Wind shear, relative wind, airspeed and stalls

[MrManH]

Hey everyone,

Another question this time regarding aerodynamics.

I understand that the one and only thing that matters for stalls is the angle of attack, and that the airspeed at which it occurs is only relevant because we don't have an angle of attack indicator on most GA airplanes (although the FAA is pushing for GA planes to have them installed).

What has me confused is what is it about wind shear that really causes a stall?

If I'm flying straight and level and a shear knocks my airspeed below stall speed, will the airplane actually stall even though the angle of attack hasn't changed?

The momentary loss of airspeed results in a momentary reduction of lift, but if I let the airplane descend instead of pulling back on the control wheel, my angle of attack would remain unchanged and I wouldn't be stalled right? To me it seems like the stall would be pilot induced as he tries to fight the sink rate with increased back pressure.

Thanks!

 

[RoscoeT]

Your thinking is mostly correct, but...

If I'm flying straight and level and a shear knocks my airspeed below stall speed, will the airplane actually stall even though the angle of attack hasn't changed?

...don't think in terms of "airspeed below stall speed" causing a stall. Airspeed is irrelevant. AOA is. You can stall at higher than your "stall speed", or be unstalled while your airspeed is below your "stall speed". "Stall speed" only applies to unaccelerated 1G flight at a specific aircraft weight - which can vary.

Wind shear does not typically cause a stall. It can cause the airplane to descend momentarily, or a stall can be produced if a pilot attempts to arrest the descent by applying elevator. Think of a Cessna 152 flying into a 100 mph headwind. 100 mph airspeed, no ground speed. Now the wind instantly ceases. The pilot makes no inputs. Will the airplane stall? No. There has been no increase in AOA. The airplane will simply descend and gain airspeed. Wind doesn't typically cause much change in AOA. If you are flying very close to critical AOA, then swirling winds could possibly cause a momentary stall. Adding airspeed on final approach in gusty conditions is not so much to give you margin over stalling, but to provide more control over the sinking that can occur in gusty/wind shear conditions. Sinking and stalling are different things.

 

[Stewartb]

Hey everyone,

Another question this time regarding aerodynamics.

I understand that the one and only thing that matters for stalls is the angle of attack, and that the airspeed at which it occurs is only relevant because we don't have an angle of attack indicator on most GA airplanes (although the FAA is pushing for GA planes to have them installed).

What has me confused is what is it about wind shear that really causes a stall?

If I'm flying straight and level and a shear knocks my airspeed below stall speed, will the airplane actually stall even though the angle of attack hasn't changed?

The momentary loss of airspeed results in a momentary reduction of lift, but if I let the airplane descend instead of pulling back on the control wheel, my angle of attack would remain unchanged and I wouldn't be stalled right? To me it seems like the stall would be pilot induced as he tries to fight the sink rate with increased back pressure.

Thanks!

So you don't think relative wind has anything to do with it? To me it has everything to do with it.

 

[Mike Smith]

Its the critical angle TO the relative wind. If the wind changes so did the AOA.

 

[MrManH]

So you don't think relative wind has anything to do with it? To me it has everything to do with it.

Relative wind is opposite and parallel to the direction of flight. So sure if the wind comes to you at an angle and changes your direction of flight, the relative wind changes with it. But that doesn't mean the angle of attack will change unless the pilot introduces a correction right?

I've heard many people and read a lot of articles about stalling during wind shear, and I'm trying to confirm that it's actually pilot induced.

I guess it comes up a lot when talking about landings and takeoffs because operating so close to the ground, the pilot wants to keep the aircraft from hitting the ground and may exceed the critical angle of attack in doing so.

Let's use the following extreme example to keep things simple:
I'm flying straight and level in zero wind at 100MPH and all of a sudden I get a perfectly horizontal (parallel to my direction of flight) 100MPH tailwind. My airspeed momentarily drops to 0, what happens to the airplane during that small time frame?

