Browse Topic: Tools and equipment
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.
Urban Air Mobility (UAM) concepts require multidisciplinary analyses across multiple modes of operation and often involve discrete architectural differences such as propulsion type, rotor configuration, and mission context. Existing optimization and workflow frameworks support continuous design variables but provide limited mechanisms for handling discrete variants, multi-modal vehicle definitions, and vehicle management for UAM vehicles. This paper presents uam4x, an open-source Python framework that addresses these challenges through a structured problem definition representation, a plugin-based execution engine, integrated version control, and a function-based branching script mechanism for constructing analysis scenarios. The framework provides integration of existing tools including Open Vehicle Sketch Pad (OpenVSP), NASA Design and Analysis of Rotorcraft (NDARC), M4 Structures Studio (M4SS), and Intelligent Cross Section Generator (IXGEN) through unified plugin interfaces. Parameter sweeps, nested analyses, and optimization via OpenMDAO are supported within the same architecture. This paper also presents demonstrations that were created to illustrate the various capabilities and integration efforts of the framework.
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.
This paper presents a meshless large eddy simulation approach for rotorcraft wake prediction, using a vortex particle method accelerated on GPUs. The solver couples a rotor model with a vortex particle wake model, employing the Fast Multipole Method for computational efficiency and implementing viscous diffusion through Particle Strength Exchange and Core Spreading Methods. GPU acceleration achieves speed-ups of up to 10x compared to CPU execution. The solver’s predictions are validated against experimental data, showing excellent agreement. Effects of time step size, numerical integration schemes, viscous models, and particle overlap factors on simulation accuracy and computational cost are systematically analyzed. This GPU-based vortex particle framework provides a fast, accurate, and scalable tool for rotorcraft wake simulations.
The Shake-The-Box technique was applied to experimentally quantify the time-resolved volumetric flow field around a free-flying quadcopter UAV with an overall span of about 0.5 m. State-of-the-art LED illumination and high-speed camera equipment was combined with modern Lagrangian tracer particle tracking and data assimilation techniques, facilitating a measurement volume larger than 1.5m3. The setup allowed for both hover and limited maneuvering of the quadcopter, while resolving even small details of the complex interactional aerodynamics. In hover out of ground effect, the four individual rotor wakes merged into a single jet within a few rotor radii below the rotor planes. Evaluating the mass and momentum fluxes over suitable control volumes yields accurate estimates for the quadcopter's total thrust, the asymmetric thrust distribution between front and back rotors, and the entrainment of external flow through turbulent mixing. Hover in ground effect decreases the power requirement and induces recirculating flow in the center of the four rotors. The outwash pattern is non-uniform with jets developing between the rotors and pointing in radially outward directions. Forward flight cases result in a skewed, rapidly merging wake flanked by the roll-up of two "super-vortices" similar to the wingtip vortices of fixed-wing vehicles.
ABSTRACT The impact of hover download on rotorcraft design has long been recognized, though analytical focus on the issue has been intermittent, for both technical and programmatic reasons. Advanced models employed on high performance computer systems have shown impressive ability to capture observed behavior, though physics-based tools better suited to routine early stage design analysis are highly desirable. Prior papers conducted an initial assessment the ability of several contemporary "mid-fidelity" analysis tools to compute download and rotor/airframe interaction on helicopters and compound rotorcraft in hover, with initial studies focusing on single rotor aircraft operating out of ground effect. This paper extends this work to the consideration of other rotor configurations (e.g., tiltrotor/side-by-side and coaxial cases); given the development and prospective use of multiple new vehicles featuring these design elements an assessment of this capability is judged timely. In addition, this paper will address the application of these models to the impact of ground proximity on download, an important operational consideration. The major features of airframe download and rotor performance are captured for several representative cases, and observations on differences in predicted and measured performance are discussed.
