A pilot direction indicator or pilot's directional indicator (PDI), Smithsonian Institution is an aircraft instrument used by bombardiers to indicate heading changes to the pilot in order to direct them to the proper location to drop

bomb A bomb is an explosive weapon that uses the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-transmitted mechan ...

s. The PDI is used in aircraft where the pilot and bombardier are physically separated and cannot easily see each other. PDI's typically consist of a dial that is installed in the pilot's instrument set on the main console, with an arrow pointer than can be moved to indicate how far and in what direction to correct the heading. The bombardier typically has a switch to move the pointer to the right or left, and a repeater dial so he can see the setting. The

Norden bombsight The Norden Mk. XV, known as the Norden M series in U.S. Army service, is a bombsight that was 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 an ...

was originally designed with the idea of automatically directing a PDI and thereby simplifying the bombardier's task.

References

Aircraft instruments Measuring instruments {{Component-aircraft-stub