 

[vkhosid]

Relative wind is opposite and parallel to the direction of flight. So sure if the wind comes to you at an angle and changes your direction of flight, the relative wind changes with it. But that doesn't mean the angle of attack will change unless the pilot introduces a correction right?

I've heard many people and read a lot of articles about stalling during wind shear, and I'm trying to confirm that it's actually pilot induced.

I guess it comes up a lot when talking about landings and takeoffs because operating so close to the ground, the pilot wants to keep the aircraft from hitting the ground and may exceed the critical angle of attack in doing so.

Let's use the following extreme example to keep things simple:
I'm flying straight and level in zero wind at 100MPH and all of a sudden I get a perfectly horizontal (parallel to my direction of flight) 100MPH tailwind. My airspeed momentarily drops to 0, what happens to the airplane during that small time frame?

In theory, your airspeed would drop to zero....the wings would stop producing lift because there is no air moving over them, your plane would drop straight down, and the RELATIVE WIND would be at about 90 degrees to the chord line of the wing....because relative to the plane, the air is moving up...

makes sense?


EDIT: This all assuming your plane doesn't pitch down, and maintains its same position on x,y, and z axes....which, realistically, won't ever happen.

 

[Capt. Geoffrey Thorpe]

Let's use the following extreme example to keep things simple:
I'm flying straight and level in zero wind at 100MPH and all of a sudden I get a perfectly horizontal (parallel to my direction of flight) 100MPH tailwind. My airspeed momentarily drops to 0, what happens to the airplane during that small time frame?

The air flow across your wing goes to zero, the wing stops delivering lift, and the airplane sinks which changes your angle of attack and you stall (unless you get the nose down just as fast as the wind changed - which you probably didn't).

 

[jsstevens]

Unless your airplane is one of the mythical physics "massless" examples, you have inertia so your airspeed would change for a time as well. Essentially your airspeed would drop to 0, the plane would begin to fall straight down, (AOA just became nearly 90 degrees), the nose would drop, airspeed would build up and the airplane would resume it's trimmed airspeed- if you have enough altitude.

If you are in a steady state wind, ground speed calculations, etc. are easy. But with wind shear your inertia comes into play before things steady out again. So an actual stall is possible with wind shear even without the pilot inducing it.

John

 

[Mike Smith]

Relative wind is opposite and parallel to the direction of flight. So sure if the wind comes to you at an angle and changes your direction of flight, the relative wind changes with it. But that doesn't mean the angle of attack will change unless the pilot introduces a correction right?

I've heard many people and read a lot of articles about stalling during wind shear, and I'm trying to confirm that it's actually pilot induced.

I guess it comes up a lot when talking about landings and takeoffs because operating so close to the ground, the pilot wants to keep the aircraft from hitting the ground and may exceed the critical angle of attack in doing so.

Let's use the following extreme example to keep things simple:
I'm flying straight and level in zero wind at 100MPH and all of a sudden I get a perfectly horizontal (parallel to my direction of flight) 100MPH tailwind. My airspeed momentarily drops to 0, what happens to the airplane during that small time frame?

You would have zero relative wind and therefore zero angle of attack and you would be sitting in a rock.

ETA, it would be 90 as mentioned above, not zero

 

[flyingron]

Your big problem is you are caught up with the idea that SPEED has something to do with it and possibly that you don't understand how lift works. The stall has nothing to do with not having enough lift to maintain level flight.

The stall is the point where further increase in AOA doesn't generate further increase in lift. Contrary to popular believe, the AOA->Lift curve is pretty symetrical at the tall point. With sufficient power, you can maintain level flight in a stalled attitude. The reason you don't usually see the AOA->Lift curve drawn much past the stall point is that the power required goes way up to make further plotting there unproductive.

A wind gust or shear except in some bizarre case will not cause a stall. Often it can cause an upset in stability which may result in you exceeding the critical AOA but even that is uncommon. The time it's most problematic is when you are close to the critical angle already. It may upset you enough to stall in that situation. Or if you're close to the ground as it may WITHOUT STALLING result in a decrease in lift that may be unwanted in that situation.

