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Transponder
An electronic device in the aircraft that transmits a coded signal when interrogated by ground radar. Mode C transponders report altitude. Mode S transponders support ADS-B Out, which is required in most controlled airspace.
Related Terms
- VASI (Visual Approach Slope Indicator)A visual glide-path aid that uses red and white light bars beside the runway to help pilots maintain a safe approach angle. A disabled VASI is a common NOTAM item that can change night or VFR approach planning.
- VFR (Visual Flight Rules)A set of regulations under which a pilot operates an aircraft by visual reference to the ground and specific visibility and cloud clearance requirements. VFR flight is the standard for private pilots and does not require an instrument rating.
- Vmc (Minimum Control Speed)The minimum speed at which an aircraft can maintain directional control with one engine inoperative, the other at takeoff power, and specific configurations. Vmc is a critical concept in multi-engine training and marked with a red radial line on the airspeed indicator.
- VOR (VHF Omnidirectional Range)A ground-based radio navigation aid that transmits VHF signals in 360 radials, allowing pilots to determine their magnetic bearing to or from the station. VORs are used for en route navigation and many instrument approach procedures.