Genesis Between 1934 and 1935, the
German Ministry of Aviation (RLM) ran a contest to produce a modern fighter for the rearming Luftwaffe. Kurt Tank entered the parasol-winged
Fw 159 into the contest, against the
Arado Ar 80,
Heinkel He 112 and Messerschmitt Bf 109. The Fw 159 was hopelessly outclassed and was soon eliminated from the competition along with the Ar 80. The He 112 and Bf 109 were generally similar in design, but the 109's lightweight construction gave it a performance edge the 112 was never able to match. On March 12, 1936, the 109 was declared the winner. Even before the Bf 109 had entered squadron service, in autumn 1937, the RLM sent out a new tender asking various designers for a new fighter to fight alongside the Bf 109, as
Walter Günther had done with Heinkel's follow-on to the unsuccessful
He 100 and He 112. Although the Bf 109 was an extremely competitive fighter, the ministry was worried that future foreign designs might outclass it, and wanted to have new aircraft under development to meet these possible challenges. Tank responded with a number of designs, most powered by a liquid-cooled, inline engine. The Ministry of Aviation's interest was not aroused, though, until a design was presented using the air-cooled, 14-cylinder
BMW 139 radial engine. As this design used a radial engine, it did not compete with the inline-powered Bf 109 for engines, when already too few
Daimler-Benz DB 601s were available. This was not the case for competing designs such as the
Heinkel He 100 or twin-engined
Focke-Wulf Fw 187, where production would compete with the 109 and
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.
Design concepts At the time, the use of radial engines in land-based fighters was relatively rare in Europe, as their large frontal area were believed to 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. As to the rest of the design philosophy, Tank wanted something more than an aircraft built only for speed. He outlined the reasoning:
Engine The hottest points on any air-cooled engine are the cylinder heads, located around the circumference of a radial engine. To provide sufficient air to cool the engine, airflow had to be maximized at this outer edge. This was normally accomplished by leaving the majority of the front face of the engine open to the air, causing considerable
drag. During the late 1920s,
NACA led the 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 an 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 gap in the front of the cowl and was directed through ductwork in the cowl, so it was blowing rearward along the cylinder heads. The propeller spinner helped 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. The eventual choice of the BMW 801 14-cylinder radial over the more troublesome BMW 139 also brought with it a BMW-designed cowling "system" which integrated the radiator used to cool the motor oil. An annular, ring-shaped oil cooler core was built into the BMW-provided forward cowl, just behind the fan. The outer portion of the oil cooler's core was in contact with the main cowling's sheet metal. Comprising the BMW-designed forward cowl, in front of the oil cooler was a ring of metal with a C-shaped cross-section, with the outer lip lying just outside the rim of the cowl, and the inner side on the inside of the oil cooler core. Together, the metal ring and cowling formed an S-shaped duct with the oil cooler's core contained between them. Airflow past the gap between the cowl and outer lip of the metal ring produced a vacuum effect that pulled air from the front of the engine forward across the oil cooler core to provide cooling for the 801's motor oil. The rate of cooling airflow over the core could be controlled by moving the metal ring to open or close the gap. The reasons for this complex system were threefold. One was to reduce any extra aerodynamic drag of the oil radiator, in this case largely eliminating it by placing it within the same cowling as the engine. The second was to warm the air before it flowed to the radiator to aid in warming the oil during starting. Finally, by placing the radiator behind the fan, cooling was provided even while the aircraft was parked. The disadvantage to this design was that the radiator was in an extremely vulnerable location, and the metal ring was increasingly armoured as the war progressed.
