crew oxy pressure
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crew oxy pressure
hi there!i have a doubt...
you're at FL 410 and your estimated flight time will be 3 hours.
suddenly you check the crew oxygen pressure and read 0 psi.(zero).
what are you supposed to do, captain?
thanks!
you're at FL 410 and your estimated flight time will be 3 hours.
suddenly you check the crew oxygen pressure and read 0 psi.(zero).
what are you supposed to do, captain?
thanks!
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I'd descend to 310 for a start,once I.d established that there was no O2 in the tank(try the mask)..Call for a supplemental first aid bottle to the cockpit,consider a diversion if the 310 fuel inadequate..The TUC at 310 would be sufficient to do the descent and share the bottle...Your turn
cheers
I\'m not sure the QRH would cover the lack/loss of Crew O2,
but should cover depressurized flight dispatch limits..
cheers
I\'m not sure the QRH would cover the lack/loss of Crew O2,
but should cover depressurized flight dispatch limits..
Oldebloke,
This is an interesting question because I was thinking along similar lines of thought to yours. Upon reflection, It occured to me that since this may not be addressed by the flight manual or QRH, then it would be open to interpretation by all who learn of the occurance after the fact. Certainly, calling for the walk-around bottle is a good idea, but a descent to a more breathable altitude may be a good idea if the situation permits. Stopping at 310 to think things through is a wonderful idea. Terrain, weather below and flying time to a suitable alternate would have to be considered before deciding what is best to do. Continuance of the flight to destination at 310 would probably be questioned if suitable alternates are overflown though. In light of increased attention to crew O2 and it's probable role in two high profile crashes in recent years, It would be a challenging position to defend . Once safety has been satified, then the repercussions may be considered. How do you think the discussion might go?
Best regards,
Westhawk
This is an interesting question because I was thinking along similar lines of thought to yours. Upon reflection, It occured to me that since this may not be addressed by the flight manual or QRH, then it would be open to interpretation by all who learn of the occurance after the fact. Certainly, calling for the walk-around bottle is a good idea, but a descent to a more breathable altitude may be a good idea if the situation permits. Stopping at 310 to think things through is a wonderful idea. Terrain, weather below and flying time to a suitable alternate would have to be considered before deciding what is best to do. Continuance of the flight to destination at 310 would probably be questioned if suitable alternates are overflown though. In light of increased attention to crew O2 and it's probable role in two high profile crashes in recent years, It would be a challenging position to defend . Once safety has been satified, then the repercussions may be considered. How do you think the discussion might go?
Best regards,
Westhawk
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the 310 alt refence comes from the dispatch limits with one pack/bleed inop..Giving time to get down to 14000(should the other quit)..the first aid o2 would give the guys/girls air on the way down...I do think the industry will revamp the oxygen checks on the ground(walkaround)..
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The FL310 limitation is based on the ability of one a/c pack to pressurise the cabin. It assumes the pressure hull and pressurisation system is intact and fully functional. This scenario assumes the pressure hull, or pressurisation system, will become compromised, yet there is no suitable, approved back-up oxygen system for the flight deck crew.
Assume the worst case, as pilots are trained to do, which is a rapid decompression to FL310 in about 10 or so seconds. The pilot with the makeshift oxygen system will hopefully mask up. This takes a finite time using a system that is not “quick donning”. Even if he masks up in 10 seconds after the decompression the non-protected pilot has now used up a considerable portion of his time of useful consciousness, possibly all of it.
“A rapid decompression time (less than 20s) to a cabin altitude above 30,000 ft will produce a significant impairment of performance in those breathing air even if 100% oxygen is delivered to the respiratory tract immediately the decompression commences."[Aviation Medicine, 2nd Ed, Ernsting and King. My italics].
Based on this, the unprotected pilot will suffer some impairment of mental function. If, during the descent, the flying pilot with the makeshift oxygen system takes it off to share it with his colleague, then there is a real risk of two mentally impaired pilots carrying out an emergency descent and subsequent recovery and diversion.
A few more points. The gauge says the oxygen bottle is empty but you test it. You think you can feel oxygen being delivered. Do you really trust that system? Remember, if it’s really not your day your life may depend on it.
