Item Description
Original Item: Only One Available. This is one of the the most complete USAAF WW2 Norden bombsight we've ever seen and it is offered in excellent condition! It consists of the Model M9B head or "bombsight football" manufactured by Carl L. Norden Inc Serial "N 11444", Stabilizer, C-1 Auto Pilot serial number "R-1681", Maxson reflex sight serial number "8111" which was known to be fitted on B-29s, portable tachometer made by "Jaeger Watch Co." and dated 1945, military marked Elgin stop watch, Roller-Smith "PDI" meter, Polaroid lens filter kit in original box and tangent scales for automatic bombing computer from the late 1940's. Comes with original training manuals from the 1940s plus several reprints from a later date. We even include a bombardiers commemorative acrylic Lucite cube paperweight which has a die cast norden bomb sight in the center. A similar sight which was in not a complete as this one sold at auction for $13,200 in 2018, you can verify it at this link. A Norden Model M9B bombsight was the same model sight used by Tom Ferebee to drop the first atomic bomb on Hiroshima on August 6th, 1945. The sight he used, V 4120, is permanently installed inside the Enola Gay herself in the National Air and Space museum.
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 seemed to promise unprecedented accuracy in day bombing from high altitudes; in peacetime 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 the expected accuracy in combat conditions, with the average CEP in 1943 of 370 metres (1,200 ft) being similar to Allied and German results. 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.
The Norden saw some use in the post-World War II era, especially during the Korean War. Post-war use was greatly reduced due to the introduction of radar-based systems, but the need for accurate daytime attacks kept it in service for some time. The last combat use of the Norden was in the US Navy's VO-67 squadron, which used them to drop sensors onto the Ho Chi Minh Trail as late as 1967. The Norden remains one of the best-known bombsights of all time.
As U.S. participation in the war started, the U.S. Army Air Forces drew up widespread and comprehensive bombing plans based on the Norden. They believed the B-17 had a 1.2% probability of hitting a 30 metres (100 ft) target from 6,100 metres (20,000 ft), meaning that 220 bombers would be needed for a 93% probability of one or more hits. This was not considered a problem, and the AAF forecast the need for 251 combat groups to provide enough bombers to fulfill their comprehensive pre-war plans.
After earlier combat trials proved troublesome, the Norden bombsight and its associated AFCE were used on a wide scale for the first time on the 18 March 1943 mission to Bremen-Vegesack, Germany; The 303d Bombardment Group dropped 76% of its load within a 300 metres (1,000 ft) ring, representing a CEP well under 300 m (1,000 ft) As at sea, many early missions over Europe demonstrated varied results; on wider inspection, only 50% of American bombs fell within a 400 metres (1⁄4 mi) of the target, and American flyers estimated that as many as 90% of bombs could miss their targets.[37][38][39] The average CEP in 1943 was 370 metres (1,200 ft), meaning that only 16% of the bombs fell within 300 metres (1,000 ft) of the aiming point. A 230-kilogram (500 lb) bomb, standard for precision missions after 1943, had a lethal radius of only 18 to 27 metres (60 to 90 ft).
Faced with these poor results, Curtis LeMay started a series of reforms in an effort to address the problems. In particular, he introduced the "combat box" formation in order to provide maximum defensive firepower by densely packing the bombers. As part of this change, he identified the best bombardiers in his command and assigned them to the lead bomber of each box. Instead of every bomber in the box using their Norden individually, the lead bombardiers were the only ones actively using the Norden, and the rest of the box followed in formation and then dropped their bombs when they saw the lead's leaving his aircraft. Although this spread the bombs over the area of the combat box, this could still improve accuracy over individual efforts. It also helped stop a problem where various aircraft, all slaved to their autopilots on the same target, would drift into each other. These changes did improve accuracy, which suggests that much of the problem is attributable to the bombardier. However, precision attacks still proved difficult or impossible.
When Jimmy Doolittle took over command of the 8th Air Force from Ira Eaker in early 1944, precision bombing attempts were dropped. Area bombing, like the RAF efforts, were widely used with 750 and then 1000 bomber raids against large targets. The main targets were railroad marshaling yards (27.4% of the bomb tonnage dropped), airfields (11.6%), oil refineries (9.5%), and military installations (8.8%). To some degree the targets were secondary missions; Doolittle used the bombers as an irresistible target to draw up Luftwaffe fighters into the ever-increasing swarms of Allied long-distance fighters. As these missions broke the Luftwaffe, missions were able to be carried out at lower altitudes or especially in bad weather when the H2X radar could be used. In spite of abandoning precision attacks, accuracy nevertheless improved. By 1945, the 8th was putting up to 60% of its bombs within 300 metres (1,000 ft), a CEP of about 270 metres (900 ft).
