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Failed Canopy Gas Struts

E

Ex Bonanza Bucko

Well Known Member
I have had the plastic rod ends on the gas struts on my canopy break three times; the upper end breaks off apparently due to stopping the canopy as it opens. That shouldn't happen.

Gus and Van's says that reported failures have been rare. I think that is probably because home builders have seen the bad potential of the plastic rod ends and replaced them. I have an SLSA so that is not an option....or probably isn't one.

In any case I'd like your input on this,

EBB
 
Alignment?

I'm assuming the vast majority of RV-12s are using the struts provide by Van's with the standard plastic ends and if it was a common problem, I also assume we'd be reading about it on here more often. Having several fail on the same aircraft is surprising. Is it possible that your struts are not aligned as straight as they are suppose to, and that the stress on them from opening/closing is leading them to eventually fail? Not sure how that could happen, but maybe its worth comparing how yours fit vs. another RV-12 installation.
 
Thanks: Mine are straight and I've kept them oiled since Van's told me that perhaps they are binding somehow. The first failure was at about 40 TT SN on the airplane and the second and third happened about 20 hour and about 20 flights apart after that.

I think I might chance some kind of violation and buy stainless rod ends with a bearing in them to cure the problem.

EBB
 
Have all 3 breaks been in the same mode? Pics might help a diagnosis. Having read every post in the RV12 forum over the past few years, I don't recall any similar failures and no changing of the plastic tips comes to mind. We try to place/link all such things in the Modifications sticky thread. Can you post pics?
 
Are they installed with the correct end up?
On the six, 7, and 9, the rod should be on the bottom, and the body on the top when the canopy is open for the internal valve to slow the extension speed at the last couple of inches.
 
By chance are you allowing the canopy (when opening it) to travel to the extended limit of the strut unrestrained? In other words, letting the gas strut lift the canopy open and then stop suddenly when it runs out of strut? Or, any wind/canopy related incidents that put undue force on the strut end? Not suggesting that *should* cause a failure but it potentially *could* cause one.
 
Thanks for all the help. My struts are installed correctly; they were put in there by Synergy Air/Van's because my airplane is an SLSA. I have not changed anything.

It appears to me that the problem is the plastic rod ends; one failure was on the starboard side and two on the port side. There was no wind action involved with any of the failures and I simply opened and closed the canopy gently....never violently.

I had some pictures but can't find them in my computer now....I sent them to Synergy Air and Van's after the first failure. I guess you'll have to take my word for the failures and for the correct installations.

We'll see what happens going forward but I think plastic rod ends are not strong enough under any circumstances. I also think that the canopy is inordinately susceptible to racking and that may be part of the problem.

EBB
 
Ex Bonanza Bucko said:
Thanks for all the help. My struts are installed correctly; they were put in there by Synergy Air/Van's because my airplane is an SLSA. I have not changed anything.

It appears to me that the problem is the plastic rod ends; one failure was on the starboard side and two on the port side. There was no wind action involved with any of the failures and I simply opened and closed the canopy gently....never violently.

I had some pictures but can't find them in my computer now....I sent them to Synergy Air and Van's after the first failure. I guess you'll have to take my word for the failures and for the correct installations.

We'll see what happens going forward but I think plastic rod ends are not strong enough under any circumstances. I also think that the canopy is inordinately susceptible to racking and that may be part of the problem.

EBB
Click to expand...
I've had two broken in less than 100 hours Hobbs. There was a revision that has us drill out to 3/8" (?) on one of the holes - it seemed at the time that it couldn't help but make that end of the strut weaker.
 
Littl3 Bird II has had one break

somewhere around the 200-hour mark. Always been VERY carful using what I think is a weak link.

Wayne 120241/143WM
 
EBB- I wasn't doubting you - I meant - is the break always across the hole? At the same angle? Or does the break not intersect the hole? Or are the breaks different?
 
Does anyone have a broken one that they would part with?? I won't cannibalize my flying RV-12, but I sure think that I could either come up with, or make, a replacement part out of aluminum. I think that plastic end is just threaded into the end of the strut. I do have a lathe, and minimal skills, but I sure would like to give it a try. Who knows, maybe I could make a bunch of them. Drop me an email.


