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ABSTRACT Over time, the National Institute of Standards and Technology (NIST) has refined the 4Dimension / Real-time Control System (4D/RCS) architecture for use in Unmanned Ground Vehicles (UGVs). This architecture, when applied to a fully autonomous vehicle designed for missions in urban environments, can greatly assist in the process of saving time and lives by creating a more intelligent vehicle that acts in a safer and more efficient manner. Southwest Research Institute (SwRI®) has undertaken the Southwest Safe Transport Initiative (SSTI) aimed at investigating the development and commercialization of vehicle autonomy as well as vehicle-based telemetry systems to improve active safety systems and autonomy. This paper will discuss the implementation of the 4D/RCS architecture to the SSTI autonomous vehicle, a 2006 Ford Explorer.
This procedure describes a method of measuring the resistance to wet color transfer of materials such as textiles, leather, and composites.
GV WIP Test Scope
This SAE Information Report contains definitions for hydrogen fuel cell powered vehicle terminology. It is intended that this document be a resource for those writing other hydrogen fuel cell vehicle documents, specifically, Standards or Recommended Practices.
This SAE Information Report contains definitions for hydrogen fuel cell powered vehicle terminology. It is intended that this document be a resource for those writing other hydrogen fuel cell vehicle documents, specifically, Standards or Recommended Practices.
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This SAE Standard specifies terminology for agricultural equipment designed primarily for use in agricultural operations fo rthe production of food and fiber.
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SCOPE IS UNAVAILABLE.
This digital standard is a requirements extract of AS13100A Quality Management System Requirements for Aero Engine Design and Production Organizations. This file contains a general requirements extraction as well as files that are optimized for use with Doors Classic, Siemens Polarian, and PTC.
SCOPE IS UNAVAILABLE.1
This document specifies performance and quality requirements for the qualification and manufacture of 24 degree cone fittings to ensure reliable performance in aircraft hydraulic systems.This document specifies baseline criteria for the design and manufacture of system fittings that are qualification tested on engines.This document covers fittings of temperature types and pressure classes specified in MA2001.
This standard provides background information and a hydrogen fuel quality standard for commercial proton exchange membrane (PEM) fuel cell vehicles. This report also provides background information on how this standard was developed by the Hydrogen Quality Task Force (HQTF) of the Interface Working Group (IWG) of the SAE Fuel Cell Standards Committee.
This SAE Information Report contains definitions for hydrogen fuel cell powered vehicle terminology. It is intended that this document be a resource for those writing other hydrogen fuel cell vehicle documents, specifically, Standards or Recommended Practices.
Drain and Fill plugs used on engines, transmissions, transfer cases and front and rear drive axles for class 5 – 8 vehicles.
This specification covers a corrosion and heat-resistant steel in the form of welding wire.
This organizational process survey provides insight into the technical aspects of approved airworthy aircraft modifications applied in government organization vertical lift flight test. The publication reviews processes applied by the National Research Council of Canada's Flight Research Laboratory (NRC-FRL) and its Airworthiness Control System to enable research flight testing. Dominated by the need for integrating experimental payloads, the NRC-FRL embeds a Design and Fabrication Service organization for modification of internal and external client projects and flight test aircraft. In context of experimental flight testing, this work reviews technical information on process, facilities, and methodology for airworthy integration of flight test payloads. Information is used to synthesize recommendations in experimental vertical lift flight testing that satisfy both formal (regulated compliance) and informal (compliance intent) airworthiness requirements.
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.
Deep Reinforcement Learning (DRL) for quadrotor flight control typically relies on Domain Randomization (DR) for sim-to-real transfer, resulting in overly conservative policies that struggle with dynamic disturbances. To overcome this, we propose a novel adaptive control architecture that actively perceives and reacts to instantaneous perturbations. First, we train an optimal outer-loop policy, then replace its reliance on ground-truth disturbance data with a Residual Dynamics Predictor (RDP). The RDP estimates the external forces and moments acting on the aircraft in flight online using only the history of states and control actions. For seamless hardware transfer, we introduce a data-efficient linear calibration bridge and an online thrust correction mechanism that align the simulated latent space with reality using mere seconds of flight data. Real-world validations on a Crazyflie micro-quadrotor demonstrate that our adaptive controller significantly outperforms baselines
This paper introduces an eigenvalue-based whirl flutter prediction method accounting for aerodynamic interactions between a wing and propeller. The linearized unsteady vortex lattice method was utilized to model fixed-wing aerodynamics while the linearized viscous vortex particle method was utilized to model rotary-wing aerodynamics. The complete aerodynamics model was then coupled with computational structural models to demonstrate the capabilities of the model to predict whirl flutter using an eigenvalue-based method. Two computational structural models were used: the first being an analytical propeller model affixed to a rigid wing via root springs and dampers, and the second being the University of Michigan's Nonlinear Aeroelastic Simulation Toolbox. These models demonstrate the capabilities of the linearized aerodynamics model in predicting instability with structural models of different fidelities, both considering and not considering aerodynamic interactions. The linearized
