Talking about history, The DC8 was also equipped with 4 cabin compressors. Those were the 4 significant inlets in the nose. They were switched on after TO by the Fl-Eng in pairs and it needed manual manupulation of the cabin pressurization lever to stabilize the cabin rate of climb.
Before descent the Fl-Eng had to switch the engine bleeds to high to prevent the cabin compressors from stalling (quite frightening for the pax) when the pilot pulled the throttles to idle. At around 15000 ft 2 compressors were shut down ( again manual control of the cabin press.)
Just before touchdown the last 2 were switched off to raise the pneumatic pressure for the engine reverse system. Now this is almost history ('
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