High speed buffeting

[Evan]

We call this one Gone With the Wind:

http://forums.jetphotos.net/showthre...ighlight=stall

[3WE]

Originally Posted by Gandalf123

Come on guys..... You should have learned this in flight school.

You are in a stall most likely because you have an excessive AOA and/or, not enough power. You MUST reduce AOA and increase power. YOU NEED MORE AIRSPEED NOW OR DIE!!!!! Once you have recovered from the stall, you aren’t going to sit there like a dildo, leave the engine at full power and fly the plane into oblivion. You will reduce to climb power or cruise power or whatever, and return to normal flight.

Let us know when you are ready to join the adult world.

This thread is about high-speed buffet- and references operations near coffin corner.

Coffin corner is tricky because if you go ever so slighlty faster, the plane can go into a "not-so-controllable" dive, and in some instances you can break up and die.

or, if you go ever so slightly slower, you can stall, and high-performance jet planes can do strange things in a stall, sometimes going out of control where you break up and die or have a flame out, which can also cause you to break up and die when you can't glide to a runway.

To simply cram full power on and shove the nose over, you might just overspeed and get into one of those bad dives.

Instead of your ALL CAPS SUGGESTIONS of FULL POWER and NOSE OVER NOW!, what if you slightly nose over?

Next time you go flying, please ask your instructor about an imminent stall, and critical control without the need to grossly over correct.

By the way- also review what happens to engines when really really high up in the sky....what makes you think there's extra power available?

And review what "more" airspeed has to do with a stall. If you dive on your girlfriends house, I imagine you will have plenty of airspeed, and I guess no risk of stalling when you pull up...right?

As much as some of us have ranted and raved about pilots relentlessly pulling up in spite of nose high attitudes, low speed, and stall warnings, it is correct that an aggresive dive should not be the first response to a near-stall or a stall situation- you can burn lots of altitude, and possibly even hit the ground.

Again, what would be wrong with a careful, small reduction in nose up attitude (don't touch the throttle), followed by extreme attention to what the airplane feels like, whether your airspeed is healthy, whether your attitude is healthy whether the plane seems to be flying healthy, whether the controls feel healthy, and whether your altitude is trending ok???

Ask your instructor about stalls where your objective is to minimize altitude loss. It's the same basic thing and it's a basic airmanship skill.

[3WE]

Originally Posted by Gandalf123

Well Gabriel, that disagrees with over 100 hours of my flying experience in the Cessna 172.

Interesting, my 100 hours of flying a 172 agrees with Gabriel even though he flies that goofy Tommahawk.

[Evan]

Originally Posted by Gandalf123

Near stall buffering... That is when that dreadful sounding stall warning conmes on... Nose down and full power and make it snappy or the plane will fall out of the sky like a grand piano test flown off the the Empire state building

Fortunately, the stall warning comes on before buffeting, when you are still in a controlled envelope. It's telling you to immediately reduce AoA, NOT NOSE OVER. If you slam on the power in an underslung jet, you will increase the pitch due to thrust effect and possibly stall, so the thing to do is first REDUCE AoA until the stall warning ceases by CAREFULLY decreasing pitch and then CAREFULLY increase to full power. If you are in close ground proximity, you will then have to slightly increase pitch up to stall warning to minimize altitude loss and lower again to silence it and repeat this until you get stabilized. Or if you can't, crash into the trees unstalled, which is better then crashing in a stall-induced roll.

How'd I do Gabriel?

[Evan]

Originally Posted by 3WE

Interesting, my 100 hours of flying a 172 agrees with Gabriel even though he flies that goofy Tommahawk.

And how many times have you experienced mach buffet in the 172?

[3WE]

Originally Posted by Evan

And how many times have you experienced mach buffet in the 172?

As many times as Gandalf or Gabriel.

Oh, and stall recovery- it's full power and 12 degrees nose up (no deviations)- remember jets are really powerful and can genuinely power out of an incipient stall situation with no altitude loss at all.

[Gabriel]

Originally Posted by Evan

How'd I do Gabriel?

Definitivelly imporving

[snydersnapshots]

Originally Posted by Evan

Fortunately, the stall warning comes on before buffeting, when you are still in a controlled envelope. It's telling you to immediately reduce AoA, NOT NOSE OVER. If you slam on the power in an underslung jet, you will increase the pitch due to thrust effect and possibly stall, so the thing to do is first REDUCE AoA until the stall warning ceases by CAREFULLY decreasing pitch and then CAREFULLY increase to full power. If you are in close ground proximity, you will then have to slightly increase pitch up to stall warning to minimize altitude loss and lower again to silence it and repeat this until you get stabilized. Or if you can't, crash into the trees unstalled, which is better then crashing in a stall-induced roll.

