Matronics Email Lists :: View topic - Longtudinal Stability of KIS TR-1

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Longtudinal Stability of KIS TR-1

Matronics Email Lists Forum Index -> KIS-List

View previous topic :: View next topic

Author Message

BlueSkyFlier

Joined: 27 Jan 2011
Posts: 74
Location: UK

Posted: Fri Apr 15, 2011 1:06 pm Post subject: Longtudinal Stability of KIS TR-1

Since I am quite likely to fly a TR-1 again (if I'm not seduced by a snazzy CT2K ) I would like to clear up the remaining fuzzy point (for me that is) about the TR-1 aerodynamic configuration which would enable determination of the optimal location of the main landing gear.



Does anyone on this forum know the location of the the neutral point (Xn) of the TR-1 in relation the mean aerodynamic chord (MAC for short). We know what the CoG limits are in terms of MAC, but the distance between CoG and  Xn is a very important parameter in longitudinal stability and it would be great if such knowledge can be shared if it exists (as I'm sure it must).



[The LAA here in the UK is of the opinion that the TR-1 has marginal longitudinal stability and the original flight test results seemed to support that.]



It is understood that Xn is probably a locus and not a single point, but I'll take anything I can get as starting point and work from that )



Thanks in advance.



- Alfred

_________________
_________________________________________

sstearns2(at)yahoo.com
Guest

Posted: Fri Apr 15, 2011 3:26 pm Post subject: Longtudinal Stability of KIS TR-1

I think the primary problem with longitudinal stability is the very low stick forces in pitch.  This can be cured by adding an extension to the chord of the elevator.  I added about 2" in chord to mine and the stick forces are much better.  I also think that the elevator extension may cure the pitch down problem.

  

 What flight test data are they looking at?  

  

 Scott



--- On Fri, 4/15/11, BlueSkyFlier <bleuskyfly(at)teledynamix.com> wrote:



  	  Quote: 	
		  

From: BlueSkyFlier <bleuskyfly(at)teledynamix.com>

Subject: Longtudinal Stability of KIS TR-1

To: kis-list(at)matronics.com

Date: Friday, April 15, 2011, 2:06 PM



 --> KIS-List message posted by: "BlueSkyFlier" <bleuskyfly(at)teledynamix.com (bleuskyfly(at)teledynamix.com)>



Since I am quite likely to fly a TR-1 again (if I'm not seduced by a snazzy CT2K ) I would like to clear up the remaining fuzzy point (for me that is) about the TR-1 aerodynamic configuration which would enable determination of the optimal location of the main landing gear.



Does anyone on this forum know the location of the the neutral point (Xn) of the TR-1 in relation the mean aerodynamic chord (MAC for short). We know what the CoG limits are in terms of MAC, but the distance between CoG and  Xn is a very important parameter in longitudinal stability and it would be great if such knowledge can be shared if it exists (as I'm sure it must).



[The LAA here in the UK is of the opinion that the TR-1  has marginal longitudinal stability and the original flight test results seemed to support that.]



It is understood that Xn is probably a locus and not a single point, but I'll take anything I can get as starting point and work from that )



Thanks in advance.



- Alfred



--------

_________________________________________





Read this topic online here:



http://forums.matronics.com/vishare, and much much onics.com/Navigator?KIS-List" target=_blank>http://www.matronics.com/Navisp;              - MATRONICS WEB FObsp;               -Matt Dralle, List Adontribution" =======





	
 [quote][b]

BlueSkyFlier

Joined: 27 Jan 2011
Posts: 74
Location: UK

Posted: Fri Apr 15, 2011 3:28 pm Post subject: Re: Longtudinal Stability of KIS TR-1

Attached the performance figures of what is supposed to be a latter day hot ship, the Flight Design CT-LSA. Doesn't that just show how effectively the TR-1 still competes with the best. With MTOW the TR-1 with 130hp will manage over 1000 ft/min climb and the usefull load is effectively the same. Comparative takeoff and landing distances at full weight are not different enough to worry about.



