737-500 missing in Indonesia
Strange they found all those tiny bits of the CVR but just not the key storage parts? Not even damaged remains?
Watch the video of the FDR being removed from the container. That's just the (already detached) memory module, which clearly separated from the FDR chassis on impact. It seems likely that the CVR did the same.
Less Hair
As mangled as the FDR and the CVR control unit look it is no wonder that the parts are all over the place. You can assume that the plane completely disintegrated on impact at the ocean surface and all mangled parts somehow sunk to the ocean bottom. Even if it is only 15m deep the parts can be several meters apart. Dive and underwater visibility conditions are poor as you can see in the video. So it might take some time until they find the CVR data module or whatever is left over.
As mangled as the FDR and the CVR control unit look it is no wonder that the parts are all over the place. You can assume that the plane completely disintegrated on impact at the ocean surface and all mangled parts somehow sunk to the ocean bottom. Even if it is only 15m deep the parts can be several meters apart. Dive and underwater visibility conditions are poor as you can see in the video. So it might take some time until they find the CVR data module or whatever is left over.
Further to that, the sea bed is metres deep in mud. Finding a small component under such conditions must be extremely difficult, especially with limited visibility in the water.
Janner200
What you note is fair in general. This aircraft was levelled off at the time and controlling to speed by some form (ATR or manual thrust) and so the power setting would not be high when things went off the rails. It is common to have a level off in the departure out of JKT, even more common if departing out of Halim. The N1/N2 at the start of this is not going to be at a climb power level, they will be down quite low.... I found a copy of my old B735/56-3-20K FPPM.... (the accident plane was set up for -3B1 at 20K thrust) for the speed and alt that they were at, and for average pax weights, some cargo, fuel for outa nd back and reserve, the plane will be around 46T, and would have an N1 of around 67.7%, which is a low thrust setting. The actual setting on the day will be lower, which would give LRC for around 330 TAS, and they were well below that. Weight changes within a few tons doesn't change that much, so it is safe to assume that the engines going into the event were not at a high thrust setting. Hop in any 3,4,(5?) sim and set up the thrust, it will be low.
The photo shows a GV/Stator series, that is part circumference. With a disc failure, the characteristic failure is into 3 pieces for which the physics is interesting as to why. the immediate release trajectory is normal to the shaft and only parts remaining attached to the shaft if any would impact stators in front or behind the disc station. I would be considering that a partial stator circumference is consequential to impact breakup rather than direct evidence of a disc rupture. Its a while since I crawled into the wheel bay of a 735, but my recollection is that the HYD reservoirs which are accessible there, are not near the line of the turbines, the concern would be that, with a rupture of a disc, it may take out one HYD system directly related to the engine (the hyd lines to the EDP run along the way of the pylon...) and the other system could (unlikely but possible) be impacted, but the standby HYD system which you would really like to have if an engine failure occurs and you have no #1 and #2 HYD systems, would not be in line for debris impact, at least unlikely. The 737 has adequate handling; it deals with an engine failure normally, without too much issue. The ailerons are adequate, (they are a different design to the NG and MAX, shorter span but larger chord, which added to the buzz issues and the need for the outer series of VGs on the classic wing, but they are adequate) The rudder is adequate but needs HYD from some source. Without #1, #2 or the STBY RUDDER, then the plane is going to be less fun, and lateral directional control will be more interesting, no hyd, you have manual ailerons and elevators... no spoilers (actually spoilers will tend to rise partially in total loss of HYD). It will still take some time to get into difficulties, so from a speed of 250KCAS or thereabouts, to get down to losing lateral control would take some time, and that isn't consistent with the minimal information that exists so far.
Inadvertent TR deployment would be annoying but the plane was effectively well set up to have a mild controllability effect from such an event. It was not at a high power setting, and not at very high speed, or at very low speed. Still not much fun, but not usually catastrophic (not a Lauda type condition. Lauda 4 was at quite high power, and there was a window for recovery action of approximately 12 seconds, after which the event was going to be catastrophic)
Attitude instrument failure or erroneous displays are a pain and have excessively high loss rates. The Adam Air event was pretty unique, it's not often that a self-inflicted main attitude display failure occurs but it does happen ( the B744 with the new captain who did a "quick align" of the IRUs at the HP, and was then given an immediate TO clearance, rolled onto the runway with the PFD and NDs all flagged out, and rolled down the runway saying "she'll be right mate. they will come back at rotate..." which they didn't.. during the pre GPS type course the function of the TOGA switches may have been slept through). P2-CLC (MSN27323) was an EFIS cockpit, with an EADI and EHSI setup, so a failure of an attitude platform would result in a loss of the associated display and a fail message on the EADI. An alternate attitude source would have been available for selection.