Fully automatic bombsight
While the Mk. XI was reaching its final design, the Navy learned of the Army's efforts to develop a synchronous bombsight, and asked Norden to design one for them. Norden was initially unconvinced this was workable, but the Navy persisted and offered him a development contract in June 1929. Norden retreated to his mother's house in Zurich and returned in 1930 with a working prototype. Lieutenant Frederick Entwistle, the Navy's chief of bombsight development, judged it revolutionary.
The new design, the Mark XV, was delivered in production quality in the summer of 1931. In testing it proved to eliminate all of the problems of the earlier Mk. XI design. From 1,200 metres (4,000 ft) altitude the prototype delivered a CEP of 11 metres (35 ft), while even the latest production Mk. XI's were 17 metres (55 ft).[12] At higher altitudes, a series of 80 bomb runs demonstrated a CEP of 23 metres (75 ft).[2] In a test on 7 October 1931, the Mk. XV dropped 50% of its bombs on a static target, the USS Pittsburgh, while a similar aircraft with the Mk. XI had only 20% of its bombs hit.
Moreover, the new system was dramatically simpler to use. After locating the target in the sighting system, the bombardier simply made fine adjustments using two control wheels throughout the bomb run. There was no need for external calculation, lookup tables or pre-run measurements – everything was carried out automatically through an internal wheel-and-disc calculator. The calculator took a short time to settle on a solution, with setups as short as 6 seconds, compared to the 50 needed for the Mk. XI to measure its ground speed.[2] In most cases, the bomb run needed to be only 30 seconds long.
In spite of this success, the design also demonstrated several serious problems. In particular, the gyroscopic platform had to be levelled out before use using several spirit levels, and then checked and repeatedly reset for accuracy. Worse, the gyros had a limited degree of movement, and if the plane banked far enough the gyro would reach its limit and have to be re-set from scratch – something that could happen even due to strong turbulence. If the gyros were found to be off, the levelling procedure took as long as eight minutes. Other minor problems were the direct current electric motors which drove the gyroscopes, whose brushes wore down quickly and left carbon dust throughout the interior of the device, and the positioning of the control knobs, which meant the bombardier could only adjust side-to-side or up-and-down aim at a time, not both. But in spite of all of these problems, the Mark XV was so superior to any other design that the Navy ordered it into production.[15]
Carl L. Norden Company incorporated in 1931, supplying the sights under a dedicated source contract. In effect, the company was owned by the Navy. In 1934 the newly-forming GHQ Air Force, the purchasing arm of the U.S. Army Air Corps, selected the Norden for their bombers as well, referring to it as the M-1. However, due to the dedicated source contract, the Army had to buy the sights from the Navy. This was not only annoying for inter-service rivalry reasons, but the Air Corps' higher-speed bombers demanded several changes to the design, notably the ability to aim the sighting telescope further forward to give the bombardier more time to set up. The Navy was not interested in these changes, and would not promise to work them into the production lines. Worse, Norden's factories were having serious problems keeping up with demand for the Navy alone, and in January 1936, the Navy suspended all shipments to the Army.
Auto Pilot
Mk. XV's were initially installed with the same automatic PDI as the earlier Mk. XI. In practice, it was found that the pilots had a very difficult time keeping the aircraft stable enough to match the accuracy of the bombsight. Starting in 1932 and proceeding in fits and starts for the next six years, Norden developed the Stabilized Bombing Approach Equipment (SBAE), a mechanical autopilot that attached to the bombsight.[17] However, it was not a true "autopilot", in that it could not fly the aircraft by itself. By rotating the bombsight in relationship to the SBAE, the SBAE could account for wind and turbulence and calculate the appropriate directional changes needed to bring the aircraft onto the bomb run far more precisely than a human pilot. The minor adaptations needed on the bombsight itself produced what the Army referred to as the M-4 model.
In 1937 the Army, faced with the continuing supply problems with the Norden, once again turned to Sperry Gyroscope to see if they could come up with a solution. Their earlier models had all proved unreliable, but they had continued working with the designs throughout this period and had addressed many of the problems. By 1937, Orland Esval had introduced a new AC-powered electrical gyroscope that spun at 30,000 RPM, compared to the Norden's 7,200 , which dramatically improved the performance of the inertial platform. The use of three-phase AC power and inductive pickup eliminated the carbon brushes, and further simplified the design. Carl Frische had developed a new system to automatically level the platform, eliminating the time-consuming process needed on the Norden. The two collaborated on a new design, adding a second gyro to handle heading changes, and named the result the Sperry S-1. Existing supplies of Nordens continued to be supplied to the USAAC's B-17s, while the S-1 equipped the B-24Es being sent to the 15th Air Force.
