Focke Wulf Fw 190

The Focke-Wulf Fw 190 Würger ("shrike"), also called Butcher-bird, was a single-seat, single-engine fighter aircraft of Germany's Luftwaffe. Used extensively during the Second World War, over 20,000 were manufactured, including around 6,000 fighter-bomber models. Production ran from 1941 to the end of hostilities, during which time the aircraft was continually updated. Its later versions retained qualitative parity with Allied fighter planes, but Germany was not able to produce the aircraft in enough numbers to affect the outcome of the war.

Early development
Fw 190 A
Fw 190 A

In autumn 1937, the Reichsluftfahrtministerium (RLM) or Reich Air Ministry asked various designers for a new fighter to fight alongside the Messerschmitt Bf 109, Germany's front line fighter. Although the Bf 109 was at that point an extremely competitive fighter, the RLM was worried that future foreign designs might outclass it and wanted to have new aircraft under development to meet these possible challenges.[3]

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 RLM's interest was aroused. At the time, the use of radial engines was unusual in Europe because of their large frontal area and the belief that they caused too much drag to allow for a competitive design. Tank was not convinced of this, having witnessed the success of radial engines as used by the US Navy, and designed a highly streamlined mounting for the engine.[4] Instead of leaving the front of the engine "open" to allow cooling air to flow over the cylinders, Tank used a very small opening between the engine cowling and an oversized propeller spinner to admit air. In theory, the use of the tight-fitting cowling also provided some thrust due to the compression of air at speed through the cowling.[5] It was also believed that because the Fw 190 used a radial engine it would not affect production of the Bf 109, furthering the RLM's interest in the Fw 190.[4]

Another revolutionary aspect of the new design was the extensive use of electrically powered equipment replacing the hydraulic systems used by most aircraft manufacturers of the time. On the first two prototypes (described below) the main undercarriage was hydraulic. Starting with the third prototype the undercarriage was operated by push-buttons in the cockpit controlling electric motors in the wings, and was kept in position by electric up- and down-locks.[6]. Similarly the electrically operated landing flaps were controlled by buttons in the cockpit as was the variable incidence tailplane, which could be used to flight-trim the aircraft. The fixed armament was also charged and fired electrically. Kurt Tank believed that service use would prove the electrically powered systems would be more reliable and more rugged than hydraulics, as well as being much easier to service when needed and the absence of flammable hydraulic fluids and vulnerable piping, which was usually prone to leakage, would reduce the fire-risk.

Tank also designed an extremely clean cockpit layout, aided by the use of the electrical equipment. The cockpit had most of the main controls laid out in a logical pattern and incorporated into consoles on either side of the pilot, rather than being placed on the fuselage skinning. [7]

[edit] Prototypes
Fw 190 V1 in its original form with the streamlined engine cowling and ducted spinner. The pointed tip of the internal spinner can also be seen. Pilot is probably Hans Sander.
Fw 190 V1 in its original form with the streamlined engine cowling and ducted spinner. The pointed tip of the internal spinner can also be seen. Pilot is probably Hans Sander.

The first prototype, the Fw 190 V1 powered by a 1,550 hp BMW 139 two-row 14-cylinder radial engine, with civil registration D-OPZE, was flown on 1 June 1939 and soon showed exceptional qualities for such a comparatively small aircraft, with excellent handling, good visibility and speed (initially around 610 km/h (380 mph)).[8] The roll rate was 162 degrees at 410 km/h (255 mph) but the aircraft had a high stall speed of 205 km/h (127 mph). According to the pilots who flew the first prototypes, its wide landing gear made takeoff and landing easier, resulting in a more versatile and safer aircraft on the ground than the Bf 109. The wings spanned 9.5 meters (31 ft 2 in) and had an area of 15 m² (161.46 ft².

Problems with a far-forward cockpit location, directly behind the engine, resulted in a cockpit that became too hot for comfort. In fact during the first flight, the temperature reached 55°C (131°F), after which Focke Wulf's chief test pilot, Hans Sander commented: "It was like sitting with both feet in the fireplace."[9] At first the V1 used a huge spinner, covering the whole area of the forward engine cowling, through which cooling air was ducted; an additional small, pointed spinner fitted inside the duct was intended to compress and speed-up the airflow, in the hope that this would be enough to cool the engine. Flight tests soon showed that the expected benefits of the design could not be realized, and, after the first few flights, this arrangement was replaced by a smaller, more conventional spinner which only covered the hub of the three bladed VDM propeller. In an attempt to increase airflow over the tightly-cowled engine a ten-bladed fan, geared to be driven at 3.12 times the engine speed, was introduced near the mouth of the cowling, which was redesigned. In this form the V1 first flew on 1 December 1939, having been repainted with the Luftwaffe's Balkenkreuz and with the Stammkennzeichen (factory code [10]) RM+CA. [11]

The Fw 190 V2 FL-OZ, (later RM+CB) first flew on 31 October 1939 and was equipped from the outset with the new spinner and cooling fan. It was also was armed with one Rheinmetall-Borsig 7.92 mm MG 17 and one 13 mm MG 131 in each wingroot.[11]

Even before the first flight of the Fw 190 V1 BMW were bench testing a larger, more powerful two-row 14-cylinder radial engine designated the BMW 801. This engine introduced an engine management system called Kommandogerät: in effect a mechanical computer which metered fuel flow, throttle settings and the constant speed propeller.
Fw 190 V5k. This is the V5 with the original small wing. The 12 bladed cooling fan and redesigned undercarriage and canopy fairings can also be seen.
Fw 190 V5k. This is the V5 with the original small wing. The 12 bladed cooling fan and redesigned undercarriage and canopy fairings can also be seen.

