Some kind of autopilot?

[Yurgon]

It is on take off! Only in Air when all forces are balanced (Equilibrium) the effect is temporarily gone.

As soon as you change the balance of force inertia from the mass of the plane will act according to Newton's 3rd law and create an asymmetrical force, until the forces are in equilibrium, again.

 

While you are already using ailerons and rudder, to turn the plane and most of the force acts on the wings now, you would likely not notice the remaining fraction of the forces acting on the rudder.

 

Especially, as this is a dynamic process, with multiple controls, usually.

 

Not that I have been trying to explain this for about 20 pages including sketches to show how the asymmetrical reaction force works.

 

In the track example (with the mid-air spawn) you can see what happens if the inertia is "back" immediately, with no build up through control inputs and how it hits the plane.

 

I've done all I can to explain why Newton's axioms do not cease to affect a plane in flight. As soon as you have a mass that acts as an anchor and an imbalance in forces the object must turn, how much, how fast is determined by the parameters.

 

I don't see any benefit in going through yet another iteration of what I posted, already.

 

Leave it be! I have wasted enough time on this.

 

Let's agree we disagree....

 

I'm still entirely oblivious as to what it is you're trying to say.

 

Your statements along this discussion appear contradictory to me. What I thought you said, you negated later on. You insisted others are wrong in every imaginable way and then agreed on many of their points. You painted diagrams of aircraft in cross country flight but then insisted everything only really matters on take-off, except that it also happens in flight, but not as pronounced, actually more in a way that is practically invisible, yet still very much present.

 

Since I don't know what it is you're trying to say, we can't even agree to disagree. Maybe we mean the same thing the whole time, though I still think we have a very different understanding of the effect of wind on the motion of aircraft.

 

I guess the one thing we can agree on is that this discussion has reached a point where the prospect of enlightenment is so slim that there is simply no use continuing.

 

How about that: If we get windy conditions during one of the upcoming trainings, you grab an A-10 and we see if we can't figure out in flight what our respective positions are?

[BigDuke6ixx]

 

How about that: If we get windy conditions during one of the upcoming trainings, you grab an A-10 and we see if we can't figure out in flight what our respective positions are?

 

I wonder if the relevant wikipedia articles will be getting anymore sneaky edits? ;)

[kylekatarn720]

I do not want to fan the flames but this whole thread is basically about the question if an aircraft turns into the direction of wind while in the air, right?

 

dude that question resulted in 26 pages of posts, are you sure you wanna do this :d

[David OC]

I agree with all of you guys in what you are trying to explain here in you're context.

 

So lets keep this fun and light can we. :)

 

I do agree also with Weta43 here, that we are talking past each other.

 

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.

 

Said well too Weta43.

 

This is called AOS Angle of side slip

 

 

This is an incorrect use of the term side slip. Side slip is an aerodynamic measurement. It is perfectly normal for an airplane to have a heading different than ground track and to have an angle of side slip of zero.

 

The difference in azimuth between where the airplane is pointing and moving is typically known as drift or drift angle. In normal flight with a crosswind there will be lateral drift but no sideslip.

 

I'm also not agreeing with your use of the word yaw. Yaw is not heading. Yaw is rotational motion, not rotational position. And the "yaw vector" is straight out of the top of the airplane just like the roll vector is forward and pitch vector toward the right wingtip.

 

I was talking about AOS in this context Frederf.

(AOS) It relates to the rotation of the aircraft centerline from the relative wind https://en.wikipedia.org/wiki/Slip_(aerodynamics)#Sideslip_angle

 

 

Now can anyone here, BigDuke6ixx, WindyTX, Frederf

 

Please tell me your interpretation of how Eli Cohen an aerospace engineer, explains what Side slip angle is.

 

"What is the difference between Yaw angle and Side slip angle"

 

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."

 

 

"free stream flow" meaning

 

The freestream is the air far upstream of an aerodynamic body, that is, before the body has a chance to deflect, slow down or compress the air.

 

https://www.quora.com/Aerospace-Engineers-What-is-the-difference-between-Yaw-angle-and-Side-slip-angle

https://en.wikipedia.org/wiki/Slip_%28aerodynamics%29#Sideslip_angle

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

 

 

.

