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performance (pitch trim)
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weeav8ter

Joined: 01 Mar 2010
Posts: 16

Posted: Sun Sep 26, 2010 4:52 am Post subject: performance (pitch trim)

I've been reading the concern over runaway trim and thought I  would share my experience with this. Back in, I think, 2007 when Ray Allen came  out with relay II to replace relay I because of problems, we went in and changes  out the relay. 

  

 I was going to go up and test the trim with the new relay and  someone at the hangar had never been up in a 10 and wanted to hop in the right  seat. We took off and I was explaining how you used the trim for climb and then  again when you level off. At about 300' I hit the trim up on my  hat switch and I the trim servo went to full stop up in what seemed  like two nanoseconds. It was so fast that even if I could have reached  the CB it would have been way over with by then. I had to put a really  large amount of pressure on the stick to hold it forward, in fact I ask my  passenger to put his hand on the passenger stick to help me hold forward  pressure just in case my harm gets tired.

  

 I was able to hold the stick forward but it took quite a  bit of pressure but I was then wondering how the hell I was going to flair it in  the landing that way. I hadn't really left the pattern so I just pulled down  wind and told the passenger that it will be ok, under my breath saying I hope.  Anyway as I proceeded downwind and as I pulled back on the power the pressure on  the stick started to degrease. As I pulled the power back more the pressure  continued to decrease. I obviously had to be very gentle and careful on landing  to just let back a certain amount on the stick in landing but the landing  went fine.

  

 I taxied back to the hangar and sat there wondering what the  hell was that. I tested the trim and it worked fine. I decided I was going to go  back up, crazy guy, and see if it would do that again and my passenger decided  he would also try it again so if I needed help holding the stick. I went  up  and waited a little longer before trying the trim but when I did boom  here we go again, being from TX I had to yell yea hah ride um big boy :>}  Anyway same drill on landing and when we landed we took out the RA relay II  and put back in the relay I and went back up problem solved. I called Ray  Allen a little less than happy and the first words out of their mouths was  it wasn't our relay you wired it wrong. We wired it exactly the same way as we  took out and put back in relay I and II. They sent me another relay and  that one worked fine. For some reason the first one was ok as long as there was  no pressure being exerted but with pressure on it it would go nuts.

  

 Anyway as an end to this story, as much as I didn't much care  for the experience it did show me that if I did by accident have a run a way  trim I could still control the plane. However whenever I fly I notice that I  subconsciously always ride with my hand on the stick when the auto pilot is  engaged.

  

 Wayne Edgerton

  

  N602WT

      

  

  

  

             Time:      01:38:30 PM PST    US            Subject:      Re: performance (pitch        trim)            From:      "Bob Turner" <bobturner(at)alum.rpi.edu (bobturner(at)alum.rpi.edu)>       

      

      I've put  pullable CB's for the trim and autopilot right next to each other,  just

      right of center in front of the pilot,  easily reached by the right hand. I'll

      put a  red box around them. My plan is that if the pitch goes nuts, I'll  pull

      both breakers, then sort out the  problem.

      

       --------

      Bob  Turner

      RV-10 QB



   [quote][b]

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Tim Olson

Joined: 25 Jan 2007
Posts: 2872

Posted: Sun Sep 26, 2010 5:27 am Post subject: performance (pitch trim)

Wayne....great story!   You did miss one point in your conclusion though.....yours happened at low airspeed in climbing.  If that would have happened in cruise, I bet the outcome may not have ended the same way....especially with only single full speed trim.  At absolute bare minimum a speed reduction should be installed for slow trim during cruise.  Also, I really think that LESS than full speed would be annoying and perhaps in some cases compromise safety for some pilots.  So for me, dual speed is a big deal.

Personally though, I think at 170+ kts that a full-speed nose up trim runaway to the stops would stand a good chance of bending something.

And if someone were screwing around doing low passes at high speed for show and they got full speed nose down at 175kts and 100' they'd be toast by the tome they'd recognize the problem.



At lower climbout speeds though, it's totally different, and it's nice to hear that you can fight the trim by arm strength.

Tim



On Sep 26, 2010, at 7:45 AM, "Wayne Edgerton" <w.edgerton(at)verizon.net> wrote:



[quote] I've been reading the concern over runaway trim and thought I would share my experience with this. Back in, I think, 2007 when Ray Allen came out with relay II to replace relay I because of problems, we went in and changes out the relay.

  

 I was going to go up and test the trim with the new relay and someone at the hangar had never been up in a 10 and wanted to hop in the right seat. We took off and I was explaining how you used the trim for climb and then again when you level off. At about 300' I hit the trim up on my hat switch and I the trim servo went to full stop up in what seemed like two nanoseconds. It was so fast that even if I could have reached the CB it would have been way over with by then. I had to put a really  large amount of pressure on the stick to hold it forward, in fact I ask my passenger to put his hand on the passenger stick to help me hold forward pressure just in case my harm gets tired

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carl.froehlich(at)verizon
Guest

Posted: Sun Sep 26, 2010 6:34 am Post subject: performance (pitch trim)

Following this thread I note what seems to be a lack of confidence in the Ray Allen relays.  

   

As we know, the Infinity Stick top hat switch is not suitable to be used for trim without relays.  I built my own relay stack for my RV-8A as I viewed the Ray Allen relays too expensive for such a simple job.   I have 4 standard but good 12 volt relays from Allied Electronics, one each for trim up, down, left and right.  Simple, cost effective and exceptionally reliable.  I also used the same DPDT relay to provide the reversing function for the stick flap switch.  These relays typically cost $5 to $7 each.  Wiring diagram available off list if interested.  

   

Carl  

RV-8A (570 hrs)  

RV-10 (engine hung yesterday!)  

   

       

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Tim Olson

 Sent: Sunday, September 26, 2010 9:22 AM

 To: rv10-list(at)matronics.com

 Subject: Re: performance (pitch trim)  

  

  

     

Wayne....great story!   You did miss one point in your conclusion though.....yours happened at low airspeed in climbing.  If that would have happened in cruise, I bet the outcome may not have ended the same way....especially with only single full speed trim.  At absolute bare minimum a speed reduction should be installed for slow trim during cruise.  Also, I really think that LESS than full speed would be annoying and perhaps in some cases compromise safety for some pilots.  So for me, dual speed is a big deal.  

    

Personally though, I think at 170+ kts that a full-speed nose up trim runaway to the stops would stand a good chance of bending something.  

    

And if someone were screwing around doing low passes at high speed for show and they got full speed nose down at 175kts and 100' they'd be toast by the tome they'd recognize the problem.  

    

   

    

At lower climbout speeds though, it's totally different, and it's nice to hear that you can fight the trim by arm strength.  

    

Tim  

    

   

    



 On Sep 26, 2010, at 7:45 AM, "Wayne Edgerton" <w.edgerton(at)verizon.net (w.edgerton(at)verizon.net)> wrote:  

   	  Quote: 	
		        

I've been reading the concern over runaway trim and thought I would share my experience with this. Back in, I think, 2007 when Ray Allen came out with relay II to replace relay I because of problems, we went in and changes out the relay.   

    

   

    

I was going to go up and test the trim with the new relay and someone at the hangar had never been up in a 10 and wanted to hop in the right seat. We took off and I was explaining how you used the trim for climb and then again when you level off. At about 300' I hit the trim up on my hat switch and I the trim servo went to full stop up in what seemed like two nanoseconds. It was so fast that even if I could have reached the CB it would have been way over with by then. I had to put a really large amount of pressure on the stick to hold it forward, in fact I ask my passenger to put his hand on the passenger stick to help me hold forward pressure just in case my harm gets tired.  

    

   

    

I was able to hold the stick forward but it took quite a bit of pressure but I was then wondering how the hell I was going to flair it in the landing that way. I hadn't really left the pattern so I just pulled down wind and told the passenger that it will be ok, under my breath saying I hope. Anyway as I proceeded downwind and as I pulled back on the power the pressure on the stick started to degrease. As I pulled the power back more the pressure continued to decrease. I obviously had to be very gentle and careful on landing to just let back a certain amount on the stick in landing but the landing went fine.  

    

   

    

I taxied back to the hangar and sat there wondering what the hell was that. I tested the trim and it worked fine. I decided I was going to go back up, crazy guy, and see if it would do that again and my passenger decided he would also try it again so if I needed help holding the stick. I went up  and waited a little longer before trying the trim but when I did boom here we go again, being from TX I had to yell yea hah ride um big boy :>} Anyway same drill on landing and when we landed we took out the RA relay II and put back in the relay I and went back up problem solved. I called Ray Allen a little less than happy and the first words out of their mouths was it wasn't our relay you wired it wrong. We wired it exactly the same way as we took out and put back in relay I and II. They sent me another relay and that one worked fine. For some reason the first one was ok as long as there was no pressure being exerted but with pressure on it it would go nuts.  

    

   

    

Anyway as an end to this story, as much as I didn't much care for the experience it did show me that if I did by accident have a run a way trim I could still control the plane. However whenever I fly I notice that I subconsciously always ride with my hand on the stick when the auto pilot is engaged.  

    

   

    

Wayne Edgerton  

    

   

    

 N602WT  

    

       

    

   

    

   

    

   

            

Time:          

01:38:30 PM PST US        

           

Subject:          

Re: performance   (pitch trim)        

           

From:          

"Bob Turner"   <bobturner(at)alum.rpi.edu (bobturner(at)alum.rpi.edu)>        

      

       

       I've put pullable CB's for the trim and autopilot right next to each other, just

       right of center in front of the pilot, easily reached by the right hand. I'll

       put a red box around them. My plan is that if the pitch goes nuts, I'll pull

       both breakers, then sort out the problem.

       

       --------

       Bob Turner

       RV-10 QB  

   	  Quote: 	
		    ===================================ref="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List===================================ums.matronics.com">http://forums.matronics.com===================================http://www.matronics.com/contribution">http://www.matronics.com/contribution=================================== 	


   	
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