Dornier Do 317

The Dornier Do 317 was a prototype German medium bomber of World War II.

Design and development
In 1939, Dornier produced plans for a further development of the Do 217, which would have a pressurized cabin and more powerful engines (DB 604, BMW 802 or Jumo 222). Designated Do 317, it was one of the four 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 the heavy, 1.5 tonnes apiece, counter-rotating DB 610A/B "power system" engines, remotely aimed Fernbedienbare Drehlafette (FDL)-style gun turrets, higher bombload, and an extended wing. The "Bomber B" project was partially based on improved engines, however its engines such as the DB 604 and Jumo 222 failed to reach full production. As a result, the Do 317 had to use the less powerful engines.

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 217K and M models, with a visually reframed slight variation of its multiple glazed-panel "stepless cockpit", fully glazed nose design that accommodated a pressurized cabin provision, and triangular tailfins. Trials with the Do 317 V1 revealed no real performance advance over the Do 217, and before long the Do 317B variant was shelved and the other five Do 317 prototypes were completed as unpressurised Do 217Rs. They were issued to III./KG 100 in Autumn 1944, but saw little or no operational service.