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This report revises ARD50015 document to the AIR format. This report, as was the original, is intended to complement ARP1420C and AIR1419C documents issued by the SAE S-16 Committee on spatial total-pressure distortion. These previous documents addressed only total-pressure distortion and excluded total temperature distortion. The subject of inlet total temperature distortion is addressed in this report with some background and identification of the problem area. The status of past efforts is reviewed, and an attempt is made to define where we are today. Deficiencies, voids, and limitations in knowledge and test techniques for total temperature distortion are identified.

“An Assessment of Planar Waves” provides background on some of the history of planar waves, which are time-dependent variations of inlet recovery, as well as establishing a hierarchy for categorizing various types of planar waves. It further identifies approaches for establishing compression-component and engine sensitivities to planar waves, and methods for accounting for the destabilizing effects of planar waves. This document contains an extensive list and categorization (see Appendix A) of references to aid both the newcomer and the practitioner on this subject. The committee acknowledges that this document addresses only the impact of planar waves on compression-component stability and does not address the impact of planar waves on augmenter rumble, engine structural issues, and/or pilot discomfort.

“An Assessment of Planar Waves” provides background on some of the history of planar waves, which are time-dependent variations of inlet recovery, as well as establishing a hierarchy for categorizing various types of planar waves. It further identifies approaches for establishing compression-component and engine sensitivities to planar waves, and methods for accounting for the destabilizing effects of planar waves. This document contains an extensive list and categorization (see Appendix A) of references to aid both the newcomer and the practitioner on this subject. The committee acknowledges that this document addresses only the impact of planar waves on compression-component stability and does not address the impact of planar waves on augmenter rumble, engine structural issues, and/or pilot discomfort.

This SAE Aerospace Information Report (AIR) provides a methodology for performing a statistical assessment of gas-turbine-engine stability-margin usage. Consideration is given to vehicle usage, fleet size, and environment to provide insight into the probability of encountering an in-service engine stall event. Current industry practices, such as ARP1420, supplemented by AIR1419, and engine thermodynamic models, are used to determine and quantify the contribution of individual stability threats. The statistical technique adopted by the S-16 committee for performing a statistical stability assessment is the Monte Carlo method (see Applicable References 1 and 2). While other techniques may be suitable, their application is beyond the scope of this document. The intent of the document is to present a methodology and process to construct a statistical-stability-assessment model for use on a specific system and its mission or application.

This SAE Aerospace Information Report (AIR) provides a methodology for performing a statistical assessment of gas-turbine-engine stability-margin usage. Consideration is given to vehicle usage, fleet size, and environment to provide insight into the probability of encountering an in-service engine stall event. Current industry practices, such as ARP1420, supplemented by AIR1419, and engine thermodynamic models, are used to determine and quantify the contribution of individual stability threats. The statistical technique adopted by the S-16 committee for performing a statistical stability assessment is the Monte Carlo method (see Applicable References 1 and 2). While other techniques may be suitable, their application is beyond the scope of this document. The intent of the document is to present a methodology and process to construct a statistical-stability-assessment model for use on a specific system and its mission or application.

This document reviews the state of the art for data scaling issues associated with air induction system development for turbine-engine-powered aircraft. In particular, the document addresses issues with obtaining high quality aerodynamic data when testing inlets. These data are used in performance and inlet-engine compatibility analyses. Examples of such data are: inlet recovery, inlet turbulence, and steady-state and dynamic total-pressure inlet distortion indices. Achieving full-scale inlet/engine compatibility requires a deep understanding of three areas: 1) geometric scaling fidelity (referred to here as just “scaling”), 2) impact of Reynolds number, and 3) ground and flight-test techniques (including relevant environment simulation, data acquisition, and data reduction practices).

This document reviews the state of the art for data scaling issues associated with air induction system development for turbine-engine-powered aircraft. In particular, the document addresses issues with obtaining high quality aerodynamic data when testing inlets. These data are used in performance and inlet-engine compatibility analyses. Examples of such data are: inlet recovery, inlet turbulence, and steady-state and dynamic total-pressure inlet distortion indices. Achieving full-scale inlet/engine compatibility requires a deep understanding of three areas: 1) geometric scaling fidelity (referred to here as just “scaling”), 2) impact of Reynolds number, and 3) ground and flight-test techniques (including relevant environment simulation, data acquisition, and data reduction practices).

The turbine-engine inlet flow distortion methodology addressed in this document applies only to the effects of inlet total-pressure distortion. Practices employed to quantify these effects are developing and therefore, periodic updates are anticipated. The effects of other forms of distortion on flow stability and performance and of any distortion on aeroelastic stability are not addressed. The guidelines can be used as necessary to create a development method to minimize the risk of inlet/engine compatibility problems. The degree to which guidelines for descriptor use, assessment techniques, and testing outlined in this document are applied to a specific program should be consistent with the expected severity of the compatibility problem.

The turbine-engine inlet flow distortion methodology addressed in this document applies only to the effects of inlet total-pressure distortion. Practices employed to quantify these effects are developing and therefore, periodic updates are anticipated. The effects of other forms of distortion on flow stability and performance and of any distortion on aeroelastic stability are not addressed. The guidelines can be used as necessary to create a development method to minimize the risk of inlet/engine compatibility problems. The degree to which guidelines for descriptor use, assessment techniques, and testing outlined in this document are applied to a specific program should be consistent with the expected severity of the compatibility problem.

The processes addressed in this Aerospace Information Report (AIR) apply to the acquisition and validation of dynamic total-pressure and distortion data from CFD models simulating turbulent flows in inlets. The results of these processes can be used in the formation of an inlet-flow-distortion methodology that addresses turbine-engine operability assessments.