AF 447 Search to resume
Join Date: May 2010
Location: Le Shed on the Tropic of Capricorn
Age: 62
Posts: 22
Likes: 0
Received 0 Likes
on
0 Posts
@sensor. To make pitots independent of air density in the 0.3<M<1 range, the formula used is (with a lots more brackets in both forumula) M=sqrt((2/G-1)(Pstag/Pstatic)^(G-1/G)-1)). This then takes the Pstag and Pstatic and calculates M via gamma G. Hence why my point that a variation in the G assumption leads to incorrect calculations. (But measured Pstatic is wrong due to sensor location so this value is then recalibrated from the measured M etc etc.) If TAT and SAT are measured (rather than SAT calculated from TAT using M from pitot calculation) then this can be done via M=sqrt((TAT/SAT-1)(2/G-1)). Again using G rather than having to know density. Assuming Gamma is constant takes away the density problem. But is this assumption valid in a Cb
Join Date: Jul 2009
Location: Not far from a big Lake
Age: 81
Posts: 1,454
Likes: 0
Received 0 Likes
on
0 Posts
JD-EE
A bit of an update on the concept of a bogus Vmo/Mmo pitchup causing a stall.
1.A bit of study on the Vmo/Mmo protection mode indicates that activation of this protection will disengage autopilot as it pitches the aircraft up. This means, that the soonest such an event could have occurred would be at the very beginning of the ACARS sequence, thus perhaps explaining this message at the very beginning:
2:10:10WRN/WN0906010210 221002006AUTO FLT AP OFF
Very shortly after this message we have:
2:10:23WRN/WN0906010210 279100506F/CTL ALTN LAW
So if AF447 encountered such a pitchup, it would not have been very long in duration before the aircraft was no longer in normal law so the duration of a common mode bogus overspeed indication would not have had to stay in sync for very long either before dropping out of sync and causing ALT2 law. Perhaps 10 seconds max.
2. The 2nd BEA report, page 46 describes the airspeed elaboration function used by the PRIMS as follows:
"Like the FMGECs, the PRIMs consolidate the parameters that they use by
means of monitoring mechanisms. Concerning the airspeed, it is the voted
value that is used. In normal operation, this is the median value. When one
of the three speeds deviates too much from the other two, it is automatically
rejected by the PRIMs and the polled value then becomes the average of the
two remaining values. But if the difference between these two remaining
values becomes too great the PRIMs reject them and the control law switches
to alternate 2. Furthermore, another monitoring procedure is applied to the
value of the voted airspeed and triggers switching to alternate 2 law when it
falls by more than 30 kt in one second."
Note also from the second BEA report regarding other aircraft incidents:
In seven cases, the autopilot was reconnected during the event. In two of
them, the re-connection occurred when the two speeds were consistent
with each other but were erroneous; My personal conclusion: Bogus airspeeds can be encountered for significant periods (minutes) on an Airbus.
The question now is, how long would it take for such a protection caused pullup to put AF447 on a trajectory for a certain stall.? How long does it take for an Airbus to switch flight control laws?
A bit of an update on the concept of a bogus Vmo/Mmo pitchup causing a stall.
1.A bit of study on the Vmo/Mmo protection mode indicates that activation of this protection will disengage autopilot as it pitches the aircraft up. This means, that the soonest such an event could have occurred would be at the very beginning of the ACARS sequence, thus perhaps explaining this message at the very beginning:
2:10:10WRN/WN0906010210 221002006AUTO FLT AP OFF
Very shortly after this message we have:
2:10:23WRN/WN0906010210 279100506F/CTL ALTN LAW
So if AF447 encountered such a pitchup, it would not have been very long in duration before the aircraft was no longer in normal law so the duration of a common mode bogus overspeed indication would not have had to stay in sync for very long either before dropping out of sync and causing ALT2 law. Perhaps 10 seconds max.
2. The 2nd BEA report, page 46 describes the airspeed elaboration function used by the PRIMS as follows:
"Like the FMGECs, the PRIMs consolidate the parameters that they use by
means of monitoring mechanisms. Concerning the airspeed, it is the voted
value that is used. In normal operation, this is the median value. When one
of the three speeds deviates too much from the other two, it is automatically
rejected by the PRIMs and the polled value then becomes the average of the
two remaining values. But if the difference between these two remaining
values becomes too great the PRIMs reject them and the control law switches
to alternate 2. Furthermore, another monitoring procedure is applied to the
value of the voted airspeed and triggers switching to alternate 2 law when it
falls by more than 30 kt in one second."
