Swirling tailwheel

The manual states that the tailwheel "tend to bind" in the meaning that it may get "stuck" in a possition. As it is now it is impossible to get a good taxiing when dealing with tight corners and most certainly not possible to taxi as described in the pilot manual. As for now the tailwheel lives its own life when you press the stick froward, I think that is wrong, there must be some friction working on the wheel. Can someone do some taxiing with some tight turns and post the track?

From the pilots manual:

(HJ)

The point is to use left or right brake, depending on the direction of the turn. In general, I use the following procedure:

1. Slow down or even stop the plane

2. Stick forward of neutral

3. Gently accellerate (to have enough speed to perform the turn without getting stuck in the middle)

4. Use gentle input on the right/left brake to have the plane turn into the desired direction, release the brake as soon as possible or risk entering a circle (which is hard to leave)

5. Align the plane so it rolls straight forward, keep it that way for a few meters

6. Slow down if necessary

7. Stick aft of neutral or neutral to lock the tail wheel again

The tail wheel "locks" in terms of "it takes its time for the tail wheel to turn into a trailing position" especially after sharp turns that weren't finished in a straight forward movement long enough to align the wheel. As a result, the tail will be forced towards the direction the tail wheel is "pointing to".

Hmm, hope this is understandable... ?

Yes that seams fine but if you are going strait ahead and free the tail wheel it does not start to swirl around as in the DCS P-51D. Here is anothere explanation of the situation "tend to bind" from the repair manual. Check step 3 that states the tailwheel "CAN get out of line with the rudder" but will of course normaly follow the rudder movements through the steering cables. In DCS P-51D the wheel have its own life, and it should not!

[ATTACH]65471[/ATTACH]

Seems as if I got you wrong. I never pushed the stick forward while going straight forward, so I never encountered the symptom you describe.

As I understand the tail wheel mechanism, it is "subject to pilot's control" only when the stick is aft and the locking mechanism is in place. Limited operating range (6° left/right) and most definately some friction (probably negligible). Once the stick is pushed forward, the tail wheel is unlocked and free to swivel in any direction. I understand the "tend to bind" remark in the manuals as being caused by the locking mechanism unable to disengage due to strong forces acting upon it, thus further limiting the tail wheel range to 6°. I still might be wrong.

I indeed would expect to see the plane turning in any one direction as soon as the tailwheel is unlocked. Torque, p-factor, wind, etc. would inevitably force the plane to leave its formerly straight path.

It may all be just practise. I also see the repair manual is stating that the tailwheel can sving freely 360°.

EDIT: Thanks for replying Luigi! :D

Taxiing a tail wheel aircraft requires considerably more skill than a nosewheel aircraft. When the tailwheel is unlocked it will swivel freely like the castor on your chair. Brakes, speed, practice. You really only need to unlock the tailwheel for sharp turns. For the straight stretches leave it locked. The B-18 on the ground your feet were always moving. You had to almost had to sense which way it was about to start turning before it started.

It's been a couple decades since I flew a taildragger... IMO it seems the folks at ED did not pull any punches with the modelling of the taildragger experience and for that I salute them. :pilotfly:

You had to almost had to sense which way it was about to start turning before it started.

That was exactly wht I have been told. Anticipate the aircraft's movement and counteract by using rudder.

How does one anticipate an aircraft's movement while sitting on a regular office chair in front of a computer screen? This is the most meh thing that didn't change for the last twenty or what years... Oh, and don't tell me of these (really cool) raceseats (or however they are called), they're simply unaffordable to me. :(

As I understand the tail wheel mechanism, it is "subject to pilot's control" only when the stick is aft and the locking mechanism is in place. Limited operating range (6° left/right) and most definately some friction (probably negligible). Once the stick is pushed forward, the tail wheel is unlocked and free to swivel in any direction. I understand the "tend to bind" remark in the manuals as being caused by the locking mechanism unable to disengage due to strong forces acting upon it, thus further limiting the tail wheel range to 6°. I still might be wrong.

IMHO the "tends to bind" comment is in regard to the taildragger behaviour of having the CG behind the mainwheels, thus having a tendency to sharpen the turn by itself.

I'm sorry folks but the tailwheel should not direct the aircraft in to a 180° turn just by forwarding the stick. In the provided tracks the only change is stick forward and it is completly uncontrollable. I would like any of you "pros" taxiing down the runway and periodicly move your stick all the way forward. But before you do, read the first post here witch describes taxiing. Read point 2 about how to straiten the tailwhel again also!

Taxiing 1.trk

Taxiing 2.trk

(HJ)

IMHO the "tends to bind" comment is in regard to the taildragger behaviour of having the CG behind the mainwheels, thus having a tendency to sharpen the turn by itself.

On the ones I flew if you had a side load on the tailwheel you would have difficulty or more likely be unable to unlock it, (it was binding) also it would not lock if you were already turning.

