A320 the big flaw of the UNRELIABLE SPEED/ADR CHECK procedure
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A320 the big flaw of the UNRELIABLE SPEED/ADR CHECK procedure
After studying the issue for years (not only the procedure but also the FCTM, other airbus publications, powerpoint presentations) and over two hours of LPC simulator dedicated to this issue, I have come to the conclusion that there is a big flaw on it:
How can we tell if the altitude information is affected or not???
The procedure will soon lead you to this. Inmediately if "safe conduct of the flight" is not affected or after the memory items if it is:
LEVEL OFF for trouble shooting
HOW ON EARTH CAN I DO THAT IF I DON'T RELY ON THE DAMNED ALTIMETEEEEEERS???
I don't have GPS in my fleet, right now. Nor I have that new gadget, the BUSS, which looks like a very good thing and apparently is fitted in the 380s.
Is there any method to determine if the static part of the air data is OK or not?
I mean: are there different modes of static air data failure? Or there is only one mode, where V/S remains zero no matter how fast you climb or descend and then is totally obvious that static data is un reliable?
By the way, I never have this problem in the sim because it cannot simulate problems in the static. only in the pitot.
How can we tell if the altitude information is affected or not???
The procedure will soon lead you to this. Inmediately if "safe conduct of the flight" is not affected or after the memory items if it is:
LEVEL OFF for trouble shooting
HOW ON EARTH CAN I DO THAT IF I DON'T RELY ON THE DAMNED ALTIMETEEEEEERS???
I don't have GPS in my fleet, right now. Nor I have that new gadget, the BUSS, which looks like a very good thing and apparently is fitted in the 380s.
Is there any method to determine if the static part of the air data is OK or not?
I mean: are there different modes of static air data failure? Or there is only one mode, where V/S remains zero no matter how fast you climb or descend and then is totally obvious that static data is un reliable?
By the way, I never have this problem in the sim because it cannot simulate problems in the static. only in the pitot.
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I believe most a/c with IRUs use them for V/S instead of static.
Interestingly, a pneumatic IVSI, Instantaneous Vertical Speed Indicator, contains a small pendulum that starts tne needle in the correct direction to counter the delay inherent in the basic VSI.
GB
Interestingly, a pneumatic IVSI, Instantaneous Vertical Speed Indicator, contains a small pendulum that starts tne needle in the correct direction to counter the delay inherent in the basic VSI.
GB
Last edited by Graybeard; 7th Jun 2011 at 16:24. Reason: correction for IVSI
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scary comment above!
We have had some quite intensive training in this stuff over the last year, apart from regarding the basic pitch/power settings as memory items, we are advised to crosscheck alt with the GPS output.
We have had some quite intensive training in this stuff over the last year, apart from regarding the basic pitch/power settings as memory items, we are advised to crosscheck alt with the GPS output.
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the other flaw is
what the heck is "if safe conduct of the flight is affected"
In my opinion, every time you have an unreliable speed safety is inherently affected. For all you know, you could be on the verge of stall, or overspeed, or a spiral dive or whatever.
If you have unreliable speed at 390, in turbulence at night with hail hitting the windshield, your body giving you all kind of misleading inputs to your brain... Is the safe conduct of the flight affected? I would say "yes it is" so i would have to take over manually and set pitch at 5º and CLB thrust? I don't think so...
They have to enhance the procedure (maybe including more "emergency" pitch-thrust settings: for high level climb, cruise or descend. These are on the tables but not on the memory items.
They can also develop a tool to give inertial V/S in the MCDU (altitude is secondary. V/S is what we need)
Then we can always level off.
One last thought:
What if the Air France 330 was in overspeed, or even well beyond it and when AP disconnected they set 5º up all of a sudden? let's say a 4º increment in pitch at that level and that speed. This could explain the pitch up input.
what the heck is "if safe conduct of the flight is affected"
In my opinion, every time you have an unreliable speed safety is inherently affected. For all you know, you could be on the verge of stall, or overspeed, or a spiral dive or whatever.
If you have unreliable speed at 390, in turbulence at night with hail hitting the windshield, your body giving you all kind of misleading inputs to your brain... Is the safe conduct of the flight affected? I would say "yes it is" so i would have to take over manually and set pitch at 5º and CLB thrust? I don't think so...
