Search Results

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.

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) summarizes prior empirical findings (AIAA 2018-3991; Chati, 2018) to recommend a modified baseline fuel flow rate model for jet-powered commercial aircraft during taxi operations on the airport surface that better reflects operational values. Existing standard modeling approaches are found to significantly overestimate the taxi fuel flow rate; therefore, a modified multiplicative factor is recommended to be applied to these existing approaches to make them more accurate. Results from the analysis of operational flight data are reported, which form the basis for the modeling enhancements being recommended.

The scope of this ARP embraces the description of a configuration for a ground-plane microphone installation that may be used to determine sound pressure levels equivalent to those which would have been measured in an acoustic freefield at the microphone location. The one-third - octave-band center-frequency range over which equivalent freefield sound pressure levels may be obtained is from as low as 50 Hz to at least as high as 10,000 Hz. The specific application of the measurement technique described in this ARP is the determination of the equivalent freefield sound pressure levels of the noise produced by propeller-driven light aircraft, in flight, for sound incidence angles within 30 degrees of the normal to the ground. For larger angles to the normal, additional adjustments may be necessary which are outside the scope of this ARP.

The scope of this ARP embraces the description of a configuration for a ground-plane microphone installation that may be used to determine sound pressure levels equivalent to those which would have been measured in an acoustic freefield at the microphone location. The one-third - octave-band center-frequency range over which equivalent freefield sound pressure levels may be obtained is from as low as 50 Hz to at least as high as 10,000 Hz. The specific application of the measurement technique described in this ARP is the determination of the equivalent freefield sound pressure levels of the noise produced by propeller-driven light aircraft, in flight, for sound incidence angles within 30 degrees of the normal to the ground. For larger angles to the normal, additional adjustments may be necessary which are outside the scope of this ARP.

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. Application is limited to helicopters powered by turbo-shaft 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, precluding the necessity for spectral details. The method prescribes estimates for typical helicopter operations; certain maneuvers may produce noise levels different from those estimated. Estimates are given for the maximum sound levels at 4 ft (1.2 m) height above the ground. For aircraft in forward flight, the estimate is given for an aircraft at an altitude of 500 ft (152 m) on a path directly over the observer.

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.

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.

Satisfactory measurements of noise in personnel-occupied rotorcraft cabins may require test techniques different from those prescribed for other types of aircraft (ARP1323) because rotorcraft operate under significantly different flight conditions. Recommendations of this ARP apply to the recording of acoustical data on magnetic tape and the subsequent processing and analysis of the recorded data.