Air management systems

Air conditioning

Air conditioning systems create a safe and comfortable environment for passengers and crews inside the aircraft cabin: significant amounts of cooled fresh air are hence brought into the pressurized cabin in order to maintain a comfortable cabin environment and also to ensure avionics and electronics ventilation and/or cooling.

The air conditioning system processes high pressure, high temperature air which is most of the time taken or “bled” from the aircraft engines (engine bleed air system).

The core of the air conditioning system consists of air conditioning packs based on the so-called air cycle machines using air bearing technology allowing higher reliability. These air cycle machines are usually pneumatically driven but can also be either electrically or mechanically driven. Various components like heat exchangers, re-heaters, condensers, water extractors, flow control valves, sensors or controllers are also part of the system.

Once the cooled air is blown into the cabin, it needs to be ducted to the appropriate zones and circulated in the cabin. This is accomplished by the so-called cabin distribution system.

Ventilation and heating

Some consumers may require local ventilation. This function is performed by the ventilation control system, basically made of electrically driven fans, valves, sensors, controllers and software. Some others may require local cooling. This is typically ensured by a vapor cycle system. Various components like compressors, heat exchangers, evaporators, condensers, water extractors, sensors and controllers are part of the system.

Alternatively, when required, Liebherr systems can also provide local heating, for instance, within the crew rest areas. This is ensured by the heaters developed by Liebherr.

Humidification

Liebherr offers additional technologies enhancing the cabin air quality and thus the comfort of passengers and crew.

As the atmosphere at high altitude is very dry, cabin air has a very low relative humidity level, especially during long flights. It is therefore necessary to raise the air humidity level up to 20 or 25 per cent in order to guarantee appropriate comfort conditions for passengers and crew, either in the cockpit, the cabin or the crew rest compartments.

Liebherr supplies humidification systems for commercial airplanes and business jets. Connected to the water system of the aircraft, this system may be either powered by engine bleed air or by the aircraft’s electrical network.

If an aircraft needs to be upgraded to incorporate such a system, Liebherr proposes a specific installation (Supplemental Type Certificate).

The atmospheric pressure decreases as the altitude rises and becomes incompatible with the human physiology. That is why the pressure level and change rate inside the cabin need to be controlled in order to provide satisfactory pressure values for comfort and safety of passengers and crew. During all flight phases this is done fully automatically by the pressurization control system.

The complete cabin pressure control system provided by Liebherr includes outflow and safety valves, control panel, controller and software.

Besides the air conditioning system used to cool the air in the cabin for the passengers, an additional on-board cooling system might be necessary for food storage or avionics thermal management.

This function is achieved by a high power centralized cooling system. The cooling generated is distributed by a liquid loop carrying cooling in every place where it is required. A heat exchanger connected to this liquid loop converts the cooling power into air cooling blown on the food.

Such systems can also be used to cool down radars or electronics.

Liebherr also supplies hydraulic cooling systems to cool down high pressure (5,000 psi) hydraulic channels onboard the aircraft.