Federal Aviation Administration

Special Airworthiness Information Bulletin

- ANE-99-30.pdf

Make:
Textron Lycoming

Model:
Textron Lycoming Recip. engine crankshaft counterweight pilot holes

Product Type:
Engine

Product Subtype:




Full Text of the SAIB

SPECIAL AIRWORTHINESS INFORMATION BULLETIN REGULATORY SUPPORT DIVISION P.O. BOX 26460 OKLAHOMA CITY, OKLAHOMA 73125-0460

U.S. Department of Transportation Federal Aviation Administration No. ANE-99-30 July 12, 1999

SAIB’s are posted on the internet at http://av-info.faa.gov

This is issued for informational purposes only and any recommendation for corrective action is not mandatory.

Introduction:
This Special Airworthiness Information Bulletin (SAIB) provides information addressing Textron Lycoming reciprocating engine crankshaft counterweight pilot holes out of round condition (elongation) delivered by manufacturer, resulting in possible failure (fracture) of the crankshaft counterweight bushings and/or counterweight ears. By issuing this SAIB, the FAA Engine & Propeller Directorate is providing additional information and guidance intended to facilitate identification of abnormally worn crankshaft counterweight pilot holes (due to an out of round condition) and possible failure of the crankshaft counterweight ears and bushing. This SAIB also describes appropriate inspection/maintenance actions by owners/operators of Textron Lycoming engines, repair stations, mechanics holding Inspection Authorization (IA) and FAA Principal Maintenance Inspectors.

Reference Documents:
The following references document information and guidance regarding crankshaft counterweight Inspection and recommended corrective action.

1. Textron Lycoming Service Bulletin No. 480C dated February 26, 1999, advising early and frequent inspection of the oil filter and spectrographic analysis of the oil system for piston pin plug aluminum deposits.
2. AC43.13-1B Chapter 8 Section 8.6 “Inspection of Oil Filter”.
3. Textron Lycoming Service Instruction No. 1142B, “Replacement of Crankshaft Counterweight Bushings”, dated May 7, 1971.
4. Textron Lycoming Service Instruction No. 1152A, “Punch Marks on Crankshaft Counterweight Lobes”, dated August 3, 1979.

For copies of referenced documents, write to: Textron Lycoming Product Support Department, 652 Oliver Street, Williamsport, PA 17701; or telephone: (570) 323-6181.

Background:
An undetermined quantity of non-conforming crankshafts have been manufactured by Textron Lycoming and installed into new, remanufactured or overhauled engines at Textron Lycoming. Although the exact cause of failure has not been determined, it is suspected that an out of round (elongated) condition of the crankshaft counterweight bushing pilot holes in combination with below minimum crankshaft counterweight ear edge distance may contribute to the failure. An elongated hole allows the bushing to work loose and/or wear to the point of breakage during engine operation, and may eventually initiate a fatigue crack in the surrounding metal . The FAA has been informed that 5 failures of this nature have occurred to crankshafts since July 1996 to date. Approximately 2700 engines have been manufactured within this time period. These 5 failures occurred between 88 to 517 hours of operation and have manifested themselves as:

1. 88 hours of operation -- engine failed during 150 hours endurance test.
2. 140 hours of operation – erratic power fluctuation in flight, metal in screen/filter.
3. 121 hours of operation – engine making metal (discovered in the filter).
4. 244.6 hours on shaft (since overhaul) – zero oil pressure in flight.
5. 517 hours of operation – loss of oil pressure in flight (#1 cylinder indicated low compression (internal engine damage).

Performing oil filter inspections and oil analysis during oil changes may have precluded all of the above incidences with the exception of failure #1. Excessive wear on field engines can most likely be identified by filter inspection and oil analysis (See Ref. 1, and 2). If metal wear is found in an engine, the oil pump suction screen should be checked. A determination should be made as to what type of metal was found in order to take appropriate action.

Textron Lycoming has instituted internal manufacturing corrective action to prevent future non-conformance of the crankshaft counterweight pilot holes. The FAA is monitoring Textron Lycoming manufacturing processes and procedures and will also monitor field failure data to determine if further action is required.

Recommendations:
The FAA recommended actions to detect and preclude some crankshaft counterweight failure are as follows:

1. Oil filter inspection and oil analysis (See Ref. 1, and 2) can identify crankshaft counterweight pilot hole and bushing wear on field engines. If metal (ferrous and non-ferrous) is found in an engine, the oil pump suction screen should be checked and a determination made as to what type of metal was found and the source in order to take appropriate action. Reference 1 and 2 state that during the recommended oil change intervals (10 hours initially, followed by 25 hours for new, remanufactured, or overhauled engines and subsequently by 50 hours TIS), inspecting the filter and having a spectroscopic oil analysis performed could be very useful in monitoring engine wear to preclude failure.
2. Ensure that Ref. 3 and 4 are accomplished when inspecting, removing and reinstalling the crankshaft counterweight bushings.

FOR FURTHER INFORMATION CONTACT:
Rocco Viselli, FAA, Engine & Propeller Directorate, New York Aircraft Certification Office, 10 Fifth Street, 3 ^rd Floor, Valley Stream, NY 11581, telephone: (516) 256-7531; Fax: (516) 568-2716; email: rocco.viselli@faa.gov.



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