Flight plans in pressurised aircraft should take into account the occurrence of a depressurisation and subsequent flight at FL100. You should have enough fuel to divert somewhere at FL100, otherwise somebody’s going to be in big trouble if the authorities find out.
Why risk it? If walk around sets were suitable for this purpose then wouldn’t it be clearly stated in the MEL that they could be used in this way?
The flight crews’ lives are worth so much more than the simple A to B journey they were originally tasked to do. Their passengers’ safety and welfare is certainly worth more.
Descend out of hypoxia territory.
Divert if necessary.
Pour yourselves a well deserved drink for making a good, sensible, although perhaps boring decision.
You know it makes sense.
Assume the worst case, as pilots are trained to do, which is a rapid decompression to FL310 in about 10 or so seconds. The pilot with the makeshift oxygen system will hopefully mask up. This takes a finite time using a system that is not “quick donning”. Even if he masks up in 10 seconds after the decompression the non-protected pilot has now used up a considerable portion of his time of useful consciousness, possibly all of it.
“A rapid decompression time (less than 20s) to a cabin altitude above 30,000 ft will produce a significant impairment of performance in those breathing air even if 100% oxygen is delivered to the respiratory tract immediately the decompression commences."[Aviation Medicine, 2nd Ed, Ernsting and King. My italics].
Based on this, the unprotected pilot will suffer some impairment of mental function. If, during the descent, the flying pilot with the makeshift oxygen system takes it off to share it with his colleague, then there is a real risk of two mentally impaired pilots carrying out an emergency descent and subsequent recovery and diversion.
A few more points. The gauge says the oxygen bottle is empty but you test it. You think you can feel oxygen being delivered. Do you really trust that system? Remember, if it’s really not your day your life may depend on it.
Flight plans in pressurised aircraft should take into account the occurrence of a depressurisation and subsequent flight at FL100. You should have enough fuel to divert somewhere at FL100, otherwise somebody’s going to be in big trouble if the authorities find out.
Why risk it? If walk around sets were suitable for this purpose then wouldn’t it be clearly stated in the MEL that they could be used in this way?
The flight crews’ lives are worth so much more than the simple A to B journey they were originally tasked to do. Their passengers’ safety and welfare is certainly worth more.
Descend out of hypoxia territory.
Divert if necessary.
Pour yourselves a well deserved drink for making a good, sensible, although perhaps boring decision.
You know it makes sense.
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You know it makes sense.
PP
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I have had the crew oxygen supply drop to zero pressure, and opted to descend to 25000 feet. My reasoning then (and would still be) that TUC at 25000 feet is approximately 4 minutes, and an emergency descent to 10000 feet could be accomplished in 3 of those 4 minutes.
Whilst there may be debate upon my reasoning stated here, I think that there is no argument that a depressurisation at 41000 feet or even 31000 feet without oxygen being available would be CERTAIN death.
On the occasion that it happened to me we were fortunately operating a short 2 hour sector, and increased fuel useage was not a problem. There was sufficient fuel to continue to destination. Long sectors, e.g. trans Pacific, would cause a much greater fuel penalty, perhaps making it impossible to reach the destination, but bear in mind that we must always carry sufficient fuel to cover depressurisation at any point en-route, and a diversion to an en-route contingency airport may be necessary. (I do not refer to ETOPS operations here, but ALL operations).
In my mind, continued flight above 25000 feet without oxygen being available is a totally unacceptable risk, and a loss of crew oxygen warrants an immediate descent to a lower more suitable level.
Regards,
Old Smokey
Whilst there may be debate upon my reasoning stated here, I think that there is no argument that a depressurisation at 41000 feet or even 31000 feet without oxygen being available would be CERTAIN death.
On the occasion that it happened to me we were fortunately operating a short 2 hour sector, and increased fuel useage was not a problem. There was sufficient fuel to continue to destination. Long sectors, e.g. trans Pacific, would cause a much greater fuel penalty, perhaps making it impossible to reach the destination, but bear in mind that we must always carry sufficient fuel to cover depressurisation at any point en-route, and a diversion to an en-route contingency airport may be necessary. (I do not refer to ETOPS operations here, but ALL operations).
In my mind, continued flight above 25000 feet without oxygen being available is a totally unacceptable risk, and a loss of crew oxygen warrants an immediate descent to a lower more suitable level.
