Qantas 744 Depressurisation
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Human Factors
Ancient Obs,
Some HUF if you like.
TUC (time of useful consciousness) or EPT (effective performance time) for minimal activity (sitting in a seat) are as follows:
18,000' - 30 mins
22,000' - 10 mins
25,000' - 3 mins
28,000' - 1.5 mins
my guess is that most healthy PAX would not have even needed supplimental O2.
Some HUF if you like.
TUC (time of useful consciousness) or EPT (effective performance time) for minimal activity (sitting in a seat) are as follows:
18,000' - 30 mins
22,000' - 10 mins
25,000' - 3 mins
28,000' - 1.5 mins
my guess is that most healthy PAX would not have even needed supplimental O2.
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oxygen and grease
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Just above the regulators on all of the bottles is the first officers back up aileron cables covered in grease.
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Just above the regulators on all of the bottles is the first officers back up aileron cables covered in grease.
Here's a pic of the cables on another aircraft, sans grease, I prepared earlier...
This was the pic which prompted my question about corrosion inhibitor (unless that is coffee seeping through the floorboards
)As previously mentioned, the inhibitor dries into a waxy substance. The brown stains are perfectly dry. The same stuff is used throughout the aircraft, sometimes making it hard to spot real hydraulic (and other) leaks.
Note the brass and stainless steel fittings of this typical (non-lightweight) Qantas bottle.
Last edited by NSEU; 31st Jul 2008 at 03:35.
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Looking for a failure mechanism... pure conjecture, only.
From the pix at #703 (and before), it would appear that a looseness or failure of the single restraining strap on the bottle, so it is not held securely in position, would allow the top portion of the 13-odd kilos of object+contents to wobble or orbit around on the footplate with considerable freedom, restrained principally by the stainless-steel exit feed line that (presumably) runs over to the adjacent distribution panel.
An extended cycle of such movement would exert strong "working" forces on the bottle's valve-regulator assembly in a variety of directions and angles. Heavy stress applied to a high-pressure valve assembly is a no-no in general, because this eventually promotes some kind of failure.
Continued long enough, the cycling abnormal flexing would seem likely to cause a crystalisation fracture of the metals somewhere in the assembly. This might occur at the valve stem-to-bottle junction, in the valve body, or in the feed line or its fitting. Effect of any of these failures would likely be an initial crack, then a more dramatic break caused by releasing gas pressure. In the process, the increasingly unrestrained bottle would likely tilt enough to come clear of the curved footplate, even while the releasing gas from the degenerating valve assembly would cause increasingly eccentric and powerful motions.
As the top of the valve assembly broke loose, headed upward to punch through the cabin floor and diddle the door handle, the bottle proper would likely be drilling or bashing a hole in the airframe with the blunt end thrashing and battering wide an opening already perhaps started with tears higher up from the pressure of escaping gas. Eventually the liberated cylinder shoots out through the wall opening and through the lightweight fairing, still accelerating as it descends below and under the leading edge of the wing.
Seems like this scenario could make a strong argument for a secondary retaining strap and possibly also smaller-bore flow-limiting exit holes in the cylinders.
From the pix at #703 (and before), it would appear that a looseness or failure of the single restraining strap on the bottle, so it is not held securely in position, would allow the top portion of the 13-odd kilos of object+contents to wobble or orbit around on the footplate with considerable freedom, restrained principally by the stainless-steel exit feed line that (presumably) runs over to the adjacent distribution panel.
An extended cycle of such movement would exert strong "working" forces on the bottle's valve-regulator assembly in a variety of directions and angles. Heavy stress applied to a high-pressure valve assembly is a no-no in general, because this eventually promotes some kind of failure.
Continued long enough, the cycling abnormal flexing would seem likely to cause a crystalisation fracture of the metals somewhere in the assembly. This might occur at the valve stem-to-bottle junction, in the valve body, or in the feed line or its fitting. Effect of any of these failures would likely be an initial crack, then a more dramatic break caused by releasing gas pressure. In the process, the increasingly unrestrained bottle would likely tilt enough to come clear of the curved footplate, even while the releasing gas from the degenerating valve assembly would cause increasingly eccentric and powerful motions.
