click click click click

Junkers Ju 90/290

Few aircraft that saw operational service during World War II can have possessed a more unusual design background than the Ju 290, which in its final long-range strategic bomber form, represented the full cycle design evolution, having been developed from a commercial transport which had, itself, stemmed from a long-range strategic bomber.

The design origins of the Ju 290 dated back to early 1935 and the so-called "Ural Bomber" concept of Generalleutnant Walther Wever, the Luftwaffe's first Chief-of-Staff and an ardent protagonist of the long-range strategic bomber. The contribution of the Junkers Flugzeug und Mototenwerke to the "Ural Bomber" program had been the Ju 89, three prototypes of which had been under construction at Dessau, but the end of November 1936 , when it had become obvious that the entire program was destined to be cancelled, Junkers had requested permission of the RLM to utilize certain major components of the third prototype, the Ju 89 V3 , for a proposed transport derivative.

Permission was duly granted on January 1, 1937 with the proviso that, should the transport be ordered by Deutsche Lufthansa (DLH), alternative engines be found for the Jumo 211 or DB 600 12-cylinder liquid-cooled powerplants employed by the Ju 89 bomber. No objection was made to the retention of the DB 600 for the first transport as the wing of the Ju 89 V3 was already complete and a change to other powerplants demanded major reconstruction. Thus, the wings, engines, undercarriage and tail assembly of the Ju 89 were mated to an entirely new transport fuselage to become the Ju 909 V1 der grosse Dessauer (D-AALU).

 

Dipl.-Ing. Ernst Zindel, chief designer of the Ju 89, had initiated the first design studies for a commercial version of the bomber as a private venture in April 1936, DLH evincing only a vague interest in the project, but by the beginning of 1937, this interest had hardened, despite the fact that the only alternative engine to the Jumo 211 or DB 600 was the BMW 132 radial with which the Ju 90 transport would obviously be somewhat underpowered. Thus, by the time the Ju 90 V1 made its initial flight on August 28, 1937, the redesign of the transport by one of Ernst Zindel's principal assistants, Dipl.-Ing. Kraft, had already begun, the project being referred to as the Ju 90S, the suffix letter indicating Schwer (heavy).

In the meantime, work had begun at Dessau on the three additional prototypes and a batch of 10 Ju-90B-1 38-40 passenger transports powered by BMW 132H nine-cylinder radial air-cooled engines each rated at 880 hp for takeoff and possessing a maximum continuous rating of 830 hp. The Ju 90 V2 Preussen and V3 Bayern were completed early in 1938, and during the following summer some attempt was made to gain favorable publicity for the new transport, two load-to-altitude records (11,023 lb to 30,551 ft and 22,046 lb to 23,769 ft) receiving much acclaim during June, it being inferred that the records had been established by the Ju 90 V1. In fact, the Ju 90 V1 had broken up in flight while undergoing flutter tests in February 6, 1938, and the records had been established by the Ju 898 V1 bomber prototype. The Ju 90 V3 was demonstrated publicly at Tempelhof on July 19, 1938, and the Ju 90 V2 came to grief at Bathurst five months later while on loan to DLH for tropical trials. Nevertheless, DLH confirmed its order for eight Ju 90B-1 transports, and South African Airways took on the remaining two aircraft of the initial production batch which, with Pratt & Whitney SC3-G twin Wasp engines, were to be designated as Ju 90Z-2s.

Production deliveries of the Ju 90B-1 to DLH began late in 1938, by which time the first services had already been operated over the Berlin-Vienna route with the Ju 90 V3. The B-series prototype was the Ju 90 V4 Sachsen. The 10 production aircraft were allocated Werk-Nummern 900001 to 0010 inclusive but were also allocated Versuchs-numbers, the first production Ju 90B-1 Württemberg (Werk-Nr. 90 0001 D-ABDG) being, for example, also the Ju 90 V5, while the two Ju 90Z-2s (Werk-Nummern 90 0004 and 0005) were also the Ju 90 V8 and V9, respectively. Incidentally, the two Ju 90Z-2s, which were to have been registered ZS-ANG and -ANH in SAA service, were completed in the summer of 1939 but destined never to be delivered to South Africa.

Ju 90V1.

