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Y/A F-22 Rudder Flutter - 7/25/2012 5:06 PM   
YellowAircraft



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Status: offline 		Hi,

I was contacted by a customer regarding the crash of his Y/A Raptor. From the pictures, we are not able to know for sure what let go first, but he reports that the fin departed at moderate speed in level flight. In the photos, you can see that the rudder horn is broken clean. IMO, the rudder horn was the failure point, and rudder flutter ensued causing the fin to depart.

The customer wants owners and builders of this airplane to be aware of his misfortune in case there's a future crash that can be prevented. So do I. Personally, I've used those stock horns on many F-15's without issue, but that doesn't mean that it was not (or could not be in the future) the failure point. I've forwarded his email on to Charles, and I recommend that current owners inspect their rudders, fins and rudder horns to make sure there's no crack or weak-spot. On the next one I build, I intend to upgrade to a heavier-duty, carbon-reinforced horn.

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RE: Y/A F-22 Rudder Flutter - 7/25/2012 5:34 PM   
gunradd



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Status: offline 		I am cutting mine out today. I orderd some carbon BVM horns to replace them. I didnt like the stock ones from the start and used carbon ones on the flaps but used stock ones on the rudder.

Very glad we are told about the problem so it can be corrected.

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RE: Y/A F-22 Rudder Flutter - 7/25/2012 5:43 PM   
dubd



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Status: offline 		Sorry for your customer's misfortune, but I applaud you for being proactive.

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RE: Y/A F-22 Rudder Flutter - 7/25/2012 5:57 PM   
FenderBean



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Status: offline 		hey yellow, call crazy but that last picture looks like it has been glued and broke at the point of being glued. It looks yellowish and you can see were the glue had pushed out when the two parts were put together. You can even see the glue in the grain area of the hinge?
Is this what you guys can see as well?


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RE: Y/A F-22 Rudder Flutter - 7/25/2012 6:11 PM   
YellowAircraft



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Status: offline 		Hi,

I can see how you'd get that impression looking at the pic. Knowing the customer, though, I can't imagine him doing that in ten million years.

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RE: Y/A F-22 Rudder Flutter - 7/25/2012 6:14 PM   
FenderBean



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Status: offline 		Cool deal just looks like that from the picture, sorry a nice jet like the YA F-22 crashed, was it a totally destroyed?

quote:

ORIGINAL: YellowAircraft

Hi,

I can see how you'd get that impression looking at the pic. Knowing the customer, though, I can't imagine him doing that in ten million years.




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RE: Y/A F-22 Rudder Flutter - 7/25/2012 6:24 PM   
tp777fo



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Status: offline 		I had flutter on mine early on. The cause was poor setup of epoxy that held the horn. The horn pulled out and the rudder came off. Luckily I didnt lose jet. I replaced both horns with cf horns. Added bigger hinges and used ply to beef up the rudder hinge posts. No further problems and it still flies well. If I do anotber I will use cf horns on entire jet. Good job Shaun on letting all know of a potential problem!


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RE: Y/A F-22 Rudder Flutter - 7/25/2012 7:18 PM   
Ian R


 

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Status: offline 		 Hi all

It was my model

I want to disagree with you Shaun, I would not glue like that in 50 million years not the 10 mil you quoted    !

the horns are standard, never broken and well fitted in the rudder. The point of the picture was to show the failure comes from the material, no crack or damage propagation. IMO in hindsight the horns are nicely shaped but too thinned for the material they are made from. Easy to be smart after the event. The hinges are intact and secure, the wood post failed at the rear of the fin. servo and linkage all intact.

The model was totalled but I was flying in the safe area of our airfield and the model impacted the ground well away from anything or property, I just wanted, through Shaun, to advise Yellow Aircraft and other F22 users. Yes the model was totalled but I  am thankful no one was hurt and other than a 20 sq ft of burnt ground no damage to property.

to be clear it was a great model, one of the best I have owned

Ian

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RE: Y/A F-22 Rudder Flutter - 7/25/2012 8:20 PM   
tp777fo



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Status: offline 		Sorry Ian...get another and get building!

