Some kind of autopilot?

[BigDuke6ixx]

Thats the point once Airborne there isnt a difference unless you the pilot make one using the controls. Definitely the last post here.

 

Sent from my SM-G955U using Tapatalk

 

There you go guys, this fella is an ex military and current 777 pilot and your ignorance has seen him off. Well done, you should all be proud.

 

But explain to me how someone with his qualification can be, according to you, so completely wrong? I mean, he's go 10,000hrs of real flying yet you all know more? Take a step back and think, for flip's sake!

[BigDuke6ixx]

That would have been me. ;)

 

My point being that if weathervaning exists, it should be very simple for the proponents to show it, instead of keeping on going in circles. Let's hope shagrat or someone else comes up with a track or a video showing exactly what they mean. After arguing for 100 posts, they should be able to show it within 10 minutes, and I'd really like to see this effect that I wasn't able to produce in insanely strong crosswinds. :thumbup:

 

 

I video of them spouting the aviation equivalent of flat Earth theorem would probably make my eyes and ears bleed.

[BigDuke6ixx]

The engines push the aircraft forward, the crosswind pushes it sideways. The result is a diagonal flight path over the ground. If we ignore the engines and the forward thrust, we would see the aircraft move with the speed of the wind in the direction of the wind - no matter the attitude of the aircraft. It moves with the air mass - think of hot air balloons.

 

Now the dreaded weathervane effectl ... the above is true during regular flight. But in order to move with the wind, the aircraft has to be accellerated in that direction first. During take off, there is no lateral movement - due to the wheels on the ground (+ nosewheel steering, if you insist). The moment the wheels come free off the ground, the cross wind begins to accellerate the aircraft sideways. And during this period, the cross wind affects different parts of the aircraft differently - due to wind resistance/drag of the fuselage and due to inertia of the aircraft.

 

And this is where some wheatervane effect should be observable!

 

20 kts crosswind, the aircraft unsticks. 20 kts wind act now on a big tail fin and on a small nose. The aircraft resists to move due to it's inertia, but the wind forces on the tail are greater than the forces on the nose. What will the airframe do now?

 

The transient effects at rotation, from turbulence and as climbing through the wind gradient have been explained to them already, but they seem to be stuck on transmit. I mean, I've seen a house fly, I've even seen a horse fly but I ain't ever seen.... :noexpression:

[shagrat]

(...)The moment the wheels come free off the ground, the cross wind begins to accellerate the aircraft sideways. And during this period, the cross wind affects different parts of the aircraft differently - due to wind resistance/drag of the fuselage and due to inertia of the aircraft.

 

And this is where some wheatervane effect should be observable!

 

20 kts crosswind, the aircraft unsticks. 20 kts wind act now on a big tail fin and on a small nose. The aircraft resists to move due to it's inertia, but the wind forces on the tail are greater than the forces on the nose. What will the airframe do now?

 

Pretty much this...

[WindyTX]

Ok I know I said I would'nt post again but if you go back to one of my Original posts I said the only time you feel a "Weather vane"is on take-off.

 

NEVER IN FLIGHT

[BigDuke6ixx]

Pretty much this...

 

 

But according to you these forces continue acting on the plane for the duration of its encounter with a crosswind. Once up and flying with the inertia moments long gone, the wind does NOT continue to try to rotate the plane. Anyway, record a track and make a video or you have only words and no proof.

 

Before you waste your time, you might want to review the track posted a few pages back, that actually proves you are completely wrong.

 

And please stop quoting out of context sentences as proof that others agree with you..

[BSS_Sniper]

I'm guessing you've never flown a real pane and don't hold a pilot's license.

 

https://en.wikipedia.org/wiki/Weathervane_effect

 

 

 

I do and hold an ATP. I have no idea where you are getting your information but you're wrong. Aircraft do weather vane into the wind in flight. I see it all the time. The magnetic heading is almost always different than the ground track.

[shagrat]

But according to you these forces continue acting on the plane for the duration of its encounter with a crosswind. Once up and flying with the inertia moments long gone, the wind does NOT continue to try to rotate the plane. Anyway, record a track and make a video or you have only words and no proof.

 

Before you waste your time, you might want to review the track posted a few pages back, that actually proves you are completely wrong.

 

And please stop quoting out of context sentences as proof that others agree with you..

The plane has a mass, I guess we can agree to that?