Regards,
Old Smokey
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The original question was what one would do ,if at 410,and the press' gauge read zero???I agree SRB that the political(sensible)correct answer would be Divert and Fix!!
The zero gauge press would force on to check the mask(inop gauge)at 100% flow one would get the 'breeze' flow??
As Smokey says the O2 rules are different at Fl250,and the TUC,ergo I would still consider 'salvaging' the flight,with the availabilty of supplemental O2..All one would have to do,in the worst case'structural'(explosive),would select Alt and Cruise change(Idle open for the Airbus)and suck on the bottle(Have one each)
As you put it ,one has to explain to the CP why one diverted because of a faulty gauge,or no Crew O2, which had been checked prior to the flight????(leaks happen)
It vaguely reminds me of the Asian Carrier that dumped fuel and returned to base because the captains windshield wiper flew off at top o'climb,and rainshowers were in the Destination Forecast.
The zero gauge press would force on to check the mask(inop gauge)at 100% flow one would get the 'breeze' flow??
As Smokey says the O2 rules are different at Fl250,and the TUC,ergo I would still consider 'salvaging' the flight,with the availabilty of supplemental O2..All one would have to do,in the worst case'structural'(explosive),would select Alt and Cruise change(Idle open for the Airbus)and suck on the bottle(Have one each)
As you put it ,one has to explain to the CP why one diverted because of a faulty gauge,or no Crew O2, which had been checked prior to the flight????(leaks happen)
It vaguely reminds me of the Asian Carrier that dumped fuel and returned to base because the captains windshield wiper flew off at top o'climb,and rainshowers were in the Destination Forecast.
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Boeing pilots have stated on this website how the oxygen bottle can be switched off yet residual pressure in the delivery lines can produce a convincing test of mask function. I tried a similar thing in an Airbus and the same happens. Conclusion: test the mask delivery system thoroughly, ie a good, long press-to-test to make sure there is a continuous supply of gas behind the lines.
Studies have shown that even mild levels of hypoxia will produce a degradation of a pilot’s performance some time after the event, even after descending out of hypoxia territory. (Pilots were made hypoxic and then put in the sim to carry out simulated diversions following a rapid decompression. More errors were made in the hypoxic group than a normal, control group. I can’t remember the reference to the paper - sorry). I wouldn’t even hang around at 25k, but maybe that’s just me.
Gauge failure or system failure? I don’t know and I don’t care above 25K. How do you feel if the fuel gauges drop to zero but the engines are still running? I may suspect the gauge but I also feel nervous. I cope with nerves better on the ground than I do at altitude, but maybe that’s just me.
The “rules” of O2 at FL 310 and FL250 are not different. It’s the hazards that are different. The hazards of crashing a car at 30 mph are different to crashing at 80 mph. The smart money, however, always remains on not being in a position to crash in the first place. It sounds so easy to slip on a mask, twiddle a knob here, pull another knob there and it’s home in time for tea and medals. Maybe it is that simple, on your day. Unfortunately there is well documented evidence of trained pilots attempting such “simple” actions yet still ending up unconscious. This suggests it is not always going to be your day.
I’m not preaching or being judgmental, just stating what I’d do and why, which is get down and get it checked over. Others obviously wouldn’t. Good luck to them - and their passengers.
Studies have shown that even mild levels of hypoxia will produce a degradation of a pilot’s performance some time after the event, even after descending out of hypoxia territory. (Pilots were made hypoxic and then put in the sim to carry out simulated diversions following a rapid decompression. More errors were made in the hypoxic group than a normal, control group. I can’t remember the reference to the paper - sorry). I wouldn’t even hang around at 25k, but maybe that’s just me.
Gauge failure or system failure? I don’t know and I don’t care above 25K. How do you feel if the fuel gauges drop to zero but the engines are still running? I may suspect the gauge but I also feel nervous. I cope with nerves better on the ground than I do at altitude, but maybe that’s just me.
The “rules” of O2 at FL 310 and FL250 are not different. It’s the hazards that are different. The hazards of crashing a car at 30 mph are different to crashing at 80 mph. The smart money, however, always remains on not being in a position to crash in the first place. It sounds so easy to slip on a mask, twiddle a knob here, pull another knob there and it’s home in time for tea and medals. Maybe it is that simple, on your day. Unfortunately there is well documented evidence of trained pilots attempting such “simple” actions yet still ending up unconscious. This suggests it is not always going to be your day.
