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  #1  
Old 06-08-2020, 06:27 AM
Crafting N112DR's Avatar
Crafting N112DR Crafting N112DR is offline
 
Join Date: Oct 2013
Location: Powell, OH
Posts: 300
Default Flutter of AST in Flight

I have been documenting my test flights extensively using a 360 camera mounted on the tail tie down. I have noticed that the the AST tends to flutter in flight. This it not notable whatsoever in the stick in flight. I have the older style AST trim with no bend in the rod. There is a very small amount of play when you hold the stabilator stationary on the ground and then flex the AST. I have looked at three other RV-12?s and they seam to have to same amount of static play. I made a 1 min video so you can all see what I?m talking about. Anyone have any insight on this?


Here is the Link


https://youtu.be/hG2BrVRO3eg
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David Rohrlick
PPSEL, A&P
N112DR (RV-12iS) (SOLD)
Airworthiness signed off by the FAA 1/23/2020
First Flight on 3/14/2020
Phase I Finished on 5/7/2020
Serial#12-0864
https://youtube.com/c/CraftingN112DR
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  #2  
Old 06-08-2020, 07:49 AM
moosepileit moosepileit is offline
 
Join Date: Dec 2010
Location: Louisville, KY
Posts: 747
Default

Looks like rather stable flight conditions. The trailing edge of the tab appears always in the "up" direction, zoomed in at .25 speed.
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  #3  
Old 06-08-2020, 08:45 AM
DGlaeser DGlaeser is offline
 
Join Date: May 2005
Location: Rochester Hills, MI
Posts: 913
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Looks like some oil canning of the skin, even on the area outside the aileron. Watching the TE, I don?t see any movement...
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Rochester Hills, MI
RV-7A - Eggenfellner H6, GRT Sport ES, EIS4000, 300XL, SL30, TT Gemini, PMA6000, AK950L, GT320,
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  #4  
Old 06-08-2020, 09:19 AM
Marc Bourget Marc Bourget is offline
 
Join Date: Apr 2009
Location: Stockton, California
Posts: 338
Default

I think I'd focus on calling it "vibration" rather than flutter.

Not being picky, but flutter, in airplane context, usually suggests divergent occillation (increasing in amplitude). This appears steady state.

In a gross sense, anything totally rigid to flight loads would probably be too heavy to get off the ground.
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  #5  
Old 06-08-2020, 09:20 AM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,234
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Comparing the outboard trailing edge of the AST to the trailing edge of the
stabilator, I can see the relative motion between the two surfaces, especially if
the play back speed is reduced to 25 percent. We need Van's opinion on this.
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  #6  
Old 06-08-2020, 10:16 AM
HansLab HansLab is offline
 
Join Date: Jan 2015
Location: Netherlands
Posts: 140
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Man!! I even can see the skin of the elevator vibrate - it looked like it's alive. Ho wonderful these pics are - where's the rest of the 360 movies?
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  #7  
Old 06-08-2020, 10:45 AM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,654
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It appears to me to be a vibration induced movement of the tab, and not unusual. One reason I say this is that the movement doesn't appear to have a constant / steady frequency.
Another reason is that the variation of the reflection on the outboard stabilator skin right beside the AST seems to mimic the reflection rhythm of the AST skin.
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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.

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  #8  
Old 06-08-2020, 12:04 PM
Crafting N112DR's Avatar
Crafting N112DR Crafting N112DR is offline
 
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Location: Powell, OH
Posts: 300
Default Vibration

Thank you all for your opinion, my main concern is safety of fight. This vibration could lead to wear of the AST components down the road. As Scott has said he thinks this is not unusual so I'm good with the knowledge that its safe. Has anyone else experienced this in flight?

Thanks
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David Rohrlick
PPSEL, A&P
N112DR (RV-12iS) (SOLD)
Airworthiness signed off by the FAA 1/23/2020
First Flight on 3/14/2020
Phase I Finished on 5/7/2020
Serial#12-0864
https://youtube.com/c/CraftingN112DR
VAF donation made for 2021
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  #9  
Old 06-08-2020, 12:19 PM
Dave12 Dave12 is offline
 
Join Date: Oct 2010
Location: Elkton, Md.
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Maybe Nigel, Axel or Mel could opine? Some of our bonafide test pilots.
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  #10  
Old 06-08-2020, 12:20 PM
RFSchaller RFSchaller is offline
 
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Location: Phoenix, AZ
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Checkout this YouTube video for some flutter video clips

https://nam03.safelinks.protection.o...amp;reserved=0
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