Editing Air cycle machine (section)

== Nomenclature ==

===Types===
The types of air cycle machines may be identified as:
*Simple cycle consisting of a turbine and fan on a common shaft
*Two-wheel bootstrap consisting of a turbine and compressor on a common shaft
*Three-wheel consisting of a turbine, compressor, and fan on a common shaft
*Four-wheel/dual-spool consisting of two turbines, a compressor, and a fan on a common shaft

===Abbreviations===
The equipment is referred to variously as ''PAC'', air conditioning ''pack'', or A/C ''pack'', but there is a lack of consistency and agreement as to the derivations and meanings:
*''Pack.'' as an abbreviation of ''package'', applied to both pneumatic and non-pneumatic systems ([[Boeing]], [[Airbus]], [[Embraer]], [[Bombardier Inc.|Bombardier]] and [[Lockheed Martin|Lockheed]])
*''PAC'' as an acronym meaning either ''Passenger Air Conditioning'' or ''pneumatic air conditioning'' (the latter being found on systems control panels of at least one business jet supplier)
*''PACK'' as an acronym for ''pneumatic air cycle kit'' or ''pressurization & air conditioning kit''