Continental Motors thinks some aviation maintenance technicians missed the point of an engine service bulletin — SB05-8A — first issued in 2005. The document announced a replacement camshaft that Continental said would improve the operation of a variety of well-known engines like the IO-470 and the IO-550, used on everything from the Cessna 182 to the Beechcraft Bonanza. The replacement was designed to prevent a possible gear tooth fracture and a possible power failure that could follow.
While the original service bulletin didn’t demand compliance, Continental representatives assumed anyone cracking open the engine crankcase for any reason would naturally want to change the camshaft gear. Apparently that hasn’t been the case. Continental representatives at last week’s Sun ‘n Fun said they were shocked the original bulletin was not being followed automatically, so the company recently upgraded the bulletin to mandatory — MSB 05-08B — one step below an airworthiness directive.
Ken VeArd flies a turbo-Bonanza from Austin, Texas. He met with Continental representatives at Sun ‘n Fun and said they told him, “Most shops are still removing the original gear, testing it and reinstalling it,” which defeats the purpose of the original bulletin. The upgraded bulletin now expects compliance “within 100 hours of operation, at the next engine overhaul (not to exceed 12 years engine time in service), or whenever the camshaft gear is accessible, whichever occurs first.” One representative told VeArd there have been 10 to 15 accidents with engines operating the old camshaft. Others on site in Lakeland told VeArd they were skeptical the number was that high.
VeArd said he was still grateful the crankcase on the Bonanza just happened to be apart when the updated bulletin appeared, but that the engine builder probably underestimated the work and cost involved in the update. “The part is roughly $1,200 and requires a small amount of machining inside the case to get installed,” VeArd said. Continental estimates about two hours of work … if the case is already open. If it’s not, operators should prepare to perform the work within the next 100 hours of operation.