Editing Avionics (section)

===Collision-avoidance systems===

{{Main|Aircraft collision avoidance systems}}
To supplement [[air traffic control]], most large transport aircraft and many smaller ones use a [[TCAS|traffic alert and collision avoidance system]] (TCAS), which can detect the location of nearby aircraft, and provide instructions for avoiding a midair collision. Smaller aircraft may use simpler traffic alerting systems such as TPAS, which are passive (they do not actively interrogate the [[transponder]]s of other aircraft) and do not provide advisories for conflict resolution.

To help avoid controlled flight into terrain ([[CFIT]]), aircraft use systems such as [[GPWS|ground-proximity warning systems]] (GPWS), which use radar altimeters as a key element. One of the major weaknesses of GPWS is the lack of "look-ahead" information, because it only provides altitude above terrain "look-down". In order to overcome this weakness, modern aircraft use a terrain awareness warning system ([[TAWS]]).