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New Firestar II owner - question about elevator oscillations

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EricS

Joined: 11 Jul 2012
Posts: 7

Posted: Wed Jul 25, 2012 11:00 am Post subject: New Firestar II owner - question about elevator oscillations

Hello fellow Kolbers,



First let me say thanks to all for the helpful info. found here on a variety of subjects.  I have around 30 hrs. in my new (used) Firestar II/503 and I spent many hours before and after I started flying it perusing the archives. 



According to what I can find in the archives, I seem to have an unusual problem.  The issue I'm having is elevator oscillations.  It's not elevator flutter.  Once while flying with my Dad in his Kitfox we experienced sudden and violent aileron flutter, so I know what flutter feels like and this is different.



I dialed her in with rudder and aileron trim tabs and she'll fly straight as an arrow, hands off, in calm conditions.  But when she gets bounced around in light turbulence, the elevator will occasionally begin to oscillate if I don't keep a firm grip on the stick.  It starts slowly and will increase gradually, but I can easily stop it by changing airspeed or pitch.  I had a former Firestar pilot and multiple airplane builder fly with me in his Rans to watch and he said the boom tube began flexing - that's not good.  The immediate solution has been to never let go of the stick.



I'll call Kolb about it, but I thought I would check here first to see if others have experience with this and if there is a known solution.  I have balance rods on my ailerons.  It sounds like I need them for my elevator too.



Thanks,

Eric

-Currently flying in New Mexico, just S. of Albuquerque

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Wed Jul 25, 2012 1:22 pm Post subject: New Firestar II owner - question about elevator oscillations

Eric, Flutter is an a self excited oscillation that increases in amplitude. It can be of low, medium or high frequency. Try putting on stronger trim springs on the elevator circuits or add counter balances to stop it, but this is flutter and you need to get it stopped before it gets out of hand. Has your aircraft ever been repainted? 



Rick Girard

Do not archive



On Wed, Jul 25, 2012 at 2:00 PM, EricS <eric_savener(at)yahoo.com (eric_savener(at)yahoo.com)> wrote:

  	  Quote: 	
		  --> Kolb-List message posted by: "EricS" <eric_savener(at)yahoo.com (eric_savener(at)yahoo.com)>

  

 Hello fellow Kolbers,

 

 First let me say thanks to all for the helpful info. found here on a variety of subjects.  I have around 30 hrs. in my new (used) Firestar II/503 and I spent many hours before and after I started flying it perusing the archives.

  

 According to what I can find in the archives, I seem to have an unusual problem.  The issue I'm having is elevator oscillations.  It's not elevator flutter.  Once while flying with my Dad in his Kitfox we experienced sudden and violent aileron flutter, so I know what flutter feels like and this is different.

  

 I dialed her in with rudder and aileron trim tabs and she'll fly straight as an arrow, hands off, in calm conditions.  But when she gets bounced around in light turbulence, the elevator will occasionally begin to oscillate if I don't keep a firm grip on the stick.  It starts slowly and will increase gradually, but I can easily stop it by changing airspeed or pitch.  I had a former Firestar pilot and multiple airplane builder fly with me in his Rans to watch and he said the boom tube began flexing - that's not good.  The immediate solution has been to never let go of the stick.

  

 I'll call Kolb about it, but I thought I would check here first to see if others have experience with this and if there is a known solution.  I have balance rods on my ailerons.  It sounds like I need them for my elevator too.

  

 Thanks,

 Eric

 -Currently flying in New Mexico, just S. of Albuquerque

 

 

 

 

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 http://forums.matronics.com/viewtopic.php?p=379170#379170

 

 

 

 

 

 

 

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-- 

Zulu Delta

Mk IIIC

Thanks, Homer GBYM

It isn't necessary to have relatives in Kansas City in order to be unhappy.

   - Groucho Marx



 

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_________________
The smallest miracle right in front of you is enough to make you happy....

EricS

Joined: 11 Jul 2012
Posts: 7

Posted: Thu Jul 26, 2012 11:27 am Post subject: Re: New Firestar II owner - question about elevator oscillat

Thanks for your reply, Rick.



I don't have any trim controls on my Firestar, though I have considered installing a "ground adjustable" trim tab on the elevator as I have for the rudder and ailerons, or a simple bungie trim system.  The elevator control cables have no play in them and all bolts are tight on the tail feathers.  One suggestion was to tighten the elevator cable turnbuckle by 1/2 to 1 full turn.  I have not tried this yet.



There are 3 bolt holes to choose from at the front of the elevator to adjust the angle of incidence and both sides are currently attached in the middle.



One of the lower elevator support cables (the cables that can be disconnected to fold up the tail) on the left side was not as tight as the opposite side, so I moved the connection to a different hole.  They are now both nearly as tight as a guitar string, but it made no difference.



The paint appears to be the original.



I will be happy to install counter balance rods on the elevator if necessary.  My thought was that maybe something simple in the set-up of my Firestar was off since nobody else has had a problem with elevator flutter.



I will take a few pics of the tail when I go to the hangar this afternoon and maybe someone with more Kolb experience will see something obvious that I'm missing.



Thanks,

Eric

EricS

Joined: 11 Jul 2012
Posts: 7

Posted: Thu Jul 26, 2012 1:08 pm Post subject: Re: New Firestar II owner - question about elevator oscillat

Correction: I checked my notes and the suggestion to increase the elevator control cable tension is only 1/4 to 1/2 turn of the turnbuckle.

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jul 26, 2012 1:21 pm Post subject: New Firestar II owner - question about elevator oscillations

Correction: I checked my notes and the suggestion to increase the elevator

control cable tension is only 1/4 to 1/2 turn of the turnbuckle.

 

Eric S/Kolbers:



You have a unique situation.  First time I have heard of elevator flutter

with any Kolb aircraft, except a fatal accident many years ago that involved

a Twinstar with adjustable elevator trim tab that was a stock item on

Twinstars.



Why they all don't flutter, I do not know.  They are all very much

unbalanced, hanging from the leading edge, as does the rudder and ailerons.



I like my tail brace wires tight, as in fiddle string tight, no slack.



Elevator cables I also like tight.  When the elevators locked (have someone

hold them snug), there should be no play in the control stick, fore and aft.



We were just talking about rudder flutter.  One way to eliminate rudder

flutter is to keep your feet firmly planted on the rudder pedals.  Another

way is to double up on the rudder springs.  Both ways keep the rudder cables

tight.



I'm guessing tight elevator cables would eliminate elevator flutter.  If

not, tight elevator cables will certainly give the Kolb a much better

control feel in pitch.



john h

mkIII

Titus, Alabama

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Thu Jul 26, 2012 7:37 pm Post subject: Re: New Firestar II owner - question about elevator oscillat

This is a new one, and it sounds like you already have the bases covered. Something that you might try is to put a trim tab on the elevator to get it out of dead center, because being entirely in trail can get it hunting to try and find the place where it wants to live. Use the trim tab to load it postitively in one direction, and then - if necessary - put a spring loaded in flight adjustable trim to restrain it in the opposite direction so that you can live with it. Then go test fly very cautiously and see what happens.



You do know that any time flutter occurs, the quickest way to stop it is to kill the airspeed by chopping the throttle and easing back on the stick?



Regardless, you need to fix it. Keep us posted.

_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.

EricS

Joined: 11 Jul 2012
Posts: 7

Posted: Fri Jul 27, 2012 2:47 pm Post subject: Re: New Firestar II owner - question about elevator oscillat

John & Richard, thanks the additional advice on what to try next.



I checked my tail brace cables this morning and they were definitely not "fiddle string" tight, but they are now.   It does not appear they were ever adjusted since there was paint covering the bolts/nuts.



I'll fly it to see if it's fixed before making another change.  One adjustment at a time so I know what to watch for in the future and I can report back to this List.  I may need to fly it several times since the flutter doesn't occur often.



I braced the elevator and there is no play in my elevator control cables, but they are not what I would call tight.  I think I'll try adding an elevator trim tab next if tightening the tail wires doesn't solve the problem.  If that doesn't help either, then I will add some tension to the elevator cables.



Eric

Dennis Thate

Joined: 18 Nov 2010
Posts: 362

Posted: Sat Jul 28, 2012 4:57 am Post subject: Re: New Firestar II owner - question about elevator oscillat

Eric,



   Hope this helps, as a starting point. This seems to work well for pilots 180 to 220 pounds.  My Kolb Firestar II  503 , just a  2 "x 7/1/2"  piece of aluminum.

Elevator_Trim___Firestar_II_003.jpg

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Both optimists and pessimists contribute to our society. The optimist invents the airplane and the pessimist the parachute. ~Gil Stern

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Sat Jul 28, 2012 11:30 am Post subject: New Firestar II owner - question about elevator oscillations

Eric, Another place to look is the elevator hinges. Check them for wear and slop. That can contribute to your problem.As for trim system, I would avoid putting any weight, no matter how small on the elevator. Study the trim system for the Mk III aircraft and see if you could implement something like they use.

Rick Girard

Do not archive

On Thu, Jul 26, 2012 at 4:24 PM, Jack B. Hart <jbhart(at)onlyinternet.net (jbhart(at)onlyinternet.net)> wrote:

  	  Quote: 	
		  --> Kolb-List message posted by: "Jack B. Hart" <jbhart(at)onlyinternet.net (jbhart(at)onlyinternet.net)>

 At 12:00 PM 7/25/12 -0700, you wrote:

 >--> Kolb-List message posted by: "EricS" <eric_savener(at)yahoo.com (eric_savener(at)yahoo.com)>

 >

 >Hello fellow Kolbers,

 >

...................>

 >I dialed her in with rudder and aileron trim tabs and she'll fly straight

 as an arrow, hands off, in calm conditions.  But when she gets bounced

 around in light turbulence, the elevator will occasionally begin to

 oscillate if I don't keep a firm grip on the stick.  It starts slowly and

 will increase gradually, but I can easily stop it by changing airspeed or

 pitch.  I had a former Firestar pilot and multiple airplane builder fly with

 me in his Rans to watch and he said the boom tube began flexing - that's not

 good.  The immediate solution has been to never let go of the stick.

 >

Eric,

 Pitch stability is much like a pendulum of a clock, in that the greater the

 distance the vertical cg is below the wing and the larger the mass (weight

 of the aircraft) the more stable the aircraft is in pitch.  Each plane will

 seek to oscillate in pitch at its own natural frequency.  As the vertical cg

 moves forward it puts more load on the nose and this causes the nose to

 drop.  As the speed builds and the cg moves toward the rear more lift is

 generated and the nose will rise, etc.

 If your boom tube to cage connection is flexing, I would check out cage and

 boom tube integrity with in the cage.

 Pitch stability can be aggravated and corrected by stick input.

 Jack B. Hart FF004

 Winchester, IN

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Zulu Delta

Mk IIIC

Thanks, Homer GBYM

It isn't necessary to have relatives in Kansas City in order to be unhappy.

   - Groucho Marx

  [quote][b]

_________________
The smallest miracle right in front of you is enough to make you happy....

EricS

Joined: 11 Jul 2012
Posts: 7

Posted: Fri Aug 17, 2012 1:43 pm Post subject: Re: New Firestar II owner - elevator oscillations RESOLVED

I called Kolb and talked to Brian and he had the same suggestions as those above.  I tried them all and eventually what worked is the trim tab.



I built the trim tab so that it adds nose up pitch per Brian's instructions.  My 503 Firestar now trims out around 54 mph and 5,400 RPM versus 63 mph and 5,800 prior to adding the trim tab.  The elevator has never fluttered at this slow speed.



Now when I pitch forward to increase speed, there is additional control cable tension and stick pressure.  Basically, the pilot HAS to keep a hand on the stick to maintain 63-65 mph - the area where the elevator used to occasionally flutter in turbulence.



I am slowly building my "bump" tolerance for winds and thermals, but the elevator has not fluttered in any conditions since adding the trim tab, so for now at least, I consider the problem solved.



Thanks again for everyone's input,

Eric

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Sat Aug 18, 2012 6:18 pm Post subject: New Firestar II owner - question about elevator oscillations

Eric, That's great, and shows just how well this forum can work. I hope you have many safe and happy flying hours.



Rick Girard

do not archive



On Fri, Aug 17, 2012 at 4:43 PM, EricS <eric_savener(at)yahoo.com (eric_savener(at)yahoo.com)> wrote:

  	  Quote: 	
		  --> Kolb-List message posted by: "EricS" <eric_savener(at)yahoo.com (eric_savener(at)yahoo.com)>

  

 I called Kolb and talked to Brian and he had the same suggestions as those above.  I tried them all and eventually what worked is the trim tab.

 

 I built the trim tab so that it adds nose up pitch per Brian's instructions.  My 503 Firestar now trims out around 54 mph and 5,400 RPM versus 63 mph and 5,800 prior to adding the trim tab.  The elevator has never fluttered at this slow speed.

  

 Now when I pitch forward to increase speed, there is additional control cable tension and stick pressure.  Basically, the pilot HAS to keep a hand on the stick to maintain 63-65 mph - the area where the elevator used to occasionally flutter in turbulence.

  

 I am slowly building my "bump" tolerance for winds and thermals, but the elevator has not fluttered in any conditions since adding the trim tab, so for now at least, I consider the problem solved.

 

 Thanks again for everyone's input,

 Eric

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=381106#381106

 

 

 

 

 

 

 

 ===========

 arget="_blank">http://www.matronics.com/Navigator?Kolb-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

 ===========

 

 

 

 	




-- 

Zulu Delta

Mk IIIC

Thanks, Homer GBYM

It isn't necessary to have relatives in Kansas City in order to be unhappy.

   - Groucho Marx



 

  [quote][b]

_________________
The smallest miracle right in front of you is enough to make you happy....

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