Qantas 744 Depressurisation
What're the odds? (100% apparently, but I would never have guessed it.)
I sure hope that the final report describes in detail on how these one of a kind events occured
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Whilst I'm prepared to believe that the missing cylinder exited through the hole in the pressure hull, I'm sceptical that an exploded (ie fractured) cylinder could result in all fragments being evacuated (though clearly the vacuum effect of the hull rupture would be considerable and anything loose could be sucked out). <snip>
I'd need to see the exact shape of the hole(s) in the cabin floor and compare them with the dimensions of the cylinder . . .
Incredible I'd say.
<snip>
I'd need to see the exact shape of the hole(s) in the cabin floor and compare them with the dimensions of the cylinder . . .
Incredible I'd say.
<snip>
People speak of the bottles being castings. but steel forgings seem possible. The bottle was more than ten years old; what happened to it in the meantime?
Whoever was seated on the upper deck above the cylinder is extremely fortunate that:
- It did not go straight up as it may have penetrated the upper deck
- Energy was dissipated hitting the door handle
- the cylinder assumed an oblique trajectory to the upper deck so that it bounced off rather than penetrate.
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Similar circumstances (CVR stays on until overwritten) seem to often occur quite often when "incidents" do not progress to "accidents". One may draw one's own conclusions...
Are you saying that the flight crew deliberately left the CVR running in the hope it would overwrite the incident? That seems to be the inference from your statement. That seems to be a ridiculous reasoning based on what we have all read and understood of the actions and character of the pilot and first officer during and after the whole thing.
Please do justify your 'conclusions'.
Not disclosed in this report is the reason why the oxygen bottle may have failed. I cannot believe the ATSB is that dumb. In fact they've been unable to come to any conclusions. However a very simple conjecture can address the distinct probabilities.
And I suspect they're a lot smarter than you are.
Last edited by Spotted Reptile; 30th Aug 2008 at 01:25. Reason: double post
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The CVR is this case would prove nothing except provide a sound bite of the explosion for examination.
The crew performed as per their training and handled the associated mechanical failures correctly and well.
The crew performed as per their training and handled the associated mechanical failures correctly and well.
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A/P's & Oxy Reg,s
For clarification on My comments post 1037
AUTOPILOTs,
If the A/P LVDT & the OUTPUT LVDT disagree the A/P will disconnect. How the manual input is allowed by the A/P I can no longer remember exactly. Refresher training would be handy for everyone!
A cam-out only occurs when 2 A/P’s are engaged (Dual Engaged, APP mode only) and one commands different to the other. As the 2 engaged do not distinguish which one is in error the lessor of the same direction output will be the control (fail passive).
Only when there is a large difference will both disengage.
In Triple Engage APP, the one in error is over ridden by the other 2 (fail operational)
Large difference will cause disconnect of the one voted failed A/P by the other 2.
During CRZ only one A/P can be engaged so no cam-out can occur.
OXYGEN REGULATOR
whilst it will probably check the flow, it is mounted on a Tee piece directly onto the shutoff valve outlet of the cylinder and is more robust than the down stream plumbing. This later plumbing will be the first to break and therefore all other cylinders will discharge through the broken pipe.
SC
AUTOPILOTs,
If the A/P LVDT & the OUTPUT LVDT disagree the A/P will disconnect. How the manual input is allowed by the A/P I can no longer remember exactly. Refresher training would be handy for everyone!
A cam-out only occurs when 2 A/P’s are engaged (Dual Engaged, APP mode only) and one commands different to the other. As the 2 engaged do not distinguish which one is in error the lessor of the same direction output will be the control (fail passive).
Only when there is a large difference will both disengage.
In Triple Engage APP, the one in error is over ridden by the other 2 (fail operational)
Large difference will cause disconnect of the one voted failed A/P by the other 2.
During CRZ only one A/P can be engaged so no cam-out can occur.
OXYGEN REGULATOR
whilst it will probably check the flow, it is mounted on a Tee piece directly onto the shutoff valve outlet of the cylinder and is more robust than the down stream plumbing. This later plumbing will be the first to break and therefore all other cylinders will discharge through the broken pipe.
SC
Last edited by Short_Circuit; 30th Aug 2008 at 04:34.
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As written:
Spotted reptile's contentious demand as a "reply"
SR - you seem presumptuously argumentative - a bit inappropriate for someone with only 3 posts on the counter... even for an Aussie.
I meant exactly what was said. Clearly many circumstances can occur which cause CVR tapes to be overwritten after a serious incident of this sort. The obvious first responsibility and focus of the flight crew is to assure the safety of passengers, crew and the aircraft itself, an activity that may be very time consuming and may involve long delays before routine housekeeping activities resume.
It probably is true that some airlines do not have an explicit SOP for the protocol to secure the CVR contents following an incident; this might be desirable. Sometimes the elapsed time to the "end" of the incident period (which may be hard to delineate clearly when in the thick of it) is long enough for the CVR to be overwritten anyway - as was nearly always the case with the older, shorter-running CVR's.
I certainly did not and do not mean to suggest that the conduct of the Qantas crew in this odd and complex incident was anything other than exemplary.