 

Mass has inertia (mind weight is the gravitational force pulling the mass down, inertia is the force/energy required to accelerate the mass in any direction).

 

Now whenever you change the direction or speed of the mass inertia needs to be "overcome".

At this point it would make a pivot point around which the mass will start spinning as long as the force is applied asymmetrical to the mass...

That is basically what a pilot does when applying control inputs to make a turn, he uses the energy of the air streaming over foils and puts (a) control surface(s) in the way to generate energy and turn the plane around its CoG and thus change the thrust vector until inertia is overcome again.

The same principle laws of physics must apply when it is a wind blowing at a control surface, it is the reversion of the same formula... I'll try make a track.

 

It should be noticeable shortly after take off (what I said all the time), because your flight vector is still aligned with the runway, wind is pushing your plane, and inertia should take a moment or two to be overcome and drift the plane sideways.

If you don't counter at this point with a bit of rudder, aileron or asymmetrical thrust, it should by all means veer the nose a little upwind.

 

As soon as the crosswind has overcome inertia it just moves the whole plane, until you change course with control inputs.

Of course you wouldn't notice, the effect when you turn, because you dynamically adjust the input to get the flight vector where you want it. Yet, the effect is still there, but hidden in the greater forces of your control inputs.

 

I hope I make sense here, I really try.

[shagrat]

Ok I know I said I would'nt post again but if you go back to one of my Original posts I said the only time you feel a "Weather vane"is on take-off.

 

NEVER IN FLIGHT

So I guess we mean the same after all, the moment after the wheels lift off the ground.

 

It isn't as pronounced, as when the wheels still act as an anchor, but the nose does veer a bit into the wind until either the wind has overcome inertia and pushes the whole plane sideways, or you counter with control inputs...

 

At least that is what it should do according to laws of physics.

 

Now, bear with me, i'll try if I can get this on a track with the adapted "Instant Action Take Off mission" from 2.1.1 Nevada...

 

P.S. I really don't want to piss anybody off, and sorry BigDuke6ixx for the nasty comment, I was a bit unnerved and that was unfair.

Edited June 27, 2017 by shagrat

[BigDuke6ixx]

I do and hold an ATP. I have no idea where you are getting your information but you're wrong. Aircraft do weather vane into the wind in flight. I see it all the time. The magnetic heading is almost always different than the ground track.

 

Only because you have change the heading to maintain the correct groundtrack. It's being claimed that you need to cross control to maintain this heading because the wind is trying to pivot the plane all the time while it is being influenced by a crosswind. They are claiming that a plane in flight in a crosswind is having its tail pushed around all the time. Utter rubbish.

 

Apparently this is how you fly in a crosswind:

 

This is what the control inputs should roughly look like to fly that course...

 

If you keep the aileron and rudder neutral, what happens?

 

 

Note the sustained cross control. Remember, he's talking about in free flight, cross country here, not during landing and takeoff. See windy's replies.

Edited June 27, 2017 by BigDuke6ixx

[BigDuke6ixx]

The plane has a mass, I guess we can agree to that?

 

Mass has inertia (mind weight is the gravitational force pulling the mass down, inertia is the force/energy required to accelerate the mass in any direction).

 

Now whenever you change the direction or speed of the mass inertia needs to be "overcome".

At this point it would make a pivot point around which the mass will start spinning as long as the force is applied asymmetrical to the mass...

That is basically what a pilot does when applying control inputs to make a turn, he uses the energy of the air streaming over foils and puts (a) control surface(s) in the way to generate energy and turn the plane around its CoG and thus change the thrust vector until inertia is overcome again.

The same principle laws of physics must apply when it is a wind blowing at a control surface, it is the reversion of the same formula... I'll try make a track.

 

 

Look, for the upteenth time, the plane will only feel gusts in an aerodynamic sense and those are only momentary in their effects and will tend to be cancelled out over time by lulls. You simple do not get a continuous aerodynamic effect from a crosswind because all the crosswind is doing is pushing the plane in the direction it's going at the speed it's going at. There is no need at all to cross control unless taking off or landing (and maybe to lose height in a hurry without gaining too much speed but that's another topic) because the tail isn't being pushed harder than the nose and there is no continuous force trying to rotate the plane!.

Edited June 27, 2017 by BigDuke6ixx

[shagrat]

Here is the track file.

Take Off Instant Action only adjustment is to strip the loadout in the ME.

 

Winds: at 2000ft MSL - 6m/s from 257° (so a light crosswind with tailwind component)

 

Note please, that I have overcontrolled a tiny bit right after lift off, so the initial heading on the HSI is more 029 instead of 030. I concentrated on keeping aileron, elevator and rudder totally neutral. No trim before or after T/O.

 

At the end of the track we fly almost a heading of 021 with virtually no control input after lift off. :noexpression:

 

A-10C_clean_TO.trk

 

Here is the TacView if the trk does not work...

Tacview-20170627-220307-DCS.zip

Edited June 27, 2017 by shagrat

[Frederf]

The engines push the aircraft forward, the crosswind pushes it sideways. The result is a diagonal flight path over the ground. If we ignore the engines and the forward thrust, we would see the aircraft move with the speed of the wind in the direction of the wind - no matter the attitude of the aircraft. It moves with the air mass - think of hot air balloons.

 

Now the dreaded weathervane effectl ... the above is true during regular flight. But in order to move with the wind, the aircraft has to be accellerated in that direction first. During take off, there is no lateral movement - due to the wheels on the ground (+ nosewheel steering, if you insist). The moment the wheels come free off the ground, the cross wind begins to accellerate the aircraft sideways. And during this period, the cross wind affects different parts of the aircraft differently - due to wind resistance/drag of the fuselage and due to inertia of the aircraft.

 

And this is where some wheatervane effect should be observable!

 

20 kts crosswind, the aircraft unsticks. 20 kts wind act now on a big tail fin and on a small nose. The aircraft resists to move due to it's inertia, but the wind forces on the tail are greater than the forces on the nose. What will the airframe do now?

 

The answer to the bolded question is that the airplane will do both at the same time. The airplane, at the moment that it becomes mechanically decoupled from the ground, is not crabbed into the wind and there is a net lateral component of force (wind). The airplane is accelerated laterally.

 

At the same time there is a yaw torque due to the beta angle of relative air flow which rotates the airplane into the wind. As the airplane is rotated into the wind the thrust from the engine angled relative to the direction of motion has a lateral component in the opposite direction of drift.

 

After some time the airplane reaches a steady state condition where the beta angle is zero and there is no lateral net force. Provided there are no control inputs (imagine the airplane has no control surfaces) the ground track from the runway roll is the same course but offset laterally downwind. The airplane will not take on a new course.

[Yurgon]

Here is the track file.

 

Come on, is this a joke?

 

First, what do take-offs have to do with anything? I think we're all pretty clear on the concept of weathervaning aircraft on takeoff. You made it absolutely, totally, abundantly clear on numerous occasions that this effect also takes place in level flight. I don't need to see you take off, I need you to show the effect in level flight.

 

Second, in the playback there are some very pronounced left roll inputs on the stick X axis. Of course the aircraft will end up rolling left if that's what you command. I replayed your track a couple of times, then during one replay I took control right away and unintentionally gave some right roll input during take-off before letting the stick go back to center, and I didn't counter said roll input. Guess what? The aircraft "weathervaned" - against the wind, and I ended up heading 040ish.

 

Please tell me that's not the best you can come up with, because the only thing it shows is what you've been claiming all along: providing input, even if it's small and unintended, will change the aircraft's flight path. Well duh.

[David OC]

You guys...LOL

 

This weathercocking / weathervaning is starting to do my head in, lol :)

 

This might help clear some of this up....:(

 

"A weathervane, is made to be stable when pointed into the wind. This is generally done by making sure that more "area" is placed downstream of the "pivot" than upstream."

 

The difference between airplanes and weathervanes

 

"Now one of the diferences between wind vanes and airplanes is that airplanes can move with 6 degrees of freedom (fore and aft, left and right, up and down, as well as rolling, pitching, and yawing). This means that we need to be concerned with much more complicated kinds of motions to assess the stability. Still, we can do a pretty good job by considering just the pitching (nose-up or nose-down rotation) and yawing (nose left or right rotation) motions. We can determine (as an approximation) whether an airplane will be stable by imagining a weathervane that looks like the airplane in top view (as shown above) to assess its pitch stability, or in side view (so that it can yaw left or right) to assess its yaw stability. Now, of course, the stability of the weathervane depends entirely on where we put the pivot. The same is true of airplanes. Although they don't have pivots, the motion of a free body can be nicely decomposed into translational motions and rotations about the body's center of gravity, or balance point. So for our purposes, we'll think of the airplane as free to pivot about its center of gravity."

