AF447
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Mr Pitot
Funnilly enough, Mr Pitot invented a tube to measure fluid speeds,
and a Pitot tube measures "P tot "
ie total pressure = P Dynamic + P static !!
Year: 1732
Last edited by captainflame; 12th Jun 2009 at 15:40. Reason: Added info.
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Changing Pitot
Per Bloomberg, AF had the new pitot tubes in hand, and I'm sure I read early in the other thread that the accident plane was scheduled to get them on the next C check (approximate annual inspection.) IIRC, this plane had over 18,000 hours in about 4 years, an incredibly high rate of utilization. This leaves precious little time for non-routine maintenance at home base, such as changing pitot tubes.
You don't just change the pitot tubes and walk away; you then have to perform a full pressure-static check, including pneumatically pumping up the altitude to above max altitude, so you leave those changes for the C check if you can.
It must be quite a serious flaw in the pitot tubes that they have to be replaced with new ones, rather than re-worked. Safety review teams at Thales, Airbus and AF apparently did a cost/benefit analysis and came up with the wrong answer, if erroneous airspeed was the initial event.
GB
You don't just change the pitot tubes and walk away; you then have to perform a full pressure-static check, including pneumatically pumping up the altitude to above max altitude, so you leave those changes for the C check if you can.
It must be quite a serious flaw in the pitot tubes that they have to be replaced with new ones, rather than re-worked. Safety review teams at Thales, Airbus and AF apparently did a cost/benefit analysis and came up with the wrong answer, if erroneous airspeed was the initial event.
GB
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Tim's weather analysis
I am also very curious about the temperature "cliff" coming out of 3 updrafts in the turbuence. Could there have been a combination of wrong speed (pitot) and stall/fall with that cliff getting out of the turbulence? Isn't it really an exceptional situation (may be not weather wise, but flying wise since CBs are usually avoided), an hence not taken into account by computer/checklists? As for the "criminal investigation", it is an automatic administrative procedure here in France and does not imply that criminal behaviour is being suspected. Thanks - Gilles
As to why not make the changes mandatory instead of advisory, my guess is that there was an accountant sitting at the table. No disrespect to accountants - they're there to remind you that if you stop making a profit you'll end up on the dole.
.......................
An 'advisory' means that the airlines pay - if they care to. A 'mandatory' means that the manufacturers do.
.......................
An 'advisory' means that the airlines pay - if they care to. A 'mandatory' means that the manufacturers do.
Without supporting data it is useless to denigrate a party or person just to support a supposition.
Under continued airworthiness cost is not an issue (alternate means of compliance etc. accomodates this). The facts supporting the product safety issue are not yet in evidence to us although presumably they were to EASA. Just because a system may malfunction does not mean the aircraft is unsafe.
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FEHoppy, RE p. 122 BEA report
No that looks nothing like AF447, the rudder is damaged mid-section and is surrounded by leaked oil and hydro fluid from the rudder acuators likely. It appears to be cracked side to side about midway as well. IOW severe damage as expected to the structure of the tail section.
-drl
No that looks nothing like AF447, the rudder is damaged mid-section and is surrounded by leaked oil and hydro fluid from the rudder acuators likely. It appears to be cracked side to side about midway as well. IOW severe damage as expected to the structure of the tail section.
-drl
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Quote:-
"I'll ask this again: WHY are you messing with the rudder in cruise with or without turbulence? [Transport pilots only, please] Or, is this an Airbus technique? While it is 'proper' to try and keep the wings level, it is not necessary to keep the heading constant. Trying to maintain heading can lead to serious overloads."
I would hope that nobody here changes or maintains heading with the rudder...This would be done with aileron. The rudder pedals in jet airliners are just footrests in normal flight and should only be moved to push the ball back to the middle after engine failure, kicking off drift for landing and keeping straight on the runway centreline.
"I'll ask this again: WHY are you messing with the rudder in cruise with or without turbulence? [Transport pilots only, please] Or, is this an Airbus technique? While it is 'proper' to try and keep the wings level, it is not necessary to keep the heading constant. Trying to maintain heading can lead to serious overloads."
I would hope that nobody here changes or maintains heading with the rudder...This would be done with aileron. The rudder pedals in jet airliners are just footrests in normal flight and should only be moved to push the ball back to the middle after engine failure, kicking off drift for landing and keeping straight on the runway centreline.
