http://www.tcmlink.com/pdf2/CSB05-8C.pdf
this is from TCM
Issue resolved. The AD will not be instituted and the Cont. Mandatory service bulletin has been changed as well.
If 26000 engines get the camshaft replaced to save a few potential failures, how many other maintenance-induced failures may have been set up on otherwise good running engines. A Mooney that had a vacuum pump replaced at a local facility, had an full blown emergency landing in a field because all the oil was blown overboard because of a bad seal installation on the vacuum pump. There was no other damage, but the potential was there, the engine was perfect, just lacking oil. Obviously it was trash afterwards.
Peter, a lot more Contis throw their rods overboard per year than there have been camshaft gear failures.
It’s a combination of:
- how often does it happen
- what’s the economic impact of an AD
- is there really a clear known cause and remedy
Not everything gets addressed and there are many failure modes that could be consider unacceptable.
You never know what may break when you are flying, and there are so many other things that are (more) likely to break… The bad thing about this one is that it would result in a catastrophic failure. You go from cruise power or more to 0% power in the blink of an eye.
The other side of these MSBs, and this one is similar IF it doesn’t become an AD) is that you don’t really know if it is going to break when you are flying.
I see this Conti MSB was not based on a large number of engine failures, so one can IMHO take a chance on it. Now let’s say this Lyco MSB is based on a similar % of engine failures. The Lyco discussion belongs to the other thread linked above, and no doubt will materialse there as and when the FAA does or doesn’t make it an AD, but if it was my engine I would be seriously concerned about flying with it.
You get these considerations in the homebuilt world where ADs can be disregarded (in most registries) but I think most of the owners simply chose to take the risk.
Pfeeew! Close call!
Today Mike Bush has posted the following on his facebook page:
Fantastic news for owners of Continental 520/550 engines: The FAA has determined that no Airworthiness Directive against our camshaft gears is warranted at this time. Continental’s MSB05-8B has been revised and demoted as CSB05-8C to reflect this. Only 13 camshaft gear failures could be documented among a population of 26,000 engines, and we’re aware of only one that resulted in an in-flight engine failure and forced landing. The proposed camshaft gear inspections would have been enormously expensive. Continental Motors and the FAA worked very constructively with aircraft owner groups, and ultimately reason and common sense has prevailed. Kudos to everyone who participated in achieving this great outcome.