Edited June 29, 2017 by David OC

[Frederf]

I was talking about AOS in this context Frederf.

Sorry, in one case you stated this

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 .

The lateral displacement of the TVV on the HUD is not necessarily (general not) equal to the beta angle. Coordinated flight in a crosswind will have the TVV displaced downwind while the beta angle is zero. Every other time when you mentioned the angle of local airflow to airplane orientation is of course right but this one time when you talk about TVV placement on HUD showing beta angle it is not true.

[David OC]

Yep,

 

Thanks for clearing that up Frederf, I was starting to mix things together myself.:)

 

When we are talking about beta angle, I know this phenomenon just happens when flying as Weta43 said.

 

"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."

 

What hasppens to an aircraft when it hits a stronger wind force from the same angle in the flight, a new beta angle and new AOS

 

 

 

Why did these guys blow off your post here then? We need to take ground track (Side Slip) to location, out of the discussion.

https://forums.eagle.ru/showthread.php?t=189683&page=21

 

 

When both winds are applied at once (forward flight in cross wind) both winds apply torquing forces on the tail to attempt to point the airplane's nose into the direction each wind is coming from. Wind from each is applying a greater force on the tail than the nose at all times (even when beta is zero). The airplane is therefore subject to yaw torque in both directions at the same time by the wind of motion and the environmental wind. These two torques achieve a balance at some heading angle in between pointing at each source of wind. Despite achieving a balance in forces, the crosswind is applying a force on the tail to rotate the airplane forever and always but it cannot do so because there is another wind trying to do the opposite.

 

 

 

Biggest load of tosh I have ever read.

 

But if your plane is taxying you would be exactly right.

 

Sent from my SM-G955U using Tapatalk

 

 

WindyTX,

 

Lets Re Cap what this all started from and what I think shagrat is trying to Communicate here.

 

Aircraft don't weathervane once airborne.

 

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).

 

 

"but there is zero tendency for an aircraft in flight to point its nose into wind"

 

Is this sentence above correct or Not?

 

.

Edited June 30, 2017 by David OC

[WindyTX]

David why do you keep bringing up sideslip. It has nothing to do with the Wind effects we are talking about. Yes it exists yes your diagrams are correct just has nothing to do with the conversation.

 

Sent from my SM-G955U using Tapatalk

[Yurgon]

David why do you keep bringing up sideslip. It has nothing to do with the Wind effects we are talking about. Yes it exists yes your diagrams are correct just has nothing to do with the conversation.

 

On the plus side, he didn't mention the name of that aeronautics engineer and all his merits. :lol:

[David OC]

Yet they wont answer a simple question about this?

 

Please tell me your interpretation of how Eli Cohen an aerospace engineer, explains what Side slip angle is.

 

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).

 

 

"but there is zero tendency for an aircraft in flight to point its nose into wind"

 

Is this sentence above correct or Not?

.

Edited June 30, 2017 by David OC

[Yurgon]

Please tell me your interpretation of how Eli Cohen an aerospace engineer, explains what Side slip angle is.

 

Ah, finally! I thought I'd never hear his name again. Doesn't he hold a BS and an MS from different universities?

 

"but there is zero tendency for an aircraft in flight to point its nose into wind"

 

Is this sentence above correct or Not?

.

 

For the sake of clarity, let me define wind as: Movement of air across the planet's surface. Then the statement "There is zero tendency for an aircraft in flight to point its nose into wind" is correct to the best of my understanding.

[WindyTX]

+1 to what Yurgon yes its correct the Aircraft only knows about the Relative wind. If I do a dogfight with another Aircraft the wind at altitude is irelavent the fight is the same if the wind is 0 or a 150kts jetstream as long as it is constant for the altitude block the fight takes place in.

 

Sent from my SM-G955U using Tapatalk

[BigDuke6ixx]

Yet they wont answer a simple question about this?

 

Please tell me your interpretation of how Eli Cohen an aerospace engineer, explains what Side slip angle is.

 

 

 

 

"but there is zero tendency for an aircraft in flight to point its nose into wind"

 

Is this sentence above correct or Not?

