The system uses color to signal levels: green means normal, yellow (amber) signals a cautionary, low level, and red indicates a critical condition. When fuel quantity falls below the pre-set threshold, the left and right indicators turn yellow to warn the crew that fuel is below the desired level and needs attention. This remains yellow until a more severe condition (below minimum/critical) would trigger a red alert. So, below the threshold, yellow is the correct color because it marks a warning status, not an immediate emergency.

When the collector tank runs dry, fuel will flow from the wing tanks into it by gravity. The wing tanks are at a higher elevation and are connected to the collector tank through fuel lines, so with the collector empty there’s a downward pressure head that causes remaining fuel in the wing tanks to drain into the collector without needing pumps. This keeps the collector supplied so fuel can continue to be drawn from it as needed. The other options don’t fit because there is a natural gravity-driven flow path between the tanks, not a halt in movement, not pumping fuel into the wings, and not air alone entering the collector.

The main idea here is how the Power Management Unit (PMU) controls and protects the engine. The PMU’s job is to translate the pilot’s power request into a safe, usable power level while keeping the engine and propeller operating within their limits. It shapes the response so that as you move the power control from idle toward maximum, the engine responds in a nearly linear and predictable way. It also monitors important parameters to ensure operation stays within prescribed bounds, including factors like fuel state to maintain safe operation. What the PMU does not do is fine‑tune the power request or directly send an electronic signal to the Fuel Metering Unit. Fine tuning the power and managing precise fuel metering are responsibilities of the engine control system (the FADEC/ECU) which then drives the Fuel Management Unit (FMU) to meter fuel accordingly. So the PMU provides protection and a smooth, linear mapping from pilot input to available power, while the actual metering and final power adjustment are handled by the engine control system.

The engine-driven generator is the primary source of electrical power because it provides continuous, normal-power to all aircraft systems while the engines are running and also keeps the batteries charged. Batteries serve as energy storage for starting and as backups during electrical faults, but they cannot supply sustained power for the whole system. The auxiliary battery offers an additional backup to critical loads in certain configurations, ensuring essential equipment can operate if the main power source drops. So, in routine flight, the generator supplies the bulk of electrical power, with the batteries stepping in only for starting or emergency use.