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  #1  
Old 02-16-2007, 06:30 PM
Davepar's Avatar
Davepar Davepar is offline
 
Join Date: Jan 2005
Location: Seattle, WA
Posts: 1,166
Default Electric elevator trim direction

I know I just read this recently, but I can't find it. I want to make sure I've got the elevator trim going the right direction.

The up button should cause the trim tab to go up. Right?

Dave
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www.dualrudder.com/rv7 - building blog
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Last edited by Davepar : 02-17-2007 at 08:37 AM.
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  #2  
Old 02-16-2007, 06:38 PM
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Mel Mel is offline
 
Join Date: Mar 2005
Location: Dallas area
Posts: 10,762
Default

I don't understand the "up bottom". The tab must go up to trim the nose down. Remember the tab pushes the elevator in the opposite direction from the tab. Tab-up, nose-down. Tab-down, nose-up. You can have the switch whatever way you want it as long as it is marked properly. The switch should be marked with respect to the direction the nose will go.
Confused?
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  #3  
Old 02-17-2007, 05:51 AM
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Scott Will Scott Will is offline
 
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Location: ATL
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Dave... common mistake. On my coolie hat switch on the stick, when you push the switch down (towards the pilot, you want the plane to nose up) then the trim tab moves DOWN (towards the floor). It's reverse of what you would think. I know because I just took the ATP written and they had a question about this.

from http://www.aviation-history.com/theory/flt_ctl.htm
Assume that back pressure is required on the control wheel to maintain level flight and that we wish to adjust the elevator trim tab to relieve this pressure. Since we are holding back pressure, the elevator will be in the "up" position. The trim tab must then be adjusted downward so that the airflow striking the tab will hold the elevators in the desired position. Conversely, if forward pressure is being held, the elevators will be in the down position, so the tab must be moved upward to relieve this pressure. In this example, we are talking about the tab itself and not the cockpit control.
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  #4  
Old 02-17-2007, 08:38 AM
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Davepar Davepar is offline
 
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Location: Seattle, WA
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That'll teach me to post late at night. "Bottom" was supposed to be "button." Thanks guys. From your descriptions I have it hooked up right.

Dave
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www.dualrudder.com/rv7 - building blog
RunwayFinder.com - airport info, online charts, live METARs, TFRs, etc.
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