Rudder Trim in Start up tutorial

Having trouble with laternal control on the ground during take-off rolls?

The tutorial instructs rudder trim to the right. This deflects to trim tab to the right, pushing the rudder to the left, therefore yawing the nose left. This is pouring gas on the fire for virticle axis instability.

The P-51's Merlin rotates clock-wise which mean everything about it yaws the nose to the left via P-factor, Torque, and Gyro-scopic recession. Try trimming the rudder tab to the left 3 to 5 degrees.

S!

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Have you looked at the rudder when you do that?

Yes, I went to external view, saw the tab deflected to the right. Furthermore, during climbout, the inclonometer is unnessicerily deflectected more than a balls width to the left. Proper trimming prior to take off should indicate a centered ball.

Try trimming to the left and you'll see a marked improvement in stable flight charateristics.

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The entire rudder moves to the right when you trim right (since trim is still a WIP), I am not sure what you are looking at.

From what I see, the "TAB" moves right and the rudder responds correctly, making the the nose yaw to the left. Not good when everything about the propulsion system pulls the nose left all ready. I'm currently on a 4-day trip that finishes tomorrow. When I get home, I'll post a screenshot of the tab actually deflected from center-line within the rudder.

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Rudder trimmed 10 degrees right. Been this way for both beta releases.

It was already acknowledged that this is a visual bug , though the physical model is correct (cant find the post) - it will be corrected in a next beta.

Yes cichlidfan - trim-tabs always move the opposite direction to the wanted movement of the surface , so they drag the whole surface in the wanted position only by the airflow. (think of an rudder on the rudder )

You can test it in the A10 to understand the whole principle by switching to manual revision flight control (no hydraulic pressure ) in flight to see what the trim-tabs are doing.

When you do it in flight- be prepared for a roller-coaster ride and have enough free air under your belly!

edit:

found something official

The trim model was not yet finalized in the beta releases. Working correctly internally now and should be added in the next public release.

The trim tab has a "lift" effect (created by airflow over the curve created), so it pulls the control surface in the direction of its curve.

If the rudder Trim Tab was set n degrees to the right, for instance, it would pull the rudder left.

And in considreing that the P51 is currently in Beta, and until the acknowledged anomoly is fixed, it is best at the moment to not set trim and just ride the rudder

And in considreing that the P51 is currently in Beta, and until the acknowledged anomoly is fixed, it is best at the moment to not set trim and just ride the rudder

Wrong. The FM reacts to trim as it should (except on the ground).

Wolf Rider,

You can trim as you wish. It's only the visual model that is wrong.

It was already acknowledged that this is a visual bug , though the physical model is correct (cant find the post) - it will be corrected in a next beta.

Wolf Rider,

It's only the visual model that is wrong.

erm... I never said the visual (current Beta) model was correct

Wrong. The FM reacts to trim as it should (except on the ground).

Perhaps I was bit unclear, but the thread is about TAKE OFF, it would seem natural to assume the understanding would have been I was speaking with regard to a take off.

Also worth noting, although takeoff is normally performed with about 5 degrees of right rudder trim, the trim model is still WIP. At this point turning the trim wheels moves the actual control surface, so if you are adjusting rudder trim for takeoff, you are actually turning the rudder and the tail wheel and not just the rudder trim tab.

Trim becomes effective with adequate airflow, not before

Trim becomes effective with adequate airflow, not before

That was what the WIP was meant to relate to. It is fixed in the internal build so it'll probably be fixed in the next open beta as well.

Thanks for the heads up... that's good news indeed :thumbup:

I found that I was looking too closely. The trim tab is currently moving in the wrong direction. I just didn't notice that the whole rudder was moving with it because I was looking at a zoomed in view of only the tab.

I stand corrected and note that it's a visual bug.

So, when this is fixed, we should visually see the trim tab should move to the left for right rudder trim, and to the right for left rudder trim input.

Thnx

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I think that open beta will incorporate FFB, FFB trim, etc, etc.

:bounce:

:holiday: