FAA Powerplant Written Practice Test

What type of fuel flow meter is typically used on reciprocating engines?

1. Mass flow meter

2. Pressure based flow meter

3. Electronic flow gauge

4. Mechanical rotor flow meter

The correct answer is: Pressure based flow meter

For reciprocating engines, a pressure-based flow meter is commonly used to measure fuel flow. This type of flow meter operates by measuring the pressure differential across a restriction or orifice in the fuel line. The pressure drop correlates directly with the flow rate of the fuel, allowing for accurate measurements under various operating conditions. Pressure-based flow meters are favored in reciprocating engines due to their simplicity and reliability in measuring flow under varying fuel characteristics and operating conditions. They can accommodate a wide range of fuel types while providing real-time feedback to the engine management system. While mass flow meters and electronic flow gauges offer advantages in specific applications, they are less common in standard reciprocating engine configurations. Mechanical rotor flow meters, which use moving parts to measure flow, can be used but may present mechanical wear issues in the long term compared to a pressure-based system. Thus, the choice of a pressure-based flow meter aligns well with the operational needs of reciprocating engines.