.

 

sad to see that you haven't learnt a single thing. What's your opinion now regarding my statement? Is it correct, yes or no?

 

I said it right at the beginning, it's correct. Note that I haven't done any backsliding at all, unlike you and your side of the argument.

Edited June 30, 2017 by BigDuke6ixx

[BigDuke6ixx]

I should amend my previous conclusion about the response from an airplane subject to crosswind suddenly. I said that the heading will respond by changing the heading without changing the course. I.e. the airplane will pivot into the wind changing heading but not changing course.

 

The more careful look at the situation is that the effect will be a mixture of course and heading change. While the heading change is occurring due to yaw stability, there is some lateral acceleration. This lateral acceleration changes the course. The nose position that results in no beta angle to the air flow will not be the crab angle for the initial course but the course that has developed during the time the airplane was responding in heading.

 

An airplane with low yaw stability and low resistance to lateral acceleration will change course due to a sudden onset of crosswind and do little change of heading. Conversely an airplane with high yaw stability and high resistance to lateral acceleration will mostly pivot into the wind with minimal course change.

 

---

 

Back to the steady state situation...

 

You can think about an airplane moving in a crosswind in two ways: that the airplane is subject to two winds simultaneously from two sources or that it is subject to a single wind which is a combination of the two.

 

In the two-winds manner of thinking there is a wind opposite to the direction of motion. For example if the airplane is traveling south to north this is effectively a wind from north to south. Additionally there is a second wind which is the air movement which one would feel if the airplane was not in motion. Examined separately it should be clear that the airplane will be torqued to point directly into that one wind.

 

When both winds are applied at once (forward flight in cross wind) both winds apply torquing forces on the tail to attempt to point the airplane's nose into the direction each wind is coming from. Wind from each is applying a greater force on the tail than the nose at all times (even when beta is zero). The airplane is therefore subject to yaw torque in both directions at the same time by the wind of motion and the environmental wind. These two torques achieve a balance at some heading angle in between pointing at each source of wind. Despite achieving a balance in forces, the crosswind is applying a force on the tail to rotate the airplane forever and always but it cannot do so because there is another wind trying to do the opposite.

 

 

The one-wind interpretation is to consider the wind due to motion and the environmental wind and call it "relative wind." It is mathematically identical to the two-wind interpretation and reaches the same conclusion. When the airplane is crabbed into the crosswind only wind, relative wind, is straight down the airplane longitudinally and there is no yaw torque.

 

 

Deciding which of these two interpretations is correct is unhelpful. They are both valid.

 

The wrongheadedness of the above post is just breathtaking and the conclusion at the end mind-numbing.

[Pikey]

The stamina of this conversation is it's only rewarding merit. The tone has disintegrated somewhat. I don't understand why people care what anyone else thinks about the effect. Guys you shoudl be nicer to each other, it sets a bad example.

[BigDuke6ixx]

The stamina of this conversation is it's only rewarding merit. The tone has disintegrated somewhat. I don't understand why people care what anyone else thinks about the effect. Guys you shoudl be nicer to each other, it sets a bad example.

 

Why do I care? Well, because wrongheadedness matters in that people are all free to report inaccuracies and bugs in the flight physics. Anyway, some people were grateful for the steer in the right direction.

[David OC]

sad to see that you haven't learnt a single thing. What's your opinion now regarding my statement? Is it correct, yes or no?

 

I said it right at the beginning, it's correct. Note that I haven't done any backsliding at all, unlike you and your side of the argument.

 

 

 

There is no need for this constant immaturity please BigDuke6ixx

 

As I have said before, a 1 page back....

 

 

I agree with all of you guys in what you are trying to explain here in you're context.

 

So lets keep this fun and light can we.

 

I do agree also with Weta43 here, that all are talking past each other.

 

 

I was sitting on the fence trying to workout what was going on, and to what context all you guys are trying to explain your point in context to...?

 

There is a misunderstanding here about Directional Stability and equilibrium of the aircraft and how and when this stability changes I think?

 

Frederf is talking here about how an aircraft gets to it's equilibrium.

