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

jersey 11-23-2010 08:43 PM

Modify Cowling
 
This is a serious problem!!!!!

Found upper left and lower left bolts finger tight. I removed all bolts and reinstalled with locktite blue. Cut a section of the cowl out to access the upper left. Reinstalled the cut out with nut plates and aluminum tabs for future inspections. I don't fully trust it yet. If anybody is interested, I will be glad to send photos via email.

Gary

JohnF 11-23-2010 09:03 PM

Cut Out Photo
 
Gary, would you consider posting photo of how you make the 'cover' over the cutout that you make to inspect that one awkward to get at bolt? thanks

MartySantic 11-23-2010 09:46 PM

Quote:

Originally Posted by jersey (Post 487641)
This is a serious problem!!!!!

Found upper left and lower left bolts finger tight. I removed all bolts and reinstalled with locktite blue. Cut a section of the cowl out to access the upper left. Reinstalled the cut out with nut plates and aluminum tabs for future inspections. I don't fully trust it yet. If anybody is interested, I will be glad to send photos via email.

Gary

You better believe this is a SERIOUS problem. This issue is more than 1 week OLD and the only notification to those that have flying RV-12s has been via this website. This is indeed a SAFETY of FLIGHT issue, as mentioned in the initial post, and notification to ALL RV-12 owners HAS NOT but should have been made by now. Many have found at least 1 capscrew loose. At least three or more have been flying with 2 of the 4 capscrews loose or missing.

A periodic inspection is NOT an acceptable solution because the condition has been discovered between the required 100 hour ROTAX inspection points. As such, the required inspection MUST not be counted on, a critical situation may develop between the inspection points!!

Statistics dictate this is indeed a major problem. There are NOT that many RV-12s flying!

IMHO, notification to all is much more important rather than trying to find a solution and issuing the notification concurrently with the solution. We can try to notify all via this website, but, Van's has the complete list of RV-12 owners.

Please continue to report your findings to Van's at:

engineering@vansaircraft.com
with "SAFETY ALERT" in the Subject Line

LIMA HOTEL 11-24-2010 06:23 AM

I think the best solution for this problem would be to use the same kind of lock washers under the engine mount cap screws as we use under the prop attach bolts. Lets see what Van's comes up with.
Larry

okiejohn 11-24-2010 07:01 AM

Suggestions
 
I tightened the bolts at 25 hours and at nearly 100 hours I had 3 bolts loose.
Yes, I torqued them and i checked them at the 25 hour oil change, but not the inaccessible one. I erroneously assumed if it was covered up, it meant that access was not required therefore it would stay tight.

I think if you are getting ready to rtv your cooling shroud down, you should either:
1: wait for Vans to come up with a fix
2:moto- tool a slot that you can get a balldriver into to get to the left top screw. Then fiberglass a trough in so you can still get to the screw without leaking air.

If you wait till you get your engine in about the best you can do is rtv an aluminum cover.

I theorise that the tough steel of the engine mount might be as hard as the lockwashers and they don't get a good bite. Van's is so far against the blue medium strength locktite, but the technician at LEAF said it would work good and he recomended it. Without locktite, you need a short inspection interval.

I am not negative about this. With 400 RV-12s flying soon, we will be the largest fleet of new small airplanes, and any safety issues will be communicated on VAF.

jersey 11-24-2010 07:23 AM

John I think your right about the lock washers not performing. I noticed that the engine mounting bracket arm was flexing slightly when I was aligning the bolts. Although they firmed up when I tightened the bolts to the engine it would seem that they shouldn't rely solely on the engine case for rigidity. This is a high speed, high compression engine. It seems to me that a significant amount of energy retention would be concentrating where the brackets clamp to the engine. I'm probably over-analyzing. Hopefully Vans engineers will get back to us soon. In the meantime I will continue to inspect the bolts and enjoy the plane.

Gary

MartySantic 11-24-2010 09:49 AM

Quote:

Originally Posted by jersey (Post 487641)
This is a serious problem!!!!!

Found upper left and lower left bolts finger tight. I removed all bolts and reinstalled with locktite blue. Cut a section of the cowl out to access the upper left. Reinstalled the cut out with nut plates and aluminum tabs for future inspections. I don't fully trust it yet. If anybody is interested, I will be glad to send photos via email.

Gary

Gary asked me to post his photo's as he did not know how to do it. So, here are the photos of Gary's modification to the top shroud. A very eloquent change that allows access to the top left capscrew.












MartySantic 11-24-2010 10:06 AM

Quote:

Originally Posted by jersey (Post 487720)
John I think your right about the lock washers not performing. I noticed that the engine mounting bracket arm was flexing slightly when I was aligning the bolts. Although they firmed up when I tightened the bolts to the engine it would seem that they shouldn't rely solely on the engine case for rigidity. This is a high speed, high compression engine. It seems to me that a significant amount of energy retention would be concentrating where the brackets clamp to the engine. I'm probably over-analyzing. Hopefully Vans engineers will get back to us soon. In the meantime I will continue to inspect the bolts and enjoy the plane.

Gary

The following links and for that matter, the entire website is very interesting. The information and data clearly demonstrates how ineffective split lockwashers are and in some cases the bolt/joint is better WITHOUT the lockwasher. (Look at the graph).

http://www.boltscience.com/pages/vibloose.htm

http://www.boltscience.com/pages/hel...ingwashers.htm

AND the video.....

http://www.boltscience.com/pages/jun...ringwasher.htm

I sent all of this to Van's, last week.

MartySantic 11-24-2010 10:15 AM

Quote:

Originally Posted by LIMA HOTEL (Post 487713)
I think the best solution for this problem would be to use the same kind of lock washers under the engine mount cap screws as we use under the prop attach bolts. Lets see what Van's comes up with.
Larry

A very interesting article on bolt locking devices other than the split lockwasher. The NordLock washer is a VERY interesting device once understood. (No wonder Sensenich uses it!)

http://contrails.free.fr/article_bol...ng_devices.php

This was also sent to Van's last week.

JBPILOT 11-24-2010 10:17 AM

Hey Gary - -
 
EXCELLENT Patch ! Good job ! I really like it ! I did not take as much time. If I ever have to go back in, that will be my choice.

John Bender


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