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. A bombsight is a device used by Bomber aircraft to assist in the task of accurately dropping Bombs on a ground target World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including The Korean War refers to a period of military conflict between North Korean and South Korean regimes with major hostilities lasting from June 25 1950 until the The Vietnam War, also known as the Second Indochina War, or the Vietnam Conflict, occurred in Vietnam, Laos and Cambodia A bomber is a Military aircraft designed to attack ground and sea targets primarily by dropping Bombs on them A bomb is any of a range of devices that typically rely on the Exothermic Chemical reaction of an Explosive material to produce an extremely Its operation was a closely guarded secret of World War II. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including
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Design and operation
The Norden sight was designed for use on US Navy aircraft by Carl Norden, a Dutch engineer educated in Switzerland who emigrated to the US in 1904 and worked on bombsights at the Sperry Corporation before starting his own company. Carl Lucas Norden ( April 23, 1880 – 1965 was a Dutch -born American engineer born in Semarang, Java and educated at the ETH Switzerland (English pronunciation; Schweiz Swiss German: Schwyz or Schwiiz Suisse Svizzera Svizra officially the Swiss Confederation Sperry Corporation (1910-1986 was a major American equipment and Electronics company whose existence spanned more than seven decades of the twentieth century The Norden was later adopted by the USAAF. The United States Army Air Forces ( USAAF) was the military aviation arm of the United States of America during and immediately after World War II. The Norden was initially built at the Norden plant in New York City before the start of WWII and then at several other companies during the war, with a wide variety of different versions being built, all with minor differences.
The complete Norden system consisted of two primary parts, the stabilizer and the sight head. The stabilizer was a gyroscopically leveled platform that gave the sight head a stable base from which to work. The stabilizer was also normally attached to the aircraft's autopilot, allowing it to direct the aircraft back to the same level point as the sight head. An autopilot is a mechanical electrical or hydraulic system used to guide a vehicle without assistance from a human being The sight head had to be carefully aligned to the stabilizer in order to ensure it was looking in the same direction as the aircraft heading.
The sight head contained the main operational portions of the bombsight. It consisted primarily of three parts, a mechanical analog computer that calculated the impact point of the bombs relative to the aircraft as an angle, a small telescope used as the primary sight, and a system of electric motors and gyros that moved the telescope so a single point on the ground remained stationary in the sight. An analog computer (spelt analogue in British English is a form of Computer that uses continuous physical phenomena such as electrical mechanical A telescope is an instrument designed for the observation of remote objects and the collection of Electromagnetic radiation. An electric motor uses Electrical energy to produce Mechanical energy. A gyroscope is a device for measuring or maintaining orientation, based on the principles of Angular momentum. Early examples of the Norden included an "Automatic Gyro Leveling Device" to keep the sight head level with the stabilizer, but this proved to be difficult to maintain and was removed from most examples in the field, replaced by a simple bubble level. A spirit level or bubble level is an instrument designed to indicate whether a surface is Level or Plumb.
The system was operated by pointing the telescope out in front of the aircraft in order to acquire the target while still approaching it. Many Nordens were equipped with a reflector sight to aid in this step. Once turned on, the motors in the sight head would attempt to keep the telescope pointed directly at the selected target, slowly rotating the telescope towards the vertical as the aircraft approached the target. Since the rate of change in the angle depended on the distance to the target and the speed of approach, the bombardier dialed in estimates for airspeed and altitude, which could be read fairly accurately from the aircraft's instruments. A bombardier ( French for " bomberman " in the United States Army Air Forces and United States Air Force, or a bomb aimer
Providing an accurate groundspeed was one of the sources of improved accuracy the Norden provided compared to contemporary instruments. Groundspeed cannot be measured directly from the aircraft, at least not until the introduction of various radar devices, so it had to be calculated by measuring the known airspeed and using a calculated windspeed. The Norden itself was used to make a direct measurement of the groundspeed. During the final approach to target the bombardier would select an easily visible test target and turn the bombsight on with its default settings. Since the aircraft had no information about the windspeed, the test target would drift across the eyepiece as the aircraft moved away from the calculated point. The bombardier then adjusted the sight using a separate set of fine-tuning dials that could be operated by feel while looking through the eyepiece, using them to adjust the drift rates until the target stopped moving in the eyepiece. The dials then held an accurate measurement of windspeed, which could be used for the rest of the bomb run. This was a much more accurate measurement than could be provided by the navigator's drift telescope or dead reckoning. Dead reckoning ( DR) is the process of estimating one's current position based upon a previously determined position or fix, and advancing that position based upon
Once the bombsight was readied and the aircraft was on final approach, the system was turned on and took control of the aircraft's autopilot. An autopilot is a mechanical electrical or hydraulic system used to guide a vehicle without assistance from a human being From that point on the bombsight actually flew the aircraft, attempting to keep it on the chosen path and correcting for any last-minute adjustments provided by the bombardier. At the proper moment it automatically dropped the bombs; the aircraft was moving over 100 feet per second (30 m/s), so even minor interruptions in timing could dramatically affect aim (a problem common in Bomber Command). Bomber Command is an organizational Military unit generally subordinate to the Air force of a Country.
In the European theater, the US introduced an Automatic Flight Control Equipment (AFCE) and a radar system called the H2X (Mickey), which were used directly with the Norden bombsight. The H2X radar, nicknamed the "Mickey set" provided the USAAF with ground mapping capability (for navigation during daylight overcast and nighttime operations in The AFCE served as the mechanical computer “autopilot” of the plane. The radar proved most accurate in coastal regions, as the water surface and the coastline produced a distinctive radar echo.
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. The diplomatic policy whereby a nation seeks to avoid alliances with other nations in order to avoid being drawn into wars not related to direct territorial self-defense has had a long history 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. The United States Army Air Forces ( USAAF) was the military aviation arm of the United States of America during and immediately after World War II.
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. A dive bomber is a Bomber aircraft that Dives directly at its targets in order to provide greater accuracy and limit the exposure to and effectiveness of Types The torpedo bomber first appeared during the later years of World War I. 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. The Battle of the Philippines was the invasion of the Philippines by Japan in 1941–42 and the defense of the islands by Filipino and United Background Naka was the third (and final vessel completed in the Sendai -class of light cruisers and like other vessels of her class she was intended for use Operational history Murasame escorted transports that landed at Vigan City, northwestern Luzon, on December 11 1941 during the 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 Battle of the Coral Sea, fought from May 4 – May 8, 1942, with most of the action occurring on May 7 and May 8, was The Battle of Midway was a major Naval battle, widely regarded as the most important one of the Pacific Campaign of World War II. 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. Skip bombing was a low-level Bombing technique refined for use against Imperial Japanese Navy Warships and transports by Major William Benn
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. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout
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. Jet streams are fast flowing relatively narrow air currents found at the Tropopause, the transition between the Troposphere (where temperature decreases 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. This is the page for mechanical Gears For other uses see Gear (disambiguation For the gear-like device used to drive a roller chain see Sprocket A ball bearing is an engineering term referring to a type of Rolling-element bearing which uses Balls to maintain the separation between the moving parts 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 (see below). In Aviation, the groundcrew is the support crew supplying the Aircraft with fuel and maintenance as opposed to the Aircrew.
Wartime security
Since the Norden was considered a critical wartime instrument, bombardiers were required to take an oath during their training stating that they would defend its secret with their own life if necessary. In case the bomber plane should make an emergency landing on enemy territory, the bombardier would have to shoot the important parts of the Norden with a gun to disable it. As this method still would leave a nearly intact apparatus to the enemy, a thermite gun was installed; the heat of the chemical reaction would melt the Norden into a lump of metal. Thermite is a Pyrotechnic composition of Aluminium powder and a metal oxide which produces an Aluminothermic reaction known as a
After each completed mission, bomber crews left the aircraft with a bag which they deposited in a safe ("the Bomb Vault"). This secure facility ("the AFCE and Bombsight Shop") was typically in one of the base's Nissen hut (Quonset hut) support buildings. The Nissen hut is a prefabricated steel structure made from a semi-circle of corrugated Steel, a variant of which (the Quonset hut) was used extensively The Bombsight Shop was manned by enlisted men who were members of a Supply Depot Service Group ("Sub Depot") attached to each USAAF bombardment group. A United States Army Air Forces (USAAF bombardment group was a military combat unit during the Second World War. These shops not only guarded the bombsights but performed critical maintenance on the Norden and related control equipment. This was probably the most technically skilled ground-echelon job, and certainly the most secret, of all the work performed by Sub Depot personnel. The non-commissioned officer in charge and his staff had to have a high aptitude for understanding and working with mechanical devices. A non-commissioned officer (sometimes noncommissioned officer) also known as an NCO or Noncom, is an enlisted member of an Armed force
