Advantages & Disadvantages of Resistive Type Fuel Systems
Advantages of Resistive Type Fuel Measurement Systems
The primary advantage of this type of system is cost. The components are very simple and therefore very inexpensive to manufacture. A second advantage is reliability. Again these are very simple components involving very few piece parts to manufacture; the fewer parts that are involved then the less that can go wrong. The third and final advantage is that the system, while not optimal, does provide a reasonable amount of accuracy. When utilized on a small aircraft, carrying small quantities of fuel with a limited flight range the accuracy that is provided by this system is adequate.
Disadvantages of Resistive Type Fuel Quantity Systems
Inaccuracy due to Physics
The fuel, within the aircraft’s tanks, is subject to the laws of physics. Therefore it moves when the aircraft moves. It is affected by gravity and centrifugal force. When the aircraft banks for a turn the fuel slops to one side. When the aircraft climbs the fuel flows to the back of the tank. When the aircraft dives the fuel flows towards the front of the tank. The float is in a fixed position and can only respond to the up and down motion of the fuel. If all of the fuel has moved forward and away from the float then the float will fall down and indicate a lower amount of fuel then is currently available, conversely if the mass of fuel gathers in the area where the float is located then the float indicates a higher amount of fuel then what is actually available. Only when the aircraft is flying straight and level will the system provide an accurate report of fuel quantity. These types of inaccuracies are intolerable on a long range aircraft which is carrying thousands of pounds of fuel.
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