AF447 final crew conversation - Thread No. 2
Originally Posted by Turbine D
So I think with proper design parameters, proper mating with the aircraft and proper testing requirements pitot probes from any manufacturer can be designed that work throughout the flight envelope.
Originally Posted by RR NDB
But i love a good design. When possible, why not to have it?
Icing conditions that AF447 encountered a couple of minutes before its destruction are very rare and seldom cause trouble. Being elusive, we can't analyze them as much as we would want. All we know about them that they usually occur near "deep convections" and unlike every other known type of icing, they need the surface they hit to be heated or they won't stick, so they clog heated probes and engine compressors. I am exaggerating here but if we approach the problem narrow-mindedly, there is obvious design solution: cut heat to probes as they pick-up ice. That would make probes resilient to exotic high level ice crystals but would make them more vulnerable to every other icing condition there is and that's a lot of problems created for just one particular solved. In real world, there are no designs without downsides and designing solution for problem one doesn't even know what it is can be successful by pure chance.
Order for replacement of Thales probes was based just on empirical evidence (which is more than enough when dealing with high hazard activities such as aviation) that they are ten times more susceptible to getting blocked by high level ice crystals than rival ones. We have no idea what is in the design of probe or complete installation that makes Goodrich probe ten times less likely to get blocked than Thales but we can be sure that different performance was completely unintended. Also Goodrich probes are not completely immune and we better make sure the pilots know what to do when they lose airspeed information, like keep on flying regardless.
Originally Posted by Paull
I know that prior to AF447 the pitot-icing had already been identified and there were steps in place to change the sensors, but was any action taken to introduce this scenario into sim. flights so that we could assess what proportion of pilots would get it right?
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It is remarkable that aviation culture will wax hysterical only to be followed by a rapid version of "Nothing here, let's move along."
When a passenger packed 777 lands short of the runway with fuel starved engines (starved, not exhausted), we end up with an urban myth of "mysterious fuel characteristics", and a band aid sheet metal workaround.
Here, it seems, we are on the cusp of similar dismissal of anomalous circumstances.
Whistling in the cemetery? "We are going to crash...It cannot be." "Odd Pitots" and crap pilots? Keep whistling.
"It cannot be..."
Oh, yes it can. Merely unusual Pitot behaviour? Definitely. If one believes in real red herrings, and not virtual.
When a passenger packed 777 lands short of the runway with fuel starved engines (starved, not exhausted), we end up with an urban myth of "mysterious fuel characteristics", and a band aid sheet metal workaround.
Here, it seems, we are on the cusp of similar dismissal of anomalous circumstances.
Whistling in the cemetery? "We are going to crash...It cannot be." "Odd Pitots" and crap pilots? Keep whistling.
"It cannot be..."
Oh, yes it can. Merely unusual Pitot behaviour? Definitely. If one believes in real red herrings, and not virtual.
paull;
Re, "1> I know that prior to AF447 the pitot-icing had already been identified and there were steps in place to change the sensors, but was any action taken to introduce this scenario into sim. flights so that we could assess what proportion of pilots would get it right?"
Yes, such training was planned and done as part of AFs recurrent briefings and simulator training curriculae for 2008/2009.
The BEA Second Interim Report, Section 1.17 Information on Organisations and Management, provides specific information on this and the previous section, 1.16 Tests and Research discusses the thirteen previous UAS events which had sufficient data such that adequate studies could be undertaken of the phenomenon.
Oddly, of the 36 UAS Events listed in Appendix 7 of this Report which occurred to the A330 up to the day of the accident and during the recurrent training period, only two were not in cruise* yet the UAS script was for the right-after-takeoff phase which of course is the most critical phase of flight.
The briefing notes for the exercise indicate that if the ADRs are not rejected and the FCPCs and FCSCs continue to use the incorrect information, the crew will have to:
" Trigger the emergency manoeuvre(15) if they consider control of the flight
is dangerously affected (initial climb, go-around, etc.);
" Trigger the Flight QRH procedure with UAS / ADR check if the trajectory
has been stabilised and flight is under control." **
*one event was on descent (FL290) and the other event was on approach.
** p54, BEA Second Interim Report, English version
Re, "1> I know that prior to AF447 the pitot-icing had already been identified and there were steps in place to change the sensors, but was any action taken to introduce this scenario into sim. flights so that we could assess what proportion of pilots would get it right?"
Yes, such training was planned and done as part of AFs recurrent briefings and simulator training curriculae for 2008/2009.
The BEA Second Interim Report, Section 1.17 Information on Organisations and Management, provides specific information on this and the previous section, 1.16 Tests and Research discusses the thirteen previous UAS events which had sufficient data such that adequate studies could be undertaken of the phenomenon.
Oddly, of the 36 UAS Events listed in Appendix 7 of this Report which occurred to the A330 up to the day of the accident and during the recurrent training period, only two were not in cruise* yet the UAS script was for the right-after-takeoff phase which of course is the most critical phase of flight.
