How does a fuel quantity gauge operate in an aircraft?

The operation of a fuel quantity gauge in an aircraft relates to accurately determining the amount of fuel available for use. The correct choice describes two primary methods used to measure the fuel level in the tanks: using a float or capacitance measurement.

In the float method, a buoyant device rises and falls with the fuel level in the tank. As the fuel level changes, so does the position of the float, which is connected to a mechanical or electrical sensor that translates the float's position into an indication of fuel quantity.

The capacitance method works by measuring the capacitance between probes placed at various levels in the fuel tank. As the fuel level rises or falls, the dielectric constant of the medium between the probes changes, which alters the capacitance. The onboard system interprets these changes to display the fuel level.

Both methods provide a reliable means for pilots and maintenance crews to monitor fuel levels, ensuring safety and operational efficiency by preventing fuel exhaustion during flight.

Understanding these concepts is crucial for grasping how aircraft manage their fuel resources, which directly impacts flight planning and performance.