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Ice has been a problem for aircraft since the early days. More recently the B777 at Heathrow and now A/B330. Perhaps in this high technology world the basics are not treated with due reverence or simply that mother nature continues to teach us not to lose sight of the rules.
On exercise away from base a pitot had a heater problem which was a no go item, one was robbed from an aircraft undergoing maintenance and fitted in the evening. The main problem was the curing time for the sealant during October in Scotland.
Despite only circumstantial evidence pointing to the pitot system, the evidence has been building up and it should not need the threat of pilot action to accelerate at least a minimum update fit. The balance between costs and safety has always been a tight rope but once a reasonable amount of evidence is there the right action should be taken - the consequences are far more serious.
On exercise away from base a pitot had a heater problem which was a no go item, one was robbed from an aircraft undergoing maintenance and fitted in the evening. The main problem was the curing time for the sealant during October in Scotland.
Despite only circumstantial evidence pointing to the pitot system, the evidence has been building up and it should not need the threat of pilot action to accelerate at least a minimum update fit. The balance between costs and safety has always been a tight rope but once a reasonable amount of evidence is there the right action should be taken - the consequences are far more serious.
JR
Isnt it this way on the 330:
One engine running, low current flow.
Airborne : high current flow,
provided by controllers.
What is the reason to use controllers,
when a simple "current relay" could do it,
like on all "vintage" aircrafts.
There is no "temp-feedback" from the sensors,
so why "controllers"?
Isnt it this way on the 330:
One engine running, low current flow.
Airborne : high current flow,
provided by controllers.
What is the reason to use controllers,
when a simple "current relay" could do it,
like on all "vintage" aircrafts.
There is no "temp-feedback" from the sensors,
so why "controllers"?
I can't answer that one way or the other, as my own experience is on Hawkers, Gulfstreams, (older) Boeings and Lears - which either have fully manual control of probe heat - or weight-on-wheels coupled automatic heater on/off. (With manual overide available).
Windscreen heat is another matter - all electrical windscreen heating systems I've encountered do employ variable current controllers regulated by temperature feedback from thermistors embedded in the glass.
If I were a pilot, I think I'd much prefer to have full control of each probe's heater circuit individually (via dedicated switches) rather than a single anti-ice switch controlling multiple probes.
In any case, I leave it to an engineer with Airbus experience to shed light on the specifics of the AUTO mode on that airframe.
JR Barrett
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JRBarrett -
There we go again....."automatic". I never flew an airplane that had that. We had a Checklist that had Pitot Heat on it. Simple. In other words, no problem having it on while on the ground. And the 'automatic' portion (which there was none) couldn't fail.
The "automatic" mode is used to prevent electrically-heated sensors (pitot probes, AOA vanes, TAT probes etc.) from being switched "on" when the aircraft is on the ground.
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For those who are interested in the basics behind a330 probe heating
Monitoring
The PHC monitors heating of the static probes, AOA sensor, pitot probes and TAT sensor. Current detection with a preset threshold is provided for monitoring purposes.
Low heating or overcurrent or heating loss triggers a warning.
Monitoring of the TAT sensors is inhibited on the ground.
A monitoring system activates a warning when heating is incorrect. Warning is triggered as follows:
(a)
For pitot probe
-
in flight when the current I is lower than 0.9A or greater than 6A
-
on ground when the current I is lower than 0.4A or greater than 4A.
(b)
For TAT sensor
When the current I is lower than 0.8A or greater than 4A.
(c)
For AOA sensor
When the current I is lower than 0.12A or greater than 5A.
(d)
For L and R static probes
When the current is lower than 1.3A or greater than 4A.
The PHC serves to:
-
identify the faulty element(s),
-
memorize the faulty element.
(2)
Indication
The PHC continuously emits signals via the ARINC 429 bus (low speed).
A discrete output (one per probe) informs the ADIRU of associated probe channel of the heating fault. Then, the ADIRU informs the Flight Warning Computer (FWC).
Monitoring
The PHC monitors heating of the static probes, AOA sensor, pitot probes and TAT sensor. Current detection with a preset threshold is provided for monitoring purposes.
Low heating or overcurrent or heating loss triggers a warning.
Monitoring of the TAT sensors is inhibited on the ground.
