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18

The "packs" (or A/C on the aircraft) are powered by engine bleed air. When bleed air is extracted from the engines, less thrust can be produced. This may be a problem if the airplane is taking off at a high elevation airport or the departure path requires a certain climb gradient to clear obstacles. This action does create some discomfort in the cabin so it'...


17

If all ACM failed, an alarm would sound in the cockpit. And two messages would appear on the ECAM/EICAS¹. One indicating that the ACMs failed and the other indicating that cabin altitude² is rising above desired level. Pilots would execute corresponding checklist, and the one for rising cabin altitude calls for rapid descent to 10,000 ft. That is the ...


15

What powers the airconditioning on most airliners is APU or main engine compressor bleed, which is being supplied at fairly high pressure, say, 80 psi, and temperature, around 3-400F, to the air conditioning packs. You normally have a choice to select APU or main engine bleed. You will obviously use APU bleed on the ground before engine start, but also may ...


13

Pilots will turn off the packs for takeoff if maximum engine performance is needed or if there is a need to prioritize a high demand bleed draw. The particulars of the situations calling for a packs-off takeoff is airframe specific. In the EMB-145, normal takeoff was with the APU bleed powering the packs. The specific configuration calls for engine ...


11

The 747-8 has three packs, and it is feasible to complete the flight with one of them inoperative (in case of aircraft with two packs, cabin altitude can be maintained win any one). The following is taken from the Minimum Equipment list of 747-8: Screengrab from 747-8 MEL As can be seen, flight is possible with some limitations. In case of a failure in-...


9

Source: FCOM A320 familly From the flight crew operating manual (FCOM) about the pack flow selector (4): Permits the selection of pack valve flow, according to the number of passengers and ambient conditions (smoke removal, hot or wet conditions). LO (80 %) - NORM (100 %) - Hl (120 %). Manual selection is irrelevant in single pack operation, ...


8

Water comes from condensing water vapor present in the cabin, itself coming from human breathing and perspiration, and, for a small part, from atmosphere. The question mentions an air generation unit which is an Airbus terminology, so let's go into the A380 air system: A380 Engineering training, source (page 101) The two green labels are my addition to ...


7

Best answer that I can think of, without the exact engineering or design info, is that since the A/C packs are run with engine bleed air, if you need the extra thrust from the engines, you'd turn off the packs for that extra power for take off... When I did my dispatcher certificate, we used the 727... and from my notes, you'd get a 1500 lbs increase in ...


7

Photo source: own work. In-flight with the Right Pack inoperative—the button with the sticker. It is legal; the flight was limited to FL250, and the air conditioning was switched off for the take-off. If the flight is a long haul, the limited cruise altitude will limit the range. Grounding the plane would make sense then, fuel wise. The airline and the ...


5

The general answer is, the engine bleeds stay on almost all the time. The times they're turned off: For a bleeds-off takeoff to get more power from the engines. During deicing on the ground, so that deicing fluid doesn't get in the bleed air system. When you are using the APU bleed air, the #1 engine bleed switch needs to be off IF that engine is running ...


3

Pack flow is air flow through the air conditioning packs. There are two packs, one operated by each engine. Normally the system works on two packs, with some portion of the cabin air filtered and recirculated. The entire system can operate one one pack, which then must set to HIGH. Yes if you put the pack on HIGH flow it means that that pack and all its ...


2

It's not a normal A/C unit Aircraft do not use a Freon based compressor vapor-liquid transition heat pump type arrangement the way every home, car, boat and train does. They use a simpler cycle, because most turbine aircraft have a great abundance of compressed air available, or are obliged to have compressors anyway for pressurization. The compressed-air A/...


2

The running engines power commercial airliner interior climate and environmental control through their built in electrical generators and bleed air systems. The units that supply the interior air in the correct temperature and pressure for passengers are sometimes called PACK as an acronym for Pneumatic Air Cycle Kit. When the engines are off, the APU (...


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