Update on 3407

[wheelsup]

The EMB-145 would also require some back pressure when you went full power during a stall recovery, partly because of where the engines were, but also because of the direction the thrust went (down, the engines are angled). It was counter intuitive, but I think the point was to, as you said, minimize altitude loss until you could get the thing cleaned up and climbing.

Yeah the increased thrust pitches the nose down rapidly, however they really did stress not losing any altitude vs. not stalling.

 

[tgrayson]

If one holds the pitch angle the same while increasing speed that means that one is making pitch adjustments. I would think that goes without saying, yet here I am saying it.

It means one is reducing the AoA, yes. It should go without saying, but you claimed to be able to reduce the AoA through airspeed, yet you're doing exactly the reverse. The device that you're using to control the pitch attitude (yoke) is what is producing the AoA decrease (hence airspeed change) and unstalling the airplane. The thrust mainly allows you the luxury of reducing the AoA without hitting the ground.

As long as you're doing both, not so big a deal, but often pilots get stuck on the power and forget to use the yoke appropriately, and they hit the ground. (probably mostly a GA problem, although some jets have bit the dust in a similar fashion.)

 

[tgrayson]

My equally unqualified understanding is that the argument against reducing AoA is that you don't want to go down any more than you already are/have.

Note that when a lot of these guys talk about stall recovery, they're talking about recovering at the stick shaker, when the aircraft isn't actually stalled. I would assume that all of these airplanes have sufficient thrust to climb in this condition, which reduces the need for an immediate AoA reduction.

 

[MikeD]

As long as you're doing both, not so big a deal, but often pilots get stuck on the power and forget to use the yoke appropriately, and they hit the ground. (probably mostly a GA problem, although some jets have bit the dust in a similar fashion.)

No, you're right, it's a jet problem too. The T-38 in the final turn/overshooting accident is a good example. As the pilot gets slow and begins raking on the Gs and rolling more in order to prevent an overshoot of the runway, the plane begins sinking.....rapidly and unnoticiably. Unnoticably because when you're approaching/in a stall in that jet, the nose stays where it is, the only indications from the plane being the "dancing elephants" on the wings and the severe downward VVI. If a guy doesn't notice it, the last thing he'll likely see is the ground coming up all around him...with nose still at/above the horizon. If he does notice it and recovers wrong, it's normally because he relaxed the Gs, rolled the plane out of the turn and went max afterburner (all correct), but didn't lower the nose due to the ground rush, the result being the plane still mushing to the ground because it never had to chance to break the stall (depending how deep the stall was), since the pilot didn't accept a small loss of altitude (by giving some forward stick) in order to effect the recovery. Granted this is all happening in seconds, but there's a big emphasis in training for this due to the historical number of accidents the aircraft has had in this phase of flight.

Would the plane have recovered using throttle only and no change in pitch to help break the stall? Sure. Just not with the small bit of AGL altitude there was, along with the downward vector already, in the final turn. Had the same scenario been accomplished at, say, 3000 AGL (arbitrary number), the plane would've eventually powered-out of it. I agree with you that as close to the ground as one is in the final turn (and descending rapidly), the pilot has to lower the nose and accept some more loss of altitude in order for the recovery and power to take effect quicker. This might be a fair loss of altitude, but you're already dead in this situation.....anything you do to help yourself is a bonus.

As this relates to a 3407-style phase of flight, this recovery should be easier to effect since on an ILS approach, the rate of descent isn't very rapid, thus the altitude lost in a "relax (stick), max (power), roll (level)" recovery shouldn't be much, if at all.

 

[jynxyjoe]

It means one is reducing the AoA, yes. It should go without saying, but you claimed to be able to reduce the AoA through airspeed, yet you're doing exactly the reverse. The device that you're using to control the pitch attitude (yoke) is what is producing the AoA decrease (hence airspeed change) and unstalling the airplane. The thrust mainly allows you the luxury of reducing the AoA without hitting the ground.

