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

MartySantic 05-03-2012 08:14 AM

And if using locktite, mark the 4 bolts with torque seal. If you retorque them and the bolt turns, you risk breaking the loctite seal.

BigJohn 05-03-2012 04:56 PM

Go here, look at pictures for 12/7 and 12/8. Just another way to skin the cat!

Tony_T 05-17-2012 08:26 PM

Update -- Nord Lock washers on engine bolts
 
Doing an ACI (second) and had to pull off the carbs anyway so access to the top engine bolts was pretty easy. You have to take off the drip pans to get to the bolts, so a couple of 'O' rings should be on hand.

Anyway, to the point; as previous discussed in this thread I used Nord Lock washers on the engine bolts back at 40 hours instead of using Lock Tite. My reasoning was that I really wanted to be able to put a torque wrench on these bolt to check tightness at the annual inspection rather than just look at the torque seal marks. I may be the only one who used the Nord Locks.

My latest check today which is 90 hours since the Nord Locks were installed show the bolts at full torque of 30 ft-lb. I'm happy :).

Tony

2johns 05-17-2012 08:47 PM

I also used nord lock washers with 30 ft-lbs of torque. 75 hours and still tight.

Peterk 05-17-2012 09:20 PM

Bob Kibby used the Nord Locks as well and his are fine. My lower two were loose when this first was mentioned. The Rotax Installation Manual said to torque them to 30ft/lbs instead of the 26 in the build instructions...so I did...and they are still solid 300 some hours later.

rjtjrt 05-17-2012 10:53 PM

PeterK wrote
Quote:

Originally Posted by Peterk (Post 660164)
Bob Kibby used the Nord Locks as well and his are fine. My lower two were loose when this first was mentioned. The Rotax Installation Manual said to torque them to 30ft/lbs instead of the 26 in the build instructions...so I did...and they are still solid 300 some hours later.

Pete
I am not sure if you used Nordlocks, or locktite, or nothing except increased torque (30ft/lbs instead of the 26) to achieve result ("they are still solid 300 some hours later").
Can you clarify please?
John

Geico266 05-18-2012 05:37 AM

Quote:

Originally Posted by rjtjrt (Post 660176)
PeterK wrote


Pete
I am not sure if you used Nordlocks, or locktite, or nothing except increased torque (30ft/lbs instead of the 26) to achieve result ("they are still solid 300 some hours later").
Can you clarify please?
John

Pete did not use loctite or Nordlock washers, just retorqued to 30. They have held tight.

Skunkworks 06-14-2012 08:02 PM

Found Hex Ball End Socket and Socket-Knuckle does the job
 
Able to access upper left engine mount cap screw


2johns 06-14-2012 09:18 PM

I really like nordlock washers. It takes more torque to loosen them than what you have them torqued to. If the engine mount bolts are torqued to 30 ft lbs it takes at least 33 ft lbs to loosen them. They are used on two other places on our RV12s - The mounting bolts on the propeller and the two bolts that hold the brake pads on the matco brakes. 130 hours and the engine mount bolts are still tight.

Skunkworks 06-17-2012 06:34 AM

Van's Cooling Shroud Mod 11-19-2010
 
Not sure if eveyone has see this document on modifying the cooling shroud.
Our build, the shroud seemed to be already modified. We were able to reach the engine mount allen screw in the upper left using the ball end hex driver. See previous pic's above.

Link for cooling shroud modification from Van's below:
http://www.vansaircraft.com/pdf/lett...Shroud_Mod.pdf

jtdehaan 06-30-2012 03:55 PM

Upper right bolt loose
 
During my annual inspection found the upper right bolt completely loose. This is the long engine thru bolt. Could not get bolt started in the threads. Looking in the case, saw the threads messed up. What is my option now? A heli-coil repair seems to be the only way to go.

Jake - s/n 120025 with 176 hours.

MartySantic 06-30-2012 05:29 PM

Quote:

Originally Posted by jtdehaan (Post 674911)
During my annual inspection found the upper right bolt completely loose. This is the long engine thru bolt. Could not get bolt started in the threads. Looking in the case, saw the threads messed up. What is my option now? A heli-coil repair seems to be the only way to go.

Jake - s/n 120025 with 176 hours.

You may be OK. Sight down thru the engine mount frame to the engine. You may have to put a bit of pressure on the frame to get everything aligned. Then try to install the bolting.

