AF447 Thread No. 3
HN 39:
It represents the component of velocity along the aircraft longitudinal axis only. I don't know if it is significant.
But intuitively it would seem to indicate the possibility of some air molecules being ingested directly down the pitot opening. Other air molecules maybe not so lucky. The 107 groundspeed is a given.
Intuitively, I've been wrong before.
(BTW, people may be mis reading the previous ILS example. The ILS beams are effectively inertially stabilized. Wind will affect aero AOA on a fixed inertial FPA, if holding a constant pitch attitude, horizontal speed & vertical speed. I understand the conditions portrayed in MM43's graphic. Start postulating winds and see what you get for the same exact geometry.)
It represents the component of velocity along the aircraft longitudinal axis only. I don't know if it is significant.
But intuitively it would seem to indicate the possibility of some air molecules being ingested directly down the pitot opening. Other air molecules maybe not so lucky. The 107 groundspeed is a given.
Intuitively, I've been wrong before.
(BTW, people may be mis reading the previous ILS example. The ILS beams are effectively inertially stabilized. Wind will affect aero AOA on a fixed inertial FPA, if holding a constant pitch attitude, horizontal speed & vertical speed. I understand the conditions portrayed in MM43's graphic. Start postulating winds and see what you get for the same exact geometry.)
Join Date: Jun 2009
Location: I am where I am and that's all where I am.
Posts: 660
Likes: 0
Received 0 Likes
on
0 Posts
t54: "In the info released so far there is no mention of what the PF did after that stall warning caused by his nose down inputs. It's just surmise that he stopped nose down inputs at that point."
You seem to be laboring under a misconception. The nose down simply reduced AoA. The pitot tube subsequently unblocked. That made the airspeed indication valid again and too low for the indicated AoA. That led to the stall warning.
From the end of the 2 h 10 min 05 interval:
Note the return if a valid (appearing) airspeed.
From the 2 h 10 min 51 interval:
You seem to be laboring under a misconception. The nose down simply reduced AoA. The pitot tube subsequently unblocked. That made the airspeed indication valid again and too low for the indicated AoA. That led to the stall warning.
From the end of the 2 h 10 min 05 interval:
The speed displayed on the left side increased sharply to 215 kt (Mach 0.68). The airplane was then at an altitude of about 37,500 ft and the recorded angle of attack was around 4 degrees.
From the 2 h 10 min 51 interval:
the stall warning was triggered again.
Join Date: May 2011
Location: venice, ca
Posts: 61
Likes: 0
Received 0 Likes
on
0 Posts
Where were the pilots sitting?
Pleased end this discussion!
It makes no difference where they were sitting or who they were. All pilots in the cockpit or on the plane were qualified or they wouldn't be there.
The numbers of hours and types of acft flown is immaterial.
When a pilot is released to fly he/she is qualified. Period.
It makes no difference where they were sitting or who they were. All pilots in the cockpit or on the plane were qualified or they wouldn't be there.
The numbers of hours and types of acft flown is immaterial.
When a pilot is released to fly he/she is qualified. Period.
Guest
Posts: n/a
engine-eer
From a predictably solid post by lomapaseo.
"Once the actual failure rate becomes obvious in the historical useage of the system (they iced up more often than expected) then the system interaction with the ability to continue safe flight and landing needs to be examined. From my read so far, that includes the crew actions and their failure rate (to take appropriate action). I really don't know how this was taken into account (presumably it was at least considered)."
From engine-eer
"I am not questioning the current airworthiness, I understand the issue has been addressed. I don't think that the system was airworthy at the time. What I am saying is, if they were known to be junk Airbus had an obligation to have an AD issued to insure they were changed out and they didn't do it until after this crash.
I don't think it had an acronym until after 447 went in. "Unreliable Air Speed, UAS." The term gives me the willies. From the 38 logged incidents, and the asymmetrical "Recoveries" from this challenging and surprising fault, no one was ready to AD these tubes?
There was no mystery, no "Weird Fuel", the problem was patent, and challenging. People don't like surprises, eg, sudden descent, roll, and Pitch changes.
