Incident on QF706 ADL to CBR

[panpan]

When things are happening, there is a time warp between the coughpit and the cabin. Things that take minutes in the cabin, take seconds in the coughpit.

The time needed for the pitch change from cruise to descent would be about 2-3 seconds.



An automated PA, as well as automatic illumination of the signs and the cabin lights to full bright goes with the mask activation.



The gaseous systems will give you ZERO oxygen if you don’t pull the mask. It will drop about another 30 cms after being pulled. It removes a pin from the overhead attachment, which can allow it to be put back in some cases. The force required iIn not great, but you will feel it release. The chemical systems will give oxygen as long as someone at that station has pulled their pin. Pulling it down will give you more hose, and make the reach better. If nobody has pulled, again, ZERO oxygen.



They never seal and it doesn’t matter.



They are not meant to inflate, though to be honest all that does is confuse people.



There isn’t any reason for there to have been a bang, even though it was reported. The pack turned itself off for some reason...that’s just some valves closing.



Pretty unlikely to be any more chatty PAs. That’s a standardised PA, post depressurisation. Follow up duties tell the cabin crew that they can come off the oxygen, and to sort out passenger and cabin issues.



Seat belts and no smoking manual selection. They also come on automatically with the masks, but do so simultaneously.



Normal, the crew can’t do anything until they hear that ‘follow up duties’ call.

Wow, you know your stuff @jb747. Thats really reassuring

 

[Quickstatus]

3 and 4 ) I did not pull at all. Too panicked to.

So that meant you were breathing only cabin air. Though if you were able to put it on your face, you most likely did "pulled" it even if you think you didnt...

Did you experience any of: lightheadedness, dizziness, blurred vision, headache, nausea?

Mrs Quckstatus fear of pulling on the O2 mask is that in the heat of the moment she would pull the hose off its connection point.

 

[panpan]

Thank you for that @panpan and welcome to AFF. An amazing debut!

I think your experience and description completely validates the opinion of mine and others here that what experienced aircrew might describe as 'nothing to see here, all in a days work' can be a horrific event for passengers.

For me, I think it would be a fear of what would happen next because of some unknown possible fundamental problem with the aircraft.

Thanks again.

Exactly. You try to rationalise it. but I have seen the docos and seen the news stories. I was waiting for a bulkhead to fail and take off the tail. Or the fuselage to open like a tin can and suck me out, still in my seat. I knew I wouldn't go cleanly - I knew I would hit something on the way trhoguh and had the vision of being maimed and in pain at -40 degC with no oxygen travelling through the air at 800kph.
That's what I was waiting for.
And you know you're thought process at that point? it is:
I hope its quick

 

[panpan]

So that meant you were breathing only cabin air. Though if you were able to put it on your face, you most likely did "pulled" it even if you think you didnt...

Did you experience any of: lightheadedness, dizziness, blurred vision, headache, nausea?

Mrs Quckstatus fear of pulling on the O2 mask is that in the heat of the moment she would pull the hose off its connection point.

Yes to momentary lightheadedness. Like you have just been spun around. But what @jb747 said has me thinking. Perhaps I never got oxy - as I didn't pull?
All I can say is that EVERYONE had a mask and I assume there were a good number of hard pulls in amongst the frightened passengers. No-one pulled it out., so rest easy, Mrs Quckstatus.

 

[panpan]

There are many routes where you will not be able to get down to 10,000. They will have some form of ‘escape’ route, that will be available (and which we used to program into the FMCs as secondary routes). The escape route will get to either somewhere you can land, or to a track where you can descend, but they will not necessarily immediately get you all that low. You may have to remain at 18-22,000’ for a while. The were most common on the Hong Kong to UK flights over China, and also Afghanistan.



No, engine failure and loss of an engine are considered separately. Combining the two, at the wrong part of oceanic flight could well have you going for a swim. The only alternative, is to descend to about 20,000, and to live with whatever happens re the oxygen. The Southwest, engine plus window loss scenario, is not planned or catered for.



Yes. There is a tool that the cabin crew use, but I suspect it could be done with a pen. Never tried.



This is what I’m bemused by, in this incident. The should be a number of minutes between the pack failing, and the cabin reaching the auto deploy height (which I think is 13,800’). The time available for the descent should have precluded the need for the masks. But, from what we’re hearing here, the masks actually deployed right at the start of the descent. So...either the descent was not entered promptly after the pack shutdown, or the cabin climbed unreasonably fast (which is pretty much impossible without structural issues), or, the masks were accidentally deployed at the start of the descent instead of waiting to try to beat the automatic deployment.

You don’t need to deploy the masks at 10,000. You can wait for 13-14.

From the passenger perspective, there wouldn’t have been any real difference between a necessary or unnecessary deployment. We would need to know the cabin altitude profile to know for sure.

