Staff Writer (Updated: 4/25/2016):
Designed to a US requirement for a four-engine bomber capable of long distance travel with a full 2,000lb bombload and reach speeds between 200 and 250 miles per hour. The result was the Boeing Model 229 which first flew in 1934, though was later lost to pilot error. Nevertheless, the US Army Air Corps pursued the design with an order for further developmental models fitted with differing powerplants. Early B-17 models were mostly developmental production variants that included the additions of seal-sealing fuel tanks, better armor protection and a redesigned tail. The initial definitive Flying Fortress model would arrive with 512 examples of the B-17E model which were the first to incorporated the twin .50 caliber tail armament for defense. This model was followed by the similar B-17F models of which 3,405 were produced. This latter model featured revised defensive armament positions. Often regarded as the ultimate B-17 production model, the B-17G featured the identifiable and effective Bendix powered chin turret fitted with 2 x 12.7mm machine guns under the nose. Revised turbochargers and an increase to 13 .50 caliber machine guns also arrived with this G model. In the end, the B-17G would account for over 8,600 units with production split between Boeing (4,035 samples), Douglas (2,395 samples) and Lockheed Vega (2,250 samples).
B-17 Flying Fortresses followed common practice in that they flew in what was known as the "box formation". This formation allowed every gunner on board the aircraft to bring their guns to bear to any position needed. Gunner positions on the B-17 included a top turret gunner manning 2 x 12.7mm machine guns, a tail gunner manning 2 x 12.7mm machine guns, a belly gunner manning 2 x 12.7mm machine guns, 2 x cheek gun emplacements, staggered waist gunner positions each manning a single 12.7mm machine gun and the Bendix chin turret. A limited-arc-of-fire, single 12.7mm machine gun position at the radio operators area was available in early models but later removed. The flight engineer doubled as the top turret gunner while the bombardier and navigator in the nose section doubled as front gunners. The belly turret gunner was generally of a small stature to be able to fit into the limited-space turret system. All positions were afforded some type of built-in armor protection but this varied extensively by position.
The bombardier and navigator were awarded the best views of the sky through the large plexiglas nose. The bombardier sat on a type of swiveling stool with the fabled Norden Bombsight before him. The navigator sat off-set to his rear at a small map-filled desk. Both were supplied with defensive .50 caliber machine guns with the Bendix chin turret under the bombardiers control in the G model and onwards. Access to the nose was accomplished through a smallish passage way underneath the main flight deck.