Mandatory Service Bulletin MSB05-8B (camshaft gear) downgraded to non-mandatory. FAA will not issue AD.
In April, my blog post “Continental’s War on Camshaft Gears” I wrote about Continental Motors’ issuance of Mandatory Service Bulletin MSB05-8B intended to compel owners of Continental 520- and 550-series engines (and a few IO-470s) to preemptively replace the older-style camshaft gears with a newer-style gear that is .060” thicker (about the thickness of a penny).
MSB05-8B would have mandated that engines with the older-style gear would need to be disassembled and the new-style gear installed “within 100-hours of operation, at the next engine overhaul (not to exceed 12 years engine time in service), or whenever camshaft gear is accessible, whichever occurs first.” This would have meant that many thousands of low-time-since-overhaul engines would need to be torn down within 100 hours, and that any engine overhauled more than 12 years ago would need to be torn down before further flight.
Owners push back
When MSB05-8B hit the streets, aviation type club forums were awash with cries of disbelief, expletives, and demands for class-action lawsuits—both against Continental Motors and against the overhaul shops that elected to overhaul engines without installing the new-style camshaft gears. The uncertainty also took its toll on the resale market for Continental-powered aircraft.
My company Savvy Aviation joined a group of stakeholder representatives including AOPA, American Bonanza Society, Cirrus Owners and Pilots Association, and Twin Cessna Flyer. Our group prepared a 10-page response to the FAA on this subject that was submitted to the FAA Engine & Propeller Directorate and to the Atlanta Aircraft Certification Office on May 1. We argued forcefully that the extremely low crankshaft gear failure rate did not rise to the level of “an unsafe condition” required to justify the issuance of an AD.
May and June passed with no word from Continental. Then in early July, AOPA’s Dave Oord emailed the members of our group to say that Continental was about to issue the long-awaited revised MSB and had asked to discuss it with us prior to publication. We were surprised and delighted that Continental was reaching out to us, and agreed to an electronic meeting on July 13th.
Can we talk?
Continental told us that they were planning to release a new MSB05-8C the next day, calling for repetitive visual inspections of older-style camshaft gears at every annual or 100-hour inspection (whichever was applicable to the aircraft), with gear replacement mandated at the next overhaul or case-splitting event. We learned that the FAA and Continental had uncovered only seven documented camshaft gear failures from 1964 to the present, the majority of which were unrelated to any in-flight engine anomalies. We also learned that an estimated 26,000 engines would be affected by the MSB.
Alarmingly, this was issued as a Mandatory Service Bulletin (MSB), which Continental defines as one that “has been incorporated in whole or in part into an Airworthiness Directive (AD) issued by the FAA or have been issued at the direction of the FAA by the manufacturer requiring compliance with an already-issued AD.” It was conspicuously NOT issued as a Critical Service Bulletin (CSB), which Continental defines to be a “candidate for incorporation into an FAA Airworthiness Directive.”
We made a strong appeal for Continental to issue its revision as a CSB rather than an MSB, given that the FAA had not yet decided whether an AD was warranted. We also urged the FAA to think carefully about whether such a tiny number of gear failures over such a long time period (most of which had no safety consequences) really rose to the level of “an unsafe condition” under the FAA’s guidelines for when an AD should be issued. We further argued that the repetitive inspections Continental was proposing would be staggeringly costly to owners and would not prevent a single engine failure.
To put all this in perspective, there has been only ONE in-flight camshaft gear failure in the past 53 years, and that one resulted in an uneventful on-airport forced landing. This makes the camshaft gear arguably the most reliable and least failure-prone component of the engine.
The next day, July 14th, each of us individually received a call from Continental Vice President Emmanuel Davidson, who gave us wonderful news: After carefully considering our comments and conducting further discussions with the FAA, Continental had decided to issue its revision as a non-mandatory CSB, and the FAA had decided that no AD was warranted at this time.
This was a marvelous outcome for owners of Continental-powered aircraft, and it was achieved through the most constructive and cooperative interaction I’ve ever seen between owners, a manufacturer, and the FAA (and I’ve been doing this for a long time). I sincerely hope this will become a model for how such situations are dealt with going forward. Kudos to Continental and the FAA for listening with open minds, and ultimately doing the right thing.