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RE: Y/A F-22 Rudder Flutter - 7/25/2012 11:36 PM   
ddlstang


 

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Status: offline 		I assume the ball link is what was supplied. I know on some materials of horns made that you should use a clevis instead of a ball link to prevent twisting.

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RE: Y/A F-22 Rudder Flutter - 7/25/2012 11:51 PM   
ianober



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Status: offline 		I wouldn't be warning just F-22 owners but all Yellow owners. Those horns are also used in their F-15 kit and ARF. So this should be for all models, not just one.

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 12:06 AM   
gunradd



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quote:

ORIGINAL: ianober

I wouldn't be warning just F-22 owners but all Yellow owners. Those horns are also used in their F-15 kit and ARF. So this should be for all models, not just one.


Well I think the big issue is the F22 has a lot of stress on the rudders in flight. Every manufacture has had rudder problems with the F22s. Jetlegend even made them smaller on thier model.

I thought I lost my rudder at kentucky jets while doing a knife edge pass the plane went into a hard snap roll with no aileron inputs at all. It turns out that when you pull to much rudder with the F22 that it snaps. My friend did it also with his skymaster F22.

I will stress test mine when I get them off the rudder and see the breaking point and if it looks like Ians.

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 2:29 AM   
gunradd



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Status: offline 		Well I had a brand new one in my box since I didnt like it from day one and used BVM carbon ones on the flaps during the build. So here are the pics. It did not take much to snap it. Its pretty strong for and aft but is pretty flimsy if bending up or down. It did not take much effort to snap it. It looks just like Ians when it breaks. They are complete crap.

I have built many yellow kits and love them. But these horns suck! I am pretty sure everyone would be fine paying $10.00 more for an aircraft kit and get quality carbon horns.

Ian I think having the ball link made the problem worse in your case because it put a twisting motion on the horn. Really sucks to loose such a great fling plane Ian. Sorry for the loss man but thanks for the warning.

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 6:51 AM   
loucel-RCU



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Status: offline 		sorry about your loss Ian,

I thought , a clevis such as Dubros or similar is intended to be used with this type of horn,
the pictures show how the ball link set-up can load one side of the horn....

my two cents

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 8:42 AM   
Ian R


 

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I agree in hindsight the ball link might be a contributor in particular after Kris's test.

My logic was to reduce play in the linkage after others lost their rudders, quick links in fibre material create play after a period of operation in my view, ball links reduce this. I have not  been knife edging the aircraft, only using rudders in cross winds and the occasional slow roll .

I do support the odd aerodynamics on the 22 from the fin angles, the side load from the ball link and  the control horn is thin for that material all contributed to the failure.

I think the loads are different on the F15 but I will be changing mine, yes I have yellow F15 which is another great flyer but not as good as the 22

Ian

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 11:15 AM   
smchale



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Status: offline 		Ian, sorry for your loss. Thanks for sharing the warning, that's first class of you.
If you have enough meat in the surface perhaps a pair of these on each side of a ball link would give you the rigidity that you're looking for without the risk of twisting. I know hindsight is 20-20, but worth considering when you build another.

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 12:14 PM   
BaldEagel



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Status: offline 		Sorry for the loss of your F-22 its a bummer when that happens.

Not trying to be a smart a**e, but some time ago I thought that the so called Phenolic horns being supplied by most manufactures where of a very low standard and not strong enough torsionally, this I proved to myself by twisting some of the C-ARF and Extreme Flight horns, so my solution was: http://www.rcuniverse.com/forum/m_7203928/tm.htm been using them every since, now days you can buy carbon horns off the shelf, so no need to make them.

Mike

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 1:54 PM   
warbird_1



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quote:

ORIGINAL: YellowAircraft

Hi,

I was contacted by a customer regarding the crash of his Y/A Raptor. From the pictures, we are not able to know for sure what let go first, but he reports that the fin departed at moderate speed in level flight. In the photos, you can see that the rudder horn is broken clean. IMO, the rudder horn was the failure point, and rudder flutter ensued causing the fin to depart.

