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he Junkers Ju 87 or Stuka (from Sturzkampfflugzeug, "dive bomber") was a two-man (pilot and rear gunner) German dive bomber and ground-attack aircraft. Designed by Hermann Pohlmann, the Stuka first flew in 1935 and made its combat debut in 1936 as part of the Luftwaffe's Condor Legion during the Spanish Civil War.
The aircraft was easily recognisable by its inverted gull wings and fixed spatted undercarriage. Upon the leading edges of its faired maingear legs were mounted the Jericho-Trompete ("Jericho trumpet") wailing sirens, becoming the propaganda symbol of German air power and the blitzkrieg victories of 1939–1942. The Stuka's design included several innovative features, including automatic pull-up dive brakes under both wings to ensure that the aircraft recovered from its attack dive even if the pilot blacked outfrom the high g-forces.
Although sturdy, accurate, and very effective against ground targets, the Ju 87, like many other dive bombers of the war, was vulnerable to modern fighter aircraft. Its flaws became apparent during theBattle of Britain; poor manoeuvrability and a lack of both speed and defensive armament meant that the Stuka required a heavy fighter escort to operate effectively.
The Stuka operated with further success after the Battle of Britain, and its potency as a precision ground-attack aircraft became valuable to German forces in the Balkans Campaign, the African and Mediterranean theaters and the early stages of the Eastern Front campaigns where Soviet fighter resistance was disorganised and in short supply.
Once the Luftwaffe lost air superiority on all fronts, the Ju 87 once again became an easy target for enemy fighter aircraft. In spite of this, because there was no better replacement, the type continued to be produced until 1944. By the end of the conflict, the Stuka had been largely replaced by ground-attack versions of the Focke-Wulf Fw 190, but was still in use until the last days of the war. An estimated 6,500 Ju 87s of all versions were built between 1936 and August 1944.
Some notable airmen flew the Ju 87. Oberst Hans-Ulrich Rudel was the most successful Stuka ace and the most highly decorated German serviceman of the Second World War. The vast majority of German ground attack aces flew this aircraft at some point in their careers.
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 (Plauth was killed in a flying accident in November 1927), 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 (RLM, the German aviation ministry) 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, the 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 some 450 kW (600 hp). 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 Hawk II. When he invited Walther Wever and Robert Ritter von Greim 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 1,000 m (3,300 ft) and released his 1 kg (2.2 lb) bombs at 100 m (330 ft), barely recovering and pulling out of the dive. The chief of the Luftwaffe Command Office, Walther Wever, and 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 have dive-bombing capabilities, which initially doomed the largest bomber in German front-line service — the 30 meter wingspan He 177A — into having an airframe design (due to Udet examining its design details in November 1937) that could perform "medium angle" divebombing missions, until Reichsmarschall Hermann Göring exempted the He 177A, Germany's only operational heavy bomber, from that mission profile in September 1942.
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 engine. Ten engines were ordered by Junkers on 19 April 1934 for £ 20,514, two shillings and sixpence. 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 was not completed until October 1935. However, the mostly complete Ju 87 V1 W.Nr.c 4921 (less non-essential parts) took off for its maiden flight on 17 September 1935. The aircraft originally did not carry any registration, but later was given the registration D-UBYR. The flight report, by Hauptmann Willy Neuenhofen, stated the only problem was with the small radiator, which caused the power plant to overheat.
The Ju 87 V1, powered by a Rolls-Royce Kestrel V12 cylinder liquid-cooled engine, and 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 singlevertical stabiliser tail design. To withstand strong forces during a dive, heavy plating was fitted, along with brackets riveted to the frame and longeron, 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 in-line 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 stabilizers removed and a single tail fin installed due to fears over stability. Due to a shortage of power plants, 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 Jumo 210Aa power plant, which a year later was replaced by a Jumo 210 G (W.Nr. 19310). Although the testing went well, and the pilot, Flight Captain Hesselbach, praised its performance, Wolfram von Richthofen 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 only communicate with Udet 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.
