Browse Topic: Vertical take-off and landing (VTOL)
This paper presents the design, implementation, and validation of an aerial-launch FPV (First-Person View) drone system that was developed to provide a complex environment with flexible deployment and precise delivery capabilities. The integrated system is composed of a hybrid VTOL carrier aircraft, a number of FPV drones, and an aerial mounting / release equipment. Using the AYK-250 platform, the carrier has a vertical take-off and landing function and long-time endurance. In terms of the FPV drones, it is built upon the high performance MARK4 5-inch frame that has high agility and high payload. The release module uses a single-hook point structure with a limit stop. The FPV drones are released stably, and the separation is reliable in flight. Comprehensive flight tests proved all workflows completely, involving carrier take-off, cruise with drones mounted, sequential aerial launch, and subsequent autonomous attitude recovery and route tracking by the FPV drones. The test results confirm the system’s capability for reliable launch from an aerial platform coupled with precise guidance, establishing a credible technical solution for expanding the practical applications of FPV drones in distributed tasks. Results show that our system can be launched via an aerial platform with an accurate guide and is a viable technological solution to spread FPF Drones for operational strategies in a more distributed way.
With the rapid development of China’s logistics and transportation industry, how to reasonably and efficiently use drones to carry out logistics and distribution business under the background of UAM has become a focus of attention for social enterprises. It is urgent to propose a feasible logistics drone take-off and landing sites layout planning method based on reality. The article first explains the principles and connotations of the layout of logistics unmanned aerial vehicle take-off and landing sites, dividing logistics distribution scenarios into three sub scenarios: urban end of pipe distribution, medical material distribution, and short distance logistics transportation. Then, based on strong constraint conditions, preliminary site selection is carried out for each sub scenario. The HRW-Kmedoids algorithm is used to optimize the site selection points for each sub scenario, and the final site selection and alternative points are obtained. The Huangpu District of Guangzhou is taken as a case study for field application. The results show that compared with the traditional method, this method can effectively avoid the actual undeployable area, and it is helpful to reasonably plan the location of the vertical take-off and landing field according to the actual demand, so as to provide some reference for the future vertical take-off and landing field layout.
This paper investigates a sub-scale testing methodology via Froude scaling combined with comprehensive simulation model development to validate Electric Vertical Take-off and Landing (eVTOL) aircraft simulations and disturbance rejection characteristics. Both sub-scale and full-scale quadrotor aircraft were modeled using the Distributed Electric Propulsion Simulation (DEPSim) and the Comprehensive Hierarchical Aeromechanics Rotorcraft Model (CHARM) for simulation analysis. The sub-scale simulation was validated using flight data from the sub-scale model, including frequency sweeps and impulsive gust disturbance tests in the Penn State University (PSU) indoor flight facility. The PX4 control architecture was modeled in DEPSim and implemented in both scale models, using Froude-scaling in the control laws with the limitation that the Electronic Speed Controller (ESC) dynamics were not fully replicated in the simulation. The scaling methodology and control laws were verified through gust response tests and the Hovering turn and hold Handling Qualities Task Element (HQTE) test. The results indicate that the sub-scale flight testing and simulation provide a low-risk and low-cost method to evaluate full-scale flight performance and disturbance rejection properties.
Urban Air Mobility (UAM) vertical takeoff and landing (VTOL) air taxis might exhibit flight motions that are unfamiliar to many passengers. Researchers at the NASA Armstrong Flight Research Center performed a study to identify relationships between rotational flight motion and passenger comfort and acceptance. Fifty test subjects each completed a 20-min passenger experience in a virtual air taxi simulation. Subjects evaluated flight maneuvers with varying levels of rotational motion and indicated their comfort level and willingness to take a real flight with the motion they experienced. Study factors included yaw rate, pitch rate, and roll rate. Participants evaluated four levels of each study factor. The study found linear relationships for each study factor showing a decrease in passenger comfort and acceptance with increased motion. Statistical significance of the results, the possible influence of participants’ backgrounds and experiences, and other potential sources of bias in the study population are discussed.
Integrating safety standards across domains offers significant opportunities to enhance the safety coverage of vertical takeoff and landing (VTOL) aircraft. By integrating various frameworks with advanced digital engineering practices, stakeholders can leverage the strengths of each approach to build a more comprehensive and resilient safety strategy. This paper demonstrates how such integration, particularly within electrical and electronic (E/E) domain, supports robust certification processes and promotes the development of safer, more adaptable VTOL platforms for both civil and defense applications.
The Enhanced Tiltrotor blade, also known as the RGF3 blade, represents a major milestone in Leonardo Helicopters Division's pursuit of advanced rotorcraft technology. Developed at the Yeovil facility in the United Kingdom as part of a dedicated program and in collaboration with the European Clean Sky 2 initiative, it is a key enabler for the Next Generation Civil Tiltrotor Technology Demonstrator. Leveraging the AW609 airframe, the NGCTR integrates a new lateral rotor control system and a V-tail with ruddervators to expand maneuverability and control authority. The RGF3 blade combines aerodynamic efficiency with manufacturability, cost effectiveness, and certification readiness. Innovations include advanced airfoil families, highly swept anhedral tips, dual-redundant anti-ice systems, and full compatibility with legacy components. A comprehensive test campaign—covering structural loads, lightning and bird strikes, icing, and wind tunnel validation—confirmed its robustness and performance. The RGF3 blade embodies Leonardo's vision for high-speed, sustainable, and reliable next-generation rotorcraft.
