Landing and rudder trim

[Wichid]

Has anyone else noticed that you tend to slide and crash after landing if you have rudder trim set?

 

It seems much safer to land with rudder trim set to neutral...

[cichlidfan]

Has anyone else noticed that you tend to slide and crash after landing if you have rudder trim set?

 

It seems much safer to land with rudder trim set to neutral...

 

I was nodding my head...before I finished reading the whole sentence!:D

 

EDIT: BTW, I don't see anything in the manual about rudder trim for landing.

Edited May 3, 2012 by cichlidfan

[IvanK]

I think this is a Beta issue. Since at present Trim means actual surface deflection rather than tab deflection. In the case of Rudder that means 5 units rudder trim at present means you have x degrees Rudder deflection. On landing with the stick aft of neutral means tailwheel steering is engaged. Since in the BETA Trim is surface deflection that means you have y amount of tailwheel steering as well so as soon as the tailwheel makes ground contact ... off you go.

 

If the Rudder trim was actual tab deflection this issue would/will go away. In the meantime land with Rudder trim trim neutral.

[Yo-Yo]

I think this is a Beta issue. Since at present Trim means actual surface deflection rather than tab deflection. In the case of Rudder that means 5 units rudder trim at present means you have x degrees Rudder deflection. On landing with the stick aft of neutral means tailwheel steering is engaged. Since in the BETA Trim is surface deflection that means you have y amount of tailwheel steering as well so as soon as the tailwheel makes ground contact ... off you go.

 

 

If the Rudder trim was actual tab deflection this issue would/will go away. In the meantime land with Rudder trim trim neutral.

 

How do you want the rudder to work differently? Are your rudder pedals of FFB type? :)

Any trimmer will work in the same way. Your pedals neutral point is a force neutral point for rudder and trim tab system so having non-zero trim you always have rudder and tail wheel deflected.

The only thing we can make for trimmer - is an eye-candy when at zero speed only trim tab deflects not rudder itself. But at 40-50 mph you will have the whole rudder deflected. It's an eye-candy but I am not sure you will like it running... :)

[IvanK]

If I am sitting on the ground with the stick back and aft of neutral and I wind in some rudder trim the only thing that will happen is the tab surface itself will move. The Rudder surface and or tailwheel steering will NOT react one bit.

 

All The Rudder trim input on take off is there for is to reduce pedal loads once airflow and the rudder itself become effective. Tailwheel deflection will ocurr with rudder surface deflection if tailwheel steering is engaged. (This is the situation I think we currently have in the beta since Trim deflection is actually moving the surface not the tab itself).

 

I have just confirmed this as well with a close friend and current Mustang pilot.

[WildBillKelsoe]

How do you want the rudder to work differently? Are your rudder pedals of FFB type? :)

Any trimmer will work in the same way. Your pedals neutral point is a force neutral point for rudder and trim tab system so having non-zero trim you always have rudder and tail wheel deflected.

The only thing we can make for trimmer - is an eye-candy when at zero speed only trim tab deflects not rudder itself. But at 40-50 mph you will have the whole rudder deflected. It's an eye-candy but I am not sure you will like it running... :)

 

hey yo-yo. could you point me to the thread for remarks from pre-purchasers of the sim? I want to throw my remarks for your work guys.

[Yo-Yo]

If I am sitting on the ground with the stick back and aft of neutral and I wind in some rudder trim the only thing that will happen is the tab surface itself will move. The Rudder surface and or tailwheel steering will NOT react one bit.

 

All The Rudder trim input on take off is there for is to reduce pedal loads once airflow and the rudder itself become effective. Tailwheel deflection will ocurr with rudder surface deflection if tailwheel steering is engaged. (This is the situation I think we currently have in the beta since Trim deflection is actually moving the surface not the tab itself).

 

I have just confirmed this as well with a close friend and current Mustang pilot.

 

we are talking about the same thing. But my point was that IN SIM we must have trimmers working as they work now EXCEPT the very low IAS condition. Very low means IAS less than 40-50 mph. And this is overall air speed at the empennage so even propwash at full power makes rudder and elevator stiff and they get the trim position.

 

Once again - in sim as we have non-feedback controls we must use trimmers to set controls to the trimmed position.

The only minor issue we have now is control surfaces deflection even if there is no dynamic prtessure at the empennage. But either in flight or during take-off run the trim will work as it works now.

This is our sim reality... :)

Edited May 3, 2012 by Yo-Yo

[Yo-Yo]

hey yo-yo. could you point me to the thread for remarks from pre-purchasers of the sim? I want to throw my remarks for your work guys.

 

What do you want to report about? Can't you find the proper thread?

[26-J39]

If I am sitting on the ground with the stick back and aft of neutral and I wind in some rudder trim the only thing that will happen is the tab surface itself will move. The Rudder surface and or tailwheel steering will NOT react one bit.

 

Hmm.. not true... At full rudder trim, the tab moves about 30 deg, rudder surface 15 & tail wheel 5 deg roughly. That's stationary on ground.

[Yo-Yo]

Hmm.. not true... At full rudder trim, the tab moves about 30 deg, rudder surface 15 & tail wheel 5 deg roughly. That's stationary on ground.

 

Hown it can be? The gear ratio is 5 from the rudder to the tail wheel. 30 deg of rudder means 6 degrees of tailwheel.

[flightace37]

I don't have any real problems landing with trim, but I also land at pretty low engine power and contact the runway on three points. It doesn't give too much kick over, and I'm able to correct it pretty easily using pedals. Landing has actually gotten to be easier than takeoff for the time being.

