Focke-Wulf Fw 190 TL
In the late 1930s, Max A. Mueller, engineer of the firm Junkers AG, patented a ducted-fan device that greatly improved the performance of the conventional propellers. In 1938, a team of technicians of the company BMW GmbH, under the leadership of Dr.-Ing. Hermann Oestrich, modified a Bramo 325 radial engine fitted with a four-bladed ducted-fan with a diameter of 1 m. The modified engine, that was named
Motorjet, was installed in a trainer Focke-Wulf Fw 44 and successfully tested in flight by Hanna Reitsch.
In 1939, Max A. Mueller joined the Heinkel-Rostock team, working at the time on the development of the HeS 8 centrifugal turbojet, which was expected to be used to propel the He 280 fighters. With a planned thrust of 700 kp and a diameter 20 per cent shorter than the HeS 3, the new turbojet required a great research effort and an extensive test program. Numerous technical problems had to be solved before starting its large-scale production and the HeS 8 suffered numerous delays. By March 1941 it only produced 500 kp static thrust, 550 kp by early 1942 and 600 kp in early 1943.
The root cause was the reduction of the diameter, recommended by the aerodynamicists to minimize the drag produced by the engine nacelles when installed under the wings of the He 280. Trials experience revealed that the most effective way to increase thrust in this type of turbojets was to also increase their diameter, to improve the performance of the centrifugal compressor. In 1939, the HeS 3B, with 93 cm of diameter, produced 450 kp. In May 1941, the British Power Jets W.1, with 107 cm in diameter, produced 387 kp and in 1943, the De Havilland Halford H.1, with 127 cm in diameter, produced 1,225 kp static thrust. With this power, it was possible to build a single engine jet fighter, with the centrifugal turbojet installed inside the fuselage. In 1943, the British chose the Halford to propel their new fighters Gloster E5/42 and De Havilland E6/41 ‘Vampire’. The Americans used the same turbojet to power the Lockheed XP-83 prototype, in early 1944.
In Germany, Max A. Mueller proposed to build the 'ZTL' version of the HeS 8, with a ducted fan of 1 m diameter and a planned thrust of 900 kp. Focke-Wulf engineers also proposed to modify a HeS 8 to be used as a nose-mounted power plant in an Fw 190. The modification would consist of replacing the radial inflow turbine with another of 122 cm diameter and the exhaust nozzle by three outlets located underneath and on both sides of the cowling. The outlets were equipped with deflectors to prevent hot gases from damaging the airframe. The new turbojet, called T.1, would have had a thrust of 600 kp by the end of 1942.
The jet version of the Fw 190 A-3 was named ‘TL’ (Turbo Lader), would have had an overall length of 9.4 m, an estimated maximum weight of 4,865 kg and an estimated maximum speed of 850 kph. The ceiling was expected to be of 10,300 m and the range of 1370 km. Its endurance, with 1,400 litres of J2 heavy kerosene, would have been 70 minutes. As for the armament, would have consisted of two machine guns MG 17 and two MG 151/20 cannons in the standard positions.
In the spring of 1943, the OKL decided to cancel all research work with centrifugal turbojets to focus on the development of axial-flow type engines.