A monitoring system activates a warning when heating is incorrect. Warning is triggered as follows:
(a)
For pitot probe
-
in flight when the current I is lower than 0.9A or greater than 6A
-
on ground when the current I is lower than 0.4A or greater than 4A.
(b)
For TAT sensor
When the current I is lower than 0.8A or greater than 4A.
(c)
For AOA sensor
When the current I is lower than 0.12A or greater than 5A.
(d)
For L and R static probes
When the current is lower than 1.3A or greater than 4A.
The PHC serves to:
-
identify the faulty element(s),
-
memorize the faulty element.
(2)
Indication
The PHC continuously emits signals via the ARINC 429 bus (low speed).
A discrete output (one per probe) informs the ADIRU of associated probe channel of the heating fault. Then, the ADIRU informs the Flight Warning Computer (FWC).
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> Great idea, but as long at the Pilot Unions are worried about airlines reviewing this data and then taking action against pilots after flights - this will never happen.
Yeah, sending cvr/fdr data at 20 min. intervals would seem like a big privacy problem with little practical gain. After all, I would think that the 5-10 minutes before an incident is where the most important info tends to be found. Hence one can generally send all of the ROUTINE info but none of the important stuff.
Furthermore, the costs of such a thing would be very large for dubious benefit.
Yeah, sending cvr/fdr data at 20 min. intervals would seem like a big privacy problem with little practical gain. After all, I would think that the 5-10 minutes before an incident is where the most important info tends to be found. Hence one can generally send all of the ROUTINE info but none of the important stuff.
Furthermore, the costs of such a thing would be very large for dubious benefit.
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Regarding GPS and vehicle status information
I've noticed a fair number of non-pilots mumbling about GPS as if they think it tells you everything about where the plane is and how fast it's going. It's time to put some details on the record.
First, GPS tells you nothing about where you are. It tells you where you were at the time of the last measurement. With an automobile we're speaking of discrepancies that are not worth thinking about. With a high dynamics aircraft (fighter) the difference between where you are and where GPS alone tells you can be more than slightly significant. GPS alone even has difficulty tracking through typical military fighter aircraft moves. With C/A code tracking it's just about worthless. That is why the military has its P-code (and encrypted Y-code).
This lag and inability to track is mitigated to a high degree via software and other inputs, the IMU and IRU for example. Kalman filters can generate enough accuracy to feed back a position estimate to the GPS receiver that the receiver can maintain lock, if not accuracy.
Still, the whole system tells you where you were and where it thinks you might be based on projections not where you are.
GPS is even worse at telling you your speed, although it can do so. It can take where you were at two times and divide by the time to get a velocity vector. If it smooths that over time it can be reasonably accurate.
That brings up "time" as your enemy. The longer you integrate the GPS tracking feedback loops (the lower their bandwidth) the more accurate the data. Noise is the enemy. Fortunately GPS is designed to work WITH jamming efforts. And jamming is just another word for noise. So there is a potentially very large margin for unjammed GPS to be very accurate, especially in relative positions over a short time frame.
Now consider the plane is in heavy turbulence. The filters are prepared to handle this. Civilian aircraft don't do aerobatics. They fly sanely, even in turbulence the flight is fairly sane, it cannot be called aerobatics with spins. rolls, and other rapid motion changes. So far the GPS plus other information sources can give you reasonably good estimates of where you're going, how fast, and where you are. To be sure it's accuracy is fading. But you are within the design parameters for all the instruments and software involved.
Note that I've not said a thing about heading, yaw, or pitch of the plane itself. GPS CAN make an estimate if you have antennas on the nose, tail, and both wing tips. It might even be a good guess using phase tracking tricks. Theoretically it's possible. And with computers these days it may even be practical if calibration tables for cable measured temperature versus delay time is carried and usable. I'd not bet on it.
Now throw the plane into a spiral dive or a flat spin or almost any other controlled or uncontrolled aerobatic movement. Civilian GPS is not designed to handle this very well. The nav computer can make some estimates. But I question whether the dynamic ranges of the instruments, including GPS, can handle the uncontrolled "aerobatics" situation. I'd also be surprised if the SatCom antenna aiming algorithms can adapt quickly enough to the questionable data to keep the antenna aimed on the satellite.