Full stall landings are indeed misnomers. It's near impossible to be in a stalled state in either conventional or tricycle gear with the mains touching the ground.

 

[MrManH]

The air flow across your wing goes to zero, the wing stops delivering lift, and the airplane sinks which changes your angle of attack and you stall (unless you get the nose down just as fast as the wind changed - which you probably didn't).

You're right, that's what I failed to visualize.

So let's use another example. Flying straight and level at 100MPH I get hit vertically by a microburst. The downdraft itself is forcing the airplane down, my airspeed is still indicating 100MPH but the wings are stalled since my direction of flight is almost vertical while my pitch attitude has remained unchanged. Correct?

 

[Silvaire]

...Let's use the following extreme example to keep things simple:
I'm flying straight and level in zero wind at 100MPH and all of a sudden I get a perfectly horizontal (parallel to my direction of flight) 100MPH tailwind. My airspeed momentarily drops to 0, what happens to the airplane during that small time frame?

The problem with hypothetical examples is that they aren't real and therefore don't actually happen. In this one we can start off by realizing that the "zero wind" condition is completely irrelevant because the aircraft in flight knows nothing of "wind". It is immersed in the air mass and the ground has no effect on it so even in a case of extreme wind shear as the air moves so does the aircraft and the only change in airspeed is due to inertia, it takes the mass of the aircraft a moment to catch up.

The air itself also has mass and inertia so it can't really just switch on and off like that but let's say you wandered into a thunderstorm where you could certainly experience severe wind shear. There could be a column of air rising at 2000 fpm next to a column of air descending at 2000 fpm with an extremely turbulent boundary layer between. Flying from one column to the other is going to alter your AOA even if you do nothing and yes, you could stall and it wouldn't be pilot induced.

 

[bflynn]

You're right, that's what I failed to visualize.

So let's use another example. Flying straight and level at 100MPH I get hit vertically by a microburst. The downdraft itself is forcing the airplane down, my airspeed is still indicating 100MPH but the wings are stalled since my direction of flight is almost vertical while my pitch attitude has remained unchanged. Correct?

No. The air you're flying in is moving downward, but you're still flying forward in that air. Relative to the ground you're moving 100 kts forward and 100 kts downward, so a 45degree angle. Your aircraft's attitude is flat. Relative to yourself, you're flying normal (in rough air) and the ground is moving upward quickly.

 

[MrManH]

The problem with hypothetical examples is that they aren't real and therefore don't actually happen. In this one we can start off by realizing that the "zero wind" condition is completely irrelevant because the aircraft in flight knows nothing of "wind". It is immersed in the air mass and the ground has no effect on it so even in a case of extreme wind shear as the air moves so does the aircraft and the only change in airspeed is due to inertia, it takes the mass of the aircraft a moment to catch up.

The air itself also has mass and inertia so it can't really just switch on and off like that but let's say you wandered into a thunderstorm where you could certainly experience severe wind shear. There could be a column of air rising at 2000 fpm next to a column of air descending at 2000 fpm with an extremely turbulent boundary layer between. Flying from one column to the other is going to alter your AOA even if you do nothing and yes, you could stall and it wouldn't be pilot induced.

Doesn't this contradict what others have been saying? I agree that the plane's inertia being greater than the air's is what causes the plane to lag behind, but during the time that it "catches" up, airspeed and lift are affected so the plane does "care" about what the wind does.

Regarding that 1/2 gust factor that we add on landing. I was always told that it's to provide a safe margin above stall speed? Would it be more correct to say that the lower angle of attack resulting from the increased airspeed puts us further away from the critical angle of attack? But then I'm not sure this makes complete sense because airspeed could also be increased by adding power.

