FAA Aviation Mechanic Airframe (AMA)Fuel, Cabin and Ice Control SystemsMedium
A technician troubleshoots a mechanical, float-type fuel quantity indicating system on a light aircraft. The float arm is connected directly to a needle on the cockpit gauge via a mechanical linkage. What is a key limitation of this type of system compared to a capacitance-type system?
- AIt requires a constant electrical power source to function
- BIt provides accurate readings only within a limited range of aircraft attitude and fuel level
- CIt cannot be used with any fuel tank shape
- DIt is unaffected by fuel sloshing during maneuvers
Show answer & explanationAnswer & explanation
Correct answer: B. It provides accurate readings only within a limited range of aircraft attitude and fuel level
Mechanical float-type systems rely on a float following the fuel surface and are affected by aircraft attitude, tank shape, and fuel sloshing, making them less accurate than capacitance systems, especially at low fuel quantities or during maneuvering flight.
Why the other options are wrong
- A. Purely mechanical float systems don't require electrical power at all, unlike capacitance systems.
- C. Float systems are used in many tank shapes but with reduced accuracy; this isn't the primary limitation described.
- D. Float systems are actually quite susceptible to reading errors from fuel sloshing.
Float-Type Fuel Quantity Indicator
A mechanical system using a float on the fuel surface connected via linkage or arm to a cockpit gauge to indicate fuel level.
- Simple, no electrical power needed for basic types
- Affected by aircraft attitude and fuel sloshing
- Less accurate than capacitance systems
Memory trick: Float = 'bobs with the wobbles' — inaccurate in turns