Here's a couple quotes I like re taildraggers:

"In a taildragger, picture your favorite shopping cart pushed backward,

the center of gravity is behind the main wheels. If you draw a

diagram of the forces, you'll see that the momentum vector will tend

to cause the tail to tend to continue swinging out after a swerve.

After a certain point, the CG will be outside the wheel and there's

nothing you can do to stop it from continuing to swing around. This

tends to be hard on the landing gear and wingtips. You want to keep

the momentum vector between the wheels if you want to stay in control."

and this:

"A ground loop is an inadvertant maneuver that allows you to visits parts of

the airport that you never knew existed before..."

I'm no "pro" so I'd better shut up, but I cannot resist ;) To me your tracks seem OK and correspond to what I encounter while taxiing.

I'm sorry folks but the tailwheel should not direct the aircraft in to a 180° turn just by forwarding the stick. In the provided tracks the only change is stick forward and it is completly uncontrollable. I would like any of you "pros" taxiing down the runway and periodicly move your stick all the way forward. But before you do, read the first post here witch describes taxiing. Read point 2 about how to straiten the tailwhel again also!

The tailwheel and attendant functionality is fine. With flightstick forward it is controlled with the left and right toebrakes :)

As stated previously, utilize differential braking and all should be OK. Herewith attached a quick and dirty track where I am goofing around with a couple of 90 degree turns, 180 degree turns and everything inbetween, alternating between 6 degree locked and free tail-wheel turns.

Track: Tailwheel.trk

Great track there Viper! Just what I wanted. So I can conclude that operating the tailwheel without pedals is a no go. I have mapped the brakes to the stick but it's not good at all.

Btw. Viper did you make it out of that takeoff? :P

So I can conclude that operating the tailwheel without pedals is a no go.

You could try mapping the left and right brake to the Numarrow keys. Then again, you need your hand for throttle control. It's true what they say - you need 4 hands for the Mustang.

Btw. Viper did you make it out of that takeoff? :P

:megalol:......erm..........no.

I Pancaked her properly.

There's significant caster to the tail wheel pivot axis though, which in real life gives it a tendency to align straight even when it is unlocked - as long as there is weight on the tail wheel.

I have a sneaking suspicion this is not modelled - pending further testing. There also seems to be no modelling of the directional control provided by the propwash as of yet.

The difficulty of keeping things straight on take-off and landing is plausible to me. However, the difficulty to get things back under control once you allow it all to go pear-shaped is probably WIP. If it was really this easy to wreck aircraft on the ground, the pilot's manuals would have page upon page with warnings and advice and there'd be no end to the journal footage and written accounts of aircraft going off the runways.

The Mustang was considered benign as compared to the narrow-track Spit and Bf109, so imagine what they'd be in a crosswind relative to what we are seeing? I've never seen landing accidents listed as a serious cause of attrition in the war-time Mustang fleet - unlike for the aforementioned two aircraft - and pilots were sent to crud weather in Europe with relatively few hours on-type.

As for handling qualities checks by real-life P51 pilots, real-life P51 pilots will all be very, very experienced aviators. They're not likely to react much to things being off once you get slightly out of shape as they'll never enter that part of the envelope. Compare it with the situation when the Swedish Saab J29 first entered service. Literally half the first classes of students were killed as they spun in on short final - yet this lethal trait of the aircraft had never been noticed during flight testing. Why? Simple. The snap roll problems occurred when you flew the aircraft with less-than-perfect coordination, which students are prone to but experienced factory and air force test pilots will simply never do unless specifically asked to.

I reiterate - I consider this to be WIP and expect to see things change back and forth as the beta period progresses, so I try to take it at face value and not get too upset as of yet.

Thats fine effte, I was not upset, just having trouble with the release of the tailwheel. As for now I manage the taxiing with short break on wheels to make sharper turns without stick forward. It works somewhat but users with the pedals have a huge advantage. I will also check the progress on these things in coming betas. Thanks for posting! :D

(HJ)

You could just bind left and right brakes (not the axis) to left and right on a coolie hat e.g.

Repeatedly tapping those in a corner improves turning radius a lot.

You could just bind left and right brakes (not the axis) to left and right on a coolie hat e.g.

Repeatedly tapping those in a corner improves turning radius a lot.

