Slowflight Question

[FrankenkotaFlyer]

Originally Posted by Captain

Maybe I should head over to BJC. I've only been there 200 times. I grew up in Arvada and the first time I was on a runway in BJC was in 1987. Got me beat?

Yes, winds can change and that affects aircraft. But my point that has nothing to do with wind shear was that once a plane is in the air heading doesn't matter with respect to gusty winds or winds in general.

Yes, I have you beat. I've got more than 200 landings at BJC and I know that wind shear matters.

The whole point of wind shear is that heading does matter. Heading with the gust is bad, heading into the gust is good. Got it?

[iHenning]

Originally Posted by Inverted

You act like slow flight isn't a PTS standard which is a calm wind, fair weather standard. If its turbulent the examiner will be more forgiving and won't, nor can't hold you to the calm wind standard. Do slow flight where you can pick an outside reference, if you can't, use the DG thats what its there for. Who gives a crap about wind direction when you are 3500 feet AGL or more. It doesn't matter plain and simple because its not a ground reference maneuver. You will most likely do a 90 degree turn to one side, then back to your original heading. No biggie.

True, it occupies a few minutes most depending on how quickly you get stabilized.

[Captain]

Originally Posted by Clark1961

Yes, I have you beat. I've got more than 200 landings at BJC and I know that wind shear matters.

The whole point of wind shear is that heading does matter. Heading with the gust is bad, heading into the gust is good. Got it?

Landing is a ground refrence maneuver and specifically excluded from my 'heading doesn't matter' position.

How did we get into a number of landings at BJC contest? And what did you win?

[iNdigo]

Originally Posted by Captain

Landing is a ground refrence maneuver and specifically excluded from my 'heading doesn't matter' position.

Windshear doesn't only happen when you are landing (or taking off).

[iASCIIart]

Originally Posted by Captain

Yes, winds can change and that affects aircraft. But my point that has nothing to do with wind shear was that once a plane is in the air heading doesn't matter with respect to gusty winds or winds in general.

There's a bunch of people killed in airliner crashes who would disagree... But that's fairly irrelevant to a small airplane.

Henning, I have to disagree with you: During Private Pilot PTS slow flight (IE, near the stall with the wings level), you cannot turn downwind fast enough to get a stall from being downwind - You would stall due to the increased load factor long before you would stall due to the changing wind. At the rates of turn possible during slow flight and the weights of the average training airplane, there is not enough inertia to cause a problem.

Captain, I also have to disagree with you: Wind shear does matter somewhat. However, I doubt anyone's going to be doing slow flight while descending through a shear layer or flying through a microburst, thus in the OP's scenario it doesn't matter.

Funkeruski, you've discovered one of the facets of this board: We can nit-pick the simplest answer to death! But it's interesting to consider all the out-of-the-box scenarios too, so I hope you've learned something even though, as Ben points out, you had your answer at post 2!

[iHenning]

Originally Posted by flyingcheesehead

Henning, I have to disagree with you: During Private Pilot PTS slow flight (IE, near the stall with the wings level), you cannot turn downwind fast enough to get a stall from being downwind -

Nope, you're not disagreeing with me at all. I always said it was a fractional deal on the very edge only. As you say, as it is normally flown, the down wind turn will never effect a flying plane, something else will f- up first. That is my position as well. Just pointing out that this is the spark of reality that has born us the downwind turn myth that I find still exists today.

Wind shear on the other hand counts for everything when you're on a spray pass at 3'; you end up dropping out of your harness head first.

[Captain]

Grrrrr,

I don't care how hard the wind is blowing or how fast you "turn downwind" the airplane will never ever, not in a million attempts, ever experiance a 'tail wind' or even a fraction of a loss of lift. The plane is in the airmass and moves with it. From the planes perspective the airmass doesn't move.

Windshear is outside the scope of slow flight as it pertains to the PTS. Is there WS? Of course and it's an important topic. Just doesn't apply to the OPs question...which was answered on post two.

