Browse Topic: People and personalities
This study evaluates the operational impact of multiple concurrent spatialized auditory cues during high-workload rotorcraft missions. A controlled, within-subject flight simulation experiment was conducted in which military-qualified rotorcraft pilots completed continuous multi-objective missions including formation flying, visual asset detection, collision avoidance, and emergency landing tasks. Each mission was flown under spatialized (3D) and non-spatialized (2D) audio rendering conditions while cue composition remained constant. Preliminary results indicate that under complex, formation-dominant workload conditions, pilots consistently prioritized visually anchored tasks and largely deprioritized auditory cue information regardless of spatial rendering. Collision avoidance cues did not produce observable evasive responses, and reported cue trust remained low without prior training. Although limited performance improvements were observed in isolated conditions, participants reported consciously suppressing audio cues. These findings suggest that effective integration of spatial audio requires structured training, procedural embedding, and deliberate workload redistribution rather than perceptual enhancement alone.
A 4-rotor uninhabited air vehicle is described, with a primary mission of supporting personnel fighting wildfires. The paper demonstrates the use of technical design tools for a small Uninhabited Aircraft System (sUAS). A description of the design process is provided, including developing requirements, identifying constraints, the software tools employed, and examination of results. The vehicle is capable of delivering more than 20 kg of supplies to a delivery point 10 nm away while penetrating 30 kt winds. The sized vehicle is transportable in a medium-duty pickup truck and can be picked up and moved for ground handling by one or two individuals. The vehicle information will be publicly released for NDARC software users. Future work will examine other requirements, such as maneuvering and gust rejection.
A quantitative understanding of the perceptual elements of handling qualities rating brings us to the heart of pilot control. In previous work it was shown that pilot induced oscillation ratings (PIORs) were a strong linear function of the closed loop dominant mode decay rate of the modeled pilot-vehicle system. While PIORs are based solely on the degree that oscillation degrades the task, the handling qualities rating (HQR) scale employs aggregate performance criteria and three apparently distinct sensations: workload, compensation, and controllability. However, in practice the pilot must modulate control in real time based on an instantaneous sense of performance. It is incumbent to model these four perceptions if the objective is to reproduce the manner and resolution with which the pilot assigns HQRs. The current work examines the same offset landing task that was conducted in two separate piloted studies: 1) Flight, using the Calspan variable stability NT-33A aircraft, and 2) Fixed and motion-based simulation, using the NASA Vertical Motion Simulator (VMS). The substantial difference in actual pilot ratings between the inflight and simulation studies was unexpected and hitherto could not be accounted for. The perception-based theory developed herein predicted pilot ratings that matched well the two studies’ ratings. It is demonstrated how acceleration washout (employed in most motion simulators) could impede the vestibular system from sensing decay rate and require the visual system to be used for primary control. A biomechanical feedback model is developed that computes dynamic limb tension from the neuromuscular system which is then integrated with the feel system to produce a stick force disturbance in response to aircraft motion. This model is flight-data-validated, and the neuromuscular mode’s decay rate was used as a metric to successfully predict the occurrence of roll ratchet (a higher frequency PIO phenomenon).
This paper details the development of a tailsitter unmanned aerial system (UAS) that has the potential to be airlaunched in the near future. By simultaneously integrating air-launch capability with both rotary-wing vertical flight and fixed-wing horizontal flight, the vehicle can be rapidly deployed, perform hovering flight, and achieve high-speed and efficient cruising flight. The aircraft prototype has a mass of 1 kg (2.2 lbs) with wings that can fold to allow the aircraft to fit inside a 6-inch launch tube. A coaxial propeller with vectored thrust is used for control in vertical flight, and a unique avian-inspired wing-folding mechanism is used for stowing and deploying the wings. The aerodynamic design was characterized through a series of wind tunnel experiments, propeller tests, and flight dynamics simulations. High-fidelity simulations of vehicle dynamics validated its air-launch capability and flight tests performed with the prototype demonstrated the ability of the aircraft to perform hovering, transitioning, and fixed-wing cruising flight. To date, this aircraft has achieved speeds of up to 130 km/hr (81 mph), and range up to 10 km (6.2 miles).
The complex and turbulent ship airwakes make shipboard rotorcraft launch and recovery difficult for even the most seasoned pilots. One of the main challenges to using flight simulation to train pilots is the real-time accurate prediction of the ship airwake. A real-time, accurate methodology that is able to operate on personal computers without computational meshing is being developed for Advanced Air Mobility (AAM) applications. The early success of this novel approach indicates that it may be well-suited to meet the challenge of dynamic interface (DI) applications as well. To explore this, a novel reduced-order model (ROM) to represent unsteady airwakes for shipboard operations is underway. This ROM will be integrated into an ocean-based representative environment model (REM) to close the gap in real-time simulations without significant computational investment. The ROM effort presented here specifically investigates which superstructure wake characteristics are dominant in different regions where flight operations are conducted. Canonical ship geometries that have been significantly studied experimentally and computationally provide the substantiation of this approach. Evaluation of the accuracy of the approach is presented, correlated with Lattice-Boltzmann simulations, theoretical and experimental data.
Rotorcraft continue to experience higher fatal accident rates compared to fixed-wing aircraft, primarily due to low altitude flight operations and reduced situational awareness in complex environments. A critical factor is the limited availability of accurate, up-to-date information on helipads and surrounding obstacles - such as trees, poles, and buildings - that pose significant risks during takeoff and landing. Existing resources, including the Federal Aviation Administration's heliport registry, are often outdated and incomplete, particularly for private or state-operated sites, and fail to report nearby obstacles. This lack of up-to-date data is largely due to privacy restrictions at certain locations and the high cost associated with comprehensive obstacle surveys. To address this challenge, we develop a deep learning (DL) framework that automatically detects helipads and nearby obstacles from high-resolution satellite imagery. Our approach combines Mask R-CNN for precise pixel-level helipad segmentation with Grounding DINO, a zero-shot vision-language model that identifies obstacles using flexible text prompts (e.g., "Pole", "Tree") without task-specific training. This text-guided, scalable detection method adapts to diverse and evolving operational settings. We validate our framework across helipads in the United States, and demonstrate strong performance in both helipad localization and obstacle detection. In addition, we build a web-based application that automates image processing, updates incorrect heliport coordinates, and provides obstacle reports. This work aims to enhance aviation safety, modernize infrastructure records, and deliver scalable tools to the aviation and machine learning communities.
