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Ultrastar aileron bellcrank?

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Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Wed May 07, 2008 5:56 pm Post subject: Ultrastar aileron bellcrank?

I've seen several references to cracking and failure of the Ultrastar 

aileron bellcrank and a recommended modification, but nothing on exactly 

what the fix is.  I'm pretty sure mine doesn't have this fix, which makes 

me nervous... does anybody (John Hauck?) have drawings or photographs of 

the modified part?



Would love to see pix of the inboard wing spar collar mod too...



-Dana

--

  Resist militant "normality" -- A mind is a terrible thing to erase.

John Hauck

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

Posted: Wed May 07, 2008 6:24 pm Post subject: Ultrastar aileron bellcrank?

> I've seen several references to cracking and failure of the Ultrastar

 	  Quote: 	
		   aileron bellcrank and a recommended modification, but nothing on exactly 

 what the fix is.  I'm pretty sure mine doesn't have this fix, which makes 

 me nervous... does anybody (John Hauck?) have drawings or photographs of 

 the modified part?



 Would love to see pix of the inboard wing spar collar mod too...



 -Dana


	




Dana:



There are two aileron bell cranks on the US.  The upper and a larger complex 

one the aileron push/pull tubes connect to attached to the boom.



I had a failure of the upper, the small one above the lower bell crank.  My 

fuselage was welded at the factory.  The small tube brace was not welded to 

stabalize it.  Homer felt it was not needed on the factory cages.  The plans 

clearly show a small tube strut welded to the rear of the upper aileron bell 

crank and was meant to be used by those builders welding their own kit.



The large bell crank on the bottom of the boom tube pivots on a 1/4" bolt 

welded to a curved plate and riveted to the boom, IIRC.  I have the old US 

plans somewhere.  They show in detail all this stuff.  I put a Z brace made 

of 4130 strip to the bolt end after the bell crank was installed, riveting 

it to the boom.  I did not like all that lateral stress on a bolt welded and 

braced on one end only.



My 1984 US did not have a collar on the inboard rib.  It used two 4130 tubes 

inside the main spar.  Did not do much to prevent wing twist.  Heavy aileron 

input would be canceled out by the wing twisting.  The old US had to be 

flown gently or one could get into trouble.



john h

mkIII

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

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Wed May 07, 2008 7:06 pm Post subject: Ultrastar aileron bellcrank?

At 10:22 PM 5/7/2008, John Hauck wrote:



 	  Quote: 	
		  There are two aileron bell cranks on the US.  The upper and a larger 

complex one the aileron push/pull tubes connect to attached to the boom.



I had a failure of the upper, the small one above the lower bell 

crank.  My fuselage was welded at the factory.  The small tube brace was 

not welded to stabalize it.  Homer felt it was not needed on the factory 

cages.  The plans clearly show a small tube strut welded to the rear of 

the upper aileron bell crank and was meant to be used by those builders 

welding their own kit.


	


John, thanks, I see it now... it's a 1/4" tube running diagonally from the 

vertical tube that drives the rear crank to the horizontal tube that's 

driven by the pushrod from the control stick torque tube.  Definitely not 

on mine, and not easy to weld in place, either, since the assembly can't be 

removed from the fuselage.  Hmmm, perhaps a bolted bracket between the 

bolts holding the rod ends?



 	  Quote: 	
		  The large bell crank on the bottom of the boom tube pivots on a 1/4" bolt 

welded to a curved plate and riveted to the boom, IIRC.  I have the old US 

plans somewhere.  They show in detail all this stuff.  I put a Z brace 

made of 4130 strip to the bolt end after the bell crank was installed, 

riveting it to the boom.  I did not like all that lateral stress on a bolt 

welded and braced on one end only.


	


I don't like it, either.  Now that you mention it I see that brace is on 

the plans as well (and not on my plane).  At least that one's easy to retrofit.



 	  Quote: 	
		  My 1984 US did not have a collar on the inboard rib.  It used two 4130 

tubes inside the main spar.  Did not do much to prevent wing twist.  Heavy 

aileron input would be canceled out by the wing twisting.  The old US had 

to be flown gently or one could get into trouble.


	


The one day I flew the plane in excessive turbulence I could see the wings 

twisting.  That seems like a less urgent change, though.



-Dana



do not archive

--

  CanYouFixTheSpaceBarOnMyKeyboard?

jb92563

Joined: 23 Mar 2007
Posts: 314
Location: Southern California

Posted: Thu May 08, 2008 11:27 am Post subject: Re: Ultrastar aileron bellcrank?

Hmmm....better check my bellcranks out as well.



Wing twisting around the main spar tube?.....yikes



I hope it had a dampening effect on the turbulence inputs and not a divergent effect.



