Why doesn't elevator trim wheel move in real time?

[Mango]

My joystick throttle axis is mapped to the P51's elevator trim wheel and it generally works correctly. However, when I move the physical wheel, the virtual trim wheel moves at a constant speed and thus lags behind my input.

 

Why doesn't the trim wheel move at the same speed as my control inputs? Imagine if the stick and rudder controls behaved the same, we would never be able to fly. :huh: As it is, I have to make several attempts to set the trim as I want it.

[PeterP]

Here is the punchline: The stick and rudders behave the same ! But you hardly notice it in a light aircraft like the P-51D.

 

All control surfaces in DCS simulate a mechanical friction that is representing the time you will need to move it for a 'average' human.

 

One example are the rudders in the Ka-50 - you are not able to move them from left to right in a fraction of a second. The mechanical hinges and hydraulics are taken into account.

 

And now about the trim-wheels: The real one are connected to pulleys that makes it impossible to move them as quick as your input device can without braking your fingers .

 

It's a sacrifice to have a AdvancedFlightModel instead putting your inputs 1:1 into the sim.

If this wouldn't be the case - you would be able to do with the plane what would never happen in RL.

 

One solution would be to add a great friction and/or a gears transmission to your Trim input , so you also wouldn't be able to move it all the way within a second.

And that's a very good thing in DCS - I only can shook my head when I see a heavy plane in X-plane (for instance) that is able to move the control-surfaces within a second from one max to the other - and the developers claim that they nailed the flight-model down as good as it can be .

 

 

Have a look how I modified my rudders to not 'over-react' :

http://forums.eagle.ru/showthread.php?p=1745115#post1745115

Edited May 10, 2013 by PeterP

[Merlin-27]

Here is the punchline: The stick and rudders behave the same ! But you hardly notice it in the a light aircraft like P-51D.

 

All control surfaces in DCS simulate a mechanical friction that is representing the time you will need to move it for a 'average' human.

 

One example are the rudders in the Ka-50 - you are not able to move them from left to right in a fraction of a second. The mechanical hinges and hydraulics are taken into account.

 

And now about the trim-wheels: The real one are connected to pulleys that makes it impossible to move them as quick as your input device can without braking your fingers .

 

It's a sacrifice to have a AdvancedFlightModel instead putting your inputs 1:1 into the sim.

If this wouldn't be the case - you would be able to do with the plane what would never happen in RL.

 

One solution would be to add a great friction and/or a gears transmission to your Trim input , so you also wouldn't be able to move it all the way within a second.

And that's a very good thing in DCS - I only can shook my head when I see a heavy plane in X-plane (for instance) that is able to move the control-surfaces within a second from one max to the other - and the developers claim that they nailed the flight-model down as good as it can be .

 

 

Have a look how I modified my rudders to not 'over-react' :

http://forums.eagle.ru/showthread.php?p=1745115#post1745115

 

Yup, what he said. :D It's simulating the controls.

[Mango]

Thanks, guys. That's both interesting and nice to know that my controllers are set up properly.

 

I've never notices this before in the Black Shark pedals, but my pedals are heavier and slower than the throttle wheel so makes sense.

[PeterP]

Well , I'm not 100% sure if my answer on the trim wheels is right- only at 98%.. , but all my engineering skills tells me that it needs a lot of power to move a trim-tab that is in such a distance , and hinged on another moving surface, on such a small space mechanical - so if you don't have the needed throw available to do it directly, you use this small space to translate your movement by a transition that adds a lot of friction.

 

So let's have a close look at his thread where I posted exactly this question:

What would YOU ask a real P-51 Pilot?

And let it maybe answered by someone who uses it by a living/passion.

Edited May 10, 2013 by PeterP

[sobek]

The movement speed of the trim controls was saturated during the beta to better mimick real behaviour. The trim wheels all have a gear reduction built in, so you have to turn them a lot for the needle to move just a bit. Since this makes it impossible to do fast changes without attaching an electric screwdriver to it, this measure was taken to keep the trim tabs in sim from being moved unrealistically fast. Anyone who has ever flown a simulated plane that does not have this (plane makers for X-Plane are prone to not do this) will appreciate it, else the plane would react extremely jumpy to trim inputs.

Edited May 10, 2013 by sobek

[Bucic]

(plane makers for X-Plane are prone to not do this) .

Even official XP testers are ignorant when it comes to the subject. Mention it to eagerly and you'll be named troll, like it ended for me :D

http://forums.x-plane.org/index.php?showtopic=46060&view=&hl=&fromsearch=1

XP aside, control forces modeling is an important aspect of simulation and knowing the details allows for better appreciation of a machine in-sim handling.

Edited May 15, 2013 by Bucic

[sobek]

XP aside, control forces modeling is an important aspect of simulation and knowing the details allows for better appreciation of a machine in-sim handling.

 

That's why Yo-Yo deemed it so important to have this. When they first introduced axes for trim, the plane would go complete bonkers with every small change you made because the actuation happened way too fast.