How'd I do Gabriel?

You're right about reducing AOA but not nosing over, however I'm going to beg to differ with you regarding power application on a jet with underslung engines. Here's an excerpt from the stall recovery procedure for a large jet (bigger than a 737, smaller than a 777, and not a 787):

"...Accelerate to the normal maneuvering speed with minimum altitude loss... by pushing the thrust levers to their forward limit and calling "max thrust, stow speedbrakes," leveling the wings if in a turn. Smoothly adjust the pitch attitude to maintain altitude or minimize altitude loss. Any pitch change should be smooth and gradual. In most configurations and weights the airplane will accelerate away from a stall without changing pitch attitude"

Needless to say, the last sentence is predicated on a low-altitude stall. At high altitudes, you're not going to recover without losing some altitude. You are correct regarding the pitch change with power application in an airplane with underslung engines, however after enough time in the airplane, the compensation becomes automatic and the pilot doesn't even notice the pitching moment anymore.

[snydersnapshots]

Originally Posted by 3WE

Interesting, my 100 hours of flying a 172 agrees with Gabriel even though he flies that goofy Tommahawk.

HEY! Don't be putting that airplane down. I have many fond memories (and one scare-the-crap-outta-me moment: I made the mistake of looking at the tail in a stall) in the venerable PA38-112 "Tomachicken"

[snydersnapshots]

If you will indulge me just one more time while I hijack the thread, since it's turned into a stall discussion as well, I'd like to relate an experience I had recently. While I know not everyone on this forum is a pilot, there are enough on here that I feel this might be beneficial (Moderator: if you want to move this to a new or different thread, feel free). I've often wondered how a pilot could get into an inadvertant stall, especially in a modern jet. The other day I learned, though it didn't get dangerous, it was enough to wake me up.

Descending to 13,000 feet, the autopilot was on and the FMC was programmed to cross an intersection at 13,000 feet and 250 knots. As the airplane leveled the other pilot and I had our attention diverted outside looking for traffic. When I looked back inside the speed was down at 230 and decreasing and the speed bug (which should have been at 250) was at the top of the low-speed buffet, 210 knots. I said those two famous CVR words ("OH S&*T!"), added power, and manually set the bug to 250. Then I checked the FMC to see what the commanded speed was. It was our target approach speed of 143 knots. The next question was the famous "why'd it do that?" I still have no idea--I do know I verified the 250/13000 in the box when we started the descent. It shouldn't have done that and in 17 years of flying FMC's and 7 years on this airplane, I've never seen one do that... I was glad to see that it defaulted to the top of the buffet margin though instead of trying to take us all the way down to approach speed with the flaps up...

It was a major eye-opener for me. From now on, no matter what's happening outside, I'll glance in when the autopilot levels the airplane!

[Evan]

Originally Posted by snydersnapshots

Descending to 13,000 feet, the autopilot was on and the FMC was programmed to cross an intersection at 13,000 feet and 250 knots. As the airplane leveled the other pilot and I had our attention diverted outside looking for traffic. When I looked back inside the speed was down at 230 and decreasing and the speed bug (which should have been at 250) was at the top of the low-speed buffet, 210 knots. I said those two famous CVR words ("OH S&*T!"), added power, and manually set the bug to 250. Then I checked the FMC to see what the commanded speed was. It was our target approach speed of 143 knots. The next question was the famous "why'd it do that?" I still have no idea--I do know I verified the 250/13000 in the box when we started the descent. It shouldn't have done that and in 17 years of flying FMC's and 7 years on this airplane, I've never seen one do that... I was glad to see that it defaulted to the top of the buffet margin though instead of trying to take us all the way down to approach speed with the flaps up...

The Airblue A321 crash last year was partially caused by the FMC not engaging the selected guidance. The reason for this was that the pilot did not pull the knob after selecting the heading to engage the selected mode. The FMC then reverted back to its managed mode parameters. This was a pilot with little experience on Airbus types. Still I wonder if this push/pull methodology isn't a bit of a pitfall for distracted pilots.

[Gabriel]

Originally Posted by snydersnapshots

Here's an excerpt from the stall recovery procedure for a large jet (bigger than a 737, smaller than a 777, and not a 787):

"...Accelerate to the normal maneuvering speed with minimum altitude loss... by pushing the thrust levers to their forward limit and calling "max thrust, stow speedbrakes," leveling the wings if in a turn. Smoothly adjust the pitch attitude to maintain altitude or minimize altitude loss. Any pitch change should be smooth and gradual. In most configurations and weights the airplane will accelerate away from a stall without changing pitch attitude"

What a crappy and aged procedure!!! (which, by the way, looks like the old "approach to stall recovery" and not the old "full stall recovery" procedure).

