What is the N_1 percentage in flight at idle?

The N_1 percentage in flight at idle for the T-6A is indeed 67%. This value is crucial for operating within the engine's parameters, as it reflects the engine's performance at idle power settings during flight.

Operating at the correct N_1 percentage ensures that the engine operates efficiently and allows for a controlled descent or glide, especially in scenarios such as reduced power settings for landing. In essence, maintaining the N_1 at idle within this specified limit prevents potential engine stall or uncommanded power loss, which is critical for safety.

The other percentages provided do not correspond with the T-6A's operating limits for N_1 at idle, meaning they would not provide the necessary engine performance required for safe flying conditions. Thus, knowing that 67% is the ideal and safe operational limit greatly aids in effective flight training and real-time decision-making in the cockpit.