Whatever happened, occurred rapidly, and led to a very low nose attitude, which still looks suspiciously like a lateral upset at the start. Silkair sim reconstructions showed that it was exceedingly difficult to get to the flightpath that was recorded, which is relevant only in the fact that it showed that to get a nose-low condition rapidly, a rollover was almost always needed, as USAir 427 and UAL585 also showed for other reasons. Flash/Sharm indicated other means by which a rollover could arise, and also led to a fair bit of acrimony in the analysis and the conclusions. The flight phase that this event occurred at is very different to Silkair and would make it improbable that a pilot caused event arose, not impossible, but extremely unlikely. Both pilots are almost certainly in the cockpit at that time, 4 minutes after takeoff, 10,000' around weather, no one is going to be in the bathroom or galley instead of their designated seat position. That doesn't say it is impossible, but it is extremely unlikely and would be novel in the experience of human factors forward of the flight deck door.
The recorders will give some answers and NTSC have some investigators and board members that have exhibited courage and integrity on a number of occasions, I expect that the report will disclose the truth.
What you note is fair in general. This aircraft was levelled off at the time and controlling to speed by some form (ATR or manual thrust) and so the power setting would not be high when things went off the rails. It is common to have a level off in the departure out of JKT, even more common if departing out of Halim. The N1/N2 at the start of this is not going to be at a climb power level, they will be down quite low.... I found a copy of my old B735/56-3-20K FPPM.... (the accident plane was set up for -3B1 at 20K thrust) for the speed and alt that they were at, and for average pax weights, some cargo, fuel for outa nd back and reserve, the plane will be around 46T, and would have an N1 of around 67.7%, which is a low thrust setting. The actual setting on the day will be lower, which would give LRC for around 330 TAS, and they were well below that. Weight changes within a few tons doesn't change that much, so it is safe to assume that the engines going into the event were not at a high thrust setting. Hop in any 3,4,(5?) sim and set up the thrust, it will be low.
The photo shows a GV/Stator series, that is part circumference. With a disc failure, the characteristic failure is into 3 pieces for which the physics is interesting as to why. the immediate release trajectory is normal to the shaft and only parts remaining attached to the shaft if any would impact stators in front or behind the disc station. I would be considering that a partial stator circumference is consequential to impact breakup rather than direct evidence of a disc rupture. Its a while since I crawled into the wheel bay of a 735, but my recollection is that the HYD reservoirs which are accessible there, are not near the line of the turbines, the concern would be that, with a rupture of a disc, it may take out one HYD system directly related to the engine (the hyd lines to the EDP run along the way of the pylon...) and the other system could (unlikely but possible) be impacted, but the standby HYD system which you would really like to have if an engine failure occurs and you have no #1 and #2 HYD systems, would not be in line for debris impact, at least unlikely. The 737 has adequate handling; it deals with an engine failure normally, without too much issue. The ailerons are adequate, (they are a different design to the NG and MAX, shorter span but larger chord, which added to the buzz issues and the need for the outer series of VGs on the classic wing, but they are adequate) The rudder is adequate but needs HYD from some source. Without #1, #2 or the STBY RUDDER, then the plane is going to be less fun, and lateral directional control will be more interesting, no hyd, you have manual ailerons and elevators... no spoilers (actually spoilers will tend to rise partially in total loss of HYD). It will still take some time to get into difficulties, so from a speed of 250KCAS or thereabouts, to get down to losing lateral control would take some time, and that isn't consistent with the minimal information that exists so far.