Throughout the latter half of 1937 and the early months of 1938, the redesign of the basic airframe as the Ju 90S had been continuing under Dipl.-Ing. Kraft on the assumption that the new BMW 139 14-cylinder radial air-cooled engine would eventually be available for installation in the transport, and the Ju 90 V5 (Werk-Nr. 0001 D-ABDG) Württemberg was allocated to test program. The Ju 90 V4 was rebuilt early in 1939 with an entirely new wing which the marked leading-edge sweepback gave place to a straight center section with tapered outer panels. Simultaneously, enlarged and redesigned endplate vertical tail surfaces were applied to ensure adequate stability around the yawing axis with the larger, more powerful engines that it was proposed to eventually install, and sturdier twin-wheel main undercarriage members were provided to cater for the increased operating weights.

A further change was the introduction of the newly-developed Trapoklappe, an hydraulically-powered ventral loading ramp which, when fully lowered, raised the tail of the aircraft from the ground, providing a level freight deck and enabling vehicles to be driven beneath the fuselage so that they could be unloaded directly on the ramp. Field vehicles up to the size of a Kübel-wagen could be driven up the ramp which could also be lowered in flight for paratroops.

When, late in 1939, three design offices were available to Junkers in Prague, it was decided to transfer the entire Ju 90S design program to Prague from Dessau, Dipl.-Ing. Kraft being simultaneously appointed chief designer of the entire Ju 90S development, the former Letov factory at Letňany being responsible for design, mock-up construction and the static and dynamic testing of components, the Dessau plant retaining responsibility for prototype construction and assembly, and test flying, and Junker's Bernburg plant being allocated the responsibility for future series production.

Shortly after hostilities commenced, the Luftwaffe took over few Ju 90B-1s that had been delivered to DLH, together with those awaiting delivered at Dessau, and only two of these were destined to be returned to the airline (D-AEDS Preussen and D-ADLH Sachsen), the remainder being retained by the Luftwaffe for transport tasks or returned to Dessau for modification and subsequent participation in the Ju 290 (as the Ju 90S had now been redesignated) development program. During 1940, the Ju 90 V4 had been re-engined, the low-powered BMW 132H nine-cylinder radials having given place to the 14-cylinder BMW 801MA. The BMW 139 had meanwhile been abandoned in favor of this heavier but more powerful engine which was retrospectively added to the V5 later used at Letňany for trials with blown flaps. These trials proved unsuccessful, and at the suggestion of Prof. Hertel, who had joined Junkers in May 1939 as Technical Director and Chief of Development, the ailerons and flaps were redesigned.

The Ju 90 V7 embodied yet a further modification, an additional fuselage section some 6 ft 6 in in length immediately aft of the rear spar attachment point, overall length being increased from 86 ft 11 1/4 in to 94 ft 2 in. The lengthened aft fuselage eradicated a yawing problem, restoring the cg position which had shifted with the installation of the more powerful engines despite the aft movement of the inboard engines that had resulted from the use of straight wing center section. By this time, the Ju 290 was envisaged as both transport and a maritime reconnaissance aircraft, and the next prototype, the Ju 90 V8 (formerly the first Ju 90Z-2 Werk-Nr. 90 0004 initially flown as D-AQJA) was completed with full defensive armament. The Ju 90 V8 (DJ + YE) embodied the lengthened fuselage of the V7 and introduced a small gondola beneath the port side of the fuselage nose. This housed a forward-firing 20-mm MG 151 cannon and an aft-firing 13-mm MG 131 machine gun. A forward hydraulically-operated dorsal turret mounted a 20-mm MG 151 cannon , and a third 20-mm MG 151 was installed in the extreme tail where a prone position was provided for the gunner. Provision was also made for two MG 131 machine guns firing from lateral mountings in the fuselage sides.

Preparations for the series production of the Ju 290A had begun at Bernburg early in 1942, but still further changes were to be embodied in the wing before it was to reach its definitive form, and the Ju 90 V11 alias Ju 290 V1 (originally Ju 90B-1) had wingspan and area increased from 118 ft 1 1/3 in to 137 ft 9 1/2 in and 1,980.5 to 2,191.53 ft2, respectively. Further, the circular windows, and the oval endplate fins and rudders that had characterized all Ju 90s participating in the Ju 290 development program were replaced by more angular surfaces. lacking defensive armament but retaining the offset gondola beneath the nose, the Ju 290 V1 (BD + TX) commenced flight testing in August 1942.