Note also from the second BEA report regarding other aircraft incidents:
In seven cases, the autopilot was reconnected during the event. In two of
them, the re-connection occurred when the two speeds were consistent
with each other but were erroneous; My personal conclusion: Bogus airspeeds can be encountered for significant periods (minutes) on an Airbus.
The question now is, how long would it take for such a protection caused pullup to put AF447 on a trajectory for a certain stall.? How long does it take for an Airbus to switch flight control laws?
Join Date: Jul 2009
Location: France - mostly
Age: 84
Posts: 1,682
Likes: 0
Received 0 Likes
on
0 Posts
Gamma
Originally Posted by FluidFlow
fig 62(a) This graph too is for normal humidity but you can see the trend of decreasing G with added moisture ('saturated air' in this case).
I'm not sure I understand the issue you're raising. Air is (nearly) saturated in all clouds, so what's special about this one? If you're thinking of liquid or solid water, is there any data on that?
Secondly, the graph you're referring to shows 0,4% change of gamma for saturated air. Let's consider FL350, M=0,8 and gamma changes rapidly from 1.4 to 1.33 (5%). A simple calculation shows that pitot pressure would increase by 0,3% and the indicated Mach would increase from 0,8 to 0,8032.
regards,
HN39
Join Date: Jul 2009
Location: France - mostly
Age: 84
Posts: 1,682
Likes: 0
Received 0 Likes
on
0 Posts
HiSpdProt pull-up
Originally Posted by Machinbird
The question now is, how long would it take for such a protection caused pullup to put AF447 on a trajectory for a certain stall?
To put some numbers your question, the high speed protection will apply a nose-up order up to 1.75 g (FCOM). At FL350, M=0.8, ISA+13 the AoA at 1g is about 2,9 degrees and buffet onset loadfactor is about 1.65 at AoA=5,6 degrees (assuming linearised QF72 AoA), which could be attained in about 1 sec. 1.75 g would take the airplane to FL384, M=0.66 (1g buffet onset at that FL) in about 12 sec.
regards,
HN39
Originally Posted by fluid flow
Assuming Gamma is constant takes away the density problem. But is this assumption valid in a Cb
Originally Posted by hazelnuts39
Secondly, the graph you're referring to shows 0,4% change of gamma for saturated air. Let's consider FL350, M=0,8 and gamma changes rapidly from 1.4 to 1.33 (5%). A simple calculation shows that pitot pressure would increase by 0,3% and the indicated Mach would increase from 0,8 to 0,8032.
Do I read you clearly?
Join Date: Jul 2009
Location: Not far from a big Lake
Age: 81
Posts: 1,454
Likes: 0
Received 0 Likes
on
0 Posts
HN39
To put some numbers your question, the high speed protection will apply a nose-up order up to 1.75 g (FCOM). At FL350, M=0.8, ISA+13 the AoA at 1g is about 2,9 degrees and buffet onset loadfactor is about 1.65 at AoA=5,6 degrees (assuming linearised QF72 AoA), which could be attained in about 1 sec. 1.75 g would take the airplane to FL384, M=0.66 (1g buffet onset at that FL) in about 12 sec
To put some numbers your question, the high speed protection will apply a nose-up order up to 1.75 g (FCOM). At FL350, M=0.8, ISA+13 the AoA at 1g is about 2,9 degrees and buffet onset loadfactor is about 1.65 at AoA=5,6 degrees (assuming linearised QF72 AoA), which could be attained in about 1 sec. 1.75 g would take the airplane to FL384, M=0.66 (1g buffet onset at that FL) in about 12 sec
Thanks for that HN39. I assume at that point, there would be a residual nose up pitch angle of about 20 degrees or so. It would seem likely that the pitch angle protection would set an upper limit in any case.
