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#11
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There are bolts that should have been retorqued at a certain hour.
The shop would have specified which ones. No one I've talked to has heard of this schedule with regard to the case bolts. Have you got a Lycoming reference for this? Understand this. If the case is fretting, as it does when bolts are loose, it's a very serious situation. If this were my engine, I would have another mechanic check the torque of the through bolts. What are the "through bolts"? Are these the bolts I'm talking about, or different ones? Do Not Fly This Airplane. Too late. We torqued everything to spec, and flew it uneventfully for half an hour, at all throttle settings, at altitudes up to 4000 feet. No leakage noted, all six bars on the JPI engine analyzer looked fine, everything sounded and ran perfectly. If wet, the engine needs to be pulled and the disassembled, cases sent out and reassembled. What do you mean by "if wet"? Thanks, -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#12
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On Thu, 10 Feb 2005 16:39:48 -0500, "Gene Kearns"
wrote: snip This should be expected and the bolts should be checked at annual. If not, fretting corrosion can take a *real* toll on the case. I strongly disagree. Annual is often enough.... unless "on condition" becomes necessary. I strongly disagree. They shouldn't have been *that* loose, but they should have already been checked. I wonder if they were *ever* torqued properly. The #1 cause of leaking cases (that were correctly assembled) is letting the case bolts get loose. Now this I'll agree with, maybe. I cannot honestly remember EVER having to re-torque on the case bolts on a Lycoming. Have come across a few leaky spine seams, NEVER had one caused by any/all the bolts being "loose". Then again, I've only allegedly personally witnessed around 70-80,000 hours (conservative estimate) of Brand L operation from the perspective of an alleged maintenance technician, so WTF do I know. The only periodic "re-torque" on recips that I have been exposed to is on cylinder base studs on radial engines. BTW, only ever had one "properly" overhauled Brand L engine not make it to TBO that I've hung on an engine mount and then regularly maintained. Maybe I wuz just real lucky. TC |
#13
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#14
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On Fri, 11 Feb 2005 03:30:22 GMT, "Jay Honeck"
wrote: There are bolts that should have been retorqued at a certain hour. The shop would have specified which ones. No one I've talked to has heard of this schedule with regard to the case bolts. Have you got a Lycoming reference for this? No, your rebuilder should have it. May be 10 hours or so. Understand this. If the case is fretting, as it does when bolts are loose, it's a very serious situation. If this were my engine, I would have another mechanic check the torque of the through bolts. What are the "through bolts"? Are these the bolts I'm talking about, or different ones? I think you're speaking of the case bolts. The through bolts go all the way through the case near the cylinder bases. If the case bolts weren't done properly, there's no reason to believe the through bolts were, either. Do Not Fly This Airplane. Too late. We torqued everything to spec, and flew it uneventfully for half an hour, at all throttle settings, at altitudes up to 4000 feet. No leakage noted, all six bars on the JPI engine analyzer looked fine, everything sounded and ran perfectly. You'll not see anything special on the engine analyzer. Ask if they retorqued the cylinders and through bolts. Not a hard job, but very time consuming removing all the junk around the engine. If wet, the engine needs to be pulled and the disassembled, cases sent out and reassembled. What do you mean by "if wet"? Signs of further leakage. Thanks, Stay safe, I may need a room one day! |
#15
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Too late. We torqued everything to spec, and flew it uneventfully for
half an hour, at all throttle settings, at altitudes up to 4000 feet. No leakage noted, all six bars on the JPI engine analyzer looked fine, everything sounded and ran perfectly. The point I'm trying to make is it appears that some bolts being torqued have been overlooked and what is the chance that the cylinder nuts & thru bolts had been overlooked also? Simply, You don't know until you check. It'll require 10 minutes if you have easy access to the engine. Cylinders may run for a while but can start working on the crankcase, break one stud then the others follow in quick succession then the cylinder departs the engine. Some instances it may appear that the connecting rod broke first to cause the damage, but actually the cylinder left first and the rod broke after. I don't have the link handy, but Sacramento Sky Ranch website has a bunch of information. Good chance that is just the spine bolts and you'll make TBO. Take care Kent Felkins |
#16
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The point I'm trying to make is it appears that some bolts being torqued
have been overlooked and what is the chance that the cylinder nuts & thru bolts had been overlooked also? Simply, You don't know until you check. It'll require 10 minutes if you have easy access to the engine. I'm having my shop check these this morning. To those who think that the bolt might have been loose from the start, remember: I watched the shop build this engine, and I personally saw them check the torque on the engine case bolts. They *were* tightened to spec. I also know that they never re-checked them, however, and my main mechanic has admitted that they never check these as a matter of course. In the case of the O-540, anyway, the case bolts are torqued surprisingly low, and they are not secured in any way. No cotter pin, no safety wire, no LocTite, no lock washer -- NOTHING prevents those nuts/bolts from loosening over time. It seems like a ridiculous over-sight, but that's the way it is. A guy on the Cherokee Chat actually had a case bolt FALL OUT after loosening over time from vibration, so this is not an unheard-of problem. I'm surprised it's never been addressed in this forum before -- at least not in my 7 years here. I've bought a torque wrench, and I'm going to be checking ALL of these bolts every time I change the oil, from now on. -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#17
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"Jay Honeck" wrote in message news:6q3Pd.63958$eT5.59714@attbi_s51... I've bought a torque wrench, and I'm going to be checking ALL of these bolts every time I change the oil, from now on. -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" You may want to check with your mechanic about this also. I think the proper way to check torque of a bolt is to loosen it first and then re-torque. This could lead to case-cracks after multiple sessions. The best method of checking might be the "tamper stripe". Have your mechanic apply it after torque and then just examine it at oil change. Allen |
#18
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Allen wrote: You may want to check with your mechanic about this also. I think the proper way to check torque of a bolt is to loosen it first and then re-torque. Nope. Just buy a modern wrench, set it to the bottom end of the proper torque range, and try to tighten the bolt. If the wrench "clicks" without the bolt turning, you're good to go. If the bolt turns first, call that to the attention of your mechanic. George Patterson He who would distinguish what is true from what is false must have an adequate understanding of truth and falsehood. |
#19
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"Jay Honeck" wrote in message news:6q3Pd.63958$eT5.59714@attbi_s51... To those who think that the bolt might have been loose from the start, remember: I watched the shop build this engine, and I personally saw them check the torque on the engine case bolts. They *were* tightened to spec. I also know that they never re-checked them, however, and my main mechanic has admitted that they never check these as a matter of course. Now, I am not an A&P, but is it possible that when the bolts were torqued that they needed to be torqued in a particular order, reminiscent of tightening lug nuts on a wheel? Sometimes when tightening several bolts, the action of tightening later bolts causes the first bolt to become loose. In this scenario, the last bolt is torqued correctly and the first bolt is fairly loose. Just thinking here.... -Trent PP-ASEL |
#20
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Jay wrote, "I've bought a torque wrench, and I'm going to be checking ALL of
these bolts every time I change the oil, from now on." Jay, I'm sure you know this from your motorcycle Zen days, but I've learned (and relearned a couple times) to be certain the click-type torque wrench setting is correct before using it -- and to loosen it completely before putting it away. (Maybe the latter is an old wives' tale.) I've also learned to be careful to note whether foot-pounds or inch-pounds is specified. It seems that aircraft bolts are often torqued considerably less than I would expect them to be. Regards, Jon (not an A&P or even a motorcycle mechanic) PS: I shall now be checking my engine's bolts. Thanks for the heads up! |
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