 

 

When both winds are applied at once (forward flight in cross wind) both winds apply torquing forces on the tail to attempt to point the airplane's nose into the direction each wind is coming from. Wind from each is applying a greater force on the tail than the nose at all times (even when beta is zero). The airplane is therefore subject to yaw torque in both directions at the same time by the wind of motion and the environmental wind. These two torques achieve a balance at some heading angle in between pointing at each source of wind. Despite achieving a balance in forces, the crosswind is applying a force on the tail to rotate the airplane forever and always but it cannot do so because there is another wind trying to do the opposite.

 

 

+1 to what Yurgon yes its correct the Aircraft only knows about the Relative wind. If I do a dogfight with another Aircraft the wind at altitude is irelavent the fight is the same if the wind is 0 or a 150kts jetstream as long as it is constant for the altitude block the fight takes place in.

 

What I see, and correct me if I'm wrong, the misunderstanding here is.

 

Directional Stability and equilibrium

State in which opposing forces or influences are balanced.

 

 

WindyTX posted this above

 

"as long as it is constant for the altitude block the fight takes place in."

 

 

 

This is flying in a perfect bubble right, no change in wind, direction, speed or turbulence to change the equilibrium.

 

Any change and it will generate a stabilizing yaw moment into the wind.

 

As seen in this video. https://youtu.be/UQDI0YvLdtI?t=29

 

I think this is the misunderstanding here?

 

 

.

[BigDuke6ixx]

There is no need for this constant immaturity please BigDuke6ixx

 

As I have said before, a 1 page back....

 

 

 

I was sitting on the fence trying to workout what was going on, and to what context all you guys are trying to explain your point in context to...?

 

There is a misunderstanding here about Directional Stability and equilibrium of the aircraft and how and when this stability changes I think?

 

Frederf is talking here about how an aircraft gets to it's equilibrium.

 

 

 

 

 

 

What I see, and correct me if I'm wrong, the misunderstanding here is.

 

Directional Stability and equilibrium

State in which opposing forces or influences are balanced.

 

 

WindyTX posted this above

 

"as long as it is constant for the altitude block the fight takes place in."

 

 

 

This is flying in a perfect bubble right, no change in wind, direction, speed or turbulence to change the equilibrium.

 

Any change and it will generate a stabilizing yaw moment into the wind.

 

As seen in this video. https://youtu.be/UQDI0YvLdtI?t=29

 

I think this is the misunderstanding here?

 

 

.

 

The transient effects produced by gusts and passing through layers within the wind gradient are just that, transient. The misunderstanding is on your side of the argument (yes you have taken sides) and it relates to you not knowing the difference between wind and relative wind. You seem to think that these two forces have a constant, combined aerodynamic effect on a plane in flight. They don't. Wind, movement of an air mass in relation to the ground, only influences navigation, while relative wind, speed of the air as it travels from the nose to the tail, is what generates the aerodynamic force.

 

A crosswind will not overcome or the directional stability of the relative wind. The video you liked to only reinforces what we've been saying.

Edited June 30, 2017 by BigDuke6ixx

[David OC]

The misunderstanding is on your side of the argument (yes you have taken sides) .

 

OK I have taken sides then, are you like 8 years old or something? Oh you took side so there. LOL

 

 

Once again, nice immaturity and trolling throughout here.

 

and on that note I'm out.

 

Cheers

[WindyTX]

The conversation is about a constant wind with no turbulence.

 

Sent from my SM-G955U using Tapatalk

[David OC]

One more..

 

What is this NASA document talking about and how does it compare to the post below.

 

Quote

 

"The velocity of an object is a vector quantity having both a magnitude and a direction and when discussing velocities we must account for both magnitude and direction. The wind introduces an additional velocity component perpendicular to the flight path, as shown in the middle of the figure. The addition of this component produces an effective flow direction shown in red on the figure. The effective flow direction is inclined to the horizontal at an angle which we shall call angle b. The size of angle b depends on the relative magnitude of the wind and the rocket velocity. Since the effective flow is inclined to the rocket axis, an aerodynamic lift force is generated by the rocket body and fins. The lift force acts through the center of pressure cp of the rocket. For stability reasons, the cp is located below the center of gravity cg. The lift force generates a torque about the cg which causes the rocket to rotate. "

 

https://spaceflightsystems.grc.nasa.gov/education/rocket/rktcock.html

 

 

 

I should amend my previous conclusion about the response from an airplane subject to crosswind suddenly. I said that the heading will respond by changing the heading without changing the course. I.e. the airplane will pivot into the wind changing heading but not changing course.

