Browse Topic: Environment
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.
TEST https://wcm14-tst.cld.sae.org/site/binaries/content/gallery/mobilus-brx/digital-supplements/software-diagram.png/software-diagram.png/sae%3Amedium
An experimental investigation was conducted to explore the loads, acoustics, and tip vortex trajectories of coaxial counter-rotating (CCR) rotor with unequal upper and lower radii. The upper and lower rotor radii were tested both at the nominal radius of 1.108 m, and also with a lower rotor radius of 90% nominal radius, for a constant rotor speed of 1180 RPM and a constant inter-rotor spacing of z/R = 0.108. Rotors were torque balanced and tested for a range of upper rotor collective pitch from -2◦ to 10◦ . The power required for both CCR systems was within 0.9% for most trim conditions, and equal thrust was produced at upper rotor collectives of 6◦ and 8◦ (within 1.0%). At low loading conditions the unequal radii configuration produced more thrust for the same power due to a reduction in profile drag. The overall sound pressure level (OASPL) was lower for the CCR rotor with shortened lower rotor blades at all angles of elevation. Larger reductions in A-weighted OASPL(A) were observed, due to a larger contribution of broadband noise to the total OASPL(A).
As per Committee/Henry E. Harschburger recommendations
SAE J1939-03 provides requirements and guidelines for the implementation of on-board diagnostics (OBD) on heavy duty vehicles (HDV) using the SAE J1939 family of standards. The guidelines identify where the necessary information to meet OBD regulations may be found among the SAE J1939 document set. Key requirements are identified here to ensure the interoperability of OBD scan tools across individual OBD-compliant vehicles.Market-defined regulations permit the use of SAE J1939 to meet OBD requirements. Implementers are cautioned to obtain and review the specific regulations for the markets where their products are sold. This document is focused on guidelines and requirements to satisfy the State of California Air Resources Board (CARB), the authors of 13 CCR 1971.1, United States Environmental Protection Agency, Euro IV and V requirements from European Commission directives, and UN/ECE WP 29 GRPE WWH OBD Global Technical Regulation (GTR).
This study provides a comprehensive framework for establishing land use compatibility guidelines specific to vertiports serving electric Vertical Takeoff and Landing (eVTOL) aircraft within urban settings. Recognizing critical gaps in current regulatory standards, the research systematically integrates analyses of accident risk, noise propagation, and aerodynamic impacts—including downwash and outwash—to delineate compatibility zones around vertiports. Employing an artificial intelligence (AI) augmented system, the study conducted safety and hazard assessments, various quantitative analyses, and simulations to identify spatial constructs of operational risks and environmental impacts. Results indicated significant discrepancies between existing aviation infrastructure guidelines and the unique operational characteristics of eVTOLs, necessitating revised zoning parameters. The proposed multi-tiered safety zoning framework provides precise, evidencebased recommendations for urban planners, enhancing safety, minimizing noise impacts, and ensuring environmental sustainability. Ultimately, this research offers policymakers and stakeholders practical tools for integrating advanced air mobility infrastructure safely into complex urban landscapes.
As part of a human factors research project aimed at optimizing technical documentation used in helicopter maintenance with multimedia elements, we compared different instruction formats to observe their effects on the performance of an assembly task. This task offers us the opportunity to test procedures that call for similar actions as a maintenance task (e.g., localization, action sequencing, assembly). Static (i.e., image and image with text) and dynamic instruction formats (i.e., video, video with text and video with audio) were compared to determine if dynamic formats allowed a better motor performance of the task for assembly reaction time (time needed to complete the assembly) and accuracy. We were also interested in how the use of the text instructions interacted with both visual dynamic and static instructions. Reaction times were recorded and measured with eye tracking data. Subjective data was collected in questionnaires during and after the experiment. Results showed significant differences in the time spent on the instructions and the time spent on the assembly, depending on the format of instructions. Overall, assembly time is shorter with video instruction formats, but videos took longer to be consulted than static formats. Results also showed a difference in the number of actions required to do the assembly. Videos facilitated the right path of action sequence in comparison with static formats. With the analysis of both subjective and objective data, the results give us a better idea of the advantages and drawbacks of using dynamic formats in technical documentation.
The biography of Henrich Focke is well known and documented. During a small period from October 1954 to February 1956 he held lectures at the Technical University of Stuttgart during the winter semester. In the summer period he returned to Brazil for continuation of his contract work on the "Convertiplane" (a quad-tiltrotor aircraft) and the "Bei-jaflor" (a small single rotor helicopter). The topic of Focke's lecture in the winter semester 1954-55 was "Design of Fixed-Wing Aircraft", but the lecture manuscript of it is unavailable. In the following period 1955-56 Focke lectured about "Helicopter Design" and the manuscript was recently found in the central archive of DLR. It covers 123 pages of text with sketches and graphs and provides deep insights into the helicopter design philosophy of Henrich Focke.
Civil and military rotorcraft operators desire enhanced capabilities from their vehicles in terms of mission efficiency, effectiveness, productivity, and availability. A critical element of this challenge is associated with providing cold weather availability. Currently, cold weather operations are enabled by regulatory actions leading to Limited Approvals, Qualifications, Clearances, and Restrictions. Cold weather certification (clearance of a new aircraft) and continuing airworthiness (maintaining effectiveness of fielded aircraft) are data driven processes. This work provides guidance on an Icing Encounters Survey (IES) based data gathering method supporting continuing airworthiness organizations in improving fleet safety and capabilities during cold weather operations.