Are you sure it is dated, that your airline didn't release a new one recently or isn't in the process of doing so? Didn't you recently received a publication regarding the changes that the airline industry at grate (Boeing, Airbus, FAA, JAA...) has done regarding policies and guidelines for stall recovery?

Well, after several fully avoidable crashes where the pilots prioritized minimizing altitude loss over not stalling or recovering from a stall, the philosophy towards stall recovery was changed extensively, in fact returning it to what it should have never been taken away of: the basic stall recovery that you learn when you have about two hours of student-pilot under your belt.

To summarize, the changes are:
- Priority is taken from minimizing altitude loss to silencing the stall warning first.
- In line with the above, priority is taken from the throttles to the yoke.
Both the approach to stall and the stall are problems of the same nature (just different intensity): Too much AoA. The solution to both is the same: Reduce AoA. Even further, while the onset of the "approach to stall" is pretty clear (stall warning or buffeting), the onset of the real stall isn't. So now there is one unified procedure for both situations: Use elevator to reduce AoA at least as needed to silence the stall warning. The use of throttle is left to a second priority and even then, in airplanes with underslung engines, with caution and smoothly.
- Minimizing altitude loss has been changed for silence the stall warning ASAP in the FAA checkrides.
- It is understood that minimizing altitude loss cannot be successfully achieved unless you successfully control the AoA FIRST.

Being this change endorsed by the airplanes' manufacturers and the regulators, it would very strange that you haven't heard of it yet. More info in the Stall thread (linked by Evan a few slots above).

You are correct regarding the pitch change with power application in an airplane with underslung engines, however after enough time in the airplane, the compensation becomes automatic and the pilot doesn't even notice the pitching moment anymore.

Tell that to a couple of 737 pilots that couldn't arrest the nose-up pitching and subsequent increase in AoA and further loss of speed even after applying forward yoke to the stops. The engines were inadvertently idled in an ILS approach witht the AP adding nose-up trim to track the glide slope until the stick shaker activated, point at which the pilots TOGAe'd it and disconnected the AP. The plane kept pitching up despite the full forward yoke, fully stalled and fell. During the fall the nose went down and the plane gained enough airspeed to increase the effectiveness of the elevators to the point where the pitch could be controlled. It was a really close call. They could have added nose-up pitch (the plane was badly misstrimmed after the AP did what it did), but that didn't occur to them in the heat of the moment.

[Evan]

Originally Posted by snydersnapshots

You're right about reducing AOA but not nosing over, however I'm going to beg to differ with you regarding power application on a jet with underslung engines. Here's an excerpt from the stall recovery procedure for a large jet (bigger than a 737, smaller than a 777, and not a 787):

"...Accelerate to the normal maneuvering speed with minimum altitude loss... by pushing the thrust levers to their forward limit and calling "max thrust, stow speedbrakes," leveling the wings if in a turn. Smoothly adjust the pitch attitude to maintain altitude or minimize altitude loss. Any pitch change should be smooth and gradual. In most configurations and weights the airplane will accelerate away from a stall without changing pitch attitude"

snydersnapshots, no disrespect but we had a bit of a lengthy discussion about this recently. In the wake of a number of stall-related accidents, where pilots actions tended to exacerbate the stall rather than attenuate it, manufacturer's stall procedures were rewritten from the one you posted above. The new procedures call for priority to be placed on silencing the stall warning, not on minimizing altitude loss (obviously when not in ground proximity), and specified priority on pitch management to silence the stall warning, then smoothly adding power, and emphasized the importance of compensating for a pitching moment if power was brought on abruptly.

What concerned me then and still concerns me is whether this information is reaching pilots through periodic upset recovery training and updates to the QRH/FCOM in the cockpit. Your post is confusing and causes me to wonder about this. Is it possible that you have outdated procedures...?

I think these procedures were rewritten due to a number of pilots who seemed to lack basic airmanship instincts in a stressful upset situation, and were intended to address the occasional low-hanging fruit that might make it into a automated cockpit. Pilots with solid airmanship probably aren't going to get into the stall regime in the first place.

Example, you got tripped up by the automation, but you caught the error in time because you were actively monitoring and flying the plane. That is the kind of airmanship that is lacking in these incidents.

(EDIT: sorry Gabriel, I wrote this before I saw your post.)