Inadvertent TR deployment would be annoying but the plane was effectively well set up to have a mild controllability effect from such an event. It was not at a high power setting, and not at very high speed, or at very low speed. Still not much fun, but not usually catastrophic (not a Lauda type condition. Lauda 4 was at quite high power, and there was a window for recovery action of approximately 12 seconds, after which the event was going to be catastrophic)
Attitude instrument failure or erroneous displays are a pain and have excessively high loss rates. The Adam Air event was pretty unique, it's not often that a self-inflicted main attitude display failure occurs but it does happen ( the B744 with the new captain who did a "quick align" of the IRUs at the HP, and was then given an immediate TO clearance, rolled onto the runway with the PFD and NDs all flagged out, and rolled down the runway saying "she'll be right mate. they will come back at rotate..." which they didn't.. during the pre GPS type course the function of the TOGA switches may have been slept through). P2-CLC (MSN27323) was an EFIS cockpit, with an EADI and EHSI setup, so a failure of an attitude platform would result in a loss of the associated display and a fail message on the EADI. An alternate attitude source would have been available for selection.
Whatever happened, occurred rapidly, and led to a very low nose attitude, which still looks suspiciously like a lateral upset at the start. Silkair sim reconstructions showed that it was exceedingly difficult to get to the flightpath that was recorded, which is relevant only in the fact that it showed that to get a nose-low condition rapidly, a rollover was almost always needed, as USAir 427 and UAL585 also showed for other reasons. Flash/Sharm indicated other means by which a rollover could arise, and also led to a fair bit of acrimony in the analysis and the conclusions. The flight phase that this event occurred at is very different to Silkair and would make it improbable that a pilot caused event arose, not impossible, but extremely unlikely. Both pilots are almost certainly in the cockpit at that time, 4 minutes after takeoff, 10,000' around weather, no one is going to be in the bathroom or galley instead of their designated seat position. That doesn't say it is impossible, but it is extremely unlikely and would be novel in the experience of human factors forward of the flight deck door.
The recorders will give some answers and NTSC have some investigators and board members that have exhibited courage and integrity on a number of occasions, I expect that the report will disclose the truth.
Old King Coal
re fake or otherwise, if referring to #253 the video audio is consistent with the NTSC accident report readout, and if you run an FFT of the audio and check SPL, the later part is consistent with the rapid descent and the break up of the aircraft, you can do the maths on the acoustics from the cruise state to determine the increase in air noise, which is an analogue of freestream flow levels (gotta account for the normal shock-related noise over the top of the cockpit). Take an example of the time deltas between any of the transmissions noted in the report and the audio, and they are accurate to 1 millisecond, so I would discount the proposition that the audio is faked.
The original report (KNKT/07.01/08.01.36 BOEING 737–4Q8 PK–KKW MAKASSAR STRAIT, SULAWESI REPUBLIC OF INDONESIA 1 JANUARY 2007) did not include a complete transcript of the CVR, but did include partial transcripts of the A/G Comms and of the cockpit comms leading up to the upset, including the discussion on the IRSs and the GPWS Mode VI Bank Angle callouts. The FDR transcript of the last 2 minutes of the flight is in the report.
As an aside I had input to the investigation as an independent expert related to the flight path, and was aware of the data, but had never previously heard the audiotape until this link was shown. (Previously I had used CVR SPL to determine the engine state and the CAS of a widebody accident where the DFDR was destroyed totally.)
The calculated highest speed encountered was transonic, just below sonic, recovery was severely compromised before the structural failure of the tail finally removed all question.
[Years after this in dive test of this wing we ran a 3D DES analysis of the wing at high speed and showed that eventually, the aircraft would encounter a collapse in CL from the wing for a given AOA, expected, which was caused by the formation of a lower surface normal shockwave, not so expected... which then led to an analysis as to the trim change that would arise, for a given stab setting. In the end, it looked like the flight path would tend to lower rapidly due to loss of lift, while the trim would tend to offset that slightly, the net result being a pitch down. The loss of lift was coincident with the development of normal shocks on the bottom of the wing. In the end, running out towards MDive we descended with power on so that a thrust reduction would permit a reduction in speed, and we were quite happy not to go too far outside of the MMO of the aircraft to demonstrate compliance with the Part. Axelson in 1947 wrote a good memorandum (NACA RM A7024) which spoke about the effect on longitudinal stability from the collapse of main wing lift AOA slope at higher Mach. the conventional wisdom of Mach-tuck causation (AP3456A, aero for "non-marines" etc) being from the effect of the aft movement of Cp with shock migration rearward with increasing Mach, and the change in downwash incidence to the tail appeared to be only a partial truth, the development of a shock on the lower surface of the wing altered the zero-lift AOA considerably, and that meant a collapse if CL, which has an adverse flight path angle effect]. So, what the heck, why rabbit on about the cause of the pitch down... simple; the cause is from a reduction in the zero-lift angle of attack, so to get the same lift as before, the wing has to be at a higher AOA than the trim point, therefore all else being equal, the flight path will decay, unless. more nose-up trim is applied, which we see as an effective pitch down moment. The moment is actually not significantly altered, it is that case that the flight path degrades for the given trim state; it May sound like semantics, but if you are out in that region, it gives a hint on avoidance and recovery. Notably, the collapse of CL that occurs is coincident with a reduction of the Cm, and that was the reason for going into the analysis in some depth, as conventional wisdom suggests that wing Cm increases from the migration aft of the Cp, and, it does not.
