Browse Topic: Terminology
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.
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.
Axial velocity measurements were performed in the wake of a hovering rotor with constant and sinusoidal cyclic pitch inputs ranging from 0.05/rev to 0.4/rev using a fixed, 2D-3C PIV system. Measurements were taken at 36 azimuths of the rotor with a constant cyclic input producing a pitching moment of CM = -0.00037. Using a Pitt-Peters definition, a longitudinal inflow state of λ1c = 0.0059 was extracted from the velocity measurements. A phase-resolved, undersampling approach was used to reconstruct the time history of the wake for the dynamic inputs. Simultaneous rotor hub loads measurements were used to obtain the frequency response of the longitudinal inflow state to pitching moment perturbations. The pitching moment perturbations ranged from ΔCM = 0.00027 at f=0.05/rev to 0.00046 at f=0.4/rev. The inflow perturbations ranged from Δλ1c = 0.0085 at f=0.1/rev to 0.0085 at f=0.4/rev. A first order transfer function was fit to the frequency response to compute Pitt-Peters dynamic inflow model parameters, but the low signal strength of λ1c produced high uncertainties in the model parameters.
In over actuated aircrafts a simple relationship between control inputs and forces/moments generated does not exist, however they have become very attractive for their wide range of applications. Control allocation aims at finding a unique surface control distribution as function of flight condition to perform the desired maneuver. The goal of this paper is to present a control allocation methodology applied on a generic over actuated aircraft aimed to determine the surface gearing matrix weights in different operative conditions to minimize the total power consumption. First, the non-linear model of the control forces and moments is derived for an over actuated aircraft. Then, two different optimization problems are introduced: the first to compute the trim equilibrium for any flight condition to minimize power consumption by the aircraft; the second to minimize the surface deflections required to produce desired control forces/moments starting from the trim point previously found. Finally, the optimized solution is subjected to engineering judgement to neglect the ineffective surfaces that do not provide a significant contribution to the required maneuver.
Launch, recovery, and deck handling operational performance on smaller ship platforms like Corvettes, Frigates and Destroyers are qualified as the most challenging tasks in the UAS ship-deployment of a VTOL Uncrewed Air System (UAS). One of the main hurdles is the random nature of seaway-created deck motions coupled with ship structure disturbed air wake patterns. The MoD has supported a range of work aimed at bringing Quiescent Period Prediction (QPP) technology to fruition. QPP firstly requires Wave Profiling RADAR to measure the sea wave system out to approximately 2km in the region around a vessel. Secondly these measurements are employed in a wave propagation model to predict the actual wave forces acting on a vessel. Using the wave predictions as inputs to a vessel model makes possible to predict the actual (deterministic as opposed to statistical) motions of a vessel. Wave systems naturally alternate groups of large waves with smaller waves, this property, combined with the predictive ability, allows to identify the quietest (most quiescent) periods in which to conduct wave limited naval operations. Naval mission planners in the Royal Navy, and elsewhere in the World, appreciate the need to maintain rapid, but safe, deck tempo. The fundamental concept is to measure remote sea surface profiles to predict the future wave forces acting upon a vessel. The objective is to expand ship operating deck limits to approximately Sea State 6+. The deck definitions generally empirically measured by using standard rating scales, are replaced by instrumented devices reporting the status of the deck prior to touch-down. In this paper, a thorough discussion describing the QPP deck measuring devices designed to replace piloted cueing is provided. Theory, previous simulation studies and current at-sea testing along with data results, are also discussed. To conclude, the interface of the deck measuring device into the next version of the UK UAS system, is provided. The results of the RADAR trial indicated that the RADAR data was reliable, with the RADAR images matching the physical map. The two-dimensional surface plot showed both the RADAR blocking fence along with an additional target. An additional observation concerning the operation over the deck whilst the ship is experiencing a quiescent ship motion period. The coupled secondary effect documents minimized air wake confusion. This is owing to fewer ship structure excursions into and out of the air flow. To better define deck airflow around the ship the integration of a Doppler LIDAR instrumented federate is proposed. This is meant to predict the future vessel air wake and look for quiescent periods in this paralleling the vessel motion QPP technique.
