Some kind of autopilot?

[lemoen]

So many pages of dick swinging. Most of you are almost right or completely right but suck at explaining, or just wrong.

 

 

The aircraft weathervanes into the wind. Of course it does, else it wouldn't be going where you wanted it to go. BigDuke, your explanation is not quite correct, however, in general you are right (almost).

 

Whether a plane weathervanes into the crosswind has nothing to do with being on the ground or in the air, it has to to with airflow along the axis parallel to its wings. When it is on the ground or have just taken off, if there is air flowing in that direction, the nose is pushed into the wind and the centre of gravity of the plane is accelerated in the direction of the wind (because the aerodynamic stability of the plane requires the nose to point into airflow.). However, once the plane's CoG's velocity component in the direction of the wind is equal to the windspeed, this rotational force stops turning the plane.

 

So, I think you guys are arguing just for the sake of it and some of you are using rules of thumb approximation (plane on ground, plane in air) to explain physics and most aren't working it out from first principles.

[BigDuke6ixx]

So many pages of dick swinging. Most of you are almost right or completely right but suck at explaining, or just wrong.

 

 

The aircraft weathervanes into the wind. Of course it does, else it wouldn't be going where you wanted it to go. BigDuke, your explanation is not quite correct, however, in general you are right (almost).

 

Whether a plane weathervanes into the crosswind has nothing to do with being on the ground or in the air, it has to to with airflow along the axis parallel to its wings. When it is on the ground or have just taken off, if there is air flowing in that direction, the nose is pushed into the wind and the centre of gravity of the plane is accelerated in the direction of the wind (because the aerodynamic stability of the plane requires the nose to point into airflow.). However, once the plane's CoG's velocity component in the direction of the wind is equal to the windspeed, this rotational force stops turning the plane.

 

So, I think you guys are arguing just for the sake of it and some of you are using rules of thumb approximation (plane on ground, plane in air) to explain physics and most aren't working it out from first principles.

 

Yes, planes in flight do NOT weathervane into the wind (wind being the direction the air mass is moving in relation to the ground) which is what some are claiming. neilwills, for example, claims that a crosswind pushes harder against the tail of a plane than the nose in flight and caused the plane to yaw into wind. He is wrong.

Edited June 28, 2017 by BigDuke6ixx

[kylekatarn720]

However, once the plane's CoG's velocity component in the direction of the wind is equal to the windspeed, this rotational force stops turning the plane.

 

I agree with the rest of your post but why the 2 velocity vectors needs to be equal?

 

After aligning the longitudinal axis with the relative winds direction, there shouldnt be a velocity component of the relative wind on the lateral axis of the aircraft.

[lemoen]

I agree with the rest of your post but why the 2 velocity vectors needs to be equal?

 

After aligning the longitudinal axis with the relative winds direction, there shouldnt be a velocity component of the relative wind on the lateral axis of the aircraft.

 

I guess we're saying the same thing. Its when the airflow has no V_lateral component over the airframe. This all assumes all the air in the entire airspace is moving as a block at the same velocity (inertial reference frame) and the aircraft has been accelerated by this airflow after takeoff. Once it has, there is no rotation into the wind anymore because there is no 'wind'.

[kylekatarn720]

I guess we're saying the same thing. Its when the airflow has no V_lateral component over the airframe. This all assumes all the air in the entire airspace is moving as a block at the same velocity (inertial reference frame) and the aircraft has been accelerated by this airflow after takeoff. Once it has, there is no rotation into the wind anymore because there is no 'wind'.

 

ye it s the same.

[BigDuke6ixx]

ye it s the same.

 

You admit you were wrong then?

[kylekatarn720]

You admit you were wrong then?

 

im still saying the samething.

 

Edit: to be clear on the issue, i still think weathervaning will happen while flying. and i still think wind speed will effect both ias and tas.

 

Edit: Shagrat even drew you a picture. Too hard to grasp i suppose.

 

I might be wrong on both, i might be overlooking something (i dont think i am but it is possible) , still, in the end you will be the one who denied nasas explanation of weathercocking not me.

Edited June 28, 2017 by kylekatarn720

[David OC]

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.

 

This small amount of Yaw from a constant wind to symmetrically aligned with the aerodynamics of an aircraft. This would be more likely at slow speeds and would be different at those speeds per aircraft design, right?

 

Thinking now, this is what they mean by how much "directional stability" is in the aircraft design.

