Focke Wulf Fw 190 V1 D-OPZE featured an oversized ducted spinner in an unsuccessful attempt to combine lower drag with sufficient cooling. D-OPZE WNr. 0001 first flew from the Focke Wulf Bremen works field (Neuenlander Feld) on 1 June 1939 with Flugkapitän Hans Sander, Focke-Wulf’s chief test pilot, at the controls. In order to keep drag in high-speed flight as low as possible, the BMW 139 featured a 'closely cowled' housing reducing any significant curves, which would lead to local spikes in air velocity. The spinner fairing was designed in such a way that it merged into the hub casing without a step and with a slight curvature forming an annular duct with the propeller hub fairing, through which cooling air was fed to the engine. The cooling air outlet was regulated on the underside of the fuselage by butterfly flaps. The flaps were adjusted on the ground. The front part of the cowling was rigidly connected to the engine. The cylinders were accessible through large flaps.These hinged down cowl parts were held by safety wires and could serve as a platform. The centre parts of the cowling with the inlet manifolds were easily detachable
The V2 coded 'RM+CB' was photographed at Tarnewitz in early 1940 undergoing weapons testing - an MG 17 and an MG 131 in each wing root - with a similar close cowl ducted spinner arrangement.
While it had been calculated that this arrangement would improve the aircraft’s top speed by 25 mph the gap between the spinner and the engine housing resulted in enough drag to cancel out any aerodynamic benefits. The ducted spinner arrangement was of course also prone to overheating, even with the spinner hub cover removed. During the winter of 1939-40 the V1 was fitted with a new 'conventional' NACA-profile radial engine cowl featuring a ten-bladed cooling fan. During this period BMW was testing a larger version of the BMW 139 some 159 kg heavier, the BMW 801. Because of its increased size the BMW 801-powered Fw 190 would require changes to the airframe and production of the V3 and the V4 was stopped. Changes to the V5 including modifying the CG by moving the cockpit further aft which at the same time eased the engine overheating problem from the pilot perspective and allowed upper cowl MGs (Rumpfbewaffnung) to be fitted between the engine and the windscreen. Armoured plate protection for the pilot could also be incorporated into the design. The first test flights of this heavier machine powered by the BMW 801 C took place during August 1940 and proved disappointing in comparison to the performance of the V1. The solution was the design of a new bigger wing ('V5g' = groß) which reduced wing-loading and at the same time the larger wing roots would enable heavier armament to be fitted. Whilst testing continued, construction of forty pre-production aircraft (the A-0) began. Work on the so-called Null-Serie machines was in fact so far advanced that WNr. 0008 -0014 received the original 'small' wing. Many of these machines were rebuilt to serve as test-beds for later variants. In March 1941, six aircraft were assigned to the Erprobungsstaffel 190, the unit responsible for operationally testing the Fw 190, at Rechlin-Roggenthin. This unit was essentially made up from elements of II./Jagdgeschwader 26 and was commanded by Oblt. Otto Behrens.
