Almost all air forces adopted some variation of the CSBS as their standard inter-war bomb sight, including the U.S. Navy, who used a modified version known as the Mark III.

[6] Norden suggested that the only solution to improve accuracy would be to directly measure the ground speed, as opposed to calculating it using the CSBS's wind triangle.

[3] In December 1927, the United States Department of War was granted permission to use a bridge over the Pee Dee River in North Carolina for target practice, as it would soon be sunk in the waters of a new dam.

[7] The Army turned its attention to further upgraded versions of their existing prototypes, replacing the older vector bombsight mechanisms with the new synchronous method of measuring the proper dropping angle.

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.

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.

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.

They wrote to George Pirie, the British air attaché in Washington, suggesting he approach the U.S. Army with an offer of an information exchange with their own SABS.

The matter was not helped by a minor diplomatic issue that flared up in July when a French air observer was found to be on board a crashed Douglas Aircraft Company bomber, forcing President Roosevelt to promise no further information exchanges with foreign powers.

[22] The RAF's desires were only further goaded on 13 April 1939, when Pirie was invited to watch an air demonstration at Fort Benning where the painted outline of a battleship was the target: At 1:27 while everyone was still searching [the sky for the B-17s] six 300-pound (140 kg) bombs suddenly burst at split second intervals on the deck of the battleship, and it was at least 30 seconds later before someone spotted the B-17 at 12,000 feet (3,700 m)[23]The three following B-17s also hit the target, and then a flight of a dozen Douglas B-18 Bolos placed most of their bombs in a separate 550 m × 550 m (600 yd × 600 yd) square outlined on the ground.

[23] Another change of management within the Bureau of Aeronautics had the effect of making the U.S. Navy more friendly to British overtures, but no one was willing to fight the political battle needed to release the design.

The Navy brass was concerned that giving the Norden to the RAF would increase its chances of falling into German hands, which could put the U.S.'s own fleet at risk.

When a report stated that the Norden's results were three to four times as good as their own bombsights, the Air Ministry decided to sweeten the pot and suggested they offer information on radar in exchange.

[24] The matter eventually worked its way to the Prime Minister, Neville Chamberlain, who wrote personally to President Roosevelt asking for the Norden, but even this was rejected.

This drove both the British Air Ministry and Royal Navy to increasingly anti-American attitudes when they considered sharing their own developments, notably newer ASDIC systems.

[24] Looking for ways around the deadlock, Henry Tizard sent Archibald Vivian Hill to the U.S. to take a survey of U.S. technical capability in order to better assess what technologies the U.S. would be willing to exchange.

[25] Ironically, by the time the Mission was being planned, the Norden had been removed from the list of items to be discussed, and Roosevelt personally noted this was due largely to political reasons.

It was not until 1942 that the impasse was finally solved by farming out autopilot production to Honeywell Regulator, who combined features of the Norden-mounted SBAE with the aircraft-mounted A-5 to produce what the U.S. Army referred to as "Automatic Flight Control Equipment" (AFCE);[19] the unit would later be redesigned as the C-1.

The USAAF demanded additional production to meet their needs, and eventually arranged for the Victor Adding Machine company to gain a manufacturing license, and then Remington Rand.

A separate section of the calculator used the inputs for altitude and airspeed to determine the angular velocity of the target, the speed at which it would be seen drifting backward due to the forward motion of the aircraft.

Over a short period of time of continual adjustments, the drift would stop, and the bombsight would now hold an extremely accurate measurement of the exact ground speed and heading.

Some versions included a system that quickly righted the platform, but this "Automatic Gyro Leveling Device" proved to be a maintenance problem, and was removed from later examples.

The Army felt the combination of the Norden and B-17 Flying Fortress presented an alternate solution, believing that small formations of B-17s could successfully attack shipping at long distances from the USAAC's widespread bases.

After the device became known about publicly in 1942, the Norden company in 1943 rented Madison Square Garden and folded their own show in between the presentations of the Ringling Bros. and Barnum & Bailey Circus.

[29] The Grumman TBF Avenger could mount the Norden, like the preceding Douglas TBD Devastator,[32] but combat use was disappointing and eventually described as "hopeless" during the Guadalcanal Campaign.

[29] 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.

C. Ross Greening, the sight was mounted to the existing pilot direction indicator, allowing the bombardier to make corrections remotely, like the bombsights of an earlier era.

The bombsights were used in Operation Igloo White for implanting Air-Delivered Seismic Intrusion Detectors (ADSID) along the Ho Chi Minh Trail.

[46] 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.

The Douglas TBD Devastator torpedo bomber was originally equipped with flotation bags in the wings to aid the aircrew's escape after ditching, but they were removed once the Pacific War began; this ensured that the aircraft would sink, taking the Norden with it.