The vertical flight industry is on its way to a transformative era, with autonomous technologies set to alter aerial vehicle operations. While it seems certain that fully autonomous helicopters will eventually be deployed for a variety of missions, some high-stakes situations—like medical evacuations (MEDEVAC)—will for the foreseeable future demand human participation in the form of Emergency Medical Care-giving Crew. This study describes the testbed built to run and investigate hypothetical future situations in which a helicopter is autonomously piloted while a human medic with no aviation training, subjected to aviation and medical emergencies, manages patient care onboard. A total of 22 participants, with emergency medical technician certification, nursing or a medical board certification, were invited to run and evaluate the use of AI pilot (AP) in different scenarios of medical evacuation under the following emergencies: medical, empty fuel tank, pressure sensor miscalibration, and engine failure. A comprehensive evaluation of both objective and subjective performance metrics revealed that novice medical professionals could effectively execute medical evacuation operations in conjunction with an AI pilot, even during unforeseen circumstances. The analysis of response times unveiled distinct perspectives on how medics perceive and manage various emergency situations when an AP functions as a collaborative and effective team member.
Research into the feasibility of a scaled rim-drive propulsion product to enable ultra-heavy vertical lift (UHVL) is ongoing at the University of South Carolina in partnership with KRyanCreative, LLC, a start-up aerospace small business. The research team is advancing a superconductive design concept for a rotor system that delivers significant performance gains and flight envelope expansion disruptive to the vertical lift transportation sector. The team has conceived a novel electric tip-driven ducted propulsor to guide architectural and engineering investigations that improve hover and acoustic performance over current practice without penalty to weight and cost. This paper summarizes the data and assumptions that emerge from the systems engineering process of requirements decomposition for product realization. Requirements are categorized as to whether they are explicit (programs of record) or implied (comparable business case or as an alternative to a program of record). Risk reduction enroute to technical feasibility is addressed with a methodology that applies predictive analytics aided by artificial intelligence that will accelerate prototype fabrication by 2030 and fast track market incentives for multiple aviation technologies.
Several efforts have been made to develop Flight Test Maneuvers for Handling Qualities evaluations, aimed at quantifying the effects of vehicle characteristics and assistance systems on a Helicopter Air-to-Air Refueling mission profile. However, these Flight Test Maneuvers have not achieved widespread adoption, likely due to the substantial logistical challenges associated with tanker deployment. Depending on a tanker aircraft not only incurs significant costs but also requires extensive organizational effort and prior testing, before Handling Qualities can be evaluated for the aerial refueling capabilities of a new rotorcraft design. Additionally, these available Flight Test Maneuver setups are not standardized or widely applied to the same degree as Mission Task Elements of the Aeronautical Design Standard, which limits repeatability and comparability. A new approach is proposed to address these limitations by introducing a repeatable, standardized method to reveal Handling Qualities deficiencies considering a worst-case situation of Helicopter Air-to-Air Refueling. This approach involves analyzing drogue motion to create a synthetic, deterministic target forcing function, based on the summation of several sine waves. Resulting laws of motion are applied to a target tracking task replicating a drogue chasing scenario by projecting all required references into the pilots' field of view. Piloted simulator studies conducted at the Air Vehicle Simulator (AVES) of the German Aerospace Center (DLR) demonstrate a high degree of similarity in pilot control behavior between the proposed Flight Test Maneuver and actual simulated Helicopter Air-to-Air Refueling.
To address the need for an objective assessment and comparison of pilot performance, a structured evaluation method is developed and applied specifically to Vortex Ring State (VRS) recovery techniques in flight simulators. This method assesses three key aspects of recovery performance: correct application, effectiveness, and consistency across recovery techniques. Correct application is defined using simple threshold-based criteria for each control input, providing pilots with clear, actionable feedback. Recovery effectiveness is normalized across varying initial conditions using a predictive model of minimum achievable altitude loss. Consistency is measured through the variation of performance across repeated attempts. Results are communicated at three levels of observation: individual, comparative, and aggregated. In terms of experimentation, a group of pilots, including Captain Claude Vuichard, flew all three recovery techniques in an H125 flight simulator to support the development of the evaluation method. Then, a single pilot flew the same techniques in a Robinson R66 helicopter and an R22 simulator, enabling both testing of the method and a preliminary comparison between helicopter and simulator performance.
Blade–wake interaction (BWI) is a significant source of broadband noise and is often dominant in rotors with high blade counts. Accurately capturing the resulting unsteady blade loading is computationally expensive and, therefore, drives the cost of BWI noise calculation. To address this challenge, a low-fidelity BWI noise prediction tool was developed using aerodynamic data from the blade element momentum theory (BEMT) and the lattice Boltzmann method (LBM) for a series of rotor configurations with medium to high solidity. Starting from a six-bladed baseline rotor, 13 additional configurations were generated by varying blade twist, taper, root collective, solidity, and blade count. The relationship between vortex miss distance and blade loading unsteadiness was quantified to construct a semi-empirical BWI noise model. The model predicted BWI noise with a root mean square error of 3.9 dBA and a mean absolute percentage error of 1%. It was subsequently integrated into a BEMT framework to produce aerodynamic and acoustic data for training a tandem neural network (TNN) that was employed to optimize two rotor geometries. The optimized designs achieved up to a 7% reduction in BWI noise and a 7% improvement in performance. Additional geometric modifications—including blade tip anhedral, forward sweep, and a mixed configuration—were also assessed using LBM, each demonstrating notable noise reduction.
