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--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
Solving the puzzle requires determining if a single engine failure (not uncontained, apparently) and loss of a single pack can result in a loss of cabin pressure that would require a descent to 10,000ft (11,000 here due to MSA). I can’t solve that one, except for coincidence. I suspect I’m missing something…
Solving the puzzle requires determining if a single engine failure (not uncontained, apparently) and loss of a single pack can result in a loss of cabin pressure that would require a descent to 10,000ft (11,000 here due to MSA). I can’t solve that one, except for coincidence. I suspect I’m missing something…
Maybe the PAC on the other engine had been MEL'd? Maybe. Maybe not.
Would you call that "Coincidence"? Maybe, maybe not.
Now, if one engine failed and the PAC in the other engine failed independently during the flight (before or after the engine failure, probably before because apparently the depressurization seem to have been immediate when the engine failed), that would qualify as coincidence. Or of there was an independent fault of an outflow valve.
Maybe something else. (Then again maybe not).
I would say let's wait for the final report but, while there will likely be a final report up there, I don't think that it will get coverage and I don't think that I will look it up 4 years from now. Or maybe I will.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
Maybe the PAC on the other engine had been MEL'd? Maybe. Maybe not.
That's what I was thinking, that this may have been a MEL dispatch violation before realizing that this was probably not an ETOPS flight. The MMEL only requires both packs operational for ETOPS.
And that's exactly what I thought you were thinking and the reason why I answered maybe, maybe not.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
Why would the PAC (or PACK) be a DMI (Deferred Maintenance Item) normally used for non-critical things like cosmetic issues or a cabin bulb burned out)? The PAC's control pressurization and enable humans (including crew) to breathe and remain conscious and functioning, so it would be critical.
So I meant MEL.I could have been wrong. But I apparently I wasn't.
I found an FAA-approved MMEL for the ATR-72 (admittedly old, from 1997, so it may have changed but I don't think that the Packs would have been kicked out of the MMEL in a revision).
50-1 - Packs
Number installed: 2
Number required for dispatch: 1
Remarks or exceptions: One may be inoperative provided flight remains at or below 17,000 feet MSL.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
The A330 MMEL specifies that both Packs must be operative for dispatch. Exceptions: Non-ETOPS flights may be dispatched with 1 Pack inoperative. (paraphrasing)
This means, of course, if the engine driving the operative pack fails in flight, cabin pressurization is lost and the flight must return or divert near or below 10,000ft altitude.
This means, of course, that if a non-ETOPS flight experiences this scenario while overflying a mountainous area with MSA well above 10,000ft, you could be in a world of hurt.
What is the wisdom behind dispatching a commercial passenger airliner with a single operative pack under any circumstances? "Probably be okay"?
Or are there perhaps further MEL restrictions to this regarding terrain?
I know (I said that in my answer) but I don't understand your point. I meant MEL, not DMI. Is there any reason why I should have meant DMI instead of MEL for dispatching an airplane with a PAC inop?
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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