Recommendation R20010257

Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: R20010257
Date issued: 19 December 2001
Safety action status:
Background: Why this Recommendation was developed

Output text

The Australian Transport Safety Bureau recommends that the Civil Aviation Safety Authority review the operating and maintenance procedures for high powered piston engines fitted to Australian registered aircraft to ensure adequate management and control of combustion chamber deposits, preignition and detonation.

Initial response
Date issued: 06 March 2002
Response from: Civil Aviation Safety Authority
Response text:

CASA acknowledges the intention of the safety recommendation and advises that the Authority has taken significant steps to address this issue with the Federal Aviation Administration in relation to the, certification of the Piper aircraft and engine.

In discussions with the Federal Aviation Administration (FAA) New York Aircraft Certification Office and the FAA Atlanta Aircraft Certification Office, CASA advised that one of the primary issues identified in the Whyalla accident was aggressive fuel leaning.

CASA advised the New York and Atlanta FAA Offices of the discrepancies identified between the Engine Operating Manual approved by the New York Office and the Aircraft Flight Manual approved by the Atlanta Office.

Following these discussions, the Atlanta Office has responded with advice that the FAA is of the opinion that fuel mixture leaning procedures were not a contributing factor in the events of May 2000.

This response is not consistent with the findings of the ATSB in regards to the resulting combustion chamber deposits, preignition and detonation.

CASA's actions in regards to this recommendation are ongoing, and discussions are being held with the engine manufacturer. CASA undertakes to advise the ATSB of the outcomes of these discussions as they progress.

In relation to the maintenance procedures for all high-powered piston engines fitted to Australian registered aircraft, CASA advises that action in relation to this matter is ongoing.

CASA intends to review current maintenance procedures applied to all high-powered piston engines fitted to Australian Registered aircraft to ensure compliance with manufacturer's published procedures, and in the opinion of the Authority, this action will provide timely notice of engine distress resulting from combustion chamber deposits.

In relation to the operating procedures for all high-powered piston engines fitted to Australian Registered aircraft, CASA advises that the Authority has notified all operators of Textron Lycoming and Teledyne Continental Motors piston engines aircraft of reports of crankshaft bearing failures.

To minimise the risk of combustion chamber deposits resulting in abnormal loading of the bearings, CASA has recommended the operators adopt conservative fuel mixture leaning procedures.

A copy of this letter is provided for the information of the ATSB.

The following is a copy of the letter

To all operators of Textron Lycomiag and Teledyne Continental Motors piston engines with a take off power rating greater than 250 horsepower

And aircraft maintenance organisations

Subject: Lycoming and TCM Crankshaft Bearing and Connecting Rod Bearing Failures

Since August 2001, CASA has received 9 major defect reports relating to crankshaft and connecting rod bearing failures. Six of the failures occurred in Lycoming engines and three in TCM engines. All of the failures have occurred at a low bearing time in service. All but one of the reports involved large, high horsepower engines. A preliminary examination of a number of the failed bearings indicates evidence of delamination of the bearing shell layers. That examination result is consistent with undocumented reports of warranty claims against engines exhibiting bearing material in the oil filters of low time in service engines.

Textron Lycoming, Teledyne Continental Motors, Superior Air Parts and the FAA have been advised. of the bearing defects being reported in Australia CASA is conducting on-goingdiscussions with Lycoming, TCM and Superior Air Parts on the reported failures. 'However, CASA, has been advised; crankshaft bearings can also be supplied by non original equipment manufacturers each with a unique prefix to the original part number. Air Support and Engine Components Incorporated are two such suppliers. An Air Support supplied bearing will have the prefix "AS", eg; AS 13884-M03

Textron Lycoming has advised; bearing delamination detects should not present a safety of flight concern if the engine oil pressure filter and oil pressure screen are inspected for metal contamination at each oil and filter change. Cutting open the filter and examining the filter element as detailed in Lycoming Service Bulletin Number 480D will provide ample opportunity to detect an impending bearing failure. The FAA supports the Lyconung response.