Helicopter pilots are exposed to a wide range of vibration frequencies, primarily generated by engine and rotor dynamics. These vibrations, particularly within the 0.5–80 Hz range, pose significant risks to pilot health, including musculoskeletal injuries and fatigue. To mitigate these effects, vibration isolators are employed, with passive and active isolation systems offering different advantages. This study investigates the initial design and performance of a novel metal additive manufactured vibration isolator, optimized for placement under the pilot's seat in a rotorcraft simulator. The isolator was designed with key structural parameters including stiffness, coil dimensions, and material properties while maintaining a lightweight and durable form, with a primary goal of validating the additive manufacturing of a metallic isolator. Experimental corroboration was conducted by incorporating modifications to the Gannon Biomechanics Flight Simulator test stand (GBFS), comparing the novel isolator to an elastomeric isolator. Results demonstrate the successful fabrication of the initial additive isolator design. The additive isolator displayed a similar performance to the rubber isolator after being installed in the GBFS, though limitations on the current test rig and sensing configuration did not allow accurate characterization of the transmissibility. This research sets the groundwork for further development of a novel additive isolator and test facility.
Huma, a reconfigurable lift compounded single main rotor (SMR) helicopter, developed by the UMD Graduate Design Team, is capable of exceptional flight time, able to loiter 185-km away from its takeoff point for over 13 hours before needing to return.
Unmanned Aerial Systems (UAS) are essential in disaster relief. VTOL UAS can take off and land in confined areas without infrastructure, efficiently accessing disaster zones for life-saving missions. The AeroLay, designed for disaster relief, delivers up to 54 kg and can loiter for 17.2 hours to relay cell signals. It features quick battery swaps and an accessible fuel tank for rapid redeployment.
This paper presents insights into a comparative approach to down-select on the most suitable pilot control schemes for eVTOL and powered-lift aircraft. The investigation examines three main areas: (1) experimental flight test performance, (2) flight control analysis, and (3) Human-Machine Interface (HMI) factors. Experiments were conducted to evaluate how various inceptor control schemes were perceived by people of various experience levels, ranging from manned aviation pilots with experience in flying F-16 jets, AH-64D helicopters and high-performance turboprop trainers, to unmanned aviation pilots of various backgrounds, such as with remote control (RC) rotorcraft and RC fixed-wing aircraft, and finally to participants with zero experience with either of these. In this experimental surveying study, all participants were briefed on a standardized mission profile and tasked to fly a VTOL drone and a computer based flight simulator using various flight control schemes. Videos were recorded for each test and reviewed for in-depth flight performance and controls scoring and analysis. At the end, feedback on key Human Machine Interface (HMI) factors for each flight control method is obtained. These results in totality provided insights, strengths and weaknesses for each flight control scheme. Upon identification of the most optimal control methodology, a novel energy-based control method to unify both multirotor drone and fixed wing aircraft control logics was developed, future testing will involve incorporating the 3+1 control inceptor scheme with the energy-based control method for further testing and optimization in a simulation environment. The goal of this study is providing a design framework to help eVTOL and powered-lift aircraft designers optimize their pilot control methodology; to become more instinctive, easier to operate, safer and more cost-effective to train new eVTOL and powered-lift pilots and operators.
This paper presents handling qualities (HQs) research findings for electrical Vertical Take-off and Landing vehicles. Testing in the Vertical Motion Simulator (VMS) investigated handling qualities of vehicle configurations having a degraded powertrain. Powertrain components, including batteries and electric motors, can degrade as the vehicle is flown. This paper investigates the impact of low battery charge and high motor temperature degradations on the pilot's ability to execute precise maneuvers. Pilot comments and ratings that were collected from four rotorcraft test pilots in VMS testing are used to quantify the effects that powertrain degradations had on the HQs of the vehicle.
Electric Vertical Takeoff and Landing (eVTOL) aircraft present a series of challenges to traditional aviation infrastructure that was designed for conventional rotorcraft. Questions have arisen within the vertical flight community as to the validity and applicability of applying current heliport markings and symbology to vertiports. Several of these questions were addressed in a previous paper from VFS Forum 80: "A Comparison of Proposed Concepts for Vertiport Markings and Symbology" (Ref. 6). In contrast, this paper extends that work and presents the results of additional research to enhance the visibility of the Federal Aviation Administration’s (FAA) “Broken Wheel” symbology. These notional enhancements to the "Broken Wheel" symbology were evaluated over the course of an experimental study using helicopter-rated pilots in the FAA William J. Hughes Technical Center’s S76-D and Loft Dynamics H125 and R22 rotorcraft flight simulators.
This study investigates the evolution of axial and radial velocities in the downwash-outwash region of a counter-rotating coaxial rotor hovering in-ground effect (IGE). The presence of the ground deflects the axial flow of the rotor wake radially outward, with mean radial velocities reaching approximately 2Vh along the ground. Based on the observed velocity profiles, the wake was classified into three distinct regions: the downwash region characterized by maximum wake contraction, the transition region where flow turns from axial to radial, and the outwash region exhibiting wall jet behavior. Results show that increasing inter-rotor spacing d/R and rotor height above ground (z/R)l extends the downwash and transition regions, delaying the onset of radial outwash. Aerodynamic loads on personnel were estimated, showing maximum mean forces and moments of 120N and 120Nm, remaining within safety thresholds for untrained personnel. However, the loads exceeded these limits for heavy-category helicopters with higher disk loading. Instantaneous velocities revealed unsteady behavior driven by tip vortex convection, with peak velocities reaching 2.8Vh and peak loads approximately 50% higher than mean values, as identified using the 98th percentile approach. Frequency analysis confirmed that fluctuations at the rotor frequency dominated the unsteadiness in the rotor wake. These findings provide critical insights for safe rotorcraft operation near ground surfaces and contribute to informed vertiport design and personnel safety guidelines.
In this work, a vision-based solution is developed to address the challenge of landing on a ship deck with precision and accuracy. For an autonomous landing, it is important to have a fast and accurate pose estimation system along with a reliable control strategy. This research uses fractal ArUCo markers instead of multiple separate markers to allow smooth pose estimation at different heights. Pose estimates are further improved using an Extended Kalman Filter, and a tracking algorithm then uses these estimates to guide the landing. A four degree-of-freedom (roll, pitch, heave and sway) simulator platform was built and used to validate the algorithm. The accuracy of the vision system is compared against that of a motion capture system. Real-world experiments were performed on different quadrotors to demonstrate tracking and landing on the platform with sway, roll, and pitch motions. The results show that the system is efficient and reliable in achieving safe and successful landings. The proposed landing system is concluded to be applicable for landings on the deck of the ship under sea-state 4.
