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setting up trim for takeoff 1st attempt issue

amekler

Well Known Member
Patron
I'm not sure my trim is correctly set up. I followed the procedure in the setup for full up full down and takeoff
it said calibration accepted but I see no markings on the trim indicator.
I'm also confused when you engage nose up which way should the tab move?
any help pictures appreciated.
Thanks,
Alan
N603NH RV-12 almost done
 
Believe it or not, about 1/2 of all airplanes I inspect have the pitch trim set up backwards.

Easy way to remember is that the tab "flies" the elevator/stabilator, not the airplane. If the tab is down, it forces the elevator/stabilator up. And vice/versa.
 
Mine was wired backwards when I became the owner... the plane had been that way for 11 years. I couldn't stand it... swapped the wires at the servo and life is much better now. :)
 
Easy way to remember is that the tab "flies" the elevator/stabilator, not the airplane. If the tab is down, it forces the elevator/stabilator up. And vice/versa.

Or in another way to look at it... the tab (regardless of whether it is on a traditional elevator or a stabilator) should always move in the opposite direction of the trimming function.

Trim switch activated for nose up - the tab should move down (and visa versa)
 
Flown with the trim reversed for 11 YEARS?!! Wow

Not necessarily unusual depending on the configuration of the pitch trim switch.

In instances where the switch is panel mounted, it could be either way depending on a persons preference / logical reasoning....
Should you push the top of the switch for nose down trim (I.E., rolling the switch fwd. akin to turning a trim wheel fwd., or push the bottom of the switch for going lower?
Just another of the never ending debates :rolleyes:

If the switch is on the stick, there should be no debate.
 
Two white wires that run the length of the airplane, which are also polarized; what can go wrong? :)
 
Van's manual trim...... turn it one way, if the plane doesn't do what you want, turn it the other way.......:D
 
Van's manual trim...... turn it one way, if the plane doesn't do what you want, turn it the other way.......:D

The way I remembered the manual trim on my -6 was...Screw the nose down, Unscrew the nose up.
 
Ok, I apologize for my snarky remark! I've not seen an aircraft with a trim switch on the dash, so it didn't seem possible you could fly a stick with the trim button running backwards... my mistake.

And a great question for the OP to ask. It was the only thing on my Certificate inspection that the DAR was really serious about. Guess it must happen often.

Fly Good
 
I'm not sure my trim is correctly set up. I followed the procedure in the setup for full up full down and takeoff
it said calibration accepted but I see no markings on the trim indicator.
I'm also confused when you engage nose up which way should the tab move?
any help pictures appreciated.
Thanks,
Alan
N603NH RV-12 almost done
To answer your original question, during setup you measure 2 inches up if I remember right. And that is your takeoff trim line. There is a step for it in the production acceptable process
 
Expanded Scale for Trim Indicator

I have set up my trim indicator as an expanded scale. Instead of showing the entire range of trim servo, I have set the end points to show only the portion of the trim corresponding to the flight envelope. End points on the scale are slightly greater than is experienced in flight. This allows a more meaningful and intuitive view of the usable window of trim movement.

Why show movement of trim that is not ever going to be used in flight? This is similar reasoning as used on an analog Volt Meter where the user selects the appropriate scale so readings are more accurate and easier to interpret. Why measure 5 volts on a 500 volt scale?

I recently had my pitot tube break in flight causing very erratic airspeed readings that were meaningless. When I slowed for landing, I set the trim to 1/8” from top of scale and I knew airspeed would be ~63 mph (55 knots) hands-off at idle power setting.

The photo below shows the Takeoff, Cruise, and Landing positions for trim. Because the scale is expanded, the motion of the indicator is more sensitive and allows more accurate positioning especially for takeoff.
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So I'm still trying to figure this out
here are 2 photos
one with the stick full forward and trim all the way down and the other with the stick full back and the trim all the way up
Alan
 

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I don’t know anything about the RV12 trim system. If however it’s conventional in the first pic the trim is full nose up. In the second pic the trim is nose down.
 
I don’t know anything about the RV12 trim system. If however it’s conventional in the first pic the trim is full nose up. In the second pic the trim is nose down.

The RV-12 has a stabilator with an anti-servo tab. Being familiar with the motion of an AST in contrast to a typical elevator and trim tab is important to answering the question, especially based on photos. An AST moves consistently in the same direction throughout the travel of the stab in order to dampen control surface forces. Trim makes a relative change. Unless you really have calibrated eyeballs, it's hard to determine this with photos of the two extreme stick positions.

The AST is moving in the correct direction. It would be hard to build the 12 the wrong way with respect to the AST. Need to see the relative movement of the AST with the stick in a constant position and trim input is given to determine if trim direction is correct.
 
problem solved
I took a look at an RV-12 LSA with the stick neutral up trim causes the tab to move down and vice versa. Mine is backwards and I switched pins 4 and 5 and now it behaves correctly.
Alan
 
Funny story: I once got some instruction in a Yak-52 from Sergei Boriak, world champion aerobatic pilot. After all that experience he was still using his hands to mimic the trim tabs to figure out which way they should be bent.
 
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