What altitude must crews maintain if the Vance Altimeter is below 29.92 when using the high block?

When flying the T-6A using the high block, there are specific altitude requirements that crews must adhere to, especially when the altimeter setting is below 29.92 inches of mercury. The correct altitude to maintain in this scenario is 20,000 feet mean sea level (MSL).

This regulation is in place to ensure safe vertical separation from other aircraft when the altimeter is set to a pressure that is lower than the standard atmospheric pressure (29.92 inHg). If the Vance Altimeter is below this threshold, it decreases the aircraft's indicated altitude, which can lead to potential conflicts in airspace if not correctly adjusted for the altitude differences.

By maintaining an altitude of 20,000 feet MSL in this context, it helps ensure that vertical separation from other air traffic is preserved, thus enhancing safety and compliance with airspace management protocols. The regulations are specifically structured to mitigate risks associated with altitude deviations caused by varying atmospheric pressure conditions.