 

The more careful look at the situation is that the effect will be a mixture of course and heading change. While the heading change is occurring due to yaw stability, there is some lateral acceleration. This lateral acceleration changes the course. The nose position that results in no beta angle to the air flow will not be the crab angle for the initial course but the course that has developed during the time the airplane was responding in heading.

 

An airplane with low yaw stability and low resistance to lateral acceleration will change course due to a sudden onset of crosswind and do little change of heading. Conversely an airplane with high yaw stability and high resistance to lateral acceleration will mostly pivot into the wind with minimal course change.

 

---

 

Back to the steady state situation...

 

You can think about an airplane moving in a crosswind in two ways: that the airplane is subject to two winds simultaneously from two sources or that it is subject to a single wind which is a combination of the two.

 

In the two-winds manner of thinking there is a wind opposite to the direction of motion. For example if the airplane is traveling south to north this is effectively a wind from north to south. Additionally there is a second wind which is the air movement which one would feel if the airplane was not in motion. Examined separately it should be clear that the airplane will be torqued to point directly into that one wind.

 

When both winds are applied at once (forward flight in cross wind) both winds apply torquing forces on the tail to attempt to point the airplane's nose into the direction each wind is coming from. Wind from each is applying a greater force on the tail than the nose at all times (even when beta is zero). The airplane is therefore subject to yaw torque in both directions at the same time by the wind of motion and the environmental wind. These two torques achieve a balance at some heading angle in between pointing at each source of wind. Despite achieving a balance in forces, the crosswind is applying a force on the tail to rotate the airplane forever and always but it cannot do so because there is another wind trying to do the opposite.

 

 

The one-wind interpretation is to consider the wind due to motion and the environmental wind and call it "relative wind." It is mathematically identical to the two-wind interpretation and reaches the same conclusion. When the airplane is crabbed into the crosswind only wind, relative wind, is straight down the airplane longitudinally and there is no yaw torque.

 

 

Deciding which of these two interpretations is correct is unhelpful. They are both valid.

 

 

The wrongheadedness of the above post is just breathtaking and the conclusion at the end mind-numbing.

 

 

Biggest load of tosh I have ever read.

 

But if your plane is taxying you would be exactly right.

 

 

 

 

 

.

Edited July 1, 2017 by David OC

[BigDuke6ixx]

One more..

 

What is this NASA document talking about and how does it compare to the post below.

 

Quote

 

"The velocity of an object is a vector quantity having both a magnitude and a direction and when discussing velocities we must account for both magnitude and direction. The wind introduces an additional velocity component perpendicular to the flight path, as shown in the middle of the figure. The addition of this component produces an effective flow direction shown in red on the figure. The effective flow direction is inclined to the horizontal at an angle which we shall call angle b. The size of angle b depends on the relative magnitude of the wind and the rocket velocity. Since the effective flow is inclined to the rocket axis, an aerodynamic lift force is generated by the rocket body and fins. The lift force acts through the center of pressure cp of the rocket. For stability reasons, the cp is located below the center of gravity cg. The lift force generates a torque about the cg which causes the rocket to rotate. "

 

https://spaceflightsystems.grc.nasa.gov/education/rocket/rktcock.html

 

.

 

 

 

I don't pretend to know anything about rockets.

 

https://spaceflightsystems.grc.nasa.gov/education/rocket/rktaero.html

 

Aerodynamic forces are generated and act on a rocket as it flies through the air. Forces are vector quantities having both a magnitude and a direction. The magnitude of the aerodynamic forces depends on the shape, size and velocity of the rocket and some properties of the air through which it flies. By convention, the single aerodynamic force is broken into two components: the drag force which is opposed to the direction of motion, and the lift force which acts perpendicular to the direction of motion. The lift and drag act through the center of pressure which is the average location of the aerodynamic forces on an object.

