Continental Aerospace Technologies Monday released a mandatory service bulletin describing how to inspect for improperly installed snap rings on about 2000 six-cylinder engines. The bulletin describes how to reseat the rings, if necessary, and also details warranty reimbursement.
The issue surfaced earlier this month when Continental notified Cirrus through a letter that snap rings had been improperly installed on engines and crankshafts manufactured between June 21, 2021, and Feb. 7, 2023. Continental said Monday that the problem was caused by improper assembly, not a defective part.
On its six-cylinder engines, Continental uses crankshaft counterbalance weights that move and suppress torsional or twisting loads on the crankshaft. The weights slide across a small range of motion and are able to respond to RPM shifts. They ride on pins held in place by the snap rings. The company says the snap rings were improperly installed and may not have seated fully in the groove designed to retain them.
The service bulletin requires inspecting the snap rings by removing one to three cylinders—variable with engine model—to gain access to the weights. The weights themselves do not have to be removed unless difficulties are encountered in seating the snap rings. Continental will loan a gauge to insert between the ears of the snap rings to determine if they’re fully seated. It also provides dimensions to field manufacture the gauge. The gap should be between 0.179 inch and 0.212 inch, depending on the engine model. The service bulletin describes how to reseat the rings if they are out of spec. The bulletin also advises techs to make sure the open end of the snap ring is oriented toward the crankshaft centerline.
Engines with more than 200 hours are exempt from the inspection, the reasoning being that if the rings allowed the pins and weight to depart, that would have occurred in the first 200 hours. It’s not known how many of the listed engines have accumulated this much flight time.
Continental will cover the cost of the work under warranty, for both engines and crankshafts. It will also establish a direct dial call center at 251-441-4460 for questions on the procedure.
Lousy situation but I respect them for taking responsibility and trying to make it right.
The obvious problem is that pulling cylinders will affect preload on the main bearings and this can lead to issues in the future, that will not likely be covered by warrantee.
Preload on the mains? Detailed explanation needed please.
Never heard if it.
A horizontally opposed aircraft engine is a light structure that carries a lot of load. It’s critical that the through studs holding the case together are torqued to the right value in the right order.
When cylinders are removed, if not done correctly, it can distort the torque loads on the case and thus the main bearings. This can cause them to spin in their mounts and fail. While this is not a common cause of engine failures, it happens frequently enough after cylinder work to raise real alarm about removing three cylinders from one side or even one cylinder.
Torque plates to hold the load temporarily are supposed to prevent this, but believe it or not, not all shops know how to do this properly. If it were my engine, I’d take it to a good engine shop where they’re more likely to know how to do it correctly.
I had to look-up what a snap ring was – we call them circlips here in the UK.
In the USA, we generally use “circlip” for the plain wire variety, often used to locate wrist [gudgeon] pins in the piston.
“Continental said Monday that the problem was caused by improper assembly, not a defective part.: The kinda have to cover this. Improper assembly is never a good thing.
I want to see what Continental and Cirrus call out for the acceptable time to perform this inspection. Usually they are way off and whats the shop rate they are figuring it on.
Click on the “service bulletin” link for specifics. Replacement crankshaft assemblies allow for 0.15 hr inspection time, and 0.25 hr for replacement or adjustment (per counterweight).
For engines, add 10, 18, or 22 hours for cylinder removal, depending on whether the specific model requires pulling 1, 2, or 3 jugs.
Can’t believe those time estimates.
Yeah, I think in 22 hours I can build an engine from the parts bin, and install it.
Bad deal for new engine owners. You paid for a new engine, now have your local A&P tear it apart. Good luck.
How many engines have had the pins and weights come apart?
How was this problem discovered?
How is it that if the engine survived for 200 hours that suddenly it’s not a problem?
There have been zero reported failures (that is, the pin itself coming loose), but because it’s not impossible, it must be fixed. Apparently the ring can be seated properly if put in “backwards” but it’s more difficult, and if it’s still there in 200 hours, it must be seated.
I’ve never been a big fan of Continental Engines, but ever since our friends in China have taken ownership of the company, I’m even less of a fan.
Made in China! A shame.
No, not “made in China”, owned by a Chinese parent company, as is Cirrus, Mooney, and other aviation entities
My guess is that the “preload on the mains” that was mentioned probably refers to the requirement for installation of torque plates when cylinders are removed, to keep adequate torque particularly on the thru-studs. So yes, that could be interpreted to mean “preload.