[iHenning]

Originally Posted by Captain

Grrrrr,

I don't care how hard the wind is blowing or how fast you "turn downwind" the airplane will never ever, not in a million attempts, ever experiance a 'tail wind' or even a fraction of a loss of lift. The plane is in the airmass and moves with it. From the planes perspective the airmass doesn't move.

Windshear is outside the scope of slow flight as it pertains to the PTS. Is there WS? Of course and it's an important topic. Just doesn't apply to the OPs question...which was answered on post two.

It will experience a fraction of a component of loss of lift as the plane turns off the wind due to the inertia of the vector path in relationship to the change in airmass to airfoil aspect. No, it will never effect anybody, that's why I called the deadly downwind turn a myth.

[Captain]

Originally Posted by Henning

It will experience a fraction of a component of loss of lift as the plane turns off the wind due to the inertia of the vector path in relationship to the change in airmass to airfoil aspect. No, it will never effect anybody, that's why I called the deadly downwind turn a myth.

No, it won't.

A plane doing 360 turns in calm air flies the exact same as a plane doing 360 turns in air moving 300 kts. (assume no turbulance in either). Point is wind alone has ZERO effect on the plane except ground track.

[Oldman]

Originally Posted by Captain

Point is wind alone has ZERO effect on the plane except ground track.

Well, OK, this may be a good place for you folks to educate me. I used to agree with this statement, having absorbed Wolfgang Langewiesche's analogy to the man walking around inside the train. But he wrote fifty years before people "discovered" wind shear. I have never (knowingly) encountered wind shear, but everything I read suggests that it actually does change the air flow over the wings, so that 95 KIAS can become 75 KIAS for example. Yes? No?

- jkw

[Captain]

Yes. Wind (absent wind shear) has no effect...wind shear does certainly have an effect.

[Dan Mc]

The physics of the downwind turn -- continued discussion....

[Dan Mc]

Originally Posted by Captain

Yes. Wind has no effect...wind shear does certainly have an effect.

Wind shear isn't wind?

[Captain]

Originally Posted by dmccormack

Wind shear isn't wind?

Fine, FIFY.

[iNdigo]

Originally Posted by Oldman

I have never (knowingly) encountered wind shear, but everything I read suggests that it actually does change the air flow over the wings, so that 95 KIAS can become 75 KIAS for example. Yes? No?

Yes. Many people use an analogy between wind and water. If you are swimming in a steady current you won't feel the effects. However wind, like water, can have eddies and merging flows of air. You feel that standing outside on a gusty day. The wind is not constant. If you fly into a decreasing headwind or an increasing tailwind your airspeed will drop momentarily as you cross the boundary of different air masses. If you are not anywhere close to stall speed or the ground this doesn't matter too much. The airplane will accelerate again in the new parcel of air. However if you are close to stall speed such as when you are taking off or landing this could be a problem. You'll often hear windshear reports, depending on where you fly. They are usually given as plus or minus X knots.

[iHenning]

Originally Posted by Captain

No, it won't.

A plane doing 360 turns in calm air flies the exact same as a plane doing 360 turns in air moving 300 kts. (assume no turbulance in either). Point is wind alone has ZERO effect on the plane except ground track.

Correct, Ground Track = Gravity Well/Field of Earth which is where inertia lies. Inertia adds the 'ground track' component to the equation when you add an acceleration component off the wind. You can't leave gravity out of any energy equation.

[iHenning]

Originally Posted by Oldman

Well, OK, this may be a good place for you folks to educate me. I used to agree with this statement, having absorbed Wolfgang Langewiesche's analogy to the man walking around inside the train. But he wrote fifty years before people "discovered" wind shear. I have never (knowingly) encountered wind shear, but everything I read suggests that it actually does change the air flow over the wings, so that 95 KIAS can become 75 KIAS for example. Yes? No?

- jkw

Secondary issue not under debate. The only issue is one of inertia vs acceleration with a changing aspect of the airframe to wind separate of the airframes inertial path. It is inconsequential, however it does exist.

[Captain]

Maybe if you better explained your theory of inertia and how it effects a plane turning from upwind to downwind. Describe an airplane in steady (smooth) air blowing 300kts over the ground.

