No bounce landing

[photofly]

Regarding the definition of stall for airplanes that are controllable well into the stall, I always taught it as the aircraft is "stalled" when the wing has exceeded the critical angle of attack AND is producing less lift than gravity is exerting on the aircraft.

That’s not a helpful criterion.

Oftentimes the wing produces less lift than the weight of the aircraft, when the aircraft is far from stalled. Any time the aircraft is in a climb, for example, when there is a vertical component of thrust.

And when the airplane is a steady non-stalled descent, there is a significant upward vertical component of drag, so the lift, again, is less than the weight.

I believe that what you mean to say is that the forces on the aircraft are unbalanced when the airplane stalls, but even that is not true: for as long as the vertical speed and airspeed remain steady, all forces are balanced and constant. It is possible for this to be so even if the AoA is beyond the critical AoA and the aircraft is “stalled”.

As you note, controllability, stability, and stall are three different things.

[GoinVertical]

Regarding the definition of stall for airplanes that are controllable well into the stall, I always taught it as the aircraft is "stalled" when the wing has exceeded the critical angle of attack AND is producing less lift than gravity is exerting on the aircraft.

That’s not a helpful criterion.

Oftentimes the wing produces less lift than the weight of the aircraft, when the aircraft is far from stalled. Any time the aircraft is in a climb, for example, when there is a significant vertical component of thrust.

And when the airplane is a steady non-stalled descent, there is a significant upward vertical component of drag, so the lift, again, is less than the weight.

I believe that what you mean to say is that the forces on the aircraft are unbalanced when the airplane stalls, but even that is not true: for as long as the vertical speed and airspeed remain steady, all forces are balanced and constant. It is possible for this to be so even if the AoA is beyond the critical AoA and the aircraft is “stalled”.

When the wing is no longer producing enough lift to meet or exceed the force of gravity AND has exceeded the critical angle of attack.

[photofly]

But The conjunctive clause is simply wrong. When the wing exceeds the critical angle of attack it is stalled, regardless of the amount of lift it produces.

It is not “unstalled” if it exceeds the critical angle of attack but somehow does produce more lift than the weight of the aircraft. Which it could, under some unusual circumstances.

[digits_]

I was about to write the same thing, but I have some trouble coming up with a clear example where lift would exceed weight in a stalled airplane.

[GoinVertical]

But The conjunctive clause is simply wrong. When the wing exceeds the critical angle of attack it is stalled, regardless of the amount of lift it produces.

It is not “unstalled” if it exceeds the critical angle of attack but somehow does produce more lift than the weight of the aircraft. Which it could, under some unusual circumstances.

I was responding to corethatthermal and AuxBatOn's discussion about stalling vs mushing vs technical definition in "Hershey bar wing" aircraft. Some students, and even some pilots with experience, have trouble identifying a stall when there is no obvious nose drop, wing drop, buffet, etc, especially if they've got a few dozen hours in airplanes that have a prompt nose drop at stall.

I'm not arguing with the technical, aerodynamic, definition of a stall.

[photofly]

I was about to write the same thing, but I have some trouble coming up with a clear example where lift would exceed weight in a stalled airplane.

Lift depends on angle of attack but also airspeed. If you can push a plane fast enough you can develop as much lift as you want, even though the wing is stalled.

Typically there would be stability issues with maintaining flight like that, but that would be a separate matter.

It’s also worth noting that other than transiently, you don’t get a free choice of how much lift a wing creates. If you push a plane faster so the lift increases, it will accelerate upwards so reducing the angle of attack, until the lift decreases, the forces come back into equilibrium and a new steady state is assumed.

I was just reading a NASA online book (it’s free) about the X31 which was designed to experiment with manoeuvring a post stall aircraft.

[photofly]

I was responding to corethatthermal and AuxBatOn's discussion about stalling vs mushing vs technical definition in "Hershey bar wing" aircraft. Some students, and even some pilots with experience, have trouble identifying a stall when there is no obvious nose drop, wing drop, buffet, etc, especially if they've got a few dozen hours in airplanes that have a prompt nose drop at stall.

I agree. I think the best way though the difficulty is to teach an appreciation of angle of attack, so pilots can discern when it’s clearly too high. Pitch and/or roll instability is a symptom of a stalled wing, but not determinative; high AoA is determinative. Why not teach that?

[AuxBatOn]

Where’s the AoA gauge in most aircraft?

The important part is understanding that yes, AoA is what theoratically defines stalls and for flight with more than 1g (like in a turn) the aircraft will stall at higher airspeed than published.

What’s most important is knowing what defines stall in your aircraft. We, test pilots, go at great lengths to characterize this and publish it in the AFM in pilot speak. During initial type training, this should be at least demonstrated under various conditions.

[photofly]

Where’s the AoA gauge in most aircraft?

