The Junkers Ju 87 or Stuka as it became universally known (from Sturzkampfflugzeug or German: dive bomber) was a German combat aircraft operational from 1937 and throughout World War II, and easily recognisable by its inverted gull wings, fixed undercarriage and its infamous Jericho-Trompete (Jericho Trumpet) wailing siren — though the siren was only fitted to a few aircraft because of the extra drag induced on the rather slow aircraft.
The Stuka's design included some innovative features, including automatic pull-up dive brakes under both wings to ensure that the plane recovered from its attack dive even if the pilot blacked out from the high acceleration, and a wind-powered siren under its nose (later mounted to the front upper section of each fixed landing gear strut) that wailed during dives to frighten its victims. These were named Jericho-Trompeten, or "Trumpets of Jericho", by Junkers and were a form of psychological warfare. Its rugged fixed undercarriage allowed it to land and take-off from improvised airstrips close to the battlefront, giving close support to the advancing German forces. 5,752 Ju 87 of all versions were built between 1936 and August 1944.
Although sturdy, accurate, and very effective, the Stuka suffered from low speed and poor maneuverability, with little defensive armament, making it highly vulnerable to enemy fighters. The Germans learned during the Battle of Britain that air superiority must be obtained before ground attack aircraft could be effectively used. After the Battle of Britain, the Stuka was little used in Western Europe, but it remained effective further south where Allied fighters were in short supply, most notably in the battles of Crete, Malta and Leros.
Stukas were used in vast numbers on the Eastern Front, although the steady rise in Soviet airpower as the war progressed meant that Stuka squadrons suffered very heavy losses by the final stages of the war.
Hans-Ulrich Rudel was the most notable Stuka ace, and the most highly decorated German soldier of World War II. (Hermann Goering was awarded the Großkreuz des eisernen Kreuzes, but not for achievements in battle.)
In the early 1920's the Dessau-based Junkers Flugzeugwerke AG concentrated upon military rather than civil aircraft. One such product was the Junkers K 47. The K 47 first flew in 1929, and was found to be capable of carrying a 100 kg bomb-load. After the Nazis had come to power they were designated A 48s, although these machines had "uncranked" wings and twin tail-fin units. Despite initial competition from the Henschel Hs 123 the Reichsluftfahrtministerium turned to Herman Pohlmann of Junkers and co-designer of the K 47 (the other, Karl Plauth, had been killed in a flying accident).
Design of the Ju 87 had begun in 1933 as part of the Sturzbomber-programm. However the project began poorly, the Ju 87 V1, powered by a Rolls-Royce Kestrel engine V12 cylinder liquid cooled engine, and sporting a twin-tail crashed in 1935. Square twin fins and rudders proved too weak and during dive testing they collapsed and the aircraft crashed. This prompted a change of tail design to single Vertical stabilizer.
The second prototype had a redesigned single fin and rudder and a 610 PS (602 hp, 449 kW) Junkers Jumo 210A engine. After official evaluation in 1936 against three other competing aircraft, orders for 10 aircraft were placed for it, as well as for the Heinkel He 118. The initial production variant was the Ju 87 A-1, powered by a 640 PS (631 hp, 471 kW) Jumo 210C, which began to replace the Henschel Hs 123 biplanes. At least three of these aircraft were tested under operational conditions by the Condor Legion in the Spanish Civil War.
The next major variant was the Ju 87 B-1 with a considerably larger engine, its Junkers Jumo 211D generating 1,200 PS (1,184 hp, 883 kW), and the fuselage and landing gear were completely redesigned. 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 Ju 87 B-2s that followed had some improvements and were built in a number of variants that included ski-equipped versions, 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.
A long range version of the Ju 87B was also built, known as the Ju 87R. They were primarily intended for anti-shipping missions. Internal fuel capacity was increased by adding some inner-wing tanks and by using two 300-liter under-wing drop tanks.
Bomb carrying ability was reduced to a single 250 kg bomb if the aircraft was fully loaded with fuel. The naval variant of the Ju 87B was known as the Ju 87C, and these were built to operate from the aircraft carrier Graf Zeppelin. In any case the carrier was never completed, and all of these were converted back to the Ju 87B standard.
Despite having its vulnerability to enemy fighters exposed during the Battle of Britain, the Luftwaffe had no choice but to continue the Stuka's development as there was no replacement aircraft in sight. The result was the D-series. The Ju 87 D-series received better streamlined oil and water coolers, and an aerodynamically refined cockpit with better visibility and space. In addition, armor protection was increased and a new dual-barrel 7.92 mm MG 81Z machine gun with an extremely high rate of fire was installed in the rear defensive position. The engine power was increased again, the Jumo 211 J-1 now delivering 1,420 PS (1,401 hp, 1,044 kW).
Production of the D-1 variant started in 1941 with 476 deliveries, rising to 917 D-1 and D-3 in 1942. The D-series saw extensive use in the Eastern Front and the Middle East. Bomb carrying ability was massively increased from 500 kg in the B-version to 1,800 kg in the D-version (max load for short ranges, overload condition), a typical bomb load ranged from 500 to 1,200 kg.
The D-2 was a variant used as a glider tug by converting older D-series airframes. The D-3 was an improved D-1 with more armor for its ground-attack role. The D-4 designation applied to a prototype torpedo-bomber version. The Ju 87 D-5 was another ground-attack variant that appeared in mid 1943, it had the outer wing panels extended, dive brakes were removed and the wing-mounted 7.92 mm MG 17 machine guns were replaced by 20 mm MG 151 cannons.
The D-6 was not built, for unknown reasons. The D-7 was another ground attack aircraft based on D-1 airframes upgraded to D-5 standard (armor, wing cannons, extended wing panels), while the D-8 was similar to the D-7 but based on D-3 airframes. It's a common myth that the D-7 and D-8 were specifically designed and built for night fighting as they were solely based on converted airframes and used for multiple mission types.
The Ju 87E and F proposals were never built, and Junkers went straight onto the next variant. Another variant derived from the Ju 87D airframe was called the Ju 87H, and saw service as a dual-control trainer.
With the G variant the aging airframe of the Ju 87 found new life as an anti-tank aircraft. This was the final operational version of the Stuka and was deployed on the Eastern Front starting in the early months of 1943. The Ju 87G was armed with two 37 mm cannons mounted in under-wing gondolas, each loaded with a 6-round magazine of armour piercing tungsten ammunition. With these weapons the Kanonenvogel ("cannon-bird"), as it was nicknamed, proved spectacularly successful at the hands of the Luftwaffe ace Hans-Ulrich Rudel. The G-1 was converted from older D-series airframes retaining the smaller wing but without the dive brakes. The G-2 was similar to the G-1 except using the extended wing of the D-5 with 208 G-2 new built and at least 22 more converted from D-3 airframes.
While still slow, its stable attitude, large wings and low stall speed were valuable in the acquisition of slow moving targets, such as assault boats and ground vehicles. The G-1 even influenced the design of the A-10 Thunderbolt II, with Hans Rudel's book, Stuka Pilot, being required reading for all members of the A-X project.