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WurlyBird

Joined: 16 May 2008
Posts: 207
Location: North Pole, Alaska

Posted: Fri Feb 06, 2009 5:58 pm Post subject: Problem with FLUTTER ? ! ? !

So today was my first day of instruction in my KF3 and it was a blast.  The instructor pretty much let me do my thing and talked me threw a couple takeoffs and landings and then we just flew around for a couple hours constantly requesting the controls from the other person.  



So I have a few questions now that I actually have some time in the KF but the biggest one involves what I can only describe as "flutter".  It was our final leg as we flew back to the airport after buzzing my house, cruising at about 75-80 mph when an updraft hit one of the wings and set off a vibration in the wings.  It only lasted a few seconds while I throttled back and slowed down quickly.  There appeared to be a pivot, or node for you engineer types, at each wing support point and one in the center of the cockpit which was evidenced by feeling like I was in a drink shaker.  The wings were not acting in unison and it felt VERY uncomfortable.  I have seen video of gliders doing this at speeds above Vne.  It gave us both a startle and I would like to figure out what possible causes were for this and if it is something I can fix or if it is just somethings that happens.  I seriously doubt this is normal, but who knows maybe it is how to pick out the "New Guy".  



Thanks for the help.

_________________
James
Kitfox 3 / 582 / 70" IVO 2 blade GA
50 hrs on the 582 swapping for HKS 700E and Avid Cowl.

henrysfork1(at)msn.com
Guest

Posted: Fri Feb 06, 2009 6:46 pm Post subject: Problem with FLUTTER ? ! ? !

Sounds similar to flapperon flutter. They installed counter weigts on the flapperons to prevent this. Not sure if the model III was subject to that or not. That is a place to start. Maybe check the slop in the control linkage also. 

  

 Dee Young

 Model II

 N345DY

  

 Do not archive



 	  Quote: 	
		   Subject: Problem with FLUTTER ? ! ? !

 From: james.t.trizzino(at)us.army.mil

 Date: Fri C 6 Feb 2009 17:58:42 -0800

 To: kitfox-list(at)matronics.com

 

 --> Kitfox-List message posted by: "WurlyBird" <james.t.trizzino(at)us.army.mil>

 

 So today was my first day of instruction in my KF3 and it was a blast. The instructor pretty much let me do my thing and talked me threw a couple takeoffs and landings and then we just flew around for a couple hours constantly requesting the controls from the other person. 

 

 So I have a few questions now that I actually have some time in the KF but the biggest one involves what I can only describe as "flutter". It was our final leg as we flew back to the airport after buzzing my house C cruising at about 75-80 mph when an updraft hit one of the wings and set off a vibration in the wings. It only lasted a few seconds while I throttled back and slowed down quickly. There appeared to be a pivot C or node for you engineer types C at each wing support point and one in the center of the cockpit which was evidenced by feeling like I was in a drink shaker. The wings were not acting in unison and it felt VERY uncomfortable. I have seen video of gliders doing this at speeds above Vne. It gave us both a startle and I would like to figure out what possible causes were for this and if it is something I can fix or if it is just somethings that happens. I seriously doubt this is normal C but who knows maybe it is how to pick out the "New Guy". 

 

 Thanks for the help.

 

 --------

 Prospective Kitfox buyer

 Here for information on airframes and engines

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=229000#229000

 

 

 

 

 

 

=====================

 _==========

jdmcbean(at)kitfoxaircraf
Guest

Posted: Sat Feb 07, 2009 9:57 am Post subject: Problem with FLUTTER ? ! ? !

This is a serious issue.. review what Dave said (see below) I would also

check the airspeed indicator for accuracy. 



"The long ailerons can be very susceptible if there is any flexing or slop

in the linkages.  Furthering the issue is the flaperon linkage from the

stick to the aileron. Stiffer is better than loose.

 

Full amplitude of the flutter can be achieved in just a few cycles... a

second.  Stay away from it. Its speed related.  Part of the solution is mass

balancing.  I believe you should have at LEAST one per aileron and the must

be installed. The other is carefully looking at the entire linkage for ANY

slop.

 

Fix this issue.  If it happens again you must slow down right away and land.

