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NASA NTRSDate not supplied

Wind Tunnel-Based Aerodynamic Model Identification for a Tilt-Wing, Distributed Electric Propulsion Aircraft

This paper describes the methodology used to develop a high-fidelity aerodynamic model for the Langley Aerodrome No. 8 (LA-8) tandem tilt-wing, distributed electric propulsion, vertical takeoff and landing aircraft. Electric vertical takeoff and landing (eVTOL) vehicle configurations exhibit aerodynamic characteristics of both fixed-wing and rotary-wing aircraft as well as complex vehicle-specific phenomena, such as propeller-wing interactions and high incidence angle propeller aerodynamics. Consequently, conventional aircraft aerodynamic modeling strategies require modification when applied to eVTOL aircraft. Two novel system identification-based approaches are used to develop an aerodynamic model for the LA-8 aircraft configuration using wind tunnel data collected with design of experiments techniques. The modeling strategies are compared by assessing their predictive performance for validation data acquired separately from the data used to identify the model and are shown to have sufficient predictive capability. Research findings are presented with a discussion of unique eVTOL aerodynamic modeling characteristics and practical strategies to inform future aerodynamic modeling efforts for eVTOL aircraft.

Urban Air Mobility↗

NASA NTRS1977

FY 1978 aeronautics and space technology program summary

Highlights of the aeronautics program include research on aircraft energy efficiency, supersonic cruise aircraft, vertical takeoff and landing aircraft, short haul/short takeoff and landing aircraft, and general aviation aircraft. The space technology program includes work on space structures, propulsion systems, power systems, materials, and electronics.

Source record↗

NASA NTRS1988

Aircraft technology opportunities for the 21st Century

New aircraft technologies are presented that have the potential to expand the air transportation system and reduce congestion through new operating capabilities, and at the same time provide greater levels of safety and environmental compatibility. Both current and planned civil aeronautics technology at the NASA Ames, Lewis, and Langley Research Centers are addressed. The complete spectrum of current aircraft and new vehicle concepts is considered including rotorcraft (helicopters and tiltrotors), vertical and short takeoff and landing (V/STOL) and short takeoff and landing (STOL) aircraft, subsonic transports, high speed transports, and hypersonic/transatmospheric vehicles. New technologies for current aircraft will improve efficiency, affordability, safety, and environmental compatibility. Research and technology promises to enable development of new vehicles that will revolutionize or greatly change the transportation system. These vehicles will provide new capabilities which will lead to enormous market opportunities and economic growth, as well as improve the competitive position of the U.S. aerospace industry.

Albers, James A.↗

NASA NTRS1998

Flight Research at Ames: Fifty-Seven Years of Development and Validation of Aeronautical Technology

This NASA special publication presents a general overview of the flight research that has been conducted at Ames Research Center over the last 57 years. Icing research, transonic model testing, aerodynamics, variable stability aircraft, boundary layer control, short takeoff and landing (STOL), vertical/ short takeoff and landing (V/STOL) and rotorcraft research are among the major topics of interest discussed. Flying qualities, stability and control, performance evaluations, gunsight tracking and guidance and control displays research are also presented. An epilogue is included which presents the significant contributions that came about as a result of research and development conducted at Ames.

Borchers, Paul F.↗

NASA NTRS1989

Future Civil Aircraft and Technologies

New aircraft technologies are presented that have the potential to expand the air transportation system and reduce congestion through new operating capabilities while also providing greater levels of safety and environmental compatibility. These new capabilities will result from current and planned civil aeronautics technology at the NASA Ames, Lewis, and Langley Research Centers and will cover the complete spectrum of current aircraft and new vehicle concepts including rotorcraft (helicopters and tilt rotors), vertical and short takeoff and landing (V/STOL), and short takeoff and landing (STOL) aircraft, subsonic transports, high-speed transports, and hypersonic/transatmospheric vehicles. New technologies will improve efficiency, affordability, safety, and environmental compatibility of current aircraft and will enable the development of new transportation system. The new capabilities of vehicles could lead to substantial market opportunities and economic growth and could improve the competitive position of the U.S. aerospace industry.

