At what percent N1 does the PMU deactivate the igniters and boost pump, assuming fuel pressure is adequate?

The correct answer is based on the operational parameters of the T-6A aircraft's Power Management Unit (PMU). The PMU is responsible for managing engine performance and ensuring optimal operation during various phases of flight.

When the engine reaches approximately 50% N1, the PMU deactivates the igniters and the boost pump, provided that the fuel pressure is adequate. This is a critical function because at this percentage of N1, the engine is usually operating within stable parameters where a continuous spark from the igniters is no longer necessary to maintain combustion, and the boost pump, which facilitates fuel delivery at lower engine speeds, is also not required at this stage.

This design improves efficiency and reduces unnecessary wear on components. The decision to deactivate these systems at 50% N1 balances safety considerations while also enhancing operational efficiency during flight.