Interesting, you will need to slow down to a slower speed than it started to

get it to stop ....

 

Flutter is brutal to hinges, control surfaces, linkages .... ok ok

everything!

 

I had it once briefly and let me tell you I re tightened everything and

STRICKLY adhere to VNE. I have since flown probably 350 plus hours without

another hint of it...

 

Fly Safe, enjoy

 



--

WurlyBird

Joined: 16 May 2008
Posts: 207
Location: North Pole, Alaska

Posted: Sat Feb 07, 2009 2:20 pm Post subject: Re: Problem with FLUTTER ? ! ? !

I am gonna go through all my linkages to make sure everything is nice and snug before I fly again.  I have the flaperon counterweights installed, so at least that has already been done.  Funny you mention the ASI, I was questioning it at times during the flight.  But it seemed to be indicating higher then actual frequently.  I set it up a couple of times for a moderate cruise setting, 5500 to 5800 in level flight with a 582, and slight updrafts would cause airspeed to indicate right at 100 mph.  This seems a bit unlikely.  Also several times on final I would be indicating 70 to 80 and it would feel like the proper approach speed based on stick feel, ground speed, decent, so I would hold 70 to the round out and it would feel pretty natural.  I am definitely still learning the nuances of his little plane.

_________________
James
Kitfox 3 / 582 / 70" IVO 2 blade GA
50 hrs on the 582 swapping for HKS 700E and Avid Cowl.

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Sat Feb 07, 2009 3:27 pm Post subject: Re: Problem with FLUTTER ? ! ? !

Do you have a GPS to check it against?  I found that mine was off about 5 mph (high) from 40-65 then it was dead on up to 110.

_________________
DO NOT ARCHIVE
Leonard Perry aka SNAKE
Soldotna AK
Avid "C" / Mk IV
582 (147 hrs and counting on the rebuild)
IVO IFA
Full Lotus 1450
#1 snake oil salesman since 1-22-2009

I would rather die trying to live, than to live trying not to die....

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat Feb 07, 2009 7:56 pm Post subject: Problem with FLUTTER ? ! ? !

I've never had a flutter on my plane but I expect cutting the power and

possibly loading the flaperons (pulling a bit of flap )  would stop the

flutter close to instantly.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

WurlyBird

Joined: 16 May 2008
Posts: 207
Location: North Pole, Alaska

Posted: Sat Feb 07, 2009 8:18 pm Post subject: Re: Problem with FLUTTER ? ! ? !

Well as quickly as I could react, about a second I think, I reduced the throttle and started a slight climb.  This helped so I closed the throttle more and climbed steeper and it stopped almost instantly.  I was indicating 75 to 80 at the time, it was at about 5800 rpm, straight and level.



I went through all my control linkages and I am very concerned to report that there is a fair amount of play in the system that doesn't appear to be able to be tightened out.  Every single spherical bolt in the system, there is about 16 per side I think, has a noticeable amount of play in it, say.01".  If I hold one flaperon control tube still I can coax about .1" of play out of the other.  Unless the guy who built this plane somehow managed to mangle every single spherical bolt he came into contact with it seems that this is something I may have to live with.  Not the actual flutter but the risk of it.  What is the consensus here?



A. the builder damaged all 30+ spherical bolts it the flaperon mixer/system



B. the system is fine and I just found myself in that 1:1000000 circumstance



C. the ASI is in horrible err and this plane is capable of over 100 mph straight and level with a 582 at cruise settings



D there is a way to tighten these bolts that I am unaware of

_________________
James
Kitfox 3 / 582 / 70" IVO 2 blade GA
50 hrs on the 582 swapping for HKS 700E and Avid Cowl.

darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Sun Feb 08, 2009 9:11 am Post subject: Re: Problem with FLUTTER ? ! ? !

WurlyBird,



My first Kitfox was a model 3 with the 912 UL and there was no way I was getting 100 mph out of it in straight and level flight.  In Fact, my typical cruise at 5000 rpm was 75-80 mph.  When I sold it, the guy who bought it wanted to do a full power run to see what it would do and we saw 94 mph.  I never experienced any flutter and don't remember any slop in any of the systems...but it was built by the former president of Kitfox/Skystar so he knew the airplane inside and out.  Hope you figure it out.

