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At least 109 records · Page 6

Annoyance Model Assessments of Urban Air Mobility Vehicle Operations

As urban air mobility (UAM) vehicles begin to enter service, consideration must be given to vertiport siting and flight routing to help reduce community noise impact and promote adoption by the community. Notwithstanding environmental justice concerns, a possible early strategy is to operate out of existing heliports and fly along established helicopter routes, many of which follow uninhabited waterways and/or roadways (with the thought for the latter that an already noisy ambient environment will mask the sound of the aircraft). However, no prior annoyance model has been fielded that both takes audibility into account and that may be applied to such a real-world strategy. This paper reviews a recently developed annoyance model that includes audibility as a factor and applies it to two flight operations. A simple overflight case is first undertaken to demonstrate the approach. A point-to-point operation in the New York City area is then considered to demonstrate how annoyance varies across an urban soundscape. The cases considered use modeled UAM vehicle noise propagated to a set of ground observers as the signals and either recorded or modeled ambient acoustic data as the maskers.

aircraft community noise↗

Annoyance Model Assessments of Urban Air Mobility Vehicle Operations

As urban air mobility (UAM) vehicles begin to enter service, consideration must be given to vertiport siting and flight routing to help reduce community noise impact and promote adoption by the community. Notwithstanding environmental justice concerns, a possible early strategy is to operate out of existing heliports and fly along established helicopter routes, many of which follow uninhabited waterways and/or roadways (with the thought for the latter that an already noisy ambient environment will mask the sound of the aircraft). However, no prior annoyance model has been fielded that both takes audibility into account and that may be applied to such a real-world strategy. This paper reviews a recently developed annoyance model that includes audibility as a factor and applies it to two flight operations. A simple overflight case is first undertaken to demonstrate the approach. A point-to-point operation in the New York City area is then considered to demonstrate how annoyance varies across an urban soundscape. The cases considered use modeled UAM vehicle noise propagated to a set of ground observers as the signals and either recorded or modeled ambient acoustic data as the maskers.

aircraft community noise↗

RABBIT: A Rapid Low Fidelity BVI Prediction Tool—Comparison and Validation using the NASA RVLT Toolchain

Rotorcraft noise source identification is at the forefront of civil rotorcraft applications with the emergence of the Urban Air Mobility (UAM) market. Blade Vortex Interaction (BVI) has been identified as one key source of noise produced by a rotor. To predict BVI occurrences for various Urban Air Mobility (UAM) configurations, the RApid Blade and Blade-Vortex InTeraction (RABBIT) tool was developed and utilized. The tool is built from a Beddoes Wake Model, and computes variables such as miss distance and BVI angle to calculate an impulse factor, which is able to visualize BVI for a given vehicle and flight condition. A complete checkout of this tool and comparison with CAMRADII and ANOPP2/AARON, is performed. A wake comparison between RABBIT and CAMRADII is presented, and BVI is compared with ANOPP2/AARON’s acoustic pressure time history to verify the tools effectiveness and accuracy. Three NASA Revolutionary Vertical Lift Technology (RVLT) concept vehicles were analyzed with increasing geometric and aerodynamic complexity, including the Quiet Single Main Rotor (QSMR), Side-by-Side, and Quadrotor. An analysis of the results concludes that RABBIT presents a low-fidelity tool that accurately predicts BVI location and intensity for multiple vehicle configurations and various flight conditions.

RABBIT↗

An Initial Vibro-Acoustic Model for Predicting Electric Motor Noise

A system-level tool to predict electric motor noise, suitable for trade studies of eVTOL and UAM aircraft, does not exist. This work describes the ongoing effort to develop such a tool. It utilizes a 3 phase prediction routine that models the electro-magnetic interactions of the electric motor, the resulting structural vibrations of the motor rotor, and finally the acoustic propagation generated by those structural vibrations.