As long as you're doing both, not so big a deal, but often pilots get stuck on the power and forget to use the yoke appropriately, and they hit the ground. (probably mostly a GA problem, although some jets have bit the dust in a similar fashion.)

I think I'm getting there but I'm gonna need another push on my swing.

I need to confirm first off we agree on the simpler side, that A in both my Aero classes must have been meant for another student.

We seem to agree on this point
scenario 1: Classic stall routine. Slow aircraft, pitch up to keep altitude. Then the magic shaker (not the stall as you said). We recover from the shaker by adding power and pitching to lose the least altitude possible. For the recovery I instead elect to hold pitch the same and add that power, the plane will speed up and relative wind/angle of attack will drop and I recover. Pitch remains the same, power and airspeed increase which removes the condition which started the shaker. By the way, it's important that I say again this is theoretical and this is not an approved method by my company or something I'd use. That is why I keep saying things like "all things being equal". Real world the plane is gonna do something to you to screw this all up.

It seems like we agree on that scen 1. If not then there is no point to the rest but I'll assume that and move on.

What we actually want to talk about is the deep stall or "real stall".

Scenario 2: Slow aircraft, get into shaker and now you are past shaker and into pusher land, now your past (well still in I guess) pusherland and in deep stall. You are saying that you can not power out of this? Only solution is a pitch change (down) to, for lack of a better term, "break" the stall?

 

[tgrayson]

Granted this is all happening in seconds, but there's a big emphasis in training for this due to the historical number of accidents the aircraft has had in this phase of flight.

I remember reading about a few of them; do you know where any accident reports of these events are located? I'd love to have them on file. It's a great talking point to say "if this can happen to a jet fighter, it can happen to you."

 

[MikeD]

I remember reading about a few of them; do you know where any accident reports of these events are located? I'd love to have them on file. It's a great talking point to say "if this can happen to a jet fighter, it can happen to you."

I have a good synopsis on these accidents. Its in print form, so I'd have to mail it to you. In any initial training in the AF, one of the things you're given is a compilation of (releasable, no priviliged information) accidents particular to that airframe throughout the years. It's really good reading and learning...and I still have mine for the T-37/38, as well as the A-10. Very interesting stuff, and good points taken out....from pilot error, to mechanical, to WX.....no one is really immune, unfortunately.

PM me and I'll send it to you.

EDIT: wrote some more to my previous post above.

 

[tgrayson]

For the recovery I instead elect to hold pitch the same and add that power, the plane will speed up and relative wind/angle of attack will drop and I recover.

I agree this will happen, but I object to part of your explanation...you're attributing the AoA recovery to the increased airspeed. I'm saying it's the reverse. The reason is that the pitching moments aound your CG are only in equilibrium at the trimmed AoA/Airspeed. If you are even *briefly* successful in increasing your airspeed with thrust, the aircraft will pitch up to restore the trimmed AoA, so the problem will follow you around like gum on the bottom of your shoe.

The reason that your airspeed eventually recovers is that in an effort to maintain the same attitude, you are forced to push or pull on the yoke, which produces an AoA/airspeed change. When these things happen very closely in time, the causal relationship is a bit unclear and perhaps not meaningful, as long as both actions *do* happen.

BTW, this isn't just speculation on my part....I've got the formulas in dozens of books which show how to calculate the equilibrium AoA on an aircraft. Thrust only enters into the equation via its distance from the CG, due to the pitching effect that I mentioned. If the distance is zero, then thrust has no effect.

What we actually want to talk about is the deep stall or "real stall".

I wouldn't call that a deep stall, which is something else, but agreed, you cannot power out of this, because the stall is caused by excessive elevator. As long as the elevator remains in the same position, the stall AoA will persist. Again, assuming no pitching moment produced by thrust. In something like the CRJ, I understand there is a nose down pitching moment upon thrust application which would act to reduce the AoA. In something like a C172, there tends to be a nose up tendency on the application of power.