Tom
 
Hi Tom,

Sounds great, but I think you will also need a mill to achieve the required shape. I think some searching on the Internet will result in finding something already made for the purpose.

Thanks, Alex
 
alexe said:
Hi Tom,

Sounds great, but I think you will also need a mill to achieve the required shape. I think some searching on the Internet will result in finding something already made for the purpose.

Thanks, Alex
Click to expand...

Yeah, I have a mill also, but if there is something out there already made, it probably isn't worth the trouble to make our own.............Tom
 
Okay!! I found a supplier for the rod ends. Now I need to have some dimensions. The eyelet can be reamed to size, and the length of the threaded shank could be shortened, if necessary. But the threads must match. Here are the most popular thread sizes:
M6 X 1.0
M8 X 1.0
M8 X 1.25

So, if someone has a broken strut laying around, and could do a little measuring, I will be glad to order a few parts, experiment with a retrofit, and post instructions, and supplier information. Then, anyone interested could make their own, and replace the plastic ends with a metal one. Sounds like a simple fix to me.

Tom
 
The dimensions on my struts are as follows:

LOA: 8 3/16"
Thrust: 2 1/2"
Barrel: 3 5/8"
Barrel diameter: 5/16"
The eye on the lower end is 1/4" and Van's replacements have to be drilled out to at least that....maybe 5/16
The eye at the upper end is sized for a 10 X 32 machine bolt.

McMaster Automotive has the rod ends for these struts for $10 +/-. Aircraft Spruce sells the same ones ("aircraft quality") for about $40 @.

I hope this helps. It would be great to get replacements that are all assembled because the originals are made in Mexico and the threads going into the rod ends are metric and hard to match in a rod end. Helicoils might be called for.

This failure should not happen. The canopy of the RV12 racks when it is opened because the upper bolt does not go all the way through and the rod ends are plastic and break. My bird is black and I think heat might deteriorate them. Who knows?

Bummer!

EBB
 
Okay guys. Thanks for the info. I also did some measuring on my struts. I found a supplier with a product that looks very good. They are called lift strut heavy duty metal eyelets. As soon as I get them, I will see what modifications are needed, if any, and when I am satisfied, I will post the suppliers name, as well as any mods, or comments. Should be a good mod.............Tom
 
todehnal said:
Okay guys. Thanks for the info. I also did some measuring on my struts. I found a supplier with a product that looks very good. They are called lift strut heavy duty metal eyelets. As soon as I get them, I will see what modifications are needed, if any, and when I am satisfied, I will post the suppliers name, as well as any mods, or comments. Should be a good mod.............Tom
Click to expand...
So Tom, how did the new metal struts worrk out?
 
I figured out what is breaking the rod ends: When you open the canopy the last foot of its rise puts a tremendous force on the rod end as the canopy's motion stops. If you are sitting in the cockpit it's almost impossible.....for me at least.....to hold on to the side of the canopy to ease its travel. If you're outside, of course, that's easy. There is a very great lever arm at work on that canopy and it will take a very strong rod end not to break out at the top. I think this needs a systemic fix by Van's; I don't think this problem is going away.

EBB
 
One must always be cautious opening the canopy toward the end of travel. Replacing the strut ends with a stronger material will move the energy to the next weakest link. Take your pick, the strut itself, the canopy fiberglass assembly or the fuselage mount assembly.
 
gossend said:
So Tom, how did the new metal struts worrk out?
Click to expand...

Actually it's great, in fact, I will be wearing a sample rod end and bushing on a necklace at the Oshkosh Social. I will also have instruction sheets to hand out to anyone interested.

Tom
 
todehnal said:
Actually it's great, in fact, I will be wearing a sample rod end and bushing on a necklace at the Oshkosh Social. I will also have instruction sheets to hand out to anyone interested.

Tom
Click to expand...

Please post what and where you can get your fix😎😎
 
canopy strut strength

I must be missing something here. First of all, I would never just turn loose of the canopy and let it fly open on its on. I gently let it travel to the fully open position before turning loose. Yes, I do this while sitting in the cockpit. When at the fully open position, their is no pressure remaining in the struts....no pressure on the rod ends or screws.
The plastic ends appear to be sufficiently strong to me.
 