 

Aerodynamic forces are mechanical forces. They are generated by the interaction and contact of a solid body with a fluid, a liquid or a gas. Aerodynamic forces are not generated by a force field, in the sense of the gravitational field,or an electromagnetic field. For lift and drag to be generated, the rocket must be in contact with the air. So outside the atmosphere there is no lift and no drag. Aerodynamic forces are generated by the difference in velocity between the rocket and the air. There must be motion between the rocket and the air. If there is no relative motion, there is no lift and no drag. Aerodynamic forces are more important for a model rocket than for a full scale rocket because the entire flight path of the model rocket takes place in the atmosphere. A full scale rocket climbs above the atmosphere very quickly.

 

Aerodynamic forces are used differently on a rocket than on an airplane. On an airplane, lift is used to overcome the weight of the aircraft, but on a rocket, thrust is used in opposition to weight. Because the center of pressure is not normally located at the center of gravity of the rocket, aerodynamic forces can cause the rocket to rotate in flight. The lift of a rocket is a side force used to stabilize and control the direction of flight. While most aircraft have a high lift to drag ratio, the drag of a rocket is usually much greater than the lift.

 

We can think of drag as aerodynamic friction, and one of the sources of drag is the skin friction between the molecules of the air and the solid surface of the moving rocket. Because the skin friction is an interaction between a solid and a gas, the magnitude of the skin friction depends on properties of both solid and gas. For the solid, a smooth, waxed surface produces less skin friction than a roughened surface. For the gas, the magnitude depends on the viscosity of the air and the relative magnitude of the viscous forces to the motion of the flow, expressed as the Reynolds number. Along the surface, a boundary layer of low energy flow is generated and the magnitude of the skin friction depends on the state of this flow. We can also think of drag as aerodynamic resistance to the motion of the object through the fluid. This source of drag depends on the shape of the rocket and is called form drag. As air flows around a body, the local velocity and pressure are changed. Since pressure is a measure of the momentum of the gas molecules and a change in momentum produces a force, a varying pressure distribution will produce a force on the body. We can determine the magnitude of the force by integrating, or adding up the local pressure times the surface area around the entire body. The base area of a model rocket produces form drag.

 

Lift occurs when a flow of gas is turned by a solid object. The flow is turned in one direction, and the lift is generated in the opposite direction, according to Newton's third law of action and reaction. For a model rocket, the nose cone, body tube, and fins can turn the flow and become a source of lift if the rocket is inclined to the flight direction.

Edited July 1, 2017 by BigDuke6ixx

[David OC]

As long as there is CG and a rear big fin it's all good. They both travel through our atmosphere and some crosswind.

 

 

 

 

This airplane has yawed to the left, so oncoming wind is striking its right side. The wind strikes all parts of the aircraft's right surface, causing those parts of the aircraft to want to yaw left. The amount of yaw torque created is, once again, a function of the magnitude of the force and its distance from the center of rotation (center of gravity).

 

Wind striking the cockpit and engine cowling wants to rotate the front of the aircraft left, which would decrease stability (since it has to go right to stabilize with the wind). However, notice that there is a nice big vertical stabilizer. It's got a lot of surface area, meaning a lot of wind is hitting it, and it's pretty far from the center of gravity, giving it a big arm and therefore lots of torque.

 

https://www.quora.com/How-do-horizontal-and-vertical-stabilizers-maintain-level-flight-And-why-dont-the-wings-of-the-plane-act-like-a-giant-horizontal-stablizer-too

 

To me you will not see this very small amount of torque to achieve the balance at speeds with these aircraft we fly in DCS. The force and offset is still there.

Yo-Yo would be able to see these forces.

 

It's also a connected torque moment, not noticeable by pilot, thinner faster crosswind air would have little affect on the rudder AOA and CG torque.

 

Don't want to upset Yurgon here to much and I can list his credentials lol.

 

"Sideslip is the analog of angle of attack, but for yaw instead of pitch."

 

When I read this above, all I could see was AOA on the rudder surface, the more deflection the more change in torque that happens, this is what Frederf was explaining here in his words.

