Continental Calls for O-360, O-470, O-520 and O-550 Engine Counterweight Inspection (Corrected.)


Continental Aerospace Friday said it’s asking owners of O-360, O-470, O-520 and O-550 series engines manufactured after June 1, 2021, and with fewer than 200 hours to perform crankshaft inspections to check counterweight retaining ring installations. The announcement from Continental follows a report from Cirrus on Wednesday that it has grounded all of its own aircraft in response to an alert from Continental about a potential engine manufacturing defect.

Here’s the full statement from Continental: “Continental has identified a potential safety of flight issue for aircraft equipped with Continental 360, 470, 520, 550 series engines and replacement crankshaft assemblies. Consequently, Continental is preemptively advising that an inspection should be performed to confirm that the crankshaft counterweight retaining ring was properly installed in new and rebuilt engines assembled between June 1, 2021, and February 7, 2023.

“This advice also applies to replacement crankshaft assemblies manufactured between June 1, 2021, through February 7, 2023. Continental proactively recommends that all flights powered by the aforementioned engines with less than 200 operating hours be limited to 5 additional flight hours with the essential crew to position the aircraft at a maintenance facility. To further clarify, Continental engines with over 200 hours may continue normal flight operations. A service bulletin with affected serial numbers will be forthcoming.”

The total number of engines affected is about 2000, but Continental said it’s unknown how many of those are beyond 200 hours. Warranty performance and reimbursement is described in this service bulletin released on February 13. On many of its engines, Continental uses moving counterweights to reduce torsional loads on the crankshaft. The weights are held in place on the crankshaft with a pin arrangement secured with snap rings. The weights counteract torsional loads by sliding across a small range of movement. The defect, says Continental, is due to an assembly error, not an incorrectly manufactured part. As described in the service bulletin, the weights and snap rings can be accessed by removing cylinders without the need to split the engine case or remove the engine from the airframe. The photo in this story depicts a counterweight removed, but this service instruction only requires checking the snap ring, not removing the weights. All of the engines in question are six-cylinder models.  

Other AVwebflash Articles


  1. The article seems contradictory. In one instance it says that Continental is “requiring” owners to perform inspections and in another it says that Continental is “advising” owners that inspections be performed.

    I suspect the latter is correct. Continental has no authority to “require” that an owner perform an inspection.

  2. I said this when Mr. Niles first wrote about this and I’ll say it again. Since cylinders have to be pulled to access the counterweights, is Continental creating a solution that may be worse than the original issue? Is this solution a cheap way for Continental to get out of replacing engines outright? I wonder who gets to pay for all those inspections?

  3. I guess being owned by the Chinese government makes you forget how to assemble components after 60+ years of doing it.

  4. Holly Molly! Continental… Well, now “we know” what the “issue” was when Cirrus announced some of its fleet be grounded because of an “issue”. Continental should be responsible for replacing the engines. If I had a brand new Cirrus in this circumstance I would not accept “removing the cylinders” to inspect the snap rings! Screw that! It’s not my responsibility to cheaply try to fix a problem created by Continental. Replace the engines Continental! You caused the problem on your factories! Brand new engines! That’s it.

    • WE will ALL pay for Continentals’ mistake…. via increased costs so Continental can recover the expenses from this screw up. :{

      (This is not likely due to Chinese ownership, however. It’d likely due to an inexperienced employee new on the task.)

  5. Not being a mechanic, what does the direction the snap ring faces make and what happens that makes it ok after 200 hours. Anybody know? Inquiring minds….

    • Snap rings are stamped when they are made. The top side is slightly rounded and the bottom side has a sharper edge. When you install it, you want the sharper edge facing out, this aids in holding it in place. Having the rounded edge up can lead to the snap ring coming out, which is most likely the problem that has happened here.

  6. This is gonna be ugly no matter what. There are now 2 separate issues with the same engines during the same time frame of manufacture. AD 2023-02-12 covers Superior cylinder valve issues and now this counterweight issue on the same. Thats gonna be the kind of warranty work no one wants.

  7. I read the article and the instructions and do not understand why engines with more than 200 hours do not need to be inspected. Did they heal themselves?