Jackkclark said:
I must be missing something here.
The plastic ends appear to be sufficiently strong to me.
Click to expand...
Considering the small number of occurrences with the number of years in service of 400+ airplanes it appears that there is something situationally specific that causes it.
Even so, it has been more than just a couple of airplanes so different design ideas are being evaluated and tested.
 
rvbuilder2002 said:
Considering the small number of occurrences with the number of years in service of 400+ airplanes it appears that there is something situationally specific that causes it.
Even so, it has been more than just a couple of airplanes so different design ideas are being evaluated and tested.
Click to expand...

To have the plastic eye of the strut fail it would have to be loaded in tension. In normal circumstance this shouldn't happen unless due to wind when the canopy is up. Could there be an alignment issue in some installations where the strut on one side reaches the end of its travel before the other. The further movement of the canopy would then load the slightly shorter strut in tension causing the failure.

The repeated failures on particular aircraft would be explained by this cause.
 
Good point about the canopy struts failing only in tension. The canopy is flexible enough so that it is unlikely that one strut could be applying tension to the other strut. The most likely cause of failure is that the pilot lets go of the canopy before it is fully open. The inertia of the moving canopy applies a large tension load on the struts when they become fully extended.
If the hole in the plastic eye has been enlarged by drilling, then it is much weaker and is more vulnerable to tension loads.
 
Update: It has been brought to my attention that the upper rod end has a different thread size than the bottom. I had actually only measured, and tested the bottom end, which is the trouble spot. So, only order 2 of the posted rod ends. If someone gets to it before I do, please measure and post the thread measurement for the upper end, and we will come up with a replacement for it as well. Sorry for the inconvenience......Tom

For those who I missed seeing at Oshkosh, if you are interested in replacing your canopy strut ends, here is the supplier, and procedure that may work for you. Note that you will end up with the larger diameter bushing on both the top, and the bottom of the strut ..............Tom



July, 2015

Canopy Mod: Heavy Duty Lift Strut Eyelets
Parts needed:
2 Heavy Duty Metal Eyelets M6 X 1.0 thread
Source: LiftSupportDepot.com SKU H00005W $1.90 each
1 set Canopy Bushings N/S C-00002 ( these are only necessary if you have and early kit and the old style bushing.
Source: Van’s Aircraft.

Procedure:

1. Drill/ream hole to 3/8” and clean away any burs on the 2 eyelets.

2. Install new rod ends on bottom end of both lift struts, and install per plans page 43-02
Questions or comments to: Tom Odehnal [email protected]
 
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todehnal said:
For those who I missed seeing at Oshkosh, if you are interested in replacing your canopy strut ends, here is the supplier, and procedure that may work for you. Note that you will end up with the larger diameter bushing on both the top, and the bottom of the strut ..............Tom

July, 2015
Canopy Mod: Heavy Duty Lift Strut Eyelets
Parts needed:
4 Heavy Duty Metal Eyelets M6 X 1.0 thread
Source: LiftSupportDepot.com SKU H00005W $1.90 each
1 set Canopy Bushings N/S C-00002
Source: Van?s Aircraft
note: If you have the old style lower bushings, and have not made
the mod, order 2 sets.
Procedure:
1. Drill/ream hole to 3/8? and clean away any burs on all 4 eyelets.
2. Remove stock from the shoulder of 2 of Van?s bushing to match the overall length dimension of the old upper bushings.
3. Install new rod ends on both lift struts, and install per plans page 43-02
Questions or comments to: Tom Odehnal [email protected]
Click to expand...

I'm assuming this would not be acceptable for S-LSA....

Fingers crossed and knocking on wood, no problems with mine so far....

TB
 
Failed Canopy Strut

Hello everyone,

I have an embarrassing story to share and do so with the hope I can save someone from making the same mistake.

It all started with an ignition check that indicated the B-module was offline. My ignition checks were showing too large of an RPM difference on the B module. The problem turned out to be a loose spark plug wire that had been dislodged when I was re-installing the lower cowling. Such a simple fix!

That's the good news.

