The Focke-Wulf Fw 190 Würger (English: Shrike) was a German single-seat, single-engine fighter aircraft designed by Kurt Tank in the late 1930s and widely used duringWorld War II. Powered by a radial engine in most versions, the Fw 190 had ample power and was able to lift larger loads than its well-known counterpart, the Messerschmitt Bf 109. The Fw 190 was used by the Luftwaffe in a wide variety of roles, including day fighter, fighter-bomber, ground-attack aircraft and, to a lesser degree, night fighter.
When the Fw 190 started flying operationally over France in August 1941, it quickly proved itself to be superior in all but turn radius to the Royal Air Force's main front-line fighter, the Spitfire Mk. V, especially at low and medium altitudes. The 190 maintained superiority over Allied fighters until the introduction of the improved Spitfire Mk. IX in July 1942 restored qualitative parity. The Fw 190 made its air combat debut on the Eastern Front in November/December 1942; though Soviet pilots considered the Bf 109 the greater threat, the Fw 190 made a significant impact. The fighter and its pilots proved just as capable as the Bf 109 in aerial combat, and in the opinion of German pilotswho flew both, provided increased firepower and manoeuvrability at low to medium altitude.
The Fw 190 became the backbone of the Jagdwaffe (Fighter Force), along with the Bf 109. On the Eastern Front, the Fw 190 was versatile enough to use inSchlachtgeschwader (Battle Wings or Strike Wings), specialised ground attack units which achieved much success against Soviet ground forces. As an interceptor, the Fw 190 underwent improvements to make it effective at high altitude, enabling it to maintain relative parity with its Allied opponents. The Fw 190A series' performance decreased at high altitudes (usually 6,000 m (20,000 ft) and above), which reduced its effectiveness as a high-altitude interceptor, but this problem was mostly rectified in later models, particularly in the Junkers Jumo 213 inline-engine Focke-Wulf Fw 190D series, which was introduced in September 1944. In spite of its successes, it never entirely replaced the Bf 109.
The Fw 190 was well liked by its pilots. Some of the Luftwaffe's most successful fighter aces claimed a great many of their kills while flying it, including Otto Kittel, Walter Nowotny and Erich Rudorffer.
In autumn 1937, the German Ministry of Aviation asked various designers for a new fighter to fight alongside the Messerschmitt Bf 109, Germany's front line fighter. Although the Bf 109 was an extremely competitive fighter, the Ministry of Aviation was worried that future foreign designs might outclass it, and wanted to have new aircraft under development to meet these possible challenges.
Kurt Tank responded with a number of designs, most incorporating liquid-cooled inline engines. However, it was not until a design was presented using the air-cooled, 14-cylinder BMW 139 radial engine that the Ministry of Aviation's interest was aroused. As this design used a radial engine, it would not compete with the inline-powered Bf 109 for engines, when there were already too few Daimler-Benz DB 601s to go around. This was not the case for competing advanced designs like the Heinkel He 100 or Focke-Wulf Fw 187, where production would compete with the 109 or Messerschmitt Bf 110 for engine supplies. After the war, Tank denied a rumour that he had to "fight a battle" with the Ministry to convince them of the radial engine's merits.
At the time, the use of radial engines in land-based fighters was relatively rare in Europe, as it was believed that their large frontal area would cause too much drag on something as small as a fighter. Tank was not convinced of this, having witnessed the successful use of radial engines by the U.S. Navy, and felt a properly streamlined installation would eliminate this problem.
The hottest points on any air-cooled engine are the cylinder heads, located along the outside diameter of a radial engine. In order to provide sufficient air to cool the engine, airflow had to be maximized at this outer edge, which was normally accomplished by leaving the majority of the front face of the engine open to the air. During the late 1920s, NACA led development of a dramatic improvement by placing an airfoil-shaped ring around the outside of the cylinder heads (the NACA cowling). The shaping accelerated the air as it entered the front of the cowl, increasing the total airflow, and allowing the opening in front of the engine to be made smaller.
Tank introduced a further refinement to this basic concept. He suggested placing most of the airflow components on the propeller, in the form of a oversized propeller spinner whose outside diameter was the same as the engine. The cowl around the engine proper was greatly simplified, essentially a basic cylinder. Air entered through a small hole at the centre of the propeller, and was directed through ductwork in the spinner so it was blowing rearward along the cylinder heads. To provide enough airflow, a cone was placed in the centre of the hole, over the propeller hub, which was intended to compress the airflow and allow a smaller opening to be used. In theory, the tight-fitting cowling also provided some thrust due to the compression and heating of air as it flowed through the cowling.