What would happen to a C-150 doing steady turns over and over in such a condition. No wind shear and no turbulence. Just a steady wind blowing 300 kts. What happens to the plane?

[iHenning]

Originally Posted by Captain

Maybe if you better explained your theory of inertia and how it effects a plane turning from upwind to downwind. Describe an airplane in steady (smooth) air blowing 300kts over the ground.

What would happen to a C-150 doing steady turns over and over in such a condition. No wind shear and no turbulence. Just a steady wind blowing 300 kts. What happens to the plane?

Understand that due to inertia, when you add an acceleration off the wind, the heading of the airplane & therefore the aspect of the wing to the relative wind will lead the change in the path of the mass of the airplane. This is because the airplane travels within the Earths gravity which acts perpendicular to the center of mass of the Earth. Think of gravity as the atmosphere and inertia as the airplane where when you make that turn you skid. Gravity, water, and air all act in a similar fashion as far as drag dynamics go, however they operate at different and independent rates which causes skidding. It's this bit of skidding in a turn that causes an angular difference between the path of the aircraft and the relative wind to the wing. It's during this time where we are waiting for one path to reintegrate with the other in a steady state that we create a loss differential in lift as we head off the wind and pick up lift as we round into it. Magnetism acts similarly and produces the lead/lag turning errors. We operate aircraft in 2 fluids, gravity and atmosphere, boats handle in 3 fluids. Did that help?

[Captain]

Not really.

So, if the airmass is moving at 300 kts at 5,000 feet what happens to the plane doing circles (besides having the center of it's circle move across the ground at 300 kts)? Again...assume it's a steady 300 kts and there is no turbulence (or wind shear for those nit picking that angle).


btw, I know the wind never blows at 300 kts. I just find that using an extreme helps to make a point.

[Cap'n Jack]

Originally Posted by Henning

Correct, Ground Track = Gravity Well/Field of Earth which is where inertia lies. Inertia adds the 'ground track' component to the equation when you add an acceleration component off the wind. You can't leave gravity out of any energy equation.

You have some very odd physics.

[iHenning]

Originally Posted by Captain

Not really.

So, if the airmass is moving at 300 kts at 5,000 feet what happens to the plane doing circles (besides having the center of it's circle move across the ground at 300 kts)? Again...assume it's a steady 300 kts and there is no turbulence (or wind shear for those nit picking that angle).


btw, I know the wind never blows at 300 kts. I just find that using an extreme helps to make a point.

The strength of the wind is irrelevant for the most part, only the direction and quantity of the acceleration (turn) relative to into or away from the wind. A turn away from the wind will have a shift turning the wings away from the relative wind as the mass of the plane proceeds on it's inertial path. The angular difference is proportionately represent by the Gs you are pulling in the turn and is the same force interaction. Lomcevocks and tumbling maneuvers are the extreme examples of this effect.

If you're in SoFla, I'll keep explaining over beer, you can't see my hands and I can't explain it without, (anybody who has met me just blew Coke out their nose.)

[Captain]

That's the point. If I'm in a 600 kt (see I doubled it for you) wind and I make a standard rate turn to the right then I simply turn to the right. Earth is flying by but my airplane does NOT care. It's just a turn. I do not lose lift as I turn to downwind and I suspect you are saying that I do.

It's a fact that I do not. I'll be happy to argue this point till the cows crow.

[FrankenkotaFlyer]

Originally Posted by Captain

Landing is a ground refrence maneuver and specifically excluded from my 'heading doesn't matter' position.

How did we get into a number of landings at BJC contest? And what did you win?

"Captain," you started the ****ing contest, I finished it. Wind shear can have an impact during just about any phase of slow flight.

[iHenning]

Originally Posted by Captain

That's the point. If I'm in a 600 kt (see I doubled it for you) wind and I make a standard rate turn to the right then I simply turn to the right. Earth is flying by but my airplane does NOT care. It's just a turn. I do not lose lift as I turn to downwind and I suspect you are saying that I do.

It's a fact that I do not. I'll be happy to argue this point till the cows crow.

Sigh, never mind, you aren't getting it.