The bad news is that while testing in 92 degree heat, I had the canopy closed, not latched but propped open for air ventilation. I ran the ignition check and all was good with the world until I turned to head back to the hangar. At that point, the cross wind caught the canopy and blew it open. The lift struts both broke at the end attached to the canopy and the canopy had the momentum needed to tip forward into the prop. This all happened so quickly it would have been impossible to intercede.

I'm in the process to replace/rebuild the canopy. Sensenich repaired the prop and Perry Robertson did a gearbox check for me.

I'm very lucky not to have been struck by any of the flying, very sharp shards! This has been reported to Vans and I was told they are looking into this aspect of the design with no hint of a timeline nor outcome.

Henceforth, I'm always going to have my canopy latched when the motor is running. I'm also thinking of modifications to use so that on very hot days the canopy can rest on the handle/latch but not fly open. The metal rod ends are also of interest to me.

I hope this information is of use and helps others avoid duplicating my mistake.

Slane
RV120043
 
I should have added that wind slammed mine down once with the tow bar lying across the canopy rail. It bent my canopy trim.
 
Slane said:
... propped open for air ventilation ...
Click to expand...

Sorry to hear about your incident Slane but thanks for posting it.

How did you have the canopy propped up? I usually prop mine open by closing the latch with the canopy open then resting the protruding latch on the top of the canopy bow. That doesn't let in a huge amount of air but has been sufficient for me in our Florida heat. Did you have it propped more open than that?

As a separate question, I picked up the habit of propping mine open on the latch like that from other -12 owners I've talked to. I've often wondered about the twisting stress that puts on the canopy. Does anyone have an opinion about that?
 
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tomkk said:
How did you have the canopy propped up? I usually prop mine open by closing the latch with the canopy open then resting the protruding latch on the top of the canopy bow. That doesn't let in a huge amount of air but has been sufficient for me in our Florida heat. Did you have it propped more open than that?

As a separate question, I picked up the habit of propping mine open on the latch like that from other -12 owners I've talked to.
Click to expand...

This is exactly how I had mine propped open. Just about every RV12 pilot I know props their canopy open in this fashion.

Slane
 
I had an interesting moment just yesterday - INSIDE MY GARAGE! I hook the canopy open by a hook around the canopy latch to the garage door opener track. While pushing down on the tail to place a board under the nose wheel (so the tail would not punch a hole in the sheetrock) the hook came unlatched allowing the canopy to bang down on the roll bar. Bent the latch mechanism pretty badly! I was able to straighten it back, no expensive harm done.
It got me to thinking, that the struts SHOULD be the slow motion type that would not permit any of what has been discussed here.
Another point came up in discussions with others, one must NOT tighten the upper end bolt, since that puts a bending motion on the upper eye. The plans are a bit vague, but does allow for that with loose bolts on the upper end.
 
I think any engineer would want both metal rod ends and a through bolt at the top end. The current design is simply going to fail at some point due to the plastic rod ends breaking out at the top end when the canopy is allowed to open without restraint or in a wind/prop blast that is going to happen sometime in the life of the bird. Even with a metal rod end at the top there will someday be a failure of the screw through the carbon fiber on only one side up there. Van's airplanes are such masterly designed airplanes it's hard to understand how the canopy strut design was allowed in the plan.
EBB
 
one must NOT tighten the upper end bolt, since that puts a bending motion on the upper eye
Click to expand...
Doesn't the bolt tighten against bushing C-1204 and not put pressure on the strut eye?
 
Slane said:
This is exactly how I had mine propped open. Just about every RV12 pilot I know props their canopy open in this fashion.

Slane
Click to expand...

Thanks. That leaves such a small gap, I'm flabbergasted the wind was able to get under it enough to flip the canopy open. I'll have to pay more attention when I have it outside with it propped open.
 
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No Joe, that is part of the apparently sloppy way to get the angle to to align with the bottom attachment. I checked the plans this morning. It is my belief that the UPPER end fails because it bends the top eye about 5 degrees every time the canopy is opened if the bolt is tightened, which several builders have told me they did..
Mich48041 said:
Doesn't the bolt tighten against bushing C-1204 and not put pressure on the strut eye?
Click to expand...
 
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