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Old 21st May 2010, 13:21   #21 (permalink)
 
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It would appear that these instructors have been encouraging their trainees to maintain altitude during recovery from an approach to a stall. The technique that has been advised is to apply maximum power and allow the aircraft to accelerate out of this high alpha stall-warning regime. There is no mention of any requirement to reduce the angle of attack – indeed one trainee was briefed that “he may need to increase back pressure in order to maintain altitude”.
The "canned" stall recoveries in my Alteon course were basically run along the same lines - minimise height loss. That, of course, is not what you do, as you guys have pointed out, if you're already at full power, stalled and going nowhere.
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Old 23rd May 2010, 12:57   #22 (permalink)
 
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Obviously if close to the ground, reducing height loss would be of up most importance during the recovery. A stall at altitude would allow a generous degree of nose down pitch and height loss during the recovery, something not acceptable on final approach.

A stall close to the ground would require a great deal of finesse to recover from. Max power and very carefully balancing a safe reduction in pitch against height loss while the wing unstalls and the aircraft powers out of it would seem to be in order.

Pancaking onto the ground in a flat, low speed condition would probably offer a greater chance of survival than stalling and crashing nose down or dropping a wing and spinning in.

Remember D.P Davies stating that "If ever the day should come when you are faced with the choice of stalling, or doing something else, choose the alternative."
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Old 23rd May 2010, 23:10   #23 (permalink)
 
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Wind shear training which happens close to the ground emphasizes not lowering the nose after full power application below stickshaker until recovery is complete. A stall could be caused by windshear close to the ground so tell me how Airbus now handles this. Lower the nose and smoothly add power???? Oh, that's right, an airbus cannot stall in normal law but can it hit the ground?
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Old 23rd May 2010, 23:17   #24 (permalink)
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Wind shear training which happens close to the ground emphasizes not lowering the nose after full power application below stickshaker until recovery is complete.

The philosophy is that, given you have a high chance of dying if you don't do something drastic ... one is best advised to go with the procedure most likely to maximise survival chances in the short term ... if something else happens simultaneously .. perhaps it just wasn't your day ?
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Old 23rd May 2010, 23:43   #25 (permalink)
 
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Given that the best L/D likely occurs at or below shaker activation, if you are both in windshear and stalled, you need to lower the nose, both to (a) unstall the wind and regain control of your flightpath and (b) get to the airspeed/attitude/AOA where you have the best chance of your aircraft's performance being adequate to get out of the shear.

Sitting there with a stalled wing isn't going to do squat for your chances of climbing away from the ground. This is the fundamental flaw with the way the ridiculous "minimize altitude loss" is being indoctrinated into people via the PTS; once the wing is stalled, you are going DOWN. If you wish to stop going down, you have to unstall. Therefore lowering the nose to unstall the wing will minimize the altitude loss.

Unfortunately, the manoeuvre is invariably taught with a fully attached, pre-stall, wing, which gives the wrong lesson for the stalled case.
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Old 24th May 2010, 00:10   #26 (permalink)
 
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At high altitude that reduction of attack angle may be as much as negative 10 or 20 degrees and will result in a number of thousand feet loss of altitude.
That must be pitch and even then that is a lot--5-10 degrees nose down would be like it. Due to being power-limited, the only means to increase EAS and Mach is gravity.
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Old 24th May 2010, 00:48   #27 (permalink)
 
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Sometimes in turbulence it may not be easy to determine if wind shear or just a basic stall do to inattention caused the stick shaker to activate breaking out at 500 ft. I totally agree with altitude to spare lowering the nose as you increase power is the best procedure. I know Airbus has had problems with max power with a pitchup. Never found it a big problem with Boeings using normal control inputs.
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Old 24th May 2010, 02:29   #28 (permalink)
 
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Best L/D is well above stall speed. 1.3 minimum of stall speed rings a bell. Max lift occures right before stall but the drag is at max. That is why low altitude stall recoveries sometimes have to sacrifice speed for more lift to not impact the ground. Best L/D is close to best glide speed. It is best to not venture below this speed but some situations require it. The shaker is a warning you are approaching stall angle of attack but if you don't force it to go deeper into the stall you have almost max lift but also almost max drag. Breaking out at 500 ft getting a stick shaker and lowering the nose first would only compound your situation. High sink rate and low speed is not good. Add power to recover and minimize sink rate.

It has worked well for 107 years.
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Old 28th May 2011, 20:07   #29 (permalink)


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Stall Recovery Training

We must remember that in any aircraft, and Airbus is no exception, the greatest tool for safety is situational awareness. Let's hope that no computer program will ever replace the aviator in the flight deck.

In the case of a stall, an aviator must remember not just what was taught in the simulator but rather must imagine the conditions that were meant to be simulated.

I know we fly how we train, but the more experience teaches us, the more we should use it. A stall recovery procedure in the simulator is designed to test the pilot's mastery of the aircraft, in the hopes that that knowledge will be used later to fly the aircraft safely in all kinds of unforecast conditions.

I remember, as I was teaching in the simulator in a previous position, the students were quite critical of the complexity of a specific procedure.