Angle of Attack is very simple: it's the difference between the direction the aircraft is pointing and the direction the aircraft is moving through the air (in the vertical plane as the pilot sees it. In the horizontal plane the difference between the same things is the sideslip angle, which is also important).

You can tell which way the aircraft is pointing by looking out of the window. You can tell which way the aircraft is travelling by combining what the ASI, altimeter and VSI are telling you. You don't need an AoA gauge to tell what your AoA is.

If you want to sum up the technical skill of piloting an airplane in a few lines, that's it.

In point of fact, you can read your AoA directly off the ASI if you know (or are willing to estimate) what your g force is.

[AuxBatOn]

Where’s the AoA gauge in most aircraft?

Angle of Attack is very simple: it's the difference between the direction the aircraft is pointing and the direction the aircraft is moving through the air (in the vertical plane as the pilot sees it. In the horizontal plane the difference between the same things is the sideslip angle, which is also important).

You can tell which way the aircraft is pointing by looking out of the window. You can tell which way the aircraft is travelling by combining what the ASI, altimeter and VSI are telling you. You don't need an AoA gauge to tell what your AoA is.

If you want to sum up the technical skill of piloting an airplane in a few lines, that's it.

In point of fact, you can read your AoA directly off the ASI if you know (or are willing to estimate) what your g force is.

What's the critical AoA on your aircraft? What about a 777? Sure you can estimate AoA but you can’t for every type, determine with precision where the aircraft is in relation to the critical AoA, hence the importance of learning individual aircraft’ behaviour during stalls (both unaccelerated and accelerated). Do you think that if they had recognized the symptoms of a stall on their aircraft, the Air France pilots over the Atlantic would have stalled and maintain pro-stall inputs for more than 35,000 ft to their death?

[AuxBatOn]

In point of fact, you can read your AoA directly off the ASI if you know (or are willing to estimate) what your g force is.

Nope, i fly with a precise G-meter and still rely on the AoA indicator for precise and accurate AoA. I can feel approaching the critical AoA with how the aircraft feels (buffet and stick position) but not with ASI and G-meter alone. This allows me to look out (instead of in) and still have a very precise idea of where I am in relation to the critical AoA.

[AuxBatOn]

Straight from the US Navy Flight Test Manual 103:

The classical stall may be defined as a condition in which the airplane wing is subjected to an angle of attack greater than the angle for maximum lift coefficient. Stall speed can be defined as the minimum steady airspeed attainable in unaccelerated flight or the minimum usable airspeed. However, characteristics exhibited by many airplanes in the region of the stall preclude attainment of the classic aerodynamic stall. These characteristics vary widely among different airplanes and are greatly affected by a multitude of factors.

Also, give 2.2.7 a read...

http://www.usntpsalumni.com/Resources/D ... TM_103.pdf

[photofly]

I do not deny that experience with flight on the edge of a stall, and through a stall, is extremely valuable, as the experience differes for different types, and for different ways the stall is reached on the same type.

Nevertheless, the definition of a stall doesn't depend on the response of a particular aircraft on a particular day, and recognizing a high angle of attack can still be done without knowledge of or reference to expertly written type-specific documentation.

Nope, i fly with a precise G-meter and still rely on the AoA indicator for precise and accurate AoA.

That is marvellous. It is still true that in aircraft without a AoA indicator and without a G-meter, which is almost all of them, you can appreciate your AoA at any given g-force by looking at the ASI.

Gaining a feeling for AoA should not be taught as something that requires reading a flight manual or having a special indicator to read it on. It's more fundamental than either of those things, valuable as they are.

Do you think that if they had recognized the symptoms of a stall on their aircraft, the Air France pilots over the Atlantic would have stalled and maintain pro-stall inputs for more than 35,000 ft to their death?

I think if they had been able to recognize a high AoA on *any* aircraft, by the way I described, even if they had never before sat in the cockpit of an Airbus, they would have saved a bunch of lives. Because they were concentraing on symptoms, rather than on basics, they didn't recognize the stall. Nobody should ever say to themselves, "I am unable to recognize a stall in this aircraft type because I've forgotten what the manual said the symptoms are."

[AuxBatOn]

So, tell me, what is an excessive AoA, in practical terms, as defined by looking inside? Assume you are IMC.

[photofly]

You’re a very smart guy: you can list as many ways to recognize a high angle of attack as I can, both by looking inside, by looking outside, and often by control feel too.

I don’t believe for an instant that you think recognizing a stall can only be done, or must be done, after consultation with the flight manual, so I’m not sure why you’re arguing.

Going back to the point of this thread, we can both recognize (well, Captain Underpants did, let’s give him credit - I needed prodding) that the aircraft in the video appears to have had an angle of attack that was too high for a safe landing, using less information than the pilot had in from of him/her, and I’ve never sat in a Seminole, still less read the flight manual of one.

