Passenger Air Vehicles Noise Requirements

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Passenger Air Vehicles Noise RequirementsYahia Ismail, Steven Morris, Martin Kearney-Fischer, and Nikola BaltadjievAurora Flight SciencesCambridge, MA2019 UC Davis Noise SymposiumJacksonville, FL15 March 2019

Overview Aurora Flight Sciences Passenger Air Vehicles (PAV) Current Noise Certification Design for Quieter PAV – Noise Simulation Tools Design for Quieter PAV – Model and Full Scale Validation Noise Metrics – Loudness vs Annoyance What Would be a Subjective Noise Metric for PAV? Summary2

Current Noise CertificationFAA CFR32016 CFR 14, Chapter 1, Part 36Subpart F2016 CFR 14, Chapter 1, Part 36Subpart H2016 CFR 14, Chapter 1, Part 36Subpart KPropeller Driven Small Airplanesand Propeller-Driven, CommuterCategory AirplanesHelicoptersTiltrotors36.501 Noise limits36.801 Noise measurement36.803 Noise evaluation andcalculation36.805 Noise limits36.1101 Noise measurementand evaluation36.1103 Noise limits

Current Noise CertificationFAA CFR2016 CFR 14, Chapter 1, Part 36Subpart F2016 CFR 14, Chapter 1, Part 36Subpart HPropeller Driven Small Airplanes and HelicoptersPropeller-Driven, CommuterCategory Airplanes2016 CFR 14, Chapter 1, Part 36Subpart KTiltrotorsPAV Could be Certified Under Subpart F, H, K or a new Category4

Design for Quieter PAVMeet Noise Requirements Conceptual Design – Preliminary Tools High Fidelity Simulation CFD/CAA Propeller Stand and Wind Tunnel Testing Full Scale Flight Test Validation5Full Use of Noise Simulation and Testing to Achieve Noise Objectives

Conceptual Design ToolsOpen Rotor Noise Footprint Use preliminary noisemodels to make a quickassessment of noisefootprintObserverObserver Different levels of fidelitybased on where we are inthe design phase Different noise metricscan be estimated for agiven mission and vehicleSideline(m)ObserverRange (m)6ObserverContour Plot of Overall Sound Pressure Level Over a Simple missionusing four different levels of fidelity

High Fidelity SimulationRotor Design, Vehicle Interaction, Full Vehicle NoiseSOURCE PREDICTION - Star-CCM /PowerFLOW URANS/DES/LBM CFD – Source Prediction(high computational cost simulation)Example multirotor sourceinteraction analysis from Wave6ACOUSTIC PROPAGATION - Wave6 Ffowcs Williams - Hawkings Model Acoustic Finite Element Analysis Statistical Energy AnalysisFULL VEHICLE NOISE PERFORMANCE High Fidelity Rotor Geometry Design Multirotor Interaction Effects Rotor-Vehicle Interaction Effects Interior Noise7Use State of the Art Noise Simulation to Predict Noise with Accuracy

Component and Wind Tunnel Testing Prop Stand toperform full scalepropellerperformance andacoustics testingBoeing Anechoic Chamber Array ofmicrophones tomeasure rotornoise at severalobserver locations Use of Boeingnoise laboratoryanechoic chamberfor propellerperformance andacoustics testing8Acquired five new class 1sound level meters thatcan acquire /- 1 dBaccuracy, narrowbandfrequency resolution up to 20 kHzWind Tunnel and Propeller Stand Testing To Verify Design

Full Scale Validation and CertificationRace track for flyover Full scale noisevalidation will beconducted using anarray of microphonesto verify vehicle noiselevels for a givenbackground The microphone arraywill comply with CFR14 measurementlocations All measured data willbe corrected forperformance andweather referenceconditions9Flight TrackTest AirplaneSidelineMicrophonesGround StationUnder Flight PathMicrophone ArraySidelineMicrophonesAcquire Data

What Would be a Subjective Noise Metric for PAV or SimilarVehicles?10

Noise Perception Perceived loudnessdepends on frequencycontent of noise source Noise deltas are moreimportant than absolutes Noise backgrounds andinteractions can result incomplex perceptionpattern11Annoyance can be highly subjective, including cognitive bias.

Rural Vs Urban Areas In QuieterRural andSuburbanareas, tonelevels will bedistinguished In Urban areasmany of thetones will bemasked by thebackgroundRural Areas12Urban/Suburban Areas

Current Projected Open Rotor Performance Against UrbanBackground Rotor blade pass frequencies High spikes will be noticeableProjected PAVSpectral Irregularity and Background Noise Has Significant Impact on Perceived Noise13

Noise Requirements for PAV Based on Urban and Suburban background noise, a conventional metric maynot be sufficient for the PAV Whether we use dBA, SEL or EPNdB, background noise has to beconsidered14

Summary15 Aurora Flight Sciences Successfully Completed its First Flight Testing of a Passenger Air Vehicle (PAV) ata test site in Manassas, VA Different Noise Certification Categories (Small Airplane driven propellers, Helicopters and Tiltrotors) thatmay fit the new Passenger Air Vehicles Advanced Noise Simulation Tools from Conceptual to Detailed design Tools, Model Scale Wind Tunnel,Component and Full Scale Noise Validation Flight Testing are used to Design a Quieter Vehicle Background Noise of Different Urban Areas will have significant impact on the Noise Limits Definition forthe new Vehicle Noise requirements or metrics based on Loudness (EPNL) or Annoyance (SEL) need to be defined forthe PAV Category

Questions?16

Summary. 3 Current Noise Certification FAA CFR 2016 CFR 14, Chapter 1, Part 36 Subpart F . 2016 CFR 14, Chapter 1, Part 36 Subpart H . 2016 CFR 14, Chapter 1, Part 36 Subpart K. Propeller Driven Small Airplanes . High Fidelity

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