FAA Powerplant Written Practice Test

A characteristic of Dyna-focal engine mounts on aircraft reciprocating engines is that the:

1. Shock mounts are made of steel

2. Shock mounts point towards the engine's center of gravity

3. Mounts can pivot freely

4. Mounting points are fixed

The correct answer is: Shock mounts point towards the engine's center of gravity

The characteristic of Dyna-focal engine mounts that is correctly identified is that the shock mounts point towards the engine's center of gravity. This design principle helps to provide a more effective alignment and load distribution throughout the mount. By aligning the mounts towards the center of gravity, the engine's weight is evenly supported, which helps reduce stress on the airframe and enhances engine stability during operation. This alignment also minimizes the potential for vibration and movement, which can lead to mechanical failure or discomfort for passengers. Dyna-focal mounts are particularly designed to allow some movement while ensuring that the engine remains securely positioned relative to its center of gravity. The other choices do not accurately capture the functional design aspect of Dyna-focal mounts as related to engine dynamics and performance. For instance, shock mounts are typically made of rubber or elastomeric materials rather than steel to provide proper damping and vibration isolation. Although mounts do have some degree of flexibility, they are not designed to pivot freely; instead, they offer controlled movement to maintain alignment. Lastly, the mounting points are not fixed in the sense that rigid mounts would be; they incorporate design features that allow for controlled movement while still securing the engine effectively.