Some kind of autopilot?

[David OC]

This is the aircraft trimmed state, the ball was still in the center.

 

10,000 feet, 20 Knot wind @ 45 degrees, video coming.

 

No weapons on wings (Clean) 70% fuel.

 

3 degrees of AOS

2.5 degrees AOA

 

This is called AOS Angle of side slip

 

Wind Navigation (side slip)

 

What are we seeing here then?

 

Yo-Yo would be sitting back laughing his ass off at all of us, you know that right.:)

 

VxL2NsCizE4

 

 

 

This is the best way to think about all this from an aerospace engineer.

 

Eli Cohen, BS from MIT, MS from Purdue University in aerospace engineer. Aircraft Designer.

 

"Yaw is typically just the heading of the aircraft on the compass.

 

Sideslip is the "relative angle" between the freestream flow and the aircraft "yaw vector"

(to simplify it somewhat). Sideslip is the analog of angle of attack, but for yaw instead of pitch."

 

It is the same as AOA, called AOS, angle of sideslip

 

 

http://www.flightlab.net/Flightlab.net/Download_Course_Notes_files/4_LateralDirectional%232BA14D.pdf

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Edited June 29, 2017 by David OC

[mvsgas]

Guys, obviously you are free to continue this rhetoric, but we all know that internet forums will not change no ones opinions and this conversation was death 200+ post ago...why do I even bother, you all will just ignore this and carry on...I wonder how old is the kid that said:"I like turtles" now? Every time I see that video reminds of Crush from Finding Nemo... that was a funny movie...anyway. You guys where arguing about what again?

Edited June 29, 2017 by mvsgas

[Donnerblase]

You got it. And fair play for being man enough to hold your hand up.

 

You have to be able to admit and correct mistakes. If everybody just stays his ground on opinions without facts, there can be no progress. Also, I really should know this stuff, but somehow got the wrong impression about what we are talking about here...

 

I am not talking about sideslip (that is someone else). I am not talking about a trimmed state, either.

 

The plane is clean (no loadout other than gun ammo and at max fuel). I do NOT control, or trim the plane the WHOLE track.

 

What the track shows is the fact that while the aircraft is settled after 3 seconds its ground track (TRK) is more or less north (with a little oscillation of 0.4°).

While it follows this ground track for quite a while over 40 seconds minimum it yaws the nose (HDG) left into the wind by at least 3° (actually 3-4° but the oscillation may swing the nose by 0.5-0.7° so lets subtract 1° for good measure).

 

Only after one minute of flight the plane starts really drifting and subsequently rolling right, where I am sure the exponential increase is related to the roll, so lets ignore the later part of the track.

 

According to the discussion here the plane should not(!) turn its nose, while in the air, as it is moving with the relative wind (thrust vector and crosswind combined).

 

So what is pushing the nose to the left by 3° ?

 

EDIT Keep in mind that the plane starts mid-air, with its inertia not overcome by the crosswind, yet. Thus it isn't travelling with the airmass, when the track begins!

 

To really be representative, one would have to know the logic ED has implemented for trimming in airstarts. I believe you when you say that you didn't move anything, but you have to consider the vast array of variables that have to be taken into account here.

[Pikey]

Let this thread end. For the love of all that is good. The death was where someone said it had gone off topic after they moved it to a different topic themselves. Watching semantics and different argument positions from different understanding levels with terminology and wiki copy/pastes, along with different experiences in flying, then comparing them to a simulation. It's simply not worth your collective lives to waste time here.

 

The OP must be laughing at you all.

[David OC]

Let this thread end. For the love of all that is good. The death was where someone said it had gone off topic after they moved it to a different topic themselves. Watching semantics and different argument positions from different understanding levels with terminology and wiki copy/pastes, along with different experiences in flying, then comparing them to a simulation. It's simply not worth your collective lives to waste time here.

 

The OP must be laughing at you all.

 

Still good to just get right, right. LOL:)

 

 

For us simmers, just look at the flight path vector in your HUD, if this is centered, then there is no Angle of side slip, to your aircraft direction .

 

Simple way to finish this really, go up in any aircraft with a HUD and watch the flight path vector when in different wind directions at different speeds, you and the wind.:thumbup:

 

 

.

[BigDuke6ixx]

Still good to just get right, right. LOL:)

 

 

For us simmers, just look at the flight path vector in your HUD, if this is centered, then there is no Angle of side slip, to your aircraft direction .

 

Simple way to finish this really, go up in any aircraft with a HUD and watch the flight path vector when in different wind directions at different speeds, you and the wind.:thumbup:

 

 

.

 

There is a bit of equipment in the A10 that continually works out the wind. It does this by combining information from other instruments and displays crosswinds via a displaced hud. There is no side slip or uncommanded yaw produced by a steady crosswind, the force of the relative wind and directional stability prevent this draggy state from developing on its own. Only control input and the transient effects from gusts and turbulence can put the aircraft in this state. Your evidence is wrong, your observations are woeful and your source material is either irrelevant or you have misinterpreted it completely.

 

You should stop being a dick and just hold your hand up.

Edited June 29, 2017 by BigDuke6ixx

[David OC]

There is a bit of equipment in the A10 that continually works out the wind. It does this by combining information from other instruments and displays crosswinds via a displaced hud. There is no side slip or uncommanded yaw produced by a steady crosswind, the force of the relative wind and directional stability prevent this draggy state from developing on its own. Only control input and the transient effects from gusts and turbulence can put the aircraft in this state. Your evidence is wrong, your observations are woeful and your source material is either irrelevant or you have misinterpreted it completely.

 

You should stop being a dick and just hold your hand up.

 

LOL, nice

 

Your just Trolling now.

 

Flight path vector is the reference path over the ground, why is it not centered then in the HUD then, mmm. :music_whistling:

 

It's the same "Flight path vector" you use when crabbing the aircraft in when landing. I.E Your facing into a crosswind, the Flight path vector is on the runway.

 

If what your saying is true the "Flight path vector" would always end up in the center of the HUD.

 

The only time I saw this, is when facing straight into the wind.

 

VxL2NsCizE4

 

.

Edited June 29, 2017 by David OC

[shagrat]

The is no yaw to the relative wind once direction stability has been reached.

Agreed, when the directonal stability is reached, it doesn't yaw further, that is why it holds the 3° angle after after a while and starts drifting. As we create an artificial situation with the mid-air spawn it behaves the same as shortly after lift off. Inertia pushing forward, crosswind creates a reactive force, asymmetry of surface yaws the nose, until stable and inertia is overcome. Now the plane is stable (apart from the roll oscillation) and drifts with the wind as expected, until somebody applies controls.

[BigDuke6ixx]

Agreed, when the directonal stability is reached, it doesn't yaw further, that is why it holds the 3° angle after after a while and starts drifting. As we create an artificial situation with the mid-air spawn it behaves the same as shortly after lift off. Inertia pushing forward, crosswind creates a reactive force, asymmetry of surface yaws the nose, until stable and inertia is overcome. Now the plane is stable (apart from the roll oscillation) and drifts with the wind as expected, until somebody applies controls.

 

Well then, doubling the wind strength should double this angle according to your new theory. Anyway, it doesn't work like that because your theory is completely wrong.

[David OC]

Worked for me at 40 knots up from 20 knots at the 45 degree wind offset.

 

6 degrees Angle of Slip

 

 

20 Knots @ 45 degrees, 3 degrees Angle of Slip

 

 

 

HUD showing 40 knots of wind at the 45 degree wind offset

 

.

Edited June 29, 2017 by David OC

[Weta43]

shagrat is agreeing with you bigduke6ixx.

 

The airspawn effectively starts the plane 'out of equilibrium' and for a moment or two (about as long as it takes to return to stable flight after kicking the rudder), the plane is catching up with the mass of air, and is indeed 'weathervaning'.

 

Once the aircraft 'catches up' with the airmass,

the plane is stable ... and drifts with the wind as expected, until somebody applies controls.

 

Doubling the windspeed will still result in the plane flying straight into the airmass, but the angle relative to the ground vector will increase.

 

A string on the window would still run straight up the windscreen, but the TVV will be deflected more.

[BigDuke6ixx]

Worked for me at 40 knots up from 20 knots at the 45 degree wind offset.

 

6 degrees Angle of Slip

 

 

20 Knots @ 45 degrees, 3 degrees Angle of Slip

 

 

.

 

That's just the stronger crosswind increasing the easterly drift and nothing to do with a crosswind wind induced slip angle to the relative wind. The crosswind is bowing the tail around it's just causing the plane to drift.

Edited June 30, 2017 by BigDuke6ixx

[Weta43]

You David OC are conflating total velocity vector relative to the earth, with movement relative to the airmass.

 

Of course if the air is moving down and to the right relative to the ground, an object moving through it will have that velocity vector added to its movement relative to the ground, just as a balloon with no movement relative to the air would.

It doesn't mean in any sense that the aircraft is 'side-slipping' relative to the airmass.

[BigDuke6ixx]

shagrat is agreeing with you bigduke6ixx.

 

The airspawn effectively starts the plane 'out of equilibrium' and for a moment or two (about as long as it takes to return to stable flight after kicking the rudder), the plane is catching up with the mass of air, and is indeed 'weathervaning'.

 

Once the aircraft 'catches up' with the airmass,

the plane is stable ... and drifts with the wind as expected, until somebody applies controls.

 

Doubling the windspeed will still result in the plane flying straight into the airmass, but the angle relative to the ground vector will increase.

 

A string on the window would still run straight up the windscreen, but the TVV will be deflected more.

 

 

No, he's claiming that the crosswind component is pushing harder against the tail and causing the nose to yaw in relation to the relative wind. Obviously that is not happening and he is mistaken.

Edited June 29, 2017 by BigDuke6ixx

[some1]

HUD showing 40 knots of wind at the 45 degree wind offset

 

.

 

The hud Flight Path Marker shows the sum of the drift due to wind and slip in the lateral plane, in the same way it shows the sum of AoA and angle of climb/descent in the vertical plane. That doesn't mean there's any slip on your picture, there's only wind drift.

 

In other words, the FPM shows your movemenet relative to the ground, not relative to the air around you.

[BigDuke6ixx]

:smilewink:

You David OC are conflating total velocity vector relative to the earth, with movement relative to the airmass.

 

Of course if the air is moving down and to the right relative to the ground, an object moving through it will have that velocity vector added to its movement relative to the ground, just as a balloon with no movement relative to the air would.

It doesn't mean in any sense that the aircraft is 'side-slipping' relative to the airmass.

 

This is the whole essence of their claim.

[Weta43]

Originally maybe. Now he's saying to you the effect he originally described only occurs as a transitory phenomena caused by the fact the aircraft artificially spawns in mid air, and only occurs until the plane reaches an equilibrium.

He even says he agrees with you:

Agreed, when the directonal stability is reached, it doesn't yaw . (& he say's 'further', but I read this as 'anymore')

 

the plane is stable ... and drifts with the wind as expected

[David OC]

You David OC are conflating total velocity vector relative to the earth, with movement relative to the airmass.

 

Of course if the air is moving down and to the right relative to the ground, an object moving through it will have that velocity vector added to its movement relative to the ground, just as a balloon with no movement relative to the air would.

It doesn't mean in any sense that the aircraft is 'side-slipping' relative to the airmass.

 

Just testing how this aerospace engineer explains Side slip angle, not Side slip navigation across the ground.

 

 

Eli Cohen, BS from MIT, MS from Purdue University in aerospace eng. Aircraft Designer.

 

"Yaw is typically just the heading of the aircraft on the compass.

 

Sideslip is the relative angle between the freestream flow and the aircraft yaw vector (to simplify it somewhat). Sideslip is the analog of angle of attack, but for yaw instead of pitch."

 

https://www.quora.com/Aerospace-Engi...ide-slip-angle

 

Side slip angle or weathering is what Shagrat is trying to explain here.

 

with reference to what started all this,

 

 

Yep, correct. In the air the effect is called "directional stability", it does the same as weathervaning on the ground, just not so pronounced.

Anyway I wanted to help the guy by pointing to the likely cause of his issue. The wind and the aircraft's tendency to put the nose into the wind.

 

Sorry to push the point, but there is zero tendency for an aircraft in flight to point its nose into wind. The only wind the aircraft sees is the relative wind (airspeed over the wings).

 

Again this is called angle of sideslip (AOS) same as AOA.

 

As shown in trackview.

 

 

 

.

Edited June 29, 2017 by David OC

[Weta43]

How can this have take > 200 posts ?

It's high school physics for 13 year olds...

[Weta43]

Side slip angle or weathering is what Shagrat is trying to explain here.

Several pages ago he seemed to acknowledge that any slip angle relative to the airmass, or 'weathervaning' only occurred at & immediately after takeoff, if there was a change in the speed of the airmass (a gust), or in the artificial circumstance that the aircraft does an airstart in DCS.world.

In those circumstances - the uneven forces will push the tail around until the nose faces into the apparent wind and an equilibrium is reached. Prior to equilibrium being reached there will be a slip angle relative to the airmass. After it is reached, there won't be.

 

Although it's been brought up, this really isn't rocket science.

[David OC]

Several pages ago he seemed to acknowledge that any slip angle relative to the airmass, or 'weathervaning' only occurred at & immediately after takeoff, if there was a change in the speed of the airmass (a gust), or in the artificial circumstance that the aircraft does an airstart in DCS.world.

In those circumstances - the uneven forces will push the tail around until the nose faces into the apparent wind and an equilibrium is reached. Prior to equilibrium being reached there will be a slip angle relative to the airmass. After it is reached, there won't be.

 

Although it's been brought up, this really isn't rocket science.

 

Totally agree,

 

The problem is explaining that "equilibrium" to BigDuke6ixx. To him it's not there at all, as seen below in the first post. "equilibrium" or Angle of Slip into the wind.

 

 

Sorry to push the point, but there is zero tendency for an aircraft in flight to point its nose into wind. The only wind the aircraft sees is the relative wind (airspeed over the wings).

 

 

.

[Weta43]

Most of you are talking past each other.

 

Read it this way:

Once that equilibrium is reached, there's no 'cross wind' for the nose to point into, there's only the apparent movement through the (moving) airmass, which to the aircraft comes from directly ahead of the aircraft, and causes no further rotational force.

[shagrat]

Several pages ago he seemed to acknowledge that any slip angle relative to the airmass, or 'weathervaning' only occurred at & immediately after takeoff, if there was a change in the speed of the airmass (a gust), or in the artificial circumstance that the aircraft does an airstart in DCS.world.

In those circumstances - the uneven forces will push the tail around until the nose faces into the apparent wind and an equilibrium is reached. Prior to equilibrium being reached there will be a slip angle relative to the airmass. After it is reached, there won't be.

 

Although it's been brought up, this really isn't rocket science.

 

Yep, actually I was talking from the start about the take off phase and the phase directly after lift off, where the plane still has inertia of its mass.

Then it moved on to "planes do not 'weathervane' once in the air, and I said, that it depends on the CoG / inertia acting as pivot point. As long as the CoG is traveling at the same speed and direction as the relative wind, no force is applied to the fuselage and tail.

Whenever the plane changes that vector (course change), the inertia of the mass will need to be overcome again, just you won't notice as a pilot, because the control inputs you make to turn the plane would completely hide the effect. It can only be "calculated".

 

To undermine this fact I made the last track. I am aware that planes do not spawn in mid-air, but as we can simulate it with DCS, why not use it to show the forces at work?

 

The plane is spawning and flies in a 360° direction with 270 kts GS at about 2000ft AGL (that is what it is set to, in the ME). Crosswind from 270° (W->E) at about 20kts.

 

According to BigDuke6ixx the plane should fly a ground track of about 004° to 005° and keep a heading of 360° as the wind drifts the plane to the opposite side with the reciprocal WCA.

 

What it does is, flying a ground track from 359.8 to 0.2° while keeping a heading of 3-4° for nearly a minute. after that it start turning noticably to the right and when the right wing dropped it started turning reaching up to 11° after 3 min.

 

The interesting part is the 30-40 seconds at the beginning, between settling from the disturbance after spawning (at about 4sec) to 40seconds into the track. If no force is pushing the nose to the left, what is it? :huh: ...and no, it isn't sideslipping either, no control inputs just the plane and the wind.

 

EDIT ...and I was never talking about a sideslip, or forward slip or any other control inputs other than what you would need to do, to keep the aircraft from drifting of the extended runway centerline after take off, which I propably shouldn't have, because it was confusing for some.

Edited June 29, 2017 by shagrat

[BigDuke6ixx]

http://www.physicsclassroom.com/mmedia/vectors/plane.cfm

 

Note that the aircraft in the crosswind example doesn't weathervane its nose into the wind.

 

Note that the Animation does not show, the pilot using rudder or aileron to keep the nose on course, pointing straight, if he would let the rudder/aileron go, the tail would catch the wind and yaw the plane around the center of gravity resulting in the plane flying a curve into the wind.

 

It is shown in the NASA example by kylekatarn720.

 

And you stand by this claim that opposite rudder and aileron is required to keep the 'nose pointing straight'?

Edited June 29, 2017 by BigDuke6ixx

[shagrat]

And you stand by this claim that opposite rudder and aileron is required keep the 'nose pointing straight'?

While the inertia "anchors" the CoG you would turn the nose back on the extended centerline, as the rudder input induces a little drag you counter the drag with a bit of aileron to keep wings level... or at least that is what I do after liftoff in a crosswind.

You could also just sideslip to counter the upcoming drift until inertia is overcome, but I guess this is personal preference.