As the top of the valve assembly broke loose, headed upward to punch through the cabin floor and diddle the door handle, the bottle proper would likely be drilling or bashing a hole in the airframe with the blunt end thrashing and battering wide an opening already perhaps started with tears higher up from the pressure of escaping gas. Eventually the liberated cylinder shoots out through the wall opening and through the lightweight fairing, still accelerating as it descends below and under the leading edge of the wing.
Seems like this scenario could make a strong argument for a secondary retaining strap and possibly also smaller-bore flow-limiting exit holes in the cylinders.
Last edited by arcniz; 30th Jul 2008 at 23:31.
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So correct me if I am wrong but the O2 bottle could still have been sucked out secondary to a rupture in the fuselage and the valve fittings could have simply been ejected upwards in the process of being ripped off the cylinder.
There still appears no evidence of an actual cylinder rupture does there ?
No fragments ejected sideways or into the hold perchance ?
There still appears no evidence of an actual cylinder rupture does there ?
No fragments ejected sideways or into the hold perchance ?
I love the photos so keep them coming.
Do we have an idea of which way the valve stem was launched through the floor and into the ceiling panel. The trajectory might give an idea as to whether the bottle was loose or in place at the time. I'm guessing that a + or - 15 deg cone angle trajectory would be inconclusive, but if it was greater it might be a significant pointer.
I am also reminded that we still don't have a reason for the very large hole in the fuselage, without lesser shrapnel damage holes visible.
The ATSB certainly has their work cut out for them to identify the cascading damages as well as the chicken and the egg.
Do we have an idea of which way the valve stem was launched through the floor and into the ceiling panel. The trajectory might give an idea as to whether the bottle was loose or in place at the time. I'm guessing that a + or - 15 deg cone angle trajectory would be inconclusive, but if it was greater it might be a significant pointer.
I am also reminded that we still don't have a reason for the very large hole in the fuselage, without lesser shrapnel damage holes visible.
The ATSB certainly has their work cut out for them to identify the cascading damages as well as the chicken and the egg.
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Even wearing warm clothing in case of crash might not be a good idea if it's hot at the ends of your trip - grounds for suspicion (or worse) from security...
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Kiwiguy, I agree.
The last picture in post #751 shows the mount that the bottle is strapped against and it clearly shows a failure of where each side of the strap is attached. You would expect the strap to fail, or one of the strap mounts, but not both strap mounts to have sheared at the same time due to their own failure. There is no obvious sign of damage to the adjacent bottle or the cabling that is visible (although this cabling may have moved to its current position after the event).
Now if it was a failure of the skin beneath the wing to body fairing, then the base where the bottle sits could have ejected when the skin failed as it would be attached to either stringer or frame. The bottle would then pivot outward, ripping the strap from the strap mount and disappear out of the hole. The weak point in this 1am theory is that you would imagine that the charge line/ring main supply lines would fail before the brass regulator fitting, which would not allow the regulator to enter the passenger cabin and cause the damage that it is stated it has.
The last picture in post #751 shows the mount that the bottle is strapped against and it clearly shows a failure of where each side of the strap is attached. You would expect the strap to fail, or one of the strap mounts, but not both strap mounts to have sheared at the same time due to their own failure. There is no obvious sign of damage to the adjacent bottle or the cabling that is visible (although this cabling may have moved to its current position after the event).
Now if it was a failure of the skin beneath the wing to body fairing, then the base where the bottle sits could have ejected when the skin failed as it would be attached to either stringer or frame. The bottle would then pivot outward, ripping the strap from the strap mount and disappear out of the hole. The weak point in this 1am theory is that you would imagine that the charge line/ring main supply lines would fail before the brass regulator fitting, which would not allow the regulator to enter the passenger cabin and cause the damage that it is stated it has.
