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

Buzz J 11-04-2013 09:31 AM

A better solution needed!!!
 
Cowboy and all others, I totally agree that there has to be a better solution than four more pounds of torque, loctite, & even self 'engineered' nordlocks to ensure that these critical bolts don't back out!! Certainly, we will, religiously, do 25 hour inspections and check torques (which means bolts have to be removed completely to re loctite them.... removing, by the way, the carbs each time and replacing the 'O' rings between the drip pans and the intakes...to do it right)! But, I strongly suggest that there has to be be a better way to secure these critical bolts than what is being recommended! I guarantee that our aircraft values and Vans very good name will suffer greatly should an accident or incident occur due to this issue! None of us want that to happen. I'm not one who panics or cries wolf...But, come now, gentlemen, there has to be a better way!!!!!!
Buzz

JBPILOT 11-04-2013 09:49 AM

Buzz - -
 
Since the 30# memo came out, those who have used 30#, dry; 30# with special locking washers; or like myself have used 30# with Loctite 'blue', no one has reported a problem. I think that is good enough for most of us. If ANYONE reports a problem using one of these 3 options reports a problem, then further examination might be in order. I have nearly 600 hours, and do not worry about them ANY now. Make a mechanical lock if you feel better piece of mind.

Buzz J 11-04-2013 10:30 AM

Strong disagreement...LOCK TIGHT SOLUTION REQUIRED
 
I appreciate your comments and assurances, John. But, I strongly believe that this is an issue that needs to be addressed AND SOLVED once and for all by a well engineered, totally respected by all, PERMANENT (as possible) SOLUTION to this critical matter! Let me be clear...We do not want a loss or even an appearance of neglect to address an issue such as engine cap screws that are critical to our aircraft safety...and peace of mind! As my family and good friends, one who strongly advocates for our cause in the U.S. Senate, view these discussions, they say as I have stated, "Come on guys, get a better solution...Put this to rest once and for all...in the interest of safety (Let's err on that side, please!) and gain the respect of the aviation community and the general public!!!!!" Secure, LOCK TIGHT, not Loctite) solution required! Then peace of mind can be achieved and we can move on!

Buzz

rvbuilder2002 11-04-2013 10:51 AM

The only way to begin working on resolving a problem is to have detailed information that allows it to be determined if there is actually a problem.

As already mentioned -
I am unaware of any reports of loose bolts within the past two years (until this most recent one).
It is still unclear with this one recent report, whether the bolt torques were checked at the initial 25 hr inspection and then at the 100 hr / condition inspection(s).

BTW, specifying proper torque value was only part of the correction.
Early engine mounts had powdercoat on the surfaces under the bolt washers, and on the surfaces that are in contact with the engine case.
Powdercoat is a soft (compared to 4130 steel) material that can compress over time, reducing the stretch load on the bolts.

Buzz J 11-04-2013 11:44 AM

A Strong Lock Tight Mechanical Connection JUST MAKES SENSE!
 
IT JUST MAKES SENSE to have a strong, mechanical connection to eliminate the risk. Why the the resistance to something that just makes sense, Scott and John? Eliminate the possibility of error and risk! It just makes sense!

Buzz

rvbuilder2002 11-04-2013 12:13 PM

Quote:

Originally Posted by Buzz J (Post 822926)
Why the the resistance to something that just makes sense

Ok, here is one.
The torque value specified by Rotax for the bolts is for dry threads.
A liquid thread locker acts as a lubricant during installation.

Rotax doesn't spec a torque range allowing you use a value at the low end to compensate for the additional stretch load that would be applied using the standard torque value with lubricated threads.
The bolts are threading into aluminum threads in the engine case.
If the higher stretch load damaged threads inside the expensive engine case, an RV-12 builder would be (understandably) upset.

