Elevator Trim Tabs - wrong movement direction?

[Santiago3]

Hi everyone,

Im not sure if this has been mentioned before, or is it just me experiencing this.

Upon close inspection, I noticed that the elevator trim tabs on default (and some add-on) aircraft in FSX animates to the wrong direction (moves for a nose-down when you adjust for nose-up, and vice versa).

Correct me if I'm wrong: Trim tabs move to the same direction as the main elevators do - eg. if you trim for nose-up, the tabs shud move the same direction (up) as the elevator does if you pull the stick/yoke for nose up?

This isn't the case for me... instead, the trim tabs animate to the opposite direction of my controls (eg. if i trim nose-up, the animation does a 'nose-down' movement, and vice versa). There is an exception though, and that is the Aerosoft Beaver X add-on which animates correctly. The rest of my GA aircraft, be it default or add-on animates wrongly. But the planes does respond to the correct control, only the animation is the opposite way.

Am I the only one noticing this, or is it a known FSX "bug"? Just in case you haven't notice this already, try this - on the ground, switch to Spot or Locked SPot view, pan around to have a clear view of the trim tabs, and zoom in as close as you can. Make big adjustments of the trim, and watch the trim tabs animate.

Your thoughts are most welcome.

Santiago

[lnuss]

An elevator trim tab uses aerodynamic forces to move the elevator, thus if the trim tab goes down, it deflects air downward and is itself (taking the elevator with it) forced upward. So nose up trim would move the tab down, moving the elevator up which, of course, raises the nose.

On a stabilator (one piece horizontal tail -- well, almost one piece), there is an anti-servo tab, which moves as the elevator moves, and in the same direction, thus providing a resistance force which the pilot can feel. On SOME of these, the trim control will adjust the anti-servo tab almost as if it were a trim tab, but it doesn't stop the anti-servo tab from moving with the elevator, it only changes its range of travel.

Your description of what the elevator trim tabs do on your aircraft sounds correct, and your description of what you expected sounds like an anti-servo tab.

I know it's not intuitive, but that's true of a LOT of things in aviation.

You might also see this section of the flightsim Wiki: What actually gets moved when trimming an aircraft? for further description, and be sure to check out the Wikipedia references there, also. It's in the Miscellaneous section of the Flying Techniques and Real Aviation FAQ there.

[Santiago3]

Wow.. thanks a lot Inuss for clarrifying things up .. and what an embarrassment my post was ?! LOL !

You see, I've been flight simming for many years but din't pay much attention about trim tabs operate (yes, i do use them all the time and understand the effects in the sim)... but until you enlighten me on that, i had no idea it moves "inverted"

Now that's one big thing i learn

THanks!

Santiago

[n4gix]

You see, I've been flight simming for many years but din't pay much attention about trim tabs operate (yes, i do use them all the time and understand the effects in the sim)... but until you enlighten me on that, i had no idea it moves "inverted"

If your goal is to force the elevator "upwards" to trim the aircraft, then logically the trim tab would deflect "down..."

Force of air moving across the "downward" trim tab will apply force in an "upwards direction" thereby transferring that force to the elevator...

[InsyleM]

If your goal is to force the elevator "upwards" to trim the aircraft, then logically the trim tab would deflect "down..."

Force of air moving across the "downward" trim tab will apply force in an "upwards direction" thereby transferring that force to the elevator...

I noticed that on the default DC-3... Backwards trim tabs....
I wonder how/why such an easy item was in error. It would be
an easy fix in the modeling too, just flip the axison the part.
Did you also notice your carburator is set too lean at idle?
-Jonathan

[ladamson]

I noticed that on the default DC-3... Backwards trim tabs....
I wonder how/why such an easy item was in error. It would be
an easy fix in the modeling too, just flip the axison the part.
Did you also notice your carburator is set too lean at idle?
-Jonathan

I haven't checked the DC-3, but some older versions (was FS2002 or FS2004) had reversed trim tab animation on the Cessna 182.

L.Adamson

[John_c]

Have you noticed that the default Maule has the right aileron moving in the wrong direction. When rolling to the right, the right aileron moves down rather than up, as it should.

John

[InsyleM]

I haven't checked the DC-3, but some older versions (was FS2002 or FS2004) had reversed trim tab animation on the Cessna 182.

L.Adamson

I just noticed Ive posted in FSX. I havnt really played FSX due to financial
and hardware limitations. My observation of the reversed elevator trim tab
on the DC-3 was in FS2K4
-Jonathan