Yes masks 30 seconds into the descent, max. There is one more possibility and that is that the aircrew did it themselves to protect the passenger's safety. That is what I like to think.
I guess they fly with the cabin crew a lot and knew they could handle any situation. I like to believe that the crew on that aircraft were at the top of their game and made the best decision for us, not the airline. Just sayin'

 

[Quickstatus]

Yes masks 30 seconds into the descent, max. There is one more possibility and that is that the aircrew did it themselves to protect the passenger's safety. That is what I like to think.
I guess they fly with the cabin crew a lot and knew they could handle any situation. I like to believe that the crew on that aircraft were at the top of their game and made the best decision for us, not the airline. Just sayin'

One of the scenarios pilots and cabin crew regularly train for...

Interestingly ATSB has not yet opened an investigation.

 

[Quickstatus]

Yes to momentary lightheadedness. Like you have just been spun around. But what @jb747 said has me thinking. Perhaps I never got oxy - as I didn't pull?
All I can say is that EVERYONE had a mask and I assume there were a good number of hard pulls in amongst the frightened passengers. No-one pulled it out., so rest easy, Mrs Quckstatus.

Maybe you didn't if the lightheadedness is anything to go by, especially if the masks were released early. In any case its momentary because time of useful consciousness at 18000 feet is about 20 minutes. Sounds like you retained all your neurons

So take home message for all of us (me included) who think we know the safety briefing verbatim. In an emergency your cognitive ability suddenly deteriorates. Pull that Mask!!

 

[panpan]

LOL yes

I also forgot to tighten the strap - duh

I think I was consumed with worrying whether to swallow my toastie bite or not...strange what you think of

 

[drron]

We have 3 settings. Normal, 100% and emergency. Normals is a mixture of o2 and ambient air, 100% is exactly that. 100% oxygen on demand (sounding like Darth Vader) and is our default setting, and emergency is a positive pressure of o2 being continuously supplied. We usually use that setting to purge the mask from fogging up or to remove smoke etc.

The 12minutes is exactly that. Enough time to get down to a more breathable level.

.

Now you have wandered onto medical grounds.
Yes the O2 being delivered to the mask may be 100% but not the air you are breathing.If the mask is airtight you are still breathing a mixture of the O2 and the air you breathe out which still has an awful lot of nitrogen.
If the mask is loose or has holes you will be breathing a mixture of O2 and air.The % of O2 in what you breathe will depend on the volume of your respiration.If breathing up the O2 concentration will be lower.

 

[Quickstatus]

.

Now you have wandered onto medical grounds.
Yes the O2 being delivered to the mask may be 100% but not the air you are breathing.If the mask is airtight you are still breathing a mixture of the O2 and the air you breathe out which still has an awful lot of nitrogen.
If the mask is loose or has holes you will be breathing a mixture of O2 and air.The % of O2 in what you breathe will depend on the volume of your respiration.If breathing up the O2 concentration will be lower.

Yes,
The amount of “dead space” will be higher with the demand triggered setting compares with the emergency pressurised continuous flow setting

In the former the small amount of exhaled gas remains in the mask (assuming air tight mask) which is then re-inhaled along with demand triggered O2. In the latter the pressurised continuous flow blows away the exhaled gas.

Presumably there is a blow off valve in the mask which limits the pressure buildup in case of the 3rd (emergency) setting and the mask is a tight enough fit so that negative pressure from inspiration will trigger the demand flow in the middle setting.

Re passenger masks. It’s a loose fit but when it’s too loose a lot of the supplied O2 just leaks away further away from the face and so the proportion of supplied O2 inspired is lower than if the mask was closely fitted to the face

In any case it’s better to make the safety briefing a memory item so that in an emergency it is “routine “

 

[Quickstatus]

LOL yes

I also forgot to tighten the strap - duh

I think I was consumed with worrying whether to swallow my toastie bite or not...strange what you think of

Were you in J?. I can only imagine what other important considerations a J passenger would have to deal with

 

[AviatorInsight]

.

Now you have wandered onto medical grounds.
Yes the O2 being delivered to the mask may be 100% but not the air you are breathing.If the mask is airtight you are still breathing a mixture of the O2 and the air you breathe out which still has an awful lot of nitrogen.
If the mask is loose or has holes you will be breathing a mixture of O2 and air.The % of O2 in what you breathe will depend on the volume of your respiration.If breathing up the O2 concentration will be lower.

You may be right, but all I care about is what setting is it on for what I need. 100% from the bottle on demand (whenever I breathe in) and emergency (continuous from the bottle) to purge anything I don’t want in there. The masks we have encompass the entire face and is fitted with tubing filled with air pulling the mask onto the face.

 

[AviatorInsight]

@AviatorInsight
Are pilot oxygen masks a complete/ air tight seal around the face?
Is the O2 demand valve easy to trigger?
How do pilots communicate with face masks on?

1. Yes they are
2. Very easy. Sits like a fighter pilot’s mask and we move the valve left or right of centre depending on what you want/need.
3. Very hard, but through the mask. You sound like Darth Vader.