That's as far as I can take it. This is stuff I know about. It is far enough to suggest strongly, but not conclusively, that the plane was still relatively speaking straight and level at 0214Z, the time of its last transmission. Now, the time gap MIGHT mean it was more or less out of control and the antenna aligned for a few hundred milliseconds, long enough to spit out a burst of trouble reports. But that magic lineup seems to me to be to low a probability to worry OUR minds about. The accident investigators might just to kill even the remote possibilities.
{^_^} Joanne - worked on GPS satellite hardware and software and worked on some GPS receiver software in her years at Rockwell and Magnavox (military) in Torrance.
(It's Kalman not Jalman, you bimbo. {^_-} Typo fixed.)
First, GPS tells you nothing about where you are. It tells you where you were at the time of the last measurement. With an automobile we're speaking of discrepancies that are not worth thinking about. With a high dynamics aircraft (fighter) the difference between where you are and where GPS alone tells you can be more than slightly significant. GPS alone even has difficulty tracking through typical military fighter aircraft moves. With C/A code tracking it's just about worthless. That is why the military has its P-code (and encrypted Y-code).
This lag and inability to track is mitigated to a high degree via software and other inputs, the IMU and IRU for example. Kalman filters can generate enough accuracy to feed back a position estimate to the GPS receiver that the receiver can maintain lock, if not accuracy.
Still, the whole system tells you where you were and where it thinks you might be based on projections not where you are.
GPS is even worse at telling you your speed, although it can do so. It can take where you were at two times and divide by the time to get a velocity vector. If it smooths that over time it can be reasonably accurate.
That brings up "time" as your enemy. The longer you integrate the GPS tracking feedback loops (the lower their bandwidth) the more accurate the data. Noise is the enemy. Fortunately GPS is designed to work WITH jamming efforts. And jamming is just another word for noise. So there is a potentially very large margin for unjammed GPS to be very accurate, especially in relative positions over a short time frame.
Now consider the plane is in heavy turbulence. The filters are prepared to handle this. Civilian aircraft don't do aerobatics. They fly sanely, even in turbulence the flight is fairly sane, it cannot be called aerobatics with spins. rolls, and other rapid motion changes. So far the GPS plus other information sources can give you reasonably good estimates of where you're going, how fast, and where you are. To be sure it's accuracy is fading. But you are within the design parameters for all the instruments and software involved.
Note that I've not said a thing about heading, yaw, or pitch of the plane itself. GPS CAN make an estimate if you have antennas on the nose, tail, and both wing tips. It might even be a good guess using phase tracking tricks. Theoretically it's possible. And with computers these days it may even be practical if calibration tables for cable measured temperature versus delay time is carried and usable. I'd not bet on it.
Now throw the plane into a spiral dive or a flat spin or almost any other controlled or uncontrolled aerobatic movement. Civilian GPS is not designed to handle this very well. The nav computer can make some estimates. But I question whether the dynamic ranges of the instruments, including GPS, can handle the uncontrolled "aerobatics" situation. I'd also be surprised if the SatCom antenna aiming algorithms can adapt quickly enough to the questionable data to keep the antenna aimed on the satellite.
That's as far as I can take it. This is stuff I know about. It is far enough to suggest strongly, but not conclusively, that the plane was still relatively speaking straight and level at 0214Z, the time of its last transmission. Now, the time gap MIGHT mean it was more or less out of control and the antenna aligned for a few hundred milliseconds, long enough to spit out a burst of trouble reports. But that magic lineup seems to me to be to low a probability to worry OUR minds about. The accident investigators might just to kill even the remote possibilities.
{^_^} Joanne - worked on GPS satellite hardware and software and worked on some GPS receiver software in her years at Rockwell and Magnavox (military) in Torrance.
(It's Kalman not Jalman, you bimbo. {^_-} Typo fixed.)
Last edited by JD-EE; 15th Jun 2009 at 23:20.
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I keep on seeing this - can someone explain how an aircraft, supposedly 'breaking up' badly enough to spill passengers, can travel on for 85k?
http://www.asc.gov.tw/author_files/Ballistic.pdf
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The heater controller maybe can't tell when it's being overwhelmed by outside spec icing conditions (or an undetected heater failure or a "design flaw") but there is a system which can detect the consequences - the ADIRU miscompare messages are telling you that the data is beoming unreliable. Since there's not a lot you can do to rectify the situation other than switch to (hopefully functional) alternate sources.