This paper investigates the impact of aerodynamic interactions on the whirl flutter boundary of wing-twin-propeller configurations. A coupled wing-pylon-propeller model is developed in the Rotorcraft Comprehensive Analysis System (RCAS), where the wing is modeled using uniform inflow and the propeller wake is modeled using the viscous vortex particle method (VVPM). The study examines the effects of spanwise propeller placement and rotation direction by first analyzing a single-propeller configuration and subsequently extending the analysis to twin-propeller configurations. The analyses are performed for both rigid and flexible wings, with the latter designed such that whirl flutter governs the instability boundary. Results show that spanwise propeller placement strongly influences whirl flutter stability, with outboard locations exhibiting higher flutter speeds. Aerodynamic interactions between the wing and the propeller are found to be generally destabilizing, reducing the whirl
This paper presents an efficient numerical framework for prediction of broadband noise scattering through time-domain synthesis and propagation. For efficient scattering of broadband noise sources, a time-domain boundary element method is applied to propagate all frequencies together in a single computation. To obtain a time-resolved incident field without high-fidelity aerodynamic simulation, a stochastic broadband noise synthesis method is developed based on a semi-analytical airfoil broadband noise modeling approach. The framework is validated for airfoil trailing edge noise prediction, and the correspondence of the time-domain broadband noise synthesis method to existing semi-analytical broadband noise models is demonstrated. The framework is then applied to predict fuselage scattering of rotor tonal and broadband noise for a full-size urban air mobility concept vehicle. Significant differences are observed between the scattering effects in the tonal and broadband contributions.
This work presents the development of an interconnected gearbox drive system for a tandem rotor unmanned aerial vehicle (UAV) designed for a power rating of 20 kW per rotor. Development of the facility for dynamic testing of the interconnecting drive system is also presented. Tandem rotor configurations offer superior payload capacity and aerodynamic efficiency but pose challenges in transmission design due to the need for synchronized power distribution between counter-rotating rotors. The proposed gearbox employs a simple two-stage reduction system combining bevel and planetary gears to achieve compactness, high torque transmission, and ease of fabrication. A dedicated test rig is concurrently being developed to evaluate gearbox performance under variable torque and speed conditions for the first stage with the mechanical interconnection. The test set-up integrates a variable-speed drive, torque and vibration sensors, and a data acquisition system to measure efficiency, losses, and
When surveying the current landscape of Deterministic Ethernet avionics solutions in the aerospace industry, the three main technologies in the market are ARINC 664 part 7 rate-constrained Ethernet (commonly known by its trademark name "AFDX®"), TTEthernet (which combines ARINC 664 part 7 with Best-Effort Ethernet, while adding a new class of synchronous determinism defined in SAE AS6802 [Time-Triggered Ethernet]), and IEEE 802.1 Time-Sensitive Networking (TSN). No single deterministic Ethernet technology optimally satisfies certification, MOSA, and lifecycle goals across all avionics domains. Instead, successful digital backbones require intentional partitioning of responsibilities across technologies. This paper will seek to identify a number of those considerations and provide guidance on which technologies offer the best fit. After first opening with an explanation of the market forces driving the trends towards these technologies, this paper will delve into a short outline of each
This paper presents a wind tunnel investigation on the interactional aerodynamics of a slowed-rotor lift- and thrust-compounded helicopter model in high-speed forward flight. A systematic configuration study was conducted to isolate the aerodynamic contributions of the main rotor, wings, fuselage, and pusher propeller to the aft flowfield, measured using phase-resolved 2D-3C particle image velocimetry. Measurements were acquired at an advance ratio of 0.5 across multiple rotor thrust levels, lift offset trim states, and propeller rotational speeds. The fuselage induces a streamwise velocity deficit of nearly 50% of the freestream near the tail boom due to oncoming flow blockage. This deficit is modulated by the main rotor and wing configurations. The rotor slipstream partially alleviates the deficit by convecting high-speed freestream flow downwards. Lift offset in the asymmetric half-wing configuration suppresses the rotor wake influence, deepening the velocity deficit relative to a
A wind tunnel investigation to assess the impact of rotor-fuselage spacing on the development of the Vortex Ring State and flow topology is presented. Particle Image Velocimetry was utilised to investigate flow mechanisms across a range of rotor-fuselage spacings and descent ratios, which were compared to that of an isolated rotor configuration. Mean flow data was used to identify coherent flow structures, whilst flow unsteadiness was investigated through statistical analysis of the velocity fluctuations. It was found at cases of Vortex Ring State onset, the presence of the fuselage delays the development of the Vortex Ring State for all rotor-fuselage separation distances tested. Furthermore, certain cases of rotor-fuselage spacings display a rotor-fuselage aerodynamic interaction that results in an increased effective descent ratio.
