What type of fuel quantity system accurately determines the weight of fuel in an aircraft's tanks?

The capacitor-type fuel quantity system accurately determines the weight of fuel in an aircraft's tanks because it measures the capacitance change caused by the presence of fuel. In this system, capacitive probes placed in the fuel tank measure the dielectric constant of the fuel, which varies depending on how much fuel is present. The change in capacitance correlates to the amount of fuel, allowing for a precise measurement of fuel quantity.

This method is particularly beneficial because it can provide fuel weight directly, especially when combined with temperature compensation and specifics about the fuel type, ensuring that the readings are consistent regardless of fuel density variations. The system is also less prone to inaccuracies that can occur due to fuel turbulence or position when compared to other measurement methods.

Other systems, like mechanical float systems, while effective in indicating fuel levels, do not provide as accurate a measurement of weight because they rely on float buoyancy, which is influenced by fuel density changes. Magnetic gauge systems primarily measure fuel level through magnetic floats and similarly don't provide direct weight measurements, while ultrasonic systems use sound waves to gauge fuel levels but may not account for variations in fuel density accurately. These limitations make the capacitor-type system the most suitable choice for determining the weight of fuel in aircraft.