How to make a stable airplane

 

"So, to make a stable airplane all we have to do is to make sure that the pivot (center of gravity -- or c.g. for short) is sufficiently far forward. In particular, it must be forward of the neutral point. For simple wings, we can make a very rough estimate the location of the neutral point by estimating the center of area of the airplane's surfaces (in side view for estimating yaw stability or top view for pitch). There are much more accurate ways of estimating the neutral point, but this is a start.

 

So, its easy to make a stable airplane: just put enough weight on the nose. This is completely correct, but putting too much weight on the nose leads to poor performance and difficulty making the airplane trim, as discussed in the next section."

 

http://aero.stanford.edu/e1/stability.html

 

Weathercock stability

 

"If an aeroplane is yawed due to a gust of wind, it’s ability to automatically return to it’s previous heading depends on the area behind it’s centre of gravity to produce a restoring force. The "fuselage ahead of the centre of gravity" will tend to produce a force to destabilise the aircraft."

 

http://www.propdesigner.co.uk/html/weathercock_stability.html

 

 

So to my understanding, there can be a force "Wind" trying to turn the nose of an aircaft into it, the plane tries to stops this from happening because of where the center of gravity is and the rear tail fin size (Think Dart or Arrow from a crossbow). The more speed the aircraft has the less affect the crosswind has on it. As seen when working out wind correction angle [WCA] https://www.recreationalflying.com/tutorials/navigation/wind.html

 

 

So the aircraft does use a weathervane or weathercocking affect for it's own directional stability control using it's own man made wind of 150 knots etc.

 

20 knot wind @ 30 degrees offset, will have little affect against where this 150 knot Dart is pointing. It will have an affect on the side slip, while on its way to the target bullseye.

 

 

 

 

.

Edited June 28, 2017 by David OC

[BigDuke6ixx]

 

 

So the aircraft does use a weathervane or weathercocking affect for it's own directional stability control using it's own man made wind of 150 knots etc.

 

20 knot wind @ 30 degrees offset, will have little affect against where this 150 knot Dart is pointing. It will have an affect on the side slip, while on its way to the target bullseye.

 

 

 

 

.

 

That's it.

[David OC]

Another good example of how to say it.

 

"If the boat is moving through the water at 10 knots, it doesn't matter to the boat whether its going upstream, downstream, or across the river. It is moving through the water at 10 knots. Now if the water is also moving at 5 knots, then the boat is effectively moving 5 knots upstream and 15 knots downstream COMPARED TO THE STATIONARY LAND. To the boat it will still be 10 knots.

 

Same thing for airplanes. The speed of the plane through the air stays the same, regardless of the wind. But compared to the ground, it will be moving faster or slower due to the entire air mass moving.

 

Much the same was as you are really going thousands of miles an hour right now - around the sun that is."

http://www.airliners.net/forum/viewtopic.php?t=752331

 

 

The water current doesnt affect the boats speed or direction when cruising around, in the relation to the water (Mass) it's cruising around on. It's movement of (Drift) can only be seen from land or when anchored to land. If you were floating around in the ocean, and there was no land, you would have know idea you were drifting at all. Just like us, right this very minute, are cruising at a speed of 18.5 miles/sec around the sun.

 

 

.

Edited June 28, 2017 by David OC

[NeilWillis]

Yes, if you are part of a moving mass of air or water, you will make lee way or drift over a fixed point on the ground or ocean floor.

 

An aircraft will have a tendency to yaw when flying into a cross wind if there is an imbalance of side forces due to the shape of the airframe. In other words, the tail fin will create more wind resistance than the fuselage, and so the nose will usually tend to turn into the wind.

 

A crosswind will manifest itself in the HUD of an A-10C by the flight path marker and ladder being offset. Placing the flight path marker over your chosen direction of travel will offset the nose of the aircraft to make the aircraft fly on the chosen bearing.

 

It is when you are close to the ground that you'll notice the lee way drift most clearly.

[shagrat]

Come on, is this a joke?

 

First, what do take-offs have to do with anything? I think we're all pretty clear on the concept of weathervaning aircraft on takeoff. You made it absolutely, totally, abundantly clear on numerous occasions that this effect also takes place in level flight. I don't need to see you take off, I need you to show the effect in level flight.