[Ali Fish]

Even official XP testers are ignorant when it comes to the subject. Mention it to eagerly and you'll be named troll, like it ended for me :D

http://forums.x-plane.org/index.php?showtopic=46060&view=&hl=&fromsearch=1

XP aside, control forces modeling is an important aspect of simulation and knowing the details allows for better appreciation of a machine in-sim handling.

 

painfull to read the responses. first and last time i have anything to do with that pretend sim thats apparently ok because they dont have enough money to do realism.

 

and also very bad because you, Bucic doesnt work for them with your expertise. thats a bit on the laughhable side for responses.

Edited May 15, 2013 by Ali Fish

[sobek]

Guys, this is not an avenue to bash other sims, please keep that in mind.

[Bucic]

That's why Yo-Yo deemed it so important to have this. When they first introduced axes for trim, the plane would go complete bonkers with every small change you made because the actuation happened way too fast.

Please pardon my mistake. I recalled the handling of some F-4 Phantom and changed my mind as to control forces modeling being important. It's freaking crucial! :D That thing flew like a RC model! Mango, please consider this. A top notch flight model X-Plane features didn't assure even remotely realistic handling of the machine because control forcesrelated modeling has been neglected/omitted. This is how important it is for realism to include all the delays there are. With your example a trim system that would operate without delay could even be used for cheating.

 

* by 'control forces modeling' I mean all aspects of control system/surfaces limitations - forces, resultant delays, damping, limited control surface actuators displacement speed etc.

 

 

I know I derailed the topic a bit but I have the following for my defence:

1. The xplane forums topic I linked above contains quite some explanations regarding the subject.

2. A bonus, courtesy of Rise of Flight blokes About "wrong elevator position" and "pitch sensitive"

And another one A2A BDG Battle of Britain "Wings of Victory" Patch 2.10 FM Code Enhancement

Edited May 15, 2013 by Bucic

[Ali Fish]

apologies, more referring to them o`er there with their responses as such to a knowledgable ED forum goer.

[ZaltysZ]

A top notch flight model X-Plane features didn't assure even remotely realistic handling of the machine because control forcesrelated modeling has been neglected/omitted.

 

You need to keep in mind that XP is a civil aviation sim with possibility to throw some military machines in, but it doesn't even remotely make it close to combat sim. Now, you can take a liner jet and abuse it to extent of imitating RC plane, but most fans of XP won't really get you, because they don't normally even approach RL control limits (you know, imaginary passengers love smooth ride and so on). Different use case, different priorities, different sandboxes to play in.

[ARM505]

Does anybody remember the IL2 'Shock, horror, using Trim on a Slider is cheating because you can trim instantly' discussions?

[msalama]

Does anybody remember the IL2 'Shock, horror, using Trim on a Slider is cheating because you can trim instantly' discussions?

Unfortunately yes. :chair: And then there was the Focke-Wulf bar brouhaha. And how this/that/the other was under- or overmodelled, and Oleg a government-funded communist childeater. And so on and on ad nauseum...

 

Yah, the bad old Ubizoo. That place really lived up to its name :D

[Echo38]

By the mocking tone, I presume that you feel that there isn't a problem with being able to go from neutral trim to full trim in a tenth of a second. Having flown several aircraft in the real world, I assure you that it is physically impossible to do so. It takes a couple of seconds to fully cycle the trim wheel--it cannot be done in the time it takes to blink, as it can in sim-games which do not make a decent effort to portray trim as accurately as possible with standard simming hardware. So, feelings and flames need not come into it--if a flight simulator lets you go from full negative trim to full positive trim in a quarter second, then it is incorrect (and the margin of error is very large--several hundreds of percent).

Edited May 20, 2013 by Echo38

[Bucic]

By the mocking tone, I presume that you feel that there isn't a problem with being able to go from neutral trim to full trim in a tenth of a second. Having flown several aircraft in the real world, I assure you that it is physically impossible to do so. It takes a couple of seconds to fully cycle the trim wheel--it cannot be done in the time it takes to blink, as it can in sim-games which do not make a decent effort to portray trim as accurately as possible with standard simming hardware. So, feelings and flames need not come into it--if a flight simulator lets you go from full negative trim to full positive trim in a quarter second, then it is incorrect (and the margin of error is very large--several hundreds of percent).

Yep. Same applies to any of the controls and the subject of a sim / type of A/C does not matter. The delays change, they are never zero. From my experience even in Extra 300 at low speed the controls movement limitations were not negligible. Even when I felt the forces as close to zero (the airspeed was low and Extra 300 has huge control stick arm and movement range) yanking the stick from fully right to fully left took some time. In an extreme case scenario even when you imitate the movement with your bare arms it will still take some time.

 

As for the trim. In probably any A/C it moves slowly because... there is no need for it to move fast. Instead there is the need for precision, hence the gearing always favors precision over rate of deflection, be it a complete mechanical system or electrical actuators (servomechanisms).