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  #11  
Old 06-10-2010, 08:06 PM
midwest rv-10's Avatar
midwest rv-10 midwest rv-10 is offline
 
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Location: Pleasant Prairie,Wisconsin
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Default RV-10 trim forces

The trim forces are significant and increase with speed. Go to my RV-10.com and read Tim's write up on the trim forces and the Safety trim system and the installation process. It should answer all your questions.

Don Orrick
N410JA
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  #12  
Old 06-10-2010, 09:58 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by midwest rv-10 View Post
The trim forces are significant and increase with speed. Go to my RV-10.com and read Tim's write up on the trim forces and the Safety trim system and the installation process. It should answer all your questions.

Don Orrick
N410JA
Don hit it right on. The trim force produced by a trim tab (or tabs) is directly proportional to the aircraft speed. If the stick force because of a trim failure feels too high for your comfort, pull back on the throttle and reduce speed. A trim force that feels very heavy at 180 kts may seem like very little at 100 kts.
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  #13  
Old 06-10-2010, 10:51 PM
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RV10inOz RV10inOz is offline
 
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Vic

I see your point.....however the failure of a solid state bit of gear is far less than the little button failing.

For the few hundred dollars its a no brainer.

Sure you can pull a breaker, but if the trim starts running away you will be busy keeping control of the plane let alone reaching for the breaker etc.

The safety trim controller only allows 3 seconds woth of trim travel at any one application of the button. Even if you realise the button has stuck and trim is running away, it will only go so far and you have time to use the reversing function, then you can continue using the REV function to trim forward and reverse until you get on the ground and can fix the problem.

Best value device I can think of for trim control.

DB
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  #14  
Old 06-11-2010, 01:26 AM
paul330 paul330 is offline
 
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If you have a nose up runaway and you increase speed, then you are plain dumb! As you reduce speed, the aircraft will come more in trim.

If you have a nose down runaway at high speed, then you have a problem when reducing for landing. I am not fully aware of the certification requirements for light aircraft, but I would have thought that it would be mandatory that the aircraft would remain controllable even if it required a bit of grunting. In any case, keep the speed up till required for landing and test controllability at altitude. Then if necessary, increase landing speeds.
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  #15  
Old 06-11-2010, 08:03 AM
aerhed aerhed is offline
 
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"The trim forces are significant and increase with speed. " Of course. That's still not a quantitative answer. I guess what I'd like to know is... Can an out of trim 10 be flown by someone with normal arm strength? As far as being too busy to pull a breaker, I don't buy it. You're just pushing or pulling & It's not hideen behind your back like John Denver' fuel selector. BTW, remember that an anti-trimmed surface has more authority than a trimmed surface. I read Tim's writeup, still doesn't really answer the question, he just says its "scary" or something.
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  #16  
Old 06-11-2010, 10:42 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by aerhed View Post
"The trim forces are significant and increase with speed. " Of course. That's still not a quantitative answer. I guess what I'd like to know is... Can an out of trim 10 be flown by someone with normal arm strength?
I think it is difficult to answer with the answer you want.

The forces that need to be countered are dependent on airspeed and how far out of trim the pitch trim is. The ease in producing the countering force is dependent on the strength of the person holding the stick. So it is not whether it can or can't.... it depends on a number of factors. Can it be controled at full deflection up to VNE. Probably not and probably no airplane can, so to answer your question it would require more specific information.
The control system is designed for a maximum amount of force that a person would likely be capable of inducing at the stick so the limiting factor will be the pilots strength.
I am pretty sure the RV-10 was tested to be controllable at both extremes of trim deflection but obviously that is at a much reduced airspeed for the reason I mentioned previously. I have not ever done any testing on a 10 my self (I have on other models) so I can not give specifics.

Sounds like a good thing for a 10 owner to add to their phase one test program. This could be done very safely if started at low airspeeds and slowly worked up to more and more trim tab deflection and speed.

Personally, this is one flight qualities item that I wouldn't take anyone else's word for.

Practice it in your airplane. This practice coupled with a practiced procedure for quickly disabling the electric pitch trim if need (having this should be a given) should keep RV-10 pilots out of trouble.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")

Last edited by rvbuilder2002 : 06-11-2010 at 10:45 AM.
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  #17  
Old 06-11-2010, 02:17 PM
aerhed aerhed is offline
 
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"Sounds like a good thing for a 10 owner to add to their phase one test program. This could be done very safely if started at low airspeeds and slowly worked up to more and more trim tab deflection and speed."
That's a dandy idea. I can always mod the trim later however I feel appropriate, based on real testing. Not that big a deal to do really. Thanks.
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  #18  
Old 06-13-2010, 05:29 AM
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RV10inOz RV10inOz is offline
 
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An RV10 taking off with a lot of nose uptrim is a very nasty beast......yes you can fly it, but it takes two hands on the stick and you have to ease off the power
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  #19  
Old 06-13-2010, 11:38 AM
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Vertical Power VP-200 has some nice trim safety features built in, as well. Similar to Safety Trim.
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  #20  
Old 06-14-2010, 07:13 PM
AaronG AaronG is offline
 
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Location: Hartford, CT
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I happen to be phase 1 flight testing my RV-10, so I tried some trim scenarios this evening. I don't have the wheel fairings on, so it might be slightly different when complete. What I learned:

1) If trim runs away nose up, let the speed bleed off, and it becomes manageable at about 110 kts with power to hold altitude. Let speed drop further and lower the flaps, and you can fly hands off around 75 knots. A slow trip home, but the landing should be uneventful.

2) If trim runs away nose down ... here I got surprised. I started at 110 kts, and the stick required 1 very strong hand. I increased power to increase speed, figuring it would trim out. Instead, stick forces increased beyond my ability to hold, and the plane started into a dive. Fortunately I was at altitude and able to trim the plane out ... definitely would have been interesting if I was unable to trim the plane out. I then repeated the experiment, but slowed the plane down from 110 kts. In this case, the stick forces got marginally lighter, and I could hold with my hands (strong force still required at 80 kts). Flaps also surprisingly didn't seem to make a difference at 80 kts, so I would put them down for the landing. This would clearly be a much more difficult landing than nose up trim, but it could be accomplished.

So bottom line for me, if I have runaway trim in either direction, slow the plane down below 100 kts, and fly to the nearest airport for a
flaps down landing.

Aaron
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