Join Date: Jul 2009
Location: France - mostly
Age: 84
Posts: 1,682
Likes: 0
Received 0 Likes
on
0 Posts
Machinbird;
that's roughly confirmed. Calculated flight path angle 20 degrees, AoA at 1g 7,8 degrees. Per FCOM pitch angle protection steps in early enough to avoid exceeding 30 degrees.
Lonewolf;
Yes, that's what I'm inclined to think.
that's roughly confirmed. Calculated flight path angle 20 degrees, AoA at 1g 7,8 degrees. Per FCOM pitch angle protection steps in early enough to avoid exceeding 30 degrees.
Lonewolf;
Yes, that's what I'm inclined to think.
Last edited by HazelNuts39; 29th Jun 2010 at 14:53.
Join Date: Jan 2002
Location: USA
Posts: 286
Likes: 0
Received 0 Likes
on
0 Posts
messages may have been generated quasi simultaneously.
As an aside, I attended a BMW presentation over the week end, and one of the tech reps briefly touched on the protocol of fault software. As an example, depending upon how the software is bundled will make a difference in how faults are presented. Often, a component fault will not be valid if another component with a higher hierachy suffers a simular failure, there by creating a dazy chain. Result, not all problems can be tracked down by following the fault tree. Now, don't ask me any questions, I just mentioned what I heard, and am not suggesting this is the case with AF447.
Join Date: Jan 2005
Location: W of 30W
Posts: 1,916
Likes: 0
Received 0 Likes
on
0 Posts
Machinbird,
To me, if the AP disconnect is the consequence of the overspeed protection, alongside the AUTO FLT AP OFF WRN ACARS MSG, we should have got an OVERSPEED WRN ACARS MSG as well.
A bit of study on the Vmo/Mmo protection mode indicates that activation of this protection will disengage autopilot as it pitches the aircraft up. This means, that the soonest such an event could have occurred would be at the very beginning of the ACARS sequence, thus perhaps explaining this message at the very beginning:
2:10:10WRN/WN0906010210 221002006AUTO FLT AP OFF
2:10:10WRN/WN0906010210 221002006AUTO FLT AP OFF
Join Date: Jun 2009
Location: 6m below sea-level
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
deep sea search
auv-ee
"The typical ranges used are about 300-500m either side of track, and the achievable resolution allows detection of an object about the size of a 55 gallon oil drum."
"That puts the range of a l@ser scanner at a maximum of 6*50=300m, but more typically 4*25 = 100m. That does not compete well with sonar for a wide area search for large objects that are likely sitting proud on the seafloor."
The AUV in use seems to be capable of carrying at least another custom-device besides the side-scan sonar. Green/Blue l@ser could add just that additional peace of information, if detected, which could be overlooked with a side-scan sonar. Range is less, half maybe, but to increase the chance of finding, is what it's all about. Not to choose between the 2, but to add l@ser as another opportunity.
"The typical ranges used are about 300-500m either side of track, and the achievable resolution allows detection of an object about the size of a 55 gallon oil drum."
"That puts the range of a l@ser scanner at a maximum of 6*50=300m, but more typically 4*25 = 100m. That does not compete well with sonar for a wide area search for large objects that are likely sitting proud on the seafloor."
The AUV in use seems to be capable of carrying at least another custom-device besides the side-scan sonar. Green/Blue l@ser could add just that additional peace of information, if detected, which could be overlooked with a side-scan sonar. Range is less, half maybe, but to increase the chance of finding, is what it's all about. Not to choose between the 2, but to add l@ser as another opportunity.
Join Date: May 2010
Location: MA, USA
Posts: 126
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Peter-1959
The AUV in use seems to be capable of carrying at least another custom-device besides the side-scan sonar. Green/Blue laser could add just that additional piece of information, if detected, which could be overlooked with a side-scan sonar. Range is less, half maybe, but to increase the chance of finding, is what it's all about. Not to choose between the 2, but to add laser as another opportunity.
In any case, I don't think that both a laser imager and side-scan can be used effectively at the same time. Side scan works best when the vehicle is flown at an altitude of 10% of range (a lot of the information is revealed by the shadows), so for 300-500m side scan range the altitude should be 30-50m. For the laser scanner, you would want to fly at an altitude more nearly equal to range so 100-200m if that is the imaging range of the scanner.
