Air Asia Indonesia Lost Contact from Surabaya to Singapore
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[from actual incident report]
From other Airbus experiences (and I am open to correction) the turbulence and fluctuating outside air temperature fluctuation lead to autopilot disconnect if the angle of attack then reaches the 'alpha prot' value. The angle of attack excursion beyond alpha prot causes a change in the pitch flight control law from normal law (NZ law) to angle of attack protection law (AoA law). (rewritten from http://www.rvs.uni-bielefeld.de/publ...pdf_501275.pdf ) This actually happened and the aircraft involved zoom climbed at up to 6000fpm to above FL380.
[/from actual incident report]
[Speculation]
If that zoom occurs in an updraft it could be even faster but the aircraft would be capable of that rate on its own. Then at the apogee the speed would have bled off and the aircraft could stall.
As Machinbird (I think) suggested a compressor stall due to the AOA and poor airflow into one engine with the other at full power could change a stall into a spin accelerated by into spin power.
The autorotate and then tightening spin to a surveillance observer could look like a hard turn followed by a very fast descent at slow ground speed.
The resultant damage on hitting the surface of the ocean would look very similar to that which has been found. It is possible that the outside engine could eventually be shed due to the spin g forces.
[/Speculation]
From other Airbus experiences (and I am open to correction) the turbulence and fluctuating outside air temperature fluctuation lead to autopilot disconnect if the angle of attack then reaches the 'alpha prot' value. The angle of attack excursion beyond alpha prot causes a change in the pitch flight control law from normal law (NZ law) to angle of attack protection law (AoA law). (rewritten from http://www.rvs.uni-bielefeld.de/publ...pdf_501275.pdf ) This actually happened and the aircraft involved zoom climbed at up to 6000fpm to above FL380.
[/from actual incident report]
[Speculation]
If that zoom occurs in an updraft it could be even faster but the aircraft would be capable of that rate on its own. Then at the apogee the speed would have bled off and the aircraft could stall.
As Machinbird (I think) suggested a compressor stall due to the AOA and poor airflow into one engine with the other at full power could change a stall into a spin accelerated by into spin power.
The autorotate and then tightening spin to a surveillance observer could look like a hard turn followed by a very fast descent at slow ground speed.
The resultant damage on hitting the surface of the ocean would look very similar to that which has been found. It is possible that the outside engine could eventually be shed due to the spin g forces.
[/Speculation]
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Quote from Nigel on Draft
"6000fpm is the low 30K's is quite possible in an A320, and does not need an "updraft"."
What would the g loading be at this ROC and would envelope protection not say computer says NO.
Likely cause of such ROC must be exceptionally powerfull updrafts in the storm cell.
Can anyone corroborate how far away from the main wreckage the radome was found. In an earlier post someone had mentioned a figure which seemed rather implausible.
"6000fpm is the low 30K's is quite possible in an A320, and does not need an "updraft"."
What would the g loading be at this ROC and would envelope protection not say computer says NO.
Likely cause of such ROC must be exceptionally powerfull updrafts in the storm cell.
Can anyone corroborate how far away from the main wreckage the radome was found. In an earlier post someone had mentioned a figure which seemed rather implausible.
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Are inertial guidance or GPS speed and climb rates -as opposed to airspeed and barometric indications - written to the flight recorder?
It might be time to have flight recorders that can record weather radar patterns ...
It might be time to have flight recorders that can record weather radar patterns ...
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From other Airbus experiences (and I am open to correction) the turbulence and fluctuating outside air temperature fluctuation lead to autopilot disconnect if the angle of attack then reaches the 'alpha prot' value. The angle of attack excursion beyond alpha prot causes a change in the pitch flight control law from normal law (NZ law) to angle of attack protection law (AoA law).
- In Normal Law the high AoA will leas to an AP disconnect (would need to look up when exactly)
- If Alpha Prot is exceeded then "Normal Law's AoA protection" means that stick neutral holds Alpha Prot, and Stick Full Aft holds Alpha Max, and proportionally between.
- Thus if you get into this protection, and do nothing (let go), the aircraft will maintain Alpha Prot. If power is high (and will be if Alpha Floor has been triggered), this is not far off equating to a "Max Angle of Climb"
- This is one area trained for, since it requires a positive and slightly unnatural recovery - you need to push forward to reduce AoA below Alpha Prot and return to Normal Law's usual pitch control (stick v 'g')
- You also need to get out of Alpha Floor (max power wherever TLs are)
If you assume it took some level of "lack of SA" and distraction to get into the situation, the multitude of warnings is unlikely to immediately improve SA
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"6000fpm is the low 30K's is quite possible in an A320, and does not need an "updraft"."
What would the g loading be at this ROC and would envelope protection not say computer says NO.
Likely cause of such ROC must be exceptionally powerfull updrafts in the storm cell.
What would the g loading be at this ROC and would envelope protection not say computer says NO.
Likely cause of such ROC must be exceptionally powerfull updrafts in the storm cell.
What envelope protection would intervene? There is no "RoC Protection"? 6000'/m is easily achievable to low altitude, but not usually high up due reduced thrust. All my "scenario" involves is an increasing HW to substitute for the IAS loss. Put another way, the high RoC (increasing PE) is obtained by loss of KE (measured v GSpd) - the key is the increasing HW (temporarily) maintains IAS = AP target.
It does not need to be an updraft.
Supposed Latest
"World News
AirAsia Jet Climbed at Rate Beyond Design of Commercial Planes
Plane Climbed at Rate of More Than 8,000 Feet a Minute, Transport Minister Says"
If this is the latest from Indonesia, it's meaningless nonsense and all we know is that it climbed rapidly and stalled. The ambiguity re instantaneous and average climb rate, and climb speed is obvious (GS or CAS). Any one or a combination of zoom climb, windshear, temperature change, updraft, loss of control, is sufficient to explain a higher than normal rate of climb bleeding into a stall. At the moment any figures remain dubious as we don't have the confirmed source of the figures or confirmation of the readings.
"World News
AirAsia Jet Climbed at Rate Beyond Design of Commercial Planes
Plane Climbed at Rate of More Than 8,000 Feet a Minute, Transport Minister Says"
If this is the latest from Indonesia, it's meaningless nonsense and all we know is that it climbed rapidly and stalled. The ambiguity re instantaneous and average climb rate, and climb speed is obvious (GS or CAS). Any one or a combination of zoom climb, windshear, temperature change, updraft, loss of control, is sufficient to explain a higher than normal rate of climb bleeding into a stall. At the moment any figures remain dubious as we don't have the confirmed source of the figures or confirmation of the readings.
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Time
HT to Nigel's few well chosen words that allow me to cut my post by 90%: “...the multitude of warnings is unlikely to immediately improve SA”
A decision chain leading to an accident can be long or very short. The last possible chance to avoid an accident comes between the last two decisions of that chain. If the time available for all decisions or just the last two is seconds, or even virtually instantaneous as some scenarios posted suggest as possible, automation resulting in info and sensory overload probably contributes to an accident. Those are different and relatively rare scenarios compared to when pilots have enough time and automation is helpful.
A decision chain leading to an accident can be long or very short. The last possible chance to avoid an accident comes between the last two decisions of that chain. If the time available for all decisions or just the last two is seconds, or even virtually instantaneous as some scenarios posted suggest as possible, automation resulting in info and sensory overload probably contributes to an accident. Those are different and relatively rare scenarios compared to when pilots have enough time and automation is helpful.
Agreed. As usual, time is of the essence. Even CRM does not always work when there are only a few seconds available to make the decision. It can just impede the advantage of the commander's alleged, superior, experience.
SA in rapid decision making is a vexed question and there are no simple solutions. However computers now do beat humans at chess and lately poker, which has a high and ambiguous SA. The trend is obvious.
SA in rapid decision making is a vexed question and there are no simple solutions. However computers now do beat humans at chess and lately poker, which has a high and ambiguous SA. The trend is obvious.
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Originally Posted by rgbrock1
Is it possible, or even likely, for a severe updraft to carry a commercial airliner to that rate of ascent? Just curious.
Originally Posted by fireflybob
Assuming the data comes from the pressure instruments (IAS/VSI/ALT) these would be indicated values.
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Any one or a combination of zoom climb, windshear, temperature change, updraft, loss of control, is sufficient to explain a higher than normal rate of climb bleeding into a stall.
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Does that sort of "statistical analysis" inform the decisions in a given company on how much emphasis (and thus resources) to put on above mentioned upset training?
Is there even a duty to store and share accident related raw data or just the final report? For instance does Airbus have a legal right to the entire unfiltered FDR/CVR data here? Does the BEA (now EASA perhaps) as certifying body?
No aircraft is immune from stalling Finding Nemo. The bus tries to help you not get into that corner of the envelope. Unfortunately a lot of people think that in Normal law the bus is immune to the laws of Physics and Mother Nature
From the FCTM-
High AOA protection enables the PF to pull the sidestick full aft in dangerous situations, and thus consistently achieve the best possible aircraft lift. This action on the sidestick is instinctive, and the high AOA protection minimises the risk of stalls or control loss.
High AOA protection is an aerodynamic protection:
The PF will notice if the normal flight envelope is exceeded for any reason, because the autopitch trim will stop, the aircraft will sink to maintain its current AOA (alpha PROT, strong static stability), and a significant change in aircraft behavior will occur.
If the PF then pulls the sidestick full aft, a maximum AOA (approximately corresponding to CL Max) is commanded. In addition, the speedbrakes will automatically retract, if extended.
OPERATIONAL RECOMMENDATIONS:
When flying at alpha max, the PF can make gentle turns, if necessary.
The PF must not deliberately fly the aircraft in alpha protection, except for brief periods, when maximum maneuvering speed is required.
If alpha protection is inadvertently entered, the PF must exit it as quickly as possible, by easing the sidestick forward to reduce the angle-of-attack, while simultaneously adding power (if alpha floor has not yet been activated, or has been cancelled). If alpha floor has been triggered, it must be cancelled with the instinctive disconnect pushbutton (on either thrust lever), as soon as a safe speed is resumed.
In case of GPWS/SHEAR:
Set the thrust levers to TOGA
Pull the sidestick to full aft (For shear, fly the SRS, until full aft sidestick).
Initially maintain the wings level
This immediately provides maximum lift/maximum thrust/minimum drag. Therefore, CFIT escape maneuvers will be much more efficient.
From the FCTM-
High AOA protection enables the PF to pull the sidestick full aft in dangerous situations, and thus consistently achieve the best possible aircraft lift. This action on the sidestick is instinctive, and the high AOA protection minimises the risk of stalls or control loss.
High AOA protection is an aerodynamic protection:
The PF will notice if the normal flight envelope is exceeded for any reason, because the autopitch trim will stop, the aircraft will sink to maintain its current AOA (alpha PROT, strong static stability), and a significant change in aircraft behavior will occur.
If the PF then pulls the sidestick full aft, a maximum AOA (approximately corresponding to CL Max) is commanded. In addition, the speedbrakes will automatically retract, if extended.
OPERATIONAL RECOMMENDATIONS:
When flying at alpha max, the PF can make gentle turns, if necessary.
The PF must not deliberately fly the aircraft in alpha protection, except for brief periods, when maximum maneuvering speed is required.
If alpha protection is inadvertently entered, the PF must exit it as quickly as possible, by easing the sidestick forward to reduce the angle-of-attack, while simultaneously adding power (if alpha floor has not yet been activated, or has been cancelled). If alpha floor has been triggered, it must be cancelled with the instinctive disconnect pushbutton (on either thrust lever), as soon as a safe speed is resumed.
In case of GPWS/SHEAR:
Set the thrust levers to TOGA
Pull the sidestick to full aft (For shear, fly the SRS, until full aft sidestick).
Initially maintain the wings level
This immediately provides maximum lift/maximum thrust/minimum drag. Therefore, CFIT escape maneuvers will be much more efficient.
Last edited by tubby linton; 20th Jan 2015 at 23:32.
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@ Finding Nemo
Everything will work just fine if everything works as designed and you stay more or less in the normal flight enveloppe..
Extreme turbulence, or updraft, Sensor failure single or multiple, Sensor icing, single or multiple, autopilot desengage, multiple and conflicting warnings going off, pilots over saturation, and it goes downhill fast.
How many cars bang into each other because they are on cruise control?
How many trucks bang into cars because they are on cruise control?
The sensors => Automatic systems => Human interface => Results do not Always live up to its safety increasing expectations.
The more sensors, the more prone the system becomes to conflicting information and ultimately to desengaging or failure.
PS; IMHO for cars and trucks, cruise control should have been banned a long - long time ago.
Everything will work just fine if everything works as designed and you stay more or less in the normal flight enveloppe..
Extreme turbulence, or updraft, Sensor failure single or multiple, Sensor icing, single or multiple, autopilot desengage, multiple and conflicting warnings going off, pilots over saturation, and it goes downhill fast.
How many cars bang into each other because they are on cruise control?
How many trucks bang into cars because they are on cruise control?
The sensors => Automatic systems => Human interface => Results do not Always live up to its safety increasing expectations.
The more sensors, the more prone the system becomes to conflicting information and ultimately to desengaging or failure.
PS; IMHO for cars and trucks, cruise control should have been banned a long - long time ago.
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Some years ago I was flying an A320 through France ,southbound .
We were riding the core of a very tight jet stream at 330 ,with about 100 kts tailwind , ATC advised turbulence in 20nm so we requested 370 to avoid .