"What was that, Captain?" Oh, that was Unreliable airspeed. "How does one recover from it?". Well, it's a bit different each time, no worries".
Airbus does not write or ennable regulations, that would be the regulator's job.
If Airbus was left to write AD's, well......
From a predictably solid post by lomapaseo.
"Once the actual failure rate becomes obvious in the historical useage of the system (they iced up more often than expected) then the system interaction with the ability to continue safe flight and landing needs to be examined. From my read so far, that includes the crew actions and their failure rate (to take appropriate action). I really don't know how this was taken into account (presumably it was at least considered)."
From engine-eer
"I am not questioning the current airworthiness, I understand the issue has been addressed. I don't think that the system was airworthy at the time. What I am saying is, if they were known to be junk Airbus had an obligation to have an AD issued to insure they were changed out and they didn't do it until after this crash.
I don't think it had an acronym until after 447 went in. "Unreliable Air Speed, UAS." The term gives me the willies. From the 38 logged incidents, and the asymmetrical "Recoveries" from this challenging and surprising fault, no one was ready to AD these tubes?
There was no mystery, no "Weird Fuel", the problem was patent, and challenging. People don't like surprises, eg, sudden descent, roll, and Pitch changes.
"What was that, Captain?" Oh, that was Unreliable airspeed. "How does one recover from it?". Well, it's a bit different each time, no worries".
Airbus does not write or ennable regulations, that would be the regulator's job.
If Airbus was left to write AD's, well......
Join Date: Jul 2009
Location: France - mostly
Age: 84
Posts: 1,682
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by OK465
It represents the component of velocity along the aircraft longitudinal axis only.
bearfoil/ lomapaseo and others
I don't think it had an acronym until after 447 went in. "Unreliable Air Speed, UAS." The term gives me the willies. From the 38 logged incidents, and the asymmetrical "Recoveries" from this challenging and surprising fault, no one was ready to AD these tubes?
( Background: I've bashed around in military jets and the likes of the 747 and the 777 for over 15 k hours and never, ever had pitot icing - so what gives with the A330, is it really that fragile)?
Guest
Posts: n/a
wiggy
After 38 actual episodes, the statistics are in dire need of revamp.
I am not content with the seeming "sureness" of most that Pitot ICE was in play, we'll find out. I think it is likely, but who knows?
you say:
"Devils advocate, historically do we know that the tubes in question (Thales?) were statistically significantly more liable to failure than the pitot tubes that were going to replace them and/or the pitots used on similar designs (e.g.777).
( Background: I've bashed around in military jets and the likes of the 747 and the 777 for over 15 k hours and never, ever had pitot icing - so what gives with the A330, is it really that fragile)?"
After rollbacks by TRENT7's, it took a hull loss and some very lucky people to get the Heat exchangers modded.
I am here to tell you that the "Mystery Fuel" was a propagandistic device.
So, beware of those who want us to stare like automatons at the "Certs".
All the proper people were aware of the UAS episodes, as they were of TRENT Fuel Plumbing issues. It took 228 living breathing souls to sacrifice themselves for the bottom lines of the ones who are guilty of inaction.
I may be the only person on Earth who sees it this way. I couldn't care less.
If not Pitots, then Training. Lack of follow through by Airbus on training syllabus for pilots not up to speed on the vagaries of Automatic Controls in LOC? Automatic controls in Loss of Control? Can we spell Oxymoron?
After 38 actual episodes, the statistics are in dire need of revamp.
I am not content with the seeming "sureness" of most that Pitot ICE was in play, we'll find out. I think it is likely, but who knows?
you say:
"Devils advocate, historically do we know that the tubes in question (Thales?) were statistically significantly more liable to failure than the pitot tubes that were going to replace them and/or the pitots used on similar designs (e.g.777).
( Background: I've bashed around in military jets and the likes of the 747 and the 777 for over 15 k hours and never, ever had pitot icing - so what gives with the A330, is it really that fragile)?"
After rollbacks by TRENT7's, it took a hull loss and some very lucky people to get the Heat exchangers modded.
