Air Asia Indonesia Lost Contact from Surabaya to Singapore
Hardly Never Not Unwilling
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I fly the A320, and recently received guidance that when Sparky (the mysterious French brain that protects us from screwing things up) is directing unsustainable nose up or down auto commands, you press off two of the three ADIR push-buttons.
My bible is to turn off all the automation when things start to spin out of control. It will fly like an airplane if you allow it.
With experience (now about 10 years on Airbus), I've found, less and less do I question, 'Why is Sparky doing that?', as I know as soon as I ask myself the question.
One thing I inwardly shudder about, though, is that under the seniority system of the major airlines flying the A320, you can have the situation of a brand new Captain coming from an old Boeing with no Airbus experience, and a new FO who knows next to nothing, dealing with the surprises Airbus will throw at you.
My bible is to turn off all the automation when things start to spin out of control. It will fly like an airplane if you allow it.
With experience (now about 10 years on Airbus), I've found, less and less do I question, 'Why is Sparky doing that?', as I know as soon as I ask myself the question.
One thing I inwardly shudder about, though, is that under the seniority system of the major airlines flying the A320, you can have the situation of a brand new Captain coming from an old Boeing with no Airbus experience, and a new FO who knows next to nothing, dealing with the surprises Airbus will throw at you.
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There is a comment on another forum that uncommanded rudder is suspected. But even if the rudder was at full deflection could this not be counteracted and control maintained through engine power and aileron input?
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YAW on A320
The rudder damper system is (usually) designed to prevent excessive rudder deflection at high speeds in a mechanical flight control system. In a fly by wire system that is taken care of in software.
Yaw damper is designed to "damper" yaw movements not to limit rudder deflection. RTLU (Rudder Travel Limiting Unit) is there to limit mechanically the rudder deflection depending of A/C speed, this units (double) are driven by FAC's fonction of speed information from ADR's.
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YAW
The rudder is sized to provide sufficient rudder power to overcome a worst case yaw deflection at or near stall speed.
At all.
Uncommanded rudder trim would cause a nose down dive and a sharp turn. (Or possibly a fin separation again with a dive and sharp turn)
Here we have a massive climb and at a very wide turn until very late in the event.
So: You can probably scrap rudder trim runaway in this case. Doesn't seem to fit to what we know so far.
If boom mics are worn and designed to stay on during severe turbulance! they remain the best solution.
The overhead mounted ambient mics with an omnidirectional pickup pattern cant be expected to recieve the pilots voice clearly when pilot is looking at instruments and when the warning speakers are direct line of sight to the mic.
A couple of panel mounted directional mics each aimed directly at where the pilot and FO is looking could be considered if boom mics cant be relied upon.
This will reduce background level relative to voice level. These mics and the ambient mic could be fitted with wind gags to eliminate the sound of air moving over the surface of the mic, so called "wind noise" that would otherwise greatly reduce the fidelity of the recording during a decompression or other event.
Cameras that show the crew mouths will help with deciphering what was spoken.
I guess that cvr use compression? Use of high rates of compression when there is lack of control over mic placement and background sound and when level control is "auto" is to be avoided. Compression trys to keep every hum and background noise (there is considerable background noise of air over the fuselage) at the expense of reducing amount of data to record the good stuff.
As with images, the less control of the subject the more beneficial it is to have a high fidelity equipment, in this case microphones and a recording strategy which allows far more detail to be extracted post event.
A camera looking into passenger cabin would be very useful to evaluate passenger response to emergencies including evacuation.
The overhead mounted ambient mics with an omnidirectional pickup pattern cant be expected to recieve the pilots voice clearly when pilot is looking at instruments and when the warning speakers are direct line of sight to the mic.
A couple of panel mounted directional mics each aimed directly at where the pilot and FO is looking could be considered if boom mics cant be relied upon.
This will reduce background level relative to voice level. These mics and the ambient mic could be fitted with wind gags to eliminate the sound of air moving over the surface of the mic, so called "wind noise" that would otherwise greatly reduce the fidelity of the recording during a decompression or other event.
Cameras that show the crew mouths will help with deciphering what was spoken.
