True or False: The illumination of the BAT BUS annunciator during engine start is normal.

During engine start in the T-6A, the illumination of the BAT BUS annunciator is not considered normal. The BAT BUS annunciator alerts the pilot to the fact that there is an issue with the battery bus, which is crucial for powering essential systems when the engine is not yet running. During an engine start sequence, while there are fluctuations in electrical demand that might temporarily cause some system lights to flicker or illuminate, the BAT BUS should remain off once the battery is functioning correctly and the engine is transitioning to start.

If the BAT BUS annunciator lights up, it indicates that the battery is not providing adequate power or that there is a fault in the system. Therefore, the correct response is that it is false to say that the illumination of the BAT BUS annunciator during engine start is normal. Understanding this distinction is important for the pilot in ensuring the aircraft's systems are functioning properly.