This paper develops an engineering concept and research framework showing how Cherokee MC2 (Mobile Command Center) and MVP (Mobile Vertipad Platform) can individually, and then as a combined system, resolve key operational and infrastructure challenges facing rotorcraft, eVTOL, VTOL, and UAS missions across civil, commercial, and military contexts. The investigation synthesizes current vertiport / vertipad design guidance, UAM and UTM operational architectures, and recent research on rotor downwash and degraded visual environment hazards to derive a deployable "vertiport node" architecture for austere and time-critical operations. MC2 is treated as the digital and procedural core enabling command, control, communications, data fusion, and manned–unmanned teaming, while MVP is treated as the physical landing interface enabling rapid, load-bearing, illuminated vertical-lift operations without fixed infrastructure. The primary contribution is a traceable topic-to-capability mapping supported by standards and research, plus a modeling, simulation, and optimization workflow to validate safety zones, capacity, scheduling, and resilience. Conclusions identify practical deployment pathways and research gaps for certification-aligned operations.
Cargo-focused autonomous Vertical Takeoff and Landing (VTOL) operations are advancing toward commercialization significantly faster than passenger missions due to a confluence of regulatory pragmatism, technical readiness, and market economics. This paper examines the commercial potential of integrating Artificial Intelligence (AI) and Beyond Visual Line of Sight (BVLOS) control into an Uncrewed VTOL Air Cargo (AI-UVAC) vehicle for dual use military and commercial logistics applications. The Piasecki KARGO II was designed specifically for these missions and is used as the basis for evaluating this capability. This AI-UVAC concept has useful commercial application in the "mid-weight Less than Truck Load (LTL)" freight market for middle-mile delivery of time-sensitive cargo in infrastructure-constrained markets. To validate the advantages of commercial freight orchestration, a multiphase pilot program is conducted to measure the effectiveness of the LogistiWerx Generative AI-Powered Freight Logistics Orchestration platform as integrated in the KARGO II uncrewed BVLOS VTOL developed by Piasecki Aircraft Corporation (PiAC).
This paper shares the complete process and recommendations on how an eVTOL (electric vertical take-off and landing) aircraft is planned, conceptualized, designed, built and tested. The recommendations draw on extensive experience gained from designing multiple eVTOL aircraft and working within the rotorcraft industry. A Lift + Cruise eVTOL aircraft with a wingspan of 8-meter (26.3 ft) is used as a case study to illustrate the whole process.
The United Kingdom's convertible rotorcraft studies of the 1960s and early 1970s represent a systematic effort to combine vertical take-off and landing capability of helicopters with the speed and efficiency of fixed-wing transport aircraft. Conducted primarily by Westland Helicopters under the Short Range Transport (SRT) programme, these investigations explored both tiltrotor and tiltwing configurations for civil and military applications. Early work focused on the WE-01 tiltrotor, conceived as a research and demonstrator aircraft to investigate transition aerodynamics, control integration, and rotor–wing interactions, and subsequently scaled to the larger WE-02, intended for intercity and tactical transport missions. In parallel, Westland pursued the more ambitious WG.22 tiltwing, a 100-seat intercity VTOL transport incorporating high-incidence stall wing technology, large prop-rotors, and mechanically scheduled flight controls to ensure benign handling through transition. Although none of these aircraft were built, the studies addressed aerodynamics, structures, propulsion, flight controls, noise, and socio-economic viability with exceptional depth. Shaping the future through the past, this paper revisits Westland's early involvement in tiltrotor and tiltwing research, with the aim of assessing the technical maturity of these configurations and evaluating their lasting relevance to contemporary vertical lift aircraft design.
In November 2024, Blue Ridge Research and Consulting and Archer Aviation performed acoustic flight tests of the pre-production version of Midnight, Archer Aviation’s full-scale, multirotor electric vertical takeoff and landing (eVTOL) aircraft. The flight tests included concurrent community noise and cabin noise measurements of Midnight across a range of flight conditions. This paper describes the flight test design, measurement instrumentation, and empirical analysis methods used to assess steadiness and repeatability, develop acoustic hemispheres, and identify aeroacoustic sources on Midnight. The acoustic measurements reveal that tonal noise from the propellers is dominant during hover, broadband noise from the propellers and airframe is dominant during cruise, and both tonal and broadband noise components are important during transition. The geometric arrangement of Midnight's propellers influences the acoustic directivity. Source separation using the Vold-Kalman filter reveals that the rear propellers produce higher tonal sound levels than the forward propellers, but broadband noise is the dominant contributor to the overall sound level in forward flight. The paper concludes with lessons learned and recommendations for future acoustic flight tests.
To examine the unsteady aerodynamic environment surrounding vertiports, this research performs high-fidelity Large-Eddy Simulations of two full-scale square cylinders with aspect ratios of 2 and 1, representing prospective urban and vertiport configurations. To ensure realistic conditions, a volumetric momentum-source term is utilized to generate atmospheric turbulence internally within the computational domain. Numerical results reveal severely disturbed flows, with total turbulence intensities reaching a peak of 38% near the first vertiport structure. While the downstream vertiport benefited from a 40% reduction in maximum turbulence intensity due to the sheltering effect of the upstream building wake, the flow in its vicinity still maintains a powerful content. To evaluate operational safety conditions, multiple flight trajectories were analyzed approaching two distinct end-points located 4m and 11m above the center of each vertiport model from three directions: aligned with the wind, against the wind, and sidewise. Based on the evaluation of transient velocity components across these trajectories, and following the Federal Aviation Administration compliant 8:1 approach slopes, this study proposes a robust operational strategy centered on lateral approaches followed by vertical descents from higher altitudes. This maneuver sequence is designed to avoid the severe and sudden gust-induced disturbances prevalent in the immediate vicinity of the vertiport.
