Airplane fuel gauges are somewhat similar to vehicle fuel gauges in that they both indicate the quantity of usable fuel present in the fuel tank. However, airplane fuel gauges work at a more complex level simply because aircraft carry more than one fuel tank and they also have more than one engine. Besides, reading fuel levels becomes complicated due to the fluctuating fuel density resulting from the changing aircraft altitudes.
To explain the workings of an airplane fuel gauge in a simplistic manner: a float level gauge is fitted to each of the fuel tanks in the aircraft. These gauges feed the information pertaining to fuel level in each tank to magnetic couplings and potentiometers which in turn pass on the information to the aircraft fuel gauge. However, the sloshing liquid with fluctuating density in multiple tanks make the work of airplane fuel gauges quite complicated. Modern aircraft technology however, has been able to achieve an advanced level of accuracy in the complicated world of aircraft fuel level reading.
Basically, there are three types of airplane fuel gauges that are used in aircrafts of today, namely,
1) mechanical airplane fuel gauge
2) electric airplane fuel gauge, and,
3) digital airplane fuel gauge, which is the choice for the latest model of airplanes.
The Mechanical Airplane Fuel Gauge is fitted with a cork which is attached to a lightweight aluminium pipe. The cork goes up or down with the fuel level. The pipe is attached to a stainless steal gear system which converts the motion of the cork into a circular movement showing “full” or “empty” indication of the fuel tank. The mechanical fuel gauge is a simple device found in the old aircraft models. The disadvantage of mechanical fuel gauges is that there are too many moving parts that can get stuck or jam up due to the aircraft’s movement and vibration.
Electrical Airplane Fuel Gauge is also known as capacitance meter and uses a capacitor, an electrical amplifier and a fuel gauge to give a reading of Aircraft Fuel Flow Indicator in the tanks. The capacitor stores an electric charge, the size of the dielectric which is either the fuel in the tank when full or the air in the tank when it’s empty. The fuel gauge in the cockpit of the aircraft reads the capacitance charge and displays the information.
The Digital Airplane Fuel Gauge is the latest technology being used to calculate the level of fuel in the airplane’s tanks. When the aircraft is fuelled up for a flight, the pilot enters the quantity in each tank via a touch screen on the Digital Aircraft Fuel Flow Monitors. The flow rate of the aviation fuel through the outlet pipe is accurately measured and the onboard computer in the plane’s electronic management system calculates the quantity of fuel remaining in each of the tanks and displays it in digital form or bar graphs. Based on the consumption of fuel and the quantity left in the tanks, the aircraft’s electronic management system can calculate whether the plane has sufficient fuel to reach its destination.