747-400 T/O with packs off
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Join Date: Jan 2007
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747-400 T/O with packs off
Recently I read of an article where in the pilots took off with all pack selectors in OFF posn n realised that only at about 10,000 ft.
Is it possible that no EICAS msg would have come till then?
Is it possible that no EICAS msg would have come till then?
Join Date: Dec 2000
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If you take off with packs off in a 744, the cabin will only climb at about 1000ft/min. Taking off from sea level, it will take about 5 minutes to get to 10,000ft altitude, by which time the cabin will only have climbed to about 5,000ft. You will therefore not trigger any warnings. If you start off above sea level (eg Mexico City at over 7,000ft) then the cabin will reach the Eicas warning level much sooner.
There is no substitute for airmanship in checking systems, but sometimes events can conspire against you (bad wx + failures + comms problems) and you may end up being 'reminded' by the aircrafts monitoring systems.
Indeed, engine failures etc at places like Mexico City, where there are significant performance and terrain issues, can lead you into marginal situations where the oxygen masks dropping are the least of your worries!
For that reason, some airlines (mine used to), may configure APU to 1 pack for take off so that the pressurisation is not an issue with an EFATO.
There is no substitute for airmanship in checking systems, but sometimes events can conspire against you (bad wx + failures + comms problems) and you may end up being 'reminded' by the aircrafts monitoring systems.
Indeed, engine failures etc at places like Mexico City, where there are significant performance and terrain issues, can lead you into marginal situations where the oxygen masks dropping are the least of your worries!
For that reason, some airlines (mine used to), may configure APU to 1 pack for take off so that the pressurisation is not an issue with an EFATO.
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Is it possible that no EICAS msg would have come till then?
The "CABIN ALTITUDE" EICAS message with aural warning presents at 8250 feet Cabin Altitude.
Regards,
Old Smokey
The "CABIN ALTITUDE" EICAS message with aural warning presents at 8250 feet Cabin Altitude.
Regards,
Old Smokey