Landing gear In contrast to the complex, failure-prone, fuselage-mounted, main gear legs of the earlier Fw 159, one of the main features of the Fw 190 was its wide-tracked, inwards-retracting, landing gear. They were designed to withstand a sink rate of , double the strength factor usually required. Hydraulic wheel brakes were used. The wide-track undercarriage produced better ground handling characteristics, and the Fw 190 suffered fewer ground accidents than the Bf 109. (The Bf 109's narrow-track, outwards-retracting landing gear hinged on its wing root structure to help lower weight, but this led to inherent weakness and many failures and ground loops.) The Fw 190's retractable tail gear used a cable, anchored to the "elbow" at the midpoint of the starboard maingear's transverse retraction arms, which ran aftwards within the fuselage to the vertical fin to operate the tailwheel retraction function. The tailwheel's retraction mechanical design possessed a set of pulleys to guide the aforementioned cable to the top of the tailwheel's
oleo strut, pulling it upwards along a diagonal track within the fin, into the lower fuselage; this mechanism was accessible through a prominently visible triangular-shaped hinged panel, on the left side in the fin's side sheetmetal covering. On some versions of the Fw 190 an extended tailwheel oleo strut could be fitted for larger-sized loads (such as bombs or even a torpedo) beneath the fuselage.
Control systems 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. Another innovation was making the controls as light as possible. The maximum resistance of the ailerons was limited to , 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.
Wing loading and canopy Like the Bf 109, the Fw 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 under most flight conditions, so flies faster and may have better range, but it also means the aircraft has a higher
stalling speed, making it less maneuverable, and also reduces performance in the thinner air at higher altitudes. The wings spanned and had an area of . The wing was designed using the NACA 23015.3 airfoil at the root and the NACA 23009 airfoil at the tip. Earlier aircraft designs generally featured canopies consisting of small plates of
perspex (also known as Plexiglas) in a metal "greenhouse" framework, with the top of the canopy even with the rear fuselage; this was true of the
IJNAS Mitsubishi A6M Zero, whose otherwise "all-around view" canopy was still heavily framed. 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 visibility. Tank's design for the Fw 190 used a canopy with a frame that ran around the perimeter, with only a short, centerline seam along the top, running rearward from the radio antenna fitting where the three-panel windscreen and the forward edge of the canopy met, just in front of the pilot.
Wilde Sau From mid-1943, Fw 190s were also used as night fighters against the growing
RAF Bomber Command offensive. In mid-1943, one of the earliest participants in the single-engined, ground controlled, night-fighting experiments was the
Nachtjagdkommando Fw 190 (Night Fighter Command Fw 190), operated by IV.
Gruppe (4 Group),
Jagdgeschwader 3, (Fighter Wing 3, or JG 3). The main
Nachtgeschwader (Night Fighter Wings) were keen to adopt a new fighter type as their twin-engine fighters were too slow for combat against increasing numbers of
de Havilland Mosquito night fighters and bombers.
Nachtjagdgeschwader 1 (NJG 1) and
NJG 3 kept a pair of Fw 190s on standby to supplement the Messerschmitt Bf 110 and
Junkers Ju 88. The considerable performance advantage of the Fw 190 over the other two types was more than offset by the difficulties of operating at night. Few, if any, aerial successes can be attributed to these operational tests. One of the first purpose-built units to use Fw 190s in this role was
Stab/Versuchskommando Herrmann, a unit specifically set up in April 1943 by Major
Hajo Herrmann. Herrmann's unit used standard A-4s and A-5s borrowed from day fighter units to intercept bombers over or near the targeted city, using searchlights and other visual aids to help them find their quarry. The first use of
"Window" by the RAF during the
Battle of Hamburg in July 1943, rendered the standard nightfighter
Himmelbett procedures useless and brought urgency to the development of Herrmann's
Wilde Sau ("Wild Boar") technique, pending the development of new nightfighting strategies. Instead of restricting the Fw 190s to ground control interception protocols, the Fw 190s were given a free hand to over-fly bombed areas to see if they could locate bombers using the ground fires below. These tactics became an integral part of the nightfighter operations until May 1944. St/V Herrmann was expanded to become
Jagdgeschwader 300 (JG 300, or Fighter Wing 300),
JG 301 and JG 302. All three units initially continued borrowing their aircraft from day fighter units. The day fighter units began to protest at the numbers of their aircraft that were being written off because of the hazards of night operations; the numbers soared with the onset of winter, with pilots often being forced to bail out through being unable to find an airfield at which to land safely. Crash landings were also frequent. Eventually, all three
Wilde Sau units received their own aircraft, which were often modified with exhaust dampers and blind-flying radio equipment. Another unit was
Nachtjagdgruppe 10, which used Fw 190 A-4/R11s through to A-8/R11s; Fw 190s modified to carry FuG (
Funkgerät)
217 or FuG 218 radar mid-VHF band equipment.
