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Old 01-20-2021, 11:04 AM
SeattleAviator SeattleAviator is offline
Join Date: Nov 2020
Location: Seattle, WA
Posts: 18
Default Control Surface Clearance Requirements

I am doing a Pre-buy inspection of an RV-9a and note that some control surfaces (aileron, rudder, elevator) have very little clearance between them and surrounding structure. None of these controls are touching the surrounding structure but wafer thin margins. What is the clearance specification between 1)elevator and horizontal stabilizer at the counterweight end of the elevator, 2) rudder and vertical stabilizer at the top of the rudder, 3) outboard aileron and wing end cap? A jam could spoil my whole day! Also is there an easy way to adjust these clearances.

Thanks for your help.
Analog Man Living in a Digital World
Donation December 2020
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Old 01-20-2021, 04:09 PM
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bruceh bruceh is offline
Join Date: Mar 2008
Location: Ramona, CA
Posts: 2,423

Drawing 9 has the information for the wing. 1/4" gap nominal between wing tip and aileron. 3/16" nominal gap between aileron and flap.
Bruce Hill
RV-9A N5771H flown over 800 hours!
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Old 01-21-2021, 08:52 AM
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Steve Melton Steve Melton is offline
Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 3,097

if the control clearances are wafer thin be sure not to fly in any icing conditions or have bird a strike in the wrong place. this could be a show stopper for the sale unless it can be corrected. the thing more important than the engine is aircraft control.
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 900+ for all

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Last edited by Steve Melton : 01-21-2021 at 09:03 AM.
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Old 01-21-2021, 10:41 AM
Ralph Inkster Ralph Inkster is offline
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 1,248

Look closely at the flap and aileron hinges and see where the spacer washers have been placed in the hinge bolts, look for possibly redistributing the washers to get the required spacing. If you have to move the aileron outboard, you may need to sand the inboard edge of the wingtip to get the required spacing there.
For the elevators & rudder, you would have to remove those surfaces to adjust the hinge rod end bearings to gain the spacing you require. Refer to the plans for the suggested initial bearing distances and adjust ALL bearings to get required clearances and free movement.
built a few RVs, rebuilt a few more, hot rodded more, & maintained/updated a big bunch more
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Old 01-21-2021, 11:00 AM
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Mel Mel is offline
Join Date: Mar 2005
Location: Dallas area
Posts: 10,971

If the aircraft is not yet painted, that can also be a factor. Paint will narrow the gap by twice the thickness of the paint.
Mel Asberry, DAR since the last century. Over 1,000 certifications accomplished.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
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RV-6 Flying since 1993 (sold)
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