In the years before World War II, Air Corps engineers improved the Mark XV bombsight and the Army Type C-1 autopilot. During "undisturbed" runs, where speed and altitude were maintained for 15–20 seconds, bombardiers using the Norden could place their bombs within 200 feet of the target from 12,000 to 15,000 feet.
The Norden was essentially an analog computer that addressed the problem of accurately hitting a target from an aircraft at high altitude. The sight had to compensate for flight speed, wind direction, and height. This was accomplished through a collection of gyros, motors, mirrors, gears, and cams. At the heart of the Norden was an autopilot device that allowed the bombardier to control the plane and line up the crosshairs on the target. Bombardiers claimed that the Norden enabled them to place a bomb "in a pickle barrel" from 20,000 feet. But the Norden was accurate only under ideal conditions and with a long, level bomb run to the target. Under combat conditions of flak, fighters, and clouds, results were not so dramatic.
Still, no other country possessed anything comparable to the Norden, and it became one of the most guarded pieces of equipment during the war. The sight was under cover while on the ground, and bombardiers were required to take an oath to destroy the sight if they were shot down. Indeed, it was the origin of the term "black box," as it was carried to the aircraft in a black box.
More than 40,000 Norden sights were built in World War II. It continued to be the primary daytime sight for the U.S. Air Force in the Korean War. Some were recalled for service by the U.S. Navy during 1967–1968 for the Vietnam War.
M. R. Pierce
Jablonski, Edward. Flying Fortress: The Illustrated Biography of the B-17s and the Men Who Flew Them. Garden City, NY: Doubleday, 1965.; McFarland, Stephen L. America's Pursuit of Precision Bombing, 1910–1945. Washington DC: Smithsonian Institution Press, 1995.; Pardini, Albert L. The Legendary Norden Bombsight. Atglen, PA: Schiffer Publishers, 1999.; Parr, Esther, and Nancy Poage. Case History of Norden Bombsight and C-1 Automatic Pilot, March 1943–December 1944. Army Air Forces Special Study, 2 Parts. Patterson Field, OH: Air Technical Service Command, 1945.