Despite being chosen, the design was still lacking and drew frequent criticism from Wolfram von Richthofen. Testing of the V4 prototype (A Ju 87 A-0) in early 1937 revealed several problems. The Ju 87 could take off in just 250 m (820 ft) and climb to 1,875 m (6,152 ft) in just eight minutes with a 250 kg (550 lb) bomb load, and its cruising speed was 250 km/h (160 mph). However, Richthofen pushed for a more powerful engine. According to the test pilots, theHeinkel 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 350 km/h (220 mph) 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 Daimler-Benz DB 600 engine, but delays in development forced the installation of the Jumo 210 Da in-line 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 280 km/h (170 mph) at ground level and 290 km/h (180 mph) at 1,250 m (4,100 ft), while maintaining its good handling ability.
The Ju 87 was a single-engined all-metal cantilever monoplane. It had a fixedundercarriage and could carry a two-person crew. The main construction material was duralumin, and the external coverings were made of Duralumin sheeting. Parts that were required to be of strong construction, such as the wing flaps, were made of Pantal (a German aluminum alloy containing titanium as a hardening element) and its components made of Elektron. Bolts and parts that were required to take heavy stress were made of steel.
The Ju 87 was fitted with detachable hatches and removable coverings to aid and ease maintenance and overhaul. The designers avoided welding parts wherever possible, preferring moulded and cast parts instead. Large airframe segments were interchangeable as a complete unit, which increased speed of repair.
The airframe was also subdivided into sections to allow transport by road or rail. The wings were of standard Junkers double-wing construction. This gave the Ju 87 considerable advantage on take-off; even at a shallow angle, large lift forces were created through the aerofoil, reducing take-off and landing runs.
In accordance with the Aircraft Certification Center for "Stress Group 5", the Ju 87 had reached the acceptable structural strength requirements for a dive bomber. It was able to withstand diving speeds of 600 km/h (370 mph) and a maximum level speed of 340 km/h (210 mph) near ground level, and a flying weight of 4,300 kg (9,500 lb). Performance in the diving attack was enhanced by the introduction of dive brakes under each wing, which allowed the Ju 87 to maintain a constant speed and allow the pilot to steady his aim. It also prevented the crew from suffering extreme g forces and high acceleration during "pull-out" from the dive.
The fuselage had an oval cross-section and housed a water-cooled inverted V-12 engine. The cockpit was protected from the engine by a firewall ahead of the wing center section where the fuel tanks were located. At the rear of the cockpit, the bulkhead was covered by a canvas cover which could be breached by the crew in an emergency, enabling them to escape into the main fuselage. The canopy was split into two sections and joined by a strong welded steel frame. The canopy itself was made of Plexiglas and each compartment had its own "sliding hood" for the two crew members.
The engine was mounted on two main support frames that were supported by two tubular struts. The frame structure was triangulated and emanated from the fuselage. The main frames were bolted onto the power plant in its top quarter. In turn, the frames were attached to the firewall by universal joints. The firewall itself was constructed from asbestos mesh with dural sheets on both sides. All conduits passing through had to be arranged so that no harmful gases could penetrate the cockpit.
The fuel system comprised two fuel tanks between the main (forward) and rear spars of the (inner) anhedral wing section of the port and starboard wings, each with 240-litre (63 US gal) capacity. The tanks also had a predetermined limit which, if passed, would warn the pilot via a red warning light in the cockpit. The fuel was injected via a pump from the tanks to the power plant. Should this shut down, it could be pumped manually using a hand-pump on the fuel cockArmature. The powerplant was cooled by a 10-litre (2.6 US gal), ring-shaped aluminium water container situated between the propeller and engine. A further container of 20-litre (5.3 US gal) was positioned under the engine.
The control surfaces operated in much the same way as other aircraft, with the exception of the innovative automatic pull-out system. Releasing the bomb initiated the pull-out, or automatic recovery and climb, upon the deflection of the dive brakes. The pilot could override the system by exerting significant force on the control column and taking manual control.
The wing was the most unusual feature. It consisted of a single center section and two outer sections installed using four universal joints. The center section had a large negative dihedral (anhedral) and the outer surfaces a positive dihedral. This created the inverted gull, or "cranked", wing pattern along the Ju 87's leading edge. The shape of the wing improved the pilot's ground visibility and also allowed a shorter undercarriage height. The center section protruded by only 3 m (9 ft 10 in) on either side.
