Airliner and medium bomber aircraft
The Junkers Ju 86 is a monoplane bomber and civilian airliner designed and produced by the German aircraft manufacturer Junkers.
It was designed during the mid-1930s in response to a specification for a modern twin-engined aircraft suitable for use as both a high-speed airliner and a bomber. Junkers responded with a low-winged twin-engined all-metal monoplane; unusually, it was intended to be powered by Junkers Jumo 205 diesel engines instead of petrol engines for greater fuel efficiency. It also had a smooth metal skin instead of the company's traditional corrugated exterior. On bomber-configured aircraft, bombs were carried vertically in four fuselage cells behind the cockpit; these bomb cells were replaced by seating for up to ten passengers on the civil airliner version of the Ju 86. On 4 November 1934, the first prototype, powered by Siemens SAM 22 radial engines, made its maiden flight; on 4 April 1935, the third prototype, which was the first civil-configured aircraft, flew for the first time.
The civil-oriented Ju 86 models were operated by a range of airlines, including the German flag carrier Deutsche Luft Hansa, Manchukuo National Airways, South African Airways, Iberia Airlines and AB Aerotransport amongst others. Some civilian aircraft would be converted into military aircraft following the outbreak of the Second World War. The type was employed by various air forces on both sides of the conflict, although the first military use of the Ju 86 was during the Spanish Civil War, where it was flown by the Condor Legion with mixed results. The Luftwaffe deployed its Ju 86s during the invasion of Poland, but opted to withdraw its diesel-engined aircraft fairly promptly while the radial-engined Ju 86 models were predominantly assigned to training roles thereafter. During late 1942, Ju 86s, along with all other available transport aircraft, were pulled from training schools to reinforce the "Luftwaffe"'s transport force in its attempt to supply the German 6th Army besieged at Stalingrad, although this attempt was soon ended due to Soviet advances.
The "Ju 86P", which emerged in early 1940, possessed considerable high altitude performance as a result of its longer wingspan, pressurized cabin, Junkers Jumo 207A-1 turbocharged diesel engines; used as both a bomber and reconnaissance aircraft, it was used as a "nuisance bomber" for a time over England until effective interception by modified Supermarine Spitfires led to its withdrawal. At one point, Junkers was developing the "Ju 86R", fitted with even larger wings and new engines, to attain even higher altitudes, but this model never progressed beyond the prototype stage. By the twenty-first century, only a single Ju 86 is known to still exist; it is on permanent static display at the Swedish Air Force Museum outside Linköping.
Design and development.
Background.
The origins of the Junkers Ju 86 are closely linked to the clandestine build-up of "Luftwaffe" during the mid-1930s. During 1934, the recently created German "Reichsluftfahrtministerium" (RLM) and the German flag carrier Deutsche Luft Hansa worked together to produce a specification for a twin use aircraft, capable of operating both as a high-speed airliner for Deutsche Luft Hansa and as a medium bomber for the Luftwaffe. Distinct civil and military variants of the aircraft were sought; however, where the requirements were not fully compatible with one another, it was deemed that military needs took precedence over those of the civil side of the programme.
Two German aircraft manufacturers, Junkers and Heinkel, were both approached regarding this specification; each company received an initial order for five prototypes (three military and two civil) of their designs, these being the Ju 86 and Heinkel He 111 respectively. Junkers' opted for a low-winged twin-engined monoplane that featured all-metal stressed skin construction. Unlike the majority of Junkers' previous designs, the Ju 86 discarded the typical corrugated skinning in favour of smooth metal skinning, which helped to reduce drag. It was intended to be powered by Junkers Jumo 205 diesel engines, which although heavy, gave better fuel efficiency than conventional petrol engines. This decision made the Ju 86 one of the earliest quantity production aircraft to use diesel propulsion.
The wing of the Ju 86, which was tapered, comprised two primary spars and one auxiliary spar. It was outfitted with distinctive Junkers control surfaces on the wing, similar to those on the Junkers Ju 52, that were hinged below the wing's trailing edge, with the outboard section on each side functioning as an aileron, and the inner section functioning as a wing flap. The aircraft was fitted with a retractable main-gear conventional undercarriage with a fixed tailwheel, and twin fins and rudders. Unusually, the main undercarriage members were attached to the wing roots and outwardly retracted into recesses within the wings; this arrangement meant that the undercarriage had a particularly narrow track.
The bomber aircraft had a crew of four: a pilot, navigator, radio operator/bombardier and gunner. Defensive armament consisted of three machine guns: at the nose, at a dorsal position, and within a retractable ventral position. Bombs were carried vertically in four fuselage cells behind the cockpit. The airliner version replaced these bomb cells with seating for ten passengers; furthermore, the fuel tanks were relocated from the fuselage to the wings.
Into flight.
As the Jumo 205 was unavailable when the first prototype airframe was completed, the bomber-configured Ju 86ab1 was fitted with Siemens SAM 22 radial engines instead when it performed its maiden flight on 4 November 1934. Early flight trials were reportedly demonstrated the prototype to possess unsatisfactory control and stability; modifications were made. The second prototype, which was also a bomber, flew during January 1935. The third Ju 86, the first civil prototype, flew on 4 April 1935. The fourth and fifth prototypes, which were more representative of production aircraft, were furnished with a new wing design with an increased chord, and thereby wing area, towards the tips.
During late 1935, production of both pre-series military and civil aircraft commenced. In April 1936, full-rate production of the Ju 86A-1 bomber was achieved. Many of the early modifications made were centred around increasing the aircraft's stability, such as the addition of a spine-like dorsal fin on the tail end of the fuselage on the Ju 86C. Production was quickly transitioned to the improved Ju 86D, the chief differences of which being a modified tail cone that improved stability and an almost 50 per cent increase in fuel capacity over that of the Ju 86A. Durign the late 1930s, demand for the type was such that rival firm Henschel became involved in the production program.