The Adam 574 tape is adequate to determine the frequency of the cooling fans are in the background, which indicates what the engines were doing in acceleration or deceleration, which happens to be consistent with the DFDR data anyway, not a surprise, but supporting the authenticity of the recording. About the only curiosity coming out of the CFR tape vs the report is that the thump sound that was considered to be the commencement of the breakup of the tail, while it is at the same time as the vertical g reversal, is about 4 seconds before the highest pitch attitude in the recovery, at which point the nose drops once again. The later pitch rate reversal is the greatest rate that is recorded, and probably results from a final farewell of the horizontal stab, following the loss of elevators 4 seconds earlier... at that later moment, there is a very large lateral acceleration, possibly the horiz stab going off in pieces.
For what it is worth, the plane held together longer than any design requirement would require. The aircraft was completely recoverable had the wings been rolled to level earlier while the guys were pulling high g. The bank angle was over 30 degrees for more than a minute, and beyond 90 degrees for over 16 seconds, while pulling g between 1.5 and 3g Had the bank been reduced to near level at any reasonable time, the recovery was possible, but history shows we still have more hard learning to do then on recovery from UA, as occurred with AF447 etc.
FFT of ADAM AIR 574 questioned CVR recording
re fake or otherwise, if referring to #253 the video audio is consistent with the NTSC accident report readout, and if you run an FFT of the audio and check SPL, the later part is consistent with the rapid descent and the break up of the aircraft, you can do the maths on the acoustics from the cruise state to determine the increase in air noise, which is an analogue of freestream flow levels (gotta account for the normal shock-related noise over the top of the cockpit). Take an example of the time deltas between any of the transmissions noted in the report and the audio, and they are accurate to 1 millisecond, so I would discount the proposition that the audio is faked.
The original report (KNKT/07.01/08.01.36 BOEING 737–4Q8 PK–KKW MAKASSAR STRAIT, SULAWESI REPUBLIC OF INDONESIA 1 JANUARY 2007) did not include a complete transcript of the CVR, but did include partial transcripts of the A/G Comms and of the cockpit comms leading up to the upset, including the discussion on the IRSs and the GPWS Mode VI Bank Angle callouts. The FDR transcript of the last 2 minutes of the flight is in the report.
- The audio is consistent with the SPL of the spectrum.
- the timing between comms from Ujung to the aircraft is consistent with those that occurred.
- the time between the comms and the breakup event indicated by the rapid reversal of g load from +3.5 to -2.5 is consistent with the data in the report.
As an aside I had input to the investigation as an independent expert related to the flight path, and was aware of the data, but had never previously heard the audiotape until this link was shown. (Previously I had used CVR SPL to determine the engine state and the CAS of a widebody accident where the DFDR was destroyed totally.)
The calculated highest speed encountered was transonic, just below sonic, recovery was severely compromised before the structural failure of the tail finally removed all question.