The offensive armament was two 7.92 mm (.312 in) MG 17 machine guns fitted one in each wing outboard of undercarriage, operated by a mechanical pneumatics system from the pilot's control column. The rear gunner/radio operator operated one 7.92 mm (.312 in) MG 15 machine gun for defensive purposes.
The engine and propeller had automatic controls, and an auto-trimmer made the aircraft tail-heavy as the pilot rolled over into his dive, lining up red lines at 60°, 75° or 80° on the cockpit side window with the horizon and aiming at the target with the sight of the fixed gun. The heavy bomb was swung down clear of the propeller on crutches prior to release.
Flying at 4,600 m (15,100 ft), the pilot located his target through a bombsight window in the cockpit floor. The pilot moved the dive lever to the rear, limiting the "throw" of the control column. The dive brakes were activated automatically, the pilot set the trim tabs, retarded his throttle and closed the coolant flaps. The aircraft then rolled 180°, automatically nosing the aircraft into a dive. Red tabs protruded from the upper surfaces of the wing as a visual indicator to the pilot that, in case of a g-induced black-out, the automatic dive recovery system would be activated. The Stuka dived at a 60-90° angle, holding a constant speed of 500–600 km/h (350-370 mph) due to dive-brake deployment, which increased the accuracy of the Ju 87's aim.
When the aircraft was reasonably close to the target, a light on the contact altimeter came on to indicate the bomb-release point, usually at a minimum height of 450 m (1,480 ft). The pilot released the bomb and initiated the automatic pull-out mechanism by depressing a knob on the control column. An elongated U-shaped crutch located under the fuselage swung the bomb out of the way of the propeller, and the aircraft automatically began a 6 g pullout. Once the nose was above the horizon, dive brakes were retracted, the throttle was opened, and the propeller was set to climb. The pilot regained control and resumed normal flight. The coolant flaps had to be reopened quickly to prevent overheating. The automatic pull-out was not liked by all pilots. Helmut Mahlke later said that he and his unit disconnected the system because it allowed the enemy to predict the Ju 87s recovery pattern and height, making it easier for ground defences to hit an aircraft.
Physical stress on the crew was severe. Human beings subjected to more than 5 g forces in a seated position will suffervision impairment in the form of a grey veil known to Stuka pilots as "seeing stars". They lose vision while remaining conscious; after five seconds, they black out. The Ju 87 pilots experienced the visual impairments most during "pull-up" from a dive.
Eric "Winkle" Brown RN, a British test pilot and Commanding Officer of Captured Enemy Aircraft Flight section, tested the Ju 87 at RAE Farnborough. He said of the Stuka, "I had flown a lot of dive-bombers and it’s the only one that you can dive truly vertically. Sometimes with the dive-bombers...maximum dive is usually in the order of 60 degrees.. When flying the Stuka, because it’s all automatic, you are really flying vertically... The Stuka was in a class of its own."
Extensive tests were carried out by the Junkers works at their Dessau plant. It was discovered that the highest load a pilot could endure was 8.5 g for three seconds, when the aircraft was pushed to its limit by the centrifugal forces. At less than 4 g, no visual problems or loss of consciousness were experienced. Above 6 g, 50% of pilots suffered visual problems, or "grey" out. With 40%, vision vanished altogether from 7.5 g upwards and black-out sometimes occurred.Despite this blindness, the pilot could maintain consciousness and was capable of "bodily reactions". However, after more than three seconds, half the subjects passed out. The pilot would regain consciousness two or three seconds after the centrifugal forces had dropped below 3 g and had lasted no longer than three seconds. In a crouched position, pilots could withstand 7.5 g and were able to remain functional for a short duration. In this position, Junkers concluded that ⅔ of pilots could withstand 8 g and perhaps 9 g for three to five seconds without vision defects which, under war conditions, was acceptable. During tests with the Ju 87 A-2, new technologies were tried out to reduce the effects of g forces. The pressurised cabin was of great importance during this research. Testing revealed that at high altitude, even 2 g could cause death in an unpressurised cabin and without appropriate clothing. This new technology, along with special clothing and oxygen masks, was researched and tested. When the United States Army occupied the Junkers factory at Dessau on 21 April 1945, they were both impressed at and interested in the medical flight tests with the Ju 87.