I am here to tell you that the "Mystery Fuel" was a propagandistic device.
So, beware of those who want us to stare like automatons at the "Certs".
All the proper people were aware of the UAS episodes, as they were of TRENT Fuel Plumbing issues. It took 228 living breathing souls to sacrifice themselves for the bottom lines of the ones who are guilty of inaction.
I may be the only person on Earth who sees it this way. I couldn't care less.
If not Pitots, then Training. Lack of follow through by Airbus on training syllabus for pilots not up to speed on the vagaries of Automatic Controls in LOC? Automatic controls in Loss of Control? Can we spell Oxymoron?
Join Date: Jun 2009
Location: I am where I am and that's all where I am.
Posts: 660
Likes: 0
Received 0 Likes
on
0 Posts
HN39, it helps to view the image in message 1340. The velocity of the plane at an angle of 45 degrees (ignoring wind) is about 151-152 knots. The fuselage is at a 61 degree angle to the flight path. Take the cosine of 61 degrees and multiply it by the velocity and you get something on the order of 73 knots. Now it's easier to entertain the notion the 132 knot velocity component across the inlet to the pitot would have it reading "somewhat" low.
The image in 1172 has a misfeature. It implies you can take the cosine of 61 degrees and multiply it by the horizontal velocity component and get something meaningful. Note that the vertical velocity rotated to the plane's reference gives a rearward velocity that subtracts from what you computed.
It's, of course, all quibbling to show that poor pitot had ample reason to read incorrectly.
The image in 1172 has a misfeature. It implies you can take the cosine of 61 degrees and multiply it by the horizontal velocity component and get something meaningful. Note that the vertical velocity rotated to the plane's reference gives a rearward velocity that subtracts from what you computed.
It's, of course, all quibbling to show that poor pitot had ample reason to read incorrectly.
All the proper people were aware of the UAS episodes, as they were of TRENT Fuel Plumbing issues. It took 228 living breathing souls to sacrifice themselves for the bottom lines of the ones who are guilty of inaction.
I may be the only person on Earth who sees it this way. I couldn't care less
I may be the only person on Earth who sees it this way. I couldn't care less
Join Date: Jun 2009
Location: I am where I am and that's all where I am.
Posts: 660
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by wallybird7
When a pilot is released to fly he/she is qualified. Period.
With most junior engineers they spend some time really learning portions of their trade the college never had time to teach. All junior engineers are not qualified to take on really large systems until they can tackle the smaller tasks with aplomb.
I suspect there is not much difference between engineers fresh out of college with their BS degree and pilots fresh out of pilot training. (Certainly if the 9/11 terrorists could even be accepted to a flight training program an engineering degree with some serious coverage of aviation is not needed.)
I also note that a doctor right out of college isn't ready. He spends time as a resident. Then he continues to gain skill as he ages and indulges in extra training.
If pilots don't learn as they gain experience, I am not sure I want to fly anymore. That would say something terribly frightening about the attitude and intelligence of pilots. Fortunately reading this list make it obvious pilots do gain skills with experience.
Join Date: Jun 2011
Location: UK
Age: 83
Posts: 19
Likes: 0
Received 0 Likes
on
0 Posts
jd ee
I'm talking about when they were on the way down - not the warning at the start of the stall.
The report tells of nose down inputs and (consequent?) stall warnings sounding. Possibly the pitot readings had been invalid due to the large angle of attack - and nose-down validated them and so the stall warning sounded?
t54: "In the info released so far there is no mention of what the PF did after that stall warning caused by his nose down inputs. It's just surmise that he stopped nose down inputs at that point."
You seem to be laboring under a misconception. The nose down simply reduced AoA.
You seem to be laboring under a misconception. The nose down simply reduced AoA.
The report tells of nose down inputs and (consequent?) stall warnings sounding. Possibly the pitot readings had been invalid due to the large angle of attack - and nose-down validated them and so the stall warning sounded?
Join Date: Jun 2009
Location: I am where I am and that's all where I am.
