default aileron trim setting

 

That looks like a good bet. Can you do it in aircraft that don't have aileron trim?

 

So, if they are balanced to null-out the engine torque at cruise conditions, shouldn't they exhibit some roll tendency at different conditions? (e.g. idle engine and descenting at cruise speed, max power at low speed, etc.).

 

Yes. I believe he even mentioned this in one post.

 

A Cessna 152 requires right rudder on takeoff and climb, left rudder on descent, and no correction needed in cruise flight. I know one factor used to balance this is an angle offset in the vertical stabilizer, and I'm sure there are others. There will be similar fixes designed into the aircraft for other forces like roll. While you may get some left roll under power, at cruise condition the aircraft should be stable. In fact, you may not notice any left rolling tendency in climb power because the right rudder required to keep the nose straight will tend to offset it, more or less, depending on the aircraft

 

Hook

That looks like a good bet. Can you do it in aircraft that don't have aileron trim?

Hook

 

Every aircraft that begins in Planemaker has aileron trim. If the real one doesn't have aileron trim, the aileron trim values in X-Plane are left at zero. So yes, you can adjust default aileron trim position in any add on.

When aircraft are built, they're test flown to show any roll tendency at cruise speeds. They should remain level without pressure on the stick.

 

Would you be so kind and name the available aircrafts that get it wrong in X-plane so that we get warned or on the other hand have a chance to try it. Because there are planes that get it right. I can e.g. get the Blackshape Prime into a nice stable cruise flight just by adjusting power and without touching aileron trim. Apparantly Carenados and Gorans planes aren't that bad either.

 

Please keep the discussion very tight and precise and name examples, what you did in sim and what would have been the "perfect" outcome.

 

Everything else is religion. Believe it or believe it not that X-Plane has a basic flaw that affects "it all".

Would you be so kind and name the available aircrafts that get it wrong in X-plane so that we get warned or on the other hand have a chance to try it.

 

The default Baron has been given as an example many times in this thread. You'll have to do your own research to find others; just check the default aircraft. We know that third party aircraft don't have the problem, and there are ways to adjust it out in the Baron. I'd try the default aileron trim in Planemaker first, as that should fix the problem without introducing side effects, and works even on aircraft that do not have aileron trim.

 

When a problem is pointed out, instead of getting defensive, admit the problem is there and suggest a fix or workaround. Pretending the problems aren't there, or worse, suggesting they are normal behavior for that aircraft aren't doing anyone any favors, especially XPlane.

 

It's not like similar problems don't exist in other flight sims. Here's how I handled the same problem in Microsoft Flight.

 

After the last update, the aircraft had a tendency to roll to the left, and the available trims were far too coarse to adjust out the problem (sound familiar?). When someone complained, the typical answer was, "Yes, we know about the roll and no one likes it. While the trim is useless for fixing this, you can burn fuel from the left tanks until the planes are stable, then switch to all tanks." Flight didn't come with a utility like Planemaker.

 

FSX had a different problem:

 

The DG808S sailplane flew nose up at recommended speeds. I changed the cruise_lift_scalar from 1.0 to 1.25 (I think that's the value I used at the time) and the plane flew level. The Grumman Goose flew nose low, and for that plane I cut the cruise_lift_scalar in half, from 1.0 to 0.5 and raised the prop thrust scalar from 1.0 to 1.2 to compensate for the lack of performance. Since then I've done more complex fixes.

 

Oh, and thanks again to GoranM for information on what's available in Planemaker.

 

Hook

The default baron needs ca. 16 MP and 2400 rpm in order to fly straight without aileron trim. Yes, that's anything but cruise settings. My question was: Is it a X-Plane issue or are only certain planes the bad apples, like some of the default (I don't fly them often, only the C90 from time to time). If so, take it up to the developer if you want to have it improved, in this case Tom Kyler.

My question was: Is it a X-Plane issue or are only certain planes the bad apples, like some of the default

 

We know that third party aircraft don't have the problem, and there are ways to adjust it out in the Baron.

 

Hope that helps.

 

Hook

fine. hope it helps others, too

I am not discussing this here any further Markus. I am confident in my interpretation of what's going (pic below).

 

 

 

We know that third party aircraft don't have the problem......

A flight model in x-plane has no concept of whether or not it is a third party flight model. Such vernacular and rhetoric make discussion of the topic here futile.

 

TomK

A flight model in x-plane has no concept of whether or not it is a third party flight model.

 

That was my point. Apparently only some default aircraft have the problem, as third party developers have adjusted the flight models appropriately, and even the default aircraft can be adjusted.

 

Identifying a problem, and finding a solution, is never futile. For example, if the Baron roll problem is brought up in the future, there's an answer and a fix. The only thing people can complain about now about the Baron is why hasn't it been fixed by the developer. I can't answer that one.

