Lack of left turning tendencies
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@SadBucket Wait, what... So under high power and low airspeed, you're experiencing a left rolling moment and a right yawing moment? So without any pilot correction, the plane is putting itself into a left sideslip?
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@Buzz Yes, that is what I am experiencing, not too pronounced, but definitely feels wrong especially when you instinctively add right rudder and make the slip worse... 🥲
@SadBucket I was going to hold off on purchasing it, but figured I would do it at some point, so I just picked it up and can confirm what you all see.
Power is producing a left rolling moment which is correct, and a right yawing moment. It appears at first glance the yaw and roll moments scale with torque which is correct, but the yawing moment should also scale with increased prop disk AOA, which I'm not entirely sure is the case. It seems like the yawing tendency, is simply inverted. It also feels like the two are coupled, which should not be the case. Roll should be induced by engine torque regardless of AOA and Yaw should be induced by torque to a factor of prop disk AOA.
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@Black-Square said in Lack of left turning tendencies:
so there is no "click here to increase left-turning tendency",
But there is.
prop_mod_moment_scalar_yaw
That's the line in the engines.cfg for what you're looking for. It's almost a direct correlation between engine power transmission to the prop and turning tendencies due to things like p-factor. If I had to pull a number out of thin air, I'd guess you should try this at somewhere between 3 and 5 and see how it feels. I am away from my sim gear right now and can't test directly but that's where I'd start.
@CdnCptMoustache said in Lack of left turning tendencies:
prop_mod_moment_scalar_yaw
Tried, no change unfortunately. I never thought I'd be upset over not having to hit right rudder... ðŸ«
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@CdnCptMoustache said in Lack of left turning tendencies:
prop_mod_moment_scalar_yaw
Tried, no change unfortunately. I never thought I'd be upset over not having to hit right rudder... ðŸ«
You could try drastically increasing that number. If you find it then goes worse the wrong direction, set it negative.
If you're into humouring me, try setting it to something ridiculous like 40.
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You could try drastically increasing that number. If you find it then goes worse the wrong direction, set it negative.
If you're into humouring me, try setting it to something ridiculous like 40.
@CdnCptMoustache wut the heck, I'll report back in a minute
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You could try drastically increasing that number. If you find it then goes worse the wrong direction, set it negative.
If you're into humouring me, try setting it to something ridiculous like 40.
@CdnCptMoustache Update: 40 definitely does something... not enough right rudder in the world for that.
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@CdnCptMoustache Update: 40 definitely does something... not enough right rudder in the world for that.
@SadBucket Ah nice. That answers that
The "correct" number for that line obviously lies somewhere between 1 and 40 but without testing myself, it's really hard to say. There are any of a dozen things in the various lines that can impact the effect the prop has on yaw, such as engine angle, prop moment figures, yaw inertia, gyro stability, etc. I've seen that number vary from 0.2 up to 20 or so for what feels right in specific aircraft depending on everything else. I suspect it's the term "scalar" that's throwing people for a loop as it's more an effect and not so much a scalar.
At least it maybe gives Nick a little something to play with
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@CdnCptMoustache said in Lack of left turning tendencies:
prop_mod_moment_scalar_yaw
Tried, no change unfortunately. I never thought I'd be upset over not having to hit right rudder... ðŸ«
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@SadBucket Ah nice. That answers that
The "correct" number for that line obviously lies somewhere between 1 and 40 but without testing myself, it's really hard to say. There are any of a dozen things in the various lines that can impact the effect the prop has on yaw, such as engine angle, prop moment figures, yaw inertia, gyro stability, etc. I've seen that number vary from 0.2 up to 20 or so for what feels right in specific aircraft depending on everything else. I suspect it's the term "scalar" that's throwing people for a loop as it's more an effect and not so much a scalar.
At least it maybe gives Nick a little something to play with
@CdnCptMoustache Ok, there's definitely something else going on here with how the flight model is done. Setting the value to 15 the ball initially went left on rotation, then swung full right but very slowly with a constant airspeed of around 80kts, when applying a tiny bit of right rudder the ball would suddenly swing back full left. Definitely not a "click here to increase left-turning tendency"...
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@SadBucket All kidding aside It's understandable. It's hard to believe that this wasn't identified in beta.
@Buzz These things are always a surprise to me too on release day. I have a wonderful team of beta testers, who give me great advice on everything from usability to "nice-to-haves", but there will always be some things that just evade our attention. Some of these things seem painfully obvious to me too on release day, but when explaining the complexity of these aircraft, I often say to friends, "there was a day when I really cared about that one pixel on the panel right there." Thanks for being patient with me, and always being so constructive.
@CdnCptMoustache Thanks for working on the problem here. I will investigate what prop_mod_moment_scalar_yaw is actually doing, since it can be hard to tell what unintended consequences there might be from the short descriptions in the SDK. The other variable I'm familiar with is rudder_engine_wash_on_roll, which acts as a kind of built in "assistance", applying virtual rudder trim to counteract aggressive turning tendencies. I've used this in my twins before to get the effect my twin pilots were looking for. It has a smaller value in some of my other aircraft, so that's where I was going to start before adjusting the propeller model.
