Which altitude measurement systems are necessary for RVSM compliance?

For Reduced Vertical Separation Minimum (RVSM) compliance, the necessary altitude measurement systems include two independent systems that are equipped with ice protection. This requirement ensures redundancy and reliability in altitude reporting, which is crucial for maintaining safe vertical separation between aircraft operating at higher altitudes, typically between FL290 and FL410.

The rationale behind requiring two independent systems is to safeguard against the failure of any single system, which could compromise altitude accuracy. Ice protection is important because altitude sensors can be affected by icing conditions, which may distort readings and lead to dangerous situations such as loss of vertical separation.

Having two systems allows for cross-checking of altitude information, which increases safety in a crowded airspace, ensuring accurate communication of altitude between pilots and air traffic control. This dual-system requirement is a standard practice in aviation regulations to maintain operational integrity and safety during RVSM operations.