 

Second, in the playback there are some very pronounced left roll inputs on the stick X axis. Of course the aircraft will end up rolling left if that's what you command. I replayed your track a couple of times, then during one replay I took control right away and unintentionally gave some right roll input during take-off before letting the stick go back to center, and I didn't counter said roll input. Guess what? The aircraft "weathervaned" - against the wind, and I ended up heading 040ish.

 

Please tell me that's not the best you can come up with, because the only thing it shows is what you've been claiming all along: providing input, even if it's small and unintended, will change the aircraft's flight path. Well duh.

I made it very clear from the start, that we talk about the point after lift off (no wheels acting as an anchor), as that was what understood from the original post.

Second, I am also pretty sure the effect will happen in flight as well as soon as a course change happens, only that you wouldn't notice, as you are controlling the plane anyway.

 

And there were numerous people telling "if there is no wheels on the ground as a pivot point, the plane does not weathervane"...

 

https://forums.eagle.ru/showthread.php?p=3178407

 

https://forums.eagle.ru/showthread.php?p=3178478

 

I was pretty sure when I tested this two days ago it did turn its nose.

I can try if flying a level nose attitude after take off changes it...

Edited June 28, 2017 by shagrat

[BigDuke6ixx]

Yes, if you are part of a moving mass of air or water, you will make lee way or drift over a fixed point on the ground or ocean floor.

 

An aircraft will have a tendency to yaw when flying into a cross wind if there is an imbalance of side forces due to the shape of the airframe. In other words, the tail fin will create more wind resistance than the fuselage, and so the nose will usually tend to turn into the wind.

 

A crosswind will manifest itself in the HUD of an A-10C by the flight path marker and ladder being offset. Placing the flight path marker over your chosen direction of travel will offset the nose of the aircraft to make the aircraft fly on the chosen bearing.

 

It is when you are close to the ground that you'll notice the lee way drift most clearly.

 

A plane flying in crosswind will not yaw in relation to the air mass it is flying in! It will appear to crab in relation to the ground though. You should stop talking off the top of your head and go do some research on the subject.

[BigDuke6ixx]

I made it very clear from the start, that we talk about the point after lift off (no wheels acting as an anchor), as that was what understood from the original post.

Second, I am also pretty sure the effect will happen in flight as well as soon as a course change happens, only that you wouldn't notice, as you are controlling the plane anyway.

 

And there were numerous people telling "if there is no wheels on the ground as a pivot point, the plane does not weathervane"...

 

https://forums.eagle.ru/showthread.php?p=3178407

 

https://forums.eagle.ru/showthread.php?p=3178478

 

I was pretty sure when I tested this two days ago it did turn its nose.

I can try if flying a level nose attitude after take off changes it...

 

Yes or no: does a plane that wants to hold a north heading, flying with a crosswind from the north west, have to be cross controlled to hold its north heading?

 

i say no, no sideslip is required.

[Razor18]

Heading will remain north, but ground track will be northeast, sou you will end up east of the point that was north of you, when you switched (north) heading hold ON.

[BigDuke6ixx]

Heading will remain north, but ground track will be northeast, sou you will end up east of the point that was north of you, when you switched (north) heading hold ON.

 

Yes, but not an answer to my question.

[NeilWillis]

A plane flying in crosswind will not yaw in relation to the air mass it is flying in! It will appear to crab in relation to the ground though. You should stop talking off the top of your head and go do some research on the subject.

 

In a crosswind, it isn't travelling with a mass of air, it is crossing it as it moves relative to the aircraft's flight path. Any force applied to a body against which it is not symmetrically applied will always induce a rotational moment.

 

Go do some basic physics instead of making accusations.

[BigDuke6ixx]

In a crosswind, it isn't travelling with a mass of air, it is crossing it as it moves relative to the aircraft's flight path. Any force applied to a body against which it is not symmetrically applied will always induce a rotational moment.

 

Go do some basic physics instead of making accusations.

 

Not correct. The only thing affected by the crosswind is groundspeed and ground track. The fact the air mass is moving in relation to the ground is only a navigational issue and the aerodynamics of how the reletive wind (what we measure as airspeed) passes over the plane remain unaffected. The crosswind does NOT push harder against the tail than the nose in flight, like it does on the ground.

 

I'll bet my house on that. How sure are you?