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Being an 'infrequent flyer' you might not be aware that there are extra masks in every PSU (pax service unit: above your head). For example, the 3 seats outboard of a 747, there will be 4 masks drop from the PSU in a depresurisation event. Plenty of masks for all even if yours dont drop.
The location of where the masks failed to deploy will be the issue, not the number, trust me.
The location of where the masks failed to deploy will be the issue, not the number, trust me.
As far as numbers go, 418 out of 484 masks for 346 PAX sounds pretty good to me. 
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The 747-400F Passenger and Crew Oxygen System supply source is a bank of
high-pressure cylinders. Each cylinder has a quantity of oxygen
equivalent to 115 cubic feet (3030 liters), when charged to 1850 psig at
760 mm Hg and 70 degrees F. The cylinders are retained firmly in place
with clamps.
Cylinder positions 1 through 7 are located in the forward cargo
compartment right hand sidewall between STA 720 and STA 880.
Because cylinders from position 4 to position 7 are customer
options, actual passenger system cylinder quantities in the sidewall
may vary.
Cylinder positions 8 through 21 are located in the forward cargo
compartment ceiling, between STA 620 and STA 780. Because cylinders
from position 8 to position 21 are customer options, actual
passenger system cylinder quantities in the ceiling may vary.
Cylinder positions 1 through 2 are located in the forward cargo
compartment right hand sidewall between STA 680 and STA 720.
Because cylinder position 2 is a customer option, actual Crew system
cylinder quantities in the sidewall may vary.
Older in-service steel cylinders are interchangeable with the graphite
composite cylinders.
Every cylinder has an associated high-pressure regulator, which
reduces the pressure for reasons of safety, to the intermediate
system working pressure of 600-680 psig.
C_A_U_T_I_O_N_: DO NOT TIGHTEN THE FITTINGS AND CONNECTIONS MORE THAN
THE TORQUE WHICH IS PERMITTED. THIS CAN CAUSE DAMAGE
TO THESE PARTS.
high-pressure cylinders. Each cylinder has a quantity of oxygen
equivalent to 115 cubic feet (3030 liters), when charged to 1850 psig at
760 mm Hg and 70 degrees F. The cylinders are retained firmly in place
with clamps.
Cylinder positions 1 through 7 are located in the forward cargo
compartment right hand sidewall between STA 720 and STA 880.
Because cylinders from position 4 to position 7 are customer
options, actual passenger system cylinder quantities in the sidewall
may vary.
Cylinder positions 8 through 21 are located in the forward cargo
compartment ceiling, between STA 620 and STA 780. Because cylinders
from position 8 to position 21 are customer options, actual
passenger system cylinder quantities in the ceiling may vary.
Cylinder positions 1 through 2 are located in the forward cargo
compartment right hand sidewall between STA 680 and STA 720.
Because cylinder position 2 is a customer option, actual Crew system
cylinder quantities in the sidewall may vary.
Older in-service steel cylinders are interchangeable with the graphite
composite cylinders.
Every cylinder has an associated high-pressure regulator, which
reduces the pressure for reasons of safety, to the intermediate
system working pressure of 600-680 psig.
C_A_U_T_I_O_N_: DO NOT TIGHTEN THE FITTINGS AND CONNECTIONS MORE THAN
THE TORQUE WHICH IS PERMITTED. THIS CAN CAUSE DAMAGE
TO THESE PARTS.
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In the 5th picture of post #745, which shows the o2 tank valve imbedded into the cabin interior, does it not look like a transfer mark ( the green smear of paint) from the o2 bottle itself ?
It almost seems to me as if the o2 bottle came up through the cabin floor and struck the door handle and cabin interior, then sheared the valve and exited downward and out though the side of the aircraft.
However, the pictures of the cabin floor are not clear enough to lend further credibility to this idea.
