Wednesday, February 4, 2015

Focke-Wulf Fw-191


During the winter of 1939-40, the Reichsluftfahrtministerium issued a specification for what was, known as the "B" medium bomber. This bomber had to possess a radius of action covering the whole of the British Isles from French or Norwegian bases, a pressurised crew compartment, remotely controlled defensive armament, the ability to perform the dive-bombing role, a maximum speed of 370 m.p.h., and a bomb load of 8,820 lb.

The specification was issued to several aircraft manufacturers, and four companies received development contracts : Arado for the Ar 340, Junkers for the Ju 288, Dornier for the Do 317, and Focke-Wulf for the Fw 191. During the early months of 1940, the RLM made a final selection from the four competitive designs, abandoning the Ar 340, allocating low development priority to the Do 317, and giving full backing to the development of the Ju 288 and the Fw 191.

The Focke-Wulf design embodied several novel features, and all systems were electrically-operated. In fact, the aircraft employed so many small electric motors that it was quickly dubbed the "Flying Power Station." The design of the Fw 191 was the work of a team led by Dipl. Ing. Kosel, who had previously developed the Fw 186 gyroplane and the Fw 189 army co-operation monoplane, and construction of the first of six prototypes, the Fw 191VI, commenced in the spring of 1940. At the time of the Fw 191 's design, Junkers had promised the availability of the 2,500 h.p. Jumo 222 engine for installation, but continual teething troubles had bogged down the development of this engine, and when the Fw 191V1 made its first flight tests early in 1942, with Dipl. Jng. Melhorn at the controls, power was provided by a pair of.BMW 801A engines rated at 1,600 h.p. for take-off and 1,380 h.p. at 15,100 ft.

The Fw 191V1 followed standard German practice in concentrating its crew of four in the fuselage nose. This compartment was to be pressurised in the production version, and aft of the crew compartment was the bomb bay, which could house a maximum load of 8,820 lb. A further 4,400 lb. of bombs or a pair of LT950 glider torpedoes could be carried underwing, between the fuselage and engine nacelles. Above the bomb bay were the main fuselage fuel tanks, which, together with tanks in the inboard wing sections, were sufficient for a range of 2,200 miles. The fuselage, which was basically of circular section, had an overall length of 64 ft. 4 3/4 in., and carried the 85 ft. 3 1/2in. wing in high-mid position. The exceptionally stalky main under-carriage legs retracted backwards, the large wheels turning through ninety degrees to lie flat in the shallow engine nacelles.

While the Fw 191V1 was, in fact, unarmed, it carried mock-ups of the remotely-controlled turrets that were proposed for the production Fw 191A bomber. A chin turret was to have contained twin 7.9-mm. MG 81 machine guns, the remotely-controlled dorsal and ventral barbettes were to have each contained one 20-mm. MG 151 cannon and two MG 81 machine guns, and two small barbettes placed at. the extremities of the engine nacelles were to have housed two MG 81 machine guns each. The dorsal and engine barbettes were to have been controlled by the radio operator and the ventral barbette by the flight engineer.

The first prototype had made ten flight tests by the time that it was joined by the Fw 191V2, but with an all-up weight of some 50,700 lb., it was seriously underpowered, the numerous small electric motors were a constant source of failure, and the combined landing flap and dive brake, known as the "Multhopp- Klappe," suffered serious flutter problems. In fact, flight tests were so disappointing that, after ten hours of flying, further flight development was abandoned and work on the third, fourth and fifth prototypes cancelled. Dipl. Ing. Kosel had continually complained to the RLM about the foolishness of their insistence that the Fw 191 should employ all-electric systems which were inadequately developed and the source of many of the Fw 191's teething troubles. Finally, permission was given to complete the sixth prototype, the Fw 191V6, with hydraulic systems. The Fw 191V6 was powered by a pair of early Jumo 222 engines, but, at 2,200 h.p., these offered considerably less power than had been anticipated.

The aircraft was flown for the first time in the spring of 1943 by Flugkapitan Sander, but tests results were little improved over those obtained with the first two machines. After limited testing at Delmenhorst, the Fw 191V6 was transferred to Wenzendorf, but this was destined to be its last flight, for, as it was becoming increasingly obvious that the Jumo 222 would never be a reliable engine owing to the lack of high quality materials, and as no suitable alternative engine offered itself, the RLM had decided to cancel the "B" medium bomber programme.

Focke-Wulf had earlier proposed the Fw 191B with Daimler- Benz DB 605L engines, but these only offered 1,700 h.p. for take-off and emergency, and there was little possibility of attaining the original performance requirements. Thus, after the cancellation of the Fw 191A programme, a simplified version of the basic design, the Fw 191 C, was offered. Featuring no pressurisation and abandoning the complex system of remote1y- controlled gun barbettes in favour of manually-operated guns, the Fw 191C was to have been powered by four Jumo 211F, D8 601E or DB 605A engines, but this variant never progressed further than the drawing board.

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