Still working to get airbourne with my US.



Just need to take the engine out and pressure test to see why the Fan side front cylinder is running hot, this weekend.



If I can't solve it, the Cuyuna 430 is going in the UL-202's place until I get it rebuilt.



Once that is resolved I'm going flying at my Test Pilot area, El Mirage Dry lake.



Thanks for the good heads up Dana and John.

_________________
Ray

Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
Schreder HP-11 Glider
Grob 109 Motorglider

Do Not Archive

jb92563

Joined: 23 Mar 2007
Posts: 314
Location: Southern California

Posted: Thu May 08, 2008 11:40 am Post subject: Re: Ultrastar aileron bellcrank?

I was thinking about the wing twisting and wondered if a second wing strut from the trailing edge to a couple feet before the existing struts wing attach point would help. 



Sortof like a Y branch off the main strut going to the trailing edge, and clamped on to avoid putting holes and weakening the main strut.



Perhaps the twisting is not really a big problem except in extreme conditions?



I suppose the Kolb's wings have been twisting this way for some time already with out any detrimental effect?

_________________
Ray

Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
Schreder HP-11 Glider
Grob 109 Motorglider

Do Not Archive

John Hauck

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

Posted: Thu May 08, 2008 12:08 pm Post subject: Ultrastar aileron bellcrank?

> I was thinking about the wing twisting and wondered if a second wing 

strut from the trailing edge to a couple feet before the existing struts 

wing attach point would help.

 	  Quote: 	
		  

 > Perhaps the twisting is not really a big problem except in extreme 
	


conditions?

 	  Quote: 	
		  

 I suppose the Kolb's wings have been twisting this way for some time 

 already with out any detrimental effect?



 --------

 Ray


	


Ray:



The problem was corrected by replacing the two internal tubes off the 

inboard rib with a collar.  Really stiffened up the Kolb wing in twist.



I would not attach a strut from the trailing edge if it were my airplane. 

The trailing edge is not a spar, nor is the leading edge.



The wing twist when the ailerons are operated.  The more aileron input the 

more wing twist.  Wing twist cancels out aileron input.  Yes, one could get 

into trouble in some situations.  The Firestar was a great improvement over 

the US in this respect.



I wouldn't bet my butt on your last statement above.



john h

mkIII

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

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Thu May 08, 2008 3:44 pm Post subject: Ultrastar aileron bellcrank?

At 03:40 PM 5/8/2008, jb92563 wrote:



 	  Quote: 	
		  I was thinking about the wing twisting and wondered if a second wing strut 

from the trailing edge to a couple feet before the existing struts wing 

attach point would help.


	


As John H. said, I don't think that'd be a good idea.  Adding a collar 

seems to be the better fix:

http://tinyurl.com/5krl9m



 	  Quote: 	
		  Perhaps the twisting is not really a big problem except in extreme conditions?



I suppose the Kolb's wings have been twisting this way for some time 

already with out any detrimental effect?


	


Except for the fact that the US's roll rate is not breathtaking, I don't 

think it's a big deal.  I haven't heard of any failures due to the 

twisting.  Only once, flying in turbulent conditions that I wished I hadn't 

taken off into, did I actually see the effect.  I may look into the collar 

if I have to open up the wings for any other reason.  The aileron bellcrank 

fix I'll do as soon as the tubing arrives.



-Dana

--

  Refuse Novocain... Transcend Dental Medication.

jbhart(at)onlyinternet.ne
Guest

Posted: Fri May 09, 2008 3:27 am Post subject: Ultrastar aileron bellcrank?

Dana,



There is a solution to the problem of slow roll rate and wing twist.  

Shorten the chord of the aileron.  This will reduce aileron dynamic loading 

so that ailerons can be more easily displaced.  And at the same time it 

reduces the amount of twisting moment which the aileron subjects the wing 

for a given aileron tip displacement.  This in turn removes significant load 

from the aileron control mechanism.  



I built one of the early FireFlys and after flying it a few hours, I reduced 

the aileron chord to nine inches.  As a result, I have a FireFly that is 

very light on the controls and it flys like a P-51 if you keep the speed up. 

 No trouble flying in the middle of the day or during windy conditions, and 

I can fly it cross country in the middle of the day with out a sore shoulder.



Jack B. Hart FF004

Winchester, IN

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Fri May 09, 2008 3:45 am Post subject: Ultrastar aileron bellcrank?

At 08:14 AM 5/9/2008, Jack B. Hart wrote:



 	  Quote: 	
		  There is a solution to the problem of slow roll rate and wing twist.

Shorten the chord of the aileron.  This will reduce aileron dynamic loading

so that ailerons can be more easily displaced.  And at the same time it

reduces the amount of twisting moment which the aileron subjects the wing

for a given aileron tip displacement.  This in turn removes significant load

from the aileron control mechanism...


