Definition
In an aircraft air conditioning system, the compressor is the engine- or motor-driven pump that raises the pressure and temperature of refrigerant vapor and circulates it through the system. It draws low-pressure refrigerant vapor from the evaporator, compresses it into a hot high-pressure vapor, and discharges it to the condenser where the heat is rejected.
Plain English
The pump in the air conditioning system that squeezes the refrigerant gas. Squeezing it makes it hot and high-pressure, which is the first step in moving heat out of the cabin and dumping it overboard.
Context Anchor
Seen in aircraft environmental control and air conditioning system descriptions, especially during maintenance, troubleshooting, and system operation checks.
Derivation
From Latin 'comprimere', meaning 'to press together'. The component literally presses the refrigerant vapor into a smaller volume, which raises its pressure and temperature.
Why Pilots Care
The compressor is the heart of the cooling system. If it fails, seizes, or loses its drive belt, cabin cooling stops. On many light aircraft the compressor also adds a noticeable load on the engine when engaged, which is why it is often automatically disengaged at takeoff power.
Analogy
Think of a bicycle pump. When you push the handle down, the air inside gets squeezed and the pump body warms up. The air conditioning compressor does the same thing continuously to refrigerant vapor.
Intuition Check
Do not confuse this with an engine compressor in a turbine engine. Here, “compressor” means the air conditioning system component that pressurizes refrigerant for cabin cooling.
Example Sentence 1
After starting the engine, the technician engaged the air conditioning and listened for the compressor clutch to click in.
Example Sentence 2
Low refrigerant pressure often points to a failing compressor that must be replaced during scheduled maintenance.