[Years after this in dive test of this wing we ran a 3D DES analysis of the wing at high speed and showed that eventually, the aircraft would encounter a collapse in CL from the wing for a given AOA, expected, which was caused by the formation of a lower surface normal shockwave, not so expected... which then led to an analysis as to the trim change that would arise, for a given stab setting. In the end, it looked like the flight path would tend to lower rapidly due to loss of lift, while the trim would tend to offset that slightly, the net result being a pitch down. The loss of lift was coincident with the development of normal shocks on the bottom of the wing. In the end, running out towards MDive we descended with power on so that a thrust reduction would permit a reduction in speed, and we were quite happy not to go too far outside of the MMO of the aircraft to demonstrate compliance with the Part. Axelson in 1947 wrote a good memorandum (NACA RM A7024) which spoke about the effect on longitudinal stability from the collapse of main wing lift AOA slope at higher Mach. the conventional wisdom of Mach-tuck causation (AP3456A, aero for "non-marines" etc) being from the effect of the aft movement of Cp with shock migration rearward with increasing Mach, and the change in downwash incidence to the tail appeared to be only a partial truth, the development of a shock on the lower surface of the wing altered the zero-lift AOA considerably, and that meant a collapse if CL, which has an adverse flight path angle effect]. So, what the heck, why rabbit on about the cause of the pitch down... simple; the cause is from a reduction in the zero-lift angle of attack, so to get the same lift as before, the wing has to be at a higher AOA than the trim point, therefore all else being equal, the flight path will decay, unless. more nose-up trim is applied, which we see as an effective pitch down moment. The moment is actually not significantly altered, it is that case that the flight path degrades for the given trim state; it May sound like semantics, but if you are out in that region, it gives a hint on avoidance and recovery. Notably, the collapse of CL that occurs is coincident with a reduction of the Cm, and that was the reason for going into the analysis in some depth, as conventional wisdom suggests that wing Cm increases from the migration aft of the Cp, and, it does not.
The Adam 574 tape is adequate to determine the frequency of the cooling fans are in the background, which indicates what the engines were doing in acceleration or deceleration, which happens to be consistent with the DFDR data anyway, not a surprise, but supporting the authenticity of the recording. About the only curiosity coming out of the CFR tape vs the report is that the thump sound that was considered to be the commencement of the breakup of the tail, while it is at the same time as the vertical g reversal, is about 4 seconds before the highest pitch attitude in the recovery, at which point the nose drops once again. The later pitch rate reversal is the greatest rate that is recorded, and probably results from a final farewell of the horizontal stab, following the loss of elevators 4 seconds earlier... at that later moment, there is a very large lateral acceleration, possibly the horiz stab going off in pieces.
For what it is worth, the plane held together longer than any design requirement would require. The aircraft was completely recoverable had the wings been rolled to level earlier while the guys were pulling high g. The bank angle was over 30 degrees for more than a minute, and beyond 90 degrees for over 16 seconds, while pulling g between 1.5 and 3g Had the bank been reduced to near level at any reasonable time, the recovery was possible, but history shows we still have more hard learning to do then on recovery from UA, as occurred with AF447 etc.
FFT of ADAM AIR 574 questioned CVR recording
Last edited by fdr; 17th Jan 2021 at 05:15. Reason: forgot "IMHO"
Recurring Autothrottle problem
Indonesian media quoting unrectified(?) autothrottle problem in the accident aircraft...
https://today.line.me/id/v2/article/op96ep
Asymmetric thrust due to autothrottle problem has led to fatal accident in B737 before (but, in a different phase of flight).
In my previous post 79, when observing the lower performance, specifically the slower speeds from about 4000 feet on up, a speculative thought was that of a pitot/static system malfunction.
However, a new speculative thought occurs. If the autothrottle was engaged and one engine gently rolled back to, or near to flight idle with the autothrottle active and the other engine maintained climb thrust...the performance...specifically the rate of climb and/or the speed would be reduced from normal. The secondary flight control effects of the thrust asymmetry would be masked by the autopilot.
If IAS continued to decreased, the aileron control would offset ("cross") until the flight path eventually deviated laterally due to untrimmed rudder.
And then if the autopilot was then disconnected with the controls all crossed, the sudden out of trim forces would be unexpected and cause a rapid roll...
Total speculation of course...
https://www.dailytelegraph.com.au/ne...ct/news-story/
A Tempo source who is aware of the problem said that the SJ-182 aircraft autothrottle system has experienced recurring problems. "The autothrottle has been repetitive for a month," he told Koran Tempo. Regarding the SJ-182 autothrottle, sources said the system had experienced problems since December 2020 or when the plane returned to flight after being grounded for nine months. Soerjanto explained, if the system had problems, it should have been anticipated by manual regulation. "No problem, just use your hands like the old days," he said.
Asymmetric thrust due to autothrottle problem has led to fatal accident in B737 before (but, in a different phase of flight).