The briefing notes for the exercise indicate that if the ADRs are not rejected and the FCPCs and FCSCs continue to use the incorrect information, the crew will have to:
" Trigger the emergency manoeuvre(15) if they consider control of the flight
is dangerously affected (initial climb, go-around, etc.);
" Trigger the Flight QRH procedure with UAS / ADR check if the trajectory
has been stabilised and flight is under control." **
*one event was on descent (FL290) and the other event was on approach.
** p54, BEA Second Interim Report, English version
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PJ2
A quick question. You refer to "UAS" procedures in the literature from Airbus. I may be mistaken, but I believe the term "UAS" was coined here at PPRUNE, post AF447. Prior, the nomenclature was not specific, generally referencing other than "Unreliable Air Speed" (UAS). ??
A quick question. You refer to "UAS" procedures in the literature from Airbus. I may be mistaken, but I believe the term "UAS" was coined here at PPRUNE, post AF447. Prior, the nomenclature was not specific, generally referencing other than "Unreliable Air Speed" (UAS). ??
Lyman;
The term "UAS" was used in the BEA Second Interim Report but not the first. In researching the eight or so AF447 threads the term was used first by Will Fraser on the 23rd of September 2009 and thence by bearfoil on the 24th of December, same year. Whether the BEA adopted the abbreviation or not can't be known. I know some from the BEA have monitored the threads in the past.
The evolution of the UAS drill and QRH checklist is discussed in the BEA Reports. I first saw it around 1998 and it showed up in the FCTM around 2003/05. At that time it was clarified when to apply the memorized items and when to not do the memorized items and go straight to the QRH procedures which prescribed setting pitch and power according to the QRH tables. Typically such circumstances were cruise flight; the memorized items were intended for low-level, during/after-takeoff circumstances where immediate information was required due to the immediate high risk to the flight, (as per Birgenair & Aeroperu accidents). The aircraft is not in immediate danger with a loss of airspeed information in cruise.
The term "UAS" was used in the BEA Second Interim Report but not the first. In researching the eight or so AF447 threads the term was used first by Will Fraser on the 23rd of September 2009 and thence by bearfoil on the 24th of December, same year. Whether the BEA adopted the abbreviation or not can't be known. I know some from the BEA have monitored the threads in the past.
The evolution of the UAS drill and QRH checklist is discussed in the BEA Reports. I first saw it around 1998 and it showed up in the FCTM around 2003/05. At that time it was clarified when to apply the memorized items and when to not do the memorized items and go straight to the QRH procedures which prescribed setting pitch and power according to the QRH tables. Typically such circumstances were cruise flight; the memorized items were intended for low-level, during/after-takeoff circumstances where immediate information was required due to the immediate high risk to the flight, (as per Birgenair & Aeroperu accidents). The aircraft is not in immediate danger with a loss of airspeed information in cruise.
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Unreliable airspeed has been called unreliable airspeed for many years. It is not a new term, neither is the abbreviation.
I recall checklists called "unreliable airspeed" from at least the early 90's, possibly the late 80's, and expanded checklists and explanatory material with the heading "speed control with unreliable airspeed".
The expanded checklists and explanatory material were more detailed in the A300 days than for later models, particularly concerning the various failure modes and effect on indications and systems.
I recall checklists called "unreliable airspeed" from at least the early 90's, possibly the late 80's, and expanded checklists and explanatory material with the heading "speed control with unreliable airspeed".
The expanded checklists and explanatory material were more detailed in the A300 days than for later models, particularly concerning the various failure modes and effect on indications and systems.
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PJ2, Hamburt Spinkleman.
Thank you both for your input. The reason I suggest that "UAS" is a "new" acronym has to do not with aviating, but with marketing. At the time, in 2009, it occurred to me that "Unreliable" is not a term to be found on any documents emanating from the community, manufacturer, Line, Pilot's, etc. Not only does it conjure up "risk", it could be conflated to mean, erm...."Unreiiable". It could also have a negative effect in "product liability".
So Hamburt, I am curious if you have copies of these "checklists from years ago".
The reason I coined the term was its self-explanatory nature, and its 'honesty' in an industry that can at times be over obsessed with "marketing".
I meant it without malice, but was attracted to its inception merely because it was....descriptive.
me
Especially at low level, PJ2, would it not also be important to include "Point" after Pitch/Power? Heading after T/O could be construed as important as the first two, CFIT?
Thank you both for your input. The reason I suggest that "UAS" is a "new" acronym has to do not with aviating, but with marketing. At the time, in 2009, it occurred to me that "Unreliable" is not a term to be found on any documents emanating from the community, manufacturer, Line, Pilot's, etc. Not only does it conjure up "risk", it could be conflated to mean, erm...."Unreiiable". It could also have a negative effect in "product liability".