They have to enhance the procedure (maybe including more "emergency" pitch-thrust settings: for high level climb, cruise or descend. These are on the tables but not on the memory items.
They can also develop a tool to give inertial V/S in the MCDU (altitude is secondary. V/S is what we need)
Then we can always level off.
One last thought:
What if the Air France 330 was in overspeed, or even well beyond it and when AP disconnected they set 5º up all of a sudden? let's say a 4º increment in pitch at that level and that speed. This could explain the pitch up input.
They can also develop a tool to give inertial V/S in the MCDU
http://www.pprune.org/tech-log/452973-fpv-fpv-cage.html
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If there are accelerometers and valid aTTitude, inertial V/S is easy to obtain.
Or they can install a dedicated accelerometer. There must be a thousand ways of achieving a reliable instrument to achieve zero vertical speed.
Or else, enlighten us how to rule out (or not) failed altitude/V/S data
Or they can install a dedicated accelerometer. There must be a thousand ways of achieving a reliable instrument to achieve zero vertical speed.
Or else, enlighten us how to rule out (or not) failed altitude/V/S data
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On a recent A320 sim-check, we had the following scenario :
In T/O just after rotation, we got 2 unreliable ADR`s, that both had the same failure of increasing airspeed, rapidly increasing to above 400 kts.
That means, that even though they are faulty, they wote out the remaining good ADR.
And what happens on the A320 in an overspeed situation : VMO/MMO + xx kts/0.xx mach, the A/C starts to pitch up, even though you manually try to pitch down !
And even more scary, with A/THR engaged, it reduce to idle due to higher speed than targetspeed. (We are not quite sure if this a "simulator thing" that it reduces to idle, can`t find anything about it in the books. Anyone confirm ??)
So with a rapidly increasing pitch and thrust at idle, things start to evolve very very quickly ! (and in this scenario very close to the ground). You have to do the following quickly, not a memory item (we are talking seconds) :
Solution : Select 2 ADR`s to off (doesn`t mean anything which two) and then you can apply the pitch/power procedure.
In T/O just after rotation, we got 2 unreliable ADR`s, that both had the same failure of increasing airspeed, rapidly increasing to above 400 kts.
That means, that even though they are faulty, they wote out the remaining good ADR.
And what happens on the A320 in an overspeed situation : VMO/MMO + xx kts/0.xx mach, the A/C starts to pitch up, even though you manually try to pitch down !
And even more scary, with A/THR engaged, it reduce to idle due to higher speed than targetspeed. (We are not quite sure if this a "simulator thing" that it reduces to idle, can`t find anything about it in the books. Anyone confirm ??)
So with a rapidly increasing pitch and thrust at idle, things start to evolve very very quickly ! (and in this scenario very close to the ground). You have to do the following quickly, not a memory item (we are talking seconds) :
Solution : Select 2 ADR`s to off (doesn`t mean anything which two) and then you can apply the pitch/power procedure.
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hadn't thought of that one!
regarding the thrust, if in SPEED, thrust will kept at idle as long as speed is much faster than target.
So in this case the high speed protection is trying to kill us. Taking over manually solves the A/THR comanding idle thrust problem, but what about the high speed protection!
how come thre is nothing in the procedure about this? what are we missing?
after rejecting one ADR we still have normal law, so it makes sense.
regarding the thrust, if in SPEED, thrust will kept at idle as long as speed is much faster than target.
So in this case the high speed protection is trying to kill us. Taking over manually solves the A/THR comanding idle thrust problem, but what about the high speed protection!
how come thre is nothing in the procedure about this? what are we missing?
after rejecting one ADR we still have normal law, so it makes sense.
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In Normal Law, Alpha ('Stall') protection "overrides" High Speed protection.
In Alternate Law, if High Speed protection is available (it is not always), it is "reduced", which means (IIRC) you can "overpower" it with e.g. full fwd stick.
Thus within the Flt Ctrl Laws, the High Speed protection should not be able to pull the nose up into/beyond the stall.
