Bombsight, Pilot-Directing, Mark III

The Bombsight, Pilot-Directing, Mark III was an inter-war era bombsight developed by the US Navy to equip its bomber aircraft. It was a development of the British Course Setting Bomb Sight, or CSBS, which had been introduced in UK service in early 1918 and was demonstrated to the Navy in Washington in May 1918. As the primary bombers in Navy service at the time were flying boats where the pilot and bombardier were separated, Mark III's primary change was to include an electrically driven pilot direction indicator.

The Mark III was the standard Navy bombsight in the interwar period, from late 1918 until its complete replacement just before the opening of World War II. The Navy was never particularly happy with it, as it lacked the accuracy to hit a ship from higher altitudes and had no way to directly account for moving targets. The Navy continued to look for ways to improve it through this period, but none of the advances were enough to justify the production of a new model.

One of these improvements was to ask Carl Norden to stabilize the system to ease sighting, but this proved to be only a minor advance. Norden continued to consider the problem and this led to the development of the Norden bombsight, or Mark XV, which began to replace the Mark III on new aircraft starting in 1935.