Continental 6-cyl engines hit by cam gear issues

Continental Motors has issued further guidance for operators of aircraft affected by a Mandatory Service Bulletin (MSB) issued recently regarding some of its engines.

The bulletin affects a long list of its older six-cylinder aero engines, fitted to a wide range of aircraft including older Cessna 182s (pictured above).

Continental’s guidance:
In 2005, Continental Motors superseded Cam Gears P/Ns 631845, 655430, 655516, or 656031 with a new part, P/N 656818. Continental Motors issued Service Bulletin SB05-8 recommending the replacement of the older design parts at the next overhaul or when the gear is accessible.

Production of parts P/N 631845, 655430, 655516, or 656031 was discontinued in August 2005, and since then, only the P/N 656818 was produced and installed in factory new or factory rebuilt engines manufactured by the Continental Motors factory and sold as spares.

In July 2009, SB97-6 (Mandatory Parts Replacement at Overhaul) reiterated the need to change the parts mentioned above with the new design parts.

In late 2016 and early 2017, as part of the ongoing FAA Continued Operational Safety program, reports of camshaft gear fractures were provided to the FAA. A statistical assessment was accomplished by the FAA, and the initial data indicated an AD was merited.

The FAA then asked CMG to reformat the current bulletin into a format compatible with FAA AC 20-176 to facilitate an AD. Continental Motors subsequently superseded SB05-8A by MSB05-8B at the FAA request.

Continental Motors is working diligently with the FAA to make significant amendments to MSB05-8B. We expect this to happen in the next 15 days.

Our team is working on three main issues to alleviate the burden potentially imposed on aircraft owners and operators:

  1. Change the mandatory replacement of the camshaft gear to a visual inspection procedure allowing ‘on condition’ operation until the engine is overhauled, replaced, or the gear is accessible.
  2. Change the time limit imposed by MSB05-8B, to values that still ensure that the appropriate level of safety is attained, but does not dictate a mandatory overhaul time limit.
  3. Publish alternative means of compliance, to allow camshaft gear replacement without complete engine disassembly.

Engines affected

The following engine models are potentially affected:

  • IO-470-U, V
  • IO-520-A, B, BA, BB, C, CB, D, E, F, J, K, L, M, MB, N, NB, P, R
  • L/TSIO-520-ALL
  • LIO-520-P
  • IO-550-A, B, C, D, E, F, G, L, N, P, R
  • IOF-550-B, C, D, E, F, L, N, P, R
  • TSIO-550-A, B, C, E
  • TSIOL-550-A, B, C

Engines manufactured or rebuilt at the Continental Motors factory after 9 August 2005 are not affected as the new design part was installed from that date, unless the cam gear in the engine has been replaced during a maintenance event with an earlier, superseded gear.

Q&A

My engine was manufactured or rebuilt by the Continental Motors factory after 9 August 9 2005.

Your engine is not affected, if the cam gear was not replaced during other maintenance since the engine left the factory.

My engine was manufactured or rebuilt by the Continental Motors factory before 9 August 2005.

Only engines manufactured or rebuilt at the Continental Motors Factory before 9 August 9 2005 are potentially impacted by MSB05-8B.

Inspect logbook or other paperwork for indication of replacement of part numbers 631845, 655430, 655516, or 656031 by P/N 656818. If evidence is found that the original gear (P/N 631845, 655430, 655516, or 656031) was replaced by P/N 656818, follow instructions in MSB-05-8B.

If no evidence of parts 655430, 655516, or 656031 replacement is found: Use inspection instructions of MSB05-8B to determine the part number of the camshaft gear installed. Use the part number found to determine if replacement is necessary or not and follow instructions in MSB-05-8.

My engine was manufactured or rebuilt by the Continental Motors factory before 9 August 2995 and has been field overhauled since that date, or the case has been disassembled for any reason for a field repair.

Inspect logbook or other paperwork for indication of replacement of part numbers 631845, 655430, 655516, or 656031 by P/N 656818. If evidence is found that the original gear (P/N 631845, 655430, 655516, or 656031) was replaced by P/N 656818, document in logbook, no further action required.

If no evidence of parts 655430, 655516, or 656031 replacement is found: Use inspection instructions of MSB05-8B to determine the part number of the camshaft gear installed. Use the part number found todetermineif replacement is necessary or not and follow instructions in MSB-05-8.

Why issue an MSB mandating compliance within 12 years of manufacturing date?

Continental Motors has always indicated that engines should be overhauled when reaching 12 years after manufacturing, factory rebuild or field overhaul or after reaching the TBO set for the engine.

Although many owners operating under Part 91 choose not to observe this, we stand behind this recommendation. There are many parts, metallic or not (gaskets, O-rings etc.) that age with the engine. These parts need replacement after time in service or because age can modify their structure.

The certification process ensures that an engine reaching TBO will not be adversely affected by engine run time or because of the ageing of some materials. The fact that many planes are not hangared and are parked on a ramp, some in hot and humid or maritime climates, is also a factor to consider in the aging of airframes and engines.

Has Continental Motors requested the FAA to issue an AD on this subject?

No. The FAA COS team reviewed the data related to these gear reports and performed statistical analysis. Their analysis showed that an AD was warranted and the FAA requested that CMG rewrite the related service bulletin in a format corresponding to FAA AC 20-176 to support the pending AD activity. Continental Motors never requested the FAA to issue an AD.

Is it by design that Continental Motors issued MSB05-8B 12 years after issuing SB05-8?

No. The fact that twelve years have passed between the original issuance of SB05-8 and MSB05-8B is purely coincidental.

Continental Motors

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