 

Actually, I like the idea of having a "default aileron trim" adjustment. I don't think FSX has anything like that.

 

Hook

Here is my interpretation B)

 

 

FAR part 23, section 171, general:

 

"The airplane must be longitudinally, directionally, and laterally stable under 23.173 thru 23.181.

In addition, the airplane must show suitable stability and control feel (static stability) in any condition normally encountered in service, if flight tests show it is necessary for safe operation.

 

My hope is that we can merge regulations and engineering in the sim same as rw...

Well, I have to say a readthrough of this entire thread has been very enlightening. it answers a number of questions I had, although probably unintentionally. No wonder things are the way they are.

 

Thanks to TomK for providing a fix for the roll instability for the Baron which will be included in a future version of XPlane.

 

Hook

 

PS.

 

the airplane must show suitable stability and control feel (static stability) in any condition normally encountered in service

 

Looks like TomK may have done that.

 

H.

I hope so-if so-it is great news! Now for the rest of my fleet... :rolleyes:

This is a well worded description of the issue we seek to resolve.

 

http://ma3naido.blog...e-reaction.html

 

This supports my assertion that some form of asymmetrical lift has to be applied to adjust for engine torque in order to keep a non counter-rotating twin wings level at a given speed. The tools available to the real world designer are myriad. As long as lift is increased on one side, the effect can be neutralized, but only at a given speed. x-Plane has only a few tools to simulate this effect...the most prominent is "default aileron trim" and the method I choose to use in the absense of slipstream corkscrew effects or any other trim inducing device that Beech has employed that I am unaware of. This technique in x-plane deflects the aileron a default amount so that when your "trim wheel" is in the neutral position, the ailerons are still deflected a tiny bit. From Austin's perspective, it's just a roll force..whether it's from a trim tab or the aileron matters not. This setting has been calibrated for "reasonable" wings level at about 160 knots. By reasonable I mean I can fly a specific speed "hands off" and the plane will only roll very slowly. I am sorry, but as an engineer, I can't in good conscious say that a plane with the control yoke ridgidly locked would remain perfectly "roll free". The goal is to put slight pressure...but given flight sim hardware and it's spring centering....there's just no way to get the feel to that level.

 

Where I think many of us get caught up here is some feel this is a "cheat". I mean, no real trim is used i the plane, why is it used in x-plane. My response to that is simply that some method must be employed in reality...whether it's engine offset, bent trim tabs or whatever...in x-plane, the simplest and easiest is the default aileron trim. I am intersted in exploring other solutions designers may use though and ideally, it'd be nice to employ the same methods as the real beech baron.....whether it's some form of rigging, a trim tab, offset or canted engines I have no idea. Until then though, the default aileron trim tab, set to balance the plane at cruise is the method I'm using.

 

Tom K

the default aileron trim tab, set to balance the plane at cruise is the method I'm using.

 

When GoranM listed the various factors that might be changed, this was the one that looked like the best to do the job without causing side effects and still allowing for proper torque forces with different power settings. I doubt that anyone in the cockpit would be able to determine which of several torque stabilization methods is in use.

 

I can fly a specific speed "hands off" and the plane will only roll very slowly. I am sorry, but as an engineer, I can't in good conscious say that a plane with the control yoke ridgidly locked would remain perfectly "roll free".

 

I think most residual roll tendency would be neutralized by dihedral. I doubt anyone's going to mind if any remaining roll tendency is adjustable by use of the power setting, with a power band that produces no *perceptible* roll because the dihedral keeps the aircraft steady.

 

Atmospheric forces will cause the wings to move away from level, but the plane should still seek the level condition due to dihedral which will allow general hands-off flying in relatively smooth air with only slight adjustments with the rudder pedals.

 

I've seen a number of people complain that some aircraft flies "as if on rails" but that's not a fault of the flight model, it's a fault of the atmosphere model. Some days and times of day the air will actually be that smooth, but it's not going to be a default condition. For the purposes of a flight sim, people are still going to want to be able to specify perfectly smooth air, though.

 

Good post, btw. Thanks.

 

Hook

I used also artificial stability in PM. It can be tunned to allow for even the @negative@ torque effects when the power is reduced in a prop aircraft, even when no other techniques are used such as canted prop or tail, asymmetric lift, etc, that could then come to play, the reason why some aircraft require left rudder&aileron when descending at low power, even if their engines are not canted, etc...

 

I believe at least one Carenado also uses this technique.

 

I am satisfied with either for the time being, but looking for the day Austin announces that XP FM includes the same detailled flight dynamics model used in DCS World, and particularly on their p51d, where indeed, all of the players come to play ! There is the asymmetric spriraling slisptream effect, torque, p factor, gyroscopic effects... well, that-s why DCS became my preferred flightsim ...