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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
- Urgent PIREP (UUA)A pilot weather report marked urgent rather than routine (UA). UUA reports highlight conditions that need immediate dissemination, such as severe or extreme turbulence, severe icing, hail, volcanic ash, or other hazards that can rapidly affect flight safety. Student pilots should treat UUA details as high-priority briefing inputs.
- 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.
- View-Limiting DeviceA hood, foggles, or similar device that blocks outside visual references so a pilot must fly by instruments. Instrument trainees wear a view-limiting device during most dual simulated-instrument lessons to build scan, attitude control, and approach skills.