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Elevator Trim

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jeynon2

Joined: 25 Oct 2007
Posts: 24
Location: Southern Illinois

Posted: Wed Jun 25, 2008 8:39 am Post subject: Elevator Trim

I have recently received the new trim system for my Lightning to replace the bungee trim, but I am confused about how to balance the elevator.  Is the balance bungee still used?



John Eynon

Lightning kit #53

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info(at)flylightning.net
Guest

Posted: Wed Jun 25, 2008 9:15 am Post subject: Elevator Trim

The bungee system is eliminated completely.

Nick 



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EAFerguson(at)aol.com
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Posted: Wed Jun 25, 2008 3:50 pm Post subject: Elevator Trim

In a message dated 6/25/2008 12:43:14 P.M. Eastern Daylight Time,  jeynon2(at)verizon.net writes:

  	  Quote: 	
		  I have    recently received the new trim system for my Lightning to replace the bungee    trim, but I am confused about how to balance the elevator.  Is the    balance bungee still used?

	


 

 I recently added the new trim tab system and it's a tremendous improvement,  but pitch control forces were a little heavy.

  

 So - I just added a single 1/2" bungee loop using the old connection on the  elevator pushrod. Flew for the first time today for ~ 1.0 with some touch &  goes. I need less up trim on TO and landing. About 2  spaces down on the  indicator for TO. 

  

 Before I added the bungee, full up trim left me with noticeable up stick  force on final. Now that is gone. I don't even feed in full up on the trim tab.  

  

 One flight, 3 landings; not a significant data base, but tentative results  are favorable.  Your experience may be different. I have no way of  measuring the applied bungee force. 

  

 Do be careful and make your first trials on a long, wide runway. Don't  ask me to define long and wide, but if you're flying out of 1000' unpaved, I  suggest you go somewhere else before connecting the bungee for the first time.  My home field is 5700' by 100'

  

 Has anybody else tried this?

  

 Earl Ferguson

 N17EF

 Atlanta



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pequeajim

Joined: 03 Sep 2006
Posts: 708
Location: New Holland, PA

Posted: Wed Jun 25, 2008 5:03 pm Post subject: Elevator Trim

Earl, I replaced the stock bungee with the new trim tab.  While I have not flown it yet, I did have a question about what to leave in place with the old system.  Perhaps Nick or Buz could answer this one.  I believe we took everything out, but of course the bungee attachments are still on the pushrod.  

   

Jim!  

       

From: owner-lightning-list-server(at)matronics.com [mailto:owner-lightning-list-server(at)matronics.com] On Behalf Of EAFerguson(at)aol.com

 Sent: Wednesday, June 25, 2008 7:47 PM

 To: lightning-list(at)matronics.com

 Subject: Re: Elevator Trim  

  

  

       

In a message dated 6/25/2008 12:43:14 P.M. Eastern Daylight Time, jeynon2(at)verizon.net writes:  

   	  Quote: 	
		    

I have recently received the new trim system for my Lightning to replace the bungee trim, but I am confused about how to balance the elevator.  Is the balance bungee still used?  	
  

    

I recently added the new trim tab system and it's a tremendous improvement, but pitch control forces were a little heavy.  

    

   

    

So - I just added a single 1/2" bungee loop using the old connection on the elevator pushrod. Flew for the first time today for ~ 1.0 with some touch & goes. I need less up trim on TO and landing. About 2  spaces down on the indicator for TO.   

    

   

    

Before I added the bungee, full up trim left me with noticeable up stick force on final. Now that is gone. I don't even feed in full up on the trim tab.   

    

   

    

One flight, 3 landings; not a significant data base, but tentative results are favorable.  Your experience may be different. I have no way of measuring the applied bungee force.   

    

   

    

Do be careful and make your first trials on a long, wide runway. Don't ask me to define long and wide, but if you're flying out of 1000' unpaved, I suggest you go somewhere else before connecting the bungee for the first time. My home field is 5700' by 100'  

    

   

    

Has anybody else tried this?  

    

   

    

Earl Ferguson  

    

N17EF  

    

Atlanta  

  



 

         

  

Gas prices getting you down? Search AOL Autos for fuel-efficient used cars.  

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jeynon2

Joined: 25 Oct 2007
Posts: 24
Location: Southern Illinois

Posted: Thu Jun 26, 2008 6:41 am Post subject: Re: Elevator Trim

I expect that the weight of the unbalanced elevator would be equivalent to nose down trim requiring a certain amount of nose up trim to compensate.  The weight of the elevator pushing down is always the same while the aerodynamic forces acting on the elevator and its trim tab increase with speed, so at higher speeds less compensation is needed.  In either case I would think the additional trim requirements would add to drag.



I like Earl's approach of keeping enough "up bungee" to balance the elevator, but worry that that might retain some of the issues addressed with the new system.



When it comes to flight test time, I am fortunate to have a quiet 8000' by 150' runway available. 



John Eynon

Lightning kit #53





[quote="EAFerguson(at)aol.com"]In a message dated 6/25/2008 12:43:14 P.M. Eastern Daylight Time,  jeynon2(at)verizon.net writes:

  	  Quote: 	
		  I have    recently received the new trim system for my Lightning to replace the bungee    trim, but I am confused about how to balance the elevator.  Is the    balance bungee still used?

	


 

 I recently added the new trim tab system and it's a tremendous improvement,  but pitch control forces were a little heavy.

  

 So - I just added a single 1/2" bungee loop using the old connection on the  elevator pushrod. Flew for the first time today for ~ 1.0 with some touch &  goes. I need less up trim on TO and landing. About 2  spaces down on the  indicator for TO. 

  

 Before I added the bungee, full up trim left me with noticeable up stick  force on final. Now that is gone. I don't even feed in full up on the trim tab.  

  

 One flight, 3 landings; not a significant data base, but tentative results  are favorable.  Your experience may be different. I have no way of  measuring the applied bungee force. 

  

 Do be careful and make your first trials on a long, wide runway. Don't  ask me to define long and wide, but if you're flying out of 1000' unpaved, I  suggest you go somewhere else before connecting the bungee for the first time.  My home field is 5700' by 100'

  

 Has anybody else tried this?

  

 Earl Ferguson

 N17EF

 Atlanta

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N1BZRich(at)aol.com
Guest

Posted: Thu Jun 26, 2008 2:38 pm Post subject: Elevator Trim

The new trim system is designed to completely replace all bungees.   Also, the new trim tab was sized (after many test flights) so as to completely  trim off all pressures during all phases of "cruise" flight.  However, when  you lower the flaps, you are now flying a different wing - a different  airplane.  The trim tab size will trim off most of the nose down pressures  when using up to 30 degrees of flaps and when at 65 to 70 mph on final and  when close to gross weight.  If the aircraft is lighter (more forward CG),  or if you are slower, or if you have more than 30 degrees of flaps you will not  have quite enough up trim.  But again, this was done intentionally and  designed that way.  It is no problem to fly it as set up at any allowable  weight and CG.  The reason it is set up that was is if you trimmed off all  pressures and have to make a last minute go around, you are going to have to  really push forward on the stick to keep the airplane from really wanting to  climb away from you and possibly stall.  It can be a hand full on a last  minute go around with all pressures trimmed off.  With the relatively slow  trim motor it is going to take some time to trim off these pressures during the  go around and you could have your hands full.  Adding a bungee back into  the system will acerbate the problem with a last minute go around (making the  airplane want to climb even more at slow speeds) in addition to causing the  aircraft to feel as if it is neutrally or slightly unstable in pitch during  normal cruise operations.  That is exactly why the bungee system was done  away with.  The new system makes the airplane easier to fly,  especially on long flights and it is certainly easier to maintain.   The slightly heavy elevator feel on final with flaps down is only a slight out  of trim condition, certainly well within the design limits of the  airplane.  

  

 So bottom line, now you know why the system is designed like it is.   With the many test hours that Nick and I have flown it on both the prototype and  the new 2008 demonstrator, we have tested about all the conditions and found  that the current set up is the best for all possible in-flight situations.   If you don't believe me, just read the upcoming September issue of KitPlanes  magazine and see what a PHD in aeronautical engineering that used to teach  at the Navy test pilot school at PAX River had to say about the new trim  system.  But forget what he says in the article about "killing snakes" -  heck, he was a Navy pilot that flew heavies.  

  

 Blue Skies,

 Buz

 PS: I am writing this because I know just how busy Nick is at the  moment.  When you read the July newsletter due out in a day or so, you  will kind of get a feeling just why and how busy he is.  

  



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jeynon2

Joined: 25 Oct 2007
Posts: 24
Location: Southern Illinois

Posted: Thu Jun 26, 2008 3:19 pm Post subject: Re: Elevator Trim

Thanks for your response Earl, and your explanation Buz.  I'll strip her bare and go from there.  It's all theory until she flies.



John Eynon

Lightning kit #53

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N1BZRich(at)aol.com
Guest

Posted: Thu Jun 26, 2008 3:33 pm Post subject: Elevator Trim

In a message dated 6/26/2008 7:22:41 P.M. Eastern Daylight Time,  jeynon2(at)verizon.net writes:

  	  Quote: 	
		  It's all    theory until she flies.

	


 

 Hey John, I like your analogy.  And you are exactly right.  That  is the neat thing about EAB aircraft - you are the builder and you can build  them the way you want.  All of them are different in some way, so as you  said, its all theory until yours flies.  When you get a chance, send me  some updates and photos on your build and I will get it in a future  newsletter.  You never know, something you write might just be the spark  that ignites someone's fuse and gets them started building their  Lightning.  Then "kaboom", someone else has set their hair on fire and is  now building their own airplane.  That's what happened to my hair - several  airplanes ago.  

 Blue skies,

 buz



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