why are they called air conditioning "packs"?

Question

On jet airplanes, the air conditioning systems are called "Packs". I was wondering why.

Answer 1

I think it's just that they've been called that for such a long time that that's what they're called.

On some old 707s, the complete air conditioning pack could be removed as a unit. The 707 was available with either a standard air cycle machine system, or with a conventional freon system. The freon system came out of the airplane as a complete unit; all components were mounted to a frame, which bolted up to the airplane. This modular system could very well have been called a 'pack', and if so, the name stuck.

(The reason for two systems was that the early air cycle systems didn't work very well on the ground; they needed a lot of airflow through their heat exchangers in order to effectively cool a lot of air. The conventional freon systems didn't have that problem. If I remember correctly, most (if not all) TWA 707s had freon packs, and I think at least some of the later Pan Am ones did as well.)

I've never seen an air cycle system on an airliner that could be removed as a unit, however. All the components are attached to the airplane structure separately, though they are all located together in the same part of the airplane (in the belly underneath the wings on Boeings, in the nose on the DC-8, and in the tail on the DC-9/MD-80/MD-90 series).

As far as it originating with an abbreviation of PACS, well, that's entirely possible. I've never seen that abbreviation used in reference to an airliner, but maybe it was a military term (after all, the military just loves abbreviations). However it originated, that's what everyone calls them.

Answer 2

An Air Conditioning pack on an airplane is not the same as your home air conditioner. It is actually called an Enviornmental Control Unit. It conditions air that is brought in from the engines of the plane. When you are flying at 30 - 35 thousand feet the outside air temp is around -50F.and the air must be conditioned for your comfort.

Answer 3

several things on airplanes are called "packs". It is in fact because it is all self contained in one unit. I think the pack is probably an air cycle unit, which is like a car turbocharger with a heat exchanger. When the air is compressed, it heats up. The heat exchanger takes out the heat from the compressed air. Then, when the air decompresses it is cooler than when it started.

Answer 4

Lots of good answers, Shenold is correct.

PAC is an abbreviation for Pressuirzation & Air Conditioning.

As Shenold explained, they are not a one piece unit, they are made up of several parts, the ACM, Seperators, coalescers, heat exchangers, expansion turbines, etc, etc.

The early DC-8s also used the freon systems, they were a pain in the **** to work on tho they did work well.

Answer 5

It’s short for ‘package’.
The valves, pipes, heat exchanges etc. must remain in relative close proximity to each other in order for the system to operate efficiently. If the designer needs to move any main component then all the rest of the system has to move with it. This means the system is treated as a package.

Answer 6

The "packs" are actually spelled "pacs". It stands for pressurization and air conditioning system.

Answer 7

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Answer 8

AC pack that mean a big roof top unit on the roof and that included filters, heat, cold, coil, compessrors and everything in 1 unit....not like in the house unit, coil in the ceiling and compresor on the ground outside the house.

Answer 9

From what I know, It stands for Pneumatic Air Cycle Kit.

Answer 10

I don't know. Could it be that they are preassembled components that can just be swapped out if something goes wrong instead putting the pieces together one by one. I wonder, too.