Which equipment is required for RVSM operations to report altitude?

• A. Altitude reporting transponder
• B. Two independent altimeters
• C. Altitude alert system
• D. Automatic altitude control system

Answer: (A)

In RVSM operations, the key requirement for letting ATC know your precise altitude is the altitude reporting transponder. This device encodes the aircraft’s current barometric altitude and transmits it to ATC (typically via Mode C or Mode S), enabling radar displays to reflect your exact flight level. Without a functioning altitude reporting transponder, ATC cannot reliably see your altitude even if you have accurate altimeters. While having two independent altimeters is also essential in RVSM for accurate and redundant altitude measurement, the equipment that actually reports altitude to ATC is the altitude reporting transponder. The altitude alert system and automatic altitude control system serve other safety and operational roles and are not the primary means of reporting altitude to ATC.