I guess that cvr use compression? Use of high rates of compression when there is lack of control over mic placement and background sound and when level control is "auto" is to be avoided. Compression trys to keep every hum and background noise (there is considerable background noise of air over the fuselage) at the expense of reducing amount of data to record the good stuff.
As with images, the less control of the subject the more beneficial it is to have a high fidelity equipment, in this case microphones and a recording strategy which allows far more detail to be extracted post event.
A camera looking into passenger cabin would be very useful to evaluate passenger response to emergencies including evacuation.
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Yes I agree with you it seems most likely that the sharp turn was induced as a result of the stall. However the bus is supposed to be spin tolerant when stalled even in gusts or asymetric thrust. At least they have the FDR to analyse fully on this occasion.
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Nose dive
I am not an A man, so hardly dare to comment on the rudder behaviour. However, many years ago, in the early days of the 757, a slow L HYD leak required the system to be switched off until required for the approach. For some reason all our aircraft required a great deal of rudder trim in the cruise (later corrected). Having such a leak and following the QRH, the result was an immediate 30 to 40 degree wing down. The aircraft, though, maintained straight and level (altitude but not wings!) flight with us hanging in our straps until the L HYD was quickly switched back on again. There was no immediate nose dive at all. This was due to a full rudder deflection. Mr B informed us later that the ratio of rudder deflection reduces with speed by 15 times due to the RUDDER RATIO which, of course, was switched off by selecting L HYD OFF.
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One of the best techniques to keep an undesired FBW pitch up from bleeding off all your airspeed is to immediately drop a wing and convert pitch-up into turn. The little bus will let you get 67 degrees bank if you hold the stick over, right?
It may be that QZ8501 was doing that but got started too late and bled off too much speed and fell off onto the low wing in a stall.
For someone who flies the little 'bus:
How long do you think it would take to turn off two of the 3 computers if you were surprised by an undesired maneuver? I'm betting that it would be about 15 seconds from initial startle to Alternate Law-and that only if you were really on top of your game.
It may be that QZ8501 was doing that but got started too late and bled off too much speed and fell off onto the low wing in a stall.
For someone who flies the little 'bus:
How long do you think it would take to turn off two of the 3 computers if you were surprised by an undesired maneuver? I'm betting that it would be about 15 seconds from initial startle to Alternate Law-and that only if you were really on top of your game.
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The equivalent deflection ratio exists on the airbus apparently, the AP can command +/- 3 degrees of rudder deflection at high speed to +/- 30 degrees at low speed. When actuated any deviation from the track is compensated with opposing elevator and aileron but AP aileron authority is limited and under the fault conditions the craft cannot maintain track, manual control is required.
At first it seems surprising that the AP can command a rudder deflection that would defeat lateral navigation, but if you consider normal operation would be to compensate for weathercock due to high winds not compensation for a software anomaly.
At first it seems surprising that the AP can command a rudder deflection that would defeat lateral navigation, but if you consider normal operation would be to compensate for weathercock due to high winds not compensation for a software anomaly.
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Human performance in stress / startle
The sad but interesting parts of the CVR / DFR data analysis will be the human response to some of the alarms.
If, as in , say Colgan style, or AF, the PF response to stall was NOT nose down, due to startle or whatever, does there need to be in the alarm aural sequence, the loud and repetitive message "pitch nose down" announced ?
Although it it obvious and basic, it is clear in recent years that it is not automatically done. And if there are already aural warnings with ground prox saying "pull up" (mind you not helpful if aircraft in stall), by which stage the a/c is 3 - 5 seconds from impact, why not a message such as above which would be helpful, while the a/c may still be at salvageable altitude.
Of course avoiding getting into the stall is preferable in the first place.
Just my 2c worth as a pax with frequent interaction of stress situations.
If, as in , say Colgan style, or AF, the PF response to stall was NOT nose down, due to startle or whatever, does there need to be in the alarm aural sequence, the loud and repetitive message "pitch nose down" announced ?
Although it it obvious and basic, it is clear in recent years that it is not automatically done. And if there are already aural warnings with ground prox saying "pull up" (mind you not helpful if aircraft in stall), by which stage the a/c is 3 - 5 seconds from impact, why not a message such as above which would be helpful, while the a/c may still be at salvageable altitude.