 

Directional stability is stability of a moving body or vehicle about an axis which is perpendicular to its direction of motion. Stability of a vehicle concerns itself with the tendency of a vehicle to return to its original direction in relation to the oncoming medium (water, air, road surface, etc

when disturbed (rotated) away from that original direction. If a vehicle is directionally stable, a restoring moment is produced which is in a direction opposite to the rotational disturbance. This "pushes" the vehicle (in rotation) so as to return it to the original orientation, thus tending to keep the vehicle oriented in the original direction.

 

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

 

If you take the A10 up with a good 20 to 30 knot crosswind @ 30 degrees or so, you can see the aircraft fighting to keep its heading track with no control input. (Body aligned with track) Will video.

 

There is no control needed here on the aircraft in a constant wind still, it's just how the aircraft will, shall we say, sit or pendulum in this unsymmetrical wind tunnel.

 

The yaw is around the CG as the wind and aircraft wants to be symmetrical, both wings same air flow etc. The CG and and tail want to go were the pilot put the heading. It's a small fight going on.

 

This is interesting tho, getting your head around this.:) Keep it fun guy's no need to get stroppy. Even I said dart before and that's not really correct here, when you have two very large wings. Yo-Yo could finish us off, that might be harder to workout possibly.;)

 

 

The way I see it, we have all been sort of correct, if that helps?:(

 

 

 

.

Edited June 28, 2017 by David OC

[BigDuke6ixx]

im still saying the samething.

 

Edit: to be clear on the issue, i still think weathervaning will happen while flying. and i still think wind speed will effect both ias and tas.

 

Edit: Shagrat even drew you a picture. Too hard to grasp i suppose.

 

I might be wrong on both, i might be overlooking something (i dont think i am but it is possible) , still, in the end you will be the one who denied nasas explanation of weathercocking not me.

 

As I thought, you didn't understand what he wrote, but agreed with him even though he is saying the opposite to you.

 

Also, the NASA rocket data is not applicable.

 

Finally, wind speed doesn't affect airspeed, apart from the transient effects from gusts. You even posted a video that proves you are wrong about this.

[kylekatarn720]

As I thought, you didn't understand what he wrote, but agreed with him even though he is saying the opposite to you.

 

Also, the NASA rocket data is not applicable.

 

Finally, wind speed doesn't affect airspeed, apart from the transient effects from gusts. You even posted a video that proves you are wrong about this.

 

ye, i dont know how to read, espcially in english.

 

ye, nasa shouldnt be included in this discussion, its not like their specialty after all.

 

ye, wind speed does not effect airspeed, afterall aircrafts travel in water not air.

 

and for the last time, ye, that video shows nothing about wind effecting airspeed.

 

The reason im using this forum is i want to learn more about aviation. Not gonna argue with you any further, im not learning anything from it.

[GurbY]

.....Finally, wind speed doesn't affect airspeed, apart from the transient effects from gusts. You even posted a video that proves you are wrong about this.

Right. In that case we have to discuss the many rought landings that I witnessed on our airbase with students making a final approach while the wind suddenly dropped. Why did those planes stall? Had nothing to do with the wind speed as you stated, so we will start an intern investigation what could have caused these stalls and rough landings.

[Yurgon]

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.

 

You also made it clear that this effect is also present in level flight. That's what the whole discussion is about. No one is arguing weathervaning during take-off (at least I don't think anyone is arguing that).

 

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.

 

Right. Show it.

 

I thought 10 pages ago that everything on the subject had already been said, just not by everyone. That hasn't changed.

 

I posted a track where I tried to replicate what you described. 60 kts crosswind, that should somehow make my aircraft weathervane, right? Except I couldn't find the smallest hint that this happens.

 

Did you watch the track?

 

Please provide a track or a video showing this effect.

 

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...

 

We can all point to numerous posts stating numerous things. All of us could point to posts of RL pilots who state with complete certainty that weathervaning does / does not happen. That doesn't advance the discussion, it just means entering yet another recursion loop. I don't like that.

 

So please with sugar on top, just show the effect in DCS. It seriously can't take more than 10 minutes to set up a mission and provide a clear, exhaustive example that will end this discussion once and for all.

 

(Well, then we'd argue if DCS got it right, but let's not go there just yet).

 

Right. In that case we have to discuss the many rought landings that I witnessed on our airbase with students making a final approach while the wind suddenly dropped. Why did those planes stall? Had nothing to do with the wind speed as you stated, so we will start an intern investigation what could have caused these stalls and rough landings.