My point to them was that the procedure was not designed to fail them, but rather provide good pointers as to how the aircraft may behave in rapidly changing conditions and airspeeds. Invariably, once the students progressed through the training, they came to appreciate the value of that maneuver.

In the case of an actual stall (such as Air France 447 may have entered- since we don't know everything just yet), conditions change so quickly that pilots have to step out of their "as trained" comfort zone, and process these changes and react, perhaps differently, but with knowledge and mastery.

I hate to reach out to old addages, but good old stick and rudder skills are invaluable in such situations, since Airbus or not, modern aircraft still employ those devices.

Pilots should keep in mind all this, as they graduate a training program. Once entrusted with the lives of people, I must repeat a statement I made to one of my students in the past: One must put the thinking hat on and keep it on until safely at the gate.
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Old 28th May 2011, 20:51   #30 (permalink)
 
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MAD SCIENTIST

in the case of the windshear and depending on circumstances it can be better to be at the verge of stall than to pitch down. A quasistalled airplane goes down, but a quasistalled airplane pitching down goes down faster, and you need height to recover the speed you need to make a pull out. You might get in a secondary stall or simply crash before you have enough energy. In these cases, it can be better not to sell any potential energy and hope that the windshear will end soon.

Windshear is a problem of time, after all.
____________

As far as I know, Airbus drivers do not practice stalls in the sim.

Because airbus FBWs are supposed not to stall.

but they do

Until one year or so, stall recovery technique was only included deep in some FCOM (you never know which one, exactly). They decided to include it in the QRH as a proper procedure and now we have one more memory procedure... (20 years late!).

Before coming to the airbus, I saw too many FIs giving too much importance to the height loss during a stall recovery. I always thought that the wings are what matters, and the sooner you unstall them, the better, because the less energy will be lost.
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Old 28th May 2011, 20:57   #31 (permalink)

 
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Not to sound sciolistical or anything, but considering how much of commercial aviation is based on proceedure

I think the procedure should emphasize the fact that below a certain altitude, the traditional stall recovery procedure of firewalling the throttles should be used.
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Old 28th May 2011, 22:20   #32 (permalink)
 
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Don't have it handy...

Don't have it handy, as I'm on vacation....no FCOMs with me....
BUT: The Bus can be stalled in normal law....yes, it's true, I
promise....if you're on one engine and you have slats/flaps out.
The info is hidden in the bowels of the FCOM.

Second, I'm the type of instructor who has the philosophy that
if a student hasn't learned, the teacher hasn't taught....I always
feel like our training program has failed anytime we have a student
fail or have a problem on the line. In my opinion, the line pilot should
be the last to be blamed. (My position on this, sometimes, really
pisses off my boss.)

Having said that, we, as educators, have failed. For all these years
we've been teaching 'approach to stalls' as if they were actual stalls.
Airbus, now along with the FAA and many U.S. carriers, are making
the distinction. Two different situations; two different procedures
for recovery.

Two weeks ago, Airbus had a meeting in Dubai, and this topic was
discussed. (along with the "new" stall recovery procedure....ha ha ha)

So, what we've been drilling all these years is recovery from the
approach to stall. Now, we're making the distinction...and the 'new'
delineated procedure is for the actual stall.

And, even more to muddy the waters, Airbus states that the
distinction between the two maladies can sometimes be difficult
to determine, even for test pilots. (Assuming that test pilots
are the best pilots in the universe....)

Ya'll be careful out there, ya hear!!!!1
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Old 28th May 2011, 23:48   #33 (permalink)
 
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Quote:
Originally Posted by p51guy View Post
Oh, that's right, an airbus cannot stall in normal law but can it hit the ground?
Yes, this has been common knowledge for longer than the A320 has been in line service - because this feature of the protections was sadly demonstrated at the Habsheim-Mulhouse airshow, when the PF, having permanently disabled autothrust, tried to pull back on the stick before the engines had spooled up. From his point of view, the aircraft was not responding to his inputs and this was the germ of the "Airbus FBW overrides pilot inputs" complaints that are constantly repeated by his supporters. What tends to be excluded in those complaints - and is something that the PF never draws attention to - is the fact that having irreversibly disconnected throttle control from the computers, his inputs would have caused an unprotected aircraft to stall and fall to the ground in an uncontrolled fashion, with the likelihood that the death toll would have been significantly higher.

Returning to the topic at hand, I think Airbus are doing the right thing by emphatically stating that if you have stalled the aircraft and have altitude to spare the correct action is to get the nose down as soon as possible. This becomes extra important if you have bad airspeed data, because in that situation the stall protections cannot work.
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Old 29th May 2011, 01:45   #34 (permalink)
 
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PantLoad,

when you have the time could you please refer to FCOM when it says that an Airbus FBW can be stalled in normal law?

I also share the opinion that Pilots are very bad trained in relation to real stall recoveries. I have never failed to recover an aircraft from a stall situation but have I tried to recover it when I am in severe turbulence with different indications regarding to speed and altitude? Of course not!

"if a student hasn't learned, the teacher hasn't taught" - not always true but very very true!
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Old 29th May 2011, 06:34   #35 (permalink)
 
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Bloggs,
I think you ( and many others) would be rather appalled at what is required by YSBK CASA office FOI's, in recent times, highly experienced pilots have been failed on base checks for ANY decrease in attitude during stall and recovery. "Powering" out of the stall with zero loss of height has been "informally" adopted as the "standard".

Indeed, one FOI was "demanding" that the stall/attitude warning/stick pusher system in a Metro be deactivated and the aircraft pulled into a "proper" stall ---- only a very very strongly worded letter from the Type Certificate holder dissuaded them/him from the practice.

Maybe some of these "CASA experts" would benefit from a course with UK CAA at Redhill.

Tootle pip!!
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Old 29th May 2011, 11:37   #36 (permalink)
 
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Quote:
- no way Jose! Unless you have been indulging in some aeros or a major upset, a reduction of a few degrees is sufficient to silence the stick shaker or at worst to unstall the wing - to pitch 10-20 down from a normal high level stall AoA of around 5-7 degrees would be horrendous and would upset me as well as Tyro, spilling our 'retired' G&Ts in First and would undoubtably "result in a number of thousand feet loss of altitude" if not bits falling off the a/c.
Quote:
That must be pitch and even then that is a lot--5-10 degrees nose down would be like it. Due to being power-limited, the only means to increase EAS and Mach is gravity.
The information from the AF447 FDR now shows that the aircraft was descending for three minutes with and Angle of Attack of 40º or so - so it should be obvious to see now that, in this type of upset at high altitude resulting in a deep stall, even 10-20º reduction in pitch (OR AoA) may not be enough.

Quote:
On the GLF we teach to keep pitch attitude, and just add FULL MAX WAR POWER, and the aircraft will power itself out of the stall.
...which is exactly what the AF crew did - maintained the normal after take-off climb pitch (about 15º nose up) with full power for three minutes - and remained stalled until the event ended.

Quote:
I think you ( and many others) would be rather appalled at what is required by YSBK CASA office FOI's, in recent times, highly experienced pilots have been failed on base checks for ANY decrease in attitude during stall and recovery. "Powering" out of the stall with zero loss of height has been "informally" adopted as the "standard".
Then they are teaching people to die. Stall recovery is exactly that - un-stall the wing, and everything else is secondary (including terrain clearance). Minimising height loss with a stall recovery at altitude is simply not a consideration - if the pilot is so out of the loop that the aircraft has stalled in the first place, then the recovery is going to take some height.
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Old 29th May 2011, 11:52   #37 (permalink)
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Powering out of stall MIGHT be adequate on large propeller aircraft - eg Electra and, I would imagine, the Herc would be similar. Certainly, it was fun to do just that on the Electra - a few shudders and away it would go. However, the size of the prop disks meant a sudden and dramatic change in airflow over the wings. It's a bit different with a jet.

The general certification stall recovery is a bit different to the training version - another example of operations not reading the certification stuff. Some aircraft, if held into the stall will do strange things not addressed during certification. The trick is to get the wing unstalled first (and promptly) ... then worry about thrust.

Indeed with a high alpha a heavy handed bunch of thrust might well produce an unwanted and significant nose up pitching moment rather than the nose down pitching moment desired.



Of course, if this is all happening at near dot feet, then one might be advised to incline to minimising height loss on the basis that you are going to die if the stall persists - a case of playing the risk numbers. That is a specific case with priorities different to the general.
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Old 29th May 2011, 15:45   #38 (permalink)
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Quote:
Originally Posted by Checkboard
maintained the normal after take-off climb pitch (about 15º nose up)
- in which part of the report do you see that? I see 'increasing above 10 degrees'
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Old 29th May 2011, 22:30   #39 (permalink)
 
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AF447

BOAC,

I think you are referring to the initial increase in pitch, at the start of the upset sequence?

Quote from the English version of the BEA "Update":

"The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb. The PF made nose-down inputs and alternately left and right roll inputs."

The initial increase in pitch is not explained. At that stage, the BEA does not report any sidestick input.

The aircraft climbed from FL350 to FL375. At that stage, the BEA continues:
"At 2 h 10 min 51, the stall warning was triggered again. The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs. The recorded angle of attack, of around 6 degrees at the triggering of the stall warning, continued to increase. [...]
Around fifteen seconds later, [...]. The PF continued to make nose-up inputs. The airplane’s altitude reached its maximum of about 38,000 ft, its pitch attitude and angle of attack being 16 degrees."

Without wishing to put words into anyone else's mouth, I think the last two sentences may be what Checkboard was referring to.

Chris


Last edited by Chris Scott; 29th May 2011 at 22:43.
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Old 30th May 2011, 08:27   #40 (permalink)
 
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Putting aside all talk of whether the Airbus can stall or not, is this change to the stall recovery procedure not, in fact, applicable to all jet types? I had understood it as a joint change by both Boeing and Airbus, possibly others as well.

In my airline all types have adopted the new recovery technique, not just airbus fleets.
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