B-17B / C / D
On 3 August 1937 a contract was issued for ten of the improved B-17Bs. Improvements include the turbo supercharger that had been tested on the Y1B-17A, a larger rudder, fuel systems changes an a redesigned nose area. The nose cone with its rotating machine gun bubble was replaced with an all new multi-piece plexiglas nose cone with serveral ball and socket machine gun mounts. A large aircraft commander's observation bubble was moved to a flattened panel in the nose cone. The DF loop was moved from just above the cockpit to a position on the chin. Because of the B-17s range the navigator was given a position of his own; the Y1B-17 having had a combination bombardier-navigator.
The first B-17B was delivered on 20 October 1939 and on 30 March 1040 the last of the 39 B-17Bs fnially was delivered to the Army. Additional aircraft added to the original contract brought the cost per aircraft down from $274.000 to $207,150. Bone of the B-17Bs would see combat service during World War Two. However many late improvements in the B-17B series were tested and proven on the B series. Some of late B-17Bs were externally indistinguishable from the later C and D series since many of the latters' improvements were incorporated into the B series. The last B-17B was retired on 1 January 1946.
In 1939 the B 17 C (model 299 H) were ordered whose first representative of a series of 38 machines went through his maiden flight on July 21st, 1941. The main difference for the earlier series consisted in the R 1820-65 jet engines with 895 kW each (1200 hp) and seven machineguns
The B-17C was the first version of this bomber which obtained Royal Air Force (British air force RAFs). The 20 copies which arrived in England at the beginning of 1941 were called Fortress I there. They led their first mission under No 90 squadron on July 8th, 1941. As she bombed Wilhelmshaven from 9145 m of height. At the 26 air raids against German aims within the next two months the Fortress Is proved to be not satisfactory. The Americans asserted, though, that they have been used wrongly. The actions had nevertheless let himself be seen at daylight over Germany that the sample didn't need a stronger counter-intelligence arming for any protection for the altitude for alone bot. Urgently to be able to defend itself for the Me 109 fighters who almost effortlessly intercepted it in an altitude of 9750.
For operations over Europe the Fortress Is left till one would have carried out improvements or found other possibilities for more effective use.
In 1940 Boeing received an order for the production from 42 B-17D. These bombers were, so that hardly the model name remained the same different of the B-17C. After all, first war reports had been the reason from Europe that one bullet-proofly executed her tanks and the garrison got an extended tank protection.
These bombers were delivered in 1941.