Yes thats what I did ;)

Does anyone else have a hard time understanding what the fuh effte is trying to say ;)

Does anyone else have a hard time understanding what the fuh effte is trying to say ;)

It's all between the lines :P

G-Lock91,

perhaps you could be a little more specific with your question and I'll be happy to clarify what you are trying to understand. :)

I could explain every term and concept from the ground up in every post, but god knows that my posts are long enough to begin with, and I doubt the more technical matters will keep the interest of more than a few forum participants. There's also the question of having limited time to spend on the forum. Hence, I elect to write as I would among peers and rely on people asking if they are unclear about something they are interested in when googling the terms does not provide the answer. Some, strangely, call it semantics but I call it educational and time-effective communication. I think this crowd is rather well-educated, should not be underestimated and can handle a lot of jargon. :thumbup:

Cheers,

Fred

It's all between the lines :P

Everything is between the lines - except when you are thinking out of the box... ;)

G-Lock91,

perhaps you could be a little more specific with your question and I'll be happy to clarify what you are trying to understand. :)

 

I could explain every term and concept from the ground up in every post, but god knows that my posts are long enough to begin with, and I doubt the more technical matters will keep the interest of more than a few forum participants. There's also the question of having limited time to spend on the forum. Hence, I elect to write as I would among peers and rely on people asking if they are unclear about something they are interested in when googling the terms does not provide the answer. Some, strangely, call it semantics but I call it educational and time-effective communication. I think this crowd is rather well-educated, should not be underestimated and can handle a lot of jargon. :thumbup:

 

Cheers,

Fred

Well that's the problem, you're bein pretty technical and only those "few" that are as educated in this as you are able to understand what you're saying :) Not trying to be rude, simply asking that ya dumb down what it is you are actually saying.. for those of us that aren't as fortunate:thumbup: Seems like you know a lot of how this stuff works; would nice to take some of it and apply it without the use of a flight dictionary.

I would have to agree that much (especially propwash) does not yet appear to be modelled. That's the only thing that would explain the stick forward controllability of the plane. I've never flown a high performance classic fighter but I have flown some short coupled relatively unstable tailwheel planes. All responded quickly and predictably to either bursts of power or a small amount of differential braking.

I agree that prop wash might not be fully modeled. Deflecting the rudder with significant power on the ground seems to have very little effect, and steering authority improves dramatically after you pick up 15-20 mph (tail wheel locked). A lack of a proper caster model would definitely explain the behavior when the wheel is unlocked. There should be a definite tendency to stay centered if you release the lock while rolling in a straight line. It would wobble a little, of course, but it shouldn't go flipping completely around the way it does now. I'll do some testing later on and we can compare notes.

@GLock:

I've spent about an hour trying to write this post in a way that won't cause friction on the forums, but I'm not sure if I've succeeded. Please understand that I'm doing my best to avoid being offensive.

The essence of the problem is that it is exceedingly difficult and time consuming to try to write this material in a way that everyone can understand. We're talking about years or even decades of experience and training. Fortunate or not, there's no way we can impart that knowledge in the span of a few forum posts. In many cases, it's not possible to talk about a subject without both parties having an understanding of the underlying material. You simply have to put in the time, and that involves asking questions when you don't understand something. We're not hateful people, and we don't look down on you for not being able to understand what we're saying. Just like school teachers, we need you to tell us what you're having difficulty with so that we can find the applicable knowledge in the giant pool of goo that we carry around in our heads. :helpsmilie:

Here are descriptions of some terms that stand out to me in effte's post (hopefully with the right definitions for the context):

Caster - (I had to actually go look this up, as I got caster and camber confused for a while). This is a design concept that causes a wheel to return to center because of friction forces while rolling. See http://en.wikipedia.org/wiki/Caster_angle for a basic discussion. Effte actually described this in his post, although it may have been an edit.

Prop wash - The wind coming from the propeller that flies back over the aircraft, causing flow over the wings and control surfaces. Prop wash can produce enough airflow over the rudder and elevator to allow you to swing the tail left and right, or even raise it above the ground.

Track - More properly called track width. This is the distance between a pair of wheels, perpendicular to the direction of motion. Wider track widths provide a more stable platform, with less tendency to tip over in a turn. You'll notice that race cars all tend to be very low to the ground, with an extremely wide track width. This makes them resistant to tipping over, and it also allows them to pull 1G or more in a turn. A common high performance road car, by comparison, is only able to achieve about 0.8G.

Hopefully that helps clear up any confusion about terms in effte's post. Remember that these are also just very basic descriptions of what these terms are. When I think about all this stuff, I'm actually picturing the physics in my mind, imagining flow fields for the discussion on prop wash, and the way friction and suspension geometry affect a tire in motion.

There's a good example of another use of a term that I might need to define.

Flow field - A mathematical/visual model describing the way a liquid (air acts like a liquid) moves around a surface. Here's a relevant Wiki article on vector fields.

From this post alone, you can see how terms and concepts compound on each other. Having us drill all the way down to the most basic level isn't practical, especially when you might already know some of the material. Take a look at that article on vector fields. There's a bunch of additional terms in there that you would have to know to develop a full understanding of the concept. How far do I drill down? It's much better to start at the top and work down to concepts that you understand than it is to try to write at a very basic level. That saves both parties a lot of time.

We'll do our best to provide a simple description when we can, like I did for the terms above, but if there's no way to get into it without dropping into details, you're going to have to bare with us and keep asking more questions.

(And yes, going all the way down to vector fields is probably more than pilots receive in flight training. I'm just fumbling for a way to describe the nature of the problem.)