No. The air you're flying in is moving downward, but you're still flying forward in that air. Relative to the ground you're moving 100 kts forward and 100 kts downward, so a 45degree angle. Your aircraft's attitude is flat. Relative to yourself, you're flying normal (in rough air) and the ground is moving upward quickly.

This makes sense, I agree 45 degrees and not "almost" vertical.

 

[bflynn]

The problem with hypothetical examples is that they aren't real and therefore don't actually happen. In this one we can start off by realizing that the "zero wind" condition is completely irrelevant because the aircraft in flight knows nothing of "wind". It is immersed in the air mass and the ground has no effect on it so even in a case of extreme wind shear as the air moves so does the aircraft and the only change in airspeed is due to inertia, it takes the mass of the aircraft a moment to catch up.

The air itself also has mass and inertia so it can't really just switch on and off like that but let's say you wandered into a thunderstorm where you could certainly experience severe wind shear. There could be a column of air rising at 2000 fpm next to a column of air descending at 2000 fpm with an extremely turbulent boundary layer between. Flying from one column to the other is going to alter your AOA even if you do nothing and yes, you could stall and it wouldn't be pilot induced.

The other consideration is that you won't instantly get a 100kt tailwind , instantly negating lift over your wing unless maybe if you're flying into a hurricane eye wall the wrong direction. Then you just don't fly in that direction.

For the next part, keep in mind the way the wings + stabilizer create a positive balance for the airplane. Also keep in mind that I'm working from memory rather than pulling out Stick and Rudder and my notes from PP ground school, so there's a chance I'll state something the wrong way. All it's doing is breaking down how the Angle of Attack comes to be from a CG and force/lever standpoint.

Wings and Stabilizer - the wings are large and generate a lot of lift, but they are near the CG, so operate on a short lever arm. The stabilizer is small but far away and operates on a longer lever arm. The wings are pushing up on a lever in front of the CG, the stabilizer is pushing up on a lever aft of the CG and the forces balance out, creating a stable attitude that the aircraft flies in. Keeping everything else equal, a nose up attitude causes nose down force and vice versa - creating the phugoid mode oscillations that students chase. This positive balance point defines the angle of attack that the airplane is trimmed for.

When you trim, what you're doing is slightly changing the chord of the stabilizer, causing a slight change in lift in the stabilizer and therefore a slightly different balance point between the fore and aft levers of the CG.

When airspeed decreases, such as from a strong tailwind gust, both wings and stabilizer generate less lift. Less relative airspeed causes less lift and the nose can't be held up anymore. The nose falls seeking to re-establish the balance point and the AOA that it is trimmed for. Now, if the airplane is flying close enough to stall speed AND that tailwind gust is strong enough, it could cause a stall by disrupting the lift and causing the airplane to stall - hopefully going into a nose down attitude where the acceleration will create a stall recovery easily.

 

[MrManH]

I'm updating my notes and drew something with exaggerated AOAs to illustrate the change, would you agree with the explanation?


Going back to Bernoulli’s principle, the higher the airspeed and the more lift is generated by the wings. An increase in headwind increases the airspeed (therefore the flow of air over the wings) resulting in an increase in lift. A lull or increase in tailwind reduces the airspeed and therefore reduces lift. During a headwind, more lift is created without changing the pitch of the airplane; the angle of attack is decreased despite climbing. When the wind shears to a tailwind, lift is reduced without changing the pitch of the airplane, the angle of attack is increased despite the descent.

 

[jsstevens]

Doesn't this contradict what others have been saying? I agree that the plane's inertia being greater than the air's is what causes the plane to lag behind, but during the time that it "catches" up, airspeed and lift are affected so the plane does "care" about what the wind does.
[snip]

It doesn't care what any steady state wind does, but, because of inertia, it does care about gusts or changes. Wind shear is where two adjacent air masses are moving in a different direction. The plane moves from one to the other and encounters a temporary change in air speed until it can stabilize out. Do that to close to the ground and you may crash before it can stabilize. If it's extreme enough (or you're close to the critical AOA already, like on final) you may stall before it stabilizes.