 

BigDuke said multiple times that gusts (changes of windspeed and/or direction) will of course have an effect on airspeed and attitude. Do we really need to put a disclaimer after every single statement in order to prevent someone from quoting out of context?

[shagrat]

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?

That is correct, once the inertia is overcome and the wind does no longer apply any force to the fuselage/tail.

[shagrat]

I agree with the rest of your post but why the 2 velocity vectors needs to be equal?

 

After aligning the longitudinal axis with the relative winds direction, there shouldnt be a velocity component of the relative wind on the lateral axis of the aircraft.

Because the CoG is the pivot point.

When the plane lifts off the ground (isn't it in the air then?) the CoG moves along the course/heading from the take off roll.

Now the crosswind applies force to the fuselage and tail, as it is asymmetrical, it yaws, while at the same time the energy of the crosswind pushes the plane in the wind direction.

Now when the plane moves with the wind at the same speed the counter force seizes to exist, until you change course and inertia is effective, again.

 

Usually you wouldn't notice the later, as you apply controls and thus counter the yaw anyway, when turning, for example...

 

Really difficult to explain without seeing someone in the eye and taking a model or a hand. :(

[shagrat]

This small amount of Yaw from a constant wind to symmetrically aligned with the aerodynamics of an aircraft. This would be more likely at slow speeds and would be different at those speeds per aircraft design, right?

 

Thinking now, this is what they mean by how much "directional stability" is in the aircraft design.

 

Directional stability is stability of a moving body or vehicle about an axis which is perpendicular to its direction of motion. Stability of a vehicle concerns itself with the tendency of a vehicle to return to its original direction in relation to the oncoming medium (water, air, road surface, etc

when disturbed (rotated) away from that original direction. If a vehicle is directionally stable, a restoring moment is produced which is in a direction opposite to the rotational disturbance. This "pushes" the vehicle (in rotation) so as to return it to the original orientation, thus tending to keep the vehicle oriented in the original direction.

 

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

 

If you take the A10 up with a good 20 to 30 knot crosswind @ 30 degrees or so, you can see the aircraft fighting to keep its heading track with no control input. (Body aligned with track) Will video.

 

There is no control needed here on the aircraft in a constant wind still, it's just how the aircraft will, shall we say, sit or pendulum in this unsymmetrical wind tunnel.

 

The yaw is around the CG as the wind and aircraft wants to be symmetrical, both wings same air flow etc. The CG and and tail want to go were the pilot put the heading. It's a small fight going on.

 

This is interesting tho, getting your head around this.:) Keep it fun guy's no need to get stroppy. Even I said dart before and that's not really correct here, when you have two very large wings. Yo-Yo could finish us off, that might be harder to workout possibly.;)

 

 

The way I see it, we have all been sort of correct, if that helps?:(

 

 

 

.

Yep, actually I think we all mean the same things and for my part, I had some difficulty to get the "in the air part" right, as I was so focused on the phase after takeoff and the physical part of action and reaction, through inertia.

 

I am not sure by the way how this is modeled in DCS when starting in mid-air... Do you start already moving with the wind, or spawn directly in the air with only the thrust vector and the full inertia in effect?

Need to try this later... :)

[Exorcet]

Right. In that case we have to discuss the many rought landings that I witnessed on our airbase with students making a final approach while the wind suddenly dropped. Why did those planes stall? Had nothing to do with the wind speed as you stated, so we will start an intern investigation what could have caused these stalls and rough landings.

 

That's transient wind as Duke mentioned.

 

Having paged through the discussion quickly, I think both sides are right. There is communications issue where one person is talking about something slightly different from the other.

 

A completely uniform moving mass of air is completely identical to stationary air as far as the aircraft is concerned.

[shagrat]

You also made it clear that this effect is also present in level flight. That's what the whole discussion is about. No one is arguing weathervaning during take-off (at least I don't think anyone is arguing that).

 

 

 

Right. Show it.

 

I thought 10 pages ago that everything on the subject had already been said, just not by everyone. That hasn't changed.

 

I posted a track where I tried to replicate what you described. 60 kts crosswind, that should somehow make my aircraft weathervane, right? Except I couldn't find the smallest hint that this happens.

 

Did you watch the track?

 

Please provide a track or a video showing this effect.

 

 

 

We can all point to numerous posts stating numerous things. All of us could point to posts of RL pilots who state with complete certainty that weathervaning does / does not happen. That doesn't advance the discussion, it just means entering yet another recursion loop. I don't like that.

 

So please with sugar on top, just show the effect in DCS. It seriously can't take more than 10 minutes to set up a mission and provide a clear, exhaustive example that will end this discussion once and for all.