Bill_H 07-16-2012 03:44 PM

One more data point for what its worth. Installed the bolts with loctite and 30 ft-lbs. Used torque seal paint as an indicator. Just did my 25 hour check today - no movement of the bolts. Plus everything else under the cowl looks great! Getting ready for OSH 2012.

rv3flier 04-22-2013 08:01 AM

I just arrived home in SW Washington in my new to me RV-12 which I picked up in Stonewall, OK on Friday. On the way I thought I detected an increase in the level of vibration. I attributed it to the carbs probably being out of balance, even though the EGT/CHT's were quite close. Having just stumbled across this thread and with just 100TT on the airplane, I'm sure that these bolts are the likely problem. The first thing I'll be checking today -- and will post what I find.

rv3flier 04-23-2013 06:29 PM

Both bottom bolts were tight. Still haven't checked the top ones yet and have been looking and thinking about John Peck's mod cutting away the top part of the cooling shroud. I wonder if anyone has tried drilling the fiberglass shroud slightly larger than the cap screw diameter. It would seem that you might be able to remove and replace the bolt using 3/8" drive extension with a 6" 7mm allen 3/8" drive cheaply available from Harbor Freight. The holes could then be plugged with red RTV. Has anyone already tried this?

RFSchaller 10-26-2013 08:33 PM

For what it's worth I torqued my mounting bolts to 30 ft-lbs with no Loctite almost 2 years ago and checked them today at 110 hours. All four were still torqued to 30 Ft-lbs.

yankee-flyer 10-27-2013 01:10 PM

Ditto at 199.8 hours
 
Locktite, 30 ft-lbs, torque-marks not broken

Wayne 120241/143WM

Buzz J 10-28-2013 01:02 PM

A more permanent fix in the works?
 
So glad the 30# of torque and Loctite are doing the job. Has anyone (you engineer types, perhaps) designed a more permanent fix for these so important screws, such as, perhaps, a pin or safety wire through a very carefully designed/drilled through the engine mount on top of each screw...so it can't back out?! Just an idea. The other four engine mount bolts have castle nuts with cotter pins to give the assurance that they cannot loosen! That's real assurance! Why not a like solution for these four screws that, in spite of frequent inspections could cost us both safety and money?! The current "solutions" of inpection and Loctite to ensure that our engines stay put, especially as they age, are not enough!! There needs to be a more permanent solution than frequent inspections and Loctite to ensure safety!!! Is anyone working on such a fix? I think that this is a critical issue that needs to be solved and put to rest! Really appreciate your concern an efforts, everyone!

Buzz

Mich48041 10-28-2013 02:59 PM

It is my understanding that safety wire does not prevent bolts from loosening. The bolts loosen first, then the safety wire prevents them from backing out any further. With engine bolts subject to vibration, it is not desired for the bolts to loosen even a little.
See previous posts about Nord-Lock, aka wedge-lock, washers.
Joe Gores

RFSchaller 10-28-2013 09:42 PM

Buzz,

The 3/8" bolts are in tension and the mounting bolts are in shear. The 3/8" bolts experience the forces along the axis which tends to loosen the nuts. The mounting bolts normally wouldn't be expected to loosen in shear. My guess is that's why the cotter pins are only on the 3/8" bolts.

Rich

Captain Cowboy 10-31-2013 07:55 AM

Engine Cap Screw inspection
 
In doing my conditional, 10/30/2013, found upper right engine mount cap screw totally out of hole and wedged against engine support, 60 hours total on eng/frame. Will check othes soon, aircraft grounded immediately!!!! Every flying 12 needs to be looked at now before a more serious problem results. There needs to be a Service Bulletin issued NOW that applies to all flying 12s with Rotax/Vans ELSA combination aircraft! Additionally, an Engineering permanent solution needs to be completed and disseminated to all 12 owners!!!!!

JBPILOT 10-31-2013 07:59 AM

Hey Doug - -
 
I am sure you did not use locktite blue. If you use 'blue' and 30#, you will NOT have another problem. Put torque paste on them, and NEVER touch them again. JUST LOOK at torque seal.

Captain Cowboy 10-31-2013 08:16 AM

Will do John, I also think that an SB with recurring compliance needs issued to educate those that have not had any problems yet but may in the future! Thanks

rvbuilder2002 10-31-2013 08:56 AM

Quote:

Originally Posted by Captain Cowboy (Post 821593)
Will do John, I also think that an SB with recurring compliance needs issued to educate those that have not had any problems yet but may in the future! Thanks

Checking the torque of these fasteners is included in the 100 hr inspection check list, so they should be getting checked during every engine inspection. On new engine installations, a 25 hr inspection is prescribed. The 25 hr inspection uses the exact same check list as the 100 hr, so the engine attach bolts should be getting checked at that time also.

Because of the above inspection intervals, a SB is not necessary.,..

It has now been more than 2 years since this problem originally surfaced.

A couple of details were changed that resolved the issue -
1. Corrected the torque value for the four bolts to 30 ft lbs (incorrectly spec.ed at 26 ft lbs)
2. Deleted powdercoat from the engine mount where it contacted the engine and fasteners (possible torque value drop off because of compression of the powdercoat).

There is now more than 280 RV-12's flying and yours is the first loose bolt issue I have heard of during that 2 year period.
Two years ago, some owners/builders chose to deviate from the recommended install procedure, and also used thread locker and/or locking washers.
The major majority of completions within the past 2 years have probably used the recommended installation, with no problems detected.

rvbuilder2002 10-31-2013 08:59 AM

Quote:

Originally Posted by JBPILOT (Post 821586)
I am sure you did not use locktite blue. If you use 'blue' and 30#, you will NOT have another problem. Put torque paste on them, and NEVER touch them again. JUST LOOK at torque seal.

Undisturbed torque seal is not a reliable indicator that a bolt is still fully torqued. It only indicates whether the fastener has rotated. The torque value (stretch load) of a bolt can drop off without it rotating.

JBPILOT 10-31-2013 01:10 PM

Scott - -
 
respect your statements, but until someone who has used 'blue' & 30# and reports a problem, I will stay with my method. To me it is extra piece of mind. If the bolt doesn't move, and 30# of original torque, I'm satisfied it won't be a problem. If anyone EVER has a problem and has NOT touched them after my method, I would certainly like to hear from them, and hope they post it.

Captain Cowboy 10-31-2013 04:26 PM

Scott and John, I don't just want piece of mind when we fly our 12s, I want a totally 100% safe and reliable aircraft that has the best engineering applied to its design and maintenance. That is not the case with these bolts that can completely back out in less than a year from the previous conditional and after 45 flying hours since our last conditional in Oct 2012. There has to be a better solution than adding 4 more pounds of torque and some blue loctite. We did everything according to ELSA build specs and inspections and still had the upper cap screw back out completely! It is shear luck that I found the screw still on the aircraft. The last thing we need is a hull loss because of these cap screws moving any amount. It is obvious to me that this problem has been an ongoing concern for multiple years and it NOW needs FIXED!!!!

DHeal 10-31-2013 05:01 PM

Sorry, but there never has been and never will be a "totally 100% safe and reliable aircraft". Only the politicians promise you that.

rvbuilder2002 10-31-2013 05:35 PM

Quote:

Originally Posted by Captain Cowboy (Post 821787)
Scott and John, I don't just want piece of mind when we fly our 12s, I want a totally 100% safe and reliable aircraft that has the best engineering applied to its design and maintenance. That is not the case with these bolts that can completely back out in less than a year from the previous conditional and after 45 flying hours since our last conditional in Oct 2012. There has to be a better solution than adding 4 more pounds of torque and some blue loctite. We did everything according to ELSA build specs and inspections and still had the upper cap screw back out completely! It is shear luck that I found the screw still on the aircraft. The last thing we need is a hull loss because of these cap screws moving any amount. It is obvious to me that this problem has been an ongoing concern for multiple years and it NOW needs FIXED!!!!

Doug,
As I already mentioned, yours is the first instance in two years I have heard of.
I would need a lot more information than you have given up to this point, to comment on your case.

Reread my other post (#184).
Since implementing the listed changes ~ 2 years ago, I am unaware of any instances of loose bolts. Without more information, all I can assume is there is some detail specific to your installation that caused them to loosen.

You say 45 hrs since the last conditional (proper term is condition inspection BTW). When you did that inspection, did it include verifying that the 4 bolts were properly torqued to 30 ft lbs (as prescribed in the Rotax inspection check list)?

Regarding your comment of wanting something better than 4 more pounds of torque - in the context of properly installed threaded fasteners, 4 ft pounds can make a big difference in obtaining proper stretch and preload on a fastener such as this. Many were found loose when the incorrect torque value was being used... as already mentioned, I have heard of none (until yours) since the correct torque value has been used. BTW, the 30 ft pound value is a specification from Rotax. It can be found in the illustrated parts manual.

Captain Cowboy 11-01-2013 11:43 PM

I must correct my original post, it was the lower right cap screw that came completely out! I just read every post in this forum on this subject which I should have done before posting my comments! I was totally unaware of all the problems others had, previously, with this subject and their subsequent actions. After reading all of these and consulting with a friend who is an Aero Engineer about why these bolts/cap screws move/back out, I have come to the realization that nothing will totally guarantee that these bolts do not vibrate out short of engineering a different eng mount that mechanically locks them in place after installation! I also realize that this is a costly correction for Vans, Rotax, or whoever is responsible for this mod. It is true that we in the field will ultimately solve it before all the engineers get around to it, which apparently has already happened using loctite, increasing torque, using nordlocks or other combinations thereto. I just stumbled onto this problem of mine because of reading VAF posts and looking at our aircraft!!! I never received any info from Vans or Rotax about loose cap screws or shroud mods that would have clued me into this problem, but I should have!!! As others before me have solved this Experimental problem, i will also.

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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