 

[Champcar]

Stall recovery in the Q is pretty much tought to unleash the motors, while holding on. The area where I've seen stuff go wrong is that F'in Yaw dampner. On a normal change from cruise or descent to climb power, it will give you nearly full ball deflection, and you really have to use your feet. Going from Flight Idle to full overtravel at a very slow airspeed would be a monster to get a handle of. You would need fast, and heavy rudder imput to keep it centered... which if flying on autopilot, the likelyhood of your feet being on the rudder pedals is slim. I also know that it took me at least a good 100 hours to get used to stepping on a rudder every time i change power, even with the yaw dampner on. I'm sure most of you can see where I'm going with this, so I will stop there.

That is what gets me about the whole thing. I have a hard time believing they over reacted to the stall AND lost directional control that fast.At that point in their carriers and with enough time in the aircraft these things should just be second nauture. It just doesn't add up for me, guess I have too much faith in pilots.

 

[tgrayson]

Would the plane have recovered using throttle only and no change in pitch to help break the stall? Sure. Just not with the small bit of AGL altitude there was, along with the downward vector already, in the final turn. Had the same scenario been accomplished at, say, 3000 AGL (arbitrary number), the plane would've eventually powered-out of it.

I don't think this is a proper interpretation of what's occurring. First of all, the use of the word "pitch" is not meaningful, and is the cause of a whole host of misunderstandings. "Pitch" does not control airspeed nor does it cause or break a stall. AoA does. Pitch is a combination of climb angle and AoA. If you're climbing out at a 10 degree flight path, and have an AoA of 5 degrees, then you have a pitch attitude of 15 degrees.

What I really think you're saying is that these aircraft had sufficient thrust to initiate a climb that would have allowed an AoA reduction.

 

[jynxyjoe]

I agree this will happen, but I object to part of your explanation...you're attributing the AoA recovery to the increased airspeed. I'm saying it's the reverse. The reason is that the pitching moments aound your CG are only in equilibrium at the trimmed AoA/Airspeed. If you are even *briefly* successful in increasing your airspeed with thrust, the aircraft will pitch up to restore the trimmed AoA, so the problem will follow you around like gum on the bottom of your shoe.

The reason that your airspeed eventually recovers is that in an effort to maintain the same attitude, you are forced to push or pull on the yoke, which produces an AoA/airspeed change. When these things happen very closely in time, the causal relationship is a bit unclear and perhaps not meaningful, as long as both actions *do* happen.

BTW, this isn't just speculation on my part....I've got the formulas in dozens of books which show how to calculate the equilibrium AoA on an aircraft. Thrust only enters into the equation via its distance from the CG, due to the pitching effect that I mentioned. If the distance is zero, then thrust has no effect.



I wouldn't call that a deep stall, which is something else, but agreed, you cannot power out of this, because the stall is caused by excessive elevator. As long as the elevator remains in the same position, the stall AoA will persist. Again, assuming no pitching moment produced by thrust. In something like the CRJ, I understand there is a nose down pitching moment upon thrust application which would act to reduce the AoA. In something like a C172, there tends to be a nose up tendency on the application of power.

Follow those bolds above if you can. Like first bold is #1, second is #2

#1. I'm not saying don't adjust the yoke. I've said over again now that to hold pitch you will be changing control forces. Something we've said again and again doesn't need to be said. So for the third time, hold pitch the same, that doesn't mean watch the airplane pitch up with the increase in power, it means... hold pitch constant. For the life of me I keep saying this and you keep reading, "This guy is freezing his control inputs."

#2. Yeah I guess as an airline pilot I personally think of a stall as a shaker and a deep stall as something past a pusher. I know those volcab words are wrong but its tough to shirk that mentality.

#3. You seem to get very involved in CG's relationship on this when I'm trying to simplify it a bit. Kinda like when you were a CFI (if you were) and held up the little model and said, "Here kid, there are 4 forces on a plane."

Thanks again for some help on the swing here.

 

[jtrain609]

That is what gets me about the whole thing. I have a hard time believing they over reacted to the stall AND lost directional control that fast. It just doesn't add up for me, guess I have too much faith in pilots.

