Incident on QF706 ADL to CBR

[33kft]

This is probably the most vivid description of a first person inflight incident I've ever read, and I like reading about aviation, so I've certainly tried to digest as much as I can. Thanks! Sorry you had to go through it. From what you have described, the crew did about as well as you could expect in that sort of situation.

 

[Antoallison]

So I have to explain the event a bit. Picture this:

it is 7'somethng oclock, you have been up since 4. Just getting into the swing of the day,.Coffee in your tray, OK ham and cheese toastie in your mouth. Orange tints in a black sky. Cabin crew are attentive and delightful All is serene and peaceful. Takeoff was normal. Air is clean and fresh, Will be a good day

Look out the window. World in tilted. Listen. Change of engine pitch. Now I see we are nosing down. Not normal
This goes on for 15-30 secs before...

1 and 2) when the oxy masks dropped, it was accompanied by a calm, stern, male voice LOUDLY saying "This is an emergency. You are required at this time to breathe oxygen. Pull the mask down. Strap it onto your face. Stay in your seat." Over and over again. It was surreal. The female passenger next to me gasped and grabbed my hand. The lady behind me was clearing going to hyperventilate. BUT to me - the direction was clear from the voice - and I followed it.

3 and 4 ) I did not pull at all. Too panicked to. So a slight smell,but not unpleasant, not plasticy. If there is a chemical reaction on pull mine would not have worked, so I dispute that.

5) Mouth and nose. Allowed air in at the sides. A solid yellow cup not flexible. I forgot to tighten my strap but it stayed on (over my ears) I assume at "bad" altitudes it might suck to your face?

6) No.EVERYONE put it on.

7) bag did not inflate. When you breathe in, the bag makes a kind of bubbling noise/feel, like blowing out of a straw into a drink.

8) No (I assume the depressurisation was a slow leak). I did not hear a bang either

9) Obviously the recorded message stopped. The Captain announced simply "We are now at a safe level. You may remove your mask and breathe normally. There is a problem with the aircraft, we are diverting to Melbourne. Cabin crew, continue follow-on duties". I am pretty sure it was in that order. "Follow-on duties" I didn't understand at the time, however crew got out of their seats, went to the tail and moved forward (facing the tail) asking for a thumbs up from each passenger as they travelled up the aisle towards the nose.

10) wow you must have seen it in a dream. So JUST BEFORE the masks dropped there were two signals within 5 seconds of each other. Seatbelt was the first, the second I can't account for, but might have been warning to crew re masks coming down. There was a 5 -10 sec delay between last signal and masks dropping. I never saw/heard the signals cleared

11) Crew found the closest seat, buckled in and put on a mask. No fuss. There were some people in mild distress, but they didn't acknowledge them at this time. It was kinda everyone for themselves at this point.

12) Each seat set either side of the gangway had one extra maxk (i.e.4 for 3 seats)

13) There was a delay after landing before we were allowed to disembark. Captain simply said " Wait until we are given the all clear to disembark from ground (crew)". No "Welcome to Melbourne, local time is...", no disembarkation music, etc
We simply got off. Crew smiled but said nothing. My wife asked me if we all clapped and cheered when we finally made it to the gate. We did not.

However, when we reached the building (over the skybridge), some people simply collapsed and/or cried from the stress of it.

What an awful experience. I am sure the aftermath of that experience and holding all that tension affected many of the passengers on the flight for some time afterwards. Were there airline staff in the airport to assist the passengers or did they just collect their bags and wander off ?

 

[panpan]

Cabin crew were awesome - but frankly I never want to meet them again and I somehow feel they probably don't want to see me again either.
You could see in their eyes that they did not want to be the first Qantas statistics.They were completely professional and followed their training to the letter, as a team. They will be commended I am sure.

However I would get on any flight any time again to shake the hand of the aircrew. I guess because I only heard the Captain's voice, never saw the fear in his eyes my feeling towards them is different. I know they would have been seriously busy in the coughpit and some passengers did complain afterwards that they did not know what was happening in a blow-by-blow sense, but they had a serious job to do and their response was exemplary.I cannot fault it, and believe me I have relived it a number of times now.

 

[panpan]

Once we got off, the two-person gate crew handled it well. They asked everyone to stay at the gate while they rebooked us on to Canberra. There was an respectful sense of "Sorry for the delay" and no "OMG you poor souls", so we all just got on with it.
They wrestled with their (single) terminal at the gate for a while and then moved most of us to a customer point, where there were two more terminals. Everyone got Qantas lounge access. Cabin crew assisted the 2-3 that were in distress away from the main group. I left to go to the lounge after 15 min or so so not sure what happened after that.
For the record, I got straight on the 09:10 back to Adelaide. Wanted to see my wife.

 

[juddles]

Awesome to hear your experiences panpan. Thank you

 

[RooFlyer]

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.

