Slowflight Question

[Funkeruski]

I will probably be taking my checkride in the next couple of weeks, and have a question on slowflight. Is there any advantage to do the slowflight manuever into the wind if the examiner lets me pick my initial heading? My first thought was yes as it would be easier to get slowed up and the wind going over the wings would probably help maintain altitude. But, on second though, wouldn't the wind just effect groundspeed which should be irrelevant? So, is there any real advantage/disadvantage in starting slowflight upwind as opposed to downwind? Thanks.

 

[flyingcheesehead]

I will probably be taking my checkride in the next couple of weeks, and have a question on slowflight. Is there any advantage to do the slowflight manuever into the wind if the examiner lets me pick my initial heading? My first thought was yes as it would be easier to get slowed up and the wind going over the wings would probably help maintain altitude. But, on second though, wouldn't the wind just effect groundspeed which should be irrelevant? So, is there any real advantage/disadvantage in starting slowflight upwind as opposed to downwind? Thanks.

Your "second thought" is correct - The airplane doesn't know what the ground is doing, and rides with the air that it's in. So, your heading won't have any effect on slow flight or any other maneuver except groundspeed and ground track, which are only relevant to ground reference and pattern maneuvers.

That said, pointing into the wind for more of your maneuvers means you can stay in the practice area a bit easier!

 

[david.h]

Agree, your second thought is correct. However, if it is exceptionally gusty, the gusts will come from the prevailing wind direction and pointing into these gust fronts is probably a better idea (heading into wind) but doubtful that the signifigance of this is worth mentioning. The airplane will handle slowflight the same at any heading.

 

[Captain]

When airborne the airplane does not know or care where the wind or gusts come from. You move as a mass. The only time it matters is when you reference your flight to the ground.

 

[Funkeruski]

Great, thanks for all the feedback.

 

[Skylane81E]

I'd go directly into or out of the wind simply so the ground tracks strait under the plane making holding heading easier.

 

[poadeleted20]

I'd go directly into or out of the wind simply so the ground tracks strait under the plane making holding heading easier.

In most trainers, the nose is so high at minimum controllable airspeed that you can't see much of the ground ahead. At that point, all you really have to judge yaw divergence are the clouds you can see, and they are moving in the same airmass as you are, so it doesn't make any difference which way the wind is blowing.

 

[Henning]

Your second thought is correct, however at the very bottom of minimum controllable airspeed is where the legend of the deadly downwind turn has a shadow of merit especially in gusty conditions. Due to inertia, as you go to turn down wind, you can get a stall. Since most people flying MCA are maneuvering very gingerly and gently, this is not a real problem, it just gets a little closer to why the downwind turn myth exists.

 

[Skylane81E]

In most trainers, the nose is so high at minimum controllable airspeed that you can't see much of the ground ahead. At that point, all you really have to judge yaw divergence are the clouds you can see, and they are moving in the same airmass as you are, so it doesn't make any difference which way the wind is blowing.

True, but I pick up enough in my peripheral vision out the side windows that it helped me when i was green. YMMV

 

[Captain]

Whatever...slow flight isn't a ground reference maneuver for a reason. I'll say it again, the wind makes ZERO difference when performing slow flight. None. Zip and zero.

Heading? Ah no. Just look at an object on the horizon. The DPE isn't going to make you fly slow flight for 20 miles. You'll never get to the object. Pick the moon if it's visible if you're worried...but either way it's a non-factor.

Downwind to base? Doesn't affect you. Tailwind gust have the exact same effect as headwind gusts. The airplane doesn't know it's on downwind. A gust is a gust.


Listen to me and forget the others..."Once the plane is in the air you can FORGET about earth for purposes of how is the wind going to affect the plane". If you have to base your flight in reference to earth then that doesn't apply.

Referenced to ground: Wind has effect.
Not referenced to ground: Wind has ZERO effect. Even when people tell you it does..it doesn't.

 

[denverpilot]

Turbulence is wind.

 

[Henning]

"Once the plane is in the air you can FORGET about earth for purposes of how is the wind going to affect the plane". If you have to base your flight in reference to earth then that doesn't apply.

Referenced to ground: Wind has effect.
Not referenced to ground: Wind has ZERO effect. Even when people tell you it does..it doesn't.

It's not zero due to inertia, it's just negligible. The only place it shows up at all is at the edge of stall.

 

[Captain]

It's not zero due to inertia, it's just negligible. The only place it shows up at all is at the edge of stall.

No, it's zero when compared to which direction you fly. Turbulent air is turbulent air. Which way you fly has no effect. Are you more likely to momentarily stall in turbulent air during slow flight? Sure. But that's because the airmass you're in isn't stable. It make no difference which way you fly. Heading has zero effect on slow flight stalls caused by turbulence.

 

[timwinters]

When airborne the airplane does not know or care where the wind or gusts come from.

