FAA Powerplant Written Practice Test

What is a key characteristic of the crankpin in an aircraft engine?

1. It is made of aluminum for weight savings

2. It is hardened by nitriding and may be hollow to reduce weight

3. It has a square shape for better rigidity

4. It is located at the top of the engine block

The correct answer is: It is hardened by nitriding and may be hollow to reduce weight

The crankpin is a crucial component in an aircraft engine, serving as the pivot point for the connecting rods that link the pistons to the crankshaft. A key characteristic of the crankpin is that it is often hardened by a process known as nitriding. This treatment enhances its wear resistance, extending the operational lifespan and reliability of the engine under the stresses of continuous operation. Additionally, the design may incorporate a hollow structure to reduce overall weight without compromising strength. Weight reduction is particularly important in aircraft engines, as it contributes to improved fuel efficiency and performance. The other factors presented in the alternatives, while they may incorporate valid engineering concepts, do not accurately describe the essential characteristics or common practices associated with crankpins in aircraft engines. For instance, crankpins are typically not made from aluminum due to concerns over strength and heat resistance, do not have a square shape which would not provide the necessary rotation mechanics, and their location is not necessarily at the top of the block as that varies in engine design.