How does the fuel gauge function in an aircraft?

• A. Indicates altitude changes
• B. Measures engine RPM
• C. Indicates the quantity of fuel using resistance changes
• D. Shows the pressure of the air-fuel mixture

Answer: (C)

The fuel gauge in an aircraft functions by indicating the quantity of fuel remaining in the tanks, which is typically achieved through the measurement of resistance changes in a fuel level sensing system. In this system, a float is connected to a variable resistor, or potentiometer, that changes resistance based on the float's position, which corresponds to the fuel level. As fuel levels rise or fall, the float moves accordingly, altering the resistance and thereby affecting the electrical signal sent to the fuel gauge display. This allows pilots to see an accurate representation of how much fuel is available for flight, which is crucial for flight planning and ensuring safe operations.

The other choices do not pertain to the fuel gauge's function. Indications of altitude changes and engine RPM are provided by different instruments, such as the altimeter and tachometer, respectively. The air-fuel mixture pressure is relevant to engine performance but is monitored through separate sensors and gauges that specifically track engine parameters.