The aircraft was light so no problem . The initial climb at 1500 fpm was ok ,but as we exited the side of the jet into about 50 kts less tailwind the roc increased to 6000 fpm with speed increasing rapidly.
Even with rapid disconnect and gentle handling we zoomed through 390 and topped out at 400 at which point the indicated airspeed fell back rapidly.
We had little time to think about what was going on and traffic and ATC were an issue . Firm but gentle handling got us safely back to 370 .
The event was reported ASR and put down to unusually extreme wind gradient .
not saying this was the case here but perhaps we are not always aware of the potential of a jet upset due to upper air boundaries.
We were riding the core of a very tight jet stream at 330 ,with about 100 kts tailwind , ATC advised turbulence in 20nm so we requested 370 to avoid .
The aircraft was light so no problem . The initial climb at 1500 fpm was ok ,but as we exited the side of the jet into about 50 kts less tailwind the roc increased to 6000 fpm with speed increasing rapidly.
Even with rapid disconnect and gentle handling we zoomed through 390 and topped out at 400 at which point the indicated airspeed fell back rapidly.
We had little time to think about what was going on and traffic and ATC were an issue . Firm but gentle handling got us safely back to 370 .
The event was reported ASR and put down to unusually extreme wind gradient .
not saying this was the case here but perhaps we are not always aware of the potential of a jet upset due to upper air boundaries.
Last edited by zorin; 21st Jan 2015 at 13:12.
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Vilters, the analogy with car cruise control is closer to the mark than you perhaps intend. It leads to complacency. People set cruise control in situations where they should have their foot hovering over the brakes. Of course now there is radar linked braking available in the latest models. For aircraft, pilots who spend most of their time turning knobs on regular short flights on the same route, they too can become complacent. The Colgan Air case is a good example. The best pilots are always thinking about 'what if' scenarios, but fatigue, a domestic dispute, financial stress, alcohol and a ton of other things can leave any person with dulled responses. This is always a hidden factor with mistakes. It is also why HAL needs to be given more responsibility, not less. The sensors on the human will fail before HAL loses all SA. AF447 may have had frozen pitot tubes but it was the human that commanded the THS to its stop.
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Attention
ekw...Are there not studies showing it is also more difficult to maintain the same degree of vigilance and attentiveness when overseeing an automated system compared to constant manual control, difficulty being a slightly different metric than outside stresses?
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ekw makes some fine points , which is why pilots should be well paid and not have to have second income sources and take care of all problems including rest before flight, honorable retirement and health care and have nothing but flying the plane on their mind.
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If someone is idle with almost no stress, their attention level drops to its lowest level, if someone is extremely busy with high stress the attention level drops - sometimes called attentional or cognitive tunneling (tunnel vision). The ideal is a medium level stress that keeps the mind stimulated but not over worked.
See Yerkes?Dodson law - Wikipedia, the free encyclopedia and numerous other references.
Just a reminder that high alt windshear and jet streams are not usually found in the ITCZ region. Nor is hail. The most probable w/x related upset is violent convective turbulence and heavy rain. Microbursts are common but at lower altitudes. CBs are just plain dangerous in the ITCZ.
Last edited by RifRaf3; 21st Jan 2015 at 02:03.
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Studies
IanW: Indeed there are...... Yerkes and Dodson developed ...the inverted U.
My point is also asking whether a person overseeing an automated system has "farther to go" to catch up specifically in the case of very rapidly changing events. In all but rare cases this wouldn't matter because time available allows it, as low accident rates show. But in a very rapidly developing situation is there a response time penalty for all pilots flying in an overseer role compared to a hand flying role? If so at what point does that time penalty become long enough that success or failure is determined by it? Another way to put it would be to ask at what point the rapidity of events cascades to apparently become insurmountable in the "success" time available, comparing overseer and hand piloting roles. I think a lot of people would attest that there is a rhythm to flying, where one is physically as well as mentally engaged.
My point is also asking whether a person overseeing an automated system has "farther to go" to catch up specifically in the case of very rapidly changing events. In all but rare cases this wouldn't matter because time available allows it, as low accident rates show. But in a very rapidly developing situation is there a response time penalty for all pilots flying in an overseer role compared to a hand flying role? If so at what point does that time penalty become long enough that success or failure is determined by it? Another way to put it would be to ask at what point the rapidity of events cascades to apparently become insurmountable in the "success" time available, comparing overseer and hand piloting roles. I think a lot of people would attest that there is a rhythm to flying, where one is physically as well as mentally engaged.