Autoland in modern aircraft, the electrical supply includes which arrangement?

• A. 2 independent AC and a DC supply
• B. 2 independent DC and a AC supply
• C. 3 independent AC and a DC supply
• D. One combined supply

Answer: (A)

Autoland relies on highly redundant electrical power to keep the flight control system and autopilot operating through the approach and landing. The essential setup uses two independent AC sources, typically from different generators (one from each engine or an APU), to feed the essential AC buses that power the avionics and control actuators. Having two separate AC paths means that if one source fails, the other can continue to supply power, preserving control and guidance during the critical approach phase.

A separate DC supply backs up the system, powering the essential DC bus and, when needed, allowing an inverter to produce AC power for components that must stay alive even if the AC system dips. This combination—two independent AC sources for redundancy plus a DC supply for backup power—provides the reliability autoland requires.

Lack of redundancy (one combined supply) would risk losing critical capability if power drops, and relying on three independent AC sources or on DC-only power would either add unnecessary complexity or fail to support all flight-control loads that depend on AC power.