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ClippedCub
All the plane has to do is disperse the bodies over a fraction of a km.
Differential drift rates in the prevailing Westerly currents would take care of the rest of the dispersion.
{^_-}
All the plane has to do is disperse the bodies over a fraction of a km.
Differential drift rates in the prevailing Westerly currents would take care of the rest of the dispersion.
{^_-}
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speculative posts
Are you sure that 'any other professional pilots' would have been flying through that weather, and not around it?
pilots were 'flying through that weather'?
After reading numerous posts by extremely knowledgeable
pilots, meteorologists, engineers, mechanics, and assorted other
professionals, it appears as if it's not been proven that the AF pilots
did not deviate around the worst of the WX.
Many attest that they may have deviated, and communications
to that effect may have been affected by WX, etc. So received
communications or lack thereof aren't evidence that they were flying through that weather.
Also, knowledgeable sources report that, whether they did or
did not deviate, decision making about this may have been
affected by inadequate WX information, including radar, and by the
fact that newly developing convective forces can form and rise rapidly
from the ocean surface and be nearly indetectable.
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Originally Posted by "towhee'
Is it an established fact or only an assumption that the AF
pilots were 'flying through that weather'?
pilots were 'flying through that weather'?
However, I think it is probable because the projections of the plane flying through the MCS explain the 0200Z manual message and fit in well with the projections of Tim Vasquez. Maps suggesting deviation do not do this as well, so I would suggest that the general weight of the evidence suggests that the plane was probably flying through the mesoscale convective system.
This makes it more than an assumption and a bit less than an established fact.
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Application of rudder, instinctual -
what has been said of rudder input in normal flight is very interesting and telling. One should consider the animations the NTSB often publish as part of their public dockets. It would seem that a sudden upset almost always leads to rapid, one would say instinctual, rudder input from the PF. Sometimes this may be justified but from what has been said by pilots here, not often. Perhaps this goes back to training days in small aircraft where more rudder authority is required to escape an upset or establish stable flight in turbulence - the ideas imprinted there could somehow just become part of the airman's natural skills.
This aircraft had already accumulated 18000 hours in 4 years - that's a lot of flying. There are many unknowns about how fatigue accumulates in composite structures. We know in one case that the VS mounting lugs failed laterally, all at once, across many layers of composite material, in AA587. This must have taken the structural engineers somewhat by surprise. These things have not been around long enough to know all their properties under heavy use. One thing is sure, they don't respond well to rapidly changing stress like aluminum does, and they tend to fail collectively and not along easily identifiable cracks. One can point out here the failure of the carbon-carbon reinforced leading edge panels in the Columbia orbiter. The collected engineers gasped in amazement as a piece of foam smashed a 50cm hole in that panel - I don't think anyone expected this collective failure mode where a crack develops and propagates at such speed. One thing that may be important to consider is that these structures come out of fabrication with a lot of frozen-in stress that gets released almost explosively on failure.
-drl
what has been said of rudder input in normal flight is very interesting and telling. One should consider the animations the NTSB often publish as part of their public dockets. It would seem that a sudden upset almost always leads to rapid, one would say instinctual, rudder input from the PF. Sometimes this may be justified but from what has been said by pilots here, not often. Perhaps this goes back to training days in small aircraft where more rudder authority is required to escape an upset or establish stable flight in turbulence - the ideas imprinted there could somehow just become part of the airman's natural skills.
This aircraft had already accumulated 18000 hours in 4 years - that's a lot of flying. There are many unknowns about how fatigue accumulates in composite structures. We know in one case that the VS mounting lugs failed laterally, all at once, across many layers of composite material, in AA587. This must have taken the structural engineers somewhat by surprise. These things have not been around long enough to know all their properties under heavy use. One thing is sure, they don't respond well to rapidly changing stress like aluminum does, and they tend to fail collectively and not along easily identifiable cracks. One can point out here the failure of the carbon-carbon reinforced leading edge panels in the Columbia orbiter. The collected engineers gasped in amazement as a piece of foam smashed a 50cm hole in that panel - I don't think anyone expected this collective failure mode where a crack develops and propagates at such speed. One thing that may be important to consider is that these structures come out of fabrication with a lot of frozen-in stress that gets released almost explosively on failure.
-drl
