The Junkers Ju 87, popularly known as the "Stuka",[b] 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 (1939–1945).
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" (noise device), 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.
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 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 Stuka had inverted gull wings, as shown in this photograph. Also visible are the two separate sliding "hoods" of the canopy.
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 (W.Nr. 19310). 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.
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 250 m and climb to 1,875 m in eight minutes with a 250 kg bomb load, and its cruising speed was 250 km/h . 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 350 km/h 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 280 km/h at ground level and 290 km/h at 1,250 m , while maintaining its good handling ability.
The Ju 87 was a single-engined all-metal cantilever monoplane. It had a fixed undercarriage 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 aluminium 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 Centre 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 and a maximum level speed of 340 km/h near ground level, and a flying weight of 4,300 kg . 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, in most examples, a Junkers Jumo 211 water-cooled inverted V-12 engine. The cockpit was protected from the engine by a firewall ahead of the wing centre 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 engine's 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 engine. Should this shut down, it could be pumped manually using a hand-pump on the fuel cock armature.The powerplant was cooled by a 10-litre , ring-shaped aluminium water container situated between the propeller and engine. A further container of 20-litre 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 centre section and two outer sections, each installed using four universal joints. The centre 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 leading edge. The shape of the wing improved the pilot's ground visibility and also allowed a shorter undercarriage height. The centre section protruded by only 1 m on either side.
The offensive armament was two 7.92 mm 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 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 releas
