Autoland systems rely on how many independent power supplies to maintain operations?

• A. Two
• B. Three
• C. Four
• D. Five

Answer: (B)

Redundancy in the autoland power supply is what keeps the system alive during failures. Autoland must function through the approach and landing even if part of the aircraft’s electrical system fails, so it uses three independent power sources. This arrangement ensures that if one source or its distribution path fails, two other isolated sources can still power the flight-control computers, guidance, and actuators needed for a safe landing. Typically the three come from the main electrical system, a standby/essential power source, and a separate backup such as an APU generator or a dedicated independent power unit. With only two sources, a single fault could leave the autoland without power; four or five sources would exceed what's required for standard autoland reliability.