keskiviikko 8. heinäkuuta 2015

Focke-Wulf Fw 187 Falke

The Focke-Wulf Fw 187 Falke ("falcon") was a German aircraft developed in the late 1930s. It was conceived by Kurt Tank as a twin-engine, high-performance fighter, but the Luftwaffe saw no role for the design, perceiving it as intermediate between the Messerschmitt Bf 109 and Bf 110. Later prototypes were adapted to two-seats to compete with the Bf 110 in the Zerstörer (heavy fighter) role, but only nine aircraft were built in total.
In the early to mid-1930s, developments in airframe design outstripped available aircraft engine power, allowing large aircraft to be built that existing engines were unable to sufficiently lift or propel (at least not alone). A period ensued in which multi-engine designs mostly outperformed aircraft designed with just one engine. In air racing in Europe, the Dornier Do 17 outran every single-engine fighter it competed against. In Germany, this led to the idea of the "schnellbomber", fast bombers that were expected to fly right past the defensive fighters. Although this period of twin-engine superiority would be short-lived, it also led to many air forces considering twin-engine fighter designs, resulting in the Lockheed P-38 Lightning, Westland Whirlwind, Grumman XF5F Skyrocket, and the Fw 187.
In 1935, Kurt Tank made the suggestion of creating a long-range single-seat fighter under a private venture within Focke-Wulf. The idea was not to produce a heavy fighter or bomber destroyer like the Bf 110, but instead a long-range design that would have the performance of a single-seat design. Powered by the new 736 kW (1,000 PS) Daimler-Benz DB 600, it had an expected speed of 560 km/h (350 mph). 

The design was unveiled in 1936 at an exhibition of new weapons, prototypes and projects held at the Henschel factory at Berlin-Schönefeld, where it was viewed by a number of high-ranking Nazi officials, including Hitler. However, the Reich Air Ministry (RLM) rejected the design on the grounds that the single-engine Bf 109 had comparable performance but would cost roughly half as much. The need for a long-range design was not considered serious, as at the time it was believed bomber escort was simply not needed.
Tank then took the design directly to Wolfram von Richthofen, chief of the development section of the Technischen Amt, the research and development arm of the RLM. Richthofen was not so convinced that bomber performance would remain superior to fighters, and gave the go-ahead for the construction of three prototypes, but on the condition that they replace the DB 600, which was in extremely short supply, with the less-powerful 515 kW (700 PS) Junkers Jumo 210.

R. Blaser was assigned to detail design. In order to improve performance compared to the Bf 110, the fuselage was made as small as possible, so small that there was no room on the instrument panel for the complete set of engine instruments, which were instead moved to the inside faces of the engine nacelles, as would be done for the Hs 129 ground attack aircraft and some versions of the Bf 110. The engine nacelles were relatively normal, including both the engine and the main landing gear storage, but the front-mounted radiators for the engines were retractable for high speed when less frontal area would be needed to get the same airflow. 

The mainwheels were fully retractable and faired and the design required no struts or supports, in order to further reduce drag. The wing's two spars passed under the pilot's seat. As was common on pre-war designs, the rear of the fuselage was raised which blocked direct viewing to the rear, but the aircraft nevertheless used a bubble-type canopy, opening rearward and upward at an angle of about 15°. Although the cockpit was located well forward, a small window panel was fitted in the underside of the nose by the pilot's feet to improve the view for landing.
The first prototype, Fw 187 V1 (D-AANA) flew for the first time in late spring 1937, with Hans Sander at its controls. In testing it demonstrated 523 km/h (325 mph) despite the use of the low-powered Jumo engines. In fact, it was 80 km/h (50 mph) faster than the contemporary Jumo-powered Messerschmitt Bf 109B, despite having twice the range, more than twice the weight, and using two of the same engines. Members of the RLM complained that this was due to faulty flight instruments, but further testing ruled this out. The Fw 187's climb and dive rates were also on par - if not superior - to the single-seater.

Several changes were made to the design as a result of the testing, including new DVL propellers in place of the original Junkers-Hamiltons, and experimental twin-wheel bogies that were abandoned after testing. Blaser was concerned about flutter in the rudder at high speed and had fit a weight to reduce it, but in testing this proved to cause flutter and was torn away at high speed. A second prototype followed, differing in having fixed radiators in place of the retractable versions, a semi-retractable tailwheel, changes to the elevator, and a vertical stabilizer with somewhat less chord. 
The engine was also upgraded to the 210G version of the Jumo, which featured direct fuel injection and a fairly dramatic boost in power as a result. New ejector exhaust stacks were fitted for a small boost in speed. Fw 187 V2 started testing in the summer of 1937, but crashed on landing when one of its landing gear legs failed, and V1 was destroyed on 14 May 1938 after a high-speed pass over the Bremen facilities, when the pilot, Paul Bauer, pulled up too sharply at the end of the pass, stalling the aircraft and spinning into the ground.

