Lazair ruddervaders

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Postby whiskey whiskey » Thu Oct 15, 2009 12:04 am

Any of you Lazair guys had or heard about an in-flight failure of a ruddervader? I am wondering if the Lazair is controlable if one of the pushrods or controlhorns fails.

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Postby Shannon » Thu Oct 15, 2009 1:36 pm

Hi Whiskey Whiskey. Do you have a name, location, and a Lazair ?

The short answer to your question is NOPE not in the 29 years I've been around Lazairs.

Would the plane still be controllable ? Don't know but I'd guess yes ?

Take a look at this picture. Even with major impact damage and the right side of the tail completely torn away from the attachment points the RUDDERVATOR is still in place.
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Postby ozzie » Thu Oct 15, 2009 3:56 pm

there was a mention in an early lazair update from the factory about a series one rudder becomming dislodged at the lower attach point after hitting some rocks during the takeoff. assume the T/O was aborted.
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Postby whiskey whiskey » Sat Oct 17, 2009 12:00 pm

Hi Shannon,

Yes I have a flying Lazair III. I also have a Lazair I and another Lazair III, both of which are in varying stages of disrepair. I fly out of Highland IL.

My partner, 89Charlie, regularly particiates in this forum.

The reason I sent out this question is that the control horns on the Lazair ruddervaders look a bit delicate. I have seen where other Lazair owners have modified the horns to work like a clevis. I am thinking of making this alteration.

Just wondered if anyone has actually seen a failure of the horns and/or pushrods. If so, would the Lazair be flyable with only 1 ruddervader working. I think it would.....but I am not interested in trying it.

Thanks

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Postby JPXman » Mon Oct 19, 2009 4:07 am

i made my own clevis style horns after I inspected the originals before my rebuild. there were cracks in both of them at the inner radius of the horn. way back then my friend did an FEA of the horn and the single horn had quite a stress concentration there. the clevis eliminated it. they're easy to make and incorporate, as you can stack them on the same ruddervator plug if you make new ones out of material just over half as thick as the original. I think I actually had enough play in mine to use another horn of the same thickness

To make them, simply trace a horn onto a piece of aluminum, and make the horn part an extra 2" long. Then, after bending the second piece in a vice to make the gap for the rod end, you can cleco the two horns together and drill through the original horn-hole into the new one to get a nicely aligned set of holes for the rod end. Then grind off the excess and you're done! The tricky part is finding the right angle to bend the piece to, but i have pictures posted somewhere on here for what mine looks like.
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Postby peter » Mon Oct 19, 2009 10:09 am

Hi guys......Here's an interesting thing....I've snapped both the rod ends on the ruddervator horns on my ser. 3.....the first time I broke one, I was pulling the plane back into my tie downs, and the left ruddervator caught a little rise in ground,dug in and snap.....couldn't believe it would break so easy.....I thought it must have been ready to break and was glad it didn't happen in the air....anyway I inspected the whole control system right back to the rudder pedals, and couldn't find any other damage....I thought it for sure must have done damage to the control horn, but no sign of bending or cracking or anything wrong.....well, I replaced the rod end and a few weeks later I forgot to tie the stick back again, and did the same thing to the other side......and again no damage that I could find.......Needles to say, I'm now a little gunshy about backing the plane up.
The point is the rod ends appear to be the weak link in the ruddervator system, mine both broke at the outside of the jam nut without any other apparent damage......This really surprised me because the single control horn certainly looks to be the weak spot in the system.
I certainly think the doubled up control horns is a good mod , and relativley easy to do if for no other reason than piece of mind and good looks.
I'd hate to have a ruddervator fail in flight but my plane flys almost hands off and I feel I would have sufficient elevator remaining to keep control and to land ok.
Just my experience and thoughts...........Peter
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Postby Shannon » Mon Oct 19, 2009 11:15 am

Pete I'd replace all the original Rod ends if that's what you still have. Years back I found some replacement high misaligment Rod ends that are very similiar to OEM. I use now use them exclusively as well as George and Tyler I believe. There's a link to them somewhere here or on Tylers parts list.

I've never seen a broke ruddervator horn but I did find a cracked aileron horn. Because of the way it cracked (over the aileron tube attachment plug) two rivets still had the horn held in place. Surprising that I could not make the remaining portion break off by hand (simulating pushrod push/pull force) even with only 2-3 rivets holding it. Had I not been recovering that aileron I'd probably have never noticed the hairline crack until a total failure occured. I suspect the cracked horn was caused by the previous owner putting the wing down on the ground with the aileron in the neutral position.
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Postby Shannon » Mon Oct 19, 2009 12:39 pm

This broken horn came from a wind storm damaged plane. The complete break you see on this horn is approximately in the same location and direction as the crack I found on the horn on my plane. I'd say it's a good idea to check this area on the aileron horns very closely for hairline cracks.
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Postby lazairiii » Mon Oct 19, 2009 1:19 pm

Good advice by Shannon here folks. Simply add this to your walk around pre-flight inspection since you should have your hands on the pushrod to inspect the bolts and bearings anyway.
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Postby peter » Mon Oct 19, 2009 11:58 pm

Thanks Shannon, and point well taken.....Pete
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