The Sturmböcke The appearance of
United States Army Air Forces heavy bombers caused a problem for the German fighter force. The
Boeing B-17 Flying Fortress in particular was especially durable, and the armament of the Bf 109 and Fw 190 were not adequate for bomber-destroyer operations. The B-17's eventual deployment in
combat box formations provided formidable massed firepower from 100 or more
Browning AN/M2 .50 caliber (12.7 mm) machine guns. In addition, the
Luftwaffes original solution of
Zerstörer twin-engined Messerschmitt Bf 110G
bomber destroyers, while effective against unescorted Allied bomber formations, lacked maneuverability and were eviscerated by the USAAF's fighter escorts in late 1943 and early 1944. Two of the former
Wilde Sau single-engined night fighter wings were reconstituted for their use, such as
Jagdgeschwader 300 (JG 300—300th Fighter Wing) and
JG 301. These units consisted of
Sturmböcke. However,
JG 3 also had a special
gruppe (group) of Sturmböcke. The Fw 190, designed as a rugged interceptor capable of withstanding considerable combat damage and delivering a potent "punch" from its stable gun platform, was considered ideal for antibomber operations. Focke-Wulf redesigned parts of the wing structure to accommodate larger armament. The Fw 190 A-6 was the first subvariant to undergo this change. Its standard armament was increased from four
MG 151/20s to two of them with four more in two underwing cannon pods. The aircraft was designated A-6/R1 (
Rüstsatz; or field conversion model). The first aircraft were delivered on 20 November 1943. Brief trials had the twin cannon replaced by the
MK 108 30 mm autocannon in the outer wing, which then became the A-6/R2. The cannons were blowback-operated, had electric ignition, and were belt fed. The 30 mm MK 108 was simple to make, and its construction was economical; most of its components consisted of just pressed sheetmetal stampings. In the A-6/R4, the
GM-1 (
nitrous oxide) boost was added for the BMW 801 engine to increase performance at high altitude. For protection, of armoured glass were added to the canopy. The A-6/R6 was fitted with twin, heavy-calibre
Werfer-Granate 21 (BR 21) unguided, air-to-air rockets, fired from single underwing tubular launchers (one per wing panel). The increased modifications, in particular heavy firepower, made the Fw 190 a potent bomber-killer. The A-7 evolved in November 1943. Two synchronized 13 mm (.51 inch)
MG 131 machine guns replaced the twin, cowl-mount, synchronized 7.92 mm (.318 inch) MG 17 machine guns. The A-7/R variants could carry two 30 mm MK 108s, as well as BR 21 rockets. This increased its potency as a
Pulk-Zerstörer (bomber formation destroyer). The A-8/R2 was the most numerous
Sturmbock aircraft; some 900 were built by Fiesler at
Kassel with 30 mm MK 108s installed in their outer wing panel mounts. While formidable bomber-killers, the armour and substantial up-gunning with heavier-calibre firepower meant the Fw 190 was now cumbersome to maneuver. Vulnerable to Allied fighters, they had to be escorted by Bf 109s. When the
Sturmgruppe was able to work as intended, the effects were devastating. With their engines and cockpits heavily armored, the Fw 190 As attacked from astern and gun camera films show that these attacks were often pressed to within 100 yds (90 m).
Willy Unger of 11.(
Sturm)/JG 3 (11
Staffel (Squadron) of
Sturmgruppe (Storm group) JG 3) made these comments: Richard Franz commented: The number of heavy bombers destroyed by the Fw 190 is impossible to estimate. However, below is a list of the top-scoring
Sturmbock pilots: ==Variants==