By all means, keep the suggestions coming. I always have a long list of things I start working on as soon as your feedback starts coming in, so please don't let the lack of any immediate response give you the impression that I'm not interested in your feedback, or not already working the problem myself.
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Just to be clear, I'm basing my experience/recommendation for prop_mod_moment_scalar_yaw on dozens of my own mods and hundreds of hours of my own personal experimentation. The SDK documentation is all but useless for things like this. I've had negative experience with rudder_engine_wash_on_roll. That is, it tends to not do what you'd expect from the SDK writeup. My theory is in switching to modern prop physics, that battles one of the new variables instead of being switched off entirely like p_factor_on_yaw in the flight model.
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@Black-Square Nick, if your using a sim parameter to induce the rolling moment of torque, make sure the parameter your using isn't mimicking left aileron deflection, if it is, then the right yawing moment may be caused by adverse yaw from the application of what you may be using to induce the torque roll. This was the first thing that popped out to me when I flew it. The yawing force seemed to be coupled to the torque roll. Felt exactly like the plane had a left aileron applied, thus causing adverse yaw.
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@Black-Square Nick, if your using a sim parameter to induce the rolling moment of torque, make sure the parameter your using isn't mimicking left aileron deflection, if it is, then the right yawing moment may be caused by adverse yaw from the application of what you may be using to induce the torque roll. This was the first thing that popped out to me when I flew it. The yawing force seemed to be coupled to the torque roll. Felt exactly like the plane had a left aileron applied, thus causing adverse yaw.
@Buzz You can get fun effects like that with things like too much or too little virtual dihedral, wing aoa, wing twist, induced drag scaling, or a bunch of other things. Fun rabbit hole, isn't it?
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@Buzz You can get fun effects like that with things like too much or too little virtual dihedral, wing aoa, wing twist, induced drag scaling, or a bunch of other things. Fun rabbit hole, isn't it?
@CdnCptMoustache I always thought it would be fun to use my RL aviation experience and passion for aerodynamics to help test simulation flight models, but I have no idea nor do I want to know how to "Wrench" on the simulation flight model.
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@Buzz You can get fun effects like that with things like too much or too little virtual dihedral, wing aoa, wing twist, induced drag scaling, or a bunch of other things. Fun rabbit hole, isn't it?
@CdnCptMoustache That makes sense, since a change in dihedral, AOA, Induced drag or twist will create a difference in lift (Drag) between the two wings, but only if in a bank. In level flight, those changes should not create adverse yaw.
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@Black-Square Just by the names, my guess is.
"prop_mod_moment_scalar_yaw" is a factor to P-Factor of the model. More should increase the left yaw moment under high power high prop disk AOA.
"rudder_engine_wash_on_roll" Sounds like the rolling force created by the spiraling slipstream of the prop hitting the vertical stabilizer on the left side above the CG, thus causing a right rolling moment. This should scale upward with an increase in power and a decrease in airspeed. If there is a parameter called "rudder_engine_wash_on_yaw", my guess is this would be the left yawing moment caused by the same spiraling slipstream hitting the vertical stabilizer on the left side, thus pushing the nose to the left.
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@CdnCptMoustache That makes sense, since a change in dihedral, AOA, Induced drag or twist will create a difference in lift (Drag) between the two wings, but only if in a bank. In level flight, those changes should not create adverse yaw.
@Buzz Correct. Not on their own they won't create adverse yaw but coupled with other unique sim-isms and some mildly misbehaving numbers in other areas the configs, you can get visible extremes. For example, combine a wing with too much twist with a plane that has the tendency to skid in a turn and you can get either positive or negative yaw/roll coupling depending on the twist number and direction (and the SDK would lead you to believe the twist works backwards from what it does. Did you know that most helis in the sim have their blades twisted the wrong way and have more aoa at the tips? I digress). Or combine that with a plane that has too little fuselage side area and a tendency to skid in level flight. Or too little yaw stability so it wanders. Or.... well the list goes on. And how the sim handles some of these extremes is less-than-ideal. But the good news is, get those in check and make this number mate up with that number and you get something that flies really, really nice.
This is getting a tad off topic now as I'm not really talking about the Caravan at all with all of the above but flightsim aircraft in general. My favourite was one plane a few years back that would have negative roll coupling to yaw, then when you gently corrected it, it would snap roll the wrong direction.
At any rate, when I can get a minute I'll fire up the sim and see if I can come up with specific recommendations for the Caravan.
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@CdnCptMoustache sounds like you know what your talking about. What your describing with the sim sounds frustrating for developers trying to get a flight model close on first draft. IMHO, you should be able to simply plug in real world values to get something that is good enough to start making minor tweaks to hit published performance tables and real world flight characteristics.
