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This document describes a practical system for a user to determine observer-to-aircraft distances. These observer-to-aircraft distances can be either closest point of approach (CPA) distances during field measurements or overhead distances during acoustic certification tests. The system uses a digital camera to record an image of the subject aircraft. A method of using commercial software to obtain the distance from such an image is presented. Potential issues which may affect accuracy are discussed.

This SAE Aerospace Information Report (AIR) describes procedures for calculating fuel consumption for civil jet airplanes through all modes of operation for all segments of a flight. Turboprop and piston airplanes, as well as helicopters or unconventional aircraft, are not included in this AIR. The principle purpose of these procedures is to assist model developers in calculating airplane fuel consumption in a consistent and accurate manner that can be used to address various environmental assessments including those related to policy decisions and regulatory requirements. This AIR is intended to directly support the emission calculations documented in AIR5715. The models described in this AIR are intended to be used from the start of the takeoff roll to the end of the ground roll; taxi fuel consumption models are not included. If modelers have access to higher fidelity methods, they should use those methods in lieu of the ones in this AIR.

ARP876 is intended to provide specific recommended procedures for the prediction of gas turbine jet exhaust system noise sources. Procedures are issued as separate sections, to allow for future updating as additional methods, consistent with state-of-the-art, become available.

This Aerospace Information Report provides guidelines for hardware design. Guidelines on such items as engine types, test arrangements, and test purposes that would benefit from the use of an inflow control device during static noise testing are outside the scope of this report.

Recommendations presented in this document are intended primarily for the acquisition of far-field noise data. The test engine is to be appropriately configured and operated so that the sound pressure levels obtained are consistent with the specific objectives of the test. The principal output of the data reduction system is one-third octave band sound pressure levels. However, when appropriate, data may be recorded for purposes of broader or narrower bandwidth analysis.

This document describes analytical methods for calculating the attenuation of the level of the sound propagating from an airplane to locations on the ground and to the side of the flight path of an airplane during ground roll, climbout after liftoff, and landing operations. Both level and non-level ground scenarios may be modeled using these methods, however application is only directly applicable to terrain without significant undulations, which may cause multiple reflections and/or multiple shielding effects. This attenuation is termed lateral attenuation and is in excess of the attenuation from wave divergence and atmospheric absorption.

This method estimates noise for both single and tandem main rotor helicopters except for approach where it applies to single rotor designs only. It does not apply to coaxial rotor designs. Due to lack of available data, application of the method has not been evaluated for application to tiltrotor, or other VTOL configurations, when operating in the helicopter mode. Since there are substantial differences between helicopter rotors included in the data base, and tiltrotor rotors, application to VTOL configurations other than helicopters is not advised. Application is limited to helicopters powered by turboshaft engines and does not apply to helicopters powered by reciprocating engine, tip jets or other types of power plants. It provides noise information using basic operating and geometric information available in the open literature. To keep the method simple, it generates A-weighted sound levels, and Sound Exposure Levels precluding the necessity for spectral details.

ARP876 is intended to provide specific recommended procedures for the prediction of gas turbine jet exhaust system noise sources. Procedures are issued as separate Sections, to allow for future updating as additional methods, consistent with state-of-the-art, become available.

Recommendations presented in this document are intended primarily for the acquisition of far-field noise data. The test engine is to be appropriately configured and operated so that the sound pressure levels obtained are consistent with the specific objectives of the test. The principal output of the data reduction system is one-third octave band sound pressure levels. However, when appropriate, data may be recorded for purposes of broader or narrower bandwidth analysis.

This Aerospace Information Report provides guidelines for hardware design. Guidelines on such items as engine types, test arrangements, and test purposes that would benefit from the use of an inflow control device during static noise testing are outside the scope of this report.

Because of the special circumstances under which these tests were conducted, it is necessary to carefully define the limitations on the validity of the results. The measurements and the comparisons reported here apply only to the specific locations of the noise sources and microphones and only for the specific weather and ground-surface conditions existing at the time of the tests. It cannot be assumed that these conditions are representative of most field measurements of aircraft exterior noise.

ARP876 is intended to provide specific recommended procedures for the prediction of gas turbine jet exhaust system noise sources. Procedures are issued as separate Sections, to allow for future updating as additional methods, consistent with state-of-the-art, become available.