Early use of the Jumo-powered Ju 86 bomber in the Spanish Civil War showed that it was inferior to the He 111, with the diesel engines being unsuitable for rough treatment during combat and thus difficult to keep operational. Accordingly, production plans of the type were promptly cut back. One Ju 86 had already been converted to use radial engines as a testbed for possible export versions, and this showed improved reliability. Production switched to a version powered by the BMW 132 engine, the Ju 86E, the production of which continued though to 1938. The sudden end to production without advance warning meant that there were still enough component parts to construct a further 1,000 aircraft.
While the Ju 86 was deemphasised as a bomber as time went on, Junker opted to continue development of the aircraft as a high altitude platform for both reconnaissance and bombing missions. The "Ju 86P", which possessed a longer wingspan, pressurized cabin, Junkers Jumo 207A-1 turbocharged two-stroke, opposed-piston diesel engines and a two-man crew, could fly higher than 12,000 m (39,000 ft), where it was felt to be safe from enemy fighters. Furthermore, it could be produced by remanufacturing existing Ju 86D airframes.
During early 1942, Junkers was working on the "Ju 86R", which used even larger wings and new engines that were reportedly capable of even higher altitudes - up to 16,000 m (52,500 ft) - in order to continue evading increasingly advanced interceptors. While a few aircraft were built and delivered to the "Luftwaffe" during 1943, production was limited to a small quantity of aircraft. Further advanced models, such as the Ju 86 R-3 and the Ju 186, but these never left the drawing board.
Export variants.
Civil variants, introduced in 1936, were designated Ju 86Z in three different models differing in their engines. The Jumo-engined Ju 86Z-1 (corresponding to the former B-0 or C-1) was sold to Swissair (one), Airlines of Australia (one), and LAN-Chile (three). The BMW 132H-powered Ju 86Z-2 was sold to DLH (two) and the para-military Manchukuo Air Transport (five or more). The Pratt &amp; Whitney R-1690 Hornet-engined Ju 86Z-7 was delivered to AB Aerotransport (ABA) of Sweden (one, for use as a mail carrier), Lloyd Aéreo Boliviano (three), and South African Airways (SAA) (seventeen). The ABA aircraft was later transferred to the Swedish Air Force, with which it served, under the designation Tp 9, until 1958. South African Airways' original intention was to have its Ju 86s powered by 745 hp Rolls-Royce Kestrels. Six aircraft for SAA, flown with these engines, were refitted with Hornets before delivery, and the remainder were also Hornet-powered.
The "Ju 86K" was an export model, also built under license in Sweden by Saab as the B 3 with (905 hp) Bristol Mercury XIX radial engines. Several aircraft remained in service with the Swedish Air Force until 1958. A few were converted for radio interception activities.
Operational history.
The bomber was field-tested in the Spanish Civil War by the Condor Legion. Four Ju 86D-1s arrived in Spain in early February 1937, but after a few sorties one of them was shot down in late February–early March 1937 by Republican fighters. A replacement aircraft was sent from Germany, but after two more were damaged in landing accidents, the remaining two aircraft were sold to the Nationalist air force, where they remained in service until at least the end of the Civil War. The Ju 86 had proved to be generally inferior to the Heinkel He 111 evaluated at the same time.
A single "Gruppe" of Ju 86 bombers (III KG 1 "Hindenburg") remained in operational service at the start of the Second World War and were used in the invasion of Poland, but replaced soon after. The diesel-engined Ju 86A and Ds were quickly retired while the radial-engined Ju 86E and Gs were transferred to bomber training schools. Soon after the conflict started, the (Air Fleet) commanders raided their training schools for Ju 52s as transport aircraft, together with their experienced aircrew instructors. This depletion continued with the formation of special bomber crews for the invasions of Norway, the Low Countries, and Crete. This was to a severe blow to the pilot training programme, and Lt-Colonel Paul Deichmann, Chief of Staff to the Luftwaffe's Chief of Training Helmuth Wilberg suggested that Ju 86s with dual controls and instruments could be easily produced to replace the appropriated Ju 52s. However, his contention that "the need for air transport services would soon reach tremendous proportions" was simply brushed aside by the commander-in-chief of the "Luftwaffe", Hermann Göring.
In late 1942, all available aircraft, including Ju 86s, were pulled out of the training schools to reinforce the "Luftwaffe"'s transport force in its attempt to supply the German 6th Army, besieged at Stalingrad. The Ju 86s formed two transport "Gruppen", equipped with 58 aircraft, operating out of Tatsinskaya Airfield. They were unsuited to the transport role, and suffered heavy losses (42 Ju 86s were lost by the end of January 1943) before being forced out of the airlift when the Soviets captured Tatsinskaya, not having the range to reach Stalingrad from the replacement airfields. More than 40 Ju 86s were lost in this endeavour while the survivors were reallocated to training bomber crews.
Ju 86s operated by the Allies in the Second World War included 17 early-model units that had been in use by South African Airways. When the conflict broke out, these aircraft were militarised and armed as bombers with defensive guns and external bomb racks. These aircraft were initially used for coastal patrols along with the sole Ju 86K-1, playing an important role in the interception of the German blockade runner SS "Watussi" in December 1939. In May 1940, they were used to re-equip No. 12 Squadron SAAF, which was deployed in the East African Campaign from June 1940. It flew its first bombing missions on 14 June 1940. As more modern aircraft became available, the South African Ju 86s were passed from squadron to squadron, seeing their last use with No. 22 Squadron SAAF, which used it along with the Avro