What is a cause for rejection of wood propellers?

What is a cause for rejection of wood propellers?

• A. Surface cracking due to impact
• B. Incorrect color coding for wood grading
• C. An oversized hub, bolt hole or elongated bolt holes
• D. Minor scratches in wood grain

Answer: (C)

The key factor here is mounting integrity. Wood propellers must transmit engine torque through a secure, precisely matched connection between the propeller hub and the shaft. If the hub bore is oversized, the hub won’t grip the shaft properly, reducing clamping force and allowing the propeller to loosen or slip under load. Elongated bolt holes show wear or deformation from over-tightening, misalignment, or repeated cycles, which also prevents a proper, uniform clamp. Both situations compromise concentricity and the secure attachment needed for safe operation, so they are grounds for rejection. Surface cracking can indicate damage, but its acceptability depends on severity and repairability; color coding for wood grading isn’t a standard rejection criterion for propellers, and minor scratches in the wood are typically cosmetic or within repairable limits. The mounting-fit issues described in this question are the most critical and direct threat to safe operation.

The key factor here is mounting integrity. Wood propellers must transmit engine torque through a secure, precisely matched connection between the propeller hub and the shaft. If the hub bore is oversized, the hub won’t grip the shaft properly, reducing clamping force and allowing the propeller to loosen or slip under load. Elongated bolt holes show wear or deformation from over-tightening, misalignment, or repeated cycles, which also prevents a proper, uniform clamp. Both situations compromise concentricity and the secure attachment needed for safe operation, so they are grounds for rejection.

Surface cracking can indicate damage, but its acceptability depends on severity and repairability; color coding for wood grading isn’t a standard rejection criterion for propellers, and minor scratches in the wood are typically cosmetic or within repairable limits. The mounting-fit issues described in this question are the most critical and direct threat to safe operation.