John

 

[MrManH]

I agree with everything you said. So am I right to say that the danger is that within the couple seconds that the airplane needs to stabilize, it may be stalled as a result of the change in relative wind?

Also let's talk about the purpose of adding a half gust factor during the approach. When I was taught about the gust factor, I was told it's to keep a safe margin above stall speed. But since stall speed isn't what actually causes the stall it has me wondering in what ways does increasing the airspeed in a descent attitude actually protect from a stall.

At first I was under the impression that if I increase my airspeed by solely adding power I will still have the same stalled AOA when the shearing tailwind or lull changes my relative wind. But going back to the conversation about descending at a 45 degree angle if I'm flying 100MPH into a 100MPH tailwind, the higher the airspeed and the less impacted my relative wind correct?

 

[Capt. Geoffrey Thorpe]

I'm updating my notes and drew something with exaggerated AOAs to illustrate the change, would you agree with the explanation?

In a downdraft, the air is moving downwards which reduces your angle of attack and accelerates the aircraft downward.

 

[MrManH]

In a downdraft, the air is moving downwards which reduces your angle of attack and accelerates the aircraft downward.

Would it though if I maintained the same attitude as during straight and level flight? Are you inferring that in a downdraft, the airplane (without any input from the pilot) would have a tendency to drop the nose as soon as the relative wind changes and therefore the angle of attack would be reduced?

 

[jsstevens]

I agree with everything you said. So am I right to say that the danger is that within the couple seconds that the airplane needs to stabilize, it may be stalled as a result of the change in relative wind?

Also let's talk about the purpose of adding a half gust factor during the approach. When I was taught about the gust factor, I was told it's to keep a safe margin above stall speed. But since stall speed isn't what actually causes the stall it has me wondering in what ways does increasing the airspeed in a descent attitude actually protect from a stall.

At first I was under the impression that if I increase my airspeed by solely adding power I will still have the same stalled AOA when the shearing tailwind or lull changes my relative wind. But going back to the conversation about descending at a 45 degree angle if I'm flying 100MPH into a 100MPH tailwind, the higher the airspeed and the less impacted my relative wind correct?

The half gust factor is so you're not sitting at the critical AOA on approach. A gust (because of all the inertia stuff discussed above) could cause you to either descend rapidly or exceed the critical AOA due to changes in the relative wind because of the gust.

John

 

[Capt. Geoffrey Thorpe]

Would it though if I maintained the same attitude as during straight and level flight? Are you inferring that in a downdraft, the airplane (without any input from the pilot) would have a tendency to drop the nose as soon as the relative wind changes and therefore the angle of attack would be reduced?

I'm saying that the direction of the air flow changes (otherwise it wouldn't be a downdraft). And, it changes in a direction that reduces your angle of attack.

 

[MrManH]

Thanks again for the reply. While I process all the information I have one last question. When the wind is shearing, will the airspeed indicator still be a reliable indicator of my angle of attack? For instance if my Vs0 is 50kts, and my airspeed moves back and forth down to 51kts but never below, I will never be stalled correct?

 

[MrManH]

I'm saying that the direction of the air flow changes (otherwise it wouldn't be a downdraft). And, it changes in a direction that reduces your angle of attack.

I have no doubt that you're right but I am visualizing the exact opposite.
At first you're flying straight and level, let's say your chord line is parallel to the relative wind (to keep things simple), therefore your AOA is 0.

All of a sudden you get hit by a wind that pushes you down. You still have the same attitude as earlier but now your direction of flight/relative wind is descending, how does that not increase your AOA?

 

[Capt. Geoffrey Thorpe]

Thanks again for the reply. While I process all the information I have one last question. When the wind is shearing, will the airspeed indicator still be a reliable indicator of my angle of attack? For instance if my Vs0 is 50kts, and my airspeed moves back and forth down to 51kts but never below, I will never be stalled correct?