 

(Well, then we'd argue if DCS got it right, but let's not go there just yet).

 

 

 

BigDuke said multiple times that gusts (changes of windspeed and/or direction) will of course have an effect on airspeed and attitude. Do we really need to put a disclaimer after every single statement in order to prevent someone from quoting out of context?

I may sound cocky, but is a plane flying level one second after take off NOT flying level?

 

And track or no track, you are right, we could argue about DCS modeling it correctly.

 

I made an effort to draw a series of sketches to illustrate the math and physics.

 

Wind blows against a surface of an Object.

Inertia of the object's mass creates a counterforce. If the force is asymmetric to the CoG it will start to yaw/turn/spin the mass, even if it is a brick.

 

Until the inertia isn't completely overcome by the applied force it continues to create a counterforce.

The turn will stop before that happens if(!) the surfaces and thus the counterforce created is symmetric to the CoG.

 

I don't need a track to understand these laws of physics. They should apply to DCS and from what I have experienced so far, they are...

 

Maybe you want to provide a track where directly after take off you are simply pushed sideways and the noses heading remains, without compensation from trim, rudder or ailerons?

Edited June 28, 2017 by shagrat

[Yurgon]

I may sound cocky, but is a plane flying level one second after take off NOT flying level?

 

Yes. You do. ;)

 

Other than that, I fail to see what that (non-) distinction is supposed to prove.

 

We've established that aircraft will weathervane during take-off, that has never been disputed during the course of this discussion.

 

Standing by with a stop-watch in order to tell with 1 second precision what counts as "during take-off" and "after take-off" doesn't do us much good. I took 15 minutes to record a track of what I think you've been trying to claim. It took me another 5 minutes to double check that the track plays fine on my end.

 

I also watched your take-off track, several times, and told you why it has nothing to do with this discussion - because it shows the take-off, and because you actually provided additional input that exacerbated what you say is "weathervaning".

 

Did you even watch my track once?

 

Let's come back to this example of a cross-country flight.

 

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

 

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

 

 

If you keep the aileron and rudder neutral, this is what happens:

 

 

I don't need a track to understand these laws of physics. They should apply to DCS and from what I have experienced so far, they are...

 

Well, I need a track where you show that aircraft in level flight do indeed weathervane. Why are we still talking about this?

[BigDuke6ixx]

I may sound cocky, but is a plane flying level one second after take off NOT flying level?

 

And track or no track, you are right, we could argue about DCS modeling it correctly.

 

I made an effort to draw a series of sketches to illustrate the math and physics.

 

Wind blows against a surface of an Object.

Inertia of the object's mass creates a counterforce. If the force is asymmetric to the CoG it will start to yaw/turn/spin the mass, even if it is a brick.

 

Until the inertia isn't completely overcome by the applied force it continues to create a counterforce.

The turn will stop before that happens if(!) the surfaces and thus the counterforce created is symmetric to the CoG.

 

I don't need a track to understand these laws of physics. They should apply to DCS and from what I have experienced so far, they are...

 

Maybe you want to provide a track where directly after take off you are simply pushed sideways and the noses heading remains, without compensation from trim, rudder or ailerons?

 

A plane is flying north at 2,000ft, airspeed is 250, there is a 20kt crosswind from the west. Answer Yes or no: Do you still insist that the crosswind is pushing harder against the tail than the nose and that opposite rudder and aileron needs to be applied (as per your diagram) for the duration of the fight north to counter this rotational force you claim is present?

 

If the answer is 'no', then end of discussion and you are admitting you were wrong.

[BigDuke6ixx]

That's transient wind as Duke mentioned.

 

Having paged through the discussion quickly, I think both sides are right. There is communications issue where one person is talking about something slightly different from the other.

 

A completely uniform moving mass of air is completely identical to stationary air as far as the aircraft is concerned.

 

This is what they won't accept. They insist that a crosswind pushes harder against the tail than the nose of a plane in free flight. We really aren't talking about the same thing, it's just that they just don't understand the fundamentals.

[shagrat]

Yes. You do. ;)

 

Other than that, I fail to see what that (non-) distinction is supposed to prove.

 

We've established that aircraft will weathervane during take-off, that has never been disputed during the course of this discussion.

 

Standing by with a stop-watch in order to tell with 1 second precision what counts as "during take-off" and "after take-off" doesn't do us much good. I took 15 minutes to record a track of what I think you've been trying to claim. It took me another 5 minutes to double check that the track plays fine on my end.