Posts: 660
Likes: 0
Received 0 Likes
on
0 Posts
bearfoil, I have a favorite homily about foolproofing. "No matter how well you foolproof a system God will provide you a better fool." (Some idiot is going to put his hand in the toaster.) Fixing the pitots by getting better pitots is simply going to lead to the discovery of even more obscure means for the pitots to fail transiently or permanently.
So you must presume they are going to fail. Then you look at the next step in the over-all failure chain and see if you can at least partially mitigate it. You recurse as far as you can into this process.
Please don't advocate simply changing the pitot tubes as the grand solution. It is very obvious there were several serious failures in the chain of events that led AF447 with 228 people aboard to a watery grave. ALL of these items should be addressed and mitigated as much as feasible. (And I am sure that mitigation process will include some brutal cost calculations. These companies are in business to make money. We, the people, should demand these calculations be made public - for ALL airlines and aircraft companies. Then we can make our decisions about flying or not, which airline, and how often. I suspect the pilots would like to know their personal risks, too. And with the A330 line it seems that risk is uncommonly low already.)
So you must presume they are going to fail. Then you look at the next step in the over-all failure chain and see if you can at least partially mitigate it. You recurse as far as you can into this process.
Please don't advocate simply changing the pitot tubes as the grand solution. It is very obvious there were several serious failures in the chain of events that led AF447 with 228 people aboard to a watery grave. ALL of these items should be addressed and mitigated as much as feasible. (And I am sure that mitigation process will include some brutal cost calculations. These companies are in business to make money. We, the people, should demand these calculations be made public - for ALL airlines and aircraft companies. Then we can make our decisions about flying or not, which airline, and how often. I suspect the pilots would like to know their personal risks, too. And with the A330 line it seems that risk is uncommonly low already.)
Join Date: Feb 2001
Location: right here inside my head
Age: 65
Posts: 178
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Engine-eer
I don't think that the system was airworthy at the time. What I am saying is, if they were known to be junk Airbus had an obligation to have an AD issued to insure they were changed out and they didn't do it until after this crash.
IF Airbus, and/or, the regulator, and/or THALES knew... that the pitots were not performing to specs... due diligence would require them to cause all the aircraft so equipped, to be declared un-airworthy. ....as that is the definition of airworthiness: "meets the standards".
Last edited by 3holelover; 4th Jun 2011 at 22:59.
Greybeard, #1337
Sounds like a good project for you, SYSENG
Ok, dropped myself right into it there :-), but not enough data to do
it. Someone else mentions later a doc that describes what's available in
the various laws, but not enough info on the conditions or inputs, that
lead to them.
Will keep digging...
Sounds like a good project for you, SYSENG
it. Someone else mentions later a doc that describes what's available in
the various laws, but not enough info on the conditions or inputs, that
lead to them.
Will keep digging...
Join Date: Jun 2009
Location: I am where I am and that's all where I am.
Posts: 660
Likes: 0
Received 0 Likes
on
0 Posts
quoth bearfoil, "After 38 actual episodes, the statistics are in dire need of revamp."
Just what ARE the statistics you cite? The probability of a probe icing incident at altitude is how many per million flights? Is it something to panic about or is it something to fix when a fix appears? Is it going to make flying measurably safer?
Give us the numbers to go with your sense of urgency, please.
Just what ARE the statistics you cite? The probability of a probe icing incident at altitude is how many per million flights? Is it something to panic about or is it something to fix when a fix appears? Is it going to make flying measurably safer?
Give us the numbers to go with your sense of urgency, please.
AVLNative, #1339
That looks pretty good, but still not enough info on how it gets to each law.
Perhaps I should google "Flight Control Logic", or similar
...
That looks pretty good, but still not enough info on how it gets to each law.
Perhaps I should google "Flight Control Logic", or similar
...
Background: I've bashed around in military jets and the likes of the 747 and the 777 for over 15 k hours and never, ever had pitot icing - so what gives with the A330, is it really that fragile
Could it be that this problem has more to do with the way they are installed than with the probes themselves (e.g. typical position on the fuselage)?