	


Shortening the aileron chord would certainly reduce control forces, but it 

won't increase the roll rate for a given aileron deflection.  It takes a 

certain amount of aerodynamic force to cause a certain roll rate; with less 

aileron you need more deflection to achieve that same force.  I don't have 

a problem with the stick force.  The real solution, as John H. and others 

have pointed out, is to reinforce the wing spar attachment.



I'm currently not up for a project as large as rebuilding the ailerons.  If 

I was, I think I'd leave the chord alone but split them, and make the inner 

half into flaps... but that's a project for another year.



-Dana

--

  Campaigns to bearproof all garbage containers in some national parka have 

been difficult, because as one biologist put it, "There is a considerable 

overlap between the intelligence levels of the smartest bears and the 

dumbest tourists."

jbhart(at)onlyinternet.ne
Guest

Posted: Fri May 09, 2008 3:49 pm Post subject: Ultrastar aileron bellcrank?

At 07:42 AM 5/9/08 -0400, you wrote:

 	  Quote: 	
		  

Shortening the aileron chord would certainly reduce control forces, but it 

won't increase the roll rate for a given aileron deflection.  It takes a 

certain amount of aerodynamic force to cause a certain roll rate; with less 

aileron you need more deflection to achieve that same force.  I don't have 

a problem with the stick force.  The real solution, as John H. and others 

have pointed out, is to reinforce the wing spar attachment.




	


Dana,



You are correct in that a shorter chord aileron will not provide the same 

roll rate as a longer chord aileron for the same angular displacement.  



If one cuts the aileron chord in half, you have to about double the 

displacement to get the same change in lift for the same air speed.  In 

doing this the center of pressure of the short chord aileron will be at 

one-fourth as apposed to one-half the chord for the full chord aileron.  If 

one flys both ailerons at the same speed the full aileron dynamic load will 

be 1.2 times that of the short aileron.  This means the bell crank torque 

required to hold the full aileron in position will be 2.4 times that of the 

half chord aileron. 



All of the above would be true if the wing was perfectly stiff.  But in 

reality, the tail of the wing kicks up and lowers the relative AOA from what 

it should be.  And so one will see a slower roll rate from the full aileron 

than the half chord aileron.  If you want to reduce wing warping use shorter 

chord ailerons with greater displacement.



Adding a steel root rib as used in the FireFly does nothing for the main 

spar attachment point but it will help to transfer some of the twist load to 

the wing rear attachment point.  But it will not completely stiffen the 

whole wing.  High roll rates at speed will still warp or twist the wing.



Fly safe



Jack B. Hart FF004

Winchester, IN

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Fri May 09, 2008 5:06 pm Post subject: Ultrastar aileron bellcrank?

At 08:35 PM 5/9/2008, Jack B. Hart wrote:



 	  Quote: 	
		  If one cuts the aileron chord in half, you have to about double the

displacement to get the same change in lift for the same air speed.  In

doing this the center of pressure of the short chord aileron will be at

one-fourth as apposed to one-half the chord for the full chord aileron.


	


OK, I'll buy that.  Not sure it's really linear but let's go with it.



 	  Quote: 	
		  If one flys both ailerons at the same speed the full aileron dynamic load 

will

be 1.2 times that of the short aileron.  This means the bell crank torque

required to hold the full aileron in position will be 2.4 times that of the

half chord aileron.


	


Where do you get the 1.2 from... and thus the 2.4?



If you have to move the aileron twice as far to get the same effect (same 

aerodynamic force), but the moment arm to the center of pressure is halved, 

then the torque applied to the aileron is also halved.  However, you have 

to move the stick twice as far (not possible on the US, at least not on mine).



To get the same control authority for a given stick deflection, then you 

have to adjust the control linkage to get double the aileron movement for 

the same stick deflection, which multiplies the torque by a factor of 

two... net result, same stick force.



 	  Quote: 	
		  All of the above would be true if the wing was perfectly stiff.  But in

reality, the tail of the wing kicks up and lowers the relative AOA from what

it should be.  And so one will see a slower roll rate from the full aileron

than the half chord aileron.  If you want to reduce wing warping use shorter

chord ailerons with greater displacement.


	


I don't see that at all.  If the rolling force (regardless of the aileron 

size) is the same, then the amount of twist it causes in the wing should be 

the same.



 	  Quote: 	
		  Adding a steel root rib as used in the FireFly does nothing for the main

spar attachment point but it will help to transfer some of the twist load to

the wing rear attachment point.  But it will not completely stiffen the

whole wing.  High roll rates at speed will still warp or twist the wing.


