FAA Flight Instructor Airplane (FIA)Navigation and AirspaceMedium
A pilot planning to overfly a major Class B airport at 8,000 feet MSL, remaining 25 NM laterally from the primary airport, asks a CFI about transponder requirements. The CFI correctly explains that this flight is within the Mode C veil and therefore requires:
- Aa transponder only if the aircraft descends below 10,000 feet MSL
- Btwo-way radio communication with ATC only, transponder not required
- Cno transponder, since the aircraft will remain outside the Class B boundaries
- Dan operating transponder with altitude reporting capability, regardless of whether the flight enters Class B airspace
Show answer & explanationAnswer & explanation
Correct answer: D. an operating transponder with altitude reporting capability, regardless of whether the flight enters Class B airspace
14 CFR 91.215 requires an operating Mode C transponder within 30 NM of a Class B primary airport (the 'Mode C veil') from the surface up to 10,000 feet MSL, even if the aircraft never enters the Class B airspace itself.
Why the other options are wrong
- A. Altitude reporting is required throughout the veil, not just below a certain altitude.
- B. Radio communication alone does not satisfy the transponder/altitude-reporting requirement.
- C. Being outside Class B boundaries does not exempt aircraft within the 30 NM Mode C veil.
Mode C Veil
Airspace within 30 NM of a Class B primary airport, from the surface up to 10,000 ft MSL, where an operating Mode C transponder is required under 91.215, regardless of entry into Class B.
- Applies even if not entering the Class B airspace.
- Extends from surface to 10,000 ft MSL.
- Exceptions exist for aircraft not originally certificated with an electrical system.
Memory trick: 'Thirty miles, ten thousand feet — the veil sees your altitude.'