In my previous post 79, when observing the lower performance, specifically the slower speeds from about 4000 feet on up, a speculative thought was that of a pitot/static system malfunction.
However, a new speculative thought occurs. If the autothrottle was engaged and one engine gently rolled back to, or near to flight idle with the autothrottle active and the other engine maintained climb thrust...the performance...specifically the rate of climb and/or the speed would be reduced from normal. The secondary flight control effects of the thrust asymmetry would be masked by the autopilot.
If IAS continued to decreased, the aileron control would offset ("cross") until the flight path eventually deviated laterally due to untrimmed rudder.
And then if the autopilot was then disconnected with the controls all crossed, the sudden out of trim forces would be unexpected and cause a rapid roll...
Total speculation of course...
The transport minister said on Saturday that the jet appeared to deviate from its intended course just before it disappeared from radar, AFP reports.
“The aircraft’s final moments are … very concerning as the speed that (it) was flying at that altitude was much lower than expected,” said Stephen Wright, professor of aircraft systems at Finland’s Tampere University.
“The aircraft’s final moments are … very concerning as the speed that (it) was flying at that altitude was much lower than expected,” said Stephen Wright, professor of aircraft systems at Finland’s Tampere University.
Last edited by FlexibleResponse; 17th Jan 2021 at 06:18. Reason: Added speculation...
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PR0PWASH
Their pickup range is low, just like a contactless payment card. Deliberately designed to be like that.
It's a passive technology, remotely powered by high frequency magnetic energy from the data collection device, so anyone scanning a muddy seabed would almost have to be touching an item before they get a signal.
Their pickup range is low, just like a contactless payment card. Deliberately designed to be like that.
It's a passive technology, remotely powered by high frequency magnetic energy from the data collection device, so anyone scanning a muddy seabed would almost have to be touching an item before they get a signal.
However, a new speculative thought occurs. If the autothrottle was engaged and one engine gently rolled back to, or near to flight idle with the autothrottle active and the other engine maintained climb thrust...the performance...specifically the rate of climb and/or the speed would be reduced from normal. The secondary flight control effects of the thrust asymmetry would be masked by the autopilot
Last edited by fox niner; 17th Jan 2021 at 09:40.
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There is a CASA AD from 1/2001 (AD/B737/149) for the B737-300/400/500, with regard to the autothrottle computer.
Boeing Alert Service Bulletin 737-22A1130, dated 24 Sept 1998 advises that replacement of the existing autothrottle computer with a new, improved autothrottle computer was necessary, due to the earlier autothrottle computer proving to be unreliable.
Part numbers are provided in the AD for the earlier model of computer, and Boeing advised that "Autothrottle computers with Part Numbers 10-62017-1, -2, -3, -4, -5, -11, -21, -23, -25, or -27, may not be fitted to any aeroplane to replace an installed computer." (my bold and italics)
The background to the necessary autothrottle computer replacement was as follows;
"The aircraft manufacturer has received several reports of asymmetric thrust conditions during flight caused by irregular autothrottle operation in which the thrust levers slowly move apart, causing the aeroplane to bank excessively, and go into a roll.
This Directive requires replacement of the existing autothrottle computer with a new, improved autothrottle computer.
This action is intended to prevent a severe asymmetric thrust condition developing during flight, which could result in loss of control of the aeroplane." (my bold and italics, again).
https://www.legislation.gov.au/Detai...9-c9c2f7477bc3
IF .. and this is entirely speculative .. Sriwijaya, in its regular penny-pinching mode (seeing as it specialises in buying only used aircraft, and that penny-pinching will almost certainly extend into maintenance - particularly under cashflow-affected COVID-19 operating conditions), fitted this aircraft with a "good, used" autothrottle computer, with the above part numbers - either in ignorance, or in disobediance of Boeings directive - it could be possible that the faulty, earlier version of autothrottle computer fitted, could have created a severe asymmetric thrust condition, which the crew were unable to diagnose accurately, and deal with quickly - thus causing the loss of control of the aircraft? Stranger things have happened.
Boeing Alert Service Bulletin 737-22A1130, dated 24 Sept 1998 advises that replacement of the existing autothrottle computer with a new, improved autothrottle computer was necessary, due to the earlier autothrottle computer proving to be unreliable.