 

As far as trim implementation goes, I want to suggest something that ED may or may not have considered yet. What about using a force/counter-force implementation, where the physical controller's displacement from zero is the amount of force the pilot applies against the controls, instead of actual deflection of the stick. That way, the trim tabs can have their real-life physical effect.

 

You would obviously need a default base "spring" so that returning the physical stick to center actually returns the aircraft's flight stick to center for ground operations. With this implementation, deflection would be zero when no aerodynamic force is being applied to the flight controls with the user's physical control centered. As speed increases, the flight controls would respond by moving toward their trimmed position, all without the user having to move the physical stick. The simulated stick in the cockpit would move to the new aerodynamic center.

 

Tail wheels like on the P-51 have a tendency to center themselves, so those forces could be added to the effects of the rudder aerodynamic return. I imagine having the tail wheel in contact with the ground would tend to override the effect of the rudder, and so the aircraft would track relatively straight, which is what we expect.

 

It would probably be necessary to fade out the default spring as aerodynamic forces increase so that it doesn't affect flight characteristics. The user shouldn't have to trim out a non-existent spring while in flight. This can be done with an appropriate mathematical function.

 

This all of course only applies to aircraft modeled with physical or hydraulic controls. Fly-by-wire systems would still simply send stick position to the computer. The computer however, might have to deal with trim tab effects, if that's how trim is implemented on that particular aircraft.

 

Just trying to be helpful. I have not thought the entire thing through, so it may or may not actually work as intended.

[26-J39]

Hown it can be? The gear ratio is 5 from the rudder to the tail wheel. 30 deg of rudder means 6 degrees of tailwheel.

 

Dont take the numbers literally, it's a rough number in degrees..

 

What I mean to convey is that the rudder surface itself DOES move when trim is applied. :)

 

Edit: When stationary on the ground.

[IvanK]

Is this based on real world experience ? I am intrigued by this. How is the tab connected to the rudder surface ? Happy to be proven wrong btw just need to get this sorted in my head :)

 

This jpg from P51D/K erection manual doesn't show any interconnection between the Tab controls/surface and the rudder itself.

 

Edited May 3, 2012 by IvanK

[Wichid]

I was using the rudder trim to help with the cross wind landing. I think my other problem came from the fact that the torque dying pulled the plane in the same direction meant that it went into a slide a few seconds after landing.

[Smokin Hole]

What's the issue here? Trim so that you can fly hands and feet off (breifly) on final. Then forget it. Land three points in any wind. She won't bounce and will track nicely so long as you keep the stick in your gut.

[Yo-Yo]

I was using the rudder trim to help with the cross wind landing. I think my other problem came from the fact that the torque dying pulled the plane in the same direction meant that it went into a slide a few seconds after landing.

 

Then you'd better use rudder to counteract all these troubles and you will sure that your neutral position corresponds neutral tailwheel. I think that in RL using trim to have sideslip on final is not a good idea.

[Pyroflash]

You should only be using trim to prep for takeoff and for cruise flight. Using trim on landing is not necessary or safe because of the possibility of a go-around (significant power changes equate to changes in required control input).

[Yo-Yo]

Is this based on real world experience ? I am intrigued by this. How is the tab connected to the rudder surface ? Happy to be proven wrong btw just need to get this sorted in my head :)

 

This jpg from P51D/K erection manual doesn't show any interconnection between the Tab controls/surface and the rudder itself.

 

There is a linkage... but AERODYNAMIC linkage. :) If you have dynamic pressure at the surface it will be balanced at the deflection angle that is proportional to the trim tab deflection.

[Wichid]

Yep with neutral rudder landing is going quite nicely. A minor thing I just noticed - zooming in the F2 view, the external lights go out on the aircraft. Zoom out and you can see them again...

[IvanK]

There is a linkage... but AERODYNAMIC linkage. :) If you have dynamic pressure at the surface it will be balanced at the deflection angle that is proportional to the trim tab deflection.

 

Yes Yo YO I understand the aerodynamic linkage and agree with you. But not on the ground with zero forward speed with the tailwheel steering engaged as J6-239 indicates occurs.

[Yo-Yo]

Yes Yo YO I understand the aerodynamic linkage and agree with you. But not on the ground with zero forward speed with the tailwheel steering engaged as J6-239 indicates occurs.

 

Agreed.

[Snoopy]

Yep with neutral rudder landing is going quite nicely. A minor thing I just noticed - zooming in the F2 view, the external lights go out on the aircraft. Zoom out and you can see them again...

 

Lights are a known issue...

[kyletiernan]

I was having this problem until i did the landing training. When I land at 90-100 it sets down quite nice. Trying to taxi is another story :P

[mnrty]

i think i have crashed more planes during taxi than on takeoff and landing combined! I just dont get the hang of it.

[Pyroflash]

i think i have crashed more planes during taxi than on takeoff and landing combined! I just dont get the hang of it.

 

 

Yeah, this plane is screwy I think. The aircraft I fly IRL doesn't have a steerable nose either, and that thing is more of less a breeze to taxi around. I don't know, maybe it has something to do with the tail wheel, but when I try to apply the same practices of light taps on the brakes to keep straight, it just spins out of control, or failing that, doesn't do anything at all.

 

Note: this is probably me not doing something right, and I do notice that there is a significant difference between an Sr-20 and a P-51D.