Dornier Do 317

The Dornier Do 317 was a planned German heavy bomber of World War II.

Design and development
In June 1940, Dornier produced plans for further development of the Do 217, which would have a pressurized cabin and more powerful engines (DB 604 or Jumo 222) and would be designated the Do 317. The Do 317 was one of the proposals submitted to the RLM for the "Bomber B" project. Two versions of the Do 317 were proposed: the simplified Do 317A powered by two DB 603A engines and featuring conventional defensive armament, and the more advanced Do 317B with DB 610A/B engines, remotely-aimed Fernbedienbare Drehlafette-style gun turrets, heavier bombload, and an extended wing.

Six prototypes of the Do 317A were ordered, and the first of these, the Do 317 V1, commenced its flight test program on 8 September 1943. The Do 317 V1 was very similar in appearance to the Do 217, but featured a pressurized cabin and triangular tail fins. Trials with the Do 317 V1 revealed no real performance advance over the Do 217, so it was decided to complete the remaining five prototypes without cabin pressurization equipment and employ them as Henschel Hs 293 missile launchers. In this form the prototypes were redesignated Do 217R. At this time, the Do 317B project was abandoned due to changing wartime conditions.