Join Date: Jul 2009
Location: Not far from a big Lake
Age: 81
Posts: 1,454
Likes: 0
Received 0 Likes
on
0 Posts
some messages concerning the aircraft’s configuration such as stall or overspeed warnings are not recorded
I wonder what BEA used to exclude such a pitch up scenario in the process of setting the search area? To me, being left 20 degrees nose up at FL384, M 0.66, at night, with no visible horizon and on the outskirts of a big cell, with no valid airspeed, in a fly by wire aircraft that has just shifted to Alt2 Law seems a bit hairy.
Any delay in pushing the nose down would almost certainly result in a stall, particularly without AOA indications to see how the wing is flying. (Just had to put in a plug for AOA indicators
). If AF447 promptly entered a stall, it might flop around a bit initially but as long as the stall remained, it would likely cause further deceleration until the AOA was quite high and would then result in a stable attitude pretty much along the lines of the impact attitude described by BEA. The flight path over the ground would likely describe an inward spiral starting from an initial circle of no more than 10NM diameter and would be fairly close to the LKP.
It seems that there may well be valid potential to searching the "donut hole" in the last search pattern.
Join Date: May 2010
Location: Le Shed on the Tropic of Capricorn
Age: 62
Posts: 22
Likes: 0
Received 0 Likes
on
0 Posts
Gamma variation
@HN39 et al. Sorry for delay in returning to an internet connection.
As a mere calculation exercise if we take a 5% variation in G from 1.4 to 1.33 as per your post (#1642) and leave Pstag/Pstatic the same in M=sqrt((2/(G-1)){(Pstag/Pstatic)^([G-1]/G)}) at 0.8, from the pitot, then if we assume SAT=-42C (231K) for this exercise, taking M=0.8 we get a TAT of -12.4C for G=1.4 and -17.6C for G=1.33 ie the calcs show a sudden 5 deg change if we assume all other parameters remained constant from M=sqrt[{(Tt/Ts)-1}{2/(G-1)}]. (The other air parameters wont remain constant but I am merely showing how measuring data from one G value atmosphere and calculating others using a different G gives incompatible results.)
For some reason my formulas didnt want to paste from my MathCad program, so in case I have missed some brackets see Aircraft Temperature Measurement Page
My point is that with a change in G there become changes in other parameters that change if the ADU calculates them using a different G than that of the outside atmosphere and the changes do not appear to be insignificant from a cross-checking perspective. Hence my concern is 'error checking' flagging issues that confuse HAL.
I was assuming there would be areas in the Cb that were above saturated as the humid tropical air provides the energy source to power the storm. My reference to the dry and saturated graphs were to show that G decreases with the addition of H2O not to suggest we were operating in this range. I was suggesting AF447 entered an 'abnormal' atmosphere.
There is a section in Atmosphere Ocean Dynamics Volume 30 International Geophysics by Adrian E Gill pg 44 equation 3.3.5 (via google books??) that shows this Gamma change.
There is some research on Effective ice particle densities for cold anvil cirrus CRYSTAL-FACE Publications. See Heymsfield and Jensen half way down the list.
Trust this shows why I raised the issue.
kind regards. Ian
As a mere calculation exercise if we take a 5% variation in G from 1.4 to 1.33 as per your post (#1642) and leave Pstag/Pstatic the same in M=sqrt((2/(G-1)){(Pstag/Pstatic)^([G-1]/G)}) at 0.8, from the pitot, then if we assume SAT=-42C (231K) for this exercise, taking M=0.8 we get a TAT of -12.4C for G=1.4 and -17.6C for G=1.33 ie the calcs show a sudden 5 deg change if we assume all other parameters remained constant from M=sqrt[{(Tt/Ts)-1}{2/(G-1)}]. (The other air parameters wont remain constant but I am merely showing how measuring data from one G value atmosphere and calculating others using a different G gives incompatible results.)
For some reason my formulas didnt want to paste from my MathCad program, so in case I have missed some brackets see Aircraft Temperature Measurement Page
My point is that with a change in G there become changes in other parameters that change if the ADU calculates them using a different G than that of the outside atmosphere and the changes do not appear to be insignificant from a cross-checking perspective. Hence my concern is 'error checking' flagging issues that confuse HAL.
