In an airspace with reduced vertical separation minima (RVSM), what is the upper limit for altitude deviation alerting equipment?

In an airspace with reduced vertical separation minima (RVSM), the upper limit for altitude deviation alerting equipment is established to ensure the safety and integrity of aircraft operating at these reduced vertical separations. The correct answer, which states that the limit is ± 90 m (± 300 ft), aligns with the guidelines set forth by aviation regulatory bodies regarding altitude monitoring and alerting systems in RVSM airspace.

This tolerance level is critical because RVSM allows aircraft to operate with only 1,000 feet of vertical separation between them, compared to the standard 2,000 feet in non-RVSM airspace. As such, it becomes vital to have robust systems in place to monitor and alert pilots to any deviations from their assigned altitude. The ± 90 m (± 300 ft) requirement ensures that any potential altitude deviations are detected promptly, allowing for the necessary corrective actions to be taken in a timely manner to prevent any potential conflicts between aircraft.

The other options present larger tolerances than what is permissible in RVSM airspace. The requirement for a ± 90 m deviation alerting is specifically intended to maintain safety and prevent inadvertent altitude encroachments that could lead to midair collisions.