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The fluid flow treated in this section is isothermal, subsonic, and incompressible. The effects of heat addition, work on the fluid, variation in sonic velocity, and changes in elevation are neglected. An incompressible fluid is one in which a change in pressure causes no resulting change in fluid density. The assumption that liquids are incompressible introduces no appreciable error in calculations, but the assumption that a gas is incompressible introduces an error of a magnitude that is dependent on the fluid velocity and on the loss coefficient of the particular duct section or piece of equipment. Fig. 1A-1 shows the error in pressure drop resulting from assuming that air is incompressible. With reasonably small loss coefficients and the accuracy that is usually required in most calculations, compressible fluids may be treated as incompressible for velocities less than Mach 0.2.

The fluid flow treated in this section is isothermal, subsonic, and incompressible. The effects of heat addition, work on the fluid, variation in sonic velocity, and changes in elevation are neglected. An incompressible fluid is one in which a change in pressure causes no resulting change in fluid density. The assumption that liquids are incompressible introduces no appreciable error in calculations, but the assumption that a gas is incompressible introduces an error of a magnitude that is dependent on the fluid velocity and on the loss coefficient of the particular duct section or piece of equipment. Fig. 1A-1 shows the error in pressure drop resulting from assuming that air is incompressible. With reasonably small loss coefficients and the accuracy that is usually required in most calculations, compressible fluids may be treated as incompressible for velocities less than Mach 0.2.

Recommendations of this ARP refer specifically to the application of closed cycle vapor cycle refrigeration systems as a source of cooling in an aircraft air conditioning system. General recommendations for an air conditioning system which may include a vapor cycle system as a cooling source are included in ARP85, Air Conditioning Equipment, General Requirements for Subsonic Airplanes, ARP292, Air Conditioning, Helicopters, General Requirements For, and AIR806, Air Conditioning Design Information for Cargo and High Density Passenger Transport Airplanes, and are not included herein. Vapor cycle refrigeration system design recommendations are presented in this ARP in the following general areas: a SYSTEM Design Recommendations: (See Section 3) b COMPONENT Design Recommendations: (See Section 4) c Desirable Design Features: (See Section 5)

The purpose of this SAE Aerospace Recommended Practice (ARP) is to establish recommendations for the design, installation and testing of air vehicle vapor cycle refrigeration systems. These recommendations are representative of the refrigerant cycles.

The purpose of this SAE Aerospace Recommended Practice (ARP) is to establish recommendations for the design, installation and testing of air vehicle vapor cycle refrigeration systems. These recommendations are representative of the refrigerant cycles.

This document defines tests to be performed on electrically, pneumatically, and mechanically actuated (regulating, modulating, and shutoff) air valves. The valves may be further defined as those which function in response to externally applied forces or in response to variations in upstream and/or downstream duct air conditions to maintain a calibrated duct air condition (i.e., air flow, air pressure, air temperature, air pressure ratio, etc.). The requirements of this document should govern for all qualification tests unless different requirements are established by the detail specifications.

This document defines the tests to be performed on electrically, pneumatically, and mechanically actuated (regulating, modulating, and shutoff) air valves. The valves may be further defined as those which function in response to externally applied forces or in response to variations in upstream and/or downstream duct air conditions to maintain a calibrated duct air condition (i. e., air flow, air pressure, air temperature, air pressure ratio, etc. ). The requirements of this document should govern for all qualification tests unless different requirements are established by the detail specifications.

Recommendations of this ARP refer specifically to the application of closed cycle vapor cycle refrigeration systems as a source of cooling in an aircraft air conditioning system. General recommendations for an air conditioning system which may include a vapor cycle system as a cooling source are included in ARP 85, Air Conditioning Equipment, General Requirements for Subsonic Airplanes, ARP 292, Air Conditioning, Helicopters, General Requirements For, and AIR 806, Air Conditioning Design Information for Cargo and High Density Passenger Transport Airplanes, and are not included herein.

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.

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.