Ju 290A series

The first pre-production Ju 290A-0 (wek-Nr. 0150) was completed at Bernburg in October 1942 with BMW 801L engines each rated at 1,600 hp for takeoff  and 1,380 hp at 15,100 ft, this, like a second Ju 290A-0 and five Ju 290A-1s (Werk-Nummern 0152-0156), being completed as a transport and possessing essentially similar defensive-armament to that of the Ju 90 V8. This was later to be supplemented by forward maintenance units which introduced a pair of 7.9-mm MG 15 machine guns firing from windows on each side of the forward fuselage.

The Luftwaffe's dire need of large-capacity transport aircraft necessitated the Ju 290As being taken over the Luftwaffe straight from the assembly line, and one of the Ju 290A-0s, together with the Ju 290 V1, was assigned immediately to supply missions for the beleaguered German 6th Army at Stalingrad. The first flight to and from an airfield in the vicinity of the Russian city was made on January 10, 1943. Three days later, the Ju 290 V1 crashed while taking-off with a load of wounded troops being evacuated to Germany, and the Ju 290A-0 was attacked by LaGG-3 fighters during its landing approach after its first flight from Germany. It was so badly damaged that it was unable to effect a lading and had to return to its base.

Ju 290 equipped with radar antennas (Reichlin).

Meanwhile, on January 2, the so-called viermotorige-Transportstaffel had been formed at Tempelhof under the command of Hauptmann Braun, this unit being redesignated LTS 290 shortly after its establishment, indicating that its primary equipment was intended to be the Ju 290. However, at the time of its formation it possessed only two Ju 290As, four Ju 90Bs, the Ju 90 V4, V7 and V8, the Ju 252 V5 and one Fw 200B. LTS 290 was intended primarily for operations in the Balkans and Mediterranean, but was initially under the direct command of the Lufttransport-Chef in Berlin, undertaking long-range missions for the Oberbefehls-haber der Luftwaffe until March 1943 when it was transferred to Grosseto to operate under the Lufttransport-Führer Mittelmeer to supply bases in Tunisia, Sardinia and Corsica. Both Ju 290As had been lost to enemy action by the end of April and no longer possessing any transports of this type, priority having been given to the production of the Ju 290 for the maritime reconnaissance role, the LTS 290 was redesignated Trs.Fl.St.5 (Transport-Fliegerstaffel 5).

The decision to adapt the Ju 290 for the maritime role had resulted from a demand from the Fliegerführer Atlantik for an aircraft with adequate endurance to reconnoiter far out over the Atlantic to accurately plot Allied convoys, and assemble and marshal U-boat packs for favorable interception. The Fw 200C Condor was providing too vulnerable in this role with the steady improvement in the defensive capabilities of Allied convoys, and the first maritime reconnaissance model of the Junkers aircraft, the Ju 290A-2, was a straightforward adaption of the Ju 290A-1 transport, apart from an increase in navigational equipment, the only concessions to its new role being the provision of a second HDL 151 dorsal turret mounting a 20-mm MG 151 cannon, and large-capacity auxiliary tanks in the fuselage. Even the Trapoklappe was retained so that the aircraft could revert to the transport role as the military situation dictated.

The first maritime reconnaissance Ju 290A-2, powered by BMW 801L engines and carrying FuG 200 Hohentwiel search radar, was completed in the summer of 1943, this aircraft going to the Erprobungsstelle Rechlin, and two similar aircraft (Werk-Nummer 0158 and 0159) being delivered to the Fernaufklärungsgruppe 5 (FAGr 5), a two-Staffel unit formed on July 1, 1943 specifically to operate the Ju 290. The three Ju 290A-2s were followed off the Bernburg assembly line by three Ju 290A-3s (Werk-Nummern 0160-0162) which differed solely in having a low-drag aft dorsal turret of Focke-Wulf design, and a slightly modified tail gun position incorporating a raised glazed blister for the gunner's head, and two further Ju 290A-3s (Werk-Nummern 0163 and 0164) which standardized on the BMW 801D in place of the BMW 801L, the new engine offering 1,700 hp for takeoff and 1,450 hp at 6,560 ft.