 

I also watched your take-off track, several times, and told you why it has nothing to do with this discussion - because it shows the take-off, and because you actually provided additional input that exacerbated what you say is "weathervaning".

 

Did you even watch my track once?

 

Let's come back to this example of a cross-country flight.

 

 

 

If you keep the aileron and rudder neutral, this is what happens:

 

 

 

 

Well, I need a track where you show that aircraft in level flight do indeed weathervane. Why are we still talking about this?

Maybe I am wrong and as soon as a plane is off the ground the laws of physics no longer apply... When FatSlapper said he has issues with the controls acting like an autopilot is engaged in the "Instant action take off from Vegas", I simply tried to help, as I suspected mostly flew the usual missions with zero wind.

So when I suspected the aircraft turning into the wind directly after take off, I was "corrected" because "airplanes do not weathervane once airborne".

Then it started escalating, as I am pretty sure the laws of physics, like mass, inertia and action/reaction won't make an exception to a plane just because it lifts off the ground.

And to be clear, even in level flight at 10k ft I am very sure the same laws still apply, only that it is not possible to show somebody as a course change would require control input and you need to prove it mathematically by calculating the vectors.

Anyway that doesn't concern the pilot.

 

What I wanted to tell FatSlapper was that if you take off and get airborne in a crosswind there is a tendency of the aircraft's nose to turn slightly into the wind and he would need to counter that, by applying rudder in the opposite direction, and compensate the drag induced by the rudder with a little aileron.

 

But everybody told me "no in the air a plane doesn't do that"?!

 

Maybe somebody can prove that time is flowing in a linear fashion and not in steps?

[BigDuke6ixx]

That's transient wind as Duke mentioned.

 

Having paged through the discussion quickly, I think both sides are right. There is communications issue where one person is talking about something slightly different from the other.

 

A completely uniform moving mass of air is completely identical to stationary air as far as the aircraft is concerned.

 

Maybe I am wrong and as soon as a plane is off the ground the laws of physics no longer apply... When FatSlapper said he has issues with the controls acting like an autopilot is engaged in the "Instant action take off from Vegas", I simply tried to help, as I suspected mostly flew the usual missions with zero wind.

So when I suspected the aircraft turning into the wind directly after take off, I was "corrected" because "airplanes do not weathervane once airborne".

Then it started escalating, as I am pretty sure the laws of physics, like mass, inertia and action/reaction won't make an exception to a plane just because it lifts off the ground.

And to be clear, even in level flight at 10k ft I am very sure the same laws still apply, only that it is not possible to show somebody as a course change would require control input and you need to prove it mathematically by calculating the vectors.

Anyway that doesn't concern the pilot.

 

What I wanted to tell FatSlapper was that if you take off and get airborne in a crosswind there is a tendency of the aircraft's nose to turn slightly into the wind and he would need to counter that, by applying rudder in the opposite direction, and compensate the drag induced by the rudder with a little aileron.

 

But everybody told me "no in the air a plane doesn't do that"?!

Maybe somebody can prove that time is flowing in a linear fashion and not in steps?

 

He wasn't complaining about this transient effect, he was complaining about the sustained, turn inducing wing drop due to asymmetric payload with no trim applied, which he thought was an autopilot mode.

 

What we have said is that these transient effects from the crosswind go away once the plane speeds up and gains its full directional stability from its relative wind (which we measure as airspeed). You, OTOH, have continued to claim that these effects are permanent all the time there is a crosswind component. You even draw a diagram of a cross country flight showing how such an effect would need to be countered with opposite rudder and aileron for the duration of the flight at that heading.

Edited June 28, 2017 by BigDuke6ixx

[shagrat]

Midair start, NO(!) control inputs from my side.

 

A-10C flying north at 270 kts GS, 2000ft AGL, wind of some 20kts from 270°

 

 

And here the track

 

A-10C_clean_Midair.trk

[BigDuke6ixx]

Midair start, NO(!) control inputs from my side.

 

A-10C flying north at 270 kts GS, 2000ft AGL, wind of some 20kts from 270°

 

 

And here the track

 

[ATTACH]165084[/ATTACH]

 

And your results are? And your conclusion is?

[shagrat]

And your results are? And your conclusion is?

See for yourself, I have no idea why the nose of the plane points slightly to the west and stays there, my best guess is the crosswind is pushing asymmetricly against the airframe and the plane turns the nose into the wind, but that can't be, as laws of physics do not apply in the air? :dunno: