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Aeromatic;
About the FAA SAIB NE–01-23  
Tuesday, August 12, 2008, 01:55 PM - FAA SAIB NE–01-23
Posted by Administrator
Back in 2000 there was a supposed dry rot failure of an Aeromatic propeller blade. It was NOT a Tarver propeller blade.



I obtained the broken blade from the owner for my own inspection. I did not find any dry rot in the blade. I noticed that the blade showed that it had been broken out of the hub in the plane of rotation. This force was from the trailing edge toward the leading edge. The blade was rotating in the normal forward direction when it struck some object at about half way to the tip. The blade was totally severed at this point. The force that severed the blade came from the leading to trailing edge direction, 180 degrees from the force that broke the blade out of the hub. In addition to the above, the blade was split about 12-14 inches from the shank outward spanwise. (See photos below)



This is not consistent with a blade that was slung out of a hub by centrifugal force. It is however, consistent with a prop strike.



The blade was sent to the Forest Products Laboratory, a branch of the US Department of Agriculture, for failure analysis. The Forest Products Laboratory is located on the campus of the University of Wisconsin, Madison. This laboratory is the world’s foremost authority on wood.



The report received from the Forest Products Laboratory stated that “The blade did not fail due to wood decay” .* The failed blade was manufactured by the Koppers company on 30 September 1959.(s/n 13332)







FAA SAIB NE–01-23 dated May 23, 2001.



The following is quoted from the above SAIB.



Background



A pilot recorded one in-flight failure when the pilot reduced power to maximum continuous after takeoff, and experienced a massive and violent engine vibration and displacement. The pilot immediately reduced power to idle and safely landed the aircraft. Investigation of the incident revealed that one propeller wooden blade had separated from the hub due to dry rot around the blade root lag screws. As the blade separated from the airplane, the missing blade caused a propeller imbalance, which subsequently damaged all four-engine mounts due to the unbalance loads. This allowed the engine/nose cowl and attachment to drop approximately 1-1 ˝ feet affecting the control of the airplane. There have been other Tarver wooden

blades found with dry rot, corrosion damage, and other various unairworthy conditions.



Note 2. The subject propellers have been in-service for many years and may have deteriorated due to age, moisture, or insufficient maintenance. These factors could result in propeller blade separation and possible loss of control of the aircraft.



Recommendations

The FAA highly recommends that you, an owner or operator of aircraft equipped with the Tarver wooden propellers, accomplish the inspection for blade looseness described in Tarver Propeller LLC. Service Bulletin (SB) No. 2000-001 dated July 31, 2000, Part I, prior to every flight.




*Notice that in the SAIB above the writer says that the blade failed due to dry rot. This is totally false.



The last line in the first paragraph of the above SAIB “There have been other Tarver wooden blades found with dry rot, corrosion damage, and other various unairworthy conditions.”



Again this statement has no factual basis whatsoever. It is an assumption on the part of the writer of the original proposed AD note which was turned into the infamous SAIB.



I have requested the FAA to cancel the SAIB. They say they can’t cancel an SAIB but they will modify it. They promised to fix it but they have bigger problems than my itty bitty company.




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