Low-level flight, defined by high-speed operations near terrain, represents a significant challenge in military rotorcraft missions while providing strategic advantages, such as radar evasion and heightened surprise. Recent conflicts highlight the urgent need for advanced low-level flight capabilities in the design of new rotorcraft. The close proximity to ground obstacles, combined with the complexities of piloting, necessitates precise control and robust handling qualities to prevent accidents. However, existing handling quality standards, such as MIL-DTL-32742, reveal limitations in assessing low-level maneuvers. Given the diverse array of new rotorcraft designs, driven by initiatives like the U.S. Army's Future Vertical Lift and NATO's Next Generation Rotorcraft Capabilities, a customized handling qualities evaluation for each design is impractical. In response, a performance-driven strategy has been implemented, scaling Mission Task Elements to align with aircraft performance capabilities. This approach identifies handling quality gaps across the Operational Flight Envelope, concentrating on the aircraft’s effectiveness in achieving task success under varied conditions. Prior simulator studies validate the effectiveness of this method for assessing different configurations. This paper presents flight test results using DLR's ACT/FHS research helicopter, confirming a set of scalable Mission Task Elements developed at DLR's AVES and NASA's VMS simulators. Pilots utilized a Head-Mounted Display for task cueing, eliminating the need for physical infrastructure. The Mission Task Elements proved suitable for evaluating the low-level handling qualities of the ACT/FHS. Although the provided Head-Mounted Display facilitated Handling Qualities evaluations, it encountered some hardware limitations. The scaling for different airspeeds met pilot expectations, and wind compensation functioned as anticipated, enhancing the independence of flight tests from environmental conditions. These findings lead to recommended updates for task descriptions and course cueing requirements, confirming desired performance tolerances.
The emergence of electric Vertical Takeoff and Landing (eVTOL) air vehicles is transforming how people and freight are moved in short distances. This transformation has a profound impact on surrounding infrastructure necessary to provide Aircraft On Ground support for eVTOLs. The hover capabilities of eVTOLs have similar operating characteristics within terminal and uncontrolled airspace. However, the need to conserve battery energy via rapid approaches and departures affects terminal airspace management. To attract eVTOL operators, existing airports, landing zones, and vertiports are modifying their infrastructure to include fixed electric charging stations, additional taxiways, upgraded fire suppression systems, separate hangers, and capable MRO facilities. Augusta Regional Airport (KAGS) is the base airport for the annual Masters Golf Tournament which experiences five times the normal airport traffic and some 40,000 commuting patrons. eVTOLs can offset land traffic issues associated with commuters and supplies. Since KAGS is centroid to 32,000 square miles of territory void of major highways, basing eVTOLs can offer expedited transit services for people and goods which will have a profound impact on the economic viability and quality of life in the area.
Abstract This paper presents a software framework developed for the simulation of vehicle-level control systems for modern (existing or conceptual) ground vehicles, targeted for high-performance platforms (Linux clusters). The framework augmented existing ground vehicle simulation environments (such as CREATE-GV MERCURY or other object-oriented software packages) making it possible to perform a comprehensive evaluation of a ground vehicle’s performance when equipped with vehicle level controllers to determine the effectiveness of the control systems on the vehicle. The framework, implemented as part of the PACE (Powertrain Analysis Computational Environment), was comprised of software components (a C++ objects library) simulating various vehicle-level controllers, an Application Programming Interface for the development of new components to be used within the framework, and C++ code for integrating these components into simulations of control systems within a ground vehicle simulation environment.
Prior to 1950, use of the helicopter for evacuation was extremely limited, as military top brass often considered it a worthless contraption; thus, rescue was uncertain at best for downed pilots and wounded soldiers stranded behind enemy lines. However, this all changed in Korea, where twelve U.S. Army helicopters from three detachments, working in tandem with seven, newly created Mobile Army Surgical Hospital (MASH) units, would fundamentally change the Army's medical-evacuation doctrine forever. Using several models of the Bell H-13, the Hiller H-23, and the Sikorsky H-5 and H-19, this small band of courageous pilots pushed themselves and their aircraft to their limits, transporting 21,212 critically wounded soldiers for life-saving surgery to various MASH units, cutting the fatality rate from World War II in half. Adopting the 3rd Air Rescue Squadron's motto, "That Others May Live," these pilots and their helicopters were affectionately known to the wounded as "Angels of Mercy."
Rotorcraft responses to idealized disturbances are examined to gain insights into model fidelity requirements for flight simulations of the ship-rotorcraft dynamic interface. Two disturbance fields are considered: an isolated straight vortex that represents the canonical vortex that results from the corners of flat top ships in oblique wind-over-deck conditions and a horseshoe vortex derived from a nondimensional characterization of the time-averaged flow observed aft of a simplified ship superstructure. Rotorcraft models considered include: an analytical blade element theory-based rotor model, where the disturbance velocities are integrated over the rotor, and a coupled blade element / free wake flight dynamic model of the full UH-60 aircraft, which is used to perform time-marching simulations with the disturbances modeled as a frozen field that is fixed in space and not interacting with the aircraft (one-way coupling), and as a distorting field (two-way coupling). Analytical thrust responses of four idealized rotors to the disturbance associated with the horseshoe vortex suggest the existence of a scaling relationship between nondimensional blade loading and the product of nondimensional vortex width and strength. Time-averaged rotor thrust responses to the disturbance induced by the isolated straight vortex indicate significant distortion of the rotor wake and disturbance field at low forward speeds, with the frozen field assumption indicating greater disk tilt responses. Modeling the horseshoe vortex disturbance as a frozen field generates a greater rotor response than in the distorting case. Inclusion of full aircraft dynamics attenuates rotor responses to the disturbances when compared to isolated rotor responses.
