3393RP
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3393RP
Designing and engineering a critical part that can be installed "backwards" speaks volumes about the manufacturing culture at CMI.
Oh Continental, what have you done now?
- Thread starter PaulS
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Designing and engineering a critical part that can be installed "backwards" speaks volumes about the manufacturing culture at CMI.
The guy who was putting them on had a 50/50 shot of getting it right. If it's wrong it's going to come apart within the first 200 hours...
Pinecone
En-Route
Because the ones with the problem will fail well before then.
The longest time one that failed was 41 hours.
Daleandee
Final Approach
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Dale Andee
PaulS
Touchdown! Greaser!
Most likely the failures, which supposedly have been 3 non Cirrus, have been less than 125 hours.
PaulS
Touchdown! Greaser!
Along with the fact that per the clip manufacturer the way to detect the square side is by feel and most likely someone doing this is wearing gloves.
Also I think the instructions and sketch by Continental are confusing. I look at the sketch and in my opinion it doesn't show clearly where outboard is.
FYI: most circlip installations are not direction orientated. So it simply might be the person never experienced this requirement and missed the manual note. When it is noted I use a 10x glass to see the edge and mark the ring. IMO, the diagram was sufficient to point this out. Regardless, if the ring is truly popping out within 200 hrs my bet is on the ring was not seated properly in the groove vs not installed with the sharp side outboard.
NoHeat
Final Approach
If it’s that difficult, I wonder how the inspection is going to work. How will a mechanic inspect square vs round edge facing out, while peering into a cylinder opening?
PaulS
Touchdown! Greaser!
You've been around the block a few times, we'll probably never know how this happened, but knowing what I know about manufacturing, somebody got promoted or left, the new person was given quick training and turned loose. I don't know how TCM works, but I suspect someone will get scapegoated for this, someone who really doesn't deserve it. I hope I'm wrong.
Bacho
Pre-takeoff checklist
I agree with this. Sounds a lot better to say it might be installed backwards, then not seated at all.
While anything is possible, it will probably depend on how and where the system failure occurred that will determine the discipline side. Know of a number of people who inadvertently caused expensive damage and didn't get canned to include myself. But as you stated, whether we hear the actual reason will be interesting. Once the SB gets released there might be more given in the "reason why/background" section.
Pinecone
En-Route
Longest run time on one that failed, so far, is 41 hours.
Stewartb
Final Approach
One side chamfered, one side square. Backwards would matter.
Maybe. However, these clips are used in equally critical areas on other aircraft with no orientation requirement. So perhaps its simply an interference issue with the retaining plate when the clip reversed given both are stamped parts (sharp side to sharp side) which could prevent the ring from fully seating in its groove. Be interesting to know if they checked clip ear gap to confirm engagement?
Stewartb
Final Approach
What I read is what I said. With the clip reversed it may feel seated but it can’t be seated completely.
PaulS
Touchdown! Greaser!
Could be those issues, or the chamfer could act as a ramp/cam. When force is applied to it, rather than two square surfaces engaging each other the chamfer of the clip engages the flat surface of the part, or worse a chamfer in the groove. The chamfer or radius, acts as a cam, closing the clip, causing it to disengage from the part freeing the pin. Then very bad things happen.
The clip not being fully engaged should be caught, they should have some type of gage to physically check each ring minimum gap after installation.
I believe for that to happen one clip ear would have to be out of the groove and there is excessive play between the clip and the retainer plate. The book calls for no play at the plate and is an interference fit. I just find it hard for a fully engaged circlip to pop out of the groove on its own. Clips are usually made from carbon steel or SS and the loads on them are usually in shear against the clip side which in the pin/bush/plate tolerances it would require the clip to shear or bend mid-span. Even if installed backwards in my view. Now if a portion of the clip is barely engaged or out of groove it could pop rather easily. Have lost enough circlips this way when installing them or my pliers slipped out the ear hole. Either way I would think there was a QA issue as well as a maintenance issue for this to happen.
Checkout_my_Six
Touchdown! Greaser!
where is He.....did he come back? 
PaulS
Touchdown! Greaser!
Pretty much, internal.
PaulS
Touchdown! Greaser!
where is He.....did he come back?