_________________
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah

Tom Jones

Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA

Posted: Sun Feb 08, 2009 12:44 pm Post subject: Re: Problem with FLUTTER ? ! ? !

 	  Quote: 	
		  A. the builder damaged all 30+ spherical bolts it the flaperon mixer/system 



B. the system is fine and I just found myself in that 1:1000000 circumstance 



C. the ASI is in horrible err and this plane is capable of over 100 mph straight and level with a 582 at cruise settings 



D there is a way to tighten these bolts that I am unaware of 	


James, I will offer some ideas to check.



There was an instance early on in kitfox history where a flaperon control rod unscrewed itself during transport on a trailer.  Being that yours just completed a long ride I would check everything with that in mind.  Look for something that might have loosened up during transport.



Check everything between the stick and the flaperon hinge attachments to the wings.



Rod ends should not have slop on their attach bolt.  They should be replaced if they do.



Make sure all check nuts are still tight.



The flaperon control horn tube passes through a nylon bering on the turtle deck.  Is that bering snug around the control horn tube?

_________________
Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA

WurlyBird

Joined: 16 May 2008
Posts: 207
Location: North Pole, Alaska

Posted: Sun Feb 08, 2009 9:03 pm Post subject: Re: Problem with FLUTTER ? ! ? !

UPDATE:

   well I went through the system some today and was able to remove some of the play.  it seems the guy who built this plane reamed every single hole over size.  In addition there are spherical bolts that are not snug in their fittings so I need to order a bunch of washers to tighten everything up.  Can anyone go check and tell me how much they can wiggle one flaperon control tube when the other one is held in place?  I have it down to less then 1/16" and looking at the system I just don't believe it can get much better then that.

_________________
James
Kitfox 3 / 582 / 70" IVO 2 blade GA
50 hrs on the 582 swapping for HKS 700E and Avid Cowl.

jcorner(at)shaw.ca
Guest

Posted: Sun Feb 08, 2009 9:29 pm Post subject: Problem with FLUTTER ? ! ? !

I think you are probably of with a maximum of 1/16 when holding one ailreron.   I think you also need to hold the stick solid and expect the same or less wiggle.

What model of Kitfox are we talking about.  I have 1100 hrs on my Model 2 and would estimate thats about the wiggle I have. 

Jim Corner

Model 2, 582,. Ivo med !FA, 1100 hrs

Model 5, 0-235 40Hrs 

Calgary, AB





On 8-Feb-09, at 10:03 PM, WurlyBird wrote:

 [quote][b]

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Mon Feb 09, 2009 3:53 am Post subject: Problem with FLUTTER ? ! ? !

What the hell is a spherical bolt?



Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200, #2062, 605 hrs

Sensenich 62x46

Electroair direct-fire ignition system

New skis done and flying

do not archive



On Feb 9, 2009, at 12:03 AM, WurlyBird wrote:



 	  Quote: 	
		   

 <james.t.trizzino(at)us.army.mil>



 UPDATE:

    well I went through the system some today and was able to remove  

 some of the play.  it seems the guy who built this plane reamed  

 every single hole over size.  In addition there are spherical bolts  

 that are not snug in their fittings so I need to order a bunch of  

 washers to tighten everything up.  Can anyone go check and tell me  

 how much they can wiggle one flaperon control tube when the other  

 one is held in place?  I have it down to less then 1/16" and  

 looking at the system I just don't believe it can get much better  

 then that.



 --------

 Prospective Kitfox buyer

 Here for information on airframes and engines





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 29299#229299

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Tom Jones

Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA

Posted: Mon Feb 09, 2009 7:42 am Post subject: Re: Problem with FLUTTER ? ! ? !

 	  Quote: 	
		  UPDATE: 

well I went through the system some today and was able to remove some of the play. it seems the guy who built this plane reamed every single hole over size. In addition there are spherical bolts that are not snug in their fittings so I need to order a bunch of washers to tighten everything up. Can anyone go check and tell me how much they can wiggle one flaperon control tube when the other one is held in place? I have it down to less then 1/16" and looking at the system I just don't believe it can get much better then that. 	




james, My kitfox has the the wings folded so the flaperons are disconnected right now.  Pulling up and down on both flaperon control tubes I can feel a slight amount of slop but it is not enough to measure.  I actually can't see the movement just feet it slightly.  Now this is a Classic 4 so the comparison may be apples to oranges.