ABSTRACT Updates to the military rotorcraft handling qualities specification are currently being considered that address the high-speed flight regime envisioned for the Future Vertical Lift platform of the US Army. A team that features industry and academia have developed and evaluated a set of Mission Task Elements (MTEs) that have been defined to address VTOL high-speed handling qualities. Following the mission-oriented approach upon which ADS-33E-PRF is based, the MTEs were designed to meet different levels of precision and aggressiveness. The attitude capture and hold MTEs that are the subject of this paper were defined to be precision, non-aggressive tasks that build upon fixed wing analogs. The MTE objectives, descriptions, and performance criteria were assessed and refined via several checkout piloted simulation sessions. Formal evaluations were then conducted by Army test pilots at four simulator facilities, each featuring a unique high-speed platform including a generic winged compound helicopter, two tiltrotor configurations, and a compound helicopter with coaxial rotors. To aid in the MTE evaluation process, baseline VTOL configurations were varied to achieve different handling qualities levels. Quantitative measures based on task performance and qualitative measures based on pilot ratings, comments and debrief questionnaires were used to assess MTE effectiveness. The piloted simulation results demonstrated that the attitude capture and hold MTEs provided an effective means to discern precision, non-aggressive handling qualities in high speed flight.
ABSTRACT Updates to the military rotorcraft handling qualities specification are currently being considered that address the high-speed flight regime envisioned for the Future Vertical Lift (FVL) platform of the US Army. The US Army's National Rotorcraft Technology Center (NRTC) project "Rotorcraft Handling Qualities Requirements for Future Configurations and Missions" is a U.S. Government and Industry co-funded three year research project. A Sikorsky-led project team that features industry and academia have developed and evaluated a set of Mission Task Elements (MTEs) that are defined to address rotorcraft high-speed handling qualities. Following the mission-oriented approach upon which ADS-33E-PRF is based, the MTEs were designed to meet different levels of precision and aggressiveness. Break Turn MTE was defined for non precision, aggressive applications in order to provide a suitable coverage of aggressive air combat maneuvers in future ADS-33. The MTE objectives, descriptions, and performance criteria were systemically developed via a series of piloted simulation sessions at each team's simulation facility. Formal evaluations were then conducted by US Army test pilots at four simulator facilities, each featuring a unique high-speed platform including an X2 Technology™ compound helicopter, two tiltrotor configurations, and a generic winged compound helicopter. To enhance the MTE evaluation process, baseline control law (CLAW) configurations were varied to achieve different handling qualities levels. Quantitative measures based on task performance and qualitative measures based on pilot ratings, comments and debrief questionnaires were used to assess MTE effectiveness. The piloted simulation results demonstrated that the Break Turn MTE provided an effective means to discern non-precision, aggressive handling qualities in high speed flight.
ABSTRACT At the end of 2014, the Group for Aeronautical Research and Technology in EURope (GARTEUR) launched an action group (named AG22) in order to address both experimentally and numerically the issue of rotor wake interacting with obstacles. Within this group, several different experiments were set up and the results were provided to all the partners in order to compare and improve their numerical methods aimed at capturing interaction effects. In the present paper, we numerically investigate the experimental database provided by Politecnico di Milano (Polimi). A low fidelity method based on free wake approach and also CFD computations with different level of modeling are compared to experimental data. It shows that free wake approach is perfectly suitable to predict interaction effects on the rotor loads as long as there is no wake re-ingestion by the rotor. In other cases, the use of CFD is mandatory. However, computational cost can greatly be reduced using some approximation (no fuselage, immersed boundary method approach for the building, wall slip boundary condition on the ground) without significant loss in the rotor loads accuracy. Moreover, such approximation still gives acceptable results with regards to the effects of the rotor wake on the building itself and across the flowfield.
ABSTRACT This paper describes the modeling and simulation developments made in support of the AVX Joint-Multi-Role (JMR) Coaxial Compound Helicopter (CCH) handling qualities evaluation. The real-time full flight simulation model for the AVX-JMR CCH was developed in FLIGHTLAB and incorporates AVX's fly-by-wire (FBW) control laws. Extensive piloted simulation tests were conducted that cover various mission task elements (MTEs), including those described in the ADS-33E-PRF (Ref. [1]). The MTE test courses were set-up with proper visual cues in accordance with ADS-33E specification. For each MTE test, the test pilots evaluated the performance with ADS-33E handling qualities ratings (HQR) for achievable levels of aggressiveness and control precision. At the same time, the piloted simulation test data were recorded for post-test analysis to demonstrate the evaluation accuracy through comparison with ADS-33E performance standards. In addition to the piloted simulator tests, quantitative analyses were also conducted to assess the AVX-JMR CCH against ADS-33E hover/low speed and forward flight requirements using the ADS-33E handling qualities analysis toolkit in FLIGHTLAB. The quantitative analyses evaluated small and moderate amplitude attitude changes and inter-axis coupling characteristics of the AVX-JMR CCH against the Level 1, 2, and 3 criteria of ADS-33E-PRF. Both the qualitative and quantitative results are presented in this paper to summarize the handling qualities evaluation of the full flight AVX-JMR CCH simulation model.
ABSTRACT Shipboard operations present a unique set of challenges to the pilot-vehicle system. This work addresses problems specific to piloted rotorcraft in the simulated shipboard environment, namely cueing and ship motion, and represents the completion of a three-year effort focused on fixed-base, pilot-in-the-loop rotorcraft flight simulations. Instructors from the United States Naval Test Pilot School, with extensive operational and test experience, participated in the study. Two cueing sets, one for the approach task and another for the hover task, were developed in order to provide intuitive guidance of cyclic and collective inputs. Data were gathered for each task with the cueing system both on and off. The evaluation criteria used to determine the usefulness of the provided cueing were based on pilot workload assessment, profile performance and inceptor activity. The approach task cueing provides the pilot with a preset approach profile defined by altitude and airspeed cueing, while the hover task cueing provides the pilot with a top-down view of helicopter position over the landing spot and a representation of the vehicle’s acceleration vector. Different control response types were assessed, as well as different ship motion intensities. Both tasks show that use of the developed cues allows pilots to achieve greater precision with less overall workload when compared to task performance without cueing available.