Albers, J.↗

NASA NTRS2006

Cost Analysis for Large Civil Transport Rotorcraft

This paper presents cost analysis of purchase price and DOC+I (direct operating cost plus interest) that supports NASA s study of three advanced rotorcraft concepts that could enter commercial transport service within 10 to 15 years. The components of DOC+I are maintenance, flight crew, fuel, depreciation, insurance, and finance. The cost analysis aims at VTOL (vertical takeoff and landing) and CTOL (conventional takeoff and landing) aircraft suitable for regional transport service. The resulting spreadsheet-implemented cost models are semi-empirical and based on Department of Transportation and Army data from actual operations of such aircraft. This paper describes a rationale for selecting cost tech factors without which VTOL is more costly than CTOL by a factor of 10 for maintenance cost and a factor of two for purchase price. The three VTOL designs selected for cost comparisons meet the mission requirement to fly 1,200 nautical miles at 350 knots and 30,000 ft carrying 120 passengers. The lowest cost VTOL design is a large civil tilt rotor (LCTR) aircraft. With cost tech factors applied, the LCTR is reasonably competitive with the Boeing 737-700 when operated in economy regional service following the business model of the selected baseline operation, that of Southwest Airlines.

Coy, John J.↗

NASA NTRS2018

Urban Air Mobility Airspace Integration Concepts and Considerations

Urban Air Mobility (UAM) - defined as safe and efficient air traffic operations in a metropolitan area for manned aircraft and unmanned aircraft systems - is being researched and developed by industry, academia, and government. Significant resources have been invested toward cultivating an ecosystem for Urban Air Mobility that includes manufacturers of electric vertical takeoff and landing aircraft, builders of takeoff and landing areas, and researchers of the airspace integration concepts, technologies, and procedures needed to conduct Urban Air Mobility operations safely and efficiently alongside other airspace users. This paper provides high-level descriptions of both emergent and early expanded operational concepts for Urban Air Mobility that NASA is developing. The scope of this work is defined in terms of missions, aircraft, airspace, and hazards. Past and current Urban Air Mobility operations are also reviewed, and the considerations for the data exchange architecture and communication, navigation, and surveillance requirements are also discussed. This paper will serve as a starting point to develop a framework for NASA's Urban Air Mobility airspace integration research and development efforts with partners and stakeholders that could include fast-time simulations, human-in-the-loop (HITL) simulations, and flight demonstrations.

airspace integration↗

NASA NTRS2018

Mid-Fidelity Computational Fluid Dynamics Analysis of the Elytron 4S UAV Concept

The Elytron 4S Unmanned Aerial Vehicle (UAV) Concept was developed to combine the advantages of fixed- and rotary-wing technology. The 4S Concept is a box-wing configuration with rotors mounted on a centrally located tiltwing. The UAV is intended to be capable of both conventional takeoff and landing (CTOL) and vertical takeoff and landing (VTOL), and is envisioned to excel in UAV performance because of the combined efficiency of fixed-wing aircraft and the hover and VTOL capabilities of regular drones or quadcopters. A mid-fidelity Unsteady Reynolds-Averaged Navier-Stokes (URANS) approach using Rotorcraft CFD (RotCFD) is performed to analyze and characterize the performance of the aircraft. The flow field is coupled with a rotor model based on blade-element momentum theory to model the 4S UAV rotors. Turbulence is modeled using a realizable k- turbulence model with special wall function. The code is used to generate aerodynamic forces and moments on the body at cruise conditions, and during VTOL. The results and their uncertainties are characterized, and an angle- of-attack and sideslip sweep are computed, both with and without rotors on. Simulations are compared with the wind tunnel tests in the 7- by 10-Foot U.S. Army Wind Tunnel at NASA Ames Research Center, performed in 2017. Results show promising comparison with experimental data, despite a late change in rotor size and rudder size of the physical model that cause the expected deviations from the simulation. A slight change in the net thrust value, when rotors are modeled, is observed because of the rotor diameter increase on the physical model. A noticeable difference in the directional stability was observed because of the increased rudder surface and added strakes. These changes were implemented to improve on the design as simulated, which is observed in the results. The simulation results paved the way to the first successful flight of the UAV Concept.

Koning, Witold J. K.↗

NASA NTRSDate not supplied

Challenges in Securing UAM Operations

Urban air mobility (UAM) is a concept that proposes to develop short-range, point-to-point transportation systems in metropolitan areas using vertical takeoff and landing (VTOL) or short takeoff and landing (STOL) aircraft to overcome increasing surface congestion. To realize the potential of UAM, an assurance of cybersecurity is critical for public acceptance. Cybersecurity has come to the forefront highlighting the need to protect these networks and systems from cyberattacks. The growth in the development of UAM systems, and the associated data exchange and service interactions will create abundant challenges due to numerous types of cybersecurity attacks. As these threats evolve, the UAM cybersecurity capabilities must adapt to these changes as well.