 

[RooFlyer]

10) wow you must have seen it in a dream. So JUST BEFORE the masks dropped there were two signals within 5 seconds of each other. Seatbelt was the first, the second I can't account for, but might have been warning to crew re masks coming down. There was a 5 -10 sec delay between last signal and masks dropping. I never saw/heard the signals cleared

That one I found interesting. I wonder if the first two signals were related to the mask drop? I can't imagine there would need to be a delay between any of them, or of so, only momentarily. Maybe the Capt decided on the seat belt sign coincidentally just before whatever triggered the masks?

 

[Quickstatus]

I’m thinking differently.
If indeed the flight had one inop aircon pa k and therefore flew loweras suggested, a 2nd inop pack unable to overcome the usual air leak, the pilots would have seen it first. I doubt the pilots were fearful because this is a known “nothing to see here” problem.

The descent started without fanfare, maybe the pilots thought they could beat the auto deploy.

Note: the emergency descent does not involve increasing engine power - it’s a glide down with idle power with speed brakes. Hence it’s not a dive with that weightless feeling you feel on a roller coaster or turbulence

Maybe the seatbelt sign was triggered to get passengers back to seats whether triggered by an algorithm or pilots in case they could not beat the auto deploy

There is no rush to deploy too early, and you don’t want to, because there is only a limited supply of chemical per mask that produces O2 - maybe only 10min.

 

[RooFlyer]

If indeed the flight had one inop aircon pa k and therefore flew loweras suggested, a 2nd inop pack unable to overcome the usual air leak, the pilots would have seen it first. I doubt the pilots were fearful because this is a known “nothing to see here” problem.

The descent started without fanfare, maybe the pilots thought they could beat the auto deploy.

That sounds sensible.

There is no rush to deploy too early, and you don’t want to, because there is only a limited supply of chemical per mask that produces O2 - maybe only 10min

One would think (or I would - but I wouldn't know! ), limited supply or not, you'd deploy them at the max height (least available oxygen), but as you indicate, if it wasn't an instantaneous event, then the 'delayed' deployment is more understandable.

 

[Quickstatus]

Yes it deploys at 13000ft cabin altitude irrespective of what the outside altitude is. There is no point of deploying anything if outside is 25000 ft and inside is still 9000 ft and rising.

While there is great individual variability, the time of useful consciousness (to be cognitively functional) is about10- 20min at 18000ft if I recall correctly

It matters little if O2 masks deploy early if the pilot does not descend. (Helios, ?MH370?, Payne Stewart)

 

[Pushka]

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.

And obviously I totally agree.

@panpan - wow, Thankyou for your detailed review of what exactly happened and your experience as a technical person (the clear details) as well as an understanding of a layman’s emotional response to this.

And just as well this didn’t happen after the recent Ethiopian tragedy.

 

[jb747]

Look out the window. World in tilted. Listen. Change of engine pitch. Now I see we are nosing down. Not normal
This goes on for 15-30 secs before...

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.

1 and 2) when the oxy masks dropped, it was accompanied by a calm, stern, male voice LOUDLY saying "This is an emergency. You are required at this time to breathe oxygen. Pull the mask down. Strap it onto your face. Stay in your seat." Over and over again. It was surreal. The female passenger next to me gasped and grabbed my hand. The lady behind me was clearing going to hyperventilate. BUT to me - the direction was clear from the voice - and I followed it.

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

3 and 4 ) I did not pull at all. Too panicked to. So a slight smell,but not unpleasant, not plasticy. If there is a chemical reaction on pull mine would not have worked, so I dispute that.

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.

5) Mouth and nose. Allowed air in at the sides. A solid yellow cup not flexible. I forgot to tighten my strap but it stayed on (over my ears) I assume at "bad" altitudes it might suck to your face?

They never seal and it doesn’t matter.

7) bag did not inflate. When you breathe in, the bag makes a kind of bubbling noise/feel, like blowing out of a straw into a drink.

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

8) No (I assume the depressurisation was a slow leak). I did not hear a bang either

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.

9) Obviously the recorded message stopped. The Captain announced simply "We are now at a safe level. You may remove your mask and breathe normally. There is a problem with the aircraft, we are diverting to Melbourne. Cabin crew, continue follow-on duties". I am pretty sure it was in that order. "Follow-on duties" I didn't understand at the time, however crew got out of their seats, went to the tail and moved forward (facing the tail) asking for a thumbs up from each passenger as they travelled up the aisle towards the nose.

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.

10) wow you must have seen it in a dream. So JUST BEFORE the masks dropped there were two signals within 5 seconds of each other. Seatbelt was the first, the second I can't account for, but might have been warning to crew re masks coming down. There was a 5 -10 sec delay between last signal and masks dropping. I never saw/heard the signals cleared.

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

11) Crew found the closest seat, buckled in and put on a mask. No fuss. There were some people in mild distress, but they didn't acknowledge them at this time. It was kinda everyone for themselves at this point.