This study develops an efficient framework coupling the Lattice Boltzmann Method with the Actuator Line Method to evaluate the unsteady downwash/outwash of eVTOL aircraft. By incorporating a modified Prandtl loss function with geometric smearing correction, the framework accurately predicts velocity profiles and preserves unsteady vortices at lower computational costs than conventional RANS-based simulations. Analyzing three distinct eVTOL configurations sized for identical payload missions reveals that higher disk loading and multi-rotor interactions generate highly asymmetric, localized jet-like outwash structures, contrasting with the symmetric ground-level footprint of single rotor designs. Utilizing a 95th percentile velocity metric, transient peak hazards breach the regulated vertiport Safety Area boundary, extending up to 1.65 times the prescribed baseline limit. These findings demonstrate that time-averaged metrics underestimate physical hazards, highlighting the necessity for future guidelines to mandate configuration specific evaluations utilizing high-resolution unsteady flow data and robust statistical processing.
The aerospace industry is undergoing a profound transformation driven by emerging aviation technologies, including Advanced Air Mobility (AAM), electric vertical takeoff and landing (eVTOL) aircraft, and highly automated flight control systems. These complex systems often feature tightly coupled flight controls and power plants where traditional methods of compliance — relying heavily on physical ground and flight testing — are becoming increasingly impractical due to the vast number of potential interaction cases. To address this challenge, the SAE G-35 Modeling, Simulation, and Training for Emerging Aviation Technologies and Concepts Committee was formed to develop industry consensus standards. This presentation discusses the landmark release of SAE ARP7094, "Recommended Practice for Using Modeling and Simulation for Certification of Aircraft, Products, and Systems" and its role in establishing a standardized, simulation-based path to certification. The SAE G35C group is responsible for developing standards and procedures for using modeling and simulation as a method of compliance for the certification of AAM aircraft similar to the RCbS project conducted in collaboration between EASA, academia and industry in Europe.
We present a nonlinear topology optimization framework for designing crash--tolerant rotorcraft substructures by maximizing plastic work under prescribed crush displacement and volume constraints. The quasi-static response is modeled using a rate-independent elastoplastic formulation to capture path-dependent inelastic deformation of metallic components. A path-dependent adjoint method is developed to efficiently compute sensitivities of accumulated plastic work, revealing a mechanistic decomposition into elastic stiffness, deviatoric response, and yield surface contributions. Optimized 2D and 3D subfloor structures develop emergent plastic hinge networks and distributed deformation paths, significantly enhancing energy absorption compared to uniform designs. The results demonstrate that topology optimization can directly embed energy-dissipating mechanisms into primary rotorcraft structures, providing a practical framework for crashworthy rotorcraft and eVTOL airframe designs.
The Vertical Flight Society (VFS) was founded as the American Helicopter Society, Incorporated (AHS) in 1943. During the first decade, several means were used to communicate Society news and industry news to its members. Until 1952, the management of the Society was primarily through elected volunteers, and executives from the leading helicopter companies typically served as the AHS president. Letters to the Society's members were typed and mailed by the companies to the few hundred early members. In 1950, AHS also partnered with the broader aviation professional society, the Institute of Aeronautical Sciences (IAS), to typeset and publish a column on Society news in its membership magazine and which was then mailed to AHS members. It wasn't until 1953 that the first regular publication, the monthly "NEWS LETTER" was sent to members. This newsletter continued to increase in its length and depth of industry news -- it was renamed Vertiflite in 1963. Although some of this was covered in previous histories of VFS, this paper publishes the details of this period for the first time.
This paper presents several methods for measuring large flow fields in the wake of a helicopter, including wind vanes ("flags"), tufts, BOS (Background Oriented Schlieren), and BOS-velocimetry. The motivation is to develop methods that can map the outwash distribution of VTOL aircraft with strongly asymmetric wakes and identify jets that can be particularly dangerous for bystanders. Each measurement technique is shown to have specific advantages, and the resulting flow fields are demonstrated for the BO105 helicopter in hovering flight in ground effect above a tarmac.
Electric vertical takeoff and landing aircraft impose significantly higher electrochemical and thermal demands on Li-ion batteries than conventional electric vehicles, yet publicly available aging datasets for this application remain limited in applicability, cell technology, and statistical robustness. This study experimentally characterizes the degradation behavior of state-of-the-art Molicel P45B 21700 cells under realistic Urban Air Mobility operating conditions involving high power demand, rapid turnaround, and repeated cycling. Eight cells are subjected to over 3,000 cycles using a fast constant-current charging protocol and a multi-segment constant-power discharge profile. The discharge profile is derived from a representative 7000-lb winged eVTOL with a 20-mile range, requiring normalized power rates of 6.4E during takeoff and landing and 1.6E during cruise. Periodic Reference Performance Tests are conducted to track capacity fade, internal resistance evolution, and energy efficiency. The cells retained over 90% of their initial capacity after 3,270 cycles, while total energy efficiency remained stable at 91%, comprising impedance and hysteresis-driven components of approximately 94% and 97%, respectively. Direct current internal resistance exhibited an initial decrease before stabilizing, yet total discharged capacity increased from 1.81 Ah to 1.84 Ah, indicating aging-driven polarization effects not captured by DCIR. A zero-order equivalent circuit model underpredicts discharged capacity by approximately 4% for fresh cells, increasing to nearly 6% at cycle 3,270 due to unmodeled time-dependent polarization effects. These results demonstrate that while modern Li-ion cells exhibit strong durability under repetitive high-power usage, the accuracy of battery performance prediction is strongly dependent on dynamic impedance effects beyond conventional DCIR-based models.