Urban Air Mobility,↗

NASA NTRSDate not supplied

Challenges in Securing the Future of Air Travel

UAM↗

NASA NTRSDate not supplied

A Blockchain Case Study for Urban Air Mobility Operational Intent

The next generation of aerial passenger and cargo transportation may leverage the concept of Urban Air Mobility (UAM). UAM is a concept that proposes to develop short-range, point-to-point transportation systems in metropolitan areas using vertical takeoff and landing (VTOL) or short takeoff and landing (STOL) aircraft to overcome increasing surface congestion [1]. The UAM concept leverages a decentralized service-based architecture for airspace solutions. Within the environment, UAM operators work collaboratively to manage aerial vehicles in the urban environment. Providers of Services for UAM (PSU), UAM operators, and Supplemental Data Service Providers (SDSP) provide services to support flight operations within the UAM environment. Also, various views of UAM flight information are provided to the public and public safety entities [2]. The Federal Aviation Administration (FAA) can coordinate flight information between the FAA controlled National Airspace System (NAS) and the UAM environments through the FAA-Industry Data Exchange Protocol (FIDXP). To realize the potential of UAM, an assurance of cybersecurity is critical for public acceptance. Cybersecurity has come to the forefront highlighting the need to protect these networks and systems from cyberattacks. The growth in the development of UAM systems, and the associated data exchange and service interactions will be at risk due to numerous types of cybersecurity attacks. As these threats evolve, the UAM cybersecurity capabilities must adapt to these changes as well [3]. This research focuses on the secure data exchange and storage of this decentralized UAM environment to address these challenges. This research intends to leverage a permissioned blockchain approach to address cybersecurity threats that may impact a UAM environment. Blockchain technologies can be used for tracking transactions and verifying negotiated agreements between stakeholders in the NAS environment. For example, the record of the submitted flight plan and the approved flight plan could be verified using the Blockchain-based immutable ledger.

UAM↗

NASA NTRSDate not supplied

Overview of an Exploratory, Real-Time, Multi-Pilot Simulation Study of Early eVTOL Operations at Non-Towered Vertiports

This paper provides a report out on an exploratory, multi-aircraft/multi-pilot, real-time simulation study conducted by NASA of early commercial powered-lift, Urban Air Mobility (UAM) operations at a non-towered vertiport. As used in this paper, vertiport refers to the primary ground and airspace elements facilitating the takeoff and landing of electric vertical takeoff and landing (eVTOL) aircraft with central emphasis on a vertipad, i.e. the physical touch-down and lift-off area and surrounding approach , departure, local pattern procedures. The study, known as the Piloted UML-2 ConOps Study (PUCS), had two high-level goals. The first goal was providing preliminary insights and observations relevant to the piloting and flight operations of early, commercial UAM operations aligned with the initial stage of the FAA’s Advanced Air Mobility (AAM) Implementation Plan and the second level NASA’s UAM Maturity Level (UML) scale. The second goal was evaluating a novel, medium-fidelity, extensible, many-pilot, real-time simulation capability known as the UAM Flyers developed by NASA. The Flyers are intended to allow rapid development, screening, evaluation, and demonstrations of potential Concepts of Operation (ConOps) for UAM flight operations and airspace management in a modular and low-cost, real-time, human-in-the-loop rapid simulation prototyping environment. For this study, ten Flyer cockpits were configured to evaluate flight operations through a non-towered vertiport with pilot interfaces and displays (external and in-cockpit) appropriate for operations under visual flight rules (VFR) and employing flight and communication procedures representative of current operations at non-towered airports. The presented results include an achieved operational tempo; durations of individual flight tasks for approaches and departures; off-nominal events and triggers; and pilot comments regarding potential procedural and technology improvements.

Urban Air Mobility↗

NASA NTRSDate not supplied

Simulating Secure Data Exchange and Storage for Urban Air Mobility Environments

Urban Air Mobility (UAM) defines an environment for managing operations of vertical takeoff and landing (VTOL) and short takeoff and landing (STOL) vehicles in an urban environment. Within a UAM environment, UAM operators manage fleets of vehicles, relying on Providers of Services for UAM (PSUs) for managing flights in a region of airspace. Flight plan deconfliction is primarily performed by the Discovery and Synchronization Service (DSS), and the Federal Aviation Administration (FAA) maintains control over the UAM space via the FAA-Industry Exchange Protocol (FIDXP). UAM is a federated environment with many different entities owning and operating vehicles, PSUs, and other services. These entities often need to interoperate or access data generated by other organizations. This paper demonstrates the feasibility of using blockchain to facilitate a secure data exchange and storage for this flight information in a UAM environment. In particular, this paper is focused on flight plans and telemetry data. A blockchain network was developed with a set of smart contracts for managing relevant flight data. Hyperledger Fabric was chosen as it is performent, scalable, and allows organizations to reuse existing public key infrastructure (PKI) for identity management. A set of simulated UAM services were also developed. These services propose flight plans and negotiate with other UAM services for airspace access. All interactions between UAM services, as well as vehicle telemetry data, is recorded onto the blockchain. Vehicle telemetry data is generated by a vehicle flight simulation service. This paper successfully demonstrates the feasibility of using blockchain as a secure data exchange and storage mechanism in a UAM environment.