So the primary advantages of the CT-LSA lie in the ease of boarding (mainly of interest to womenfolk), lower stall speed (if you can stop it floating of the end of the runway) and some saving on fuel ( which matters only for long journeys). On the other hand the TR-1 can be fitted with power to nudge it up to the 180 kts mark due to its much higher Vne  -- and the TR-1 will surely fly quite happily in conditions which will ground the CT. So, when the price is factored in the TR-1 doesn't have to stand back for the competition at all. 



Mmmm ... I'll have to go fly the CT2K then to make up my mind ) IF I can get the main gear position sorted out the TR-1 probably still holds the edge if the price differential is big right. Now if we can just get a smidgin of factory support again ... ) 



Now would you believe it!! ... as I was writing that I got a call from James in the US asking me to send over pictures of my wing root dimensions so that they can check it against the dimensions of the factory stuff. Spooky ... brrrr )

_________________
_________________________________________

BlueSkyFlier

Joined: 27 Jan 2011
Posts: 74
Location: UK

Posted: Fri Apr 15, 2011 3:31 pm Post subject: Re: Longtudinal Stability of KIS TR-1

Chuckle .... completely forgot to attach the CT-LSA peformance figures to previous message, what with all the excitement of receiving a call from Pulsar )



Here it is attached now ....



In response to Scott's comment: 

 	  Quote: 	
		  I think the primary problem with longitudinal stability is the very low stick forces in pitch. This can be cured by adding an extension to the chord of the elevator. 	




[... don't know why the rest is in bold font but can't change it]

Stick forces per se don't factor into the static stability equation Scott, because stability is measured with locked controls after perturbing the flight path.  The main culprits in this affair are (i) distance between MACs of wing and tail plane (squared) and (ii) lift multiplied by distance between Xn and CoG.



So when more lift is needed (to slow the descent during landing) the negative pitching moment generated by lift acting across the distance between Xn and CoG -- as compared to opposing elevator moment -- begins to matter [Xn must be behind CoG for static stability.

CT-LSA Performance Figures.jpg

Description:

Figures taken from section 6 of the CT-LSA POH ...

Filesize:

53.25 KB

Viewed:

9178 Time(s)

_________________
_________________________________________

BlueSkyFlier

Joined: 27 Jan 2011
Posts: 74
Location: UK

Posted: Sat Apr 16, 2011 1:08 pm Post subject: Re: Longtudinal Stability of KIS TR-1

Does anyone know who originally did the aerodynamic design of the KIS airframe?



And how to get hold of him of course )



Thanks,

           Alfred

_________________
_________________________________________

lgdavid(at)roadrunner.com
Guest

Posted: Sat Apr 16, 2011 6:50 pm Post subject: Longtudinal Stability of KIS TR-1

I believe Vance Jaqua was involved.  Unfortunately, he passed away a 

couple of years ago.  I can guarantee that if he were still alive, he 

would have loved being involved in these discussions. Larry



On 4/16/2011 2:08 PM, BlueSkyFlier wrote:

 	  Quote: 	
		   



 Does anyone know who originally did the aerodynamic design of the KIS airframe?



 And how to get hold of him of course )



 Thanks,

             Alfred



 --------

 _________________________________________





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=337149#337149

sstearns2(at)yahoo.com
Guest

Posted: Sat Apr 16, 2011 7:10 pm Post subject: Longtudinal Stability of KIS TR-1

Martin Hollmann did the basic structural sizing.  Vance did some engineering and wrote the manuals.  Some of the metal parts were copied from the first generation lancairs as I remember.

  

 My impression is that the aerodynamic design was basically doing what looked right, which can be surprisingly effective with a conventional airplane like we have.   

