Norden bombsight

The Norden bombsight was a U.S. aiming device intended for use from horizontal bombers. Its effectiveness varied both with the skill of the bombardier and the conditions of use. While, under good conditions, it was a significant improvement over previous devices, it did not come close to the accuracy of more modern aiming systems with digital electronics, and, of course no combination of "dumb bombs" and bombsight could maintain the continuous correction of precision guided munitions.

To compare it to present technology, today, one can speak of the number of targets that can be accurately attacked in one sortie, or one flight of one page. In a recent test, a B-2 Spirit aircraft released 80 independent Joint Direct Action Munition guidance kits, on Mk. 82 500 lb. bombs in one 2-second opening of the bomb doors; the crew, with 160 more bombs to deliver, disliked holding the doors open because that interfered with their stealth capability. That version of the weapon, which has improved, generally could hit within 10 feet of their target; the targets, depending on the altitude of the aircraft, could be a radius of 15 miles or so.

In contrast, on the Schweinfurt raid in October 1943, the Eighth Air force sent a force of over 250 B-17s. Using Norden bombsights, only one of every 10 of their bombs landed within 500 feet of their target. Even though 60 bombers were lost, the target was not destroyed. <ref name=USAFM-Nordem>{{citation|

title = Norden M-9 Bombsight
| url = http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=8056
| journal = Museum of the United States Air Force) 

It was considered extremely secret, to the extent of having a special oath for its operators:

Mindful of the secret trust about to be placed in me by my Commander in Chief, the President of the United States, by whose direction I have been chosen for bombardier training... and mindful of the fact that I am to become guardian of one of my country's most priceless military assets, the American bombsight... I do here, in the presence of Almighty God, swear by the Bombardier's Code of Honor to keep inviolate the secrecy of any and all confidential information revealed to me, and further to uphold the honor and integrity of the Army Air Forces, if need be, with my life itself.

— The Bombardier's Oath

<ref name=CenFliNord>}U.S. Centennial of Flight Commission, Norden Bombsight

Ironically, the Germans had detailed plans but had no great use for them, preferring dive bombing over horizontal bombing whenever possible.

The technology was essentially that of a purpose-built electromechanical analog computer, using gyroscopes for stabilization.