QF depressurisation event
 

Interestingly was only cruising at F250 at the time of descent!

Anybody got the rego? XZL was flying around single pack last week...

Thanks for that.

And of course, the pax were screaming, fretting, filming each other, and on the ground saying they would be reluctant to get on another flight.

Why can't the media explain to the punters that it was a non-event. After they have milked it for all it's worth, and just missed a school on short finals.

https://www.theguardian.com/business...t-to-melbourne

https://cimg7.ibsrv.net/gimg/pprune....ba81ce5254.jpg

Which one is the 737?

For an excellent example of sludge reporting, including two variations on the "plunge" word, and mandatory use of "terrified" this article set new standards:

https://www.dailymail.co.uk/news/art...lag5YZILMLHAVY

However the public can be assured with the following:

"Passenger planes losing pressure is not uncommon. Pilots are trained to descend to 10,000ft where the atmosphere has more oxygen so passengers can breathe better." :rolleyes:

"Flight QF706 landed safely in Melbourne at 8.02am after making ARBEY time 54.

Ok, so here’s a question or two for the Brains Trust.

I’m cognisant that deferring a defect under an MEL is perfectly legal. There is however a difference between ‘Legal’ and ‘Safe’. After all, just because its in the MEL, it doesn’t mean you have to fly, it means you can, if you decide its safe to do so.

All of this is typically covered in the MEL preamble and I’m not having a shot at the pilots here.

I would be curious to know how long a pack is deferrable for? The reason I ask is that, if you are flying around on one pack, and the other one fails, you are going to get the rubber jungle, an ASIR and some free media exposure. Its not a perhaps or a maybe. I’d suggest that something like a Pack should be deferred only until the aircraft stops at a maintenance base, but that’s a personal opinion.

How much does commercial pressure affect our good judgement? Do we need to modify our risk analysis? Instead of saying, “statistically, what are the chances the second pack will fail?”, should we be looking at the definite outcome when it does fail? Let’s face it, the MEL knows the second failure is possible because of the restriction to FL250 on one pack.

2 more points please:

Would this MEL item be part of the Threat and Error Management and therefore briefed to the Cabin Crew before flight? “We’re on one pack, if it fails there’ll be an Emergency Descent.”

If so, and this is an ethical and theoretical question that goes to Duty of Care, do you believe Passengers should be told before flight of the aircraft status and possible outcomes? I know this is a controversial question and impractical in the real world, but surely Pax have an expectation that their flight is as risk free as possible? I imagine if this were the case, the commercial pressure would shift from the pilots, to the company, as that’s not a conversation the Company would want to have. Surely, that’s a good thing?

Depends greatly on the form the pack failure takes. Depending on that form, and the crews awareness/attentiveness, an emergency descent is not inevitable at all. A managed descent is quite possible. n Let me add another variable if you like. Cruising at 380, 1 pack from 2 fails. Perfectly OK to remain at 380 if I like. 1 pack. How does that change things? Discuss.

Welcome to the quagmire that is aviation. Reality is that flying involves risk. How much risk are you prepared to take is the question.

Most of your questions are only going to be answered definitively if either:

1. A passenger sues an airline or captain even though they followed manufacturer's approved procedures
or
2. A pilot refuses to fly an aircraft with a particular MEL applied and is fired and then claims unfair dismissal and tests it in court.

Until either those happen I would suggest we will never have an answer.

I no longer have access to the MMEL to give a definitive answer to the question, but everything in the MMEL (Master MEL - published by the airframer - operators can go more conservative than the MMEL, but not more liberal) has been statistically analyzed and approved by the regulators.
My best guess is 3 days, but that's just an educated guess.

10 days or 240 hrs.

Hmm. What's the maximum altitude after one of two serviceable packs fails (or is turned off under a QRH procedure) in flight?

As far as the 737 is concerned, it's good up to certified ceiling, according to Boeing. (FL 410) Subject to some caveats, of course. Not that I would necessarily advocate same......

Just to clarify, on the 737 the FL250 limit is at the planning stage only. (MEL) Not a requirement after dispatch.

ALL MEL's have two meanings. one at the planning stage & another when airborne!

Its not a certainty.

I am reliably informed that there was a time in the recent past when a certain airline in Oz had four A380s each with one pack inop, leaving one working. This went on for several weeks coz it is a major job to replace a pack even if you have the spares, which they didn't.
Trust the statistics, you'll get away with it!

Bootstrap 1,
That's what I also heard. If the parts become available the ground time needs to be also there and then we need at least 2 crews for, as I am told, about 24 hours to do each aircraft.
Still, it was eventually done and they got away with it. Think of the hours saved on the a/c packs coz they weren't fitted - a big saving of component hours. My friends used to tear their hair out, now they just shrug.

What I don't understand is, how come CASA haven't already bypassed legislation and issued a directive to say that no RPT operation is to commence unless that acft has three packs installed (the third one being for an extra level of redundancy), and that no flight is to operate if any one of those three packs are unserviceable ('cos there is always the possibility of a double pack failure). After all, safety is number one.

I wouldn't be surprised if there is a tad more redundancy within the 380 pack system than that of the 737.

The question I'm left with though, is why did they end up with a rubber jungle. The aircraft cabin altitude shouldn't climb all that rapidly in the case of a second pack failure, so why didn't they beat it down?

Depressurisation event
 

Why limit it to A/C packs? MEL operation is all about operating with reduced redundancy.
So simply ban all MEL operation for Australian based operators. Simples.
Of course, within 12 months there would no longer be any Oz based operators, but what the heck...

Packs are normally extremely reliable - maybe it's time to look at how the packs are being maintained/overhauled if they are failing at that rate. I don't see anyone else having these issues with the packs.

Maybe even a depressurisation Non-Event.

Ah, if you look at an MEL, you'll find a number of systems where "Number installed" is 2, "Number required" is 1 (sometimes zero). MEL operation, pretty much by definition, means reduced safety relative to a full up aircraft. The effect on safety is very, very small (assuming the MEL limitations are observed), but if you're going to take Dick Smith's position of absolute safety regardless of cost, you need to ban MEL operation.
Or you can live in the real world.