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Stabalator Flutter

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Alan Carter

Joined: 02 Jul 2012
Posts: 378
Location: Kent, England.

Posted: Mon Oct 15, 2012 12:21 pm Post subject: Stabalator Flutter

Hello ALL.

This question is nothing to do with how to fix the Toque Tube and stop flutter.

Ok i know stabalators are more efficient than the elevator, and they can,t Rime ice up like an elevator and i have flow many aircraft with stabalators

and i don,t like them.

Question is what is Flutter only??

I keep hearing the word  Stabalator Flutter, I have the obvious idea as to what happens but would like to know more, maybe someone has experienced it.

Do the Stabalators flutter independently, or both up and down together,

How fast is this fluttering, How is the on-set noticed in the cockpit, Can you feel it through the joy stick,( of course you can, but a tell tell indication maybe in some flight attitude or configuration well before an event). Is it controllable, What would be the position held by the stabalators if you had no control.  ete,ete,ete, agian not a test just something we can all chew over.



If anyone has experienced flutter please tell us,



Alan     



 [/u]

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Alan Carter

Joined: 02 Jul 2012
Posts: 378
Location: Kent, England.

Posted: Wed Oct 17, 2012 12:37 pm Post subject: Re: Stabalator Flutter

Hi All.

This link posted by Nigel shows just what forces are at play, he had no chance, But a Europa is not as fast and maybe you could do some thing if you had the time,



http://www.ntsb.gov/doclib/reports/2012/AAB1201.pdf



 You probably would feel a juddering on the stick and maybe a hammering from the tail, I have noise cancelling headsets, this is one good reason for not having one,but they are really good so i will keep using mine, 

However if i felt a fore and aft control shudder, i would close the throttle, hit the full fine on the prop and ease a little up to slow down as quick as possible, if possible a Mayday and get rid of the noise cancelling so i can hear the aircraft,

At this point i would decide , go for the closes runway or straight ahead down, but i think i would keep it slow and flap-less all the way down and hope.

Any Comments

Alan

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budyerly(at)msn.com
Guest

Posted: Sun Oct 21, 2012 6:08 am Post subject: Stabalator Flutter

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Alan,

 I noted no answer to your question on what is flutter.

 Attached are some video sites for you to look at.  In engineering,  vibration and aeroelastic concerns on fatique and flutter are very serious  studies.

 Please review:  

http://www.aircraftdesigns.com/aircraft-flutter-analysis.html 

http://www.youtube.com/watch?v=YIHam_isyI8&feature=related 

I became interested in the  subject when government cuts forced us to go to a cheaper hydraulic line in the  F4.  We were seeing numerous problems with hydraulic failures using the  aluminum lines attached.  Without hydraulic pressure, the flight controls  did not lock in position in certain failures (breaking of the control  pack) and controls would begin to buzz at high speed.  Luckily the  aircraft wing was brutally strong, we had redundant hydraulic controls and  with only one hydraulic failure we pilots normally slowed down, declared an  emergency and returned to base without incident.  One crew lost  all hydraulic control on one wing and the back seater could see the aileron  flopping about.  They slowed to 240 knots and the flutter stopped but hinge  and trailing edge damage was evident in only a few seconds of  flutter. 

  

 Later I was involved in a local Twin Commanche incident where rivets were  popped all over the stab and I was asked to look at it.  See the video  below.  The type of flutter is evident on stabilators as well as  conventional horizontal control surfaces which are not balanced.

  

  http://www.youtube.com/watch?v=iTFZNrTYp3k

 [quote]   ---

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Alan Carter

Joined: 02 Jul 2012
Posts: 378
Location: Kent, England.

Posted: Sun Oct 21, 2012 7:35 am Post subject: Re: Stabalator Flutter

Wow Bud, that,s pretty scary stuff, have a lot of hours on Twin Coms. glad i knew nothing about flutter then, what happened to it in the video.

Well i got the first bit right, slow down, but have not that brutal tail-plane you mention, only have a foam one!, and yes i do have a hang up on tail planes maybe its because i can,t see it.

There have been some excellent ideas posted on MOD 73 . how to elimination play and wear in the Toque tube, and this question is just an extension of that topic, so hoping for some airman-ship replies also.

Regards 

Alan

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budyerly(at)msn.com
Guest

Posted: Mon Oct 29, 2012 10:36 am Post subject: Stabalator Flutter

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  On Flutter,

 We dumb engineers really enjoy collecting testing video.

 The Comanche video and others were setups to determine failure modes.   For instance, if you forget to hook up the trim tab or you have forgotten to  check that the bushes are installed in the stab or trim rod, or the bearing in  your Comanche has failed and you didn't note it on the trim tab preflight that  it had 1/4 inch of play.

  

 We just had a twin Cessna (conventional stabilizer and elevator) here in  Plant City that has severe cracking in its trim tab due to poor  maintenance.  The owner and inspector did not notice or think it a problem  that the trim tab had play in it and upon investigation, the bearing in the trim  rod had disengaged from the socket and the trim tab moved 1/4 inch on its  own...  

  

 Any control surface can flutter so it is best to note how much play is in  the bearings, hinges, quick disconnects etc. in any aircraft that flies above  120 KIAS.

 Pay particular attention to those controls which are not balanced on a  wing, or tail (Rudders are normally not balanced if near vertical in non  aerobatic aircraft.

  

 Regards,

 Bud

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