Part numbers are provided in the AD for the earlier model of computer, and Boeing advised that "Autothrottle computers with Part Numbers 10-62017-1, -2, -3, -4, -5, -11, -21, -23, -25, or -27, may not be fitted to any aeroplane to replace an installed computer." (my bold and italics)
The background to the necessary autothrottle computer replacement was as follows;
"The aircraft manufacturer has received several reports of asymmetric thrust conditions during flight caused by irregular autothrottle operation in which the thrust levers slowly move apart, causing the aeroplane to bank excessively, and go into a roll.
This Directive requires replacement of the existing autothrottle computer with a new, improved autothrottle computer.
This action is intended to prevent a severe asymmetric thrust condition developing during flight, which could result in loss of control of the aeroplane." (my bold and italics, again).
https://www.legislation.gov.au/Detai...9-c9c2f7477bc3
IF .. and this is entirely speculative .. Sriwijaya, in its regular penny-pinching mode (seeing as it specialises in buying only used aircraft, and that penny-pinching will almost certainly extend into maintenance - particularly under cashflow-affected COVID-19 operating conditions), fitted this aircraft with a "good, used" autothrottle computer, with the above part numbers - either in ignorance, or in disobediance of Boeings directive - it could be possible that the faulty, earlier version of autothrottle computer fitted, could have created a severe asymmetric thrust condition, which the crew were unable to diagnose accurately, and deal with quickly - thus causing the loss of control of the aircraft? Stranger things have happened.
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Old electronics guy
Yes I know, I was thinking of the situation where the memory module was under a layer of silt, they are so inexpensive and perhaps if glued well to the modules would be a simple to add extra insurance in that situation, perhaps using slightly higher powered detectors with a greater range
Yes I know, I was thinking of the situation where the memory module was under a layer of silt, they are so inexpensive and perhaps if glued well to the modules would be a simple to add extra insurance in that situation, perhaps using slightly higher powered detectors with a greater range
FlexibleResponse
Undetected, that would quite possibly result in a loss of control with a rapid roll-off, as the APLT exceeds its lateral authority and trips off, with no rudder input. As the APLT disconnects, the aileron applied by the APLT will neutralize rapidly, and the aircraft will have a very high roll rate away from the engine that is at high thrust. That is the same sort of scenario as the CI006 near loss in 1985 following #4 engine failure in the cruise at FL410, and the ensuing 30,000' dive leaving lots of bit behind.
That sadly has the ring of truth to it, and from IDN, there is a high likelihood that the DFDR readout has shown that, and it has been leaked to the public inadvertently. This is similar to the China Southern 3943 B733 loss. The potential for asymmetry due to a clutch pack fault was a system fault that was practiced back in the day.
Undetected, that would quite possibly result in a loss of control with a rapid roll-off, as the APLT exceeds its lateral authority and trips off, with no rudder input. As the APLT disconnects, the aileron applied by the APLT will neutralize rapidly, and the aircraft will have a very high roll rate away from the engine that is at high thrust. That is the same sort of scenario as the CI006 near loss in 1985 following #4 engine failure in the cruise at FL410, and the ensuing 30,000' dive leaving lots of bit behind.
That sadly has the ring of truth to it, and from IDN, there is a high likelihood that the DFDR readout has shown that, and it has been leaked to the public inadvertently. This is similar to the China Southern 3943 B733 loss. The potential for asymmetry due to a clutch pack fault was a system fault that was practiced back in the day.
I think he meant what if the engine rolled back, not its thrust lever. So both thrust levers would be driven forward by the single servo and the clutches, but if one engine was not supplying power owing to, say blockage or failure in the fuel control unit, an asymmetric thrust situation could still occur? Gotta look at the N1s !
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US NTSB team arrives in Indonesia to look into jet crash Indonesian officials say a team from the U.S. National Transportation Safety Board has arrived in Indonesia’s capital to join the investigation into the crash of a Sriwijaya Air Boeing 737-500. The team also comprises representatives from the U.S. Federal Aviation Administration, Boeing and General Electric. They joined personnel from Singapore’s Transportation Safety Investigation Bureau at the search and rescue command center at Tanjung Priok port in Jakarta to see some of the plane debris.
- https://wbng.com/2021/01/16/us-ntsb-...nto-jet-crash/
- https://wbng.com/2021/01/16/us-ntsb-...nto-jet-crash/
