cone of confusion

i. An inverted cone of airspace with its vertical axis centered on the VOR (very high frequency omnidirectional radio range) or another point navigational aid. As the aircraft moves closer to the VOR transmitting station, the VOR indicator needle becomes very sensitive and oscillates from side to side (i.e., the pointer acts in an unstable manner). The time an aircraft remains in the cone depends on its speed and altitude. Once the aircraft moves out from the confusion zone, all erratic indications cease.

ii. Another form of the cone of confusion is caused by reception of VOR (very high frequency omnidirectional radio range) signals from more than one station simultaneously. Normally, stations on the same frequency are spaced to avoid interference. However, with the increased density of installations, it is possible, at certain locations and altitudes, to receive two stations with approximately equal strength. The cone of confusion can be recognized by oscillation of instrument panel indicators and an aural whistle. The cone can be eliminated by selecting different stations along the route. Also called an area of confusion.

iii. A term used to describe the area near a VOR ground station.