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A life support system (LSS) is usually defined as a system that provides elements necessary for maintaining human life and health in the state required for performing a prescribed mission. The LSS, depending upon specific design requirements, will provide pressure, temperature, and composition of local atmosphere, food, and water. It may or may not collect, dispose, or reprocess wastes such as carbon dioxide, water vapor, urine, and feces. It can be seen from the preceding definition that LSS requirements may differ widely, depending on the mission specified, such as operation in Earth orbit or lunar mission. In all cases the time of operation is an important design factor. An LSS is sometimes briefly defined as a system providing atmospheric control and water, waste, and thermal management.

This publication will discuss water carryover from the environmental control system with respect to causes and indicated corrective or preventative action. In addition, condensation on structure will be reviewed with possible preventative action described.

Many different computer programs have been developed to determine performance capabilities of aircraft environmental control systems, and to calculate size and weight tradeoffs during preliminary design. Many of these computer programs are limited in scope to a particular arrangement of components for a specific application. General techniques, providing flexibility to handle varied types of ECS configurations and different requirements (i.e., during conceptual or preliminary design, development, testing, production, and operation) are designated "company proprietary" and are not available for industry-wide use. This document describes capabilities, limitations, and potentials of a particular computer program which provides a general ECS analysis capability, and is available for use in industry. This program, names AECS1, was developed under the sponsorship of the U.S. Air Force Flight Dynamics Laboratory (References 1 and 2).

Many different computer programs have been developed to determine performance capabilities of aircraft environmental control systems, and to calculate size and weight tradeoffs during preliminary design. Many of these computer programs are limited in scope to a particular arrangement of components for a specific application. General techniques, providing flexibility to handle varied types of ECS configurations and different requirements (i.e., during conceptual or preliminary design, development, testing, production, and operation) are designated “company proprietary” and are not available for industry-wide use. This document describes capabilities, limitations, and potentials of a particular computer program which provides a general ECS analysis capability, and is available for use in industry. This program, names AECS1, was developed under the sponsorship of the U.S. Air Force Flight Dynamics Laboratory (References 1 and 2).

It is intended that the scope of this information report be limited to electrical heating of passenger, crew, and cargo compartments only. No attempt has been made to develop the complete electrical circuitry associated with the electrical heating components; however, the electrical circuitry required for heating component operation, safety, and monitoring will be included as available. Specific design information is given for various modern aircraft utilizing electrical heating. Each aircraft discussed will be identified by alphabetical letter designation and included in the appropriate appendix.

It is intended that the scope of this information report be limited to electrical heating of passenger, crew, and cargo compartments only. No attempt has been made to develop the complete electrical circuitry associated with the electrical heating components; however, the electrical circuitry required for heating component operation, safety, and monitoring will be included as available. Specific design information is given for various modern aircraft utilizing electrical heating. Each aircraft discussed will be identified by alphabetical letter designation and included in the appropriate appendix.

It is intended that the scope of this information report be limited to electrical heating of passenger, crew, and cargo compartments only.

This recommended practice covers automatic cabin temperature control systems of the following types for pressurized and unpressurized cabins: Type I - Proportioning. Type II - On-Off, or Cycling. Type III - Floating, including modifications thereof.

The recommendations of this ARP are primarily intended to be applicable to temperature control of compartments, occupied or unoccupied, of civil aircraft whose prime function is the transporting of passengers or cargo. The recommendations will apply, however, to a much broader category of civil and military aircraft where automatic temperature control systems are applicable.

The recommendations of this SAE Aerospace Recommended Practice (ARP) for aircraft compartment automatic temperature control systems are primarily intended to be applicable to occupied or unoccupied compartments of civil and military aircraft.