Some B-17s had been equipped with a simple heading-only autopilot, the Sperry A-3. The company had also been working on an all-electronic model, the A-5, which stabilized in all three directions. By the early 1930s, it was being used in a variety of Navy aircraft to excellent reviews. By connecting the outputs of the S-1 bombsight to the A-5 autopilot, Sperry produced a system similar to the M-4/SBAE, but it reacted far more quickly. The combination of the S-1 and A-5 so impressed the Army that on 17 June 1941 they authorized the construction of a 186.000 m² factory and noted that "in the future all production models of bombardment airplanes be equipped with the A-5 Automatic Pilot and have provisions permitting the installation of either the M-Series [Norden] Bombsight or the S-1 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 seemed to promise unprecedented accuracy in day bombing from high altitudes; in peacetime 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 the expected accuracy in combat conditions, with the average CEP in 1943 of 370 metres (1,200 ft) being similar to Allied and German results. 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.
The Norden saw some use in the post-World War II era, especially during the Korean War. Post-war use was greatly reduced due to the introduction of radar-based systems, but the need for accurate daytime attacks kept it in service for some time. The last combat use of the Norden was in the US Navy's VO-67 squadron, which used them to drop sensors onto the Ho Chi Minh Trail as late as 1967. The Norden remains one of the best-known bombsights of all time.
As U.S. participation in the war started, the U.S. Army Air Forces drew up widespread and comprehensive bombing plans based on the Norden. They believed the B-17 had a 1.2% probability of hitting a 30 metres (100 ft) target from 6,100 metres (20,000 ft), meaning that 220 bombers would be needed for a 93% probability of one or more hits. This was not considered a problem, and the AAF forecast the need for 251 combat groups to provide enough bombers to fulfill their comprehensive pre-war plans.
After earlier combat trials proved troublesome, the Norden bombsight and its associated AFCE were used on a wide scale for the first time on the 18 March 1943 mission to Bremen-Vegesack, Germany; The 303d Bombardment Group dropped 76% of its load within a 300 metres (1,000 ft) ring, representing a CEP well under 300 m (1,000 ft) As at sea, many early missions over Europe demonstrated varied results; on wider inspection, only 50% of American bombs fell within a 400 metres (1⁄4 mi) of the target, and American flyers estimated that as many as 90% of bombs could miss their targets.[37][38][39] The average CEP in 1943 was 370 metres (1,200 ft), meaning that only 16% of the bombs fell within 300 metres (1,000 ft) of the aiming point. A 230-kilogram (500 lb) bomb, standard for precision missions after 1943, had a lethal radius of only 18 to 27 metres (60 to 90 ft).
Faced with these poor results, Curtis LeMay started a series of reforms in an effort to address the problems. In particular, he introduced the "combat box" formation in order to provide maximum defensive firepower by densely packing the bombers. As part of this change, he identified the best bombardiers in his command and assigned them to the lead bomber of each box. Instead of every bomber in the box using their Norden individually, the lead bombardiers were the only ones actively using the Norden, and the rest of the box followed in formation and then dropped their bombs when they saw the lead's leaving his aircraft. Although this spread the bombs over the area of the combat box, this could still improve accuracy over individual efforts. It also helped stop a problem where various aircraft, all slaved to their autopilots on the same target, would drift into each other. These changes did improve accuracy, which suggests that much of the problem is attributable to the bombardier. However, precision attacks still proved difficult or impossible.
When Jimmy Doolittle took over command of the 8th Air Force from Ira Eaker in early 1944, precision bombing attempts were dropped. Area bombing, like the RAF efforts, were widely used with 750 and then 1000 bomber raids against large targets. The main targets were railroad marshaling yards (27.4% of the bomb tonnage dropped), airfields (11.6%), oil refineries (9.5%), and military installations (8.8%). To some degree the targets were secondary missions; Doolittle used the bombers as an irresistible target to draw up Luftwaffe fighters into the ever-increasing swarms of Allied long-distance fighters. As these missions broke the Luftwaffe, missions were able to be carried out at lower altitudes or especially in bad weather when the H2X radar could be used. In spite of abandoning precision attacks, accuracy nevertheless improved. By 1945, the 8th was putting up to 60% of its bombs within 300 metres (1,000 ft), a CEP of about 270 metres (900 ft).
Fully automatic bombsight
While the Mk. XI was reaching its final design, the Navy learned of the Army's efforts to develop a synchronous bombsight, and asked Norden to design one for them. Norden was initially unconvinced this was workable, but the Navy persisted and offered him a development contract in June 1929. Norden retreated to his mother's house in Zurich and returned in 1930 with a working prototype. Lieutenant Frederick Entwistle, the Navy's chief of bombsight development, judged it revolutionary.