  

 Scott



--- On Sat, 4/16/11, Larry David <lgdavid(at)roadrunner.com> wrote:



  	  Quote: 	
		  

From: Larry David <lgdavid(at)roadrunner.com>

Subject: Re: Re: Longtudinal Stability of KIS TR-1

To: kis-list(at)matronics.com

Date: Saturday, April 16, 2011, 7:48 PM



 --> KIS-List message posted by: Larry David <lgdavid(at)roadrunner.com (lgdavid(at)roadrunner.com)>



I believe Vance Jaqua was involved.  Unfortunately, he passed away a 

couple of years ago.  I can guarantee that if he were still alive, he 

would have loved being involved in these discussions. Larry



On 4/16/2011 2:08 PM, BlueSkyFlier wrote:

 	  Quote: 	
		   -->  KIS-List message posted by: "BlueSkyFlier"<bleuskyfly(at)teledynamix.com (bleuskyfly(at)teledynamix.com)>



 Does anyone know who originally did the aerodynamic design of the KIS airframe?



 And how to get hold of him of course )



 Thanks,

              Alfred



 --------

 _________________________________________





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=337149#337149





&g://www.matronics.com/Navigator?KIS-List" sp;--> http://f=             - List Contributionsp;                     &bsp;--> 
	




	
 [quote][b]

BlueSkyFlier

Joined: 27 Jan 2011
Posts: 74
Location: UK

Posted: Sun Apr 17, 2011 9:22 am Post subject: Re: Longtudinal Stability of KIS TR-1

Thank you Scott. I have tracked Martin Hollman down, but I'll defer establishing contact until I know if there is still life left in Pulsar - who knows, perhaps they can come up with a replacement TR-1 wing that meets spec.



I'm not of a mind to flog a dead horse, so I'll let this one trot to its own tune )

_________________
_________________________________________

richard_trickel(at)yahoo.
Guest

Posted: Mon Apr 18, 2011 11:07 am Post subject: Longtudinal Stability of KIS TR-1

The longitude stability on the plane is pretty good.  It was tested out by many pilots and satisfied FAA requirements in test by Dave Morse. (Test Pilot) Actual technical information I don`t know.  That was a long time ago.  I always though the netural point of mac was the most aft CG location some where around 31%.  But rember I am not an engineer.   Scott/Mark some help here.  The LAA (PFA) made a statement that the plane was not stable  based on what results.  This is the same outfit that would not license a Cruiser which has 4 seats.  It was only licensed as a two seater. These are the experts there.  I paid a lot of money for extra documentation for them for nothing.  



--- On Sun, 4/17/11, Scott Stearns <sstearns2(at)yahoo.com> wrote:

  	  Quote: 	
		  

From: Scott Stearns <sstearns2(at)yahoo.com>

Subject: Re: Re: Longtudinal Stability of KIS TR-1

To: kis-list(at)matronics.com

Date: Sunday, April 17, 2011, 3:08 AM



      Martin Hollmann did the basic structural sizing.  Vance did some engineering and wrote the manuals.  Some of the metal parts were copied from the first generation lancairs as I remember.

  

 My impression is that the aerodynamic design was basically doing what looked right, which can be surprisingly effective with a conventional airplane like we have.   

  

 Scott



--- On Sat, 4/16/11, Larry David <lgdavid(at)roadrunner.com> wrote:



  	  Quote: 	
		  

From: Larry David <lgdavid(at)roadrunner.com>

Subject: Re: Re: Longtudinal Stability of KIS TR-1

To: kis-list(at)matronics.com

Date: Saturday, April 16, 2011, 7:48 PM



 --> KIS-List message posted by: Larry David <lgdavid(at)roadrunner.com>



I believe Vance Jaqua was involved.  Unfortunately, he passed away a 

couple of years ago.  I can guarantee that if he were still alive, he 

would have loved being involved in these discussions. Larry



On 4/16/2011 2:08 PM, BlueSkyFlier wrote:

 	  Quote: 	
		   -->  KIS-List message posted by: "BlueSkyFlier"<bleuskyfly(at)teledynamix.com>



 Does anyone know who originally did the aerodynamic design of the KIS airframe?