The airplane does not know or care where the (steady) wind comes from? True

The airplane does not know or care where the gusts comes from? False

 

[Clark1961]

Not referenced to ground: Wind has ZERO effect. Even when people tell you it does..it doesn't.

Never encountered wind shear?

Why don't you head over to BJC and fly awhile...

 

[Henning]

No, it's zero when compared to which direction you fly. Turbulent air is turbulent air. Which way you fly has no effect. Are you more likely to momentarily stall in turbulent air during slow flight? Sure. But that's because the airmass you're in isn't stable. It make no difference which way you fly. Heading has zero effect on slow flight stalls caused by turbulence.

Only if you are steady state, as soon as you add an acceleration force such as turning, or a veering gust of wind that no longer is true.

 

[Captain]

The airplane does not know or care where the (steady) wind comes from? True

The airplane does not know or care where the gusts comes from? False

Of course on a local level when the relative wind shifts the plane feels it. But 'wind' as measured by humans on the ground does not affect airplanes. Sure, turbulent air tosses a plane about. Lift rises and declines and local airflow increases and decreases. If your Vs speed is 73 kts and your indicating 73 kts in turbulence then you will be going into and out of stall. But that will happen regardless of heading.

 

[Captain]

Never encountered wind shear?

Why don't you head over to BJC and fly awhile...

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.

 

[Henning]

Of course on a local level when the relative wind shifts the plane feels it. But 'wind' as measured by humans on the ground does not affect airplanes. Sure, turbulent air tosses a plane about. Lift rises and declines and local airflow increases and decreases. If your Vs speed is 73 kts and your indicating 73 kts in turbulence then you will be going into and out of stall. But that will happen regardless of heading.

Yeah, right, it's only the acceleration moments that count for anything when airborne as far as flight is concerned; thing is, is when at slow flight where your margin is low enough, the acceleration could outpace inertia and you'll momentarily stall until your inertial vector catches up. This is the reality of the fabled 'downwind turn', this is all it is, the very coffin corner, and if you have 15' of altitude to give up, it's not a problem.

 

[Captain]

Only if you are steady state, as soon as you add an acceleration force such as turning, or a veering gust of wind that no longer is true.

I'm inclined to disagree. What happens in the air happens regardless of your orientation to the ground. The ground does NOT matter and by that I mean which way you're pointing with reference to the ground matters not.

 

[Captain]

Yeah, right, it's only the acceleration moments that count for anything when airborne as far as flight is concerned; thing is, is when at slow flight where your margin is low enough, the acceleration could outpace inertia and you'll momentarily stall until your inertial vector catches up. This is the reality of the fabled 'downwind turn', this is all it is, the very coffin corner, and if you have 15' of altitude to give up, it's not a problem.

You think 'coffin corner' has to do with the traffic pattern?

Look, you would be wise to listen to me instead of push your idea of what you think is right. Doesn't change a thing either way though.

 

[Henning]

I'm inclined to disagree. What happens in the air happens regardless of your orientation to the ground. The ground does NOT matter and by that I mean which way you're pointing with reference to the ground matters not.

You are discounting drag, gravity and inertia from the equation. The inertia of the plane is oriented in relationship to the Earths gravity well which is represented reasonably well by the surface, probably a few angular issues, but good enough. As the wind shifts it will have to act upon that inertia and for a plane at the verge of stall there may not be sufficient excess energy to carry you through. It's all very fractional.

 

[Captain]

I will say this one more time. Listen close.

Yes, in turbulent air at slow flight the aircraft may momentarily stall due to guests causing a momentary loss of lift. That's life flying on the edge of stall.

BUT IT HAS NOTHING TO DO WITH THE HEADING YOU ARE FLYING!!!

Your little downwind to base story is a result of flying too close to stall in turbulent air. I'd imagine it happens downwind to base more often than not is because that's when guys are slowing down. Crosswind to downwind speeds are up.

One more time...once the plane is in the air it does not care one little bit about the ground below it. The only time issues occur is when the pilot tries to align himself with the non-moving ground in a plane that's in a moving airmass.

Any more and I am really going to have to get paid for basic flight instruction.

 

[spiderweb]

I will probably be taking my checkride in the next couple of weeks, and have a question on slowflight. Is there any advantage to do the slowflight manuever into the wind if the examiner lets me pick my initial heading? My first thought was yes as it would be easier to get slowed up and the wind going over the wings would probably help maintain altitude. But, on second though, wouldn't the wind just effect groundspeed which should be irrelevant? So, is there any real advantage/disadvantage in starting slowflight upwind as opposed to downwind? Thanks.

Funkeruski, you got your answer at post #2.

 

[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.

 

[Clark1961]

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?

 

[Henning]

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]

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?

 

[Everskyward]

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).

 

[flyingcheesehead]

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!

 

[Henning]

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.

 

[Henning]

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]

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]

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.

 

[dmccormack]

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

 

[dmccormack]

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

Wind shear isn't wind?

 

[Captain]

Wind shear isn't wind?

Fine, FIFY.

 

[Everskyward]

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.