The new design, the Mark XV, was delivered in production quality in the summer of 1931. In testing it proved to eliminate all of the problems of the earlier Mk. XI design. From 1,200 metres (4,000 ft) altitude the prototype delivered a CEP of 11 metres (35 ft), while even the latest production Mk. XI's were 17 metres (55 ft).[12] At higher altitudes, a series of 80 bomb runs demonstrated a CEP of 23 metres (75 ft).[2] In a test on 7 October 1931, the Mk. XV dropped 50% of its bombs on a static target, the USS Pittsburgh, while a similar aircraft with the Mk. XI had only 20% of its bombs hit.
Moreover, the new system was dramatically simpler to use. After locating the target in the sighting system, the bombardier simply made fine adjustments using two control wheels throughout the bomb run. There was no need for external calculation, lookup tables or pre-run measurements – everything was carried out automatically through an internal wheel-and-disc calculator. The calculator took a short time to settle on a solution, with setups as short as 6 seconds, compared to the 50 needed for the Mk. XI to measure its ground speed.[2] In most cases, the bomb run needed to be only 30 seconds long.
In spite of this success, the design also demonstrated several serious problems. In particular, the gyroscopic platform had to be levelled out before use using several spirit levels, and then checked and repeatedly reset for accuracy. Worse, the gyros had a limited degree of movement, and if the plane banked far enough the gyro would reach its limit and have to be re-set from scratch – something that could happen even due to strong turbulence. If the gyros were found to be off, the levelling procedure took as long as eight minutes. Other minor problems were the direct current electric motors which drove the gyroscopes, whose brushes wore down quickly and left carbon dust throughout the interior of the device, and the positioning of the control knobs, which meant the bombardier could only adjust side-to-side or up-and-down aim at a time, not both. But in spite of all of these problems, the Mark XV was so superior to any other design that the Navy ordered it into production.[15]
Carl L. Norden Company incorporated in 1931, supplying the sights under a dedicated source contract. In effect, the company was owned by the Navy. In 1934 the newly-forming GHQ Air Force, the purchasing arm of the U.S. Army Air Corps, selected the Norden for their bombers as well, referring to it as the M-1. However, due to the dedicated source contract, the Army had to buy the sights from the Navy. This was not only annoying for inter-service rivalry reasons, but the Air Corps' higher-speed bombers demanded several changes to the design, notably the ability to aim the sighting telescope further forward to give the bombardier more time to set up. The Navy was not interested in these changes, and would not promise to work them into the production lines. Worse, Norden's factories were having serious problems keeping up with demand for the Navy alone, and in January 1936, the Navy suspended all shipments to the Army.
Auto Pilot
Mk. XV's were initially installed with the same automatic PDI as the earlier Mk. XI. In practice, it was found that the pilots had a very difficult time keeping the aircraft stable enough to match the accuracy of the bombsight. Starting in 1932 and proceeding in fits and starts for the next six years, Norden developed the Stabilized Bombing Approach Equipment (SBAE), a mechanical autopilot that attached to the bombsight.[17] However, it was not a true "autopilot", in that it could not fly the aircraft by itself. By rotating the bombsight in relationship to the SBAE, the SBAE could account for wind and turbulence and calculate the appropriate directional changes needed to bring the aircraft onto the bomb run far more precisely than a human pilot. The minor adaptations needed on the bombsight itself produced what the Army referred to as the M-4 model.
In 1937 the Army, faced with the continuing supply problems with the Norden, once again turned to Sperry Gyroscope to see if they could come up with a solution. Their earlier models had all proved unreliable, but they had continued working with the designs throughout this period and had addressed many of the problems. By 1937, Orland Esval had introduced a new AC-powered electrical gyroscope that spun at 30,000 RPM, compared to the Norden's 7,200 , which dramatically improved the performance of the inertial platform. The use of three-phase AC power and inductive pickup eliminated the carbon brushes, and further simplified the design. Carl Frische had developed a new system to automatically level the platform, eliminating the time-consuming process needed on the Norden. The two collaborated on a new design, adding a second gyro to handle heading changes, and named the result the Sperry S-1. Existing supplies of Nordens continued to be supplied to the USAAC's B-17s, while the S-1 equipped the B-24Es being sent to the 15th Air Force.
Some B-17s had been equipped with a simple heading-only autopilot, the Sperry A-3. The company had also been working on an all-electronic model, the A-5, which stabilized in all three directions. By the early 1930s, it was being used in a variety of Navy aircraft to excellent reviews. By connecting the outputs of the S-1 bombsight to the A-5 autopilot, Sperry produced a system similar to the M-4/SBAE, but it reacted far more quickly. The combination of the S-1 and A-5 so impressed the Army that on 17 June 1941 they authorized the construction of a 186.000 m² factory and noted that "in the future all production models of bombardment airplanes be equipped with the A-5 Automatic Pilot and have provisions permitting the installation of either the M-Series [Norden] Bombsight or the S-1 Bombsight.
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