This SAE Aerospace Recommended Practice (ARP) discusses design philosophy, system and equipment requirements, environmental conditions, and design considerations for rotorcraft environmental control systems (ECS). The rotorcraft ECS comprises that arrangement of equipment, controls, and indicators which supply and distribute dehumidified conditioned air for ventilation, cooling and heating of the occupied compartments, and cooling of the avionics. The principal features of the system are: a A controlled fresh air supply b A means for cooling (air or vapor cycle units and heat exchangers) c A means for removing excess moisture from the air supply d A means for heating e A temperature control system f A conditioned air distribution system The ARP is applicable to both civil and military rotorcraft where an ECS is specified; however, certain requirements peculiar to military applications—such as nuclear, biological, and chemical (NBC) protection—are not covered.

This ARP discusses design philosophy, system and equipment requirements, environmental conditions, and design considerations for helicopter environmental control systems (ECS). The helicopter ECS comprises that arrangement of equipment, controls, and indicators which supply and distribute dehumidified conditioned air for ventilation, cooling and heating of the occupied compartments, and cooling of the avionics. The principal features of the system are: a A controlled fresh air supply b A means for cooling (air or vapor cycle units and heat exchangers) c A means for removing excess moisture from the air supply d A means for heating e A temperature control system f A conditioned air distribution system The ARP is applicable to both civil and military helicopters where an ECS is specified; however, certain requirements peculiar to military applications, such as nuclear, biological and chemical (NBC) protection, are not covered.

This SAE Aerospace Standard (AS) defines the requirements for air cycle air conditioning systems used on military air vehicles for cooling, heating, ventilation, and moisture and contamination control. General recommendations for an air conditioning system, which may include an air cycle system as a cooling source, are included in MIL-E-18927E (AS) and JSSG-2009. Air cycle air conditioning systems include those components which condition high temperature and high pressure air for delivery to occupied and equipment compartments and to electrical and electronic equipment. This document is applicable to open and closed loop air cycle systems. Definitions are contained in Section 5 of this document.

This SAE Aerospace Standard (AS) defines the requirements for air cycle air conditioning systems used on military air vehicles for cooling, heating, ventilation, and moisture and contamination control. General recommendations for an air conditioning system, which may include an air cycle system as a cooling source, are included in MIL-E-18927E and JSSG-2009. Air cycle air conditioning systems include those components which condition high temperature and high pressure air for delivery to occupied and equipment compartments and to electrical and electronic equipment. This document is applicable to open and closed loop air cycle systems. Definitions are contained in Section 5 of this document.

This SAE Aerospace Standard (AS) defines the requirements for air cycle air conditioning systems used on military air vehicles for cooling, heating, ventilation, and moisture and contamination control. General recommendations for an air conditioning system, which may include an air cycle system as a cooling source, are included in MIL-E-18927E (AS) and MIL-E-87145 (USAF). Air cycle air conditioning systems include those components which condition high temperature and high pressure air for delivery to occupied and equipment compartments and to electrical and electronic equipment. This document is applicable to open and closed loop air cycle systems. Definitions are contained in Section 5 of this document.

This report covers the design parameters for various methods of humidification applicable to aircraft, the physiological aspects of low humidities, the possible benefits of controlling cabin humidity, the penalties associated with humidification, and the problems which must be solved for practical aircraft humidification systems. The design information is applicable to commercial and military aircraft. The physiological aspects cover all aircraft environmental control applications.

This SAE Aerospace Information Report (AIR) covers the design parameters for various methods of humidification applicable to aircraft, the physiological aspects of low humidities, the possible benefits of controlling cabin humidity, the penalties associated with humidification, and the problems which must be solved for practical aircraft humidification systems. The design information is applicable to commercial and military aircraft. The physiological aspects cover all aircraft environmental control applications.

This publication outlines general design concepts considered the minimum acceptable standards for use in electrical and electronic equipment. The objective is increased reliability of the equipment without penalizing the aircraft performance.

This SAE Aerospace Information Report (AIR) outlines concepts for the design and use of fault isolation equipment that have general application. The specific focus is on fault isolation of environmental control systems (ECS) in commercial transports. Presented are general fault isolation purposes, design principles, and demonstration of compliance criteria. These are followed by three design examples to aid in understanding the design principles. Future trends in built-in-test-equipment (BITE) design are discussed, some of which represent concepts already being implemented on new equipment.