Electric Motor Noise↗

Baseline Assumptions and Future Research Areas for Urban Air Mobility Vehicles

NASA is developing Urban Air Mobility (UAM) concepts to (1) create first-generation reference vehicles that can be used for technology, system, and market studies, and (2) hypothesize second-generation UAM aircraft to determine high-payoff technology targets and future research areas that reach far beyond initial UAM vehicle capabilities. This report discusses the vehicle-level technology assumptions for NASA’s UAM reference vehicles, and highlights future research areas for second-generation UAM aircraft that includes deflected slipstream concepts, low-noise rotors for edgewise flight, stacked rotors/propellers, ducted propellers, solid oxide fuel cells with liquefied natural gas, and improved turbo shaft and reciprocating engine technology. The report also highlights a transportation network-scale model that is being developed to understand the impact of these and other technologies on future UAM solutions.

Antcliff, Kevin↗

Conceptual Design Trade Studies for Acoustic Predictions of the NASA UAM Tiltrotor Reference Vehicle

A toolchain of low-and mid-fidelity tools is applied to NASA’s Urban Air Mobility tiltrotor reference vehicle to quantify trades in sizing, performance, and noise at the conceptual design level. The process includes conceptual sizing, comprehensive analysis, and acoustic analysis to design and analyze versions of the concept tiltrotor with differing design variables. Rotor tip speed is the primary design variable studied, with blade twist, blade taper, and blade number also considered. The noise metrics used are the FAA/EASA certification Effective Perceived Noise Levels for takeoff, flyover, and approach. Certification condition noise is calculated for all conditions in both conversion and airplane flight modes, with airplane mode flight resulting in noise 10-25EPNdB quieter than conversion mode and tip speed variation providing noise reduction up to 9EPNdB.

Acoustic↗

Acoustic Measurements for the Moog S-250 Vehicle in Hover

Acoustic measurements for hover conditions and electric motor noise tests were conducted for the Moog S-250 research aircraft, an RPM-controlled quadcopter-type Urban Air Mobility (UAM) vehicle with four sets of contra-rotating rotors. The objectives of the study included determining the minimum far-field distance, the noise characteristics, and the potential for electric motor noise to contribute to the overall acoustic radiation for the full-scale UAM vehicle. Acoustic data for full-scale aircraft are critical for determining the impact of these vehicles on the surrounding communities. The results showed the far-field was reached by 8.1 single rotor diameters or 2.7 vehicle diameters as defined by the longest tip-to-tip rotor dimension for the vehicle. In hover, the peak acoustic radiation occurred at a declination angle of roughly 29° below the midplane between the upper and lower rotors. The lowest acoustic levels occurred below the aircraft. The electric motor noise studies, conducted with the rotors removed, showed motor noise radiated at shaft orders 17 – 20, whereas rotor noise covered the range of 2 – 24 shaft orders. There was some evidence that electric motor noise was present in previous ground run-up measurements.

Urban Air Mobility Noise↗

Exploration of Near-Term Potential Routes and Procedures for Urban Air Mobility

Urban air mobility is gaining interest as the need for On Demand Mobility in today's congested traffic is becoming high in metropolitan areas. Urban Air Mobility (UAM) is envisioned as a concept to transport passengers and cargo safely and efficiently using innovative aircraft in the urban areas. It is expected to improve mobility for the general public, decongest road traffic, reduce transport time and reduce the strain on existing public transport networks. There exist several challenges to Urban Air Mobility (UAM) such as integration of procedures with airspace and the airport, noise levels that are acceptable to the general public, public safety, public acceptance, vehicle certification, and more. Most of the research in the United States and European skies (DLR - German Aerospace Center) related to urban areas has focused on small UAS (Unmanned Aircraft Systems) flights (NASA's UTM (UAS Traffic Management) research) and their integration with the airspace and building safe operations in densely populated areas. Previous studies on UAM have focused on fast time simulations of the routes that are separated via a separation service and network of routes. Similarly, research in Europe has focused on the approach profile for these innovative aircraft, vertiports and battery life among others. UAM as a part of the On-Demand Mobility effort has provided some guidelines for operations as shown below: Does not require additional ATC (Air Traffic Control) infrastructure; Does not impose additional workload on ATC; Does not restrict operations of traditional airspace users; Will meet appropriate safety thresholds and requirements; Will prioritize operational scalability; Will allow flexibility where possible and structure where necessary. This paper explores potential routes and procedures in a Human-In-The-Loop (HITL) experiment that could be applied in the near-term to allow integration of UAM flights into the airspace as well as a large airport. The airspace that was explored was Dallas Fort Worth (DFW) airspace managed by the DFW East Tower in South Flow only. In addition, Dallas Love Field (DAL) and Addison (ADS) airspace were also part of the testbed. The initial set of routes investigated in this study were published helicopter routes in the DFW area. Figure 1 shows class B airspace in DFW area and the origin/destination city pairs where UAM flights flew along with helicopter routes shown in blue. The research focused on exploring procedures for integrating UAM flights into Class Bravo and Class Delta airspace. Three different communication procedures, evaluated with three different levels of UAM traffic, are shown in Table 1. The current day routes were evaluated with current day communication procedures were explored as the first condition. The current day routes were also evaluated in the second condition with reduced communications, which was assumed due to the presence of a Letter Of Agreement (LOA). The purpose of the LOA was to reduce the verbiage associated with pilots getting clearance to Class B airspace from the controllers, pre-assigning beacons codes to the UAM flights, separate routes by assigning altitudes and speeds to flights going in any one direction. Flights were expected to automatically change frequency when exiting Class B airspace, thus transition points for entry and exit points were also specified in the LOA.