ABSTRACT Accurate prediction of aeroelastic coupling between rotor wake and structure remains a key challenge to the development of advanced rotorcraft. Limitations of existing analysis tools to predict such aeroelastic interactions, notably empennage buffeting effects, have resulted in costly late-cycle design changes in multiple rotorcraft development programs, including the UH-60A and AH-64A. Aeromechanical phenomena involving interactions of the fuselage and rotor wake are complex, interdisciplinary, and three-dimensional in nature. For this reason, full vehicle CFD/CSD coupled analysis is essential to accurately capture the mutually dependent interactions between the aerodynamic loads and the aeroelastic response associated with these phenomena. The current state-of-the-art in rotorcraft analysis involves CFD/CSD coupled analysis of aeroelastic rotors and wings, but rigid representations of the fuselage and empennage structures (Ref. 1). To address this limitation, an elastic fuselage coupling capability was developed using RCAS and FUN3D. The elastic fuselage CFD/CSD interface has been successfully tested for several demonstration cases and one validation case.
Coupling numerator models are a well-established tool for predicting the closed-loop dynamics of multiple-input multiple-output systems. They describe the input-output dynamics of the open-loop path in a partially controlled system given tight controls and thus may serve as an approximation of the actual dynamics "seen" by the single-axis controller in a controlled multiple-input multiple-output plant. Such models can therefore be employed for a decentralized initial design of multivariable controllers. This paper presents a new, unifying approach for the computation of such constrained input-output dynamics. Connections to existing methods in the literature are established and a general procedure for state-space calculations is given. The use of coupling numerator models for controller design is motivated and different decoupling structures are discussed. The controller design is illustrated using a coupled high-order helicopter model.
This paper documents the re-evaluation and updates to the previous Partial Regime Recognition Spectrum effort for the MH-47G using Structural Usage Monitoring System (SUMS). Further validation of the SUMS algorithm allowed for additions to the spectrum. These additions include more refined categorization of turn and partial power descent regimes based on angle of bank and descent rates, respectively; high load prorates for turns, partial power descents, level flight, and climbs based on the Cruise Guide Indicator; exceedances of maximum density altitude; and use of occurrences for Landing and Run-On Landing regimes. Additional years of flight data from 2013 to 2019 were included in this effort. The updated usage spectrum for the Army MH-47G aircraft has been delivered to the OEM (Original Equipment Manufacturer). The OEM calculated new fatigue lives and updated the "Fatigue Substantiation Report", which will soon be fielded.
ABSTRACT
High-fidelity CFD simulations of hovering flights of the multi-rotor Volocopter 2X (VC2X) aircraft with three different heights above the ground and an out of ground reference case are presented. The tool chain applied consists of the CFD solver FLOWer, which is loosely coupled to the flight mechanic tool VFAST. For all simulations an adequate representation of the flight mechanics is of crucial importance since the high number of trim degrees of freedom of the VC2X has a significant influence on the flight physics. A short introduction and validation of VFAST is carried out, which shows that VFAST already provides valuable stand-alone results for the considered flight envelope. The in ground and out of ground CFD simulations showed a highly complex flow field for the VC2X. With increasing ground proximity the number of vortex structures induced by the ground increases and the rotor wake is characterized by strong fluctuations. Basic rotorcraft in ground effect phenomena, like a high-pressure area below the rotor plane and aircraft power reduction are observed for low flight heights. The decreased power requirement is mainly traced back to a decrease of the airframe download. The system figure of merit for all three in ground cases merely changes.
Advanced CFD tools are nowadays used routinely for analysis and design of rotorcraft. Computations for flows around rotors in trim are also common place and slowly the research community is shifting towards simulations of rotorcraft during maneuvering flight. One of the impediments of this effort is the lack of detailed data for validation, evaluation and thorough assessment of CFD methods when it comes to rotors with time-varying inputs. This paper presents a first effort to validate CFD tools for step-inputs in rotor control angles and presents both novel simulations, and un-published experimental data. The results show that there is always a lag involved between the wake and loads response and the operation of low-thrust rotors with dynamic wakes and collective input is a challenging task for modern CFD. The results used in this work originate from a study carried out at the Nanjing University of Aeronautics and Astronautics in China and represent a unique set of great value to the research community. The agreement with simulation results further contributes to the value of the test data.
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