The RLM convinced Focke-Wulf and BMW to abandon the 139 engine in favour of the new engine. The 801 engine was similar in diameter to the 139, although it was heavier and longer by a considerable margin. This required Tank to redesign the Fw 190, as a result of which the V3 and V4 were abandoned and the V5 became the first prototype with the new engine. Much of the airframe was strengthened and the cockpit was moved back in the fuselage, which reduced the troubles with high temperatures, and for the first time provided space for nose armament. A 12 bladed cooling fan was adopted, running at three times the engine speed. The sliding canopy was redesigned with the replacement of the rear Plexiglas glazing with duralumin panels. The vertical tail shape was also changed and its tab was replaced by a metal trim strip adjustable only on the ground. New, stiffer undercarriage struts were introduced, the retraction mechanism was changed from hydraulic to electrically powered, wheels of a bigger diameter were used and new fairings of a simplified design were used on the legs. At first the V5 used the same wings as the first two prototypes although, to make room for the bigger undercarriage, the wheel arches were enlarged by moving forward part of the leading edge of the wing root (in this form this prototype was called the V5k for kleine fläche/small wing). The V5 first flew in the early spring of 1940.

However, the weight increase was substantial, 635 kg (1,400 pounds), leading to higher wing loading and a deterioration in handling. As a result, following a collision with a ground vehicle in August 1940 that sent the V5 back to the factory for major repairs, it was rebuilt with a new wing, with a larger area, 18.30 m² (197 ft² and span of 10.506 m (34 ft 5in) and which was less tapered in plan than the original design (the aircraft was now called the V5g for grosse fläche/large wing). This new wing platform was to be used for all major production versions of the Fw 190.[11]

Even with the new engine and the cooling fan, the 801 suffered from very high rear row cylinder head temperatures which, in at least one case, resulted in the detonation of the fuselage mounted MG 17 ammunition. One other shortcoming of the cockpit location was a poor over-the-nose view which lead to handling problems on the ground. More than one ground crash resulted from the lack of familiarity with the new airframe.

Fw 190 A-0 were the pre-production series ordered in November 1940. 28 of these were built: because they were built before the new wing design was fully tested and approved, the first nine of the Fw 190 A-0 had small wings. All were armed with two fuselage-mounted 7.92 mm MG 17s, two wing-root mounted MG 17s and two outboard wing-mounted MG 17s. In detail they were different from later A-series Fw 190s: they had shorter spinners, the armoured cowling ring was a different shape, with a scalloped hinge on the upper, forward edge of the upper engine cowling and the bulges covering the interior air-intakes on the engine cowlings were symmetrical "teardrops'. Also, the panels aft of the exhaust pipes had no cooling slots. Several of these aircraft were later modified for testing engines and special equipment.[11]

Engine problems plagued the 190 for much of its early development, and the entire project was threatened several times with a complete shutdown. If not for the input of Oberleutnants Karl Borris and Otto Behrens, both of whom had enlisted in the Luftwaffe as mechanics, the Fw 190 program might very well have died before reaching the front lines. Borris and Behrens could see past the limitations of the Fw 190 and the 801 and see a formidable fighter. During several RLM commissions that wished to terminate the program, both men indicated that the Fw 190's outstanding qualities outweighed its deficiencies.[12]

The first unit to be equipped with the A-0 was Eprobungsstaffel 190, formed in March 1941 to help iron-out any technical problems and approve the new fighter before it would be accepted for full operational service in mainstream Luftwaffe Jagdgeschwader. At first this unit, commanded by Oblt. Behrens, was based at Rechlin, although it was soon moved to Le Bourget. Some 50 modifications were required before the RLM approved the Fw 190 for deployment to Luftwaffe units.

Engine reliability problems, particularly overheating, continued to plague the Fw 190 until spring 1942 and the availability of the BMW 801 C-2 engine in the Fw 190 A-2. In fact, the problem was relatively easy to solve by rerouting part of the exhaust system, a method discovered by III./JG 26's Technical Officer ("T.O.") Rolf Schrödeter. To quickly implement the fix, it was found the rerouting could be done easily in Gruppe workshops.[12]

Fw 190 A

General characteristics

* Crew: One
* Length: 9.00 m (29 ft 0 in)
* Wingspan: 10.51 m (34 ft 5 in)
* Height: 3.95 m (12 ft 12 in)
* Wing area: 18,30 m² (196.99 ft²
* Empty weight: 3,200 kg (7,060 lb)
* Loaded weight: 4,417 kg (9,735 lb)
* Max takeoff weight: 4,900 kg (10,800 lb)
* Powerplant: 1× BMW 801 D-2 radial engine, 1,272 kW (1,730 hp); 1,471 kW (2,000 hp) with boost

Performance

* Maximum speed: 656 km/h at 4,800 m, 685 km/h with boost (383 mph at 19,420 ft, 408 mph with boost)
* Range: 800 km (500 miles)
* Service ceiling 11,410 m (37,430 ft)
* Rate of climb: 13 m/s (2560 feet/min)
* Wing loading: 241 kg/m² (49.4 lb/ft²
* Power/mass: 0.29 - 0.33 kW/kg (0.18 - 0.21 hp/lb)

Armament

* 2× 13 mm MG 131 machine guns with 475 rounds/gun
* 4× 20 mm MG 151/20 E cannons with 250 rounds/gun in the wing root and 140 rounds/gun outboard.