missing info Tailwheel Flight Model

[maajr57]

Thanks grafspee!

[maajr57]

https://youtu.be/5nU7kgEXOMk

Gentlemen start your engines and try this in DCS. A 2 wheel takeoff from the end of the runway in a crosswind. Drive all the way down the runway on 2 wheels before liftoff.  I did this one for demonstration in X-Plane 11 with a Skunkcrafts P51 for comparison. I can't do this in DCS which is why I started this thread. Good Luck Gentlemen!

[kablamoman]

3 hours ago, maajr57 said:

https://youtu.be/5nU7kgEXOMk

Gentlemen start your engines and try this in DCS. A 2 wheel takeoff from the end of the runway in a crosswind. Drive all the way down the runway on 2 wheels before liftoff.  I did this one for demonstration in X-Plane 11 with a Skunkcrafts P51 for comparison. I can't do this in DCS which is why I started this thread. Good Luck Gentlemen!

Not sure what this is supposed to demonstrate -- you're not even supposed to have the gear extended beyond 170 mph indicated, but you're over 200 by the time you unstick. Maybe if there is something specific you can point to, rather than trying to glean anything from how other sims behave, that would help a bit.

If anything, in real life if you were performing this kind of stunt, blazing down the runway and intentionally keeping the wheels on the ground (something you would not want to do in a heavy crosswind) I would think that only the upwind wheel would be touching if you are properly compensating for a strong crosswind. While DCS warbirds can be pretty squirrely and have some odd stuff happening, especially when the wheels are in contact with the ground at an unrealistically high speed, it's still not impossible to do what you're attempting.

Just to indulge a little, here is my attempt to do what you're requesting (bonus crosswind landing, too):

Here are the settings I used (~20 knot crosswind):

Edited December 3, 2022 by kablamoman

[kablamoman]

It also just occurred to me that you could unintentionally have "Take off assistance" activated in the special options menu (you can't change it while in-game, and must exit to the main menu and go to settings there to find it). This can sometimes get reset and activated between game updates, or even for particular missions and could absolutely add a bunch of unwanted rudder input that could be messing with your takeoff technique.

Might want to double check that it is turned off for the P51.

Edited December 3, 2022 by kablamoman

[grafspee]

It is in options/special tab access only from main menu. I just went there and i found out that take off assist was at 100% in P-51, like @kablamomansaid, it is worth to check this regularly 

Edited December 3, 2022 by grafspee

[maajr57]

Simulation mode

Auto rudder = 0

Takeoff assistance = 0

The point is that I have been unable to lift the tail without the prop pulling right and into the ground making a 2 wheel takeoff impossible.

Takeoff assist and auto rudder makes takeoffs easier. If yours is on, you are cheating.

[grafspee]

1 hour ago, maajr57 said:

 

Takeoff assist and auto rudder makes takeoffs easier. If yours is on, you are cheating.

Only if you know that, if you try fight it during take off it makes a lot of mess.

[kablamoman]

2 hours ago, maajr57 said:

Simulation mode

Auto rudder = 0

Takeoff assistance = 0

The point is that I have been unable to lift the tail without the prop pulling right and into the ground making a 2 wheel takeoff impossible.

Takeoff assist and auto rudder makes takeoffs easier. If yours is on, you are cheating.

Hey Maajr, I just went back and watched the in-game track you made of your DCS take off attempt. I see what you're talking about with you nosing over and going right. From what I can tell it looks like you're overcontrolling quite a bit while also trying to lift the tail before you have actually arrested the yaw-wise acceleration.

I don't think the gyroscopic effect is the cause of your problems -- indeed lifting the tail should result in a left yaw tendency that requires right rudder to correct. In the track you provided, you start the roll, but then quickly oscillate right, left and right again at increasingly longer periods. Your control deflections also become more extreme in response to this, and by the time you lift the tail your nose is already well on its way sideways and into the dirt.

I seems like a classic case of some pilot induced oscillation.

I would recommend trying to focus on using right rudder inputs only, and merely varying the input from "a fair amount" to "a little bit less" -- but only on the right side -- in order to stabilize your directional control. Resist the urge to actually add left pedal to steer back left, just reduce the amount of right pedal, if that makes sense.

Then be patient. Wait to gain a bit of speed and to be going dead straight down the runway before you try to force the tail up and the nose down (and be prepared to add a little more right rudder when you do so). The more slowly and smoothly you lift the tail, the more time you'll have to follow it with the proper amount of change to your right rudder input.