Airspeed is never a reliable indicator of angle of attack.

The speed at which you stall depends on how much load is on the wing.

 

[MrManH]

Airspeed is never a reliable indicator of angle of attack.

The speed at which you stall depends on how much load is on the wing.

Right but can we assume we are doing all this at 1G to take wing loading out of the equation?

 

[Stewartb]

You should have been around yesterday. I'd have taken you for a ride into a small short strip with the wind blowing about 30 and shifting. If the wind wasn't enough the surroundings made mechanical turbulence a real treat down low. I'm more in the camp of keep the approach high and steep and adjust the attitude to maintain airspeed. Aim for touchdown a little downfield of the numbers to allow for an accelerated sink rate and things usually work out just fine. Going back out is more unnerving. Clawing for airspeed and altitude while the winds are rolling over terrain gets my full attention every time.

 

[exncsurfer]

I'm updating my notes and drew something with exaggerated AOAs to illustrate the change, would you agree with the explanation?

To comment on your drawing, I think you have the flight path right, but you didn't draw the relative wind. You drew the AOA arcs relative to the flight path instead of relative wind. For example in your microburst example, you're relative wind would be coming from above moving down across the top of the wing making a negative AOA. (right?)

You're increased head wind would act like increased thrust (climb), you're tailwind would act like reduced thrust(decent). You're microburst would act like you shoved the stick forward. (right?) All of these would be very temporary conditions while the conditions stabilize. yes? no?

 

[MrManH]

That sounds like a fun time. A couple days ago I was coming back into midway airport with winds gusting in the mid 20s, the ATIS changed 3 times while on final and then a LLWS alert was issued. I like approaching high as well, one of the reasons being that Midway is in the middle of a Chicago neighborhood and flying the 3 degree visual glide slope puts you really close to houses on final; lose the engine or get hit by wind shear and you may land on someone's house.

 

[MrManH]

To comment on your drawing, I think you have the flight path right, but you didn't draw the relative wind. You drew the AOA arcs relative to the flight path instead of relative wind. For example in your microburst example, you're relative wind would be coming from above moving down across the top of the wing making a negative AOA. (right?)

You're increased head wind would act like increased thrust (climb), you're tailwind would act like reduced thrust(decent). You're microburst would act like you shoved the stick forward. (right?) All of these would be very temporary conditions while the conditions stabilize. yes? no?

To me the relative wind is basically the same as the direction of flight since they're always parallel, just opposite directions.

I agree with the bold but I'm not sure about the microburst being like shoving the stick forward in terms of the airplane's attitude. I've always stayed out of rain shafts and virga haha so I don't know how the plane reacts about its lateral axis when hit by a downdraft. If the airplane pitches down automatically then I can see how the AOA is reduced.

 

[exncsurfer]

To me the relative wind is basically the same as the direction of flight since they're always parallel, just opposite directions.

I agree with the bold but I'm not sure about the microburst being like shoving the stick forward in terms of the airplane's attitude. I've always stayed out of rain shafts and virga haha so I don't know how the plane reacts about its lateral axis when hit by a downdraft. If the airplane pitches down automatically then I can see how the AOA is reduced.

Yea, I think you're right, I remember my cfi now saying that flight path/relative wind, same thing. I guess its just confusing in your examples because you're looking at a point where its all changing depending on what instant you're looking at. Because it'll take some time for the flight path to react to your theoretical gust(relative wind change of direction).

 

[warthog1984]

Easy concept- wind shear will not cause a stall. It Will remove most of your lift and so you drop like a rock until a steady stable decent is reached- sometimes at very large fpm Down!

 

[MrManH]

I am reviving this thread because I have a couple follow up questions.

Was the general consensus that theoretically it is possible for a sudden tailwind to stall the airplane since the airplane won't pitch down as fast as the relative wind changes and the critical AOA could be exceeded?

