new proposal was put forth for the Fw 191B series. The V7 through V12 machines were abandoned in favor of using the Fw 191 V13 to install a pair of Daimler Benz DB 606 or 610 "power system" engines, which were basically coupled pairs of either DB 601 or 605 12-cylinder engines. Their lower power-to-weight ratio from their 1.5 tonne weight for each "power system", meant that the armament and payload would have to be reduced. It had already been decided to delete the engine nacelle gun turrets, and to make the rest manually operated. Five more prototypes were planned with the new engine arrangement, V14 through V18, but none were ever built, possibly from the August 1942 condemnation by Reichsmarschall Hermann Göring of the coupled "power system" DB 606 and 610 powerplants as "welded-together engines", in regards to their being the primary cause of the unending series of powerplant problems in their primary use, as the engines on Heinkel's He 177A Greif, Germany's only production heavy bomber of World War II. One final attempt was made to save the Fw 191 program, this time the Fw 191C was proposed as a four engined aircraft, using either the 1,340 PS (1,322 hp, 986 kW) Jumo 211F, the 1,350 PS (1,332 hp, 993 kW) DB 601E, the 1,475 PS (1,455 hp, 1,085 kW) DB 605A or similar rated DB 628 engines. Also, the cabin would be unpressurized and the guns manually operated, with a rear step in the bottom of the deepened fuselage — in the manner of the near-ubiquitous Bola gondola used by the majority of German bombers for ventral defense under the nose — being provided for the gunner. Focke-Wulf used the designations Fw 391 and Fw 491 for the different variants of the Fw 191C, but these were unofficial and never allocated by the RLM. The "Bomber B" program had been canceled, due mainly to no engines of the 2,500 PS class being available, which was one of the primary requirements in the "Bomber B" program. Although the Fw 191 will be remembered as a failure, the airframe and design eventually proved themselves to be sound; only the underpowered engines and insistence on electric motors to operate all the systems doomed the aircraft. There were only three Fw 191s built (V1, V2 and V6), and no examples of the Fw 191B or C ever advanced past the design