[corethatthermal]

What we know : The pilot shut down both engines but failed to feather the props, then decided not to restart . NOW, the pilot finds he is barely making it to the airport and so he tries to find a speed for best glide.... Unfortunately, that speed is in a low energy state with no energy to flare and I think he knows that. I suspect that he didn't aggressively try to flare because he knew he would "stall" the plane and cause injuries. ( If his energy state/airspeed was low enough, flaring would have INCREASED the rate of descent )
Obviously, on approach, the planes wing was not "stalled" He was basically just on the backside of the power curve without the required thrust to make a successful flare. IF he was well into the backside, then he would need thrust to SLOW down more!

[corethatthermal]

Looking closely at the video, it appears he tried twice to test the aircraft WRT its response after a pitch-up and as we can see, it was worse than he likely expected and so therefore he didn't try to flare, he already knew what would happen because he already tested the A/C energy state on approach!

[Ki-ll]

So, tell me, what is an excessive AoA, in practical terms, as defined by looking inside? Assume you are IMC.

Would stick/control column deflection be a good enough indicator?

[digits_]

Obviously, on approach, the planes wing was not "stalled" He was basically just on the backside of the power curve without the required thrust to make a successful flare. IF he was well into the backside, then he would need thrust to SLOW down more!

If photofly's data is correct, the was damn well as far into the backside as he can get. No you don't need thrust to slow down more. He was descending. He would just be descending steeper, which I think is exactly what happened, as the video seemed to show.

If he was maintaining his regular approach speed, which is just around the negative peak in the power curve, he would have had enough energy to at least attempt to flare.

[AuxBatOn]

So, tell me, what is an excessive AoA, in practical terms, as defined by looking inside? Assume you are IMC.

Would stick/control column deflection be a good enough indicator?

If you re-read some of my earlier post, stick/control column can be used as a stall definition.

[digits_]

So, tell me, what is an excessive AoA, in practical terms, as defined by looking inside? Assume you are IMC.

Would stick/control column deflection be a good enough indicator?

If you re-read some of my earlier post, stick/control column can be used as a stall definition.

That is a terrible stall definition. I can be stalled or unstalled at any control column position/deflection. It highly depends on the context, or how you ended up in that position. But if you knew that, you probably wouldn't be trying to figure out if you are in a stall...

[iflyforpie]

Your AoA indicator on most aircraft is the stall warning vane. Or buffet. They work at any weight, any configuration (though some aircraft have to have multiple vanes for different flap settings), any speed or wing loading. They don’t always work when a plane is iced up.. but neither will an AoA vane, either.

It won’t tell you other angles of attack.. like for best climb or glide. For most aircraft these are done at 1G and airspeed is close enough for those.

It’s also worthy to note that AoA won’t solve everything. If you’re low, below your aircraft’s 1G stall speed, but maintaining an AoA for best L/D... you’re probably going to hit the ground violently.

With AF447... you had a pilot who had lost control of the aircraft and was “going back home to momma” hoping that Alpha Protect and Alpha Floor would help him climb again just below the critical angle of attack while commanding increased engine thrust... not realizing those had been disabled after the aircraft had reverted to Alternate Law. The aircraft was in such a deep stall that the AoA vane no longer registered a stall... and any relaxation on the side stick would cause the stall warnings to sound—completely opposite of what you’d expect. Compounding the issue was the lack of tactile feedback on the left side stick and the inattention of the PM to the position of the right stick.

[Ki-ll]

Would stick/control column deflection be a good enough indicator?

If you re-read some of my earlier post, stick/control column can be used as a stall definition.

That is a terrible stall definition. I can be stalled or unstalled at any control column position/deflection. It highly depends on the context, or how you ended up in that position. But if you knew that, you probably wouldn't be trying to figure out if you are in a stall...

I’d disagree. Airplane would stall at roughly the same stick/control column position most of the time. So if you find yourself pulling hard back on the controls you should know that you are close to the stall.
While the best and a most precise indicator of the stall would be an AoA indicator even having one in front of you won’t prevent a stall.
This crew wasn’t saved by it and Tu-154 has an indicator, flasher and an aural warning.
https://en.m.wikipedia.org/wiki/Pulkovo ... Flight_612

[digits_]

I’d disagree. Airplane would stall at roughly the same stick/control column position most of the time. So if you find yourself pulling hard back on the controls you should know that you are close to the stall.

Following that traing of logic, if full aft position of the controls equals "stall", why does the manufacturer allow pilots to move the controls fully aft? Why not limit the control to the "not stalling" range?

[AuxBatOn]

Would stick/control column deflection be a good enough indicator?

If you re-read some of my earlier post, stick/control column can be used as a stall definition.

That is a terrible stall definition. I can be stalled or unstalled at any control column position/deflection. It highly depends on the context, or how you ended up in that position. But if you knew that, you probably wouldn't be trying to figure out if you are in a stall...

For 1g, it may be all you get, beyond artificial stall warnings.