Under what conditions will the H-PBIT start automatically?

The H-PBIT, or Health Built-In Test, is designed to automatically initiate under specific conditions to ensure that the aircraft's systems are functioning correctly. In this case, the correct condition for the H-PBIT to start automatically is when all three systems are pressurized.

When all three systems—essentially meaning the aircraft's critical hydraulic systems—are adequately pressurized, it signifies that the necessary resources for system checks are available. This is crucial as it allows the H-PBIT to effectively evaluate the health of the systems without interruption.

The other conditions listed do not align with the requirements for initiating the H-PBIT. Moving flight controls might indicate a desire to test system responsiveness but does not provide the necessary stable environment for a thorough assessment. Gear extension occurs as part of landing procedures and does not inherently require a systems check, while reducing engine power may influence flight dynamics but does not affect the operational readiness of the H-PBIT itself. Thus, the activation of H-PBIT is contingent upon ensuring that all systems are ready and pressurized to carry out the diagnostic functions effectively.