 

If you are just moving through the relative airflow why does the rudder have AOA? Then I see the aircraft hitting this relative flow with a wind speed offset to the side with your 400 knots. I see torque on the rudder or AOA.

 

Frederf

"The airplane is therefore subject to yaw torque in both directions at the same time by the wind of motion and the environmental wind. "

 

keel effect

In aeronautics, keel effect is the result of the sideforce-generating surfaces being above (or below) the center of mass (which coincides with the center of gravity) in any aircraft. Examples of such surfaces are the vertical stabilizer, rudder, and parts of the fuselage. When an aircraft is in a sideslip, these surfaces generate sidewards lift forces.

 

EDIT

 

 

 

 

This Picture is from the FAA Pilot's Handbook of Aeronautical Knowledge PDF

 

What is this pic telling me about relative wind here?

 

Quote page 5 - 18

Keel Effect and Weight Distribution

 

"A high wing aircraft always has the tendency to turn the

longitudinal axis of the aircraft into the relative wind, which is

often referred to as the keel effect."

 

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/media/pilot_handbook.pdf

 

 

 

.

Edited July 1, 2017 by David OC

[BigDuke6ixx]

As long as there is CG and a rear big fin it's all good. They both travel through our atmosphere and some crosswind.

 

 

 

 

This airplane has yawed to the left, so oncoming wind is striking its right side. The wind strikes all parts of the aircraft's right surface, causing those parts of the aircraft to want to yaw left. The amount of yaw torque created is, once again, a function of the magnitude of the force and its distance from the center of rotation (center of gravity).

 

Wind striking the cockpit and engine cowling wants to rotate the front of the aircraft left, which would decrease stability (since it has to go right to stabilize with the wind). However, notice that there is a nice big vertical stabilizer. It's got a lot of surface area, meaning a lot of wind is hitting it, and it's pretty far from the center of gravity, giving it a big arm and therefore lots of torque.

 

 

.

 

Only when in yaw.. As we have been trying to get across to you, the wind (movement of the atmosphere in relation to the ground) is not felt by the aircraft in flight as an aerodynamic force. The only 'wind' that the aircraft in flight feels aerodynamically is the relative wind. The green arrows in that diagram represent the relative wind. The direction of flight of that plane is the inverse on the green arrows.

 

 

All the wind does is change the ground track and groundspeed.

Edited July 1, 2017 by BigDuke6ixx

[BigDuke6ixx]

EDIT

 

 

 

 

[/b]This Picture is from the FAA Pilot's Handbook of Aeronautical Knowledge PDF

 

What is this pic telling me about relative wind here?

 

Quote page 5 - 18

Keel Effect and Weight Distribution

 

"A high wing aircraft always has the tendency to turn the

longitudinal axis of the aircraft into the relative wind, which is

often referred to as the keel effect."

 

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/media/pilot_handbook.pdf

 

 

 

.

 

 

 

You should read this section from page 396:

 

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/media/pilot_handbook.pdf

 

Effect of Wind

The preceding discussion explained how to measure a TC

on the aeronautical chart and how to make corrections for

variation and deviation, but one important factor has not

been considered—wind. As discussed in the study of the

atmosphere, wind is a mass of air moving over the surface of

the Earth in a definite direction. When the wind is blowing

from the north at 25 knots, it simply means that air is moving

southward over the Earth’s surface at the rate of 25 NM in

1 hour.

 

Under these conditions, any inert object free from contact

with the Earth is carried 25 NM southward in 1 hour. This

effect becomes apparent when such things as clouds, dust,

and toy balloons are observed being blown along by the wind.

Obviously, an aircraft flying within the moving mass of air

is similarly affected. Even though the aircraft does not float

freely with the wind, it moves through the air at the same

time the air is moving over the ground, and thus is affected

by wind. Consequently, at the end of 1 hour of flight, the

aircraft is in a position that results from a combination of

the following two motions:

 

• Movement of the air mass in reference to the ground

• Forward movement of the aircraft through the air mass

 

Actually, these two motions are independent. It makes no

difference whether the mass of air through which the aircraft

is flying is moving or is stationary. A pilot flying in a 70-

knot gale would be totally unaware of any wind (except for

possible turbulence) unless the ground were observed. In

reference to the ground, however, the aircraft would appear

to fly faster with a tailwind or slower with a headwind, or to

drift right or left with a crosswind.