	


The modification suggested for the US is not a steel root rib (which it 

already has), but a collar to reinforce the main spar attachment to the 

root rib, keep the spar tube round, and keep the spar from twisting... 

though I'm not convinced how the modification, as I understand it, would 

help that much.



-Dana

--

  If at first you don't succeed, skydiving is not for you.

John Hauck

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

Posted: Fri May 09, 2008 7:43 pm Post subject: Ultrastar aileron bellcrank?

 	  Quote: 	
		   All of the above would be true if the wing was perfectly stiff.  But in

 reality, the tail of the wing kicks up and lowers the relative AOA from 

 what

 it should be.  And so one will see a slower roll rate from the full 

 aileron

 than the half chord aileron.  If you want to reduce wing warping use 

 shorter

 chord ailerons with greater displacement.



 Adding a steel root rib as used in the FireFly does nothing for the main

 spar attachment point but it will help to transfer some of the twist load 

 to

 the wing rear attachment point.  But it will not completely stiffen the

 whole wing.  High roll rates at speed will still warp or twist the wing.



 Fly safe



 Jack B. Hart FF004


	




Jack H:



I have a feeling you don't know what you are talking about.  You say, "But 

in reality, the tail of the wing kicks up and lowers the relative AOA from 

what it should be."  How do you know this is reality?  Have you been there 

and done that?



I believe I tried previously to explain what actually happens to the early 

model US wing when the ailerons are actuated.  The entire wing twist with 

the main spar because the main spare "oil cans".  The two internal tubes 

butt welded to the inboard rib, then riveted to the inside of themain spar, 

top and bottom, can not keep the main spar in its original round shape. 

This effectively cancels out all the aileron input.  No, it does not happen 

as the result of docile control input.  One has to be a bit agressive to 

twist the wing.



Old Kolb discovered there was a better way to attach the main spar to the 

inboard rib, thus, the 4130 ring.  Some models the ring slipped inside the 

main spar and some models the spar slipped inside the ring.  My FS had the 

ring and it fixed the problem.  No more wing twist when the ailerons were 

actuated.



To the best of my knowledge, all the subsequent model Kolbs, after the early 

US, do not suffer from wing twist.  The problem was solved.



john h

mkIII

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

jbhart(at)onlyinternet.ne
Guest

Posted: Wed May 14, 2008 6:35 pm Post subject: Ultrastar aileron bellcrank?

Dana & List,



I apologize for tossing out some numbers with out explanation.  I used a 

quick graphical solution to come up with relative numbers for an aileron 

one-half the chord.



It rained today so I worked up a similar graphical approach to match the 

modifications I have made to the FireFly.  The results can be seen at:



http://www.thirdshift.com/jack/firefly/firefly139.html



I inserted some responses below.



At 08:57 PM 5/9/08 -0400, you wrote:

 	  Quote: 	
		  



If you have to move the aileron twice as far to get the same effect (same 

aerodynamic force), but the moment arm to the center of pressure is halved, 

then the torque applied to the aileron is also halved.  However, you have 

to move the stick twice as far (not possible on the US, at least not on mine).




	


If your maximum aileron down deflection is 20 degrees, there is more than 

enough stick deflection.



 	  Quote: 	
		  To get the same control authority for a given stick deflection, then you 

have to adjust the control linkage to get double the aileron movement for 

the same stick deflection, which multiplies the torque by a factor of 

two... net result, same stick force.




	


In my case, I was able to reduce "Tee" hole spacing to gain greater 

mechanical advantage and therefore reduce stick force required.



 	  Quote: 	
		  

I don't see that at all.  If the rolling force (regardless of the aileron 

size) is the same, then the amount of twist it causes in the wing should be 

the same.




	


All that extra effort that you have to exert to deflect the aileron has to 

go some where.  Some of it goes into twisting the aileron torque tube.  The 

rest and probably most of it goes into twisting the wing ribs about the main 

spar. 



 	  Quote: 	
		  

The modification suggested for the US is not a steel root rib (which it 

already has), but a collar to reinforce the main spar attachment to the 

root rib, keep the spar tube round, and keep the spar from twisting... 

though I'm not convinced how the modification, as I understand it, would 

help that much.




	


In the FireFly, there is one pin through the main spar attachment point to 

the cage. Also a second through the rear wing universal attachment point.  

And two more through the wing struts.  The only thing that keeps the wing 

from kicking up in the back with down aileron is the most inboard steel rib. 

 This leaves the outboard portion of the wing to progressively twist up 

under this condition.  Since the airfoil lift profile usually centers over 

the main spar this twist is not usually harmful. 



I hope this helps to explain why reasonably small ailerons may be of 

benefit.  Would I change back?  No way!  



Jack B. Hart FF004

Winchester, IN

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