Have you ever flight instructed before? I learned very quickly that any one of us, no matter how good or how experienced, can do things that will get us killed in short order. I've had everybody from student pilots with 2 hours to their name, to current airline pilots, to retired airline pilots attempt to kill me in airplanes.

It's just the nature of the beast ya know? As Mike says, "Anything and everything is possible at any given time, with or without prior notice."

 

[MikeD]

I don't think this is a proper interpretation of what's occurring. First of all, the use of the word "pitch" is not meaningful, and is the cause of a whole host of misunderstandings. "Pitch" does not control airspeed nor does it cause or break a stall. AoA does. Pitch is a combination of climb angle and AoA. If you're climbing out at a 10 degree flight path, and have an AoA of 5 degrees, then you have a pitch attitude of 15 degrees.

What I really think you're saying is that these aircraft had sufficient thrust to initiate a climb that would have allowed an AoA reduction.

You're right...I was using the pitch term kind of loosely to mean pushing the stick forward in order to reduce the AoA, in order to effect recovery quicker.

 

[tgrayson]

For the life of me I keep saying this and you keep reading, "This guy is freezing his control inputs."

Not a bit. I only objected to the phraseology you used about airspeed reducing the AOA. You may regard it as not saying something that doesn't need to be saying, but my observation is that you cannot make this relationship too explicit. Many will read your statement and get confused, which has already happened. Likewise, the statement that many Part 121 people make about "powering out of a stall" confuses people who think they understand what a stall is.

You seem to get very involved in CG's relationship on this when I'm trying to simplify it a bit.

Only to defuse a possible criticism. I don't want to say that the thrust lever will never increase airspeed; in some airplanes it will, hands off. Likewise, when I drop flaps in the Mooney I fly, the airspeed increases too. Why? Nose down pitching moment. In the end, it's still AoA that's working the magic.

 

[Soul Brotha']

Have you ever flight instructed before? I learned very quickly that any one of us, no matter how good or how experienced, can do things that will get us killed in short order. I've had everybody from student pilots with 2 hours to their name, to current airline pilots, to retired airline pilots attempt to kill me in airplanes.

It's just the nature of the beast ya know? As Mike says, "Anything and everything is possible at any given time, with or without prior notice."

:yeahthat:
We all like to think of ourselves as professional/experienced aviators but isht can happen quick that we are just not ready for no matter how much training we've gotten. Look at those poor FedEx guys, how much TT do you think between them?

 

[MikeD]

It's just the nature of the beast ya know? As Mike says, "Anything and everything is possible at any given time, with or without prior notice."

You still remember that?

 

[Realms09]

Not a bit. I only objected to the phraseology you used about airspeed reducing the AOA. You may regard it as not saying something that doesn't need to be saying, but my observation is that you cannot make this relationship too explicit. Many will read your statement and get confused, which has already happened. Likewise, the statement that many Part 121 people make about "powering out of a stall" confuses people who think they understand what a stall is.

It's discussions along these lines that make "Stick and Rudder," simple and old as it is, still an important book to get that message across.

 

[jtrain609]

You still remember that?

It's been quoted very often for years here now

 

[Trip7]

Two points

1. The shaker would not go off on a tail stall. Wings are still flying during a tail stall.

2. No matter what kind of power you have if you pitch up past the critical angle of attack the plane will stall. Impossible to power out of that. I believe I heard the plane pitched up to 31 degrees. Thats insane for even a jet.

 

[jtrain609]

Two points

1. The shaker would not go off on a tail stall. Wings are still flying during a tail stall.

2. No matter what kind of power you have if you pitch up past the critical angle of attack the plane will stall. Impossible to power out of that. I believe I heard the plane pitched up to 31 degrees. Thats insane for even a jet.

That's not true at all. You can ALWAYS override lack of lift with thrust. A great example of this is the F-15. That thing can accelerate while climbing straight up, as in at a 90 degree angle. If your thrust output is greater than your weight, then you could in theory never "stall" the aircraft, because you'd ALWAYS have enough thrust to power out of whatever maneuver you were in.

The wing might not be flying, but that doesn't matter if you have enough thrust at your disposal.