I hope this helps. Good luck.

[Art-J]

Also, just for unified conditions comparison, It wold be nice to know what crosswind was set in XP11 video, so that we can replicate exactly the same wind speed and direction in DCS.

[maajr57]

4 hours ago, Art-J said:

Also, just for unified conditions comparison, It wold be nice to know what crosswind was set in XP11 video, so that we can replicate exactly the same wind speed and direction in DCS.

We are doing the Challenge Campaign Mission 3 which comes with the P-51D. The wind is 10 meters per second or 20 knots perpendicular to the runway.

[maajr57]

4 hours ago, kablamoman said:

Hey Maajr, I just went back and watched the in-game track you made of your DCS take off attempt. I see what you're talking about with you nosing over and going right. From what I can tell it looks like you're quite a bit while also trying to lift the tail before you have actually arrested the yaw-wise acceleration.

I don't think the gyroscopic effect is the cause of your problems -- indeed lifting the tail should result in a left yaw tendency that requires right rudder to correct. In the track you provided, you start the roll, but then quickly oscillate right, left and right again at increasingly longer periods. Your control deflections also become more extreme in response to this, and by the time you lift the tail your nose is already well on its way sideways and into the dirt.

I seems like a classic case of some pilot induced oscillation.

I would recommend trying to focus on using right rudder inputs only, and merely varying the input from "a fair amount" to "a little bit less" -- but only on the right side -- in order to stabilize your directional control. Resist the urge to actually add left pedal to steer back left, just reduce the amount of right pedal, if that makes sense.

Then be patient. Wait to gain a bit of speed and to be going dead straight down the runway before you try to force the tail up and the nose down (and be prepared to add a little more right rudder when you do so). The more slowly and smoothly you lift the tail, the more time you'll have to follow it with the proper amount of change to your right rudder input.

I hope this helps. Good luck.

I appreciate the detailed and thoughtful reply. Will make sure I'm straight and stable before lifting the tail but Isn't lifting the tail going to require left rudder? Do you think the tail should be lifted at a slow speed or a fast speed? I do understand the gyro and why the prop pulls right but what I find unrealistic is the nosedive prop strike. Any explanation for that?

Edited December 3, 2022 by maajr57

[Art-J]

Just for the record, so that there's no misunderstanding, while lifting the tail the gyro effect in itself will cause yaw to the left (clockwise rotating prop), not to the right. I haven't played the challenge campaign since 2014, though, so don't remember what the wind direction is in that mission. It's not really realistic scenario anyway -  such strong crosswinds are usually avoided by small planes in real life.

I do remember heated debates from that era about counterintuitive yaw behaviour in initial phase of crosswind takeoff roll (plane wanting to yaw away from the wind rather than into it). Apparently it was supposed to be caused by some simulation of propwash deflection (?). When the rolling speed was high enough, however, the plane behaved as expected (weathervaning into the crosswind) and required relevant, intuitive inputs.

[maajr57]

36 minutes ago, Art-J said:

Just for the record, so that there's no misunderstanding, while lifting the tail the gyro effect in itself will cause yaw to the left (clockwise rotating prop), not to the right.

I stand corrected! This would agree with kablamoman who told me to stay primarily on the right rudder and the kitchen science below. So, if the gyro is yawing to the left, and the wind is coming from the left which should cause a weathervane yaw to the left, what is causing the plane to go right and nosedive into a propstrike?

 

[kablamoman]

3 hours ago, maajr57 said:

I appreciate the detailed and thoughtful reply. Will make sure I'm straight and stable before lifting the tail but Isn't lifting the tail going to require left rudder? Do you think the tail should be lifted at a slow speed or a fast speed? I do understand the gyro and why the prop pulls right but what I find unrealistic is the nosedive prop strike. Any explanation for that?

 

As Art mentioned. Lifting the tail induces left yaw in a clockwise rotating prop. You would need right rudder to counteract it.

lifting the tail should be done smoothly and deliberately. Don’t try to force it at too low an airspeed, wait till you’re going a bit faster and definitely make sure you’re rolling straight down the runway before you do it and then be gentle with your pitch control until you develop a good feel for it. The yaw response will be directly proportional to the pitch rotation acceleration so make it easy on yourself and ease it up.

as for the nose dive I think it was mainly just being too aggressive with the pitch down… maybe coupled with the left wheel digging in as you veered sideways.

