SUBJECT: Tip failures of Model M76EMM-0, M76EMMS-0, 76EM8-0, and 76EM855-0 propellers on all Lycoming 0-360 series engines except the O-360-A4A.

DISCUSSION: There are at present more than three thousand of the above listed propeller-engine combinations in service, first used in 1962. Recently several tip failures have occurred. These were fatigue-type failures and the cause is believed to be continuous operation in an rpm range of relatively high vibration stress with the propeller blades in a nicked or stone bruised condition. Following is a list of precautions for these propeller-engine combinations to prevent tip failures.

RECOMMENDED ACTION:

1. Avoid continuous operation between 2150 and 2350 rpm. Have your tachometer calibrated if facilities are available.
2. A close look at the propeller blades should be the first part of your pre-flight inspection. Cracks usually start at a nick on the leading edge, or a stone cut or bruise on the rear face of the blade.
3. Remove nicks and cuts promptly by rounding out and polishing according to approved methods before accumulating more flight time (fatigue cycles).

DISTRIBUTION:

1. FAA Regional Offices
2. Propeller Repair Stations
3. Sensenich Distributors
4. Aircraft Manufacturers
5. Lycoming Division, AVCO Corporation

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