The five Ju 290A-4s that followed the similar quantity of Ju 290A-3s differed solely in having both fore and aft dorsal turrets of flattened Focke-Wulf low-drag type, each mounting a 20-mm MG 151 cannon. By this time, however, operations by FAGr 5 had resulted in recommendations for heavier defensive armament, increased protection for the pilot and co-pilot, and facilities for fuel dumping in an emergency, and these recommendations were embodied in the next variant to appear on the Bernburg assembly line late in 1943, the Ju 290A-5.

With a loaded weight of 90,323 lb and powered by BMW 801D engines, the Ju 290A-5 introduced improved protection for the fuel tanks - earlier models had tended to ignite fairly easily when hit during combat - and both pilot and co-pilot were provided with heavy-gauge armour aft and to the sides, this armour being capable of withstanding direct hits from 20-mm shells. The aft lateral gun positions were aerodynamically improved, each mounting a 20-mm MG 151 cannon in place of the 13-mm MG 131 machine gun, and embodying spoilers which deflected the airstream when the cannon were swung into firing position. At the same time the crew complement was increased from seven to nine.

Production of the Ju 290A-7 began during the early summer of 1944, and a series of 25 reconnaissance-bombers of this type was laid down, but only a small number of these had been completed when the Bernburg assembly line came to standstill, and the Ju 290A-7 failed to attain service status. One example of the Ju 290A-7 was later flown by its crew to the USA for evaluation.

Prior to the commencement of Ju 290A-7 series production, the Bernburg factory completed three Ju 290A-9s and one Ju 290A-6. The Ju 290A-9 was a maritime reconnaissance aircraft for extended-range missions, featuring increased internal fuel tankage (providing a maximum range of 5,160 miles) and substantially reduced armament. This was restricted to a single forward-firing 20-mm MG 151 cannon in the gondola, a single forward-mounted hydraulically-operated dorsal turret mounting a similar weapon, and a third MG 151 in the extreme tail. Maximum loaded weight was 99,030 lb, and maximum speed was 282 mph. The sole Ju 290A-6 was initially conceived as a pressurized personnel transport for Hitler's personnel flight. Some pressurization trials were conducted at Prague but this scheme was abandoned at an early stage, and the aircraft was completed as an unpressurized 50-passenger transport. This aircraft was eventually taken on the strength of I/KG 200 at Finterswalde for special transport operations and, in the last week of April 1945, was flown to Barcelona by Hauptmann Braun, the original Staffelkapitän of LTS 290 who subsequently served with FAGr 5 and, with the disbandment of that Gruppe, joined Kampfgeschwader 200.

The I/KG 200 was largely responsible for the transportation of escaping nazi leaders, and the identity of the passengers ferried to Barcelona aboard the Ju 290A-6 is open to conjecture. However, the aircraft remained in Spain, eventually to be purchased by the Spanish government in May 1959 from an Allied Commission responsible for the disposal of former enemy assets. After overhaul at Léon and the replacement of the decayed Buna fuel tanks by metal tanks, the Ju 290A-6 served with the Escuela Superior del Vuelo at Salamanca/Matácan, being used during exercises in co-operation with naval forces and as personnel transport until, in the mid 'fifties, it suffered a minor accident and, as spares were no longer available, was scrapped.

Manufacture of yet another version of the A-series was begun at Bernburg in parallel with the Ju 2909A-7 late in 1944, this being the Ju 290A-8. The Ju 290A-8, which possessed a loaded weight of 99,210 lb and a maximum speed of 271 mph, differed from the A-7 in relatively minor respects, these comprising a reduction in fuel capacity, the introduction of two additional hydraulically-operated dorsal turrets, and the provision of a new tail position. this new position housed the gunner in a seated attitude for the first time, was armored and mounted a pair of vertically disposed 20-mm MG cannon. Total defensive armament of the Ju 290A-8 thus comprised four hydraulically-operated turrets each mounting a single MG 151 cannon, single forward-firing MG 151 cannon in the glazed nose and the nose of offset gondola, two MG 151s in lateral positions, and aft-firing MG 131 in the tail of the gondola and a pair of MG 151s in the extreme tail.

