FAA Powerplant Written Practice Test

What is the function of full-floating piston pins in an engine?

1. To secure the piston firmly to the connecting rod

2. To allow motion between the pin and the piston and the small end of the connecting rod

3. To maintain constant lubrication between the components

4. To prevent vibration during operation

The correct answer is: To allow motion between the pin and the piston and the small end of the connecting rod

The function of full-floating piston pins in an engine is to allow motion between the pin, the piston, and the small end of the connecting rod. This design enables the piston to rotate slightly as it moves up and down, accommodating thermal expansion and minimizing wear on the piston and the connecting rod. In a full-floating arrangement, the piston pin is not permanently fixed to either the piston or the connecting rod, allowing for easier assembly and better performance by reducing friction and wear. This mobility is crucial for the effective operation of the piston within the cylinder, as it can help reduce side loading and improve overall engine efficiency. This feature also allows for improved alignment between the piston and the connecting rod during the engine's operation, contributing to the longevity of the engine components. The other options do not accurately reflect the primary purpose of full-floating piston pins, as they focus on securing the components or lubrication rather than facilitating relative motion.