Who?
nrpetersen
Line Up and Wait
A hangar partner's '49 Bonanza blew its RH main gear strut cap off, making a big pimple in the top wing skin. Again it was the slight chamfer radius side that was out. I saw it happen. The environment around a crank damper pin is pretty severe. The exact shape of the snap ring groove is obviously very critical too.
On the other hand, would you really want a special aircraft "quality" ($$$) snap ring that has been ground sharp on both sides vs a standard stamped part that is simply installed correctly?
On the other hand, would you really want a special aircraft "quality" ($$$) snap ring that has been ground sharp on both sides vs a standard stamped part that is simply installed correctly?
As far as I know, the engines and parts are made in the USA. Has that changed?
It hasnt. Its owned by Chinese - but so is a bunch of other aviation companies, so people are making a big thing about it etc etc etc. but my understanding is the engine plant is still located stateside.
FWIW: While I suppose its possible to have a snap ring/circlip with 2 sharp edges, all the aircraft "quality" clips I've ever used have only one sharp side per the applicable MS or NAS specs. As to cost, I think that would be more specific to where purchased. A quick check on the clips in questions shows a cost range from $0.44 to $1.94 each.
Just to keep the context...
As the plant is is still in Alabama, the errors were done by a 美国人
My employer was the so-and-so that sold it to them.
As the plant is is still in Alabama, the errors were done by a 美国人Just to keep the context...
My employer was the so-and-so that sold it to them.
lol and i totally understood that lol
NoHeat
Final Approach
The Service Bulletin MSB23-01 came out today. Estimated 2000 engines affected. Only those engines with less than 200 hours are affected; they are allowed just 5 hours to reposition the plane.
Inspection involves removing odd-numbered cylinders and using a special tool to determine if the retaining ring was seated properly in each counterweight. Estimated time per engine for the inspection looks to be somewhere up to about 30 hours.
Repair instructions appear to be done without removing the engine.
MSB23-01.pdf can be downloaded from link below; it includes a list of serial numbers:
http://continental.aero/support/service-bulletins.aspx
Inspection involves removing odd-numbered cylinders and using a special tool to determine if the retaining ring was seated properly in each counterweight. Estimated time per engine for the inspection looks to be somewhere up to about 30 hours.
Repair instructions appear to be done without removing the engine.
MSB23-01.pdf can be downloaded from link below; it includes a list of serial numbers:
http://continental.aero/support/service-bulletins.aspx
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So, if you’re at 196 hours you can reposition the aircraft for 5 hours to do the inspection, and then not need to do the inspection.
NoHeat
Final Approach
If you've been intending to make an appointment at a shop for something else, I'd do it right away. This inspection of 2000 rather new engines, each requiring more than half a week of A&P time, is gonna be a real demand on shop time.
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Steamflyer
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Steamflyer
The MSB explains why the snap ring it not ground sharp on both sides.
It's odd side cylinders, but only 1 for 360s, 2 for most others, and all three on the right for the geared engines (presumably they have more torsional damper weights being geared).
Pinecone
En-Route
Did you read the SB?
NOT 2000 engines, there is a 1 page list of specific serial numbers that are affected.
My copy of Appendix 1 has 24 pages of affected engine serial numbers? At least its under warranty. But not something I would wish on anyone having to tear into a "new" engine.
The fact that a clip or washer needs to be installed with the radiused side in is hardly an odd concept on panes, but still it gets done wrong all the time. We found some idiot in the past (before I bought my Navion) had done similar to a reinforcing washer on the nose gear retraction assembly of my plane causing the casting to crack.
PaulS
Touchdown! Greaser!
Lol, good point.
Pinecone
En-Route
If that was the issue, they would have them removed and installed properly.
But all that is required it to check the gap between the ends. So the ONLY issue is they are not properly seated.
PaulS
Touchdown! Greaser!
You are the second person to say this, I read the whole thing and couldn't find why the snap ring isn't flat on both sides. Could you quote it here with a page number?
Steamflyer
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Steamflyer
From TCM Standard Practices manual. Somewhere else there was an explanation as to why the rounded or chamfered side should face in, but here at least is the prescription to do so.
Page 10-86 of April 2016 manual. Don't know if this the most current version. YMMV.
NoHeat
Final Approach
Dumb question: Why don't they just cast the counterweights into the crankshaft itself, instead of adding separate pieces that must be attached?
Answered in Post 35.