 

Assuming no correction is made for wind effect, if an aircraft

is heading eastward at 120 knots and the air mass moving

southward at 20 knots, the aircraft at the end of 1 hour is

almost 120 miles east of its point of departure because of its

progress through the air. It is 20 miles south because of the

motion of the air. Under these circumstances, the airspeed

remains 120 knots, but the GS is determined by combining

the movement of the aircraft with that of the air mass. GS can

be measured as the distance from the point of departure to

the position of the aircraft at the end of 1 hour. The GS can

be computed by the time required to fly between two points a

known distance apart. It also can be determined before flight

by constructing a wind triangle, which is explained later in

this chapter.

 

The direction in which the aircraft is pointing as it flies is

called heading. Its actual path over the ground, which is a

combination of the motion of the aircraft and the motion of

the air, is called track. The angle between the heading and

the track is called drift angle. If the aircraft heading coincides

with the TC and the wind is blowing from the left, the track

does not coincide with the TC. The wind causes the aircraft

to drift to the right, so the track falls to the right of the desired

course or TC.

 

The following method is used by many pilots to determine

compass heading: after the TC is measured, and wind

correction applied resulting in a TH, the sequence TH ±

variation (V) = magnetic heading (MH) ± deviation (D)

= compass heading (CH) is followed to arrive at compass

heading. [Figure 16-16]

By determining the amount of drift, the pilot can counteract

the effect of the wind and make the track of the aircraft

coincide with the desired course. If the mass of air is moving

across the course from the left, the aircraft drifts to the

right, and a correction must be made by heading the aircraft

sufficiently to the left to offset this drift. In other words, if

the wind is from the left, the correction is made by pointing

the aircraft to the left a certain number of degrees, therefore

correcting for wind drift. This is the wind correction angle

(WCA) and is expressed in terms of degrees right or left of

the TC. [Figure 16-17]

Edited July 1, 2017 by BigDuke6ixx

[Yurgon]

Disclaimer: The following is to the best of my knowledge and understanding of aerodynamics. I wouldn't bet my house on it, but I'm about 99% sure.

 

"Sideslip is the analog of angle of attack, but for yaw instead of pitch."

 

I agree with that statement. I disagree that is has anything to do with the discussion of the last 300+ posts, no matter how often you bring it up.

 

Remember this question I asked you?

 

To put it differently: If I fly into a headwind, will that affect the Angle of Attack the same way that flying in a crosswind affects the Angle of Sideslip?

 

It was a trick question.

 

You answered:

 

Yes.:)

 

Wrong.

 

For an aircraft in flight (let's say wings level, stable heading, stable altitude, stable attitude, ball centered), there is no "headwind", "tailwind" or "crosswind".

 

Wind is the motion of air across the planet's surface.

 

For the purpose of clarity, let's assume steady wind, no gusts. I believe it is obvious that changing winds (gusts, wind shear, turbulence) will indeed affect an aircraft. But that's really not what this discussion has been about, it has been about the effect of a steady wind on the flight of an aircraft.

 

Wind affects the aircraft's movement in relation to the surface. It does not affect the aircraft's movement in relation to the air.

 

A headwind means an aircraft moves slower when observed from the ground, while a tailwind obviously makes the aircraft move faster across the ground. A crosswind will make an aircraft move in a diagonal fashion across the ground.

 

The movement of the airmass relative to the surface does not influence how the aircraft moves within it. A headwind does not affect the indicated air speed, and it does not change the Angle of Attack. A crosswind does not push the tail stronger than the nose, and it does not change the Angle of Sideslip.

 

Sideslip, or Beta, or yaw angle, could be caused by asymmetric drag, or by the aircraft being anchored to the ground (hence the weathervaning tendency on take-off), or by rudder input. I'm sure there are other possible reasons.

 

But no matter how often you quote someone who explains what sideslip is, it doesn't make wind the cause of it.