The concept of dive bombing became so popular among the leadership of the Luftwaffe that it became almost obligatory in new aircraft designs. Later bomber models like the Junkers Ju 88 and the Dornier Do 217 were equipped for dive bombing. The Heinkel He 177 strategic bomber was initially supposed to have dive bombing capabilities, a requirement that contributed to the failure of the design, with the requirement not rescinded until September 1942 byReichsmarschall Hermann Göring.
Once the Stuka became too vulnerable to fighter opposition on all fronts, work was done to develop a replacement. None of the dedicated close-support designs on the drawing board progressed far due to the impact of the war and technological difficulties. So the Luftwaffe settled on the Focke-Wulf Fw 190 fighter aircraft, with the Fw 190F becoming the ground-attack version. The Fw 190F started to replace the Ju 87 for day missions in 1943, but the Ju 87 continued to be used as a night nuisance-raider until the end of the war.
The second prototype had a redesigned single vertical stabiliser and a 610 PS (449 kW or 602 hp) Junkers Jumo 210 A engine installed, and later the Jumo 210 Da. The first A series variant, the A-0, was of all-metal construction, with an enclosed cockpit. To ease the difficulty of mass production, the leading edge of the wing was straightened out and theailerons' two aerofoil sections had smooth leading and trailing edges. The pilot could adjust the elevator and rudder trim tabs in flight, and the tail was connected to the landing flaps, which were positioned in two parts between the ailerons and fuselage. The A-0 also had a flatter engine cowling, which gave the pilot a much better field of vision. In order for the engine cowling to be flattened, the engine was set down nearly 0.25 m (9.8 in). The fuselage was also lowered along with the gunner's position, allowing the gunner a better field of fire.
The RLM ordered seven A-0s initially, but then increased the order to 11. Early in 1937, the A-0 was tested with varied bomb loads. The underpowered Jumo 210A, as pointed out by von Richthofen, was insufficient, and was quickly replaced with the Jumo 210D power plant.
The A-1 differed from the A-0 only slightly. As well as the installation of the Jumo 210D, the A-1 had two 220 L (60 US gal) fuel tanks built into the inner wing, but it was not armoured or protected. The A-1 was also intended to be fitted with two 7.92 mm (.312 in) MG 17 machine guns in each wing, but this was dropped due to excessive weight. The two that remained were fed a total of 500 rounds of ammunition, stored in the undercarriage "spats". The pilot relied on the Revi C 21C gun sight for the two MG 17s. The gunner had only a single 7.92 mm (.312 ) MG 15, with 14 drums of ammunition, each containing 75 rounds. This represented a 150-round increase in this area over the Ju 87 A-0. The A-1 was also fitted with a larger 3.3 m (11 ft) propeller.
The Ju 87 was capable of carrying a 500 kg (1,100 lb) bomb, but only if not carrying the rear gunner/radio operator as, even with the Jumo 210D power plant, the Ju 87 was still underpowered for operations with more than a 250 kg (550 lb) bomb load. All Ju 87 As were restricted to 250 kg (550 lb) weapons (although during the Spanish Civil War missions were conducted without the gunner).
The Ju 87 A-2 was retrofitted with the Jumo 210Da fitted with a two-stage supercharger. The only further significant difference between the A-1 and A-2 was the H-PA-III controllable-pitch propeller. By mid-1938, 262 Ju 87 As had been produced, 192 from the Junkers factory in Dessau, and a further 70 from Weser Flugzeugbau ("Weserflug" - WFG) inLemwerder near Bremen. The new, more powerful, Ju 87B model started to replace the Ju 87A at this time.
The Ju 87 B series was to be the first mass-produced variant. A total of six pre-production Ju 87 B-0 were produced, built from Ju 87 An airframes. Test flights began from the summer of 1937. A small number, at least three, served as conversion Cs or Es for potential naval variants.