UAM↗

NASA NTRSDate not supplied

Overview of an Exploratory, Multi-Pilot Simulation Study of Early eVTOL Operations at Non-Towered Vertiports

Urban Air Mobility↗

NASA NTRS1971

Ground noise measurements during landing, take-off, and flyby operations of a four-engine turbopropeller STOL airplane

Noise measurements were obtained for a four-engine turbopropeller STOL airplane during a Federal Aviation Administration flight evaluation program at the National Aviation Facilities Experimental Center. These noise measurements involved landing-approach, takeoff-climbout, and flyby operations of the airplane. A total of 13 measuring positions were used to define the noise characteristics around a simulated STOL port. The results are presented in the form of both physical and subjective measurements. An appendix is included to present tabulated values of various subjective reaction units which may be significant for the planning and operation of STOL ports. The main source of noise produced by this vehicle was found to be the propeller, and noise levels decrease generally in accordance with the inverse-distance law for distances up to about 457 meters. For similar slant ranges, somewhat lower noise levels were experienced during flyby than during takeoff or landing.

Hilton, D. A.↗

NASA NTRS1984

Evaluation of a real-time predictive guidance law for landing VTOL aircraft at sea

A piloted simulation evaluation was conducted to assess the merits of a predictive lull/swell guidance law for landing a vertical takeoff and landing aircraft at sea. Two cases were evaluated. The first was performed by the pilot without the aid of the lull/swell guidance indicator, which indicates a landing opportunity. The second was performed in a similar manner with the aid of the guidance indicator. The pilot was instructed to use the guidance indicator only as a landing aid. The results indicated the pilots were able to visually determine ship lulls and swells prior to landing. However, use of the lull/swell guidance resulted in increased pilot confidence in the existence of a landing opportunity, which resulted in significantly shorter hover waiting times prior to landing. The performance of the lull/swell guidance was conservative, in that it forecast the onset of deck lulls and swells later than the pilot could detect them, but with greater reliability and therefore greater pilot confidence. In no instances did the guidance algorithm predict a false ship lull with which the pilot did not agree.

Paulk, C. H., Jr.↗

NASA NTRS1988

A review of technologies applicable to low-speed flight of high-performance aircraft investigated in the Langley 14- x 22-foot subsonic tunnel

An extensive research program has been underway at the NASA Langley Research Center to define and develop the technologies required for low-speed flight of high-performance aircraft. This 10-year program has placed emphasis on both short takeoff and landing (STOL) and short takeoff and vertical landing (STOVL) operations rather than on regular up and away flight. A series of NASA in-house as well as joint projects have studied various technologies including high lift, vectored thrust, thrust-induced lift, reversed thrust, an alternate method of providing trim and control, and ground effects. These technologies have been investigated on a number of configurations ranging from industry designs for advanced fighter aircraft to generic wing-canard research models. Test conditions have ranged from hover (or static) through transition to wing-borne flight at angles of attack from -5 to 40 deg at representative thrust coefficients.

Paulson, John W., Jr.↗

NASA NTRS1990

Lateral-directional stability and control characteristics of the Quiet Short-Haul Research Aircraft (QSRA)

The results are presented of flight experiments to determine the lateral-directional stability and control characteristics of the Quiet Short-Haul Research Aircraft (QSRA), an experimental aircraft designed to furnish information on various aerodynamic characteristics of a transport type of airplane that makes use of the upper-surface blown (USB) flap technology to achieve short takeoff and landing (STOL) performance. The flight program designed to acquire the data consisted of maneuvers produced by rudder and control-wheel inputs with the airplane in several configurations that had been proposed for landing approach and takeoff operation. The normal stability augmentation system was not engaged during these maneuvers. Time-history records from the maneuvers were analyzed with a parameter estimation procedure to extract lateral-directional stability and control derivatives. For one aircraft configuration in which the USB flaps were deflected 50 deg, several maneuvers were performed to determine the effects of varying the average angle of attack, varying the thrust coefficient, and setting the airplane's upper surface spoilers at a 13 deg symmetrical bias angle . The effects on the lateral characteristics of deflecting the spoilers were rather small and generally favorable. The data indicate that for one test, conducted at low thrust (a thrust coefficient of 0.38), compared with results from tests at thrust coefficients of 0.77 and larger, there was a significant decrease in the lateral control effectiveness, in the yaw damping and in the directional derivative. The directional derivative was also decreased (by about 30 percent) when the average angle of attack of the test was increased from 3 to 16 deg.

Stephenson, Jack D.↗