Of course, other factors e.g. THS position, CG, further malfunctions, Crew reaction time, may mean a stall can occur... all I am saying is the simple "aircraft uncontrollably pitched up into a stall and nothing anyone could do about it" line is not 100% valid
NB I am talking A320 series here - A330 may be different (but doubt it fundamentally).
In Alternate Law, if High Speed protection is available (it is not always), it is "reduced", which means (IIRC) you can "overpower" it with e.g. full fwd stick.
Thus within the Flt Ctrl Laws, the High Speed protection should not be able to pull the nose up into/beyond the stall.
Of course, other factors e.g. THS position, CG, further malfunctions, Crew reaction time, may mean a stall can occur... all I am saying is the simple "aircraft uncontrollably pitched up into a stall and nothing anyone could do about it" line is not 100% valid
NB I am talking A320 series here - A330 may be different (but doubt it fundamentally).
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Why do people get wound up about unreliable airspeed in the cruise?
When you get to cruise make a note of the pitch attitude and N1 setting?
If you get Unreliable airspeed, you have the couple that was working fine to start with.
Or turn to 2.21 of the QRH, go to the bottom of the page and cross reference......
CLEAN - FL - SPEED - WEIGHT - PITCH/THRUST at your current weight.
Read across the pitch/thrust tables until yours match! Its all in front of you and always has been.
(While you're at it, note the LRC and green dot driftdown flight levels in case.)
When you get to cruise make a note of the pitch attitude and N1 setting?
If you get Unreliable airspeed, you have the couple that was working fine to start with.
Or turn to 2.21 of the QRH, go to the bottom of the page and cross reference......
CLEAN - FL - SPEED - WEIGHT - PITCH/THRUST at your current weight.
Read across the pitch/thrust tables until yours match! Its all in front of you and always has been.
(While you're at it, note the LRC and green dot driftdown flight levels in case.)
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Of course
Im sure that maintaining altitude with 2.5 or 3 degrees and about 85% N1 will give you about .76 at most of the typical flight levels and weights in cruise.
But they should include a pitch and thrust for cruise in the memory items.
And the level off critical question remains?
"Am I levelling off or is something in the air data system fooling me and leading me to disaster?"
I wonder if there is any means (other than GPS) to rule out a problem in altitude indication before leveling off for the trouble shooting
Im sure that maintaining altitude with 2.5 or 3 degrees and about 85% N1 will give you about .76 at most of the typical flight levels and weights in cruise.
But they should include a pitch and thrust for cruise in the memory items.
And the level off critical question remains?
"Am I levelling off or is something in the air data system fooling me and leading me to disaster?"
I wonder if there is any means (other than GPS) to rule out a problem in altitude indication before leveling off for the trouble shooting
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Hi Microburst2002,
I think this is because, pitots can clog with ice, nesting wasps, bird strike, or be unreliable with radome damage etc.
The only static ports problem I can think of is if they have been taped over by maintenance / engineering. Your outside check before flight should prevent the last case.
Otherwise if IMC, and no GPS data - I can't see how you would determine if you have levelled off either.
By the way, I never have this problem in the sim because it cannot simulate problems in the static. only in the pitot.
The only static ports problem I can think of is if they have been taped over by maintenance / engineering. Your outside check before flight should prevent the last case.
Otherwise if IMC, and no GPS data - I can't see how you would determine if you have levelled off either.
Last edited by rudderrudderrat; 12th Jun 2011 at 14:56. Reason: plural static ports
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For me, the "level off" part means you are not climbing/descending at XXXX ft/min, which could affect your speed (a'la AF447's climb at 7000ft/min). Setting pitch at ~2.5 deg and thrust of 85% (or the pitch/thrust setting from the QRH), ensures that you are leveled off, or at least close enough for practical purposes and is more important than what the altimiter says. Even if you have one, you should hold the pitch, power, not the altitude...
Last edited by Stuck_in_an_ATR; 11th Jun 2011 at 10:44.
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Setting 2.5Deg pitch and 85% N1 close to coffin corner and slow on speed, hockey stick territory (which you wouldn't know if you didn't have the cue of yoke pressure) will not suffice in recovering the situation.
Therefore holding the pitch to recover the stall isn't always best advice especially at high alt with little margins
Therefore holding the pitch to recover the stall isn't always best advice especially at high alt with little margins