Packs and the 747-200/300s
Most of newer generation (yet now old) 747-200/300s were produced with 3 packs, except the 200Fs which were designed with only 2 packs for specific cargo operations. I also recall old (very old) 747-100s that I flew, that were keeping good cabin altitude on only 1 pack, at say FL 350...
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What we do nowadays - with our 747-200s in passenger operations, is to cruise with one pack in full flow and one other pack in "half-flow" with low passenger loads, or two packs when we have a full cabin daylight flight.
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I have flown with cargo planes - often these were dry leased, converted passenger aircraft which had 3 packs, with the nš 2 pack conveniently labeled INOP (to save on maintenance) - yet, that nš 2 pack turned out to be fully operational - funny, they did not remove the pack all together to save on weight. I wish the INOP status was fully documented to crews.
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As to minimum dispatch MEL considerations, yes, we say - passenger airplanes must be dispatched with 2 operating packs, and we can depart with 1 pack if cargo flight, or if operating a passenger aircraft at/below FL 250.
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The idea of running a passenger aircraft with high cabin altitude (low PSI differential) is often considered. On "wild" charter flights with a bunch of drunks returning from a football/soccer game - or with children excited by their Disneyworld visit, we experiment running the cabin at 9,500 ft altitude. This puts everyone to sleep to the satisfaction of the cabin staff... After all, people from La Paz, Bolivia live fine, at 13,000 ft MSL, with "Pisco" brandy bottles at full flow.
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With the OPEC barrel at $120... this is what we have come to. Sorry...
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Happy contrails as usual...