[snydersnapshots]

Originally Posted by Evan

snydersnapshots, no disrespect but we had a bit of a lengthy discussion about this recently. In the wake of a number of stall-related accidents, where pilots actions tended to exacerbate the stall rather than attenuate it, manufacturer's stall procedures were rewritten from the one you posted above. The new procedures call for priority to be placed on silencing the stall warning, not on minimizing altitude loss (obviously when not in ground proximity), and specified priority on pitch management to silence the stall warning, then smoothly adding power, and emphasized the importance of compensating for a pitching moment if power was brought on abruptly.

What concerned me then and still concerns me is whether this information is reaching pilots through periodic upset recovery training and updates to the QRH/FCOM in the cockpit. Your post is confusing and causes me to wonder about this. Is it possible that you have outdated procedures...?

I think these procedures were rewritten due to a number of pilots who seemed to lack basic airmanship instincts in a stressful upset situation, and were intended to address the occasional low-hanging fruit that might make it into a automated cockpit. Pilots with solid airmanship probably aren't going to get into the stall regime in the first place.

Example, you got tripped up by the automation, but you caught the error in time because you were actively monitoring and flying the plane. That is the kind of airmanship that is lacking in these incidents.

(EDIT: sorry Gabriel, I wrote this before I saw your post.)

Gabriel and Evan--no disrespect assumed and no offense taken. On my last sim ride they did brief and we did demonstrate the "new" procedures for stall recovery during the upset portion of the training and the instructor emphasized that recovery from the stall or impending stall is more important than maintaining altitude. They're in the process of rewriting several manuals and procedures so that one is probably in the pipeline somewhere and just hasn't hit the book yet.

Originally Posted by Evan

Your post is confusing and causes me to wonder about this. Is it possible that you have outdated procedures...?

My apologies for the lack of clarity. That is probably due to the fact that I edited the procedure so I didn't take up an entire page here. I also changed some of the language while keeping (trying to keep?) the basic idea of the procedure. I don't want to put direct quotes from the manual in case someone from my company happens to come across one of my posts... I don't know that I would get in trouble, but I don't want to push the envelope either.

[Gabriel]

Originally Posted by snydersnapshots

Gabriel and Evan--no disrespect assumed and no offense taken.

Of course not, please!
The questions, if any, were aimed at your airline (whichever it is), not at you.

[snydersnapshots]

Originally Posted by Gabriel

Of course not, please!
The questions, if any, were aimed at your airline (whichever it is), not at you.

Oh definitely! I'm really enjoying the give-and-take here and you're keeping me honest--I'd expect nothing less. LOL...Just don't throw TOO much math at me...

[3WE]

Originally Posted by Me

Tommahawks are wierd, 172's are not

Originally Posted by snydersnapshots

HEY! Don't be putting that airplane down. I have many fond memories (and one scare-the-crap-outta-me moment: I made the mistake of looking at the tail in a stall) in the venerable PA38-112 "Tomachicken"

Well, high wing and low tail versus low wing and high tail...one of 'em has to be wierd!

...nevertheless, somehow, they both fly.

[3WE]

Originally Posted by Gabriel

...3WE likes to say, flying too slow, aiming the nose too high or pulling too many Gs are good ways to stall a plane...

Indeed

Especially when you are trying to maintain altitude with inadequate power.

[3WE]

Originally Posted by Gabriel

What a crappy and aged procedure!!!

C'mon Gabriel...

Jet's are really powerful.

They really can power away from stalls with no need to lower the nose. (Much better than you and synder's wierd 115 hp Tommahawk, or even my super duper 180 horse 172)

It really is the best technique to minimize altitude loss.

As is the procedure to NEVER EVER let airspeed or attitude get to that point in the first place- (Which Synder did beautifully, by the way)

The procedure that needs to change is this:

The stall warning is going off.
The plane is descending (rapidly)
The controllability sucks
The airspeed is low
The nose attitude is up
The AOA (if you have it) is greater than 15 degrees

QUIT RELENTLESSLY PULLING BACK ON THE STICK!

Power up and carefully adjust the nose attitude to make the stall warning happier.

or

Call center and say, "hey dude we can't maintain four one oh" and turn off the autopilot and start a descent with careful attention to stall warnings, airspeed, attitude and other behavior.

[Gabriel]

Originally Posted by 3WE

The procedure that needs to change is this:

The stall warning is going off.
The plane is descending (rapidly)
The controllability sucks
The airspeed is low
The nose attitude is up
The AOA (if you have it) is greater than 15 degrees

QUIT RELENTLESSLY PULLING BACK ON THE STICK!

Power up and carefully adjust the nose attitude to make the stall warning happier.

or

Call center and say, "hey dude we can't maintain four one oh" and turn off the autopilot and start a descent with careful attention to stall warnings, airspeed, attitude and other behavior.

That seems to be too "advanced" for some...