Of course avoiding getting into the stall is preferable in the first place.
Just my 2c worth as a pax with frequent interaction of stress situations.
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@FlightDream111 thanks for that link - also useful is the FAA upset recovery link at FAA TV: Airplane Upset Recovery, Part 2
Its on tube as well : https://www.youtube.com/watch?v=gHf5XPO9wAA
The video shows what looks like a an A320 and cautions that air brake deployment may cause pitch up - is this true on the A 320?
Last edited by FlightDream111; 24th Jan 2015 at 00:18. Reason: you tube link
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aussiepax
I understand what you are getting at, but, believe it or not, if you are in a spin, in some planes, the nose is already down.
so, instead of saying: pitch nose down...it would be better if we all just PUSHED FORWARD ON THE STICK (control wheel or sidestick).
AND we should have learned this in our first lesson in a plane.
And Wolfgang Langweische, a great author of "stick and rudder" wrote about this over 70 years ago.
But you see, some smart ass somewhere said: oh, just ''relax back pressure"...and sometimes that is not enough.
So...here we are, 70 years AFTER
"STICK AND RUDDER" was published and we still don't get out of stalls right.
There is a good chance you will never have a problem...just ask your pilot : have you read, "stick and rudder"?
I understand what you are getting at, but, believe it or not, if you are in a spin, in some planes, the nose is already down.
so, instead of saying: pitch nose down...it would be better if we all just PUSHED FORWARD ON THE STICK (control wheel or sidestick).
AND we should have learned this in our first lesson in a plane.
And Wolfgang Langweische, a great author of "stick and rudder" wrote about this over 70 years ago.
But you see, some smart ass somewhere said: oh, just ''relax back pressure"...and sometimes that is not enough.
So...here we are, 70 years AFTER
"STICK AND RUDDER" was published and we still don't get out of stalls right.
There is a good chance you will never have a problem...just ask your pilot : have you read, "stick and rudder"?
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Henra: "Doesn't fit this scenario.
At all.
Uncommanded rudder trim would cause a nose down dive and a sharp turn."
Well said, Henra. Kudos. The available evidence says this aircraft traded speed for altitude, until it stalled. Why? That's the question. The rudder can't make it climb like that. Stop the rudder nonsense. I'm just a humble private pilot, but this is obvious.
At all.
Uncommanded rudder trim would cause a nose down dive and a sharp turn."
Well said, Henra. Kudos. The available evidence says this aircraft traded speed for altitude, until it stalled. Why? That's the question. The rudder can't make it climb like that. Stop the rudder nonsense. I'm just a humble private pilot, but this is obvious.
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Machinbird, One of the best techniques to keep an undesired FBW pitch up from bleeding off all your airspeed is to immediately drop a wing and convert pitch-up into turn. The little bus will let you get 67 degrees bank if you hold the stick over, right?
In 1991 a German crew finally learned this technique in "the hard way"
http://www.youtube.com/watch?feature...ViilcDTyw#t=10
Last edited by _Phoenix; 24th Jan 2015 at 02:20.
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If they have not tested the actual aircraft - it is only an assumption that the aircraft is 'spin tolerant' whatever that means. If you are actually at the point of stall and you have a compressor stall on one engine then that engine gives high drag and the other full thrust - this will stall the wing with the engine with compressor stall as it slows down relative to the other wing with full power. The aircraft starts to autorotate -
I believe there have been one or two events at altitude that prove this wrong
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Radar spiral/circle
Is there any possibility of narrowing by calculation the number of possible attitude scenarios regarding only the last spiral or circle on the radar track? Time involved is somewhat uncertain, but an estimate (or range of estimates) could be made of the number of returns which would help estimate the total time for the 360. That duration might be compared to the duration of a normal circle flown under control at zero descent rate which would also suggest an expected G rate relative to that turn. Or would adding the range of possible (or known) descent rates during the rotation include so many as to not be useful? Put another way, would radar turn indicated be equally possible in normal flight, stalled rotation, or intentional descending dive (I'm NOT suggesting the last...it is just part of the range possibilities.)
