Air management systems
The air management system is among the most important contributors to the comfort on board an aircraft.
Liebherr has complete capability to develop, supply and service all aircraft and engine air systems: from the engine bleed air ports and engine pneumatics to the air distribution in the cabin and from the wing ice protection system to the cabin pressurization.
Liebherr also offers supplemental cooling, hydraulic cooling, fuel tank inerting air supply or air humidification. The company can either supply a complete integrated air management system (i.e. unique controller to drive multiple systems) or an individual dedicated system.
Liebherr masters the complete development including certification testing, as well as the production and worldwide customer services all along product life.
Liebherr is the system supplier for all kinds of platforms like commercial aircraft, regional aircraft, business jets, helicopters, UAV’s, fighters or military transport airlifters.
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.
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).
Engine bleed air systems bleed high pressure, high temperature air from the engine's low and high pressure ports. The air flow is processed through temperature and pressure control devices and supplied downstream to the aircraft's main air conditioning system, to the airframe anti-icing system and to the main engine starting system.
An engine bleed air system consists of temperature control valves, pressure regulating and shut-off valves, high pressure valves, over-pressure valves, pre-coolers heat exchangers, high pressure ducting, temperature sensors, pressure sensors, overheat / hot air leak detection devices and a control and monitoring electronic unit.
Liebherr also supplies high pressure, high temperature engine pneumatic valves and heat exchangers to perform such functions as cowl anti-icing, intermediate pressure check valve, handling bleed off valve, high pressure/low pressure clearance regulating valve.
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.
When a plane flies in frosting conditions, the nacelle and wings can be covered with white frost. There can even be accumulation of ice on the leading edges.
This accumulation of ice typically deteriorates the wing aerodynamic performances, in addition to increasing the aircraft’s weight, which is particularly detrimental to the aircraft’s performances and safety. It is therefore necessary to remove this ice or to prevent ice accretion.
The airframe anti-icing system carries hot air supplied by the engine bleed air system and blows it along the ice-sensitive parts of the airframe (engine nacelle air intakes, wing and tail leading edge).
An airframe anti-icing system is made up of pressure regulating valves, temperature sensors, pressure sensors, high pressure ducting, overheat / hot air leak detection devices and controller.
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.
Nitrogen generation for fuel tank inerting requires the supply of high pressure air. Liebherr offers a wide range of fuel tank inerting air supply systems based on bleed air or electrically compressed air thanks to such proprietary components as heat exchangers, valves, air cycle machines, compressors and associated controls.
Liebherr operates large air system testing facilities in Toulouse, France. Here, air management test rigs allow to perform elaborate tests of complete aircraft air systems.
The test center ISA (“Intégration des Systèmes d’Air”) at Toulouse, allows to test particularly all electrically driven systems of a future more electric aircraft.
Equiped with state-of-the-art vibration test rigs, a noise optimization anechoic chamber and altitude chambers of various sizes, the test center is a powerful research and development tool.