Swirling tailwheel

[effte]

Flight ace,

good job at definitions. No objections, apart from the fact that you omitted the importance of choosing the right size bucket when you go to fetch more prop wash... ;)

[cichlidfan]

I don't know if this is of any value but today I caught the tailwheel/aircraft doing something odd.

 

I was doing some testing when the plane started to roll. The tailwheel was likely unlocked since I had just unlocked the stick so I half-heartedly tried to gain control and bounced the running prop off of the ground. This caused the plane to roll backwards, in a circle, forever. I finally stopped the sim but the aircraft had not given any indication of slowing down much less stopping. The tailwheel looks like it is sliding sideways almost, or that could be the view making it look that way.

 

I watched for over a minute, I think, before I turned Fraps on. By this time my hands, and feet, were long since off of the controls. I attached the track but to get to the good part you will have to sit through quite a few minutes of me testing controller buttons for starting the plane.

 

Also, notice right near the beginning of the video the plane goes straight for a short distance, for no apparent reason, before going back to circling. Sorry for the lousy camera work.

 

Hopefully this is of some use.

tail wheel physics.trk

[HiJack]

Thats not jus a swirling tailwheel, it's swirling p-51 :P

[cichlidfan]

Thats not jus a swirling tailwheel, it's swirling p-51 :P

 

Backward donuts, hands free!:D

[lobo]

I don't know if this is of any value but today I caught the tailwheel/aircraft doing something odd.

 

 

I am thinking the tailwheel physics is still a WIP.

 

Sitting on the ground, engine running, not moving, push the stick slightly forward to unlock TW. Do nothing else. Now watch what the TW does... it will slowly rotate 180 degrees and stop. Even if you keep the stick forward the TW will stop rotation at 180 degrees.

 

The way the TW is designed I cant see how this can happen. In my taildragger experience the only time the TW should flip around backwards is if you have some backwards momentum.

 

It's as if something in the tailwheel assembly physics model is off by 180 degrees. This would possibly account for the difficulty of taxiing with the TW unlocked.

 

Hopefully it is a beta/WIP issue.

 

See this video for an example:

 

Edited May 21, 2012 by lobo**

[159th_Viper]

I am thinking the tailwheel physics is still a WIP......Hopefully it is a beta/WIP issue....

 

I'm finding out and I'll let you know.

[lobo]

I'm finding out and I'll let you know.

 

Thanks Viper. :thumbup:

[effte]

I grabbed a pair of screenies the other night, showing that there is some caster to the tail wheel pivot axis. Together with the trail, this means part of the reaction force from placing weight on the tail wheel will create a torque striving to align the tail wheel with the fuselage...

 

...pointing to the rear, one might add. ;)

[JimMack]

I grabbed a pair of screenies the other night, showing that there is some caster to the tail wheel pivot axis. Together with the trail, this means part of the reaction force from placing weight on the tail wheel will create a torque striving to align the tail wheel with the fuselage...

 

...pointing to the rear, one might add. ;)

 

Velma is currently in maintenance. Once we start taxiing trials I'll make a video, wheels locked, unlocked, S turns etc.

[sobek]

If possible, it would be very interesting to see what the operators feet are doing during taxiing (brake operation, rudder, etc).

[effte]

Velma is currently in maintenance. Once we start taxiing trials I'll make a video, wheels locked, unlocked, S turns etc.

 

Awesome!!!

 

Gonna have to pay you guys a visit. I think I'll wait out the olympics debacle though...

 

(Perhaps you can spare the time to tell me if I'm correct or way off the mark regarding the ignition system in this thread as well?)

 

Cheers,

Fred

[HiJack]

Watch this video and look closely at the tailwheel movement at 6:30. Now do not tell me that this movement during parking is made by propwash. It is made by the stick movement with the stick in forward position.

 

And he is breaking the left wheel of course but the tailwheel does not "spin" off uncontrollably.

 

Edited May 17, 2012 by HiJack

[lobo]

Here is another example of taxing with the tail wheel locked and then unlocked. At :40 you can see the tail wheel is unlocked by forward stick and down elevator. Again at 1:29 the tail wheel is unlocked. There appears to be a difference in controllabilty between the beta with tw unlocked and what we see in the videos of rl Mustang when tw is unlocked.

 

 

Another where you can see very positive control of the aircraft when tw is unlocked.

 

Edited May 18, 2012 by lobo**

[cichlidfan]

If possible, it would be very interesting to see what the operators feet are doing during taxiing (brake operation, rudder, etc).

 

Same for take-offs too.

 

While we are being greedy, including a view of manifold pressure during take-off would be extra nice!;)

[HiJack]

I'm finding out and I'll let you know.

Hey Viper. I made a quick video to ilustrate the problem.

 

 

(HJ)

[mrniel]

I think HiJack spotted the problem right on.

The tailwheel turning 180 when the aircraft holding still but with the stick forward.

The only situation where this should happen is if a small backward movement was induced.

I can understand it turning perhaps 90 degree to one side depending on torque or trim settings, but not 180 when holding still.

It mean that the tailwheel is sticking forward like a motorcycle, and when forward movement starts, it will try to reset to dragging, and for a short while sticking sideway giving severe turns.

<clearly needs to be look at.

[lobo]

Velma is currently in maintenance. Once we start taxiing trials I'll make a video, wheels locked, unlocked, S turns etc.