The customer wants owners and builders of this airplane to be aware of his misfortune in case there's a future crash that can be prevented. So do I. Personally, I've used those stock horns on many F-15's without issue, but that doesn't mean that it was not (or could not be in the future) the failure point. I've forwarded his email on to Charles, and I recommend that current owners inspect their rudders, fins and rudder horns to make sure there's no crack or weak-spot. On the next one I build, I intend to upgrade to a heavier-duty, carbon-reinforced horn.

i have seen that material deteriorate from sunlight before. case in point... i bought a set of robart point hinges that was inside a sun faded package . when i removed them they literally crumbed in my hand ... literally ! i'm not sure what material that is ,but is does look similar. My guess is the arm ,being weak, got overloaded and snapped causing the flutter. I'm all for CF horns .

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 2:18 PM   
YellowAircraft



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quote:

ORIGINAL: ianober

I wouldn't be warning just F-22 owners but all Yellow owners. Those horns are also used in their F-15 kit and ARF. So this should be for all models, not just one.


Ian,

I thought I'd throw a couple facts in here. "All models" includes the F-22 and F-15 ARF's. It's more like 'both' models that are factory-supplied with those horns. I haven't experienced a failure on any of them, with hundreds of flights on half a dozen F-15 ARF's. My current F-15 is powered by a K-170 and flies hard and fast. None of mine are set up with balls or anything on the horn itself but, rather, clevises at the horn and balls at the metal servo arm.

I think the observation about the relative size of the flying surface to the size/material of the horn is important. After I saw Ian's pics, I went downstairs and did a test-to-destruction on some of those horns I have sitting in a box. I broke them with my hands, although the amount of force it took left me feeling ok about them being on my F-15 (in case the hundreds of flights didn't). In the case of the rudder on the F-22, I don't think I would feel so confident, so I'm definitely advising owners to replace those on existing models and to use a heavier-duty horn on kit-built models.

Again, thanks Ian R., for bringing this to my attention and let me know if there's any way I can help.

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 2:38 PM   
ddennison


 

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Status: offline 		Great information, thank you all for sharing.

My Raptor is setup with clevis at the rudder and ball at the servo arm. I did not like the horns either but I have them in the plane since 2008.
I also had built the plane with extra and larger rudde hinges over previous concern of flutter etc.

When I looked at the rudder action I found that the clevis had to rotate a small amount while translating since the pushrod is not square to the hinge line, and so the clevis allowed that slight motion without binding. I was more worried about the hole failing. Has not yet...

Certinly CF would be better, no argument, I will have to decide about changing mine out but I do wonder if anyone who has been using a clevis on the horn has had a failure on the rudder?

I also looked at several CF horns when I built mine but would love to know if anyone finds one that has closest geometry to the existing setup!


Thanks
Dave

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 2:44 PM   
BaldEagel



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Status: offline 		You may find something here: http://mt.engel-modell.de/index.php/katalog/showarticles/563500-1-control_horn.html

Mike

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 2:55 PM   
cycross



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Status: offline 		Being an owner of a Y/A F-22 kit, thanks Ian to share this critical information and sorry to hear about your loss as a consequence. I definitely be changing out my control horns during my build.

Thanks too to Shaun for the courage and integrity as a dealer to declare the potential weakness openly.



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RE: Y/A F-22 Rudder Flutter - 7/26/2012 5:50 PM   
gunradd



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Status: offline 		Got the new carbon fibre horn in today from BVM. Should work great. Wont have to worry about this breaking now. Only $3.00 a peice.

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 6:07 PM   
YellowAircraft



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Status: offline 		Hi,

What's that part number?

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RE: Y/A F-22 Rudder Flutter - 7/26/2012 6:13 PM   
gunradd



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quote:

ORIGINAL: YellowAircraft

Hi,

What's that part number?



Hey Shaun
BVM part# K5300M-RC021


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