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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 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).

This document addresses many of the significant issues associated with effects of inlet total-pressure distortion on turbine-engine performance and stability. It provides a review of the development of techniques used to assess engine stability margins in the presence of inlet total-pressure distortion. Specific performance and stability issues that are covered by this document include total-pressure recovery and turbulence effects and steady and dynamic inlet total-pressure distortion.

AIR1419 “Inlet Total Pressure Distortion Considerations for Gas Turbine Engines” documents engineering information for use as reference material and for guidance. Inlet total-pressure distortion and other forms of flow distortion that can influence inlet/engine compatibility require examination to establish their effect on engine stability and performance. This report centers on inlet-generated total-pressure distortion measured at the Aerodynamic Interface Plane (AIP), not because this is necessarily the sole concern, but because it has been given sufficient attention in the aircraft and engine communities to produce generally accepted engineering practices for dealing with it. The report does not address procedures for dealing with performance destabilizing influences other than those due to total-pressure distortion, or with the effects of any distortion on aeroelastic stability.

This Aerospace Information Report (AIR) addresses the subject of aircraft inlet-swirl distortion. A structured methodology for characterizing steady-state swirl distortion in terms of swirl descriptors and for correlating the swirl descriptors with loss in stability pressure ratio is presented. The methodology is to be considered in conjunction with other SAE inlet distortion methodologies. In particular, the combined effects of swirl and total-pressure distortion on stability margin are considered. However, dynamic swirl, i.e., time-variant swirl, is not considered. The implementation of the swirl assessment methodology is shown through both computational and experimental examples. Different types of swirl distortion encountered in various engine installations and operations are described, and case studies which highlight the impact of swirl on engine stability are provided. Supplemental material is included in the appendices.