Norden takes up the challenge

Carl L. Norden began studying bombing problems in 1921 as a consultant to the U.S. Navy. He had been a Navy consultant on different projects since 1915. For the four years before that, he was an engineer working on ship gyrostabilizers with the newly formed Sperry Gyroscope Co., and continued as a consultant to Sperry through World War I.    

In 1923, Norden went into partnership with another Navy consultant, a former Army colonel named Theodore H. Barth, who provided valuable know-how in sales. Over the next five years, Norden designed bombsights, and Barth built and tested prototypes from Norden's top secret drawings. In 1928, Norden and Barth received their first order from the Navy for 40 bombsights. At that point the two incorporated as Car! L. Norden Inc.     

The Norden company delivered its first prototype of its Mark XV bombsight to the Navy in 1931. To make the bombsight's telescope independent of the buffeting of  the plane, it was hung from gimbals (ring-shaped bearings that allowed the telescope to point in any direction and remain level when the plane banked). Inside the sight were two dc-powered gyroscopes one for vertical orientation and one for azimuth reference. Both spun at 7800 revolutions per minute. Through an electromechanical servo mechanism similar to those that operated ship stabilizers, the azimuth gyro steadied the bombsight optics in the horizontal plane so the crosshairs could be synchronized with the plane's approach.    

The Norden design had at least four significant problems. First, the carbon dc brushes wore out and had to be replaced frequently; moreover, carbon dust from the wearing brushes would settle into the sensitive gimbal bearings, increasing friction, and necessitating the repeated cleaning and oiling of the precision bearings.  

Second, accurate leveling of the vertical gyro was a tricky procedure' especially in rough air, as it required manual setting of two liquid levels like the bubble in a carpenter's level. The process took 510 seconds, a significant fraction of the bombing run.

Third, both the azimuth and range operating knobs were on the righthand side of the bombsight, making simultaneous two-hand sighting on a target almost impossible.

Fourth, the angular freedom of the vertical gyro was such that in rough air the gyro would hit the limits and tumble off its axis of rotation, losing the bombing run.

In spite of the Norden bombsight's imperfections, it performed so much better than any other sight available in the early 1930s that it was quickly adopted by the Navy for all its bombers. Furthermore, the Navy designated Carl L. Norden Inc. as a dedicated source‹meaning the Navy purchased bombsights exclusively from Norden, and Norden supplied bombsights only to the Navy. In effect, this made the Norden company a manufacturing arm of the Navy under the Norden name.

Meanwhile, Sperry Gyroscope Co., which had been founded by Elmer Sperry in 1909, had begun designing and building bombsights as a natural outgrowth of its development of gyroscopes for commercial and military aircraft and ships. As early as 1914, when Norden had been on the payroll for three years, Sperry's company had built and was granted a patent for a vertically stabilized bombsight that relied on a vertical gyro assembly driven with dc power. The company went on to develop improved models of this first synchronized sight in 1915, 1918, 1924, 1927, 1929, 1930, and 1933, culminating in a model called the Sperry O-1. But as in the Norden sight, the Sperry gyros had significant problems. Moreover, there was no market for the Sperry bombsights until the Army began having procurement problems with the Norden company in 1936.