ABSTRACT Updates to the military rotorcraft handling qualities specification are currently being considered that address the high-speed flight regime envisioned for the Future Vertical Lift (FVL) platform of the US Army. The US Army's National Rotorcraft Technology Center (NRTC) project "Rotorcraft Handling Qualities Requirements for Future Configurations and Missions" was a U.S. Government and Industry co-funded three-year research project. A project team that features industry and academia have developed and evaluated a set of Mission Task Elements (MTEs) that are defined to address rotorcraft high-speed handling qualities. The High Speed Acceleration/Deceleration MTE was designed to provide suitable coverage in ADS-33 for handling qualities in Low/High Speed Transitional flight regimes (e.g. rotor-borne to wing-borne flight). The MTE objectives, descriptions, and performance criteria were developed via a series of piloted simulation sessions at each of the four teams' simulation facility. Formal evaluations were then conducted by US Army and contractor test pilots at the four simulator facilities, each featuring a unique high-speed platform, including two tiltrotor configurations, an X2 Technology compound helicopter, and a generic winged compound helicopter. To enhance the MTE evaluation process, baseline control law (CLAW) configurations were varied to achieve different handling qualities levels. Quantitative measures based on task performance and qualitative measures based on pilot ratings, comments and debrief questionnaires were used to assess MTE effectiveness. The piloted simulation results demonstrated that the High Speed Acceleration/ Deceleration MTE provided a suitable and effective means to evaluate Transitional handling qualities between low and high speed flight, although some refinements may still be warranted.
In this paper a full vehicle UH-60A helicopter with and without stub wings is simulated in steady autorotation using both the flight dynamics (FD) code HeliUM-A and the computational fluid dynamics/computational structural dynamics (CFD/CSD) solver CREATE-AVTM Helios. Significant effort was put into trimming the CFD/CSD simulations to an autorotative state that is representative to how the aircraft flies in practice, and the method for doing so is described. For the baseline aircraft, both FD and CFD/CSD predictions of the vehicle's autorotational descent rate were in excellent agreement with available flight test data. CFD/CSD analysis showed that the presence of the fuselage led to a significant positive pitching moment on the rotor as well as a sudden loss of loading as the rotor blades pass through the fuselage wake. When External Stores Support System (ESSS) stub wings were added to the model, both solvers show both quantitative and qualitative agreement in their predictions of the increase in autorotational descent rate due to the additional ESSS drag. CFD/CSD analysis showed that the stub wings had minimal effect on the interactional aerodynamics between the airframe and rotor.
Some infants are born prematurely or with medical conditions that require them to stay in neonatal intensive care units (NICUs). Typically, these infants spend most of their time in an incubator as it provides a safe and controlled environment. At times, these infants will need to be transported via helicopter from one hospital to another, which exposes their already fragile bodies to higher levels of vibration. Helicopters, while advantageous for medical transport, generate substantial vibration due to rotor dynamics. Current models of incubators lack specific design for reducing vibrations. This project proposes a functional vibration damper that can be integrated into existing neonatal incubators, aiming to enhance infant safety during air transport. ANSYS modeling identified low-density polyethylene foam as an effective material for vibration reduction. Flight simulation tests demonstrated the 2" polyethylene mattress reduced vibrations at low amplitudes and frequencies, but challenges arose at higher values. The prototype addresses the critical need for reducing vibrations in neonatal incubators during air transport. While successful in initial tests, further extensive testing is required for potential implementation in the medical industry.
A high-fidelity flight simulator is used to effectively train and evaluate pilots. The simulator must, however, be previously qualified by authorities by comparing the responses of the simulator to those of flight tests for several maneuvers. The use of a controller is permitted to make corrections to the simulator input signals. The simulator inputs and outputs must, however, be within tolerance bands defined by the authorities, compared to flight test data. This article presents a model predictive controller (MPC) and its evaluation on a takeoff and landing case. The method is already promising because these results were obtained after very few tuning iterations, which could result in significant time and cost savings. This is made possible by the clear meaning of the impact of the MPC tuning parameters on the simulator inputs and outputs and also by the ability to intrinsically consider the interactions and constraints of the multivariable system.
The unique designs and capabilities of electric Vertical Takeoff and Landing (eVTOL) aircraft present a series of challenges to traditional infrastructure that was designed for conventional rotorcraft. Currently, several civil aviation authorities have released interim, preliminary guidance on aspects of vertical flight infrastructure. This paper presents a comparison of two of the proposed concepts for vertiport markings and symbology, the Federal Aviation Administration (FAA) "Broken Wheel" and the European Union Aviation Safety Association (EASA) "V". These concepts were evaluated over the course of two experimental studies using helicopter-rated pilots in the FAA William J. Hughes Technical Center's S76-D and Loft Dynamics H125 & R22 rotorcraft flight simulators.
NASA's 4th New Frontiers Mission is the Titan Dragonfly relocatable lander. This coaxial quadrotor vehicle will be launched on a rocket to Titan in 2028. Following a gravity assisted Earth flyby and an approximate 6-year transit, Dragonfly will enter the Titan atmosphere around 2034 with the goal of exploring Titan's pre-biotic chemistry and habitability. The multirotor design for this unique application has continually evolved since 2016 with constraints such as Titan's cryogenic atmosphere at 95 Kelvin (-288 F), gravity 14% that of Earth's, atmospheric density 440% of standard sea-level air, and the inability to test the entire system together under all these conditions until the first flight on Titan. This paper focuses on rotor design aspects of the Dragonfly lander and introduces a novel framework for multirotor design optimization considering multiple flight conditions. The methodology leverages machine learning methods and is demonstrated in the context of Dragonfly. A new OVERFLOW Machine Learning Airfoil Performance (PALMO) database is first presented. PALMO is then wrapped inside a Bayesian optimization framework and applied to a 4-rotor system (one side of the Dragonfly lander). Training data is generated on each iteration of the optimization using the CAMRAD-II comprehensive analysis software to evaluate successive rotor designs in multiple relevant flight conditions. An optimal design for the 4-rotor system was found with approximately 900 rotor designs analyzed in CAMRAD-II, which required 9 million queries of the PALMO surrogate models. This demonstration case evaluated 10,000,000 potential candidate rotor designs in 5.5 hours on 114 CPU cores using uniform inflow, and in 27.8 hours using the prescribed wake model. This work thus enables mid-fidelity rotor design optimization without requiring access to high-performance computing.
ABSTRACT A flight simulation model for the UH-60 Black Hawk based on Sikorsky's GenHel model is modified to simulate a locked failure of a main rotor swashplate servo actuator and is compensated by using the stabilator as a redundant control effector. Steady state trim analysis is performed to demonstrate feasibility of trimmed flight in various conditions with different locked servo actuator positions for the forward, aft, and lateral actuators. A model-following, linear dynamic inversion controller is implemented and modified to account for locked actuator position. Post-failure, the control mixing and feed-forward control coupling terms are reconfigured to partially reallocate the control authority in the longitudinal axis from the main rotor longitudinal cyclic to a symmetric deflection of the stabilator. This is done by manipulation of only the control allocation relating pilot stick inputs to servo actuator positions, the feedback control gains and mechanical rigging between servo actuators and rotor pitch controls remain identical to the baseline controller. Flight simulation results demonstrate the ability of this reconfiguration to compensate for locked failure of the forward main rotor swashplate servo actuator, as well as the ability of the aircraft to decelerate from cruise at 120 knots to 50 knots which is less than the published safe rolling landing speed of 60 knots. A similar range of locked positions of the forward and aft actuators is demonstrated to be feasible for aircraft recovery using control of the stabilator. Feasibility of aircraft recovery for locked positions of the lateral servo actuator is also considered.
Many traditional ship-rotorcraft interactional simulation approaches, including those used for pilot training, use a one-way coupling between aerodynamics and flight dynamics. In a one-way coupled method, the standalone ship airwake is superimposed on the rotor, modifying its inflow. However, because the rotor wake does not alter the ship airwake in such a simulation, one-way coupling may not capture all relevant phenomena, such as dynamic ground and wall effects; two-way fully-coupled simulations may be needed. In this study, one- and two-way coupled realtime and near-real-time simulation models of the ship-rotorcraft problem were developed using a GPU-accelerated Lattice-Boltzmann Method (LBM) flow field solver. Comparing flow fields and rotor hub loads, the two-way coupled simulations showed good agreement with new ship-rotor experimental data from Georgia Tech. Real-time full-scale rotorcraft ship approach maneuvers of a notional UH-60A landing on the NATO Generic Destroyer were conducted using a flight controller, and the results showed significant differences in flight control inputs between one- and two-way coupling methods. On the other hand, the presence of ship motion was found to have little effect on the control inputs. The study proved the feasibility of real-time fully-coupled ship-rotorcraft flow field simulations, achieving real-time performance on a single GPU node, and it paves the way for fully-coupled LBM pilot-in-the-loop flight simulation trials.
This paper reports on the initial implementation of Machine Learning (ML) for predicting the workload experienced by a pilot when performing a recovery to a naval ship. Pilots classify their workload for each landing by providing a subjective rating, which is used to determine the ship-helicopter operating limit (SHOL). Different workload metrics have been trialled to bridge the gap between pilot subjective ratings and objective flight data. With hundreds of different helicopter, ship and airwake parameters available to examine, ML provides an approach to understanding the complex interactions between these variables. This paper looks at the initial results obtained by applying ML techniques to train a classification algorithm with pilot control input data. Preliminary results showed 77.14% accuracy when training a Linear Discriminant algorithm to predict pilot workload from cyclic, collective, and pedal input data.
As military organizations internationally assess life extension and replacement actions for current legacy helicopter fleets and next generation rotorcraft are under development, novel rotor system technologies are required to fulfill challenging low-speed and high-speed flight envelopes and mission requirements. Proposed by the Department of National Defense (DND) and in collaboration with the National Research Council of Canada (NRC), a TTCP AER CP13A.1 Collaborative Project (CP) has been initiated supporting multi-nation development of numerical methods for optimizing and designing next generation main rotor blades. Four NRC laboratories collaborated to assemble a data set comprising design, performance, aerodynamics, structures, dynamics, and flight sciences elements. Acquired through research and testing, this information provides reference, technical, and engineering knowledge to support aero-structural model definition, model output validation, and the numerical optimization process development.
This paper describes development and testing of a low-cost device mounted on in the pilot seat of a rotorcraft simulator with the aim of improving the perceived realism of the flight. The device acting vertically from the bottom of the seat is used to communicate changes of acceleration in the vertical direction corresponding to heave movement of the simulated aircraft. A bespoke flight simulator system was developed, featuring modular design and virtual reality (VR) visualisation to enable comparative testing with a full motion system. Objective analyses have shown similarities between the two motion cueing configurations when contrasted with only using visual cues.
Refueling mid air is considered as important force multiplier for e.g. conducting search and rescue operations. Due to close proximity to the tanker, the refueling hose and drogue as well as the receiver can be strongly affected by the tanker's wake. Thus, the refueling drogue extended from the tanker by a hose is often oscillating from turbulence. Contact with the tanker has to be established by positioning the receiver's refueling probe within the tanker's drogue. During qualification training pilots are instructed to not focus on the drogue, due to its oscillations. This is done since chasing the drogue often leads to over-controlling and therefore mostly to a failed contact attempt. The presented research aims for improving today's Helicopter Air-to-Air Refueling (HAAR) as well as related training efficiency by a gain of understanding in this phenomenon. Therefore, the HAAR real-time simulation scenario at German Aerospace Center's (DLR) Air Vehicle Simulator (AVES) was extended with a multi body hose and a probe/drogue contact model to enable realistic contact initiation. During a piloted campaign, a total of six pilots with different levels of HAAR experience conducted the maneuver. This paper presents an analysis of obtained eye tracking data with regards to gaze entropy, total fixation duration on defined areas of interest and corresponding time history of control inputs. Potential links between gaze entropy and perceived workload that might be observed in the data are also discussed. Results show that the metrics can highlight differences in successful and unsuccessful attempts for contact of HAAR experienced and inexperienced pilots.
The complex vertical takeoff and landing configurations currently under development necessitate flight control system design that enables substantial reductions of pilot workload through Simplified Vehicle Operations. This paper shows optimization and simulation of such a flight control system architecture for a subscale vectored thrust aircraft configuration. A full-envelope Trajectory Control System for longitudinal dynamics was coupled with explicit model-following inner-loop controllers, and a scheduled control allocation logic. Control system parameters were determined using a genetic algorithm optimization scheme subject to dynamic stability, robustness, and control responsiveness constraints. Flight simulation results for a series of representative maneuvers including departure and arrival transitions and forward flight maneuvers are presented to demonstrate the effectiveness of the proposed flight control system architecture.
Safety professionals receive data from internal and external sources, then manually determine whether the issue constitutes a safety hazard. Many reports are received, and each report is reviewed, then investigated further, using a tedious, labor intensive, and possibly error prone process. In the course of reaching a decision, human bias is inevitable - any two humans could reach different conclusions, and the same individual human could draw different conclusions on different days. As technology has advanced, numerous approaches have been pursued, attempting to reduce human bias and improve both efficiency and effectiveness of the process. In recent years, moderate success was achieved, which provided accuracy rates near 85% but continued refinement did not achieve acceptable results. In early 2023, the challenge was given to a new team, and within a few months, state-of-the-art Artificial Intelligence/Machine Learning data analytics techniques were utilized to aid in safety data analysis efforts, which resulted in high accuracy and efficiency, with reduced human bias.
The National Research Council of Canada (NRC) has recently developed an Integrated Reality In-flight Simulator (IRIS) that allows helicopter pilots to fly the NRC's Bell 412 Advanced Systems Research Aircraft (ASRA) while wearing a commercial off-the-shelf (COTS) virtual reality headset. IRIS is the first airborne simulator of its kind that combines COTS virtual reality and Fly-By-Wire (FBW) synthetic turbulence for helicopter operations. Simulations are not exact replications of actual environments; therefore, a methodology of comparing pilot workload with respect to an analysis of the differences between the simulated and actual environments is required. During a recent flight trial, NRC validated the effectiveness of IRIS to replicate a pilot's workload during ship landing tasks using these workload scales. During the analysis, NRC took initial steps in developing methodologies to examine environmental characteristics and then correlate them to an associated pilot workload. The work also included the initial development of methodologies to analyze pilot workload and alternative prediction methods that better map subjective or quantitative pilot workload data to DIPES.
A piloted simulation experiment was conducted in the NASA Ames Vertical Motion Simulator to investigate the effects of bandwidth, phase delay, attitude quickness, and maximum achievable rate on yaw-axis handling qualities in hover and forward flight. Two different aircraft were tested, representative of advanced scout-class rotorcraft. Five target acquisition and tracking Mission Task Elements were used in the study. Two of the tasks were modified versions of tasks used to determine the ADS-33E target acquisition and tracking yaw attitude quickness boundaries. Two of the tasks were modified versions of attitude capture and hold and sum-of-sines tracking previously used to evaluate pitch and roll axis handling qualities. The final task was a forward flight target acquisition task developed for this study based on a ground attack or strafing maneuver. Eight Army pilots participated in the study and evaluated 60 yaw-axis configurations. The results of the study suggest that the current yaw-axis hover/low-speed and forward flight bandwidth and hover/low-speed attitude quickness requirements for target acquisition and tracking are too low. Updated boundaries for these requirements are recommended.
The integration of automation and autonomy into modern aircraft has significant potential to simplify many piloting tasks. On the other hand, poor integration of automation and autonomy systems with the human crew has sometimes led to unintended consequences. With the goal of improving human-machine integration in piloting tasks, Bell Textron has conducted several autonomy demonstrations in both the simulator and aircraft. The team assessed automated terminal operations, enhanced station keeping, and maneuver tactile limit cueing in a flight simulator. Additionally, the V-280 technology demonstrator conducted autonomous flight profiles to explore these systems in an airborne environment. To mature autonomy systems for integration on future platforms, a Bell 429 was converted into the Aircraft Laboratory for Future Autonomy, completing its first flight last year with fly-by-wire controls at the evaluation pilot station. The influence of Bell autonomy demonstrations on the evolution of Optimally Crewed Vehicles is presented. These efforts have evolved the concept of a digital co-pilot capable of assisting the human crew when called upon, while also acting to enhance aircraft safety through warnings and automated control input, when appropriate.
Full vehicle CREATE-AV™ Helios model has been developed for SB>1 Defiant®, a Joint-Multi-Role Technology Demonstrator (JMRTD) designed by the Sikorsky-Boeing team utilizing compound design with coaxial rotor and propulsor. The full vehicle model includes coupling with RCAS for elastic blade deformation as well as full vehicle trim in steady level flight condition. The purpose of current study is to assess performance prediction capability of the developed Helios modeling approach for such a complex non-traditional design by correlating with flight test data. To minimize uncertainty in flight test data reduction, correlations were made with the data that were directly measured or requiring minimal derivation. The Helios model showed generally very good correlation in power, component forces, rotor and propulsor efficiencies for wide range of flight test conditions. The model also showed very good correlation in performance sensitivity to trim state and rotor RPM, which demonstrates the modeling approach can be used to find optimal flight trim condition. Significance of geometric details and its aerodynamic interference such as shaft modeling has been demonstrated. Impact of measurement uncertainty to data correlation was also demonstrated.
This study investigates the use of machine learning (ML) models to estimate the gross weight (GW), the longitudinal position of the center of gravity (CGx), and 1/rev cyclic flapping angles (Δ1c and Δ1s) of a compound helicopter with three redundant controls - main rotor RPM, collective propeller thrust, and stabilator angle. Neural Network (NN), Gaussian Process for Regression (GPR), and Support Vector Machine (SVM) algorithms are employed to develop estimation models using supervised training. The airspeed, redundant controls, main rotor controls, aircraft attitudes, and main rotor torque are selected as input variables (predictors) to the models due to their accessibility through the aircraft Health and Usage Monitoring System (HUMS). The dataset is split into low-speed and high-speed regimes to compare the prediction accuracy and training cost of separate regime models against a combined full-regime model. Separate airspeed regime GPR models showed superior performance in GW estimation, with higher accuracy and cost-effectiveness compared to a single full-regime model. For CG estimation, GPR again outperformed NN and SVM, although the maximum outlier errors increase significantly if a 95% confidence interval is considered. Finally, for 1/rev cyclic flapping angle predictions, SVM estimations, though not superior to GPR or NN, were acceptable and had a significantly lower computational cost. The study also examined the importance of predictors, highlighting that, on average, certain predictors like rotor RPM and rotor torque are less influential, but their removal degraded performance and had no cost benefit.
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