I was assuming there would be areas in the Cb that were above saturated as the humid tropical air provides the energy source to power the storm. My reference to the dry and saturated graphs were to show that G decreases with the addition of H2O not to suggest we were operating in this range. I was suggesting AF447 entered an 'abnormal' atmosphere.
There is a section in Atmosphere Ocean Dynamics Volume 30 International Geophysics by Adrian E Gill pg 44 equation 3.3.5 (via google books??) that shows this Gamma change.
There is some research on Effective ice particle densities for cold anvil cirrus CRYSTAL-FACE Publications. See Heymsfield and Jensen half way down the list.
Trust this shows why I raised the issue.
kind regards. Ian
Join Date: Jun 2009
Location: NNW of Antipodes
Age: 81
Posts: 1,330
Received 0 Likes
on
0 Posts
ACARS sequencing
Originally posted by HN39 ...
The first nine messages follow each other without interruption at an average rate of 6,25 sec/msg, which seems to be the maximum rate allowed by the communication protocol. In other words, these messages may have been generated quasi simultaneously.
The first nine messages follow each other without interruption at an average rate of 6,25 sec/msg, which seems to be the maximum rate allowed by the communication protocol. In other words, these messages may have been generated quasi simultaneously.
The AUTO FLT REAC W/S DET FAULT warning seems to be be a little out of place; by that I mean that the windshear predictive function is only available below 1500 feet and windshear below 1300 feet. This maybe a case where warnings regarding its availability should have been inhibited in this phase of the flight. However, it helps with our understanding of the possible causes of this upset.
Three maintenance warnings were not displayed to the crew, and it would appear by the gap between -
2:11:00 WRN/WN0906010210 228300106FLAG ON CAPT PFD FD
2:11:15 WRN/WN0906010210 228301106FLAG ON F/O PFD FD
that there was nothing else sequenced during that period, and that the PF was seated in the left-hand seat - assuming he went looking for the "bird" first.
The ACARS list has been updated to indicate (using background colors) the relative importance of the various Warnings and Failures. FLAG warnings are in pastel purple except for the warnings that the crew generated when they went looking for the AoA "bird", which are in pastel green. NAV warnings are in pastel orange, F/CTL warnings are in yellow and AUTO FLT warnings are in cyan.
MAINTENANCE messages have a dark grey/gray background and FLR messages are displayed as dark red, while the AUTO FLT REAC W/S DET FAULT is in pink. The final ADVISORY message has a white background.
Clicking on a line will cause the Time of Receipt to be highlighted in yellow. Clicking again will revert the line to normal.
mm43
Join Date: Sep 2000
Location: England
Posts: 303
Likes: 0
Received 0 Likes
on
0 Posts
The Logic for a Vmo/Mmo Protective Pitch-up???
Notwithstanding what Machinbird says at post 1641 above and the other quoted remarks below, I have a problem with identifying the circumstances leading to (and the possibility) of an initial Vmo/Mmo protective pitch-up (see argument below the quotes).
Confiture said:
Hazelnuts said:
Machinbirs said:
.
I'm not really following why the Airbus Flt Ctrl pitch-up protection against an imminent Vmo/Mm0 encounter should kick in if the airspeeds being fed to the ADIRS were:
.
...a. Initially in agreement, albeit wrong due to pitot icing - either internally (supercooled ice-crystal build-up) or externally (BBC's pure water icing theory)
.
...b. Latterly being maintained at the selected cruise speed by autothrust (even though the actual airspeed/mach was much higher).
...
..c. Ultimately mismatching the three pitot-derived speeds sufficiently to cause a disagree and the Autopilot to disconnect.
.
I imagine that the flt ctrl protections are keyed by CAS and Mach, and if these weren't uniformly trending dangerously high (due to pitot blockage), what is there to cause the protections to cook off and intervene - by allowing the AP to pitch the nose up then disconnect? Isn't it more likely (per posts 1208 and 1471 and 1476 and 1489 ) that the aircraft accelerated into a nose-down pitch (i.e. mach tuck) because there was nothing (no high CAS or mach) detected to trigger any such protection. If the flight crew responded to a pitch-down by misinterpreting it as a stall and went TOGA/stick fwd, then that would have embedded the A330 in compressibility (with all its nasty L.o.C. follow-ons).