Urban Air Mobility↗

UAM Decision Making

NASA, in collaboration with the industry and FAA, is conducting research on Urban Air Mobility (UAM). UAM introduces unique and evolving operational characteristics unaccounted for within current transportation planning tools. This evolving modality requires a unique and comprehensive tool that integrates new and existing planning methodologies to provide a holistic solution for decision makers. NASA has identified a number of barriers and research areas related to aircraft, airspace, and communities as well as infrastructure requirements. The research will identify requirements related to urban capable aircraft and airspace technologies. While civil aviation authorities are responsible for safety and structure of operations through the air, the local and regional authorities are responsible for decisions related to location of vertiports, helipads, and airports. The implementation of UAM vertiports will consider diverse regional system categories such as weather, airspace restrictions, noise acceptability, surface traffic, availability of power, vertipad locations, routes, impact on surface traffic, safety and risks, economic impact, ingress/egress for electric/hybrid VTOL aircraft, applicable fire codes, evacuation strategy, zoning requirements, emergency preparedness, interactions with surface traffic, and community acceptance. Therefore, regional implementation bodies need a decision making tool to assess systemic dependencies in preparation for UAM impact on the region. We are developing a simulation and modeling tool that allows regional authorities to consider many factors while deciding the location of vertiport and UAM operations. The objective of this paper is to present the conceptual design of a comprehensive decision making tool to assist planning bodies in developing UAM infrastructure. Specifically, the UAM planning tool will simultaneously consider all relevant local/regional considerations to identify for vertiport locations and UAM operations for a region.

