Late last month, Continental Motors issued a mandatory service bulletin (MSB) to replace camshaft gears on several models of its IO-470, IO-520 and IO-550 series engines. Continental introduced a replacement gear more than a decade ago, but many engines remain in service with the old part, which is prone to failure. The MSB requires that owners replace the old gears at 100 hours time in service, at the next engine overhaul or within 12 calendar years, whichever happens first. The MSB will affect thousands of aircraft equipped with these engines.
Continental has asked the FAA to issue an airworthiness directive on the replacement process, which the FAA is now considering. If it decides to go ahead with the process, which is highly likely, the FAA could adopt Continental’s process and requirements verbatim, though with a proposed AD that will affect so many engines, that’s unlikely to happen. Most likely, the FAA will choose to adopt a modified version of the MSB, at which point it will issue a Notice of Proposed Rulemaking asking for comments. Ultimately, the FAA will most likely issue an AD requiring the replacement of the camshaft gears, though it could modify the time in service and calendar time requirements that Continental is asking for in its MSB.