.
The above debate disregards where the THS may have been trimmed to and what instantaneous pitch effect it may have had upon the aircraft at autopilot disconnect. That's another ball-of-wax that's unclear to me. i.e. where's the THS being trimmed to when the datum indicated airspeed is artificially low - and how much deflected elevator can the autopilot's baro-hold handle in order to maintain the dialled in flight level (before disconnecting)?
.
Confiture said:
A bit of study on the Vmo/Mmo protection mode indicates that activation of this protection will disengage autopilot as it pitches the aircraft up. This means, that the soonest such an event could have occurred would be at the very beginning of the ACARS sequence, thus perhaps explaining this message at the very beginning:
2:10:10WRN/WN0906010210 221002006AUTO FLT AP OFF
2:10:10WRN/WN0906010210 221002006AUTO FLT AP OFF
1st interim report, p.47: "some messages concerning the aircraft’s configuration such as stall or overspeed warnings are not recorded."
Thank you for pointing out that BEA quote HN39. If such warnings existed, that would have invalidated a Vmo/Mmo protection pitch-up scenario. I was having trouble finding an ACARS reference on the subject. The only other thing that might contra-indicate such a pitch up is the rudder limiter position which probably would have locked at the polled airspeed indication existing when Normal Law was abandoned.
I wonder what BEA used to exclude such a pitch up scenario in the process of setting the search area? To me, being left 20 degrees nose up at FL384, M 0.66, at night, with no visible horizon and on the outskirts of a big cell, with no valid airspeed, in a fly by wire aircraft that has just shifted to Alt2 Law seems a bit hairy. Any delay in pushing the nose down would almost certainly result in a stall, particularly without AOA indications to see how the wing is flying. (Just had to put in a plug for AOA indicators).
If AF447 promptly entered a stall, it might flop around a bit initially but as long as the stall remained, it would likely cause further deceleration until the AOA was quite high and would then result in a stable attitude pretty much along the lines of the impact attitude described by BEA. The flight path over the ground would likely describe an inward spiral starting from an initial circle of no more than 10NM diameter and would be fairly close to the LKP.
It seems that there may well be valid potential to searching the "donut hole" in the last search pattern.
I wonder what BEA used to exclude such a pitch up scenario in the process of setting the search area? To me, being left 20 degrees nose up at FL384, M 0.66, at night, with no visible horizon and on the outskirts of a big cell, with no valid airspeed, in a fly by wire aircraft that has just shifted to Alt2 Law seems a bit hairy. Any delay in pushing the nose down would almost certainly result in a stall, particularly without AOA indications to see how the wing is flying. (Just had to put in a plug for AOA indicators).
If AF447 promptly entered a stall, it might flop around a bit initially but as long as the stall remained, it would likely cause further deceleration until the AOA was quite high and would then result in a stable attitude pretty much along the lines of the impact attitude described by BEA. The flight path over the ground would likely describe an inward spiral starting from an initial circle of no more than 10NM diameter and would be fairly close to the LKP.
It seems that there may well be valid potential to searching the "donut hole" in the last search pattern.
I'm not really following why the Airbus Flt Ctrl pitch-up protection against an imminent Vmo/Mm0 encounter should kick in if the airspeeds being fed to the ADIRS were:
.
...a. Initially in agreement, albeit wrong due to pitot icing - either internally (supercooled ice-crystal build-up) or externally (BBC's pure water icing theory)
.
...b. Latterly being maintained at the selected cruise speed by autothrust (even though the actual airspeed/mach was much higher).
...
..c. Ultimately mismatching the three pitot-derived speeds sufficiently to cause a disagree and the Autopilot to disconnect.
.
I imagine that the flt ctrl protections are keyed by CAS and Mach, and if these weren't uniformly trending dangerously high (due to pitot blockage), what is there to cause the protections to cook off and intervene - by allowing the AP to pitch the nose up then disconnect? Isn't it more likely (per posts 1208 and 1471 and 1476 and 1489 ) that the aircraft accelerated into a nose-down pitch (i.e. mach tuck) because there was nothing (no high CAS or mach) detected to trigger any such protection. If the flight crew responded to a pitch-down by misinterpreting it as a stall and went TOGA/stick fwd, then that would have embedded the A330 in compressibility (with all its nasty L.o.C. follow-ons).