The rapid expansion of electric aviation and eVTOL operations introduces tightly coupled challenges related to energy‑constrained aircraft design, battery and thermal management, mission planning, and the generation of certification‑relevant evidence. This paper presents an integrated simulation workflow developed by AVL, Unisphere, and blueflite that combines high‑fidelity electric powertrain and battery models with a guidance‑level, digital‑twin‑based 4‑D trajectory simulation driven by historical weather and operational constraints. At each mission time step, the trajectory layer provides time‑resolved environmental and routing conditions, while the system‑level models compute instantaneous power demand, state‑of‑charge evolution, and thermal response, enabling mission feasibility assessment under realistic wind, temperature, and airspace effects. The workflow is calibrated and validated using flight telemetry from blueflite's active eVTOL cargo aircraft development, ensuring alignment between simulation assumptions and real‑world mission execution. The validated framework is subsequently applied to seasonal route studies and large‑scale virtual flight campaigns spanning multiple regions and years, enabling statistically robust assessment of energy margins, thermal behavior, and mission‑duration variability. The results demonstrate how integrated, traceable simulation can bridge conceptual design and real‑world electric flight operations, supporting informed decision‑making by OEMs and operators in aircraft design, validation, and deployment planning.
Electric Vertical Take-Off and Landing (eVTOL) vehicles are emerging as solutions for urban air mobility, but their operation can encounter hazardous aerodynamic conditions such as the Vortex Ring State (VRS), which causes thrust loss and intense vibrations. This study investigates VRS for the Archer Maker tilter propeller by combining numerical simulations using the mid-fidelity solver DUST and the high-fidelity solver OVERFLOW with prior experimental observations. Propeller performance is evaluated through thrust and torque evolution under various descent conditions, while flow fields in the propeller wake at different descent ratios around VRS conditions are evaluated and compared via 2D visualizations. A comparison of results reveals that both numerical approaches are capable of evaluating the performance degradation in correlation with vortex ring formation within specific descent regimes, showing slight discrepancies particularly regarding the descent ratio regime where VRS occurs. A flow field comparison with experimental data validates the multi-fidelity numerical approach, showing the capabilities of both numerical approaches to capture the flow physics mechanisms that lead to the generation of the vortex ring around the propeller disk.
Urban air mobility with electric Vertical Take-Off and Landing (eVTOL) aircraft faces critical micro-weather and infrastructure readiness challenges. This paper proposes a novel socio-technical solution: a tokenized gamification platform that crowdsources hyper-local wind and weather data to enhance operational resilience. We outline the safety gap left by traditional aviation weather systems (METAR, AWOS, ASOS) in urban environments, and leverage community engagement to fill it. The proposed system integrates with Unmanned Traffic Management (UTM) and Safety Management Systems (SMS) to validate user-contributed micro-weather observations, incentivize accurate reporting through tokens and skill-level progression, and feed data into AI-driven forecasts. Early proof-of-concept results indicate improved wind hazard detection and robust user participation. By aligning with emerging regulations (FAA, EASA, DGCA) and test frameworks, this crowdsourced micro-weather ecosystem shows potential to uplift eVTOL safety, build public trust, and support city-scale planning for advanced air mobility.
Rainwater accumulation and management are critical to the safety and reliability of drones and emerging eVTOL aircraft. Current industry practice relies on physical rain testing, such as RTCA DO-160, which defines rainfall conditions for environmental qualification but is costly and difficult to apply during early design stages. This work presents a virtual rainwater assessment framework using Smoothed Particle Hydrodynamics (SPH) simulation in PreonLab. Using an early-stage APELEON cargo drone as a reference case, the method predicts rain impingement, surface runoff, pooling, and ingress under representative rainfall conditions. The meshless SPH approach enables direct simulation of complex geometries and transient interactions without mesh generation, while also supporting rotating components and arbitrary orientations. Results identify key mechanisms governing water transport, including geometry-driven runoff, hinge-related ingress, and droplet deflection from nearby structures. While the total water accumulated on the aircraft can reach on the order of several hundred grams, the amount entering the cargo space remain small. Localized moisture exposure highlights potential durability risks. The framework enables early design evaluation, parametric studies, and rapid assessment of mitigation strategies, supporting simulation-driven development and certification preparation for advanced air mobility systems.
The effects of hover operations near a partial boundary structure were assessed for a free-flying quadrotor platform under both wind-off and wind-on conditions. The partial boundary structure was selected to replicate a building facade or urban vertiport environment, providing a realistic operational context for these free-flight tests. Test points were chosen to investigate operations near the partial boundary wall and edge, and across a range of partial ground effect conditions to capture the progressive onset of ground effect characteristics. Regions of degraded vehicle performance, quantified primarily by rotor thrust coefficient (CT ) and power requirements, emerged near the partial boundary edge. These performance trends were attributed to localized changes in rotor inflow profile, characterized by near-field rotor pressure measurements. Partial ground effect was found to not resemble full ground effect until much of the vehicle had traversed over the partial boundary, with the vehicle airframe and fuselage serving as the primary factor driving the onset and development of ground effect characteristics. Under wind-on conditions, the interaction between the wind freestream and the partial boundary structure significantly shaped vehicle performance and handling qualities. The most adverse handling qualities coincided with regions of peak flow vorticity, highly unsteady flow, and large velocity gradients at the shear layer above the partial boundary.
