HiFly LoFly

[Evan]

I will say something else, though, and that is that the crossbleed valve does not, in my opinion, get enough attention in the training process. Granted, it is not something that we manipulate regularly, but it seems to me it does not get the respect it deserves.

Well, pilot error is an important part of my speculation here. And it should be an important part of any consideration when determining safe dispatch condition.

[Evan]

The scenario you describe would require for both BMC lanes to malfunction as well, hence the "failure due to excessive demand". One of BMC's job is precisely to control that demand precisely to prevent what you're describing. So, it seems very unlikely that that's what happened here.

The Airbus lit depicts the Bleed Monitoring Computer in the system description and schematic but makes no mention of a failure as part of the scenario.

Here is a link to that article if it interests you:

https://safetyfirst.airbus.com/app/themes/mh_newsdesk/documents/archives/avoiding-dual-bleed-loss.pdf

This is a 2009 publication, so the problem may have been designed out since then, but perhaps not retrofitted to older planes.

[ATLcrew]

The Airbus lit depicts the Bleed Monitoring Computer in the system description and schematic but makes no mention of a failure as part of the scenario.

Here is a link to that article if it interests you:

https://safetyfirst.airbus.com/app/themes/mh_newsdesk/documents/archives/avoiding-dual-bleed-loss.pdf

This is a 2009 publication, so the problem may have been designed out since then, but perhaps not retrofitted to older planes.

Well...for one thing, that procedure is for a 320 which is not what was involved in the HiFly incident. For another thing, there are 2 BMC, each with 2 lanes, which this "lit" seems to fail to mention. Finally, our current dual bleed loss procedure is different from what is in the "lit", albeit not radically different.

[3WE]

Bobby, Berntie, ATLie: Something happened involving a lot of acronyms. We (see footnote) think pilots and procedure writers get many things wrong, like this incident.

We must make bold and wordy suggestions as to how you stupid insiders should fix it.

Footnote: We is actually referring to as individual outside, ass hat, parlour talker.

Bicycle, bicycle, bicycle, I want to ride my bicycle…

[Evan]

Well...for one thing, that procedure is for a 320 which is not what was involved in the HiFly incident. For another thing, there are 2 BMC, each with 2 lanes, which this "lit" seems to fail to mention. Finally, our current dual bleed loss procedure is different from what is in the "lit", albeit not radically different.

But there are scenarios for the A330 that don't require BMC malfunction, but rather erroneous data sent to the BMC's. This is from a Finnish report of two Finnair incidents in which A330's suffered dual bleed air loss:

Both serious incidents were caused by malfunctioning of the engines’ bleed regulated pressure transducers' (Pr). The malfunctioning was caused by freezing of water that had accumulated in the bleed regulated pressure transducers' pressure cell rooms, extremely confined by design. Due to malfunctioning the transducers provided faulty pressure information to bleed monitoring computers. Due to the erroneous information the computers closed both engines’ bleed air systems which resulted loss of pressurisation in cabin, i.e. an increase in cabin air pressure altitude.

The investigation commission issued four safety recommendations. The European Aviation Safety Agency (EASA) was recommended to: 1) require that Airbus S.A.S. replace the pressure transducers on both engines of A330 aircraft with such transducers that function in conditions approved for the A330 fleet and 2) require that Airbus S.A.S. also include Dual Bleed Loss abnormal procedures in the A330 electronic centralized aircraft monitor action.

This scenario may be contained to certain ambient temperature conditions that wouldn't be present with the flight we're discussing. I don't know that this was ever determined.

As of 2012 (latest data I could find), about 30% of the A330 fleet were still not retrofitted with redesigned parts to contend with the threat.

[Not_Karl]

I want to ride my bicycle

no

[Gabriel]

But there are scenarios for the A330 that don't require BMC malfunction, but rather erroneous data sent to the BMC's. This is from a Finnish report of two Finnair incidents in which A330's suffered dual bleed air loss

Prohibiting dispatch with one PAC inop will not help avoid that. Just saying.

[Evan]

Prohibiting dispatch with one PAC inop will not help avoid that. Just saying.

And if this occurred alongside an engine failure, I guess that would be a hell of a coincidence.

[bstolle]

Prohibiting dispatch with one PAC inop will not help avoid that. Just saying.

Exactly. I assume that evan wants only planes like the Do X, H-4 and B-52 to be used as airliners because history shows that all engines have failed even on four engined jet transports.
One of the downsides of using these planes would be a slightly increased ticket price.

[ATLcrew]

Exactly. I assume that evan wants only planes like the Do X, H-4 and B-52 to be used as airliners because history shows that all engines have failed even on four engined jet transports.
One of the downsides of using these planes would be a slightly increases ticket price.

In fairness, Do X would be EPIC!

[Evan]

In fairness, Do X would be EPIC!

And very low probability of pressurization failure.