Captain Cowboy 11-04-2013 12:49 PM

My question to all this is, " As it is extremely important to secure the engine mount to the airframe with bolts/nuts that are saftied with cotter pins, why is it NOT as important to have the engine cap screws saftied to the engine case, especially, considering that a significant amount of the entire aircraft vibration is generated from the engine and translated to the airframe thru these 4 cap screws and the attach points on the same engine mount, especially when also considering that not only vibration affects the torque and stress on these screws but so does thermal expansion/contraction issues between two dissimilar metals that the screws and case are made of????" I love this site, in the last week after discovering that only 75 percent of my Rotax 100 hp (really on about 95 hp) was attached for some time to my airplane, I am glad that there were initially 4 bolts used, however, what would have happened if initially only 2 bolts had been used in the design or, 2 of the 4 had backed out completely!!! Redundancy is a key ingredient in aviation safety. I see little redundancy with this cap screw usage!

rvbuilder2002 11-04-2013 02:31 PM

Quote:

Originally Posted by Captain Cowboy (Post 822948)
My question to all this is, " As it is extremely important to secure the engine mount to the airframe with bolts/nuts that are saftied with cotter pins, why is it NOT as important to have the engine cap screws saftied to the engine case, especially, considering that a significant amount of the entire aircraft vibration is generated from the engine and translated to the airframe thru these 4 cap screws and the attach points on the same engine mount, especially when also considering that not only vibration affects the torque and stress on these screws but so does thermal expansion/contraction issues between two dissimilar metals that the screws and case are made of????" I love this site, in the last week after discovering that only 75 percent of my Rotax 100 hp (really on about 95 hp) was attached for some time to my airplane, I am glad that there were initially 4 bolts used, however, what would have happened if initially only 2 bolts had been used in the design or, 2 of the 4 had backed out completely!!! Redundancy is a key ingredient in aviation safety. I see little redundancy with this cap screw usage!


Redundancy comes in many forms. Sometimes it is by means of inspection, so I have some questions of my own.

Do you know if the engine mount you currently have installed has no powdercoat under the bolt washers, or on the faces of the mount lugs that butt up to the engine case?

Can you confirm that the torque of all four bolts was done to 30 ft lbs when the engine was originally installed?

Can you confirm that the torque of all four bolts was checked at an initial 25 hr inspection and then at subsequent 100 hr / condition inspections?

I do not ask this as a point to transfer blame, but to try and establish whether the installation and inspection requirements have been met, and make a determination of when the bolts might have begun to get loose.

Buzz J 11-04-2013 03:31 PM

Same question...doesn't it just make sense?!
 
Why the resistance to something that just makes sense?! A mechanical connection to ensure that would certainly put the redundancy issue, and this whole issue to bed...May we rest in peace! No one is interested in pinning blame on anyone. No finger pointing going on here. But, Cactus Cowboy is right! Let's seek a true mechanical solution to ensure, not merely hope for a true redundancy factor FOR SAFETY SAKE and for peace of mind, rather than dance! Lots of unnecessary dancing going on, it appears, and unnecessarily so! A great deal of resistance! Im surprised! We're fans, not those on an opposing team!
With all that being said, at this point in time, we're being left with four (4) more pounds of torque (30 total) and no powder coat and 25 hour inspections to be sure our rational holds water...And the builder "fixes" like using Loctite and/or Nordlock washers, that many have and will use, should not be used?! Talk about transferring blame! All these other builders were, obviously, greatly concerned since they designed there own solutions! Same question... Instead of all this time being wasted flapping our jaws, why not lead the way, Scott, by listening to Cactus Cowboy's concerns...and to the usually silent majority...and design a mechanical solution that equals the redundancy of the other mounting bolts? It only makes sense!!!!!
Buzz

rvbuilder2002 11-04-2013 03:43 PM

Ok Buzz J,
I was actually try to help... by asking for some information that could be used to look at the issue, and I have giving you valid answers to your questions, but I can see this is going to get no where here, so I suggest you use the prescribed RV-12 service difficulty reporting process, and voice your concerns.
Anyone can use that process and not have to be the silent majority. No one outside of Van's engineering will know that you said anything.


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