The Norden bombsight was a bombsight used by the United States Army Air Force during World War II, the Korean War, and the Vietnam War to aid the crew of bomber aircraft in dropping bombs accurately. Its operation was a closely guarded secret of World War II.
Operational efficiency
The Norden was developed during a period of United States non-interventionism when the dominant US military strategy was the defense of the United States and its possessions. A considerable amount of the US's strategy was based on stopping attempted attacks at sea, both with direct Naval power, and starting in the 1930s, with US Army Air Force airpower.
Airpower had been coming into its own as an anti-shipping weapon, but hitting a moving ship at sea was a difficult task. Most forces of the era invested heavily in dive bombers or torpedo bombers, but these generally had limited range and were only suitable in a strategic sense for carrier basing. The Army instead invested in the combination of the Norden and B-17, which it was believed would have enough accuracy to allow formations of B-17s to successfully attack shipping at long distances from the USAAF's land bases. Using the Norden, bombardiers could, in theory, drop their bombs within a 100 foot (ca 30 m) circle from an altitude of well over 20,000 feet (ca. 7 km). The high altitude would allow for long cruising ranges and keep them out of range of most ship-borne anti-aircraft fire while the bomb pattern would still give an acceptable probability of a "hit". The Norden was marketed as the tool to win the war; and it was often claimed that the bombsight could drop bombs into pickle barrels.
In practice the Norden never managed to produce accuracies remotely like those it was theoretically capable of. The RAF were the first to use the B-17 in combat, and reported extremely poor results, eventually converting their aircraft to other duties. USAAF anti-shipping operations in the far east were likewise generally unsuccessful, and although there were numerous claims of sinkings, the only confirmed successful action was during the Battle of the Philippines when B-17s damaged two Japanese transports, the cruiser Naka, and the destroyer Murasame, and sank one minesweeper. However these successes were the exception to the rule; actions during the Battle of Coral Sea or Battle of Midway, for instance, were entirely unsuccessful. The USAAF eventually replaced all of their B-17s with other aircraft, and came to use the skip bombing technique in direct low-level attacks.
In Europe the Norden likewise demonstrated a poor real-world accuracy. Under perfect conditions only 50 percent of American bombs fell within a quarter of a mile of the target, and American flyers estimated that as many as 90 percent of bombs could miss their targets.[1][2][3] Nevertheless many veteran B-17 and B-24 bombardiers swore by the Norden.
Many factors have been put forth to explain the Norden's poor performance. Over Europe the cloud cover was a common explanation, although performance did not improve even in favorable conditions. Accuracy did improve with the introduction of the "master bomber" concept, under which only a single aircraft would actually use the Norden while the rest simply dropped on their command. This suggests that much of the problem is attributable to the bombardier. Over Japan, bomber crews soon discovered strong winds at high altitudes, the so-called jetstreams, but the Norden bombsight worked only for wind speeds with minimal wind shear. Additionally, the bombing altitude over Japan reached up to 30,000 feet (9,100 m), but most of the testing had been done well below 20,000 ft (6,100 m) An additional factor was that the shape and even the paint of the bomb mantle greatly changed the aerodynamic properties of the weapon; and, at that time, nobody knew how to calculate the trajectory of bombs that reached supersonic speeds during their fall.
In both theaters of war, one vulnerability was that when the bombardier auto-piloted the aircraft using the bombsight, the aircraft was more susceptible to anti-aircraft fire and collisions with other allied aircraft.
As a mechanical device, the Norden bombsight used complex machinery consisting of many gearwheels and ball bearings, which were prone to produce inaccuracies if not properly maintained. In fact, many bombsights were rushed to war use without thorough testing. Often the bombardier had to oil and repair failures himself. For some time into the war equipped and qualified groundcrew technical staff were simply not available in sufficient numbers
Airpower had been coming into its own as an anti-shipping weapon, but hitting a moving ship at sea was a difficult task. Most forces of the era invested heavily in dive bombers or torpedo bombers, but these generally had limited range and were only suitable in a strategic sense for carrier basing. The Army instead invested in the combination of the Norden and B-17, which it was believed would have enough accuracy to allow formations of B-17s to successfully attack shipping at long distances from the USAAF's land bases. Using the Norden, bombardiers could, in theory, drop their bombs within a 100 foot (ca 30 m) circle from an altitude of well over 20,000 feet (ca. 7 km). The high altitude would allow for long cruising ranges and keep them out of range of most ship-borne anti-aircraft fire while the bomb pattern would still give an acceptable probability of a "hit". The Norden was marketed as the tool to win the war; and it was often claimed that the bombsight could drop bombs into pickle barrels.
In practice the Norden never managed to produce accuracies remotely like those it was theoretically capable of. The RAF were the first to use the B-17 in combat, and reported extremely poor results, eventually converting their aircraft to other duties. USAAF anti-shipping operations in the far east were likewise generally unsuccessful, and although there were numerous claims of sinkings, the only confirmed successful action was during the Battle of the Philippines when B-17s damaged two Japanese transports, the cruiser Naka, and the destroyer Murasame, and sank one minesweeper. However these successes were the exception to the rule; actions during the Battle of Coral Sea or Battle of Midway, for instance, were entirely unsuccessful. The USAAF eventually replaced all of their B-17s with other aircraft, and came to use the skip bombing technique in direct low-level attacks.
In Europe the Norden likewise demonstrated a poor real-world accuracy. Under perfect conditions only 50 percent of American bombs fell within a quarter of a mile of the target, and American flyers estimated that as many as 90 percent of bombs could miss their targets.[1][2][3] Nevertheless many veteran B-17 and B-24 bombardiers swore by the Norden.
Many factors have been put forth to explain the Norden's poor performance. Over Europe the cloud cover was a common explanation, although performance did not improve even in favorable conditions. Accuracy did improve with the introduction of the "master bomber" concept, under which only a single aircraft would actually use the Norden while the rest simply dropped on their command. This suggests that much of the problem is attributable to the bombardier. Over Japan, bomber crews soon discovered strong winds at high altitudes, the so-called jetstreams, but the Norden bombsight worked only for wind speeds with minimal wind shear. Additionally, the bombing altitude over Japan reached up to 30,000 feet (9,100 m), but most of the testing had been done well below 20,000 ft (6,100 m) An additional factor was that the shape and even the paint of the bomb mantle greatly changed the aerodynamic properties of the weapon; and, at that time, nobody knew how to calculate the trajectory of bombs that reached supersonic speeds during their fall.
In both theaters of war, one vulnerability was that when the bombardier auto-piloted the aircraft using the bombsight, the aircraft was more susceptible to anti-aircraft fire and collisions with other allied aircraft.
As a mechanical device, the Norden bombsight used complex machinery consisting of many gearwheels and ball bearings, which were prone to produce inaccuracies if not properly maintained. In fact, many bombsights were rushed to war use without thorough testing. Often the bombardier had to oil and repair failures himself. For some time into the war equipped and qualified groundcrew technical staff were simply not available in sufficient numbers
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