After the Y1B-17A (there was no B-17A), the first production version of the aircraft, the B-17B, was introduced and featured numerous changes over the Y1B-17 and Y1B-17A. However, only ten of the improved B-17Bs were ordered in August of 1937 while during that same year 177 B-18s were ordered. While the B-17 had made a place for itself in the Army Air Corps roster, it was still a very small place indeed.
The first major difference was the installation of turbosuperchargers that had been tested on the Y1B-17A even though that testing was still going on. The Army had been so impressed by the early test of this technology that it felt necessary that all heavy bombers be equipped with them. Also, a larger rudder was installed on the B model to improve its lateral stability, a minor problem crews mentioned about the previous models. It offered better directional controls at the higher altitudes the B-17B would be flying at with it's turbosuperchargers.
Another major difference was the redesigning of the nose section of the aircraft. The navigator position was moved from behind the pilots on the flight deck to the nose compartment. Before, the navigator and bombardier positions were handled by one crewmember. Now the positions would be separated and handled by two different crew members in the nose. The nose gunner position in the Y1B-17 models would now become the bombardiers position. However, the bombardier would not have to man the hard to use gun blister and rotating nose cone of the Y1B-17 series. Now the nose was redesigned as a framed Plexiglas nosecone with a new blister for the .30 caliber machine gun in a pivot mount. The bottom plate of this nosecone was flattened to allow the bombardier to aim his bombsight through the nosecone at the front of the aircraft. This meant the nose of the B-17B was about seven inches shorter than the previous aircraft and did away with the drag-inducing bombsight cutout that was under the nose of the Y1B-17s. With this redesigned nose, a transparent bubble molding was added to the roof of the flight deck just behind the pilots. This bubble was to be used for fire control when the aircraft was under attack and was to be manned by an observer that rode in a seat behind the pilots. A second seat was also installed for a aircraft commander.
The wings of the B-17B were also redesigned some. While their overall length remained the same, the section of wing with the engine nacelles was extended. This added room for the turbosuperchargers and allowed for longer flaps. These new flaps helped tremendously when the plane was loaded down during take offs and landings.
The revolutionary new air-brake system that saw its debut on the 299 and was carried on through the Y1B-17s was found to be very problematic. Designers now replaced these troublesome brakes with more reliable hydraulic brakes.
The original order of ten aircraft was soon upped to thirteen. The reason for this is because thirteen was the number of aircraft needed to outfit an entire squadron. Soon, two more orders for thirteen aircraft apiece followed upping the total number of B-17Bs on order to thirty-nine.
The reason for this reversal in the Army's way of thinking was simple. The war had started on September 1, 1939, not even a month after the first order for ten had been placed by the Army. One of the main German weapons that allowed for that country's swift victory over the Polish army was the use of bombers. The Stuka JU-87 dive bomber was the headline grabber but the JU-88 and DO-217 and other German medium bombers also played a major part. In Britain, and the rest of the world for that matter, the idea of enemy bombers destroying their cities became a major fear.
Even while those in the decision making positions within the Army may have changed their mind about the B-17 and Strategic Bombing, most kept it to themselves and did not mention the offensive capabilities of the B-17 outside their own close personal friends because of the still-prevailing attitude of U.S. Isolationism. It is shown by these additional orders, however, that more of these decision makers believed that there should be more heavy bombers in the U.S. arsenal.