B-17 Flying Fortress The Boeing B-17 Flying Fortress was the first mass-produced, four-engine heavy bomber. It is still one of the most recognised aeroplanes ever built. It was most widely used for daylight strategic bombings of German industrial targets during World War II as part of the United States Eighth Air Force. Development Operational History Variants/Design Stages Units Using the B-17 Noted B-17 Pilots Specifications

B-17 Flying Fortress

The Boeing B-17 Flying Fortress was the first mass-produced, four-engine heavy bomber. It is still one of the most recognised aeroplanes ever built. It was most widely used for daylight strategic bombings of German industrial targets during World War II as part of the United States Eighth Air Force.

Variants/Design stages

The B-17 went through several iterations in each of its design stages and variants. Of the thirteen YB-17s ordered for service testing, only one was actually used. Experiments on this plane led to the use of a turbo-supercharger, which would become standard on the B-17 line. When this aircraft was finished with testing, it was redesignated the B-17A, and was the first plane to enter service under the B-17 designation.

CLICK IMAGE TO ENLARGE Top view of a B-17F in flight

As the production line developed, Boeing engineers continued to improve upon it. To improve performance, the original design was altered to include larger flaps, a larger rudder, and a new nose. The engines were upgraded to more powerful versions several times. Similarly, the gun stations were altered on numerous occasions to enhance their effectiveness.

By the time the B-17G appeared, the number of guns had been increased from seven to thirteen, the designs of the gun stations were finalised, and other adjustments were complete. In this, it incorporated all changes made in its predecessor, the B-17F (which was the first mass-produced version of the B-17). The B-17G is generally considered the defining version of the B-17. Some 8680 were built, and many were converted for other missions, such as cargo-carrying, engine testing, and reconnaissance.

Two versions of the B-17 were flown under different designations. These were the XB-38 and the YB-40. The former was an engine test bed for Allison V-1710 liquid-cooled engines, to test the engine should the Wright engines normally used on the B-17 become unavailable. The YB-40 was a modification of the standard B-17 used before the P-51 Mustang became available. Since no fighters had the range to escort the B-17, a heavily armed modification was used instead with an additional power turret in the radio room, a chin turret (which went on to become standard with the B-17G) and twin .50 caliber (12.7 mm) guns in the waist positions. The ammunition load was over 11,000 rounds making the YB-40 well over 10,000 pounds (4,500 kg) heavier then that of a fully loaded B-17F. Unfortunately, the YB-40s with their numerous heavy modifications had trouble keeping the pace with empty bombers, and the project was abandoned with the arrival of the Mustang and phased out in July of 1943.

Late in World War II, at least 25 B-17s were fitted with radio controls, loaded with 12,000 lb (5443 kg) of high explosives, dubbed 'BQ-7 Aphrodite missiles,' and used against U-boat pens and bomb-resistant fortifications. Because few (if any) BQ-7s hit their target, the Aphrodite project was scrapped in early 1945. (×24)

During and after World War II, a number of weapons were tested and used operationally on B-17's. Some of these weapons included razons (radio guided), glide bombs, and the JB-2 Thunderbugs's, the equivalent of the German V-1 Buzz Bomb.

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