In the product acceptance checklists, one of the steps is to run the Anti-Servo Trim tab to the stops and measure the distance from its trailing edge, to the trailing edge of the stabilator. The acceptance checklist says nominal distance 9/16", mine is >3". Going the other way, nominal distance is 3/8", I get 1". Does this sound correct?
Van's Air Force
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AST range of movement
- Thread starter GDS
- Start date
Per the PAP...
With full "NOSE UP" trim, move the stabilator to the full trailing edge up position and measure the tab position.
With full "NOSE DOWN" trim, move the stabilator to the full trailing edge down position and measure the tab position.
The Production Acceptance Procedures are specific.
Tony
With full "NOSE UP" trim, move the stabilator to the full trailing edge up position and measure the tab position.
With full "NOSE DOWN" trim, move the stabilator to the full trailing edge down position and measure the tab position.
The Production Acceptance Procedures are specific.
Tony
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Thank you Tony, I couldn't quote the procedure because the paperwork is at the hangar:
With full "NOSE UP" trim, move the stabilator to the full trailing edge up position and measure the tab position. Distance on our RV12 is 3 1/4"
With full "NOSE DOWN" trim, move the stabilator to the full trailing edge down position and measure the tab position. Distance on our RV12 is 1"
Are those distances reasonable?
With full "NOSE UP" trim, move the stabilator to the full trailing edge up position and measure the tab position. Distance on our RV12 is 3 1/4"
With full "NOSE DOWN" trim, move the stabilator to the full trailing edge down position and measure the tab position. Distance on our RV12 is 1"
Are those distances reasonable?
Gary,
Those distances do not seem right to me. The spec says "nominal" distance of 9/16" for the full up, and 3/8" for the full down. I would not accept 3 1/4" and 1" as meeting that criteria. Mine measured 1/2" and 1/4".
I would call Van's tech support on this one, from the hangar, so you can make measurements while on the phone with them. It could be an adjustment, let us know what you find out.
Tony
Those distances do not seem right to me. The spec says "nominal" distance of 9/16" for the full up, and 3/8" for the full down. I would not accept 3 1/4" and 1" as meeting that criteria. Mine measured 1/2" and 1/4".
I would call Van's tech support on this one, from the hangar, so you can make measurements while on the phone with them. It could be an adjustment, let us know what you find out.
Tony
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Geico266
Well Known Member
I agree with Tony, mine were exactly to the specs called out in the PAP without adjusting anything. In any event, I would double check the set up or call Vans Monday morning.
A couple of thoughts here,
1. Double check the PAP called out position of the rudder during this test. Is it neutral or full deflected?
2. Double check the length of the servo arm. I believe the dimensions are bolt hole center line to bolt hole center line, not over all length.
Good luck and keep us posted on what you find.
A couple of thoughts here,
1. Double check the PAP called out position of the rudder during this test. Is it neutral or full deflected?
2. Double check the length of the servo arm. I believe the dimensions are bolt hole center line to bolt hole center line, not over all length.
Good luck and keep us posted on what you find.
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I'll check next Wednesday when I get back to Big Bear.
I know the polarity is correct, the motor runs the right way.
I double checked the position of the stabilator when taking the measurement. I need to double check the length of the servo-arm.
Also, time for AST travel, stop to stop, is good at 26 seconds.
Another thing that has occurred to me is that the control horn for the stabilator is asymmetrical and I installed it upside down.
thanks for the good ideas,
GDS
I know the polarity is correct, the motor runs the right way.
I double checked the position of the stabilator when taking the measurement. I need to double check the length of the servo-arm.
Also, time for AST travel, stop to stop, is good at 26 seconds.
Another thing that has occurred to me is that the control horn for the stabilator is asymmetrical and I installed it upside down.
thanks for the good ideas,
GDS
MacPara
Well Known Member
Has this problem ever been solved? I am asking as I am seeing the exact same travel and measurements as GDS 3 years ago. I suspect that the servo is moving the wrong way.
When I run all the way nose down trim, my AST's trailing edge is all the way DOWN and all the way UP when I run full nose up trim. Is this correct? I can't find the answer in the PAP and my instructions are at the hangar ....
When I run all the way nose down trim, my AST's trailing edge is all the way DOWN and all the way UP when I run full nose up trim. Is this correct? I can't find the answer in the PAP and my instructions are at the hangar ....
Nose down trim should make the tab move up.
Nose up trim should make the tab move down.
I believe this check is also part of the PAP.
You could go back to the section of the KAI that has you making the connections to the servo motor and redo the steps that have you checking and confirming that the tab is moving in the correct direction.
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MacPara
Well Known Member
Hm, I think I still don't understand how the AST works aerodynamically but going the opposite way for the AST movement gets me within the PAP measurements.
I have no clue how I could mess the wiring up 3.5 years ago when I started the build and did the servo connections but I must have.
Either way, I'm planning to swap the pins 31/32 on the Fuselage sub-D connector which hooks up the servo motor wires to the black box. That's easier than changing the spade connectors on the thin motor wires.
Thanks for the help. This would have been a very short first flight with the trim all messed up!
I have no clue how I could mess the wiring up 3.5 years ago when I started the build and did the servo connections but I must have.
Either way, I'm planning to swap the pins 31/32 on the Fuselage sub-D connector which hooks up the servo motor wires to the black box. That's easier than changing the spade connectors on the thin motor wires.
Thanks for the help. This would have been a very short first flight with the trim all messed up!
The trim setting is very important for the first flight. At least one RV-12 has crashed on first flight after it leaped off the runway and stalled. Run the trim all of the way nose down, then back up only 1/4 of the way for the first takeoff. Until the test pilot determines where the takeoff trim setting should be, it is better to error on the side of nose down rather than nose up.
Joe Gores
Joe Gores