As the end of World War II neared, the bombsight was gradually downgraded in its secrecy; however, it was not until 1944 that the first public display of the instrument occurred. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including
Its last use in combat was by the Naval Air Observation Squadron Sixty-Seven (VO-67), during the Vietnam War. The bombsights were used in Operation Igloo White for implanting Air-Delivered Seismic Intrusion Detectors (ADSID) along the Ho Chi Minh Trail. Operation Igloo White was a covert United States Air Force electronic warfare operation conducted from late January 1968 until February 1973 during the Vietnam War The Ho Chi Minh trail was a logistical system that ran from the Democratic Republic of Vietnam (North Vietnam to the Republic of Vietnam (South Vietnam through
Espionage
Herman W. The Duquesne Spy Ring is the largest Espionage case in United States history that ended in convictions Lang had been employed by the Carl L. Norden Company. During a visit to Germany in 1938, Lang conferred with German military authorities and reconstructed plans of the confidential materials from memory. In 1941, Lang, along with the 32 other German agents of the Duquesne Spy Ring, was arrested by the FBI in the largest espionage conviction in U. The Duquesne Spy Ring is the largest Espionage case in United States history that ended in convictions S. History. He received a sentence of 18 years in prison on espionage charges and a 2-year concurrent sentence under the Foreign Agents Registration Act. The Foreign Agents Registration Act is a United States law passed in 1938 requiring information from foreign sources to be properly identified to the American public
German instruments were actually fairly similar to the Norden, even before the war. A similar set of gyroscopes provided a stabilized platform for the bombardier to sight through, although the more complex interaction between the bombsight and autopilot was not used.
See also
- Stabilizing Automatic Bomb Sight (SABS) a Royal Air Force bomb sight introduced for precision bombing with similar capabilities to the Norden bomb sight. The Stabilizing Automatic Bomb Sight (SABS was an improved precision Bomb sight introduced into operational service by the Royal Air Force (RAF in 1943
- Lotfernrohr 7, a similar German bombsight. The Carl Zeiss Lotfernrohr 7, or Lotfe 7, was the primary late-war Bombsight used in most Luftwaffe level bombers
References
This article incorporates text from http://foia.fbi.gov/foiaindex/duquesne_frederick_interesting.htm Federal Bureau of Investigation: Frederick Duquesne Interesting Case Write-up (publicly released on March 12, 1985 under the Freedom of Information Act), a public domain work of the United States Government. Events 538 - Witiges, king of the Ostrogoths ends his siege of Rome and retreats to Ravenna, leaving Year 1985 ( MCMLXXXV) was a Common year starting on Tuesday (link displays 1985 Gregorian calendar) The public domain is a range of abstract materials &ndash commonly referred to as Intellectual property &ndash which are not owned or controlled by anyone A work of the United States government, as defined by United States copyright law, is "a work prepared by an officer or employee of the U Accessed: 2007–05–12
Further reading
Books
- Stewart Halsey Ross: "Strategic Bombing by the United States in World War II"
Features a chapter about the bombsights used by the USA. It describes the development, the fallacies, its use and how Germany soon learned about the Norden. - Albert L. Pardini: "The Legendary Norden Bombsight"
The first detailed volume to cover the Norden Bombsight. 352 pages with over 70 b/w photographs plus line art. ISBN 0-7643-0723-1, Schiffer Publishing, 1999. - "The Norden Bombsight"
A classified manual during WW II, this is a complete guide to maintenance and calibration of the Norden bombsight. 200+ pages. - "Bombing – Students' Manual"
This WW II bombardiers instruction book includes Norden bombsight instruction and more. 250+ pages, illustrated. - "Bombardier's Information File"
This manual features instructions for the use of the Norden Bombsight, and other bomb sights as well. Illustrated with photos of bombs, cameras, various equipment, etc. - Loyd Searle: "The Bombsight War: Norden vs. Sperry"
Gives many details of the history and behind-the-scenes development of the NBS and its competitor. Spectrum IEEE #0018-92235/89/0900-0060, September 1989, http://www.thevaluesell.com/images/LSearle_bombsight.pdf
Articles
- Norden Bombsight from the Hill Aerospace Museum
- Last Combat Use Observation Squadron Sixty-Seven ( VO-67 )
- U.S. Centennial of Flight Commission
- Additional images and detailed information
- WWII AAF collection (Bombardiers Information File)
- (Movies of the Norden and Sperry Bombsights in operation)
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