 

[tgh]

This interesting conversation leads me to ponder duty of care matters.
Does the safety briefing that we all listen to carefully each time we fly .. sufficiently educate the imperative of correct mask utilisation.
If someone of marginal health ( or indeed robust health) suffered a mishap due to not correctly fitting and operating the mask in a timely manner… would the airline be liable ?

 

[Quickstatus]

This interesting conversation leads me to ponder duty of care matters.
Does the safety briefing that we all listen to carefully each time we fly .. sufficiently educate the imperative of correct mask utilisation.
If someone of marginal health ( or indeed robust health) suffered a mishap due to not correctly fitting and operating the mask in a timely manner… would the airline be liable ?

I suspect anything like that would come under "Conditions of Carriage". which also may or may not include any Convention (which defines airline liability) that the airline is a signatory to. (such as The Montreal Convention 1999)

 

[jb747]

Maybe you didn't if the lightheadedness is anything to go by, especially if the masks were released early. In any case its momentary because time of useful consciousness at 18000 feet is about 20 minutes. Sounds like you retained all your neurons

So take home message for all of us (me included) who think we know the safety briefing verbatim. In an emergency your cognitive ability suddenly deteriorates. Pull that Mask!!

I very much doubt that the cabin got all that high. I would certainly love to know. My sources aren’t quite what they were, but I’ll see if any of my mates know.

I also forgot to tighten the strap - duh

You have a couple of hands. They work perfectly well, and holding the mask gives you something to do.

The pilots masks are complex, and have valves on the mask involved in inhaling and exhaling, as well as a large external regulator. They seal tightly, and leave lovely welts on your face if you wear them for long enough. At the 100% setting, there is some residual exhaled breath, but as there’s a valve releasing it, not a mask full. At the emergency setting, the flow is constant and under pressure. In civil use that’s mostly for venting into the smoke goggle component of the mask, but it does give some level of pressure breathing. Military masks are worn very tightly, and can provide real pressure breathing...which is extremely uncomfortable and tiring. They also don’t normally use any cabin air, as fighter aircraft pressurisation system don’t bother keeping the cabin below 10,000’. They often work to half the actual altitude, so taking the mask off in normal flight would be dangerous.

You’re unlikely to pull the mask off. I know of 365 people who tried, and it just didn’t happen.

 

[jb747]

Yes masks 30 seconds into the descent, max. There is one more possibility and that is that the aircrew did it themselves to protect the passenger's safety. That is what I like to think.

The crew should not manually release the masks unless they are necessary. Once the cabin exceeds the automatic release level, they should be manually selected as a backup to the automatic system. Releasing them early is a screw up. It does nothing for the passenger safety, and increases levels of anxiety.

I guess they fly with the cabin crew a lot and knew they could handle any situation. I like to believe that the crew on that aircraft were at the top of their game and made the best decision for us, not the airline. Just sayin'

It’s just as likely that the crew had never met before. Certainly you never fly with anyone ‘a lot’.

 

[jb747]

This interesting conversation leads me to ponder duty of care matters.
Does the safety briefing that we all listen to carefully each time we fly .. sufficiently educate the imperative of correct mask utilisation.
If someone of marginal health ( or indeed robust health) suffered a mishap due to not correctly fitting and operating the mask in a timely manner… would the airline be liable ?

Look around. Most people don’t listen at all. And sadly the airlines aren’t helping by making them nice marketing driven buzz pieces. You need one written by a pilot. Including phrases like ‘you will die’.

 

[Quickstatus]

I very much doubt that the cabin got all that high. I would certainly love to know. My sources aren’t quite what they were, but I’ll see if any of my mates know.

Agreed, my reading suggests that a "slow" leak compared with an explosive leak afford the affected person some extra time before unconsciousness.

You have a couple of hands. They work perfectly well, and holding the mask gives you something to do.

Even though the arms are still connected to the brain, a lot of people - even those who are at the top of their cognitive ability, suffer the problem of a mushy brain when an emergency occurs. Its also what happens when you are "put on the spot" - like stagefright.

pilots masks are complex, and have valves on the mask involved in inhaling and exhaling, as well as a large external regulator. They seal tightly, and leave lovely welts on your face if you wear them for long enough. At the 100% setting, there is some residual exhaled breath, but as there’s a valve releasing it, not a mask full. At the emergency setting, the flow is constant and under pressure. In civil use that’s mostly for venting into the smoke goggle component of the mask, but it does give some level of pressure breathing. Military masks are worn very tightly, and can provide real pressure breathing...which is extremely uncomfortable and tiring. They also don’t normally use any cabin air, as fighter aircraft pressurisation system don’t bother keeping the cabin below 10,000’. They often work to half the actual altitude, so taking the mask off in normal flight would be dangerous.

You’re unlikely to pull the mask off. I know of 365 people who tried, and it just didn’t happen.

Thats a lot of O2, breathing 100%

 

[flyer89]

Military masks are worn very tightly, and can provide real pressure breathing...which is extremely uncomfortable and tiring.

This is interesting and not something I’ve ever thought about having not lived in the military world.

Subjectively, does it feel like great strain is being put on your lungs?