I’m not preaching or being judgmental, just stating what I’d do and why, which is get down and get it checked over. Others obviously wouldn’t. Good luck to them - and their passengers.
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Hmmm, lets see.
FL410, and flight time remaining is three hours.
Not likely to be a long overwater flight where the departure weight was heavy, sounds more like a shorter sector, with suitable diversion alternates.
If it were me, descend to FL250, have the walk-around bottle available for the Commander, and divert as necessary.
FL310 would be out of the question, from my perspective.
Better safe than sorry.
FL410, and flight time remaining is three hours.
Not likely to be a long overwater flight where the departure weight was heavy, sounds more like a shorter sector, with suitable diversion alternates.
If it were me, descend to FL250, have the walk-around bottle available for the Commander, and divert as necessary.
FL310 would be out of the question, from my perspective.
Better safe than sorry.
Looking more carefully at the original scenario posed and considering the above posts along with a re-examination of the pertinent US regulations regarding crew O2 requirements, I believe that Old Smokey's and 411A's responses are closest to the mark if you indeed have good reason to believe O2 to be unavailable.
My view of this scenario would now go something like this:
Upon recognition of the zero pressure indication, and with normal pressurization function, an attempt to verify the indication should be accomplished. The method for this determination and the level of assurance resulting will vary according to specific aircraft type and O2 system installation. Assuming that O2 supply is determined to be in serious doubt, and that a descent to FL250 would not introduce increased risk, (wx, terrain, fuel range to suitable alternate) cruise descent to FL250 should be initiated after informing ATC of intentions and the reason, if required to expedite handling. Having the portable bottles ready to use is a good thought in case you are having a truly bad day. If sufficient fuel is available to continue to destination at FL250, great. If not, diversion would be appropriate. In either case, the route flown should be considered so as to allow for immediate descent to unpressurized breathable altitudes in case of pressurization malfunction.
Obviously, all possible contingencies cannot be accounted for ahead of time, but this would seem to me to be a sound basis for a strategy to address the scenario as originally posed by stumer. First, determination of a problem and it's safety implications are considered. Second, a plan of action is formulated and executed with safety as the prime goal. Third, once safety is satisfied, customer and company convenience may be considered where it does not conflict with safety or applicable regulations. Finally, once safely on the ground, the interview with the cheif pilot may be considered.
This has been an interesting thread because of the many constructive and thoughtful posts it contains. I'm glad to have the opportunity to work this through on PPRUNE in the safety of a hotel room before having to do it aloft under somewhat more demanding circumstances!
Best to all,
Westhawk
My view of this scenario would now go something like this:
Upon recognition of the zero pressure indication, and with normal pressurization function, an attempt to verify the indication should be accomplished. The method for this determination and the level of assurance resulting will vary according to specific aircraft type and O2 system installation. Assuming that O2 supply is determined to be in serious doubt, and that a descent to FL250 would not introduce increased risk, (wx, terrain, fuel range to suitable alternate) cruise descent to FL250 should be initiated after informing ATC of intentions and the reason, if required to expedite handling. Having the portable bottles ready to use is a good thought in case you are having a truly bad day. If sufficient fuel is available to continue to destination at FL250, great. If not, diversion would be appropriate. In either case, the route flown should be considered so as to allow for immediate descent to unpressurized breathable altitudes in case of pressurization malfunction.
Obviously, all possible contingencies cannot be accounted for ahead of time, but this would seem to me to be a sound basis for a strategy to address the scenario as originally posed by stumer. First, determination of a problem and it's safety implications are considered. Second, a plan of action is formulated and executed with safety as the prime goal. Third, once safety is satisfied, customer and company convenience may be considered where it does not conflict with safety or applicable regulations. Finally, once safely on the ground, the interview with the cheif pilot may be considered.
This has been an interesting thread because of the many constructive and thoughtful posts it contains. I'm glad to have the opportunity to work this through on PPRUNE in the safety of a hotel room before having to do it aloft under somewhat more demanding circumstances!
Best to all,
Westhawk