So Hamburt, I am curious if you have copies of these "checklists from years ago".
The reason I coined the term was its self-explanatory nature, and its 'honesty' in an industry that can at times be over obsessed with "marketing".
I meant it without malice, but was attracted to its inception merely because it was....descriptive.
me
Especially at low level, PJ2, would it not also be important to include "Point" after Pitch/Power? Heading after T/O could be construed as important as the first two, CFIT?
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PJ2, Lyman, Hambert Sprinkleman,
I did a little research on UAS and came up with some interesting results. It would appear the accident investigation and reporting agencies tend to use the term "Erroneous Airspeed Indications". This is true in the Aeroperu and Birgenair reports as well as one issued by the US NTSB on an incident over Kansas City involving a B-717 which did not crash. These reports were issued prior to or around the time of AF447.
However, there is an FAA document that was issued to discuss this phenomenon:
I would say, in terms of the English language, errorneous airspeed meaning is pretty clear, the airspeed was wrong. Unreliable airspeed is a little "softer" as its meaning is "don't count on it to be accurate or uncertain of accuracy".
Lyman, In a court of law, I suspect the terminology of either poses a problem for the defendant.
I did a little research on UAS and came up with some interesting results. It would appear the accident investigation and reporting agencies tend to use the term "Erroneous Airspeed Indications". This is true in the Aeroperu and Birgenair reports as well as one issued by the US NTSB on an incident over Kansas City involving a B-717 which did not crash. These reports were issued prior to or around the time of AF447.
However, there is an FAA document that was issued to discuss this phenomenon:
Date: 6/26/75
Initiated By: AFS-223
AC No.: 91- 43
Subject: UNRELIABLE AIRSPEED INDICATIONS
Initiated By: AFS-223
AC No.: 91- 43
Subject: UNRELIABLE AIRSPEED INDICATIONS
Lyman, In a court of law, I suspect the terminology of either poses a problem for the defendant.
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Unreliable Airspeed
As QRH section 2.21 is titled "UNRELIABLE SPEED INDICATION/ADR CHECK PROCEDURE", it looks like the "air" has been added at some point of time to the "speed".
But does it change something to the AF447 story (except adding almost one page to this thread
) ?
But does it change something to the AF447 story (except adding almost one page to this thread
) ?
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From the BEA July 2011 report
1.17.4.3 Terminologie du constructeur (AIRBUS)
Memory item the following procedures are to be applied without referring to paper: immediate actions of UNRELIABLE SPEED INDICATION/ADR CHECK PROC"Air France a traduit le titre de cette procédure par « Vol avec IAS douteuse »."
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Like llagonne66, I don't know what the point is, but.
"Unreliable Air Speed" is the term Airbus has been using for decades in Flight Manuals, FCOM's, QRH's and other material.
Boeing, by the way, use the same term. Or actually they use both "Airspeed Unreliable" and "Unreliable Airspeed".
"Unreliable Air Speed" is the term Airbus has been using for decades in Flight Manuals, FCOM's, QRH's and other material.
Boeing, by the way, use the same term. Or actually they use both "Airspeed Unreliable" and "Unreliable Airspeed".
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Hamburt Spinkleman
The point is a small one. I got tired of writing out the various phrases used to identify a problem that was getting much attention. In creating (?) the acronym, UAS, I found a way to simplify and shorten the nomenclature. If it was used before, fine, but I believe the industry was calling the problem different names, and spelling them out, as if it was this ill-defined, and rare anomaly. I thought it deserved its own acronym. That BEA started to use it also meant I may have been correct in codifying it. It also meant that BEA might have been reading PPRuNe, which means PPRuNe has some standing in the discussion/investigation. So Hamburt, it means whatever it means to you, nothing more. At all.
The point is a small one. I got tired of writing out the various phrases used to identify a problem that was getting much attention. In creating (?) the acronym, UAS, I found a way to simplify and shorten the nomenclature. If it was used before, fine, but I believe the industry was calling the problem different names, and spelling them out, as if it was this ill-defined, and rare anomaly. I thought it deserved its own acronym. That BEA started to use it also meant I may have been correct in codifying it. It also meant that BEA might have been reading PPRuNe, which means PPRuNe has some standing in the discussion/investigation. So Hamburt, it means whatever it means to you, nothing more. At all.
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Total pressure tube heater:
Heater is 2 elements of resistance wire, ~34 Ohm @ 20°C.
Uses full 115VACrms wave in flight and half wave (~81Vac) on ground.
PHC warnings levels <0.9A and >6A in flight; <0.4A and >4A on ground.
Uses full 115VACrms wave in flight and half wave (~81Vac) on ground.
PHC warnings levels <0.9A and >6A in flight; <0.4A and >4A on ground.
Last edited by A33Zab; 8th Mar 2012 at 11:35.
