Focke Wulf FW 190, vol. I

 FW 190A-1 at Rechlin airfield. RLM 74/75/76 camouflage is well visible [photo via Marian Krzyżan]


Design work was put in full swing and a wooden model was soon ready, whereupon a prototype began to be built in the fall of 1938. The new aircraft was an all-metal low-wing, cantilever monoplane of a semimonocoque construction with a fully retractable landing gear. The high power delivered by the BMW 139 was also a drawback of a kind – a problem resulted with effective cooling of the aircraft. To resolve this issue, a special tunnel spinner was used which covered the engine air inlet in order to increase the flow of cooling air and at the same time reduce the pressure drag.
The design work was accompanied by great enthusiasm. For the FW 190 was a real masterpiece when still on the designers’ desks. The body worked out by Kurt Tank was elegant, streamlined, of a strong construction, and at the same time very simple. Therefore, soon noone doubted the potential of the aircraft, which Kurt Tank intended to fit with a BMW engine.
The first unit was hand-made. Each piece of metal was cut out and formed using dies, though it was already assumed that the aircraft would be mass-produced.
The prototype fuselage (and later also production aircraft) was a duralumin semimonocoque construction divided into two segments. The entire fuselage consisted of fourteen frames reinforced by perpendicular longerons. Both segments were assembled separately and then joined with rivets. The rear fuselage segment was combined of three matching parts – two side ones and a bottom one. Under the floor were two self-sealing fuel tanks of 524 liters. With special attention put to the pilot’s safety, the windshield on the production aircraft was a steel welded frame which held a 50 mm thick armor pane in the front and laminated glass panels on the sides. The sliding canopy was made of formed plexi spread over a light steel tube frame. A 12 mm thick armor plate was fixed to the canopy behind the pilot’s head. Besides, three additional armor plates of 5 mm were mounted behind the seat of 8 mm sheet metal.
The wings were a two-spar construction – the main web spar ran along the entire length, the rear spar consisted of two parts. The separate (upper and lower) wing surfaces were riveted on and then joined with formed leading edges. Rounded wing tips were added on during the final stage of assembly, being fixed with bolts. The Focke Wulf’s both wings were first assembled together, and then fixed to the bottom part of the fuselage, whereas each of the Messerschmitt Bf 109’s wings was fixed to the fuselage independently. To save power and speed, the bolts connecting the wing unit to the fuselage were covered with a streamlined plate. The landing gear legs, with oleo-pneumatic shock absorbers, were fixed to the main spar. Initially, a hydraulic landing gear retraction and extension mechanism was used, but soon it was replaced by a very efficient electromechanism that retracted it into bays closed by two-piece formed sheet metal covers. The tire ­pressure could be adjusted depending on the aircraft load between 4.5-5.5 atmospheres. The wings featured split landing flaps covered with sheet metal only on the bottom side. Electromachanically controlled, they had a maximum angle of 60o. The slotted ailerons were a metal structure covered with fabric. The trimming strips could be adjusted on the ground, and they were controlled by a system of pushers.
The metal tail unit was a separate part. The horizontal stabilizers were fully cantilevered, with a tapered contour and rounded tips. The sheet metal control surfaces were set in motion by an electromechanism. The single fin was a semimonocoque construction consisting of two halves joined along the symmetry axis. Its spar was placed askew and, with transverse longerons, it was the mount of the tail wheel, which was released by a clever spring mechanism. The wheel was established in a fork with oleopneumatic shock absorption. It was only retracted halfway with a steel cord activated by the right landing gear leg. The tire pressure was adjusted between four and five atmospheres.
As time would soon show, the FW 190’s strong construction could endure even the worst conditions. Every feature of the plane reflected Kurt Tank’s principles – the construction was to be simple, and its components were to be strong. What mattered was reliability and usefulness. When the prototype was being finished, noone must have suspected that it was the top item of the FW 190 family genealogical tree that would comprise 20,000 machines.
The first prototype, FW 190V1 (W.Nr. 0001), left the Bremen factory in May 1939. It was registered under the civil code of D-OPZE and sent for ground tests. The chief Focke-Wulf test pilot, Flugkapitän Hans Sander, performed initial ground tests, which revealed the engine’s tendency to overheat. It was probably intensified by the lack of cooling fan that had still not been installed. As to taxying on the wide landing gear of the FW 190V1 over the factory airfield
tarmac, it was real pleasure, considering similar maneuvers with the Bf 109. No disturbing symptoms were noticed, and on June 1, 1939 the FW 190V1 took off on its maiden flight. Kurt Tank’s theory was now to be finally tested in practice.
When the aircraft disconnected from the ground and began to perform the obligatory test maneuvers, a crowd of interested engineers gathered on the apron. The first flight allowed them to assess the aircraft’s characteristics. Sander felt both admiration and disappointment. The FW 190V1 displayed excellent piloting features, offering accurate responding to the control surfaces’ movements, although the ailerons needed to be redesigned. Despite this, the aircraft was very agile, and the engine power effectively compensated for the greater aerodynamic drag. Backward visibility was just perfect, and a fantastic speed of 595 km/h at 4,000 m was achieved. The most important, however, was that the main concept – a combination of body harmony, high-performance engine and wide landing gear – proved excellent.

FW 190A-8 of JGr 10. RLM 74/75/76. Parchim airfield (Germany), Autumn of 1944 [Drawings Arkadiusz Wróbel]


Still, the tunnel spinner turned out to be a complete misapplication – the engine tended to overheat and the cockpit temperature rose to 55°C. Later, Hans Sander stated that while flying he “felt as if both feet were kept in a stove”, but at the same time that he was “flying the most beautiful aircraft of those times and the delight in flying the FW 190 was the only memory that remained of this first flight” – a very positive statement, indeed, notwithstanding an unpleasant surprise experienced during the first flight. A great amount of exhaust fumes entered the cockpit through the numerous leaks, and only by immediate use of oxygen mask did he save himself from asphyxia. It was imperative to seal the cockpit.
After a few test flights and slight modifications, the FW 190V1 was sent to the Luftwaffe’s main test and development center at Rechlin. The tests completed there confirmed both the good and bad sides of the new construction, and it is noteworthy that the Rechlin center was the most important advisory body to the RLM. Next, the aircraft was sent back to the manufacturer for the required modifications, the chief one being correction of the cooling installation. As any prototype, the FW 190V1 needed much more time for its construction to be elaborated and series production to be prepared. Of course, mutual accusations were not avoided – Tank accused the engine manufacturer of having delivered a faulty product, while the BMW blamed the engineers for having failed to design a correct cooling system. In the meantime the aircraft was re-registered from civil to military – first as WL-FOLY, and later as FO+LY.
The first thing the engineers did was to check the performance of the tunnel spinner. For this, they used the wind tunnel, and it soon turned out the item did not allow the necessary air flow inside the engine. Besides, its contribution to reduced pressure drag was minimal, so it was eventually given up and replaced by a standard small spinner for protection of the propeller hub. Still, this failed to solve all the issues and the unreliable BMW 139 engine retained its tendency to overheat. Now, the only reasonable solution was to intensify the air flow by employing a ten-bladed fan placed just behind the spinner.
All these innovations were applied to the FW 190V1 and used when building the second prototype, FW 190V2 (W.Nr. 0002, FO+LZ), which became airborne for the first time on October 31, 1939. Aside of the new “regular” spinner and a fan behind, the FW 190 was the first aircraft in history to be armed with MG 17 cal. 7.9 mm and MG 131 cal. 13 mm machine guns. This allowed shooting tests at the Tarnewitz center firing ground. […]

 

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