Parimal Kopardekar↗

Urban Air Mobility (UAM) Market Study

The Booz Allen Team explored market size and potential barriers to Urban Air Mobility (UAM) by focusing on three potential markets – Airport Shuttle, Air Taxi, and Air Ambulance. We found that the Airport Shuttle and Air Taxi markets are viable, with a significant total available market value in the U.S. of $500 billion, for a fully unconstrained scenario. In this unconstrained best-case scenario, passengers would have the ability to access and fly a UAM at any time, from any location to any destination, without being hindered by constraints such as weather, infrastructure, or traffic volume. Significant legal and regulatory, weather, certification, public perception, and infrastructure constraints exist, which reduce the market potential for these applications to only about 0.5% of the total available market, or $2.5 billion, in the near term. However, we determined that these constraints can be addressed through ongoing intra-governmental partnerships, government and industry collaboration, strong industry commitment, and existing legal and regulatory enablers. We found that the Air Ambulance market is not a viable market if served by electric vertical takeoff and landing (eVTOL) vehicles due to technology constraints but may potentially be viable if a hybrid VTOL aircraft are utilized. The barriers and challenges we characterized in this study can be stratified according to their applicability or potential mitigation through technology as well as market maturity (Figure 1). In the near term, high cost of service will be a key economic challenge. We found potential for significant reduction in service cost through increased vehicle and component efficiency, and automation in a more mature market scenario. Weather conditions also pose a challenge to the UAM market, though there is potential for mitigation of some of these impacts through technology such as sensors enabling operations in low visibility. However, even in a mature market with advanced technology, disruptions are still likely to occur due to weather events such as thunderstorms and strong winds. High density operations will likely stress the current Air Traffic Management (ATM) system in the near term, but technology and new initiatives such as the Air Traffic Management -eXploration project (ATM-X) will enable safe and efficient integration of UAM into the National Airspace System (NAS). Current battery technology creates a barrier in the near term, especially for the Air Ambulance market, as battery weight and extensive recharging times would be needed for these operations. Advancements in battery technology, as well as use of hybrid VTOLs, could significantly reduce this barrier in the longer term. As UAM emerges as a viable mode of transportation in the near term, adverse energy and environmental impacts, particularly noise, may impact community acceptance and potentially persist as the market matures into larger-scale operations. For non-technology related challenges, we found that infrastructure constraints will create a significant barrier to UAM in the near term but could be addressed in the longer term through development and expansion of vertiports. Competition from existing modes of transportation such as ride-sharing (e.g., Lyft, Uber) and ground taxi’s pose a key barrier to UAM in the short term, which will likely evolve into competition from other emerging technologies such as autonomous cars and electric trains in the longer term. Weather events will influence other components of the operation such as passenger comfort (e.g., extreme temperatures, turbulence) and infrastructure (e.g., winter weather causing cracks and degradation in vertiports). There is also potential for these impacts to be heightened in the longer term from the increased frequency of adverse weather such as thunderstorms due to changing climatic conditions. We also found that the public has strong concerns about safety as a passenger in a piloted UAM, including “lasing” of pilots, unruly passengers, and sabotage. They would prefer that all passengers pass through a security screening process before boarding a vehicle. They would also prefer to use UAM for longer regional trips, such as flying from Washington, DC to Baltimore, MD or San Diego, CA to Los Angeles, CA. A longer term automated UAM vehicle market will face challenges due to public apprehension about automation and unmanned operations, and a preference to fly with passengers they know in an autonomous (unmanned) operational scenario.

Rohit Goyal↗

Advanced Air Mobility(AAM) Ecosystems Working Group Briefing Urban Air Mobility Noise Working Group (UNWG) Subgroup 2: Ground & Flight Testing

Overview of Urban Air Mobility Noise Working Group (UNWG) activities of Subgroup 2, responsible for developing Urban Air Mobility (UAM) vehicle ground and flight testing recommendations for those tasked with evaluating the acoustic characteristics of UAM vehicles under development. This topic is being briefed to an audience at the Advanced Air Mobility (AAM) Ecosystems Working Group Meeting (AEWG).

acoustics↗

Noise Measurements from Ground Tests of the Moog SureFly Vehicle

Noise measurements from a ground test of a small vertical lift research vehicle are presented. The proof-of-concept all-electric vehicle called “SureFly” was developed by Moog, Inc. A cooperative effort between NASA and Moog, Inc. has led to one of the first acoustic test datasets from an Urban Air Mobility (UAM) vehicle being developed for passenger and cargo. Results show propeller and possibly motor tones are important for the overall noise levels. The vehicle has four support arms each with a pair of contra-rotating propellers. Noise measurements show higher noise levels from the lower propellers, likely due to inflow distortion from the arms and top propellers. Possible motor noise was identified by calculating harmonics of the line frequency and comparing to the tones in the narrowband acoustic spectra and phased microphone array data. The acoustic far field was found to be about 100 ft away from the vehicle, but additional microphones are needed to provide a better assessment. Results show the presence of modulation for some test conditions. The work reported here is only for ground tests.

Acoustics↗

Noise Measurements from Ground Tests of the Moog SureFly Vehicle

Noise measurements from a ground test of a small vertical lift research vehicle are presented. The proof-of-concept all-electric vehicle called “SureFly” was developed by Moog, Inc. A cooperative effort between NASA and Moog, Inc. has led to one of the first acoustic test datasets from an Urban Air Mobility (UAM) vehicle being developed for passenger and cargo. Results show propeller and possibly motor tones are important for the overall noise levels. The vehicle has four support arms each with a pair of contra-rotating propellers. Noise measurements show higher noise levels from the lower propellers, likely due to inflow distortion from the arms and top propellers. Possible motor noise was identified by calculating harmonics of the line frequency and comparing to the tones in the narrowband acoustic spectra and phased microphone array data. The acoustic far field was found to be about 100 feet away from the vehicle, but additional microphones are needed to provide a better assessment. Results show the presence of modulation for some test conditions. The work reported here is only for ground tests.

