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The Junkers Ju 86 was a disappoint medium bomber developed at the same time as the Heinkel He 111, and that had been phased out of front line service by the start of the Second World War. It remains of interest because it was one of the few military aircraft to use diesel engines and because of its later use in high altitude work.
The Design
The Ju 86 was a twin-engined low-wing monoplane, with a twin fin and rudder tail and of stressed-skin metal construction. Unlike most early Junkers aircraft it used a smooth skin in place of the normal corrugated skin.
The first prototypes had heavily tapered wings, and suffered from poor stability, so from the fourth and fifth prototype a new wing was introduced, with increased chord towards the tips (the distance from the front to the back of the wing). The undercarriage was mounted at the wing roots and retracted outwards, giving the aircraft a very narrow wheel base.
Development
Junkers received an order to built five prototype aircraft, three military and two civil, in the spring of 1934. A full scale mock-up was ready by April, and the first prototype, then known as the Ju 86a, made its maiden flight on 4 November 1934 (it was later redesignated as the V 1). The lack of Jumo 205 diesel engines meant that this aircraft was powered by Siemens SAM 22 engines, as was the second prototype when it first flew in March 1935.
In the summer of 1935 the Ju 86 and He 111 underwent trails at Rechlin. The Ju 86 performed disappointingly. It was sluggish to handle, stability was poor, and the original wing design was too prone to stalling. The Heinkel aircraft was the clear winner, and after that the Ju 86 was seen as at best a stop-gap aircraft.
Main Variants
The Ju 86A was the first bomber version to enter production. It was based on the V 5 prototype, and suffered from instability
The Ju 86B was the first passenger version to be produced. It was similar to the Ju 86A, but could carry ten passengers in place of the bombs.
The Ju 86C was an improved passenger aircraft, with a 42cm long fin attached to the end of the fuselage to improve stability.
The Ju 86D was the second bomber version, and was given the same rear fin as the Ju 86C in an attempt to improve stability.
The Ju 86E saw a change of engine, from the problematic Jumo diesels to the BMW 132 radial engine, a licence-built version of the Pratt & Whitney Hornet.
The Ju 86G was the last standard bomber version, and had a redesigned all-glazed nose and modified cockpit.
The Ju 86K was the export version of the bomber and was produced in a number of different versions with different engines.
The Ju 86P was a high-altitude reconnaissance aircraft and bomber that operated above the height reachable by Allied fighter aircraft until the summer of 1942 when three were shot down by RAF Spitfires over Egypt.
The Ju 86R was an improved version of the Ju 86P that could reach higher altitudes.
The Ju 86Z was the export version of the civil version of the Ju 86.
Service Record
The Junkers Ju 86 had a very short service career in German hands, and had been withdrawn from front line units within two years of its combat debut. That debut came in Spain in the summer of 1937, where five Ju 86D-1s flew with VB/88. The main problem were the diesel engines, which didn't respond well to changes in power, and proved to be difficult to keep in service. By September 1939 all but thirty of the Luftwaffes fleet of Ju 86s had been posted to C-class pilot training schools, while the remaining thirty were being used by IV/KG 1 for conversion training.
The Ju 86 did see some limited wartime service with the Luftwaffe. During the siege of Stalingrad 58 aircraft were taken from the schools and equipped two transport groups (KGrzb V 21 and 22). The Ju 86 was very vulnerable to Soviet attack, and by the end of the siege 42 of the aircraft had been destroyed. The rest were returned to the training schools. They were summoned to the front again over the winter of 1943/44 when a number of Ju 86s were used in anti-partisan operations in the Balkans.
The Ju 86 was produced in a number of export versions, with the designation Ju 86K for military and Ju 86Z for civil aircraft. Sweden, Hungary, Chile, Manchuria, Portugal, Austria purchased the military version, while Switzerland, Bolivia and South Africa purchased the civilian version. Bolivia and South Africa both later took their civil aircraft into the military.
Hungary and South Africa both used their aircraft in combat, although on opposite sides. Sixty three Ju 86K-2s were delivered to Hungary, and took part in the fighting in the Soviet Union, before being withdrawn due to heavy losses during 1942.
Seventeen Ju 86Z-3s and Z-7s were delivered to South African Airways. In 1939 the surviving fifteen aircraft were taken over by the South African Air Force, and were used by Nos.12, 16 and 22 Squadrons. Ten were lost in accidents and one was shot down by the Italians, before the surviving aircraft were moved to No.69 Air School.