All points well made. I found a solution but you won't like it as it is a bit tedious in some cases.
I have found looseness in the following bolts:
The M10 Bolts securing the ring mount to the engine are torqued and many have lock washers on newer airplanes. It is rare but should I find one loose, I use 10 mm Nord-lock wedge locking washers, rather than Loctite 243 alone as called for. Nord-locks are
expensive ($25 for 20) but are very secure on steel and work especially well on aluminum. See Granger or Nord-Lock direct. The Rotax Heavy Mx Manual has torque requirements for bolt sizes used and further amplify in the specific installation of components
like cylinder head bolts.
The M10 Allen head bolts securing the Engine Mounting Frame to the ring mount using the M10 "Binx" nuts will loosen often. These nuts are particularly frustrating on the 914 near the turbo. I drill the bolt head and use .020 safety wire through the slot in
the "Binx" nut back to the hole in the Allen head. This is not hard drilling the Allen head, but I highly recommend proper security of the bolt and cobalt 1/16 inch drill bits for the chore. This is tedious with the engine on but can be done with long pliers
and a lot of patience. I may try 10mm Nord-Locks one of these times.
Exhaust nuts on the 912S are frustrating and difficult to safety wire. However, I have had luck when the whole stud comes off with the nut to simply buy new nuts, remove the old corroded nuts, clean the stud threads inspect and if good reinstall with Loctite
243 on the head side (the Loctite will fail with heat but...) Secure the stud and allow the Loctite to cure overnight. I then install the new nuts, and I will peen the nut lightly if the prong ends are not grabbing well. On one aircraft a customer drilled
the 8mm bolts through the corner for 0.020" safety wire. Very secure, but I have found my proper install and if necessary,peening of "sloppy fitting exhaust nuts" (as tolerances are not what they used to be) to be quite effective. Exhaust vibration on the
912S is demanding on the exhaust system. Pay attention to springs, the sealing points and look for soot. I've written on this in the past and still find satisfaction with exhaust sealant and lapping my joints. Springs require some silicone down the outside
and just in case I still put a loop of safety wire down through the springs to keep everything secure.
Never use a Nylock nuts forward of the firewall. In high heat they melt, and after exposure for a few years under the hood, will tend to fail. Lock washers, Nord-Locks or safety wire are best. I find Nut plates and MS210 squeeze nuts hold up extremely well
over time. Squeeze nuts, MS210 type, are very good unless reused, then proper re-peening will suffice for a temporary fix for lack of a new nut on hand.
This is why I do a 25 hour oil change and inspection. Use Torque Seal on your nuts to determine if they have loosened. That way the inspection is quite fast. If a bolt or nut has loosened apply a fix as stated above and then Torque Seal Again. Your airplane
may look like a bunch of orange or yellow dots on all the bolts, but a stitch in time saves 9 as they say.
Best Regards,
Bud Yerly
From: owner-europa-list-server@matronics.com <owner-europa-list-server@matronics.com> on behalf of Area-51 <goldsteinindustrial@gmail.com>
Sent: Thursday, December 26, 2024 2:20 PM
To: europa-list@matronics.com <europa-list@matronics.com>
Subject: Europa-List: Re: Engine mount bolt loosens
--> Europa-List message posted by: "Area-51" <goldsteinindustrial@gmail.com>
All valid; points noted.
On occasion have found bolt has loosened and departed the airframe leaving three secure in place. Why does the bolt loosen? Vibration and the sum total of heat expansion and contraction cycles of individual components. Check the flat washer used under the cap
screw heads; they should be hardened washers under the spring washers.
I now make it a routine item at 25hrs to check the torque on all 4 engine to crankcase frame bolts. Clean the thread well with brake clean and compressed air before refitting. Ensure the spacer block between crankcase and engine frame has been fitted during
installation; visual inspection with light and mirror. it cannot come out even if bolt departs the frame.
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