For practice I’d say just try to be a little more fine on your controls. Not sure what your joystick setup is like, but if you have a short throw stick I would suggest a sensitivity curve of 20 for pitch/roll and 30 for yaw to start (right click on the individual axes in the control bindings and select “tune axis”, it will be the bottom slider) — see if that helps and you can tweak it as you get more practice and have a better feel.

 

Edited December 3, 2022 by kablamoman

[maajr57]

Getting closer Gentlemen! Check out this track. No crosswind. Smoother, patient, mostly right rudder. This track took a lot of experimentation. Less manifold pressure and more patience. Shouldn't the tail rise on it's own at some point or does it need to be lifted? If it's not lifted, takeoff occurs at too slow a speed. Does anyone have the official V speeds for the P-51? Should be in the manual but I don't see them. The goal for me is consistent 2 wheel takeoffs and landings. Thanks to all for the help and hopefully we can continue the discussion and practice.

Takeoff - No Crosswind.trk

[grafspee]

It depends on loadout, but combat P-51 won't rise tail as TF-51. Normally i would say that 90-100mph is when tail will rise.

[maajr57]

1 minute ago, grafspee said:

It depends on loadout, but combat P-51 won't rise tail as TF-51. Normally i would say that 90-100mph is when tail will rise.

Plane will leave the ground before the tail lifts on its own so we need foward stick to lift tail before 90. Thx grafspee!

[kablamoman]

1 hour ago, maajr57 said:

Getting closer Gentlemen! Check out this track. No crosswind. Smoother, patient, mostly right rudder. This track took a lot of experimentation. Less manifold pressure and more patience. Shouldn't the tail rise on it's own at some point or does it need to be lifted? If it's not lifted, takeoff occurs at too slow a speed. Does anyone have the official V speeds for the P-51? Should be in the manual but I don't see them. The goal for me is consistent 2 wheel takeoffs and landings. Thanks to all for the help and hopefully we can continue the discussion and practice.

Takeoff - No Crosswind.trk 2.08 MB · 2 downloads

Hey much better, my friend. Keep it up.

So much of the fun and mastery of flying ends up being pretty nuanced. I think that's why we all love it so much.

Lots of times we use instructions like "use right rudder when you add power" or "use right rudder when you lift the tail" and "rotate at 120 knots" as shorthand for conveying the basics efficiently, but they're really lacking a lot of information someone learning really needs. How much rudder do you add? When do you add it, exactly? How fast should you add it?

For takeoffs and landings, what really matters is what attitude you're trying to set and maintain, and how you do it. Not enough pilots in real life focus on this, and so rarely do you ever see players in the sim mention it.

But if your focus is actually on what you're seeing out the front of the plane, and how to set that picture and make it look the way you want it to look a lot of the rote "do this at this speed", "add right rudder", "add left aileron" instructions fall by the wayside because they are no longer required.

Learn what your three-point attitude looks like. At what angle does the horizon intersect the canopy from your typical seating position? A good takeoff attitude with tail off the ground is going to be a couple degrees below that. Once you have a good idea of what that looks like you can focus on using whatever control input you need, and in whatever proportions required, to set it and hold it. Same goes for directional control -- look down the runway, or at the edges if your nose it still pointed up -- are you going straight? If not, you have to fix it with the proper control deflections. Could be rudder, could be aileron, could be both. Is it working to give you the result you want? No? Maybe you need more rudder, or even brake, depending on where you are in the takeoff roll and what plane you're flying.

The point I'm trying to convey is that you should be focusing on the picture out front, and making sure the plane is going where you want, and the attitude is set where desired. Try not to put so much emphasis on the paint-by-numbers approach, as if you can get away from that habit and learn how to control your attitudes and movements you can fly any plane -- the only differences you end up having to learn are what "the picture" looks like, and how much and which control inputs you need to get it.

Edited December 3, 2022 by kablamoman

[Baldrick33]

1 hour ago, kablamoman said:

The point I'm trying to convey is that you should be focusing on the picture out front, and making sure the plane is going where you want, and the attitude is set where desired. Try not to put so much emphasis on the paint-by-numbers approach, as if you can get away from that habit and learn how to control your attitudes and movements you can fly any plane -- the only differences you end up having to learn are what "the picture" looks like, and how much and which control inputs you need to get it.

 

I agree. My background is sim racing and whilst this maybe not by any pilot instruction manual I just take off a taildragger by the seat of the pants with lots of small but rapid corrections. I never bother to trim, if the aircraft starts to yaw left I apply right rudder and vice versa, if the nose drops I pull the stick and so on. The rudder dance is much like managing oversteer to rotate a race/rally car with almost constantly applying small corrections to keep the car rotating as desired.