Aggressive fuel mixture leaning may be relevant to the reported bearing defects.' The Australian Transport Safety Bureau, in investigating the dual engine failures associated with the fatal Whyalla Airlines Piper PA31-350 accident, noted a relationship between bearing failures and aggressive fuel leaning procedures. The ATSB lists engine operating practices as a contributing factor in that accident. A copy of the ATSB report can be found on the internet at The CASA Flight Safety Australia Jan/Feb 2001 "Lean and Mean" article advising of the real costs of aggressive fuel mixture leaning also provides useful information on this subject.

Until a full understanding of the causes of the crankshaft bearing failures is obtained, CASA recommends all Lycoming and TCM piston engine powered aircraft operators and applicable maintenance organisations carry out the following precautionary procedures.

1. Fuel mixture leaning procedures detailed in the aircraft manufacturer's flight manual or pilot operating handbook may be different to the procedures recommended by the engine manufacturer. The engine manufacturer may recommend the use of richer fuel mixtures than those approved by the aircraft manufacturer. To limit crankshaft bearing exposure to abnormal combustion loads occurring during aggressive leaning procedures, observe the fuel mixture leaning procedure limits detailed in the engine manufacturer's operators manual.

2. At each engine oil change and filter change, if applicable to the engine model, inspect the oil pressure screen, oil suction screen and cut open the oil filter and inspect the filter element for evidence of metal contamination, Lycoming SB 480D and TCM SB M87-12 Rev.l refer; and

3. Carry out an engine oil change and, if applicable, an oil filter change, at intervals as published by the engine manufacturer, Lycoming SB 480D and TCM SB M87-12 Rev. l refer; and

4. At each engine oil change, drain the oil whilst the engine is still hot and strain the oil through a fine mesh screen filter. If a bearing defect is present, hot oil will flush out bearing material 'flakes.

Defects found in carrying out the above recommendation should be reported to CASA on the Major Defect Form available from the CASA website, CASA is continuing to seek an understanding on the primary cause of the bearing defects, in submitting such defect reports, please include all available information on the supplier and part number of the bearings fitted.

Further correspondence
Date issued: 19 November 2003
Response from: Civil Aviation Safety Authority
Response status: Closed - Accepted
Response text:

The Australian Transport Safety Bureau (ATSB) has requested that the Civil Aviation Safety Authority (CASA) seek further clarification from the Federal Aviation Administration (FAA) on detonation limiting conditions and examine what steps CASA can take to ensure that operating procedures used by operators of fleets of more than one aircraft type take account of the requirements contained in varying operating manuals and handbooks.

In response to the first issue, the FAA has been advised of CASA's specific concern with the fuel mixture leaning procedures being different in the three Pilot Operating Handbooks (POHs) for the PA31-350 Chieftain. Despite all serial numbers of PA31-350 aircraft having identical fuel systems, engines and performance, a fleet operator may operate a mix of aircraft serial number ranges, and yet, in ignorance, operate all aircraft to the one manual. CASA is writing a follow up letter to the FAA reiterating our concerns on this issue and CASA undertakes to advise the ATSB of the FAA's response.

In response to the second issue, CASA's auditing of fleet operators now requires the approved Operating Procedures Manual be reviewed with consideration given to the operating procedure document detailed in the aircraft Type Certificate Data sheet (TCDS).

This review is carried out on each individual aircraft in the fleet by type, model and the aircraft's manufacturer's serial number, and CASA believes that this step will assist in ensuring that operators of fleets including more than one model of a particular aircraft type take account of different versions of operating manuals and handbooks.

Thank you for bringing these matters to the attention of the Authority.

ATSB response:

Subsequent to CASA's response of 19 November 2003, the ATSB has released a research report into aircraft reciprocating-engine failures, B2007/0191. The ATSB now closes this recommendation.

Last update 01 April 2011