VAF Forums - RV-12: Engine Mounting Cap Screws Inspection

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- - RV-12: Engine Mounting Cap Screws Inspection (https://vansairforce.net/community/showthread.php?t=65020)

Quote:

Originally Posted by Mich48041 (Post 490346)

There are two main issues:

ISSUE 1. Notify RV-12 owners that the engine mount bolts are loosening and falling out.
This is a moral issue. Most of us would like to see RV-12 owners immediately notified to check the bolts. Until then, bolts are slowly vibrating out. RV-12 owners who have had engine bolts loosen can warn others by contacting aviation magazines and the EAA and the FAA. If the magazine editors received letters from several builders, they might write an article or publish the "letters to editors". The word will be spread.

ISSUE 2. Preventing the bolts from loosening.
Split ring lock washers do not work as evidenced by laboratory experiments and RV-12 field experience. It would be nice if we received official guidance on this issue. But manufacturer's do not know any more about solving this problem than the builders. Regardless of engineering theory, it is what works in the field that counts. Rotax mechanics have been using blue Loctite with success, even though they might be reluctant to officially recommend it due to liability concerns. And using blue Loctite seems to be the consensus among RV-12 builders. Nothing is perfect and Loctite has disadvantages. It has temperature limits, should not be disturbed by periodic torque checks, and makes removing bolts difficult. But it works and will keep the bolts from loosening. Another possible solution is using Nord-Lock washers. They work well holding the brake and propeller bolts. Nord-Lock washers are not affected by normal engine block temperatures; they can be periodically checked for torque; and the bolts can be easily removed with a wrench. But regardless of theory, they need to be proven in the field.

We can complain and try to influence others but we can not control what they do. What we can do is spread the word to other builders, perhaps with the help of national and international media. And we can ensure that our own engine mounting bolts do not come loose.
Joe

Joe,

You have it nailed. Number 2 is easier than number 1. I, for one and others I know of are testing the Nordlock theory. Others, Loctite. I expected us to be the beta testers because as you say, "we are the field" and that is the way experimental aircraft are made safer. Your number 1 is very puzzling because it could save lives. We can only contact those we know of. Others have much larger resources to get the message out. And when you realize that many of them are readers and contributors to this forum its stunning. The EAA alone participates in this forum and yet ignores this issue. Are they all waiting for Van's to bless their comments? This is experimental, grass roots aviation, not corporate politics. Of course if you think about it, safety issues only become issues following fatalities. Shouldn't be much of a wait. Thanks for your personal concerns.

I have been thinking about this problem really hard of late. I have on hand the Nord Lock washers and both blue and red Loc Tite, and debating which to use.

Fortunately the real harm done so far is only to Van's reputation. I have been a customer since 1993 (I think it was) when I began building an RV6A, and now the RV-12, and in all that time I genuinely believed Van's organization was an honest and forthright organization. This current departure from their highly regarded (and deserved) reputation is really strange. Unless something is done promptly to repair this self-inflected harm it is going to take a long time to undo the damage.

Its only my opinion, and just like belly buttons, we all have one.

I would NOT recommend RED Loctite. It takes lots of heat to get them out, and that may create other issues. I'd again suggest BLUE, and check them often as you feel comfortable. After this morning, I am now at 209.9 hours. They seem to be fine. As I have also said, I have around 100 hours on them, and they have not moved. If we find the nord-lock washers to be good also, fine, use BOTH. You could take them out if you want/need to, but could fly with confidence they are not going to fall out.

John Bender

Notify Email From Vans!

I just received a Notify email from Vans containing the info about the mounting bolts. So now the info is going out to all owners.:D

I have learned that

In life, when common sense and practicality 'appear' to have been left behind, that there is a lawyer is involved.

Quote:

Originally Posted by Jetguy (Post 490376)

I just received a Notify email from Vans containing the info about the mounting bolts. So now the info is going out to all owners.:D

It's good that they have finally notified owners by email, but you have to wonder why it has taken them nearly two weeks to get around to it. The service notice on Van's website is dated 19 Nov, just two days after Larry G first reported the problem here. I've had great service from Van's ever since I ordered my kit, but this apparent lack of urgency is a puzzle, given the potentially catastrophic consequences of losing these bolts.

Incidentally, they have just issued revision D of page 46-06 in the RV12 section on the website.

Bolts slightly loose at 20 hours

Just finished checking the bolts and modifying the engine shroud on N143WM at 20.1 hours.
All bolts were torqued to 310 in-lb PER THE RV-12 MANUAL at installation. At 20.1 hours all bolts required 10-15 deg of turn to go back to 310 in-lbs. I removed all the bolts, inspected them, coated them with lots of blue Loctite 243, reinstalled them and torqued them to 360 in-lb. All bolts were torque marked so I can see if they've moved at "regular" intervals, whatever "regular" comes to mean. I increased the size of the slot in the shroud so the upper left bolt could be removed. I did not remove the powder coating inside the mount since it hadn't been mentioned at the time and I'm not sure how it can be done with the engine in place.

After removing the lower right bolt it could not be reinstalled until enough pressure was put on ther arm of the mount to flex it down almost 1/16 inch. A friend whose entire career at Wright-Pat says that the problem is due to something in the structure flexing in the right way to set up a resonant frequency-- possible the lower right motor mount arm? That's the only bolt that did not go right back in.

The real problem, and one I'd think the whole LSA community would be VERY concerned about, is that the ONLY structural fasteners in the whole airplane that DO NOT have self-locking nuts, cotter pins, or safety wires are the 4 bolts holding the engine on! Is that ASTM standards??? If so, then I think the first time the FAA finds the engine of an RV-12 a half-mile from the crumpled wreckage, the result will make the CH-601 ruckus look insignificant!

My feeling is that the real solution may be a re-designed motor mount with a way to safety those 4 bolts.

Wayne 120241/N143WM

E-mail notification

Well maybe only to those with an engine, I have only the Empennage kit, no e-mail from them and I know they have it, but it makes sense as I don't have an engine yet.

Quote:

Originally Posted by rgmwa (Post 490463)

All Four Capscrews Retorqued to 360 in-lbs

Finished checking all four engine mounting capscrews. At 85 hours, found three of the four slightly loose. Was able to get about 1/8 of a turn on the three. The fourth (one of the lower ones) need not budge at 310 in-lbs.

Van's tells you to use a ball end 8mm allen to get to the upper right capscrew. My drip tray was squarely in-line with the capscrew head and as such I had to remove the right side carb, the right side carb flange and drip tray. The o-ring popped out. It had swelled in diameter. It was not crushed. Could not get it back in the slot. Have another on order from LEAF. $6. Suggest having one on hand if you decide to remove the flange and drip tray. It also could have been my o-ring and how it reacted to alcohol free gasoline.

Felt I would get a better torque, and minimize any capscrew head damage if I was square to the capscrew head and had full allen wrench engagement?? A little more work but not hard and I felt better.

Did all of you guys that have checked the upper right have to REMOVE the drip tray??

The o-ring will be here Tuesday or Wednesday. No real problem as we got 7" of snow in the last 24 hours.

Quote:

Originally Posted by clucier (Post 490652)

Well maybe only to those with an engine, I have only the Empennage kit, no e-mail from them and I know they have it, but it makes sense as I don't have an engine yet.

Same here, Chris. I haven't received an email, but then haven't ordered my engine yet either. I hope that by the time I do, Vans and Rotax will have got their heads together and come up with an official fix.