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

 

[jb747]

Are there any high altitude routes without immediate descent capability?

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.

Is decompression (and therefore lower altitude flying) factored into ETOPS certification or fuel required to alternate?

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.

Is there a way of opening the O2 drop doors if one fails to open

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

Yes it deploys at 13000ft cabin altitude irrespective of what the outside altitude is. There is no point of deploying anything if outside is 25000 ft and inside is still 9000 ft and rising.

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.

 

[Captain Halliday]

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

If they don’t inflate, and they just confuse people, what’s the point of them? Why not just the hose through which the O2 flows?

 

[Quickstatus]

If they don’t inflate, and they just confuse people, what’s the point of them? Why not just the hose through which the O2 flows?

The supplemental O2 delivery via the dropdown masks are continuous flow. However humans breathe intermittently. So the bag acts as a reservoir in between inspiration and may fill with O2 - its just an extra way of collecting O2 in between respirations. That it does not fill up is not an issue but if it does fill its better than not having one.

I dont have any data on the flow rate and concentration of the O2 coming out of the tubes. But lets do some sums:

Lets say an adult male (as defined by the airlines as usually weighing 80kg).
The normal inspiratory volume at rest is about 800ml (10ml/kg) and which takes say 1 second to inspire.
So the flow rate through the nose is about 800ml/sec but so as to ensure every breath is supplied it will need to be 48 litres/min

To match the inspiration 737 passenger supplemental oxygen supply need to supply over its 12 minute life, 576 litres. This is a lot of volume - approximately the amount of volume in a hospital "CD" oxygen cylinder which weighs about 4.5kg and is 0.5m long, 100cm diameter and pressurised to 2200psi - thats one tank per passenger plus an extra per row of 3 passengers.

I don't have the data for the chemical drop down O2 masks, but I don't think it is capable of that.

What all that means is that if the supplied O2 concentration is 100% and the supply rate matches the inspiratory rate, the inspired oxygen concentration will be same as the supply.

However, if the O2 supply rate is maxes out at 50% of the inspiratory rate, the inspired O2 will be a combination of 50% of the supplied 100% O2 and 50% of the ambient air which has 21% O2 (assuming the masks are not a tight fit). So the overall O2 concentration will be 35.5%

So anything that "reservoirs" the O2 in between inspirations will only increase the actual inspired O2 concentration - hence the bags.
And the masks cannot be a tight seal because it is impossible to match the inspiratory rate of anxious passengers who may actually hyperventilate. Better for them to breathe a mix of supplied Oxygen and cabin air than to feel they cant get enough volume through a tight fitting mask.

While hyperventilation (breathing faster and more deeply - which is what anxious passengers tend to do) will actually improve overall oxygenation; in a continuous supply supplemental O2 system, it is better to breathe normally.

I believe pilot O2 supply is demand driven. This means O2 is supplied only when the person inspires, and this method is able to supply much higher concentrations of O2 while conserving O2 supply. So the pilots gets more oxygen than the passenger/cabin crew. Which is a good thing

I read somewhere a long while ago (but cant find it) that the pilots can select O2/air mix, 100% oxygen demand flow, or 100% oxygen pressurised continuous flow (which is for emergencies like an explosive decompression at 40000 ft) on their system

Why the 12 minutes - I dont know but I speculate thats how long it will take to descend to 10000 from 40000 plus a little margin?. QF30 took 6 min to go from 26000ft to 8000 ft cabin altitude

 

[Himeno]

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

In 2007, I was on a QF74 departing SFO. There was a more bumpy then normal take off and the panel above my seat came partly loose. When a crew member noticed, they just hit the panel with their hand and it clicked back into place.

 

[drron]

Boy Quickstatus that sounds like a surgeons explanation of O2 delivery.
You do not need to inspire anywhere near 100% O2.In fact to do so will put some people at serious risk from CO2 narcosis.

 

[Quickstatus]

Yes the 100% was just for the purposes of the calculation.
Surgeon's calculation?. Needs to be more simple for surgeons
A standard hospital oxygen mask is capable of only about 35% which is more than enough in most cases.

 

[AviatorInsight]

I believe pilot O2 supply is demand driven. This means O2 is supplied only when the person inspires, and this method is able to supply much higher concentrations of O2 while conserving O2 supply. So the pilots gets more oxygen than the passenger/cabin crew. Which is a good thing

I read somewhere a long while ago (but cant find it) that the pilots can select O2/air mix, 100% oxygen demand flow, or 100% oxygen pressurised continuous flow (which is for emergencies like an explosive decompression at 40000 ft) on their system

Why the 12 minutes - I dont know but I speculate thats how long it will take to descend to 10000 from 40000 plus a little margin?. QF30 took 7 minutes to go from 29000 to 10000ft

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.

 

[Quickstatus]

@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?