Emerging technologies in the field of electrified propulsion systems offer a promising solution to reduce the dependence on fossil fuels and improve efficiency. However, the design of high-power density electric machines introduces new challenges, including limited passive cooling potential and the issue of the weight of electric motors. To address these challenges, this paper considers analysis and design methods for high torque-to-weight ratio axial flux motors. A magnetic equivalent circuit model coupled with a lumped parameter thermal network is developed for design space exploration and optimization. This inexpensive analytical model predicts the performance of a single-stator dual-rotor axial flux motor based on geometry, loading condition, and slot and pole pair combination. To enable comparisons against real-world data, the optimization study was demonstrated using the hover mission requirements from the Research Aircraft for eVTOL Enabling techNologies (RAVEN) vehicle to minimize the mass of the motor. In tandem with the analytical model, a higher-fidelity finite element model was also developed, and good agreement between predicted power and efficiency was demonstrated across a range of axial flux motor designs. The lightest weight design that satisfied the hover mission requirements was the 12 pole pair 27 slot (12PP 27S) configuration with a fixed weight of 9.28 kg. The analytic model undersized the output power of the electric motor by approximately 9% across a range of slot and pole pair combinations.
This paper presents the development, optimization, and flight test validation of a Trajectory Control System (TCS)-based flight control system for a tiltwing unmanned aerial vehicle. The TCS is a configuration-independent middle-loop longitudinal controller for vertical takeoff and landing aircraft and is integrated here with explicit model following inner-loop controllers, inverse propulsor models, and a tiltwing-specific control allocation scheme. The resulting flight control system provides coordinated control across vertical flight mode, hybrid flight mode, transition flight mode, and forward flight mode while relying on a concise feedback set and requiring only airspeed from the air data system. The control laws are obtained using a formal constrained optimization framework and transferred directly from simulation to flight without additional on-site retuning. Flight test results from piloted, semi-autonomous, and fully autonomous operations demonstrate stable and predictable behavior throughout the flight envelope, including tight hover performance, simultaneous climb rate and speed tracking in hybrid flight, and successful departure and arrival transitions at multiple speeds. Selected simulation-versus-flight comparisons further show that the nonlinear model captures the dominant trends in the measured response while also identifying specific aerodynamic and transition regime effects that warrant further refinement. Overall, the results demonstrate that the TCS + EMF architecture provides a practical and effective control solution for tiltwing VTOL aircraft.
A methodology was developed and validated to predict total noise from a 1/5th scale eVTOL rotor in hover by coupling 2D-RANS airfoil simulations with the comprehensive code, CHARM, for rotor loading, the acoustic code, PSU-WOPWOP, for tonal noise, and the broadband noise code, UCD-QuietFly, for broadband noise prediction. Improved sectional 2D aerodynamic inputs obtained from 2D-RANS simulations were used throughout the framework, replacing XFOIL-derived inputs to enhance the prediction accuracy of low Reynolds-number effects such as transition and laminar separation bubbles. Predictions were validated against measurements at Virginia Tech. Results indicate that turbulence model selection influences local boundary-layer development and sectional aerodynamic loading, producing modest differences in tonal noise at 4000 RPM (first BPF) and spectral differences of approximately 4 dB in broadband noise, while integrated OASPL shows slight sensitivity to turbulence model choice. At 2000 RPM, broadband noise dominates the total SPL, with transitional models predicting thinner boundary layers and reduced high-frequency trailing-edge noise. In addition, high-fidelity 3D-DDES simulations performed in OpenFOAM capture the mid-frequency noise content that is underpredicted by CHARM. Overall, the combined mid-fidelity broadband noise results and high-fidelity mid-frequency range noise results provide improved agreement with experimental spectra and demonstrate an effective approach for eVTOL rotor noise prediction.
This paper presents the design, development, and successful demonstration of the first-ever ballistically tube-launched tailsitter unmanned aerial system. The vehicle expands upon the capabilities of existing tube-launched systems by simultaneously integrating the hovering capability of a rotary-wing aircraft with the efficiency and speed of a fixed-wing aircraft. To achieve this, the platform's design incorporates a novel coaxial thrust-vectoring propeller system for control in vertical flight and a unique foldable wing design for ultra-compact storage in the launch tube. The aeromechanics of the foldable wings during deployment are studied through a combination of wind tunnel experiments and flight dynamics model simulations, and the results are used to formulate a methodology for executing the ballistic launch. Simulations are also performed to characterize the robustness of the system against asynchronous deployment of the left and right wings. Experimental data, collected from flying a prototype in vertical, horizontal, and transitioning flight, demonstrate the aircraft’s flying performance. The study ultimately culminates with a demonstration of the prototype being rapidly launched from a tube at 25 m/s (56 mph) and autonomously unfolding, stabilizing, and transitioning into self-powered cruising flight.
This work describes the flight control system architecture of the VSDDL VT-03-s Shadow, a cost-effective subscale aircraft used as a testbed for novel flight control schemes. The highlight is the Maneuver Control System comprising the Trajectory Control System, which facilitates Simplified Vehicle Operations, and the Tactical Maneuvering System, which permits more aggressive maneuvering. The control laws permit the selection of both vertical takeoff and landing and conventional takeoff and landing modes of operation. Flight test results shown include transitions between vertical and forward flight modes performed using both Trajectory Control System and Tactical Maneuvering System, limited aerobatic maneuvering performed using the Tactical Maneuvering System, and demonstration of some of the automatic flight functions and capabilities.
Newly designed eVTOL aircraft utilize propellers that operate with a large range of propeller rotation rates. Traditional nomenclature uses nondimensionalization based on the blade tip speed, and input reduction based on a similarity assumption under constant advance ratios. In this study, we explore the validity of this similarity assumption in the context of hover and descent scenarios for a variable pitch eVTOL propeller with rotation rates ranging from 54%-100% of the maximum value. In hover, the relative Reynolds number and Mach number effects are found to be relatively minor. As the axial descent ratio increases, prior to the onset of vortex ring state, the similarity assumption breaks down, and the mean thrust coefficient varies up to ±10% under different rotation rates. A similar breakdown is observed for descent conditions with higher edgewise flow. A detailed exploration shows that the effect is primarily due to relative Mach number effects, which alters the tip vortex wake interaction at the disk, and to a lesser extent changes the loading along the blade. Since the breakdown in the similarity assumption is isolated to a small region of the propeller operating envelope, a surrogate model is developed to preserve the reduced input dimensionality while accounting for the relative tip speed effects in the affected region of the envelope. This is achieved by first generating the surrogate over the full domain, assuming validity of the similarity assumption. A separate high-RPM surrogate correction layer is then built to capture the worst-case tip speed effects in the descent region of the envelope.
