AOPA is concerned about an onerous proposed airworthiness directive for McCauley propellers because it doesn't appear to be based on solid analytical data.
"The FAA failed to supply accident data to support this action. The proposal is based exclusively on test data supplied by McCauley," said Luis Gutierrez, AOPA director of regulatory and certification policy.
The proposed AD would require owners of certain McCauley propellers installed on Teledyne Continental IO-520, TSIO-520, or IO-550 engines to add an operational rpm restriction on the propellers and install an rpm restriction placard in the cockpit. It also would add a 10,000-hour total time-in-service (TIS) life limit for these propellers. Any propellers that have 10,000 hours or more total TIS or that have unknown total TIS numbers would have to be removed from service. In addition, it would require initial and repetitive propeller blade inspections.
The FAA estimates that the proposed AD would affect nearly 1,000 Beechcraft Bonanza and T-34 airplanes and Navion airplanes. About 500 propellers would need replacement at a cost of $10,500 per propeller plus labor.
The proposed AD stemmed from some recent tests McCauley had conducted to measure vibratory stress. The company said the tests identified a "high stress condition that reduces the fatigue life and damage tolerance" of the propellers, according to the proposed AD.
AOPA will be filing comments on the proposal. The comment deadline is January 17.
See also the AOPA Air Safety Foundation's new online course " Engine and Propeller."
November 17, 2005