The Boeing model 299 was an amazingly successful aircraft, a total of 12,731 were produced. The very first model was displayed to the public on July 16, 1935. We know the aircraft as the B-17 Flying Fortress.
Improvements to the aircraft were frequent reflecting the needs of the AAF and lessons learned in combat. Design variants include Y1B-17, YB-17A, B-17B, B-17C, B-17D, B-17E, B-17F, YB-40, B-17G, and post war the B-17H conversion of some B-17Gs (redesignated SB-17G). The B-17 saw extensive post war service in a wide variety of roles until it was retired in 1956.
The 381st Bombardment Group (Heavy) deployed to England with the B-17F. Those aircraft were replaced as the B-17G became available. The 381st also acquired one B-17E used as a group hack.
To meet production demand, the B-17F was the first model to be produced jointly by Boeing, Lockheed Vega, and Douglas. Despite identical engineering specs, the Fortresses produced by each of these factories had unique differences and modifications.
The biggest visual difference between the F model and the G model for the lay person is the addition of the Bendix Chin Turret. However you should note that at least eighty of the last F models produced were equipped with the turret before leaving the factory. Identification of model type and block number is best determined through the aircraft's serial number.
The last Flying Fortress built, a G model, was finished in August 1945. The Flying Fortress had an amazing history and was truly a testament to the manufacturing capacity and skill of the American worker. The B-17 per unit cost in 1942 was $258,949 and fell to an average cost of $187,7421. This was due to streamlined manufacturing techniques and a reduction in the "man" hours required to assemble the aircraft, only 18,600 hours by 19442.
The interior of the aircraft was by no means spacious, but it did accommodate a standard crew of ten. From nose to tail the positions were: Bombardier, Navigator, Pilot & Co-pilot, Top Turret/Engineer, Radio Operator, Ball Turret Gunner, Left and Right Waist Gunners, and finally the Tail Gunner.
In the sidebar illustration we can see the positions of the crew forward of the bomb bay. The Bombardier sits in front of the nose to operate the bomb sight. In the G model he also operated the Bendix Chin Turret from the same position.
The Navigator is at his table. Pilot and Copilot sit side by side, pilot on the left seat, copilot in the right. Behind them is the Top Turret Operator/Engineer. In this illustration he is manning the turret.
The bailout diagram below shows the positions of the Radio Operator and the Waist Gunners.
Two of the sidebar graphics show the unique positions of the Ball Turret Gunner and the Tail Gunner.
1 Freeman & Osborne, page 27.