Without realizing it, every aircraft passenger has benefitted from a lesser-known system called the Preconditioned Air (PCA) unit. These devices are responsible for providing a comfortable and safe onboard environment to commuters and aircrew during ground operations by circulating fresh air throughout the cabin. Of course, airplanes operate in a wide variety of conditions, and simply pushing ambient air inside the vessel would be ineffective or dangerous in most situations. As such, the PCA unit is responsible for modulating the pressure, humidity, and temperature of the air as it is introduced to the interior. In this blog, we will discuss the composition, operating principles, and other nuances associated with PCA units.
Although PCA units may vary slightly between manufacturers, the majority contain some integral components, including the compressor, refrigeration and heating system, and control module. The compressor is used to pressurize ambient air as it travels through the system. This action also marginally modulates the temperature based on Gay-Lussac's law. Once pressurized, the temperature control system then heats or cools the air depending on the operating environment to ensure a comfortable and safe delivery into the cabin. Meanwhile, another group of components work on regulating the humidity to prevent particularly dry or moist air from reaching the passenger and storage areas. Although this entire process is typically regulated by an automated control element, it may be taken over at any time by an operator.
Depending on the configuration, PCA units may either be powered electrically or by an internal combustion engine. In the past, most diesel engine-driven systems required an associated electrical generator to power the compressor. However, the latest advances have removed this extra requirement and allow the engine to drive this module directly. Although offered at a higher premium, fully electric PCA units are much more efficient and drastically reduce emissions. They also make less noise than their engine-powered counterparts, which benefits both the passengers and ground maintenance personnel.
Customers must also decide between a mobile and a fixed PCA unit. Mobile systems may be towed to any location on the ramp which increases the number of aircraft they may serve. The major downside to this configuration is that it requires a dedicated truck to facilitate hauling. A further argument could be made in terms of space utilization, as a large mobile PCA unit takes up a significant amount of real estate in an already crammed ramp. Fixed on-ground units are another popular option, as these devices take up a small portion of the stand and can be quickly stored when not in use.
When choosing a PCA package, it is important to consider the cost and efficiency aspects of the power supply, as well as the overall mobility of the unit. For example, if a customer operates a busy airport that demands contingency and flexibility with GSE equipment, they may consider a diesel-powered mobile unit. Alternatively, those customers that operate with a more organized and regular schedule of flights may consider the more efficient and space-saving mobile option.
Regardless of the configuration you choose, Emergent Purchasing is here to support your operational requirements with rapid turnaround times and significant cost savings on an inventory of over 2 billion aerospace items. With endless new, used, and obsolete products to choose from, we are confident that you will find the exact component you are looking for. Using our Instant RFQ service, customers can receive a quote in just 15 minutes or less while also being supported by one of our expert account managers. Get started on the purchasing process today to experience a streamlined procurement platform.
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