Advanced air mobility (AAM) seeks to develop a large-scale transportation system to revolutionize how people live and work, with electric vertical take-off and landing (eVTOL) aircraft serving a central role due to reduced emissions and noise impact. An important aspect for eVTOL aircraft certification is safe urban operations, which require understanding of the response due to aerodynamic disturbances. Experimental data are required to support eVTOL aircraft development with respect to flight dynamics and controllability, as well as design specification development. While flight testing of the full-sized air vehicle will be necessary as part of the certification process, subscale testing offers many advantages with respect to cost and flexibility, in addition to examining operational conditions that one would be reluctant to test in flight at full scale such as emergency conditions. These advantages only may be seen if the underlying scaling principles of flight dynamics / control, aerodynamic interactions, and propulsion-airframe integration are understood. This paper describes initial work towards development of a general subscale testing methodology for eVTOL aircraft flight dynamics and disturbance response characteristics including limited degree of freedom (DOF) and free flight testing. An overview of the initial development work is provided, including discussion of scaling relationships, subscale air vehicle model development, and testing activities focusing on flying qualities and stability / control characteristics.
This paper introduces a novel concept for an AI-powered system designed to manage vertiport takeoffs and landings by proactively addressing the safety-critical issues of downwash and outwash. The proposed system utilizes a stream of live feedback from on-site sensors, combined with a robust predictive modeling engine, to generate optimal, aircraft-specific approach and landing trajectories in real-time. By leveraging a comprehensive database of pre-computed downwash/outwash scenarios for a multitude of UAM aircraft configurations, the AI can accurately predict the unique outwash operational footprint for each individual landing operation, based on the approaching aircraft and under the prevailing conditions. This powerful predictive capability allows the system to calculate and assign an optimal approach vector that actively minimizes risk by directing hazardous airflows away from personnel, active walkways, and other sensitive ground assets. This represents a paradigm shift from static, reactive safety measures to a proactive, intelligent, and performance-based operational model; thereby paving the way for the safe, efficient, and large-scale implementation of UAM aircraft and air taxi operations.
The present study provides a detailed analysis of interactional aerodynamic effects present in the lift and cruise ROMEO demonstrator aircraft. A combination of high-fidelity unsteady Reynolds-averaged Navier-Stokes (URANS) simulations and mid-fidelity actuator disk and actuator line methods is applied to efficiently capture the dominant flow phenomena of a distributed electric propulsion configuration across multiple flight regimes. The mid-fidelity approaches are initially validated against fully-resolved propeller simulations to assess their accuracy and computational benefits. Subsequently, the influence of multi-propeller interactions on lifting arms and tail components is analyzed in hover, followed by an investigation of propeller-airframe interactions during forward and sideward hover maneuvers. A particular emphasis is placed on the modification of local inflow conditions and the subsequent distribution of loads. In the context of sideward flight, the present study explores the effects of asymmetric wake deflection on aerodynamic forces and moments. The findings indicate that propellers- airframe interactions exert a significant influence on aerodynamic performance, stability, and control behavior. This underscores the necessity for effective and precise modeling methodologies in the design of eVTOL systems.
This paper presents an adaptive model predictive control (MPC) framework for nonlinear urban air mobility (UAM) vehicles operating across the full flight envelope. The proposed approach leverages a linear parameter-varying (LPV) representation to update the predictive model online, enabling accurate capture of strongly nonlinear and time-varying dynamics associated with distributed electric propulsion (DEP) eVTOL aircraft. To systematically address the highdimensional and coupled nature of MPC tuning, a multi-objective evolutionary optimization strategy based on NSGAII is employed, incorporating proper normalization of states and control inputs to ensure balanced weighting and meaningful exploration of the design space. The resulting controller explicitly accounts for actuator constraints and enables reconfigurable control allocation for fault-tolerant operation. The framework is evaluated in nonlinear simulations using NASA's Generic Urban Air Mobility (GUAM) model and benchmarked against a robust servomechanism linear quadratic regulator (RSLQR). Results demonstrate that the proposed adaptive MPC achieves improved trajectory tracking and enhanced robustness under both nominal conditions and actuator degradation scenarios, including partial motor failure, while maintaining constraint satisfaction throughout all flight regimes.
Electric Vertical Take-Off and Landing (eVTOL) aircraft are poised to transform urban and regional mobility by offering zero-emission, congestion-free transportation. As regulatory frameworks evolve and advanced air mobility (AAM) gains traction, manufacturers are exploring propulsion strategies that improve range, power delivery, and overall system efficiency. A key challenge in eVTOL development is balancing range with payload capacity. While larger battery packs can extend range, they also increase system weight, reduce payload, and prolong charging times, limiting operational flexibility and turnaround time. Hydrogen fuel cells, supported by liquid hydrogen (LH₂) present a promising alternative for eVTOL propulsion. This study proposes a methodology for optimizing fuel cell propulsion systems tailored to eVTOL applications. A multi-physics modeling framework for eVTOL flight dynamics and propulsion system was developed, representing the target eVTOL configuration. For a defined flight path including vertical takeoff, hover, cruise, and landing, a Genetic Algorithm (GA) based optimization was conducted on propulsion system. The algorithm down-selected battery size, fuel cell stack specifications, and hydrogen tank capacity to meet mission requirements while minimizing propulsion system weight. The modeling framework was also used to evaluate trade-offs between payload and performance as functions of component sizing, battery chemistry and energy distribution strategy.
