As explained by Marshall L. Michel III in his book Schweinfurt-Regensburg 1943, one of the reasons the US Army Air Force (USAAF) committed to daylight precision bombing was the gyrostabilized Norden M-4 bombsight, developed in the mid-1930s, ironically for the US Navy. The USAAF ordered the Norden for its new B-17s, and tests of the Norden/B-17 combination — under ideal weather and visibility conditions — showed that it greatly exceeded the accuracy of its predecessors and would allow precision bombing from high altitude. The press fawned on the Norden, and to add to its mystique no photos were released and the details of how it worked remained top secret.
However, the Norden was best when used by single aircraft that could maneuver to line up on the target independently. In combat, except for the few seconds of the bombing run, all phases of the bombing mission were dominated by considerations of defense, so the maneuvering necessary for the Norden to perform its best could not be met and the Norden bombsight, with its delicate adjustment, lost much of its value.
The conditions that were best for both accuracy and protection from flak would not provide sufficient defense against fighter attacks in combat, and even under good conditions more than half the bombs hit more than 1,000ft from the target. At one point there was consideration of acquiring an inferior sight requiring less careful adjustment, a step which would seriously have compromised the ideal of precision which underlay the American bombardment theory.
The Eighth Air Force Bomber Command hoped that they could survive over Germany unescorted, relying instead on their heavy firepower and tight formations, hence procedures to strike the German targets with enough accuracy while keeping the bombers in their tight defensive formation had to be developed. Additionally, while German fighters were the main threat, flak was a danger over the target. Flak handicapped effective bombing operations not so much by destroying or damaging bombers but rather by forcing the bombers to bomb at high altitudes, which reduced accuracy.
German fighter defenses made it obvious that each bomber could not spread out and make its own bomb run, and as early as January 1943 formation bombing — entire formations dropping their bombs in unison when the lead bomber dropped his — was tried successfully. In March 1943 the Operational Research Section of VIII Bomber Command strongly recommended adopting this technique. In July 1943 VIII Bomber Command’s leadership agreed, and ordered that the combat wings begin to plan to use formation bombing, despite the fact it would be clumsy to maneuver the large formations onto the bombing run and that the resulting bomb pattern would scatter more widely than was the optimum for the desired accuracy.
To make formation bombing work, the wings needed well-coordinated teams of pilot, navigator, and bombardier, and these had to be developed. To that end, VIII Bomber Command directed the establishment of special “lead crews” in each squadron at each station. Squadrons had to identify their best bombardiers and they joined with a specially selected navigator. These lead crews alone would be responsible for identifying the target, leading the unit on the bomb run, locating the release point, and giving the order to release; and the lead crew pilot was chosen for his ability to fly smoothly and make changes gradually to keep formation together. Only three other planes in each group — one wingman of the lead plane and the leaders of the high and low squadrons — carried bombsights, in case the leader was shot down. The mission of the other crews was to stay in tight defensive formations and release when the leader released.
The lead crews underwent intensive training so that they could act as group or squadron lead crews on combat missions. They often carried an additional navigator, and usually the tail gunner’s position was occupied by an officer pilot who advised the pilot on the state of the formation. Finally, the lead crews were only to participate in combat as a lead crew, and their tour would be shortened by five missions. In addition to these crews, two very reliable B-17 aircraft in each squadron were designated as “lead bombers” and equipped with every device for accurate bombing of a target as it became available.
The critical moment in the entire mission was the few seconds immediately before the lead bombardier released the bombs, when he had to perform his final sighting operation and locate the bomb release point. This meant that the lead bomber had to be held as nearly as possible on a steady course without slips, skids, or changes in altitude, and VIII Bomber Command decided that a mechanical instrument could hold this precise position better than a pilot, who might be distracted by flak or attacking fighters. This automatic flight-control equipment (AFCE), an automatic pilot that regulated target approach and bomb run, was developed and first used successfully on Mar. 18, 1943. The AFCE allowed the bombardier to control the aircraft on the bomb run with mechanical precision by the synchronized sighting and pilotage, and enabled him to provide a steadier bombing run than could be achieved even by veteran pilots. Soon all the specially designated “lead” B-17s received the AFCE.
But as the 1943 Combined Bomber Offensive ramped up, two notorious raids forced the Americans to think again about the feasibility of long-range daylight precision bombing. Targeting the factories of Schweinfurt and Regensburg with a huge and innovative double-strike, flying well beyond the range of P-47 escorts, the Americans lost 60 bombers and hundreds of men, temporarily crippling VIII Bomber Command. The follow-up raid on Schweinfurt only repeated the carnage.
The American campaign objective for the 1943 daylight bombing missions deep into Germany was to cripple the Luftwaffe fighter force in order to provide the air superiority vital for the invasion of France, Operation Overlord, to be successful. Eighth Air Force was unable to achieve this campaign objective because the Germans were able to fulfill their own objective of destroying so many Eight Air Force bombers that the Americans stopped their bombing campaign in mid-October 1943.
The real solution to this issue came in the form of the North American P-51B Mustang. The long-range P-51B in fact not only cut bomber losses but quickly gained air superiority over Europe and in many ways made D-Day possible.
Schweinfurt-Regensburg 1943 is published by Osprey Publishing and is available to order here.
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