 

It would be very interesting to have a chat with a real world Mustang pilot who could compare the tail wheel unlocked operation of the actual P-51 vs DCS P-51.

[159th_Viper]

Hey Viper. I made a quick video to ilustrate the problem.

 

 

Issue has been submitted to the bug factory on 14/05/2012.

[Tailspin45]

Flew an SNJ (AT-6) with P-51 tailwheel installed (as many do) for about 10 years, and what the sim vids here show is not the way it should work.

 

With TO Assist at 100% the DCS '51 almost feels right, but with it off its pretty much unmanageable. Suspect this tailswheel thing is, or is related to, the problem. Otherwise, it's a terrific sim.

 

That lovely music the V-12 makes isn't near loud enough, though. :smilewink:.

[effte]

Stumbled across an interesting article, PIREP on the T-6, a while ago.

 

Some highlights:

 

"Start out in a Bearcat, transition to the P-51 and then you're ready for the T-6."

 

Edwards was referring to the T--6's less-then-spotless reputation for ground handling. And he's right. Many civilians transitioning into fighter aircraft are amazed at how much easier fighters are to handle (in most situations, anyway) then the old Texan, a supposedly easily-tamed "trainer." When I got my chance to fly Mustangs, I was amazed and relieved to find this was absolutely the case. If the P-51 had been the quantum jump up from the T-6 in ground handling difficulties that it was in aerial performance, my first Mustang hop would have culminated in a spectacular fire at the edge of the runway. Even if I kept control and survived the flight, I would have drowned in post-flight adrenaline flow. Obviously it didn't happen that way because the Mustang was such a pussy cat compared to the Texan.

 

I can't speak for others, but the Six had me so wired fo abysmal ground handling that the Mustang was a breath of fresh air. There was nothing that big bird could do that would surprise me. Yes, "relieved" is definitely the right word.

 

...

 

As soon as the power is against the stop, the tail is picked up gently (repeat, gently) and the airplane will fly off with little or no provocation from the pilot who thinks he's in command. Hoist the tail vigorously and you'll get a surprisingly quick swing to the left as the gyroscopic precession of the prop kicks in.

 

...

 

As a normal rule, I'll opt for a three-point landing and I slide my feet up high on the rudder pedals to give mechanical advantage on the brakes should I need them. Actually, the only assumption you can make about a T-6 at all is that it is going to swerve one way or the other and you can't be sure which way. So you plan accordingly, getting your nerves and feet ready to handle whatever it dishes out. The results of a bad swerve can be really exciting-like crumpled wings, folded landing gear, etc. If you do it really right, you'll be awarded with a view of the airport from an upside down position alongside the runway. The trick is to catch the swerves right at the beginning while they are still tiny turns. Nip each of those in the bud and the airplane is absolutely no problem. It only gets nasty, if you let the nose wander too far before getting your feet in the act.

 

The machine wheel lands quite easily, which is what most folks do these days. However, the swerving tendency is still there and you have to be wide awake as the tail settles because it just loves to meander as the wind goes out of the rudder.

 

But I reiterate my previous statement that it's probably WIP and we should all remain calm for now. :)

[lubey]

I grabbed a pair of screenies the other night, showing that there is some caster to the tail wheel pivot axis. Together with the trail, this means part of the reaction force from placing weight on the tail wheel will create a torque striving to align the tail wheel with the fuselage...

 

...pointing to the rear, one might add. ;)

 

I think the tail wheel doors hide stuff and make it look like there is a lot more caster angle than there actually is. Compare to this picture from the DCS website:

 

 

 

Notice how the tail wheel steering/swivelling axis is actually more or less vertical (if the picture were rotated as if the plane was sitting on 3 wheels on the ground)? There is just a bend in the shaft which creates a horizontal offset between the axis and the contact patch of the wheel. So I think the tail wheel would be much more inclined to align with its relative direction of travel than the fuselage of the aircraft as you're saying, much like in a shopping trolley. Of course there still would be friction in the steering axis, resisting the tail wheel from being completely free-swivelling so potentially making the plane more resistant to ground looping than it is and also not making the wheel automatically turn 180deg for no reason.

[HiJack]

I can confirm that the tailwheel now works as supposed! Thanks ED :D

[Tailspin45]

Concur. Feels good now in V1.2. They did a nice job tweaking ground and airborne handling.

[joker68]

I can confirm that the tailwheel now works as supposed! Thanks ED :D

Sorry, but not for me.

I'm a rl taildragger pilot, and when I press full rudder in some direction and then gently apply power, the plane starts to go to that direction after going forward for a few inches.

In P51, if I put the stick forward and start to do a *very gentle* turn to either side, *no matter what I do after*, it will not go to other side, nevermore. It will just stay there doing donuts.

I can stop the plane, apply full rudder in the opposite direction, and as soon as I apply power, it will start to continue his previous turn, regardless of my rudder position. Doesn't matter if I put full power or not. In other words, it behaves like I don't have a rudder (no authority at all). I can do several complete donuts applying rudder in the opposite direction, it just doesn't matter, it's "game over".

This is unrealistic, IMHO.

[WildBillKelsoe]

In A2A's, if you push the stick forward, you steer with rudder (mostly) and brakes (leastly). In DCS, if you push stick forward, you steer (mostly) with brakes, and (leastly) with rudder. Give me an airport so I can give you a track. I can without hassle taxi using stick forward without trouble.