You mention spherical bolts.  Is that another name for rod ends?  If so, I don't exactly follow how a sloppy one could be tightened up by adding washers.  The control rods do need to rotate back and forth slightly in the attachments.



Don't try to use washers to stop the rotation of the double rod end attachment between the stick and the aileron bell crank.  It needs to rotate quite a bit as the stick moves fore and aft.  A fellow rebuilt a kitfox a while back and that attachment broke during a test flight.  I suspect that connection was installed with too much limit in the rotation.  He landed safely by the way, using rudder to turn.

_________________
Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA

Fox5flyer
Guest

Posted: Mon Feb 09, 2009 8:34 am Post subject: Problem with FLUTTER ? ! ? !

occom

Joined: 26 Aug 2006
Posts: 404

Posted: Mon Feb 09, 2009 12:04 pm Post subject: Problem with FLUTTER ? ! ? !

I figured they were referring to heim joints.

---

matronics(at)bob.brennan.
Guest

Posted: Mon Feb 09, 2009 12:45 pm Post subject: Problem with FLUTTER ? ! ? !

What the hell are heim joints??



Bob Brennan - N717GB

ELSA Repairman, inspection rated

1991 UK Model 2 ELSA Kitfox

Rotax 582 with 3 blade prop

Wrightsville Pa   



--

mscotter

Joined: 15 Jan 2006
Posts: 49
Location: Winston-Salem, NC

Posted: Mon Feb 09, 2009 1:19 pm Post subject: Problem with FLUTTER ? ! ? !

Think rod ends, ball and socket joint, etc. 

Sent via BlackBerry by AT&T



--

_________________
Mark Scott
Winston-Salem, NC

Paul A. Franz, P.E.

Joined: 02 Dec 2008
Posts: 280
Location: Bellevue WA

Posted: Mon Feb 09, 2009 1:27 pm Post subject: Problem with FLUTTER ? ! ? !

On Mon, February 9, 2009 12:44 pm, Bob Brennan wrote:

 	  Quote: 	
		   



 What the hell are heim joints??


	


Threaded rod ends with a greasable or or permanently lubricated ball joint.



Here's a drawing;



<http://www.igus.com/igubal/sizepresent.asp?p=KBRI>



Here's a bunch of typical ones;



<http://www1.mscdirect.com/CGI/N2DRVSH?PACACHE=000000084184825>



The Heim name is most familiar among hot rodders and race car enthusiasts.



<http://autorepair.about.com/library/glossary/bldef-187.htm>



-- 

Paul A. Franz

Registration/Aircraft - N14UW/Merlin GT

Engine/Prop - Rotax 914/NSI CAP

Bellevue WA

425.241.1618 Cell

_________________
Paul A. Franz, P.E.
Registration/Aircraft - N14UW/Merlin GT
Engine/Prop - Rotax 914/NSI CAP
Bellevue WA
425.241.1618 Cell
425.440.9505 Office

815TL

Joined: 10 Oct 2008
Posts: 62

Posted: Mon Feb 09, 2009 2:43 pm Post subject: Re: Problem with FLUTTER ? ! ? !

I had to replace 3-4 rod end links on mine as well.  There was quite a bit of slack in the controls.  It fixed it right up and now it is nice and tight.



Andrew

815TL, Kitfox II, Rotax 582-C.

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Mon Feb 09, 2009 4:41 pm Post subject: Problem with FLUTTER ? ! ? !

Heim was probably the original, or at least one of the first (and  

best) of the "spherical rod end bearing" manufacturers. I just never  

heard of this device called a spherical "bolt"...which, of course, it  

is not...a "bolt" that is.

Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200, #2062, 605 hrs

Sensenich 62x46

Electroair direct-fire ignition system

New skis done and flying

do not archive



On Feb 9, 2009, at 3:44 PM, Bob Brennan wrote:



 	  Quote: 	
		   

 <matronics(at)bob.brennan.name>



 What the hell are heim joints??



 Bob Brennan - N717GB

.

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

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