Qantas flight QF568 loss of pressurization in cruise and diversion
 

https://www.qantasnewsroom.com.au/qa...-perth-sydney/


I can't find any info on what actually went wrong (did one or both packs fail?) but they got the packs working again at 10,000 feet

This is probably a non-event but some media have dramatized it :ugh:to the extent of saying that passengers were writing final letters to loved ones. Indeed one person fainted, but maybe because of (unfounded) anxiety.

Here is an example Woman faints and passengers scramble for oxygen masks as Qantas flight makes emergency landing | Daily Mail Online

I'm not too familiar with the Airbus systems, can the APU be used for pressurization in flight if both packs failed?

If both packs fail, it won’t matter what air sources are available, the packs that pressurize the plane have FAILED.

GF

Of course, my bad, didn't think of that. :ok:

After initial rapid descent to 10 they climbed again and did the last, slow 2 hours(ish) into Melbourne at 17,000 - says he scratching head.

What allows you to maintain an 8000 ft cabin but only up to 17000?
I thought that one pack could do better than that.

What does MEL say about departure on one pack?

I'll answer my own question.

Since masks had already dropped, not allowed above 17,000 (or whatever), even with packs running.

Knowing nothing of the aircraft systems of this aircraft, if it has a ram air intake, it might be able to hold some degree of cabin pressure above ambient.

You can go to Flight Level 250 without drop down masks.
I’m guessing they didn’t want to go too high in case the problem reoccurred. Just high enough to give them the range to reach Melbourne.

Hey all, might be able to provide some degree of insight, i was paxing on board.

As usual, media over-sensationalised the whole thing. Gradual decompression - felt my ears pop and noticed nearly immediately after that the exit signs lit up. I'm familiar with Airbus systems so this is when i knew we had decompressed. About 30s later felt the engines roll back and heard "Emergency Descent". Rubber jungle about another 90sec after the announcement. No shakes, shudders, sounds or smells. Just a standard descent with the boards out - as expected.

All ran rather well, crew followed procedure, pax were well informed, I managed to avoid the que for the service desk but ground staff seemed to be coping well. All in all a fairly tidy operation from what i could observe.

As for the Fault? No idea. We were only level for what felt like about 10-15min (wasn't timing so it could've been more) before climbing back up to FL170. Also looks like we had a fairly northern flight plan prior to the diversion too. May suggest a Non-ETOPS profile. Perhaps there was an MEL on one of the Eng Bleed's or a Pack Flow Control Valve. Both of which are non-ETOPS and supplying pressurisation with a single bleed source. Operating bleed fails, do the dive, fire up the APU and divert at a level below APU-Pack operating altitudes.

Can't say specifics for the A330 but it would fit the mould for my type. Obviously this is all speculative.

Sounds like an Engine 1+2 Bleed fault..

With APU providing Bleed air and unable to reset Eng bleeds max Alt is FL220.

It’s been known to happen.

Or one engine bleed and one pack fault, one of them already as MEL from the beginning. May have taken some time to sort out crossbleed or APU to restore pressurisation.

What is the SOP? Emergency descend first, troubleshooting second? How long does the APU take to start at cruising altitude?

Depends how quick you react to the Bleed trips and how quickly the cabin Alt climbs. APU would start within 1 min of being selected I’m sure, haven’t stated it in flight for a long time.

What is the purpose of the "Emergency Descent" PA?

I believe the “emergency descent” PA is for the benefit of the Cabin Crew. I.e so they know the flight crew are not incompacitated. Depending on company SOP, the cabin crew may attempt to enter the cockpit if the PA is not announced.

I was going to say the same thing but...

Unless the aircraft has a bypass system that allows bleed air to bypass both packs to keep the aircraft pressurized.

Jet Jock
 

A What!!??
Never heard of such a system, can you use an example?

Putting 250c hot air into the cabin and you just invented the pressure cooker , me thinks.

No packs, no pressure!

As fare as 17000 feet goes, is there mountains on the route? Or just ships!

Highest terrain in Aus is Mt. Kosciusko - only 7,300ft. The climb was likely made to conserve fuel.

Pack Failure
 

The 777 used to do this regularly. Apparently there was an Auto Slat command being fed into the Air Supply Cabin Pressure Controller and it shut of the packs in a way to preserve engine power as the A/C thought something really nasty was about to happen. Boeing sent out an alert which basically said not to worry if this happens for up to 60 (or 90?) seconds; this is perfectly normal and a known glitch....

IIRC, the BAE 125/800 had such a system and the aircraft I fly now, the Global Express, has an “Aux Press” switch that activates the emergency pressurization system who provides an alternate pressurization source for the cabin in the event of the loss of both cooling packs.

However, when the system is used under abnormal situations, you are limited to FL410 because anything above that may require the bleeds to switch over to the high mode creating too much heat.

Having worked for QF and now retired, as long as procedures haven’t changed, the PA was for crew and PAX as a backup to the recorded PA and to reassure them the pilots were carrying out the procedure.

Correct......Standard Airbus SOP