As to the rest of the design philosophy, Tank wanted something more than an aircraft built only for speed. Tank outlined the reasoning:
The Messerschmitt 109 [sic] and the British Spitfire, the two fastest fighters in world at the time we began work on the Fw 190, could both be summed up as a very large engine on the front of the smallest possible airframe; in each case armament had been added almost as an afterthought. These designs, both of which admittedly proved successful, could be likened to racehorses: given the right amount of pampering and easy course, they could outrun anything. But the moment the going became tough they were liable to falter. During World War I, I served in the cavalry and in the infantry. I had seen the harsh conditions under which military equipment had to work in wartime. I felt sure that a quite different breed of fighter would also have a place in any future conflict: one that could operate from ill-prepared front-line airfields; one that could be flown and maintained by men who had received only short training; and one that could absorb a reasonable amount of battle damage and still get back. This was the background thinking behind the Focke-Wulf 190; it was not to be a racehorse but a Dienstpferd, a cavalry horse.
One of the main features of the Fw 190 was its wide-tracked, inwards-retracting landing gear, designed to withstand a sink rate of 4.5 meters per second (15 feet per second, 900 feet per minute), double the strength factor usually required. Hydraulic wheel brakes were used. The wide-track landing gear produced better ground handling characteristics, and the Fw 190 suffered fewer ground accidents than the Bf 109 with its narrow-track, outwards-retracting landing gear hinged on its wing root structure. The retractable tail gear used a cable, which was guided over a set of pulleys located in the vertical fin, to pull the oleo strut upwards into the lower fuselage. On some versions of the Fw 190 an extended oleo strut could be fitted for larger-sized loads (such as bombs or even a torpedo) beneath the fuselage.
Most aircraft of the era used cables and pulleys to operate their controls. The cables tended to stretch, resulting in the sensations of "give" and "play" that made the controls less crisp and responsive, and required constant maintenance to correct. For the new design, the team replaced the cables with rigid pushrods and bearings to eliminate this problem.[N 2] Another innovation was making the controls as light as possible. The maximum resistance of the ailerons was limited to 8 lb (3.6 kg) as the average man's wrist could not exert a greater force. The empennage (tail assembly) featured relatively small and well-balanced horizontal and vertical surfaces.
The design team also attempted to minimize changes in the aircraft's trim at varying speeds, thus reducing the pilot's workload. They were so successful in this regard that they found in-flight-adjustable aileron and rudder trim tabs were not necessary. Small, fixed tabs were fitted to control surfaces and adjusted for proper balance during initial test flights. Only the elevator trim needed to be adjusted in flight (a feature common to all aircraft). This was accomplished by tilting the entire horizontal tailplane with an electric motor, with an angle of incidence ranging from -3° to +5°.
Another aspect of the new design was the extensive use of electrically powered equipment instead of the hydraulic systems used by most aircraft manufacturers of the time. On the first two prototypes, the main landing gear was hydraulic. Starting with the third prototype, the undercarriage was operated by push buttons controlling electric motors in the wings, and was kept in position by electric up and down-locks. The armament was also loaded and fired electrically. Tank believed that service use would prove that electrically powered systems were more reliable and more rugged than hydraulics, electric lines being much less prone to damage from enemy fire.
As was the case for the 109, the 190 featured a fairly small wing planform with relatively high wing loading. This presents a trade-off in performance; an aircraft with a smaller wing suffers less drag in most flight and therefore flies faster and may have better range. However, it also means the wing cannot generate extra lift as easily, which is needed for maneuvering or flight at high altitudes. The wings spanned 9.5 m (31 ft 2 in) and had an area of 15 m² (161 ft²). The wing was designed using the NACA 23015.3 airfoil at the root and the NACA 23009 airfoil at the tip.
Earlier designs generally featured canopies consisting of small plates of perspex in a metal framework, and the fuselage running horizontally back from the top of the canopy frame. This design considerably limited visibility, especially to the rear. The introduction of vacuum forming led to the creation of the "bubble canopy" which was largely self-supporting, and could be mounted over the cockpit, offering greatly improved all-round views. Tank's new design included a canopy that used only a single perimeter frame — with only a single short centerline seam frame forward of the radio antenna fitting atop the canopy's highest point — where the three-panel windscreen and forward edge of the canopy met, just in front of the pilot.