battle of Britain, the Luftwaffe deployed Stuka units in the Balkans Campaign, the African and the Mediterranean theatres and in the early stages of the Eastern Front war, where it was used for general ground support, as an effective specialised anti-tank aircraft and in an anti-shipping role. Once the Luftwaffe lost air superiority, the Stuka became an easy target for enemy fighters, but it continued being produced until 1944 for lack of a better replacement. By 1945 ground-attack versions of the Focke-Wulf Fw 190 had largely replaced the Ju 87, but it remained in service until the end of the war in 1945.
Germany built an estimated 6,000 Ju 87s of all versions between 1936 and August 1944.
Oberst Hans-Ulrich Rudel became the most successful Stuka pilot and the most highly decorated German pilot of the war.
Development
Early design
The Ju 87's principal designer, Hermann Pohlmann, held the opinion that any dive-bomber design needed to be simple and robust. This led to many technical innovations, such as the retractable undercarriage being discarded in favour of one of the Stuka's distinctive features, its fixed and "spatted" undercarriage. Pohlmann continued to carry on developing and adding to his ideas and those of Dipl Ing Karl Plauth, and produced the Ju A 48, which underwent testing on 29 September 1928. The military version of the Ju A 48 was designated the Ju K 47.After the Nazis came to power, the design was given priority. Despite initial competition from the Henschel Hs 123, the Reichsluftfahrtministerium turned to the designs of Herman Pohlmann of Junkers and co-designer of the K 47, Karl Plauth. During the trials with the K 47 in 1932, double vertical stabilisers were introduced to give the rear gunner a better field of fire. The main, and what was to be the most distinctive, feature of the Ju 87 was its double-spar inverted gull wings.
After Plauth's death, Pohlmann continued the development of the Junkers dive bomber. The Ju A 48 registration D-ITOR, was originally fitted with a BMW 132 engine, producing 450 kW. The machine was also fitted with dive brakes for dive testing. The aircraft was given a good evaluation and "exhibited very good flying characteristics".
Ernst Udet took an immediate liking to the concept of dive-bombing after flying the Curtiss F11C Goshawk. When Walther Wever and Robert Ritter von Greim were invited to watch Udet perform a trial flight in May 1934 at the Jüterbog artillery range, it raised doubts about the capability of the dive bomber. Udet began his dive at and released his bombs at, barely recovering and pulling out of the dive. The chief of the Luftwaffe Command Office Walther Wever, and the Secretary of State for Aviation Erhard Milch, feared that such high-level nerves and skill could not be expected of "average pilots" in the Luftwaffe. Nevertheless, development continued at Junkers. Udet's "growing love affair" with the dive bomber pushed it to the forefront of German aviation development. Udet went so far as to advocate that all medium bombers should have dive-bombing capabilities, which initially doomed the only dedicated, strategic heavy bomber design to enter German front-line service during the war years—the 30-metre wingspan Heinkel He 177A—into having an airframe design that could perform "medium angle" dive-bombing missions, until Reichsmarschall Hermann Göring exempted the He 177A, Germany's only operational heavy bomber, in September 1942 from being given the task of such a mismatched mission profile for its large airframe.
Evolution
The design of the Ju 87 had begun in 1933 as part of the Sturzbomber-Programm. The Ju 87 was to be powered by the British Rolls-Royce Kestrel liquid-cooled V12 engine, ten of which were ordered by Junkers on 19 April 1934 at a cost of £20,514 2s 6d. The first Ju 87 prototype was built by AB Flygindustri in Sweden and secretly brought to Germany in late 1934. It was to have been completed in April 1935, but, due to the inadequate strength of the airframe, construction took until October 1935. The mostly complete Ju 87 V1 W.Nr. 4921 took off for its maiden flight on 17 September 1935. The aircraft was later given the registration D-UBYR. The flight report, by Hauptmann Willy Neuenhofen, stated the only problem was with the small radiator, which caused the engine to overheat.The Ju 87 V1, powered by a Kestrel engine and fitted with a twin tail, crashed on 24 January 1936 at Kleutsch near Dresden, killing Junkers' chief test pilot, Willy Neuenhofen, and his engineer, Heinrich Kreft. The square twin fins and rudders proved too weak; they collapsed and the aircraft crashed after it entered an inverted spin during the testing of the terminal dynamic pressure in a dive. The crash prompted a change to a single vertical stabiliser tail design. To withstand strong forces during a dive, heavy plating, along with brackets riveted to the frame and longeron, was fitted to the fuselage. Other early additions included the installation of hydraulic dive brakes that were fitted under the leading edge and could rotate 90°.
The RLM was still not interested in the Ju 87 and was not impressed that it relied on a British engine. In late 1935, Junkers suggested fitting a DB 600 inverted V12 engine, with the final variant to be equipped with the Jumo 210. This was accepted by the RLM as an interim solution. The reworking of the design began on 1 January 1936. The test flight could not be carried out for over two months due to a lack of adequate aircraft. The 24 January crash had already destroyed one machine. The second prototype was also beset by design problems. It had its twin stabilisers removed and a single tail fin installed due to fears over stability. Due to a shortage of engines, instead of a DB 600, a BMW "Hornet" engine was fitted. All these delays set back testing until 25 February 1936.
By March 1936, the second prototype, the V2, was finally fitted with the Junkers Jumo 210Aa engine, which a year later was replaced by a Jumo 210 G. The testing went well, and the pilot, Flight Captain Hesselbach, praised its performance. However, Wolfram von Richthofen, in charge of developing and testing new aircraft in the Technisches Amt, or Technical Service, told the Junkers representative and Construction Office chief engineer Ernst Zindel that the Ju 87 stood little chance of becoming the Luftwaffe's main dive bomber, as it was underpowered in his opinion. On 9 June 1936, the RLM ordered cessation of development in favour of the Heinkel He 118, a rival design. Udet cancelled the order the next day, and development continued.
On 27 July 1936, Udet crashed the He 118 prototype, He 118 V1 D-UKYM. That same day, Charles Lindbergh was visiting Ernst Heinkel, so Heinkel could communicate with Udet only by telephone. According to this version of the story, Heinkel warned Udet about the propeller's fragility. Udet failed to consider this, so in a dive, the engine oversped and the propeller broke away. Immediately after this incident, Udet announced the Stuka the winner of the development contest.
Refinements
Despite being chosen, the design was still lacking and drew frequent criticism from Wolfram von Richthofen. Testing of the V4 prototype in early 1937 revealed several problems. The Ju 87 could take off in and climb to in eight minutes with a bomb load, and its cruising speed was. Richthofen pushed for a more powerful engine. According to the test pilots, the Heinkel He 50 had a better acceleration rate, and could climb away from the target area much more quickly, avoiding enemy ground and air defences. Richthofen stated that any maximum speed below was unacceptable for those reasons. Pilots also complained that navigation and powerplant instruments were mixed together, and were not easy to read, especially in combat. Despite this, pilots praised the aircraft's handling qualities and strong airframe.These problems were to be resolved by installing the DB 600 engine, but delays in development forced the installation of the Jumo 210 D inverted V-12 engine. Flight testing began on 14 August 1936. Subsequent testing and progress fell short of Richthofen's hopes, although the machine's speed was increased to at ground level and at, while maintaining its good handling ability.