The FR24 appreciation thread

[Captain Halliday]

Some sort of issue on QF1871 TSV-BNE

The descent indicates it could be pressurisation.



Same flight number had an issue in June at almost the same point in the flight.

Different airframe in that occasion.

Issue on QF1871 TSV-BNE

Possibly pressurisation given the descent.
View attachment 399154

 

[mysticgreg]

As someone catching an Embraer from MEL to TSV and back this week... yay? :|

 

[VPS]

As someone catching an Embraer from MEL to TSV and back this week... yay? :|

Welcome to AFF - took a while for your first post

 

[jb747]

Some sort of issue on QF1871 TSV-BNE

The descent indicates it could be pressurisation.

Just because they’re descending rapidly doesn’t necessarily equate to depressurisation. As a general rule, I’d look for a level off at 10,000’ for a depressurisation. And, I certainly don’t see much reason to be tootling along at 7,000’, down amongst the light aircraft brigade.

 

[Captain Halliday]

Just because they’re descending rapidly doesn’t necessarily equate to depressurisation.

True. Hence "could be".

But in this case it was, as confirmed by "a Qantas spokeswoman".

Qantas flight to Brisbane diverts off route following 'depressurisation' issue

A Qantas flight from Townsville to Brisbane has been forced to divert and land at the nearby Rockhampton Ai...

www.9news.com.au

I certainly don’t see much reason to be tootling along at 7,000’, down amongst the light aircraft brigade.

What operational reasons might there be for going to 7,000' for a pressurisation issue?

 

[jb747]

But in this case it was, as confirmed by "a Qantas spokeswoman".

The quotation marks are probably appropriate. Most of the spokespeople struggle to understand that the company operates aircraft.

There are depressurisations and pressurisation issues, and they're quite different animals. Basically though, you either need a hole for any air to escape, an issue with a pressurisation controller causing the outflow valve to open, or a pack problem meaning that no air is coming in.

QF 30 is an example of the first, and in the absence of images of a holy Alliance aircraft, I'll assume it was intact. Also notable is that in the event of this sort of hole, you cannot use a maximum rate descent, simply because the structure may not be able to handle it. The Alliance descent is extremely rapid, ergo, nothing structural.

An issue with the pressurisation controller will result in either an alternate form of operation or a reversion to manual operation. Manual is a PITA, and really tends to take the pilot doing it (generally the FO) right out of the loop. I've not actually heard of a controller fully opening without being commanded to do so, but it's pretty easy to make an error in this mode. If the aircraft dispatched in this mode (there might be an MEL), then selection of a lower than usual cruise height might also be advisable.

I don't know anything much about the aircraft concerned, but I'd expect it to have two packs, with one running off each engine. There would definitely be MEL relief available for an inoperative pack. This MEL may also impose a limit altitude around FL290. The loss of both packs would result in the cabin pressure bleeding down. It's not super rapid, and a prompt descent could stop the cabin rising enough to cause the deployment of the masks. My guess (based on bugger all) is that the event was something along these lines.

What operational reasons might there be for going to 7,000' for a pressurisation issue?

None really. They had a huge rate of descent, and I think they simply overshot the level off.

 

[mysticgreg]

Welcome to AFF - took a while for your first post

Thanks! Yeah I definitely lurked for a while. Time to be more active!