CASA warns on propeller cracks

CASA has issued a reminder to pilots of the need to be vigilant about cracks in propeller blades.

The regulator says owners and operators of propeller driven aircraft must maintain vigilance when inspecting their aircraft’s prop during the pre-flight checks as in their early stages cracks are easily overlooked.

“Many propeller blade failures have been caused by fatigue crack growth from a small, sharp indentation on the leading edge of the blade,” CASA says. “These indentations are likely to be caused by stone chips suffered during operations.”

While such failures are not unique to any particular manufacturer or model of propeller blade, in almost all cases where cracks grow in propellers they fail in the outer half of the blade. And CASA says that spotting fatigue cracks in the prop blade before it’s too late would likely require inspecting not just the front but also the rear side of the blades as well.

“As fatigue cracks grow in propeller blades they may not penetrate through to the front face of the blade until just before final failure,” CASA explains. “This means the only way of detecting fatigue cracks is to carefully inspect the rear face of the blades.”

While finding no evidence that cracks in propellers will propagate from initial damage to failure in a single flight, CASA nonetheless advises maintenance personnel and pilots to carefully inspect both the rear face and leading edge of propeller blades as part of their pre-flight checks.

To read a recently issued CASA airworthiness bulletin covering prop maintenance click here.