This study evaluates the predictive accuracy and computational efficiency of a mid-fidelity Lattice-Boltzmann Method (LBM) framework in simulating the complex aerodynamic interactions of a tilting proprotor–wing configuration. The analysis focuses on the tiltrotor conversion maneuver, investigating a range of proprotor tilt angles from forward towards edgewise and vertical flight. To resolve the interactional flow physics, the LBM framework was integrated with two distinct proprotor modeling approaches, an Actuator Line Method (ALM) and an unsteady Actuator Disk Method (ADM), and two wall model boundary conditions, the explicit power-law and Reichardt’s log-law. The computational models were compared with experimental wind tunnel measurements and high-fidelity computational fluid dynamics (CFD) simulations. The ALM significantly outperformed the ADM in capturing discrete tip vortices and wake turbulence, which were critical for resolving the complex flow fields and wing surface pressure distributions. Reichardt’s log-law wall model demonstrated greater physical accuracy over the power-law model by correctly preserving proprotor wake alignment and improving surface pressure predictions. Modifications to the wall models and co-locating both the proprotor and the wing within the finest mesh refinement level enabled the LBM to accurately capture lift coefficient trends and magnitudes across the conversion maneuver. While limitations were identified in resolving leading edge flow attachment at high tilt angles and resolution-sensitive wing drag, this study demonstrated that the LBM-ALM approach with log-law wall model is a highly effective tool for rapid and accurate aerodynamic analysis of tilting proprotor-wing systems.
This paper demonstrates the sizing and optimization of a hybrid-electric multi-tilt rotor configuration of both conventional and vertical takeoff and landing capabilities. The study uses Parametric Energy-Based Aircraft Configuration Evaluator to design and optimize the aircraft. To explore the design space comprising both discrete and continuous design variables, a genetic algorithm is used for optimization. The design variables are not limited to conventional aero-propulsive parameters such as wing loading, aspect ratio, and disk loading. Battery-related parameters such as the maximum permissible depth of discharge, maximum permissible discharge rate, and the number of parallel strings in a battery pack are also considered in this work to study their impact on aircraft gross weight and fuel consumption. The Non-dominated Sorting Genetic Algorithm-II (NSGA-II) optimization framework is used to solve the multi-objective optimization problem, with objectives to minimize the maximum take-off mass and fuel weight. The sensitivity studies showed that higher wing-loading and lower-aspect-ratio designs resulted in lower gross weight. A higher permissible depth of discharge led to lower fuel consumption, despite a slight increase in gross weight. But increasing the number of parallel strings in a battery pack increased gross weight with negligible change in fuel consumption.
This study investigates the acoustic performance of a single rotor representative of those seen on multi-passenger UAM-sized vehicles, focusing on the effects of blade count, disk loading, solidity, and tip Mach number in both hover and propeller operating conditions. Using PSU-WOPWOP and ANOPP2, unweighted and A-weighted overall sound pressure levels (OASPL) are computed in-plane for 2- and 5-bladed rotors across a range of design parameters and operating conditions. Unweighted results show that reducing blade count significantly increases total noise levels (14.1 dB on average) and reduces sensitivity to design parameters. In contrast, A-weighted results demonstrate that broadband noise dominates perceived acoustic performance and shows a decreased sensitivity to blade count (1.9 dBA average difference). Minimum noise levels occur at tip Mach numbers ranging from 0.35-0.45 for unweighted results and 0.4-0.5 for A-weighted results, and are primarily governed by broadband noise sensitivity to disk loading and solidity. The rotor in propeller mode, with axial flow and reduced disk loading, showed less sensitivity to variation in disk loading and solidity than the rotor in hover, indicating weaker acoustic dependence in cruise conditions.
This study evaluates the impact of range extension on gross takeoff weight (GTOW) and energy cost for the NASA Lift+Cruise eVTOL configuration under present and near-term battery technology limitations. A baseline 8,210 lb, 6-passenger vehicle, originally designed for a 75-mile mission at 400 Wh/kg battery energy density, is shown to achieve only 15 miles at a more realistic 200 Wh/kg, largely due to the 20-minute SFAR reserve, which accounts for 64% of total onboard energy. To quantify the penalties of range extension, three sizing strategies are examined: fixed GTOW with payload trade-offs, fixed-geometry overloading, and fully co-scaled vehicle resizing. The co-scaled configurations reveal a strong nonlinear GTOW growth driven by an "adding battery to carry battery" effect, in which increases in GTOW necessitate heavier structure and propulsion, leading to a practical feasibility ceiling near 45 miles. Energy cost per payload-mile is found to be non-monotonic, reaching a minimum near 20-25 miles before increasing due to compounding weight penalties, contrary to trends predicted by fixed-weight analyses. Significant off-design penalties are also observed; operating a 40-mile aircraft on a 10-mile mission incurs a 72% energy cost increase relative to a co-scaled vehicle for 10 miles. Increasing battery energy density by 22.5% (to 245 Wh/kg) reduces the 6-passenger 40-mile design GTOW by 33% (from 13,712 lb to 9,187 lb) and shifts the optimal energy cost point outward to 30 miles. Ultimately, battery energy density is identified as the dominant parameter dictating the vehicle size, weight, performance, and the fundamental operational feasibility of UAM eVTOLs.