.
The above debate disregards where the THS may have been trimmed to and what instantaneous pitch effect it may have had upon the aircraft at autopilot disconnect. That's another ball-of-wax that's unclear to me. i.e. where's the THS being trimmed to when the datum indicated airspeed is artificially low - and how much deflected elevator can the autopilot's baro-hold handle in order to maintain the dialled in flight level (before disconnecting)?
.
Join Date: Jul 2009
Location: France - mostly
Age: 84
Posts: 1,682
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by FluidFlow
I was assuming there would be areas in the Cb that were above saturated as the humid tropical air provides the energy source to power the storm.
Re "leave Pstag/Pstatic the same": If you leave TAS the same, Pstag/Pstatic changes as per my post, and if you also leave OAT the same, TAT reduces by 3.5C.
Originally Posted by Fluidflow
measuring data from one G value atmosphere and calculating others using a different G gives incompatible results
regards,
HN39
(1) At any given temperature
Last edited by HazelNuts39; 30th Jun 2010 at 16:06. Reason: TAT, 'incompatibility', footnote added
Join Date: Jul 2009
Location: Sydney
Age: 79
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
ATSB has just released its report into an A330 incident over Malaysia. It may have some relevence to the AF447 mystery.
It canvasses issues with weather radar capability, detection of high altitude icing, sudden temperature increase, and associated extreme turbulence within an undetected and unforecasted tropical storm, in darkness and at similar latitude, season/month and time of day as the AF447 incident.
FDR records show an almost instantaneous change of 150 degrees in wind direction, coincident with wind speed changing rapidly through a sequence of 20kts->5kts->38kts->20kts through that direction change causing loss of 650m altitude via a -0.48G vertical acceleration, followed by a +1.59G vertical acceleration (rated as severe turbulence). This was associated with a sudden temperature increase and the unexpected sound of ice hitting cockpit windows. I note that all injuries were with people unrestrained by seatbelts just like recovered bodies from AF447, indicating an unexpected incident with no warning to passengers (or flight crew?)
Even though I am a strong supporter of automation I have reservations based on the concerns that many are expressing about its implementation. But in questioning its role in the AF447 accident are we sometimes getting too narrowly focused on the technology thats employed in the parts of automation and concluding that other incidents such as this Malaysian incident and others over Western Australia and the Carribean etc are different or not relevent to this higher level issue because they use different brand/model of instruments? My experience with automation is that interfaces between components should be such that model/brand/technology should be irrelevent as long as the interface specifications are set in concrete and rigidly adhered to. Yet I see some argue that some of the above and other incidents are irrelevent to AF447 because they have different models of pitot....or different levels of software/microcode etc. Iisnt it a governance and design issue?
It canvasses issues with weather radar capability, detection of high altitude icing, sudden temperature increase, and associated extreme turbulence within an undetected and unforecasted tropical storm, in darkness and at similar latitude, season/month and time of day as the AF447 incident.
FDR records show an almost instantaneous change of 150 degrees in wind direction, coincident with wind speed changing rapidly through a sequence of 20kts->5kts->38kts->20kts through that direction change causing loss of 650m altitude via a -0.48G vertical acceleration, followed by a +1.59G vertical acceleration (rated as severe turbulence). This was associated with a sudden temperature increase and the unexpected sound of ice hitting cockpit windows. I note that all injuries were with people unrestrained by seatbelts just like recovered bodies from AF447, indicating an unexpected incident with no warning to passengers (or flight crew?)
Even though I am a strong supporter of automation I have reservations based on the concerns that many are expressing about its implementation. But in questioning its role in the AF447 accident are we sometimes getting too narrowly focused on the technology thats employed in the parts of automation and concluding that other incidents such as this Malaysian incident and others over Western Australia and the Carribean etc are different or not relevent to this higher level issue because they use different brand/model of instruments? My experience with automation is that interfaces between components should be such that model/brand/technology should be irrelevent as long as the interface specifications are set in concrete and rigidly adhered to. Yet I see some argue that some of the above and other incidents are irrelevent to AF447 because they have different models of pitot....or different levels of software/microcode etc. Iisnt it a governance and design issue?