Now, if we bring load factor into this discussion. In a sudden headwind, airspeed is momentarily increased, therefore lift is also increased which should result in a higher load factor, correct? But it would also make sense to me that without any input from the pilot the AOA in a headwind would be decreased due to the change in relative wind. Since lift is the product of both airspeed and AOA, if airspeed goes up but AOA goes down, do they basically cancel each other out and the load factor remains around 1G?

Thanks!

 

[flyingron]

Was the general consensus that theoretically it is possible for a sudden tailwind to stall the airplane since the airplane won't pitch down as fast as the relative wind changes and the critical AOA could be exceeded?

You've lost me. Why would you need to pitch down? While the magnitude of the relative wind changes, the direction, which is all that matters for stalling, wouldn't.

In a sudden headwind, airspeed is momentarily increased, therefore lift is also increased which should result in a higher load factor, correct?

Possibly. This is one of the reasons you have a yellow arc on your airspeed indicator. What happens is the airplane enters a climb/descent due to the acceleration.

 

[dtuuri]

In a sudden headwind, airspeed is momentarily increased, therefore lift is also increased which should result in a higher load factor, correct? But it would also make sense to me that without any input from the pilot the AOA in a headwind would be decreased due to the change in relative wind.

My emphasis. Without help from the pilot the airplane will try to maintain the same angle of attack because that's the way the horizontal tail has been trimmed. The same thing would happen if you dove the plane without trimming and then sudenly released the controls.

dtuuri

 

[coloradobluesky]

A gust of wind changes the plane's airspeed until some time passes and it goes back to the steady state airspeed it was at. If the gust comes from behind, the airspeed goes down. Stall speed is dependent on airspeed (although it is true you CAN stall at high airspeed, normal non accelerated stalls are at low airspeed). So the airspeed goes down with a gust of wind from behind and the planes airspeed goes down, temporarily. Wind shear is just wind changing direction quickly, gusts of wind and wind shear really the same thing.

 

[luvflyin]

Hey everyone,

Another question this time regarding aerodynamics.

I understand that the one and only thing that matters for stalls is the angle of attack, and that the airspeed at which it occurs is only relevant because we don't have an angle of attack indicator on most GA airplanes (although the FAA is pushing for GA planes to have them installed).

What has me confused is what is it about wind shear that really causes a stall?

If I'm flying straight and level and a shear knocks my airspeed below stall speed, will the airplane actually stall even though the angle of attack hasn't changed?

The momentary loss of airspeed results in a momentary reduction of lift, but if I let the airplane descend instead of pulling back on the control wheel, my angle of attack would remain unchanged and I wouldn't be stalled right? To me it seems like the stall would be pilot induced as he tries to fight the sink rate with increased back pressure.

Thanks!

Take it to the extreme. Imagine a shear where the airspeed suddenly goes to Zero. Now there is no lift. Gravity takes over and the plane now goes straight toward the center of the earth. Well, not really, you do have some momentum. But imagine the airplane still level but going straight down, not nosed over, just straight down while the deck (and the chord of the wing) are parallel to the earth. The relative wind is now 90 degrees to the wing. That's a lot of angle of attack. Now of course the plane can't change from going forward to straight down (doing a belly flop so to speak) and having a 90 degree angle of attack instantly, but maybe for a few seconds, before the the pilot inputs any control pressures, before the airplane starts nosing over on its own, the critical angle of attack is exceeded. I dunno. Engineers???????????

 

[bobmrg]

It's time for you and your instructor to go flying with the airspeed indicator covered. Heck, hang a towel over the whole panel.

Bob Gardner

 

[1RTK1]

Better yet have your instructor, on a night flight, turn off the panel lights along with the landing lights, then tell you to land the plane. My CFI did it to me, then signed me off for solo night flight.

 

[RotorDude]

Better yet have your instructor, on a night flight, turn off the panel lights along with the landing lights, then tell you to land the plane. My CFI did it to me, then signed me off for solo night flight.

Any runway lights?