What should be considered inop when the EHYD PX LO annunciator illuminates?

When the EHYD PX LO annunciator illuminates, it indicates low hydraulic pressure in the emergency hydraulic system. This low pressure affects critical systems that rely on hydraulic power, specifically the emergency landing gear and flap extension system.

In the T-6A, the emergency hydraulic system serves as a backup to the main hydraulic system for landing gear and flaps. When hydraulic pressure in this system is insufficient, these systems may not operate reliably or at all. Consequently, pilots must treat the emergency landing gear and flap extension system as inoperative to ensure safety, as landing gear may not deploy and flaps may not extend as needed during landing operations.

By recognizing that both the emergency landing gear and flap extension system are contingent upon adequate hydraulic pressure, it becomes clear why this option is the correct choice in response to the EHYD PX LO indication.