 A pre-production series of 10 Ju 290A-8s (Werk-Nummern 0211-0220) was laid down at Bernburg, and the production model was intended to commence with Wek-Nr. 0221, but only two or three of the pre-production machines were completed, and after the liberation of Ruzýnĕ airfield, near Prague, the second pre-production Ju 290A-8 (Werk-Nr. 0212) was discovered partly disassembled, together with major assemblies for a Ju 290B-2. The components were transported to the Letov factory, suitable engines and instruments were unearthed in former-Luftwaffe depots, and assembly and modification of the Ju 290A-8 as a transport was begun. As no Ju 290 propellers were found with the engines, it was decided to employ propellers intended for Fw 190A fighters which, although of smaller diameter, were considered suitable. With the offset gondola and all armament removed, and the nose and tail gun positions faired over, the aircraft was offered to Czechoslovak Airlines as a 48-passenfer transport, but little interest was evinced in the aircraft which was left to languish at Letňany, near Prague, and although an Israeli buyer presented himself in 1947, various complications prevented the sale of the machine which was finally scraped in 1956.

Ju 290B series

Late in 1943, work began on the prototype of a further development of the basic design, the Ju 290B-1 which, dispensing with the Trapoklappe for the first time, was intended specifically for the role of long-range high-altitude heavy bomber. intended to carry all offensive loads externally, the Ju 290B-1 embodied considerable structural strengthening and featured pressurized, Borsig-designed nose and tail turrets each mounting four 13-mm MG 131 machine guns; two pressurized dorsal turrets each with two 20-mm MG 151 cannon, and a remotely controlled ventral barbette also with twin MG 151s. A shallow sighting station for this barbette took the place of the offset gondola of A-series aircraft. The flight deck was intended to be pressurized, tests with the pressure cabin being conducted at Prague; a crew of eight was carried, and proposed offensive armament was similar to that of the Ju 290A-7. The prototype Ju 290B-1 was flown in the summer of 1944 without pressurization equipment and with wooden nose and tail turret mock-ups, eventually being flown to Prague (where it was still flying in March 1945) as development aircraft for later Ju 290 series aircraft).

Before the prototype of the Ju 290B-1 was completed, production plans for this model had been abandoned in favor of the the Ju 290B-2. this dispensed with the turret and flight deck pressurization, reintroduced MG 151 beam guns, and replaced the MG 131V tail turret with a tail position similar to that of the Ju 290A-8 and mounting twin MG 151s. Although production of a pre-series of Ju 290B-2 bombers was commenced at Bernburg, the general situation had deteriorated so much by the autumn of 1944, and supplies of strategic materials had become so critical that all production of the Ju 290 was stopped.

This decision resulted in the abandoning of several other variants of the basic design, including the Ju 290B MS with mine degaussing ring and defensive armament restricted to the tail gun position; the Ju 290C long-range reconnaissance aircraft and transport, and the Ju 290D and E bombers. The Ju 290C was, like the Ju 290B-2, to have been powered by BMW 801E engines, but was to have featured a redesigned loading ramp which could incorporate a mounting for twin MG 151 cannon. The Ju 290D was to have been essentially similar to the Ju 290C, apart from having a fuselage fuel tank removed to provide space for Hs 293 missile control equipment, and the Ju 290E was to have employed considerable structural redesign to permit the insertion of internal bomb-bays capable of accommodating four 5,512 lb bombs or up to 40 551-lb bombs. It was proposed that the initial model of the Ju 290E would be powered by BMW 801E engines but that the definitive production model would supplant these with Jumo 222A-3/B-3 powerplants with which maximum gross weight would have been no less than 133,380 lb.

Ju 290 after the war.

 

Click to enlarge  

 

The Ju 90 V7, seen below in flight with "Trapoklappe" fully extended, was formely the Ju 90B-1 D-ADFJ "Baden".  A lengthened rear fuselage erradicated a yawing problem after the instalation of more powerful engines.

 

Ju 90 Wek-Nummer 009


Data (Ju 290B-2)

Type

Long-range heavy bomber

Powerplant

4 x BMW 801E 14-cylinder radial air-cooled engines each rated @ 1,970 hp for takeoff

Max. speed

276 mph @ 18,045 ft

Range

3,480 miles (loaded with two Hs 293 missiles and 4,000 Imp. gal. fuel)

Max. range

4,970 miles

Service ceiling

24,600 ft

Max. loaded weight

113,330 lb

Span

137 ft 9 1/2 in

Length

96 ft 1 1/2 in

Height

22 ft 4 3/4 in

Wing area

2,191.53 ft2

 

Top

Home

Please note that all information is provided without any guarantees