Similar circumstances (CVR stays on until overwritten) seem to often occur quite often when "incidents" do not progress to "accidents". One may draw one's own conclusions...
Please do justify your 'conclusions'.
I meant exactly what was said. Clearly many circumstances can occur which cause CVR tapes to be overwritten after a serious incident of this sort. The obvious first responsibility and focus of the flight crew is to assure the safety of passengers, crew and the aircraft itself, an activity that may be very time consuming and may involve long delays before routine housekeeping activities resume.
It probably is true that some airlines do not have an explicit SOP for the protocol to secure the CVR contents following an incident; this might be desirable. Sometimes the elapsed time to the "end" of the incident period (which may be hard to delineate clearly when in the thick of it) is long enough for the CVR to be overwritten anyway - as was nearly always the case with the older, shorter-running CVR's.
I certainly did not and do not mean to suggest that the conduct of the Qantas crew in this odd and complex incident was anything other than exemplary.
Diesel Fitter # 1050.
The first thing that happens after many accidents is that the crew licences are inspected, and the report starts with a statment that "...... the flight crew licences were inspected and found to be in order.........." if not, the investigation can stop right there,'cos the fact that a crew member might have a licence that could be slightly defective, i.e. maybe not re-issued ( if required, as is by some States ) after a recent medical that was in itself satisfactory, means that that fact alone was the cause of the accident, and the airline and the insurers can breath again. QED
I once attended a Court of Enquiry into a B-747 total loss where the pilot had deviated by 100 ft. from the proscribed departure route on take-off, which had absolutely nothing to do with the subequent mechanical failure, but the Judge immediately stated that the accident was due to 'pilot error' ( you think I'm joking )
The first thing that happens after many accidents is that the crew licences are inspected, and the report starts with a statment that "...... the flight crew licences were inspected and found to be in order.........." if not, the investigation can stop right there,'cos the fact that a crew member might have a licence that could be slightly defective, i.e. maybe not re-issued ( if required, as is by some States ) after a recent medical that was in itself satisfactory, means that that fact alone was the cause of the accident, and the airline and the insurers can breath again. QED
I once attended a Court of Enquiry into a B-747 total loss where the pilot had deviated by 100 ft. from the proscribed departure route on take-off, which had absolutely nothing to do with the subequent mechanical failure, but the Judge immediately stated that the accident was due to 'pilot error' ( you think I'm joking )
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SR - you seem presumptuously argumentative - a bit inappropriate for someone with only 3 posts on the counter... even for an Aussie.
I meant exactly what was said. Clearly many circumstances can occur which cause CVR tapes to be overwritten after a serious incident of this sort. The obvious first responsibility and focus of the flight crew is to assure the safety of passengers, crew and the aircraft itself, an activity that may be very time consuming and may involve long delays before routine housekeeping activities resume.
I certainly did not and do not mean to suggest that the conduct of the Qantas crew in this odd and complex incident was anything other than exemplary.
CVRs are not erased, ever, by the crew it's not part of any shutdown procedure that I know of. It used to be back in B707 days.
If any of the data was erased it is because the CVR only records about the last 25 minutes of flight and anything prior to that will be overwritten, again and again. Originally designed before decent solid state memory and to capture take off or landing incident data.
The depressurisation event occurred 54 minutes before the aircraft landed so the likelyhood of anything useful remaining on the tape is remote, and further the CVR wasn't shut down until well over 2 hours after the event.
Regards,
BH.
If any of the data was erased it is because the CVR only records about the last 25 minutes of flight and anything prior to that will be overwritten, again and again. Originally designed before decent solid state memory and to capture take off or landing incident data.
The depressurisation event occurred 54 minutes before the aircraft landed so the likelyhood of anything useful remaining on the tape is remote, and further the CVR wasn't shut down until well over 2 hours after the event.
Regards,
BH.
The 777 CVR records 2 hrs ( I think it's 2, but a lot more than 25 mins ) before starting again.
The crew can erase it on the ground if they wish.
In the QF incident the tape had already runout and started to tape over the initial event. Just bad luck for the investigators, nothing sinister.
The crew can erase it on the ground if they wish.
In the QF incident the tape had already runout and started to tape over the initial event. Just bad luck for the investigators, nothing sinister.
Capt.cynical,
I think what Barkly could have said, if he was less "Grumpy"
, was that the report was referenced yesterday by cjsyd in Post 1032.
I42
I think what Barkly could have said, if he was less "Grumpy"
, was that the report was referenced yesterday by cjsyd in Post 1032.I42
Grumpy
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Cynical
Yes it was referenced earlier as was mentioned by India Four Two.
But I used to work for the then BASI and later CAA and have a real interest and read the report online in detail every single line. It was availble online from Thursday.
The series of events are well known - in fact this thread picked it early.
What no one knows is why the cylinder 'let go'.
This is what the ongoing investigation will concentrate on. It will be difficult without some remnants of then cylinder.
Yes it was referenced earlier as was mentioned by India Four Two.
But I used to work for the then BASI and later CAA and have a real interest and read the report online in detail every single line. It was availble online from Thursday.
The series of events are well known - in fact this thread picked it early.
What no one knows is why the cylinder 'let go'.
This is what the ongoing investigation will concentrate on. It will be difficult without some remnants of then cylinder.