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  #1  
Old 12-05-2018, 07:59 AM
romanov's Avatar
romanov romanov is offline
 
Join Date: May 2018
Location: Israel
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Question Question: maximum trimmer angle move

Hi Guys,

I didn't find any info in the specs so will ask you
expirienced fellows: is that trimmer move looks
good to you?

Does anybody has an info about
the angle the trimmer should go?



Thanks in advance
Roman
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  #2  
Old 12-05-2018, 11:45 AM
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romanov romanov is offline
 
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Measured the angle of the trimmer:

35 degrees down
10 degrees up

does it make sense to have such a difference?
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  #3  
Old 12-05-2018, 11:52 AM
rocketman1988 rocketman1988 is offline
 
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Default yes

As the limited "up" throw actually will trim the elevator "down" yielding Aircraft Nose Down.

The increased "down" throw, trims the elevator "up" yielding Aircraft Nose Up.

You will need FAR more Aircraft Nose Up trim than down, so yes, it does make sense...
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  #4  
Old 12-05-2018, 11:57 AM
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romanov romanov is offline
 
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Quote:
Originally Posted by rocketman1988 View Post
As the limited "up" throw actually will trim the elevator "down" yielding Aircraft Nose Down.

The increased "down" throw, trims the elevator "up" yielding Aircraft Nose Up.

You will need FAR more Aircraft Nose Up trim than down, so yes, it does make sense...

As far as I can see now the diff between up and down in elevators
is 5 degrees, down is about 25 and up is 30 , so given that all,
it still leaves me with the question: why in the trimmer move the
diff is much more dramatic?
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Old 12-05-2018, 12:30 PM
Nova RV Nova RV is offline
 
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Here is your answer from Vans maximum 13/35 up/down minimum 11/32 up/down:

https://www.vansaircraft.com/pdf/let...ons_Letter.pdf
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  #6  
Old 12-05-2018, 12:32 PM
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romanov romanov is offline
 
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Quote:
Originally Posted by Nova RV View Post
Here is your answer from Vans maximum 13/35 up/down minimum 11/32 up/down:

https://www.vansaircraft.com/pdf/let...ons_Letter.pdf

Thanks a lot. Where did you find that one?
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Old 12-05-2018, 12:40 PM
Nova RV Nova RV is offline
 
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It's on the Vans website under support for the 14.

Remember too that up refers to the direction of the trim tab, not the resulting trim direction of the elevator. Up trim tab = down elevator movement in flight. So you want 13 degrees up trim tab max = max down elevator trim and 35 degrees down trim tab max = max up elevator trim.

Shoot for the max values especially on the trim tab down movement as you need up elevator trim quite noticeably with flaps and to flare for landing.
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  #8  
Old 12-05-2018, 02:37 PM
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romanov romanov is offline
 
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Quote:
Originally Posted by Nova RV View Post
It's on the Vans website under support for the 14.

Remember too that up refers to the direction of the trim tab, not the resulting trim direction of the elevator. Up trim tab = down elevator movement in flight. So you want 13 degrees up trim tab max = max down elevator trim and 35 degrees down trim tab max = max up elevator trim.

Shoot for the max values especially on the trim tab down movement as you need up elevator trim quite noticeably with flaps and to flare for landing.
Yeah, I do understand that, but yet the elevators angle
difference is not very big, is it cause eventually it is
achieved by very small angle of elevator?
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Old 12-06-2018, 05:26 AM
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rzbill rzbill is offline
 
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Think about the flight regimes in play when using the trim tab and you will have your answers. How fast are you going when nose up trim is needed? Is there a nose down moment created by a configuration change? When do you need nose down trim? How fast are you going at that time? Do you need a LOT of elevator movement for that condition?
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  #10  
Old 12-06-2018, 09:46 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by romanov View Post
Yeah, I do understand that, but yet the elevators angle
difference is not very big, is it cause eventually it is
achieved by very small angle of elevator?
There is no direct connection between how many degrees of travel the elev. the elevators have up and down from neutral, and how much travel the trim tabs have up and down from neutral.

The elevators travel range is based on how much travel the pilot needs for all flight conditions, to control the aircraft.
Example - enough nose down elevator for stall recovery, etc.

The trim tab travel is based on how much travel is required to attain hands off trim in any normal flight condition.
Example - pitch trim will never be used to recover from a stall so the trim tab doesn't need to have enough trimming authority to induce full down elevator.

A general rough guide line on all of the RV's (except the 10 and the 12), the trim system should be adjusted so that the trim tab will proved about twice as much nose up trim (tab travel down) as it does nose down trim.

If the parts supplied with the RV-14 kit are installed per the plans, this is approx what the travel ratio will be, and in flight the pitch trim will provide sufficient trim authority for all modes of flight.
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