Commercial Airliner Environmental Control System Engineering Aspects of Cabin Air Quality

This paper discusses engineering aspects of a modern commercial jet airliner environmental control system (ECS), focusing on cabin air quality. Recent national news media coverage suggests that aircraft cabin air quality is a serious concern. However, an objective review of pertinent data and recent comprehensive testing do not support this perception. Even more important than “air quality” is “survivability.” Because modern jet airplanes operate in a physical environment that is not survivable by unprotected humans, these airplanes contain a complex ECS. Such systems enable survival, safety, and comfort. Aerospace medical experts are highly cognizant of this fact. ECS engineers study requirements for maintaining human physiological integrity, provided by the aerospace medical community. These requirements are converted into components for environmental control and life support systems. Data from studies of human comfort factors are also applied to the design of these systems. The following discussion reviews the major components of the ECS that sustains human life and comfort during flight. To illustrate how the ECS works, a volume of air will be followed as it flows continuously from outside the airplane into the airplane cabin and, finally, exits the airplane. The initial conditions and subsequent changes to this volume of air as it travels through each component of the ECS system during various flight phases will be discussed. Figure 1 is a schematic of the ECS components for the Boeing 767 airplane. The 767 is a modern generation airplane that uses 50% filtered recirculated air and 50% outside air. This is typical of modern generation airplanes. Engine (2 locations) Cabin pressure control valve