The first production version was the Ju 87 B-1, with a considerably larger engine, itsJunkers Jumo 211D generating 1,200 PS (883 kW or 1,184 hp), and completely redesigned fuselage and landing gear. This new design was again tested in Spain, and after proving its abilities there, production was ramped up to 60 per month. As a result, by the outbreak of World War II, the Luftwaffe had 336 Ju 87 B-1s on hand. The B-1 was also fitted with "Jericho trumpets", essentially propeller-driven sirens with a diameter of 0.7 m (2.3 ft) mounted on the wing's leading edge directly forward of the landing gear, or on the front edge of the fixed main gear fairing. This was used to weaken enemy morale and enhance the intimidation of dive-bombing. After the enemy became used to it, however, they were withdrawn. The devices caused a loss of some 20–25 km/h (10-20 mph) through drag. Instead, some bombs were fitted with whistles on the fin to produce the noise after release.
The trumpets were a suggestion from Generaloberst Ernst Udet (but some authors say the idea originated from Adolf Hitler). The Ju 87 B-2s that followed had some improvements and were built in a number of variants that included ski-equipped versions (the B-1 also had this modification), and at the other end, with a tropical operation kit called the Ju 87 B-2 trop. Italy's Regia Aeronautica received a number of the B-2s and named them the "Picchiatello", while others went to the other members of the Axis, including Hungary, Bulgaria and Romania. The B-2 also had an oil hydraulic system for closing the cowling flaps. This continued in all the later designs.
The tropicalised versions were initially named the Ju 87 B-2/U1. This was eventually designated the Ju 87 B-2 trop, equipped with tropical emergency equipment and sand filters for the powerplant.
Production of the Ju 87 B started in 1937. 89 B-1s were to be built at Junkers' factory in Dessau and another 40 at the Weserflug plant in Lemwerder by July 1937. Production would be carried out by the Weserflug company after April 1938, but Junkers continued producing Ju 87 up until March 1940. Total production amounted to 697 B-1s (311 by Junkers, 386 by Weserflug) and 225 B-2s (56 by Junkers, 169 by Weserflug). The last Ju 87B rolled off the production lines in October 1940.
A long range version of the Ju 87B was also built, known as the Ju 87R, the letter allegedly being an abbreviation for Reichweite, "(operational) range". They were primarily intended for anti-shipping missions. The Ju 87R had a B-series airframe with an additional oil tank and fuel lines to the outer wing stations to permit the use of two 300 L (79.25 US gal) standardised capacity under-wing drop tanks, used by a wide variety of Luftwaffe aircraft through most of the war. This increased fuel capacity to 1,080 litres (500 L in main fuel tank of which 480 L where usable + 600 L from drop tanks). To prevent overload conditions, bomb carrying ability was often restricted to a single 250 kg (550 lb) bomb if the aircraft was fully loaded with fuel.
The Ju 87 R-1 had a B-1 airframe with the exception of a modification in the fuselage which enabled an additional oil tank. This was installed to feed the engine due to the increase in range after the addition of the extra fuel tanks.
The Ju 87 R-2 had the same airframe as the B-2, and strengthened to ensure it could withstand dives of 600 km/h (370 mph). The Jumo 211D in-line engine was installed, replacing the R-1s Jumo 211A. Due to an increase in overall weight by some 700 kg (1,500 lb), the Ju 87 R-2 was 30 km/h (19 mph) slower than the Ju 87 B-1 and had a lower service ceiling. The Ju 87 R-2 had an increased range advantage of 360 km (220 mi). The R-3 and R-4 were the last R variants developed. Only a few were built. The R-3 was an experimental tug for gliders and had an expanded radio system so the crew could communicate with the glider crew by way of the tow rope. The R-4 differed from the R-2 in the Jumo 211J powerplant.
Total production amounted to 972 Ju 87R (105 R-1, 472 R-2, 144 R-4), all built by Weserflug. The last Ju 87R rolled off the production lines in October 1941.
On 18 August 1937, the RLM decided to introduce the Ju 87 Tr(C). The Ju 87 C was intended to be a dive and torpedo bomber for the Kriegsmarine. The type was ordered into prototype production and available for testing in January 1938. Testing was given just two months and was to begin in February and end in April 1938. The prototype V10 was to be a fixed wing test aircraft, while the following V11 would be modified with folding wings. The prototypes were Ju 87 B-0 airframes powered by Jumo 211 A engines. Owing to delays, the V10 was not completed until March 1938. It first flew on 17 March and was designated Ju 87 C-1. On 12 May, the V11 also flew for the first time. By 15 December 1939, 915 arrested landings on dry land had been made. It was found the arresting gear winch was too weak and had t
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