Norden bombsight

The Norden Mk. XV, known as the Norden M series in Army service, was a bombsight used by the United States Army Air Forces (USAAF) and the United States Navy during World War II, and the United States Air Force in the Korean and the Vietnam Wars. It was the canonical tachometric design, a system that allowed it to directly measure the aircraft's ground speed and direction, which older bombsights could only measure inaccurately with lengthy in-flight procedures. The Norden further improved on older designs by using an analog computer that constantly calculated the bomb's impact point based on current flight conditions, and an autopilot that let it react quickly and accurately to changes in the wind or other effects.

Together, these features allowed for unprecedented accuracy in day bombing from high altitudes; in testing the Norden demonstrated a circular error probable (CEP) of 23 metres (75 ft), an astonishing performance for the era. This accuracy allowed direct attacks on ships, factories, and other point targets. Both the Navy and the AAF saw this as a means to achieve war aims through high-altitude bombing; for instance, destroying an invasion fleet by air long before it could reach US shores. To achieve these aims, the Norden was granted the utmost secrecy well into the war, and was part of a then-unprecedented production effort on the same scale as the Manhattan Project. Carl L. Norden, Inc. ranked 46th among United States corporations in the value of World War II military production contracts.

In practice it was not possible to achieve this level of accuracy in combat conditions, with the average CEP in 1943 being 370 metres (1,200 ft). Both the Navy and Air Forces had to give up on the idea of pinpoint attacks during the war. The Navy turned to dive bombing and skip bombing to attack ships, while the Air Forces developed the lead bomber concept to improve accuracy, while adopting area bombing techniques by ever larger groups of aircraft. Nevertheless, the Norden's reputation as a pin-point device lived on, due in no small part to Norden's own advertising of the device after secrecy was reduced late in the war.

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