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.
ABSTRACT
This SAE Standard applies to cranes which are equipped to adjust the boom angle by hoisting and lowering means through rope reeving.
Illustrations used here are not intended to include all existing industrial or agricultural machines, or to be exactly descriptive of any particular machine. They have been picked to describe the principles to be used in applying this standard.
With the market introduction of the EC135 the bearingless main rotor (BMR) as a novel main rotor system was put into series production. Since then a chain of interconnected research programs led to the next generation of BMR. It now enhances the qualities of the H145 regarding the aspects of useful load, comfort of ride, purchase and maintenance cost as well as operational features. The design targets definition and their implementation by innovative solutions are summarized hereafter. The focus is put on the modular design of the main rotor system which is realized by an integrated flexbeam and control cuff assembly and a separate rotor blade joined together by a bolted connection using flat laminate lay-up instead of fiber loops. A detailed view is given on the development of the novel blade attachment from design considerations and manufacturing aspects over parametric subcomponent tests to full scale testing.
The first prototype SA340 flew the 7 of April 1967 The first prototype SA340 initially flew with a conventional tail rotor. There are more than 5200 helicopters flying today with this anti-torque concept. The first H160 prototype flew the 13th of June 2015 taking advantages of almost fifty years of continuous improvements in its global aerodynamic definition in the service of safety of customer operations. Three generations of Fenestron®, starting from the first Gazelle design take benefits of shroud improvements, dedicated airfoils and uneven spacing of the blade for external noise reduction. H160 is today the flagship of the Airbus Fenestron® Fleet.
This paper reports an overview of the experimental and analytical activities carried out in relation to the identification of the more severe limit load conditions for the AW169 Main Rotor components, with particular attention to the Main Rotor Tension Link. The entire interdisciplinary process involving the set up as well as the validation of the aeroelastic software used, the setup of the validated FE Model of the Tension Link related to both the helicopter installation and the Test Rig, the definition of the criterion used to select the more severe limit conditions will be extensively described. Particularly, the definition of a simple criterion able to restrict the number and the typologies of conditions to be simulated proved to be very useful in reducing the computational time involved in the simulation of several dozen conditions. The approach described here, although related to a specific part with specific characteristics, can be generalized to any other complex part loaded by multiple forces and tested in a Test Rig which, due to implementation constraints, cannot fully represent the real helicopter installation.
Two sets of visual symbology in conjunction with two display types (helmet mounted and panel mounted) were examined for their usability in maintaining flight performance within a simulated degraded visual environment. Eight rated Army Aviators completed a series of flights using the two symbology sets with each display type. Flight performance data was collected and used to assess performance resulting from symbology and display used. Overall, the assessment found one symbology set to result in better performance across several phases of flight and no significant differences due to display type, although a few interactions between symbol set and display type are noted.
An alternative probabilistic approach is proposed to assess the reliability of rotorcraft structures. According to the approach, safe boundaries of reliability predictions (i.e., conservative ones with additional safety margins) are calculated instead of exact values of the reliability as usually estimated in conventional analysis. Due to additional safety margins, these boundaries are suggested for practical engineering applications. The proposed approach is based on two main ideas, namely a) prediction of a relatively small population of independent coarse estimations of reliability and b) application of sampling methods to predict reliability for each individual coarse estimation. Robustness and convenience of the developed approach and its computational implementation is demonstrated for four scenarios considering two problems (simplified analytical and realistic FEA-based ones) under two sets of input data providing probability of failure (POF) close to 1e-6 and 1e-9, respectively. High accuracy of predictions according to the developed approach is independently verified by comparison with known “exact” references: closed-form solutions for the analytical problem and by direct MCS for the numerical one. The proposed approach can be recommended as an efficient practical solution for a broad range of reliability assessments of rotorcraft structures requiring both i) low POF (e.g., below 1e-6) and ii) relatively complex time-consuming structural definitions (e.g., compute times in hours for each quasi-deterministic simulation).
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