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For any modern aircraft to fly at high altitudes, it must be equipped with an air conditioning and pressurization system, which provides a convenient environment for its passengers.
The air management system or environmental control system (ECS) on an aircraft is the systems which provide and sometimes modifies the air supply to different parts of the aircraft.
These systems include mechanical, electric and pneumatic components. Most aircraft will comprise multiple systems designed to perform engine cooling, liquid cooling, thermal control, cabin pressurisation and cabin temperature control, ventilation, smoke detection, fire suppression, fuel tank inerting and ice suppression.
These systems must all comply with strict health and safety standards designed to meet requirements for efficiency, performance, safety and reliability. The maintenance plans are also strictly enforced with ‘no-fly’ rules against any infringement.
The capability of some companies to build, supply, install and service their own units makes an efficient option. Both the air systems themselves and the connected infrastructure such as, engine bleed air ports, engine air distribution pneumatics and cabin pressurisation system passages are all required to be inspected at regular intervals.
All service operators will have complete certification testing at regular intervals to meet international service standards for air management systems.
The main components of the air management system or environmental control system (ECS) on an aircraft can be broken into the following systems:
Cold Air Unit
Some cold air unit use a vapor-compressing refrigerant much like one used in a home air conditioner however, most modern aircraft cold air units no longer contain Freon refrigerants but use air cycle machines to use Ram air as a refrigerant. The cold air unit can be seen as a refrigeration unit. For residential and commercial building systems we use a different air conditioning company called Stinson Air.
Ram Air System
The Ram Air System is a small duct or inlet in the fuselage of the aircraft that collects outside air. Ram air can be used for cooling and for air distribution for the cabin.
Outside air from Ram air is mixed with recirculated filtered air and fed into a manifold that filter bacteria and viruses. These filters are usually high efficiency particulate arresting filters (HEPA filters). From these filters the air is fed to the cabin through the air conditioning A/C pack that moderates temperature and delivers it throughout the cabin via overhead ducts.
Cabin pressure needs to be controlled with the change in the aircrafts altitude, this follows a ‘cabin pressure schedule’. This is controlled by both out-flow valves on the aircrafts fuselage and their pressurisation unit. The air at aircraft cruising altitudes is generally very dry and remains that way to reduce the chances of condensation and corrosion of electrical components. This means typical cabin humidity levels don’t exceed 10% humidity – this can cause fatigue for passengers or discomfort like dehydration, dry eyes and dry nasal passages. There are some newer aircraft that use better corrosion-resistant components so that they can operate their cabin humidity up to 16% to improve comfort on longer flights.
Engine Bleed Air Systems
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 and temperature sensors. 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.
Cabin Pressure and Air Conditioning
The atmospheric pressure decreases as the plane rises in altitude. It becomes incompatible with the human physiology at low pressures. 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.
Supplemental Air Cooling Systems
As well as the air conditioning system used to cool the cabin air for the passengers, an additional on-board cooling system might be necessary for food storage, avionics thermal management and for use on such systems to cool down radars or electronics. 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.
Fuel Tank Inerting Air Supply
An inerting system decreases the probability of combustion of flammable materials stored in a confined space, especially in a fuel tank, Nitrogen generation for fuel tank inerting requires the supply of high pressure air based on bleed air or electrically compressed air from components like heat exchangers, valves, air cycle machines, compressors and associated controls.
Airframe anti-icing System
The accumulation of ice typically deteriorates the wing aerodynamic performance of aircraft, increasing the aircraft’s weight and being detrimental to the aircraft’s performance 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 intakes and the leading edges of the wings and tail.
Air Conditioning and Air Management Systems Installation
Air management test rigs allow for performance of elaborate tests of complete aircraft air systems. A test center is typically equipped with vibration test rigs, a noise optimization anechoic chamber and altitude chambers of various sizes. This allows to test all electrically driven air management systems in all types of conditions.
Our Airplane Hangars
We have converted all of our airplane hangar floors to polished concrete. We previously used epoxy and urethane paints but found this wore out fairly quickly and started looking shabby after not much time at all. Polished concrete really looks great and is super high wearing and low maintenance; it must be the most durable flooring available.
Polished concrete is increasingly being used in many industrial and commercial facilities worldwide for its superior life span, durability and cleanability. Using polished concrete floors in airplane hangars is great because it also provides excellent reflectiveness for increasing the lighting in the hangar. Our friends at Designer Floors – Polished concrete and Terrastone for exposed aggregate, both are experts and we highly recommend their services.
Fall Protection Systems in Aircraft Hangars
Aviation maintenance personnel use a variety of fall protection systems to deal with working at heights on smooth, slippery surfaces like airplane fuselage and wings. The differing shapes and sizes of planes and hangars require each fall protection systems to be versatile. Some systems are ceiling hung, fixed rail and trolley systems. These require the strength and support of the hangar to be sufficient to safely take the added load. Others are portable vacuum anchor points that can be affixed temporarily on the airplane itself. These allow staff to attach to the temporary lifelines stretched between the vacuum anchor points like in the picture to the right.
An aircraft fall protection system that is typically used inside a hangar is more than likely going to be an overhead rigid rail and trolley system. These systems offer the ability to provide fall protection for 100% of planned coverage for planes that the hangar is designed for. Outside of hangar or on-tarmac fall protection systems are likely going to be the vacuum anchor type. These portable systems can be used no matter what position the plane is in and will typically also allow complete access to the fuselage, wings and tail section. See Haz-Ed for where we do our working at heights training.