I am no great pilot but I just re did that campaign mission and took off without any issue. Maybe my reactions have been honed by many years of sim racing but it all feels kind of natural. VR may help a bunch too when it comes to feeling the sensation of movement as soon as it happens to apply the correction.

[maajr57]

1 hour ago, kablamoman said:

Hey much better, my friend. Keep it up.

So much of the fun and mastery of flying ends up being pretty nuanced. I think that's why we all love it so much.

Lots of times we use instructions like "use right rudder when you add power" or "use right rudder when you lift the tail" and "rotate at 120 knots" as shorthand for conveying the basics efficiently, but they're really lacking a lot of information someone learning really needs. How much rudder do you add? When do you add it, exactly? How fast should you add it?

For takeoffs and landings, what really matters is what attitude you're trying to set and maintain, and how you do it. Not enough pilots in real life focus on this, and so rarely do you ever see players in the sim mention it.

But if your focus is actually on what you're seeing out the front of the plane, and how to set that picture and make it look the way you want it to look a lot of the rote "do this at this speed", "add right rudder", "add left aileron" instructions fall by the wayside because they are no longer required.

Learn what your three-point attitude looks like. At what angle does the horizon intersect the canopy from your typical seating position? A good takeoff attitude with tail off the ground is going to be a couple degrees below that. Once you have a good idea of what that looks like you can focus on using whatever control input you need, and in whatever proportions required, to set it and hold it. Same goes for directional control -- look down the runway, or at the edges if your nose it still pointed up -- are you going straight? If not, you have to fix it with the proper control deflections. Could be rudder, could be aileron, could be both. Is it working to give you the result you want? No? Maybe you need more rudder, or even brake, depending on where you are in the takeoff roll and what plane you're flying.

The point I'm trying to convey is that you should be focusing on the picture out front, and making sure the plane is going where you want, and the attitude is set where desired. Try not to put so much emphasis on the paint-by-numbers approach, as if you can get away from that habit and learn how to control your attitudes and movements you can fly any plane -- the only differences you end up having to learn are what "the picture" looks like, and how much and which control inputs you need to get it.

 

Thanks Coach! Very thoughtful and insightful again!

[AJaromir]

On 12/2/2022 at 6:21 PM, maajr57 said:

Since you are the resident expert, would you please try some 2 wheel takeoffs rather than 3 point in the same crosswind scenario? 

Looking forward to your input. Thx

Will ASAP. It will be in next week. BTW the 2-point take off is not very realistic. It was not used for safety reasons.

On 12/2/2022 at 6:53 PM, maajr57 said:

Youtube rejected them, probably because it doesn't know what a TRK file is.

TRK is not video file. It is data file which is needed to replay track in DCS:World. I've recorded video using Nvidia Shadowplay tool and then uploaded it into Youtube.

[AJaromir]

On 12/3/2022 at 7:28 PM, maajr57 said:

So, if the gyro is yawing to the left, and the wind is coming from the left which should cause a weathervane yaw to the left, what is causing the plane to go right and nosedive into a propstrike?

It also works the opposite way. Yaw causes change of pitch. Action and reaction, Newton said.

Edited December 17, 2022 by AJaromir

[Yo-Yo]

On 11/9/2022 at 9:06 PM, AJaromir said:

Advice from old IL2 veteran. Using as wide field of view as possible helps to see the aircraft motion a lot. Then your reaction to motion will be much faster and better.

 

 

Clouds are good at the start of training    VR is better I heard, but not all of us have it.

[Yo-Yo]

20 kts X-wind seems to be too simple, so 20 units of turbulence were added. Thus, it's necessary not only to react to the plane but to the kicks from the Universe...
Both tracks were recorded after only one familiarization flight.
 

 

[maajr57]

3 hours ago, Yo-Yo said:

20 kts X-wind seems to be too simple, so 20 units of turbulence were added. Thus, it's necessary not only to react to the plane but to the kicks from the Universe...

Thx for the post. The issue and discussion was really about lifting the tail for a 2 wheel takeoff and the the yaw to the right and nosedive prop strike I was getting. Best advice was from Kablamoman who said to minimize left rudder and focus on the attitude of the plane to raise the tail. Light right rudder down the runway with a little short kick when the tail comes up. Still not convinced the prop strike is realistic with rudder alone but at least it won't happen to me anymore. Art-J also deserves a mention for correcting me about yaw direction when the tail comes up. Pulls to left, not right.