Ernst Udet had replaced von Richthofen in 1936, and although he was a major proponent of high-speed monoplane fighters, he also demanded maneuverability and was unconvinced that a twin-engine design could ever stand up in this regard. Nevertheless, he felt the performance of the aircraft warranted its development as a potential replacement for the Bf 110 in the bomber destroyer role. Even before V1 flew, Tank had been instructed to convert the design to a two-seater for this role, although the need for a second crewmember in this role was marginal. The first two prototypes were already well advanced in construction at this point, so they began with the third prototype, which had just begun construction.
Blaser adapted the design by stretching the fuselage only slightly, but this did have the effect of moving the center of gravity, which demanded the engine nacelles be modified to return the balance to the proper point in relation to the wing. A new extended-length cockpit with two crew members covered by a "framed" canopy was added, but due to the high line of the fuselage there was nowhere to put any defensive armament, reducing the second crewmember to the role of radio operator only. The offensive armament was improved by replacing two of the 7.92 mm (.312 in) MG 17 machine guns with 20 mm MG FF cannons, although these were never actually fitted.

Fw 187 V3 (D-ORHP) flew in spring 1938, but it suffered a starboard engine fire during one of the initial test flights, and damaged both landing gear during the forced landing that followed. It was quickly repaired and returned to service. Two additional two-seat prototypes, V4 (D-OSNP) and V5 (D-OTGN), followed in the summer and autumn of 1938 respectively. Also powered by the Jumo 210, they proved to have less performance than expected, and did not warrant replacing the Bf 110.

The final prototype, Fw 187 V6 (D-CINY), was more heavily modified. It received the originally specified 736 kW (1,000 PS) DB 600 engines, as well as a new surface evaporative cooling system for reduced drag. It was first flown in early 1939, and proved to have serious cooling problems (in common with other designs using the system, like the Heinkel He 100) and suffered some skin buckling and distortion. Nevertheless, during a series of carefully timed and measured runs in October 1939, the Fw 187 V6 clocked 634 km/h (395 mph) in level flight, making it the fastest fighter in Germany at the time.
A small production run of three Fw 187 A-0 followed in the summer of 1939, based upon the V3 prototype and using the Jumo 210G engines. The Luftwaffe, however, stated that without defensive armament the aircraft could not fit the Zerstörer role, and remained uninterested in the design. The three two-seat prototypes were returned to Focke-Wulf after testing at Rechlin. There was a brief study in the winter of 1942/43 as a night fighter, but the lack of room in the cockpit for the radar equipment quickly eliminated it from contention. After rejecting the design, the RLM "recycled" their 8-187 airframe number to Junkers for their Junkers Ju 187 dive bomber prototype.

Tank nevertheless directed studies on a wide variety of new versions of the basic airframe, everything from dive bomber, night fighter, fighter-bomber, high-altitude interceptor (with greater wingspan and lengthened rear fuselage) and others. These sported a variety of engines, including the Daimler-Benz DB 601, DB 605 and even the BMW 801 radial. The Ta 154 Moskito resulted from the Luftwaffe requirement for a twin-engine heavy fighter like the Fw 187, but constructed from wood instead of light alloys. Due to the different material, Kurt Tank couldn't make any use of the work done for the Fw 187 but had to design a completely new aircraft to meet this requirement. The surviving Fw 187s were apparently used as testbeds during this program.

An Industrie-Schutzstaffel = (Industry-Defense Squadron) comprising the three Fw 187 A-0s was manned by Focke-Wulf test-pilots in defense of the factory in Bremen. Although there are claims that they scored several kills, it is likely that these were propaganda claims. The three A-0s were even sent to Norway and promoted as evidence that the aircraft was entering service to replace the Bf 110, but by this time any such plan was long dead. The pilots reportedly found the Fw 187 generally superior to the Bf 110 in almost all respects, but the RLM quickly withdrew them from service. They returned to Focke-Wulf, where they were again used for plant defense. One Fw 187 was sent to the aerial gunnery school in Værløse, Denmark in 1942.
Specifications Fw 187 A-0
Crew: 2
Length: 11.12 m 
Wingspan: 15.30 m 
Height: 3.85 m 
Wing area: 30.40 m² 
Empty weight: 3,700 kg 
Loaded weight: 5,000 kg 
Powerplant: 2 × Junkers Jumo 210G 12-cylinder inverted-V piston, 515 kW (700 PS) 
Maximum speed: 529 km/h at 4,200 m 
Service ceiling: 10,000 m 
Rate of climb: 1,050 m/min 
Wing loading: 164.14 kg/m² 
Armament: 4 × 7.92 mm MG 17 mg in fuselage sides
Guns: 2 × 20 mm MG FF cannon in lower fuselage

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