What else could have left this green streak (smudge) on the cabin interior?
It almost seems to me as if the o2 bottle came up through the cabin floor and struck the door handle and cabin interior, then sheared the valve and exited downward and out though the side of the aircraft.
However, the pictures of the cabin floor are not clear enough to lend further credibility to this idea.
What else could have left this green streak (smudge) on the cabin interior?
Last edited by Rolling-Thunderbird; 31st Jul 2008 at 02:21. Reason: spelling
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At the bottom of that partition is a portable oxygen cylinder mounted at floor level at a 45deg angle. Had a look at another aircraft and the bottle is pointing exactly in line with the door handle.
The door handle which was hit by ?? would of tried to open but the upper and lower gate pushrods would of broken and this is why it looks like the door cracked oped during flight, but I think the gates are just hanging down because there is no pushrod to hold them closed. After the aircraft depressurized the upper gate is open more that the lower as you would expect, chk out that pic of the door upper gate. My thoughts only.
The door handle which was hit by ?? would of tried to open but the upper and lower gate pushrods would of broken and this is why it looks like the door cracked oped during flight, but I think the gates are just hanging down because there is no pushrod to hold them closed. After the aircraft depressurized the upper gate is open more that the lower as you would expect, chk out that pic of the door upper gate. My thoughts only.
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Am I imagining things, or is there another green streak on the lower portion of the door, opposite the one you're talking about? You might have to blow up the first photo in the series to see it. Looks like it's about a foot off the floor.
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Someone said the "regulator" shot through the cabin floor. Did they mean the regulator or the the valve at the top of the bottle?
The regulator is separate item on a "T" piece shown on the right hand side of my* picture in post #764 (i.e. the "T" piece is shown, not the regulator).
*NB: Picture not for media use.
The regulator is separate item on a "T" piece shown on the right hand side of my* picture in post #764 (i.e. the "T" piece is shown, not the regulator).
*NB: Picture not for media use.
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Rolling T-Bird -- good eye on the green stripe! The oxy cylinder valve knob is metal with a molded green plastic cover that could have left such a mark.
SUB -- in one photo (poor quality) of vestibule & door, the portable oxy bottle appears in its cubby in partition near floor but opposite angle you describe. May have been returned there post-descent.
NSEU -- from ATSB Media Release 2008/28: "The ATSB can confirm that it appears that part of an oxygen cylinder and valve entered the passenger cabin and impacted the number 2 right door frame handle..." [empahsis mine]
Mark in CA -- yes, could be a second green mark. Perhaps one was caused by the cylinder fragment and the other by the knob cover.
Anyone have a clear photo of the floor penetration? Lower half of door? Noddys Car? NSEU?
SUB -- in one photo (poor quality) of vestibule & door, the portable oxy bottle appears in its cubby in partition near floor but opposite angle you describe. May have been returned there post-descent.
NSEU -- from ATSB Media Release 2008/28: "The ATSB can confirm that it appears that part of an oxygen cylinder and valve entered the passenger cabin and impacted the number 2 right door frame handle..." [empahsis mine]
Mark in CA -- yes, could be a second green mark. Perhaps one was caused by the cylinder fragment and the other by the knob cover.
Anyone have a clear photo of the floor penetration? Lower half of door? Noddys Car? NSEU?
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Yesterday, 18:37 #773 (permalink)
SUB
The cables above the bottles I looked at the other day had lots of grease and were covered in thick dust.
SUB
The cables above the bottles I looked at the other day had lots of grease and were covered in thick dust.
Hypothetical question only here:
Let's say some new guy at Haeko decides he's going to help out and lube up those dry overhead control cables that he's spotted. All he can find is Lithium Grease. He really slops it on there and nobody knows he's done this.
On the next flight a big blob of this stuff drips/flakes off down and hits a leaking Valve/line/regulator.
Spontaneous Combustion possible?
Last edited by pacplyer; 31st Jul 2008 at 10:35. Reason: added quote