It still doesn’t make sense.
Anyway, surely the sensible way is to forget that silly test tool, extract the Lycoming bushings and replace them with Superior ones.
Peter wrote:
Anyway, surely the sensible way is to forget that silly test tool, extract the Lycoming bushings and replace them with Superior ones.
If money is an infinite resource to you… Also pressing those bushings into the rod is not something I would gladly let Joe Average A&P do.
If you find a bad bushing when performing the inspection and test, you have to replace the entire connecting rod assembly. You are not squeezing out the bushing and replacing it with a new one. Replacing a connecting rod is not horrifying, but there are things that need to be done correctly.
There will be no field repairs to this. I would not call this test tool silly. Lycoming made it for this purpose and is betting peoples lives with it. We have 4 aircraft go down with this SB then AD. Of the four aircraft affected, only two needed replacements. Prior to this, we did have an aircraft with a catastrophic engine failure earlier in the year. Small end connecting rod failed during flight, and engine was manufactured during this time frame…… There were some pretty big events that happened to cause this.
Thanks NeumannJ; I didn’t realise this. The conrod reinstallation isn’t trivial due to the big end bolt torque. You think the engines will need to be opened up? It’s going to be very expensive…
Given that Lycoming assume the work can be done in 3 hours per cylinder, if I read that table correctly, the work is likely done with he engine in place.
As expected, EASA has adopted the FAA AD and now European Lycomings are grounded, too: https://ad.easa.europa.eu/ad/US-2017-16-11
Given that Lycoming assume the work can be done in 3 hours per cylinder, if I read that table correctly, the work is likely done with he engine in place.
For sure, although by the time you have stripped off all the stuff which enables the cylinders to be removed, the extra work in attaching a crane and pulling the engine off is not great. Shipping it to an engine shop is a lot of extra hassle though, which is why most people choose a local shop even if it has a crap reputation (overhauls actually being just new cylinders + crankcase paint, in one central European case I know about) because then you just chuck it in the back of a van, sitting on a few old car tyres.
The estimated 12 hours is quite a bit off. We were doing them in about 16 hours. Two 8 hour days.
The inspection can be with the engine still mounted. It would take longer to completely remove the engine, and ship it out to an overhaul shop for inspection. For the inspection, the cylinders need to come off and the piston. The test is pretty straight forward, attach the spring tool to the small end of the rod, tighten it down to the specified turns and see if there is movement. I have seen small movement of .005 inches and was told some are being pushed out with finger pressure only. w
When you open up an engine, you have to keep the preload on the through studs. Replacing a connecting rod is not too awful. There is a “stretch torque” that needs to be performed.
Removing a cylinder in my Cessna is very straightforward. A few oil lines and sensors. Removing the engine would add at least 12h each time.
This statement from Lycoming was posted on a US site:
