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New Airbus STALL RECOVERY procedure
No comments on the FOT Airbus issued this past week advising of a revised STALL RECOVERY procedure.?
FIREWALLing the throttles first has been the drill since primary training but now Airbus are saying to wait until the pitch has been lowered as it might even be necessary to reduce thrust to regain pitch authority. This seems to be quite a change to just throw out there with no forewarning or am I reading too much into it. For the A320 fleet: As soon as any stall indication (could be aural warning, buffet...) is recognized, apply the immediate actions : - NOSE DOWN PITCH CONTROL . . . . . . . . . . . . . . . . . . . . APPLY This will reduce angle of attack Note: In case of lack of pitch down authority, reducing thrust may be necessary - BANK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . WINGS LEVEL • When out of stall (no longer stall indications) : - THRUST . . . . . . . . . . . INCREASE SMOOTHLY AS NEEDED Note: In case of one engine inoperative, progressively compensate the thrust asymmetry with rudder - SPEEDBRAKES . . . . . . . . . . . . . . . . . . . CHECK RETRACTED - FLIGHT PATH . . . . . . . . . . . . . . . . . . . RECOVER SMOOTHLY • If in clean configuration and below 20 000 feet : - FLAP 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SELECT Note: If a risk of ground contact exists, once clearly out of stall (no longer stall indications), establish smoothly a positive climb gradient. |
The advice is fairly standard certification stall stuff - concerned with maintaining/recovering control rather than minimising height loss. Other than in situations near to terrain it makes real good sense. Many civil OEMs, and probably all military, will investigate other stall manoeuvres and recovery techniques to address other than simple certification situations.
Suggest you search some of John Farley's posts on stall recovery. Two concerns with an immediate slam throttle input - (a) the underslung engines will provide a significant nose up pitching moment as the RPM/thrust ramps up (b) due to the high alpha, the change in airflow direction at the engine intake will provide a significant vertical force at the engine intake lip as the RPM/thrust ramps up, adding to the nose up pitching moment. This effect is seen to be critical most commonly in piston to turboprop conversions where the heavier piston engine is replaced by a lighter turboprop located further out to the front of the aircraft .. providing an increased pitching moment due both to increased engine power (usually) and the increased pitching arm from the CG. A third possible concern involves gyroscopic precession as the nose pitches up which may provide some yaw .. which is not what we want at the stall ... Perhaps Sean R's voice finally has been heeded by the OEMs ? |
Not an AB pilot but wondering whether this is really a "revised" procedure or a "new" procedure inserted in recognition that even with its elaborate flight envelope protection an Airbus can stall.
The old "full throttles, etc..." thing applies to an "approach to stall/stick shaker" situation where stall has not yet developped and should still be valid. |
in "normal law" you can not fly the Bus into a stall....:8
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This FOT was prompted by several events in airbus aircraft (not only FBW) where high angle of attack situations were not handled optimally. At least one hull loss may well be attributed to this condition.
The previous stall recovery checklists did not have enough emphasis on the immediate requirement for a reduction in angle of attack. The above comments regarding 'slam' TOGA thrust, particularly with respect to nose up pitch moments and the real possibility of a secondary 'g' induced alpha exceedance during the initial recovery process, also lend weight to the new procedure. In FBW aircraft, where stall recovery would normally only be seen in an alternate law state (with reduced feedback protections at the sidestick) , this is even more relevant. |
Hi ,
Where is this procedure writen? |
i like this comment
in "normal law" you can not fly the Bus into a stall....http://images.ibsrv.net/ibsrv/res/sr...ilies/nerd.gif
browsing thru FCTM regarding protections in normal law, we have high pitch protection, low energy protection, high AOA protection, Alpha Prot, makes me wonder if this FBW airbus do reach actual stall condition... but if u are in low speed, high pitch (approach phase) and flying into build ups, u can actually be in a stall situation if there's very strong updaft in a few seconds towards the front part of the aircraft. the current recovery actions are to reduce the pitch as to reduce the AOA, wings level, and simultaneously apply full power till u are out of stall and once the speed builds up, u can reduce the power, or re-engage the A/thrust if Alpha Prot became active previously, and return to your original path (miss approach if in approach phase). height loss will be minimal. but if u are up there at 40'000 feet, in clean config, and suddenly u hit a severe CAT, i think it is more practical to unstall the surfaces, ie. to reduce the pitch and AOA, and wings level, before u apply power to increase the speed. height loss is not a primary concern in this situation. furthermore, at high altitude, a sudden increase in power demand might choke the engines, resulting in engine stall, plus unneccessarily firewalling the engines that added to the maintainance cost. from my opinion, they should come out with stall recovery on approach/near terrain as well... separate the recovery procedures so that pilots will be clearer on the actions to be done in different situation. my 2 cents....i might be wrong, and open for better explanation...;) |
nnco
FIREWALLing the throttles first has been the drill since primary training I would see the advice you are concerned about as emphasising what experienced pilots should already appreciate when flying aircraft with a low thrust line and not as something new. |
not quite agree with u there john... training should be of level standard regardless of your level of experience. thats why we have SOP..;)
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syedo
I had always viewed SOPs as an aid to standardising pilot actions in respect of a particular type of aircraft across a range of pilots. They may also be used by an employer to allow multi-crew operations to be standardised from entering the cockpit to leaving it so that two pilots who may never have flown together before feel completely at home. The idea of writing an SOP (about any topic or phase of flight) that is optimum for a single piston trainer as well as for a large multi engined airliner strikes me as a little unusual. JF |
strobes on
" In FBW aircraft, where stall recovery would normally only be seen in an alternate law state (with reduced feedback protections at the sidestick) , this is even more relevant. " This may be a fine point, but you equate "FBW" aircraft with Airbus "programming". Sequencing Thrust/Pitch is not necessarily applicable across other types, but is type specific, no? |
in "normal law" you can not fly the Bus into a stall....http://images.ibsrv.net/ibsrv/res/sr...ilies/nerd.gif - Pitch becomes Alternate (Load Factor protection, no Autotrim) - Roll becomes Direct (mechanical yaw control) - No reversion to Direct after LDG Gear extension After recovery: - Pitch stays Alternate without protections but with Autrotim - Roll becomes Direct - Yaw becomes Alternate As you may suddenly get into Abnormal at any time, I've reason to believe the FOT is referred to this condition more than Alternate, Direct and MECH BCK, where the crew is well aware the plane can stall. |
bear
Yes - I was referring only to Airbus FBW aircraft. Should have made that clearer. |
A very good document from British CAA that has a lot in common with the new procedure:
Applicability: RETRE, TRIE, TRE, SFE, TRI, SFI Effective: Immediate STALL RECOVERY TECHNIQUE 1 Recent observations by CAA Training Inspectors have raised concerns that some instructors (both SFIs and TRIs) have been teaching inappropriate stall recovery techniques. 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”. 2 It could be argued that with all stall warning devices working correctly on an uncontaminated wing, such a recovery technique may well allow the aircraft to accelerate out of danger with no height loss at the lower to medium altitudes. The concern is that should a crew be faced with anything other than this idealised set of circumstances, they may apply this technique indiscriminately with potentially disastrous consequences. 3 The standard stall recovery technique should therefore always emphasise the requirement to reduce the angle of attack so as to ensure the prompt return of the wing to full controllability. The reduction in angle of attack (and consequential height loss) will be minimal when the approach to the stall is recognised early, and the correct recovery action is initiated without delay. NOTE: Any manufacturer’s recommended stall recovery techniques must always be followed, and will take precedence over the technique described above should there be any conflicting advice. 4 Any queries as a result of this FCTN should be addressed to Head of Flight Crew Standards at the following e-mail address: [email protected]. Captain David McCorquodale Head of Flight Crew Standards 21 April 2010 |
indeed one trainee was briefed that “he may need to increase back pressure in order to maintain altitude |
From day one of flying a plane were we not taught to lower the nose first to break the stall by restoring the airflow over the top of the wing?
The A320 is an aircraft after all, I know sometimes it is easy to forget! |
The first order of business is to reduce the angle of attack. Nothing new there. No surprise. 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.
Accounting for variables, you don't necessarily need to 'slam' any FADEC controlled engine through the instrument panel. FADEC will merely set power based on the detent at whatever rate IT determines. Engine mounting and resulting thrust vector also plays a role and both Airbus and Boeing recognize this. With an ever increasing number of stall accidents and loss of control it has become apparent the industry needs a serious review of some basic aerodynamic facts and they have both amended their stall recovery procedure to emphasize this. You are well advised to continue the discussion and pay attention to your amendments and Authority safety notices about stall, approach to stall and recovery/recognition. The 'notion' of many flight crew to misinterpret 'minimal loss of altitude' in stall recovery during a flight test has erroneously been interpreted by some to mean "within 100 feet". This notion needs to be erased. |
At high altitude that reduction of attack angle may be as much as negative 10 or 20 degrees |
interesting
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.
My personal view is to easy the nose down to assist the MAX power to encourage air flow over the surfaces. We do have the advantage of engines mounted above the wing, so the "push" is more down than up. I have experienced a high altitude stall, due to getting very close, if not too close to the top of a CB, pitch down of 10 degress, was the only way to recover, as the power was already maxed out. As to "my passengers would not like negative Alpa": Better then DEAD. |
Originally Posted by willie
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.
Anyone who has spent any time doing max performance manoeuvres will tell you that too much buffet in a max rate turn goes away IMMEDIATELY you relax the pitch a fraction. A little finesse is required and a wing that is unstalled is....well, a wing that is unstalled.. Certainly anyone getting 'used' to your 'high-level' technique will probably cause certain death in a low level eg approach stall. |
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”. |
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." |
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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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 ? |
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. |
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. |
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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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. |
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. |
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. |
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. |
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 |
Originally Posted by p51guy
(Post 5710973)
Oh, that's right, an airbus cannot stall in normal law but can it hit the ground?
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. |
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! |
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!! |
- 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. 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. 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. 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". |
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. |
Originally Posted by Checkboard
maintained the normal after take-off climb pitch (about 15º nose up)
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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 |
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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