The National Transportation Safety Board is recommending that the FAA require repetitive inspection of some cylinder assemblies on Teledyne Continental Motors Model 520 and 540 engines not covered by existing airworthiness directives issued following engine failures.
In a Feb. 24 safety recommendation, the NTSB said it wants the FAA to “require repetitive inspection of Engine Components, Inc. cylinder assemblies produced between May 2003 and October 2009 (serial numbers 7709 through 52884) installed on Teledyne Continental Motors model 520 and 550 engines and removal of these cylinder assemblies once they reach the engine manufacturer’s recommended normal time (hours) in service between overhauls.”
The letter said that since 2000 the NTSB has examined numerous ECi cylinder assemblies that failed because of fatigue cracking on Lycoming and TCM engines, in some cases resulting in fatal accidents.
Although the FAA has issued “several airworthiness directives (AD) applicable to certain new ECi cylinder assemblies used on Lycoming and TCM engines to address this issue, similar fatigue failures in other new ECi cylinder assemblies installed on TCM engines have been identified but are not covered by an existing AD,” it said.
The letter said that in most cases when fatigue cracks reached a critical size they caused fracture and separation of the cylinder heads, “resulting in catastrophic engine failure.”
At a January 2011 meeting of the FAA, NTSB, and ECi, the company recommended that the FAA issue an AD requiring inspection and replacement of any “discrepant” cylinders. The FAA has not done so, the NTSB’s safety letter said.
Since design improvements were made in October 2009, there have been no new reports of the failures on TCM 520 and 540 engines. But the NTSB said the existence in service of a “large population of potentially discrepant cylinder assemblies” without required corrective action made the recommendation necessary.