Aircraft Propeller Systems and Theory Flashcards

The purpose of propeller synchrophasing on multi-engine aircraft is to:

Answer: Ensure both propellers rotate at identical RPM and phase relationship to reduce cabin noise

Synchrophasing sets both propeller RPM and their rotational phase angle to minimize the beat frequency noise that causes cabin vibration.

A composite propeller blade inspection should include checking for:

Answer: Delamination, disbonding, impact damage, and erosion of the protective coating

Composite propeller blades are vulnerable to delamination, disbonding between layers, impact damage, and erosion that can compromise structural integrity.

Propeller blade 'twist' (varying pitch from root to tip) exists because:

Answer: The blade tip moves faster than the root, requiring a lower angle at the tip for uniform efficiency

Propeller blades are twisted so that the tip (moving faster) has a lower pitch angle than the root, maintaining a consistent angle of attack along the entire blade length.

During an annual inspection of a fixed-pitch propeller, which condition requires blade replacement rather than repair?

Answer: A crack of any length on the blade face

Any crack in a propeller blade is cause for rejection because cracks propagate rapidly under cyclical loading and can lead to catastrophic blade separation.

The 'beta range' in turboprop propeller operation refers to:

Answer: Ground operation range where blade angle is directly controlled by the power lever

The beta range is a ground operating mode where the pilot directly controls blade pitch through the power lever rather than through the governor, enabling ground maneuvering and reverse thrust.

Centrifugal twisting moments (CTM) acting on propeller blades tend to:

Answer: Move blades toward low pitch (fine)

Centrifugal twisting moments act to flatten the blade toward low pitch because centrifugal force tends to rotate the blade chord into the plane of rotation.