A high-fidelity computational study investigates the aerodynamic behavior, flight response, and control effectiveness of a multirotor electric Vertical Take-Off and Landing (eVTOL) configuration. The investigation is organized into two parts. Part I employs an unsteady computational fluid dynamics (CFD) framework coupled with a six-degree-of-freedom (6-DoF) rigid-body dynamics module. Simulations for isolated coaxial rotors and a complete eVTOL isolate rotor aerodynamics and rotor–airframe interactions under constrained kinematics, quantifying lift capability, fuselage download, and a residual nose-up pitching moment arising from fore-aft rotor lift imbalance. Fully coupled 6-DoF free-flight simulations capture the transient vehicle response to a motor failure and recovery sequence during hover. Part II assesses flight control response through a cascade Proportional-Derivative (PD) controller implemented in MATLAB/Simulink across two maneuver cases: hover stabilization and climb rate tracking, which are parameterized using aerodynamic data extracted from the isolated rotor CFD simulation. This decoupled approach enables systematic gain tuning and controller assessment without the computational overhead of fully coupled closed-loop CFD simulations. The results confirm that the CFD–6-DOF framework effectively resolves tightly coupled aerodynamic-dynamic interactions inherent to distributed electric propulsion configurations, and that the cascade PD architecture provides initial control authority assessment across the primary flight axes. These findings establish a foundation for trim strategy development, advanced control law design, and future integration toward robust flight control for urban air mobility operations.
This paper presents the design and simulation-based evaluation of a configuration-independent Trajectory Control System (TCS) for multiple vertical takeoff and landing (VTOL) vehicles. The TCS provides a unified, middle-loop longitudinal control system applicable to lift-plus-cruise, tiltwing, and vectored-thrust configurations. Developed under the Simplified Vehicle Operations (SVO) paradigm, the TCS computes thrust-to-weight commands from normalized vertical and horizontal acceleration using inertial frame force-balance relationships and allocates the resulting trajectory requirements across the available propulsors. The governing TCS equations, propulsor-share framework, and mode structure remain common across configurations, while configuration-specific effects enter only through mode thresholds, inverse propulsor models, and control allocation. The control laws require only attitude, angular rate, fore-aft acceleration, and vertical velocity feedback. Subscale simulation comparisons across three dissimilar VTOL vehicles demonstrate closely grouped longitudinal response characteristics together with broadly comparable departure and arrival transition behavior, supporting the predicted configuration-independent formulation and its suitability for pilot-intuitive operation. These results establish a scalable longitudinal control approach for next-generation VTOL vehicles. The simulation-based findings are further supported by the broader flight test progression of the three configurations reported in prior work.
The increasing use and development of electric vertical takeoff and landing (eVTOL) aircraft and unmanned aerial systems (UAS) for logistics and urban mobility requires acoustic assessment methods that better correlate with human perception and community acceptance than the conventional SPL-based metrics alone. This study presents field-based psychoacoustic measurements of repeated tilt-Octorotor delivery flight operations using a binaural Head and Torso Simulator (HATS). Event segments including lateral approach, takeoff, hover, departure and landing were analyzed using A-weighted SPL, loudness, tonality, fluctuation strength, sharpness, and roughness. Results show strong repeatability across runs and event-dependent signatures within the analysis. Landing produced the highest average loudness (11.65 soneHMS) and sharpness (3.06 acum), while hovering exhibited the highest peak roughness (1.12 asper) and strong tonal persistence. Lateral approach events showed high tonality and sharpness highlighting the directional cues. These findings demonstrate that psychoacoustic metrics provide an improved interpretation of perceived annoyance and support validation workflows for future eVTOL/UAS acoustic design and certification.
A method for evaluation of control derivatives is introduced for the purpose of rapid design evaluation of an electric, fixed-pitch multirotor aircraft during the conceptual pre-design phase. This explicit linearization methodology allows rapid co-design of the vehicle configuration and control allocation using the pseudo-inverse method. A multi-objective design analysis is conducted for a 12 rotor lift + cruise eVTOL configuration subject to hover power requirements, controllability, and tolerance to failure conditions. Generalizable design guidelines are found and presented for the cant and rotor spin direction of the lift + cruise aircraft. The benefits shown include the addition of direct lateral force control derivative, a major increase in yaw control derivative, and reconfiguration to accommodate any Two Engine Inoperative failure conditions. These are achieved through mixing anhedral and dihedral rotor cant within each quadrant of the wing, setting the spin direction so the component of thrust in the yaw axis is additive with the motor reaction torque, and having larger cant angles inboard and closer to the center of gravity. Additional analyses of stability characteristics are performed using DynaPyVTOL, a medium-fidelity flight dynamics analysis tool for any configuration.
In September 2025 a test was conducted at the NASA Ames Research Center's Outdoor Aerodynamics Research Facility to characterize the outwash flow from a hovering rotor. The studied configurations included variations in rotor height above the ground plane as well as variations in rotor speed, thrust, and trim state. Outwash flow was measured using a rake of hot-film anemometers mounted to a semi-autonomous instrumentation cart. Flow measurements were conducted for a single rotor azimuth at distances between 0.6 and 4.0 diameters from the rotor center. In addition to hot-film anemometry, additional flow data was captured using a Background Oriented Schlieren Velocimetry technique that provides a detailed measurement over time of flow velocity in an image plane upstream of the hot-film sensors. The downwash and outwash produced by a lifting rotor in the presence of a ground plane can pose significant risks to life and property in the area of operations. Rotor wake interactions exhibited by modern, multi-rotor aircraft designs can amplify these flows and increase the risk. The rotorcraft community is therefore motivated to better understand rotor downwash and outwash to establish safe operating limits in the vertiport environment.
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