Acoustics↗

Urban Aerial Mobility Networks using Amphibious Vertical Takeoff and Landing Vehicles

This study considers novel urban aerial mobility (UAM) networks that address some of the key operator and community acceptance challenges inherent in proposed UAM operations. This paper seeks to examine three possible approaches to improve operator and community acceptance – specifically targeting cost, safety, and noise. First, the conceptual design space will be examined for VTOL amphibious vehicle technologies, including the implications of onwater versus in-flight time/speed. Second, the implications of minimizing community overflights by flying over-water will be examined. Third, the implications of the partial use of onwater, or near-shore/littoral, vertiports on UAM network performance will be examined. This study considers an alternate design trade space for urban aerial mobility systems. A large number of cities in the United States are located near or surround large bodies of water. Many of these same cities are considered to be candidates for metropolitan aerial transportation systems so as to moderate the impact of urban ground-transportation congestion. This paper will expand discussion and study of notional amphibious VTOL vehicles. There is nothing particularly new with regards to helicopters with amphibious takeoff and landing capability. For example, light rotorcraft have been outfitted with pontoons since the 1950s. Larger utility helicopters – used for carrying offshore oil-rig crew – have been designed, with varying degrees of success, to emergency land in rough waters in case of onboard mechanical system failures. The unique difference for the proposed amphibious UAM vehicles, as compared to these earlier amphibious rotorcraft, is that water operation is the norm rather than the exception and that, further, the water-born operation (and design) of such vehicles can be optimized to yield significant economic and operational benefits over solely UAM land-based stations and operations. Various different amphibious UAM networks will be discussed. A first-order set of analyses – employing novel mission metrics – is presented in this paper that will examine the operational performance of these amphibious networks. In particular, amphibious operations might address critical safety and community acceptance issues. An examination of the aerodynamic and hydrodynamic characteristics of amphibious VTOL UAM vehicles will be presented in this paper. One possible conceptual design for an amphibious UAM vehicle is a hybrid synchropter/hydroplane vehicle. As interest in urban aerial mobility grows, it is worthwhile to consider whether or not amphibious vertical takeoff and landing vehicles can play an important role in providing such mobility.

Urban Aerial Mobility↗

Evaluation of Initial and Mid-Term Air Traffic Procedures for Urban Air Mobility Operations

Urban air mobility (UAM) operations are expected to expand in scale over the next several years as novel aircraft types, including electric vertical takeoff and landing aircraft, are certified and begin operations. These new aircraft may increase safety, decrease noise, and lower operating costs compared with helicopters, allowing them to operate in ways existing aircraft do not. It is vital that these expanded operations are compatible with and do not disrupt existing operations or the air traffic management system. To study the ways in which scaled UAM operations can best integrate in the national airspace system, NASA and Joby Aviation partnered to conduct a high-fidelity air traffic controller-in-the-loop study. Building on air traffic procedures used to manage high tempo operations in other parts of the airspace, new procedures, routes, and communications protocols were developed and tested by retired controllers in NASA’s Future Flight Central tower simulation facility. In addition, new cooperative airspace constructs in the form of corridors were developed to understand their potential contributions to even greater scales of operation. The controllers managed traffic scenarios in the Dallas-Fort Worth and Dallas Love Field airports consisting of fleets of up to 100 UAM aircraft operating alongside traditional traffic . Metrics for air traffic controller workload, duration of communications, departure delays, and other measures of allowable aircraft throughput were collected. The analysis indicates that using today’s procedures for initial UAM operations under nominal conditions could enable up to 40 operations per hour to an airport’s central terminal area if that involved crossing a runway and up to 55operations per hour if reaching the central terminal did not involve crossing a runway. Operations at these tempos did not delay or otherwise interfere with simulated runway traffic and were rated acceptable by the air traffic controllers. The new corridor constructs dramatically lowered controller workload in certain circumstances, suggesting they may be effective in further increasing the allowable scale of operations.

Urban Air Mobility↗