OverFlight is an in-development graphical user interface (GUI) that implements a state-of-the-art rotorcraft maneuvering noise model using a source noise hemisphere approach coupled with the Aircraft NOise Prediction Program 2 (ANOPP2). This GUI stems from a demand for easy-to-use mission planning and community impact acoustic tools that can model the maneuvering flight of a rotary-wing vehicle. This paper covers the models used for the development of OverFlight and model validation efforts. Data from a joint NASA/Army flight test of an MD530F aircraft are used both for source noise hemispheres as well as maneuvering flight data. Analysis of the predicted maneuvering noise shows better agreement that traditional methods currently employed, while also demonstrating maneuvers where the underlying assumptions fail to hold.
Shrouded rotor configurations provide aerodynamic efficiency benefits that are valuable for aerial vehicles requiring high endurance in hovering flight. The effect of the shroud on the loads produced by a vehicle in response to cyclic pitch are not well known in literature. This paper aims to understand the magnitude and phasing of the steady hub loads produced by shrouded coaxial hingeless rotors in hover due to cyclic pitch. A shrouded coaxial rotor vehicle weighing 0.934 kg and with a rotor radius 0.138 m is used as the test platform. The rotors are operated at a tip Reynolds number of 70,000 and a tip Mach number of 0.18. First, the origins of steady hub loads due to cyclic pitch on a hingeless rotor are described using theory. To quantify the effect of the shroud, different configurations of rotors were tested by giving cyclic pitch to only one rotor. For the open hingeless rotor, cyclic variation in drag force at blade sections contributed to 55% of the steady lateral force. In
This work presents the development and application of a methodology for predicting fatigue life, implemented within the modern progressive failure analysis software tool CDMat, developed at the Advanced Materials and Structures Laboratory of the University of Texas at Arlington. CDMat is designed as an extension to the general-purpose finite element analysis program ABAQUS/Explicit. The set of user-defined subroutines for describing material behavior can be expanded by adding new subroutines. A recent development in CDMat is a computational model capable of predicting delamination crack growth under quasi-static and fatigue loading, based on a fracture mechanics approach using the J-integral. The J-integral is calculated by integrating stresses and displacements along a line defined by the negative gradient of displacements in the cohesive interface. Due to the large integration path, the J-integral allows for a highly accurate estimation of the energy release rate, which makes it
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
The safe integration of Unmanned Aerial Vehicles (UAVs) into shared airspace necessitates robust conflict detection and avoid (DAA) methods that scale effectively with multiple dynamic intruders. Geometric methods, such as those in the DO-365 standard, are provably safe for pairwise encounters but become intractable in dense environments. Conversely, applying kinodynamic motion planners designed for static obstacles to dynamic scenarios leads to unstable behavior, characterized by excessive re-planning and oscillatory motion, as they lack a predictive model of intruder trajectories. This paper introduces a closed-loop planning framework based on the Closed-Loop Rapidly-exploring Random Tree* (CL-RRT*) algorithm to prevent Loss of Well-Clear (LoWC) in multi-intruder scenarios. Our approach integrates a closed-loop dynamics model to guarantee dynamically feasible trajectories and incorporates a spatiotemporal planning strategy. A time-to-come metric is propagated from the tree root to
The impact of ship airwake on helicopter operations to rear flight decks has been a topic of much research over the past three decades. While generic ships have been developed over the years to enable analysis tool and knowledge development, actual ships can vary significantly, resulting in different airwake features. The study of variations in ship geometry is important both to understand how differences may impact operations, but also to understand the level of geometrical fidelity that is required on ship models undergoing analysis. In Canada, the newly launched (2018) Harry DeWolf-class Arctic Offshore Patrol Ships (AOPS) have unique features that have been studied for their impact on airwake characteristics. This paper explores different geometrical characteristics from the perspective of their operational impacts and also considering their importance for inclusion in simulation. The paper shows that turbulence level is the parameter most affected by the minor variations that were
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
Hybrid bearings, which pair traditional bearing-steel raceways with ceramic rolling elements, can offer improved performance over full-metal bearings, particularly in aerospace applications. Because rolling-element bearings are critical components, effective condition monitoring is essential to prevent in-flight failures and support proactive maintenance strategies. Wear-debris monitoring is widely used in these applications to detect and diagnose bearing fault modes. To compare degradation behavior and monitoring signatures, bearing life tests were conducted on hybrid and full-metal bearings under matched Hertzian stress conditions. The results showed that differences in degradation curves between the two bearing types were small relative to the overall variability in bearing life. Additionally, hybrid bearings that develop rolling-element pitting were observed to progress toward raceway spall formation. This paper was presented at ERF Forum 51 but has been updated with new findings
Urban Air Mobility (UAM) represents a paradigm shift in metropolitan transportation, introducing electric vertical takeoff and landing (eVTOL) aircraft into dense urban ecosystems. This transformation is driven by advances in electrification, digital infrastructure, and integrated airspace management. According to the U.S. Department of Transportation's Advanced Air Mobility National Strategy 2025, UAM is expected to become a cornerstone of multimodal urban transport, with commercial operations projected in multiple U.S. cities before 2030 [1].
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