 And how to get hold of him of course )



 Thanks,

             Alfred



  --------

 _________________________________________





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=337149#337149





&g://www.matronics.com/Navigator?KIS-List" sp;--> http://f=             - List Contributionsp;                     &bsp;--> 
	




	
 	  Quote: 	
		  



=nofollow target=_blank>http://www.matronics.com/Navigator?KIS-List

et=_blank>http://forums.matronics.com

llow target=_blank>http://www.matronics.com/contribution



	


	


 [quote][b]

mantafs(at)earthlink.net
Guest

Posted: Tue Apr 19, 2011 6:49 am Post subject: Longtudinal Stability of KIS TR-1

I did geometry based stability calculations for both the TR1 and TR4 and they had good margins (except LP in pitch) in all axis when operated in the CG range specified in the manual.  In fact after both my calculations and those done by Vance it was determined that the allowable aft CG limit could be slightly expanded.  A student at calpoly that I advised for their senior project made a computer model of the TR4 and used Nastran and the stability module to evaluate stability on the TR4 and again had good margins (except LP in pitch) in all axis.  The only issue was the X plot and this just showed a problem with the main gear placement.  Keep in mind that all of this was geometry and calculation based and not based on experimental data.  Of course many pilots including a few test pilots have flown the TR aircraft.  I do not know of any issues with stability but no real stability flight test data has ever been taken that I know of.



LP is long period and many aircraft at or near their aft CG are not stable in LP with the stick free and some are not even with the stick fixed.  Even a Cessna 150 is not with stick free.  Maybe this is what the PFA/LAA means by not stable longitudinally.



But there is an issue with stick force both in terms of balance and in terms of just stick force per G.  This lack of stick force also can effect longitudinal stability free stick.  Using a spring pitch trim system is also not good for longitudinal stability free stick.  I would stick with a trim tab.



Mark 

--

BlueSkyFlier

Joined: 27 Jan 2011
Posts: 74
Location: UK

Posted: Tue Apr 19, 2011 7:43 am Post subject: Re: Longtudinal Stability of KIS TR-1

Thanks for the information above Mark. Good to hear that the aft CoG margin is not too critical/sensitive. The LAA opinion about 'marginal' longitudinal stability is indeed with regard to long period, but I was taught that the pilot is supposed to control that anyway.



I know of one instance where a TR-1 autopilot installation got out of sync with the LP and caused a few anxious moments, but it ended well and the owner subsequently installed a OFF switch for the autopilot on the stick.



On the TR-1 I bought the LAA imposed a requirement on the builder to install a 'down spring' on the elevator - this was a bungee chord which pulled the elevator down. I did not like that and 'rendered it ineffective' after which it felt much better on the stick and I could fly it at various speeds without messing around with the trim all the time.



With the 20 to 25 landings I did in the TR-1 it always behaved well even if I didn't (by dropping it steeply and then pulling it up strong and short). As Scott and Mark pointed out the only apparent weakness is that the gear position generates a pitching moment if the touchdown is somewhat less than gentle. That can be fixed with relative ease.

_________________
_________________________________________

bakerocb

Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

Posted: Wed Apr 20, 2011 3:14 am Post subject: Longtudinal Stability of KIS TR-1

4/20/2011



Hello Alfred, You wrote: "That can be fixed with relative ease."



How would you go about fixing this? Thanks.



'OC' Baker Says: "The best investment we can make is the time and effort to 

gather and understand knowledge."



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



Time: 08:45:44 AM PST US

Subject: Re: Longtudinal Stability of KIS TR-1

From: "BlueSkyFlier" <bleuskyfly(at)teledynamix.com>

Thanks for the information above Mark. ......SKIP .....



With the 20 to 25 landings I did in the TR-1 it always behaved well even if 

I didn't

(by dropping it steeply and then pulling it up strong and short). As Scott

and Mark pointed out the only apparent weakness is that the gear position 

generates

a pitching moment if the touchdown is somewhat less than gentle. That

can be fixed with relative ease.

Display posts from previous:

	Matronics Email Lists Forum Index -> KIS-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum