All About The AD Request That Never Happened

Funny thing about that story earlier this week that Continental had requested the FAA issue an AD on what had been a company mandatory service bulletin (MSB) requiring the replacement of a troublesome camshaft gear. Turns out that part never happened. Here's the real story.

First, a little background. More than ten years ago, Continental discontinued the manufacture of a troublesome camshaft gear common to a number of dash-numbered IO-470, IO-520 and IO-550 engines and replaced it with a better part. It turned out that there were a number of the old parts still around and they continued being used in rebuilt engines for years after the replacement gear was available. In the wake of a couple of gear failures, Continental issued a mandatory service bulletin (MSB 05-08B) that called for the repetitive inspection of the gear and its replacement before certain intervals, 100 hours of flight time, the next annual inspection or at engine overhaul.

A number of GA news outlets reported that Continental had asked the FAA to issue an airworthiness directive on the gears, which we reported. Turns out that those reports weren't accurate, according to Continental, and the FAA. The company told Plane & Pilot that it never asked for an AD to be issued---though it's not uncommon for manufacturers to make such a request. Instead, the FAA asked Continental to revise its MSB so the agency could more easily turn it into an AD.

Furthermore, Continental now says that it is working diligently with the FAA to greatly reduce the time and expense associated with the MSB. Continental's suggestion are for owners to have the gear in question inspected visually simply by removing the starter adapter. If there's no sign of fatigue or damage to the gear, the part would be considered good to go until the next 100-hour inspection, annual inspection, or the TBO of the engine, 2,000 hours in most cases. Continental expects such a visual inspection to take less than an hour.

In a release to owners, industry and media entitled "Important Communications from Continental Motors Regarding MSB05-08B" the engine maker outlined some of the changes it was making to allow for easier and cheaper compliance with the MSB:

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.
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.
Publish alternative means of compliance, to allow camshaft gear replacement without complete engine disassembly.

Continental said it expected final word on its recommendations by early May if not sooner.

Learn more at Continental Motors.

To get more aviation news delivered to your desktop or mobile device, sign up for our weeklyeNews.

Isabel GoyerWriter

A commercial pilot, editor-in-Chief Isabel Goyer has been flying for more than 40 years, with hundreds of different aircraft in her logbook and thousands of hours. An award-winning aviation writer, photographer and editor, Ms. Goyer led teams at Sport Pilot, Air Progress and Flying before coming to Plane & Pilot in 2015.