This document supplements ARP85, to extend its use in the design of ECS for supersonic transports. The ECS provides an environment controlled within specified operational limits of comfort and safety, for humans, animals, and equipment. These limits include pressure, temperature, humidity, conditioned air velocity, ventilation rate, thermal radiation, wall temperature, audible noise, vibration, and composition (ozone, contaminants, etc.) of the environment. The ECS is comprised of equipment, controls, and indicators that supply and distribute conditioned air to the occupied compartments. This system is defined within the ATA 100 specification, Chapter 21. It interfaces with the pneumatic system (Chapter 36 of ATA 100), at the inlet of the air conditioning system shutoff valves.

This document supplements ARP85, to extend its use in the design of ECS for supersonic transports. The ECS provides an environment controlled within specified operational limits of comfort and safety, for humans, animals, and equipment. These limits include pressure, temperature, humidity, conditioned air velocity, ventilation rate, thermal radiation, wall temperature, audible noise, vibration, and composition (ozone, contaminants, etc.) of the environment. The ECS is comprised of equipment, controls, and indicators that supply and distribute conditioned air to the occupied compartments. This system is defined within the ATA 100 specification, Chapter 21. It interfaces with the pneumatic system (Chapter 36 of ATA 100), at the inlet of the air conditioning system shutoff valves.

This report contains background information on life cycle cost elements and key ECS cost factors. Elements of life cycle costs are defined from initial design phases through operational use. Information on how ECS designs affect overall aircraft cost and information on primary factors affecting ECS costs are discussed. Key steps or efforts for comparing ECS designs on the basis of LCC are outlined. Brief descriptions of two computer programs for estimating LCC of total aircraft programs and their use to estimate ECS LCC, are included.

This report contains background information on life cycle cost elements and key ECS cost factors. Elements of life cycle costs are defined from initial design phases through operational use. Information on how ECS designs affect overall aircraft cost and information on primary factors affecting ECS costs are discussed. Key steps or efforts for comparing ECS designs on the basis of LCC are outlined. Brief descriptions of two computer programs for estimating LCC of total aircraft programs and their use to estimate ECS LCC, are included.

The Engineering Analysis SYstem (EASY) computer program is summarized in this report. It provides techniques for analysis of steady-state and dynamic (transient) environmental control system (ECS) performance, control system stability, and for synthesis of optimal ECS. General uses of a transient analysis computer program for ECS design and development, and general features of EASY relative to these uses, are presented. This report summarizes the nine analysis options of EASY, EASY program organization for analyzing ECS, data input to the program and resulting data output, and a discussion of EASY limitations. Appendices provide general definitions for dynamic analysis, and samples of input and output for EASY.

This AIR is intended as a status report on the work of E.C.S. to date in dealing with the problem of equipment cooling in present and immediate future civil transport aircraft. Subsequent revisions to this AIR will follow as more information is gathered on this subject.

This report contains background information on life cycle cost elements and key ECS cost factors. Elements of life cycle costs are defined from initial design phases through operational use. Information on how ECS designs affect overall aircraft cost and information on primary factors affecting ECS costs are discussed. Key steps or efforts for comparing ECS designs on the basis of LCC are outlined. Brief descriptions of two computer programs for estimating LCC of total aircraft programs and their use to estimate ECS LCC, are included.

The Environmental Control Analysis SYstem (EASY) computer program is summarized in this report. Development of this computer program initially was sponsored by the U.S. Air Force Flight Dynamics Laboratory. (See References 1, 2, 3, and 4.) It provides techniques for determination of steady state and dynamic (transient) ECS performance, and of control system stability; and for synthesis of optimal ECS control systems. The program is available from the U.S. Air Force, or as a proprietary commercial version. General uses of a transient analysis computer program for ECS design and development, and general features of EASY relative to these uses, are presented. This report summarizes the nine analysis options of EASY, EASY program organization for analyzing ECS, data input to the program and resulting data output, and a discussion of EASY limitations. Appendices provide general definitions for dynamic analysis, and samples of input and output for EASY.

This document supplements and in some cases supersedes the recommendations presented in ARP 85D, which refers to subsonic civil transports.