The influence of ground, wall, and corner boundaries on multirotor vehicle performance was investigated through a series of controlled flight tests. Changes in rotor inflow profiles were represented by near-field rotor pressure measurements captured by a custom Kiel probe wake rake. Ground effect was characterized by reduced thrust and power requirements, primarily driven by the vehicle fuselage, which induced regions of reduced pressure and increased flow unsteadiness around the airframe. Operating near a wall boundary was found to restrict airflow into the portion of the rotor disk closest to the wall, leading to increased power requirements to maintain hover and a consequent reduction in performance. While vehicle orientation had minimal impact on overall rotor performance, it did influence local rotor inflow behavior near the wall, depending on the relative position of the interaction region formed with adjacent rotors. As the vehicle descends from the isolated wall effect into corner effect, created by the intersection of the wall and ground, an exchange between the dominating ground and wall effects is observed, with corresponding ground heights and wall distances identified.
Heavy wind and high sea states pose challenges to operating unmanned rotorcraft on-board a naval ship, in particular the recovery phase. A novel autonomous landing strategy for unmanned rotorcraft is proposed and investigated. The new landing strategy makes use of a prediction of the future deck motion based on a sensor on the ship deck. The study is based on a nonlinear simulation environment which includes the dynamics of a 100 kg unmanned helicopter and the dynamics of an ocean-going patrol vessel of the Royal Netherlands Navy. The performance of the autonomous landing strategy is evaluated for a wide variety of environmental conditions (sea state) and operational conditions (ship speed and heading). The results clearly indicate that the environmental conditions have a strong influence on the landing performance in terms of touchdown velocity and landing accuracy. Furthermore, the autonomous landing strategy is effective in reducing the mean and peak value of the touchdown velocity compared to a standard automatic landing strategy. A reduction of as much as 60% in landing impact is observed for the worst case environmental and operational condition considered. The results confirm and underline the potential of the novel landing strategy.
Test Scope
ABSTRACT Rubber tracks are now extremely competitive for vehicles up to 50 tons and fully fielded on 39 ton vehicles. They represent the best of what technology can offer for tracked vehicles, in terms of high durability, performance and low life cycle cost. This is mainly attributed to the optimization through the five (5) technological tools described in this paper. Better from its numerous distinctive advantages, rubber tracks can be adapted to suit virtually any specific need. This ductile rubber track technology can be shaped to match today’s requirements, with the help of advanced rubber compounding and computer simulations.
Time-resolved background-oriented schlieren (BOS) data are used to calculate the two-dimensional velocity field in the wake of free-flying full-scale helicopters in ground effect. The calculation is performed based on the density gradient pattern of the helicopter engine exhaust gas passing the BOS field of view. A classical BOS evaluation allows the visualization of density gradients such as vortices and the exhaust plume. The result is the BOS displacement field. Applying the two-dimensional divergence to this data results in a pattern that is constant in shape across multiple BOS images, but convects downstream with the outwash velocity of the helicopter. Using this data as input to a second, timeresolved evaluation, quantitative two-dimensional velocity fields are calculated. Choosing an appropriate strategy for preparing and evaluating the data is critical to reliable velocity estimation. Another important aspect is to distinguish between reliable velocity data and erroneous results in areas of reduced signal intensity due to a lack of thermal structures. The velocity data obtained are compared with an analytical outwash model and constant temperature anemometry data acquired simultaneously with the BOS images. The data show good quantitative agreement in areas of sufficient thermal structures within the field of view.
An experimental investigation was conducted on a 1.108 m radius coaxial co-rotating (or stacked) rotor and a coaxial counter-rotating (CCR) rotor of identical geometry to compare the acoustics and loads of both rotor configurations in hover. The rotors were operated at a tip Mach number of 0.40, tip Reynolds number of 765,000 and an axial spacing of 1.55 chord lengths, and the index angle between the upper and lower blades of the stacked rotor was varied. The overall sound pressure level (OASPL) was significantly larger for the CCR rotor. For example, total rotor noise at -45◦ angle of elevation was 6 dB greater for the CCR rotor than the stacked rotor at 8◦ collective. These increases in OASPL were driven by large increases in tonal noise for the CCR rotor, of up to 10 dB higher than the stacked rotor at some angles of elevation. This was attributed to additional tonal noise occurring at harmonics of 2Nb/rev, due to vibratory loads from 2Nb/rev blade crossings. The results of the experimental study suggest that, in terms of reduced noise and increased hover efficiency, the stacked rotor is preferable to the CCR rotor for eVTOL vehicle configurations that implement compact or closely spaced designs.
ABSTRACT A full-scale Reynolds number water tunnel experiment was performed to generate a data set used to analyze the effects of helicopter rotor hub wake impingement on a canonical horizontal stabilizer. The experiment was designed and performed in the Pennsylvania State University Applied Research Laboratory Garfield Thomas Water Tunnel, where a 10.5 inch constant chord stabilizer was placed in the 48-inch diameter test section downstream of a 1/4 scale helicopter hub. Two rotor hubs were tested, a baseline configuration and a low-drag model. The stabilizer was mounted in the long-age wake. Lift, pitching moments, and unsteady pressures were measured on the horizontal stabilizer at a Reynolds number of 0:9x10⁶, 1:8x10⁶ and 2:7x10⁶, corresponding to hub diameter-based Reynolds numbers of 2:2x10⁶, 4:3x10⁶, 6:5x10⁶ and rotor advance ratios of 0.1, 0.2, and 0.3. The hub-wake interaction results were compared to a baseline airfoil test, which was performed without a hub upstream. Pressure sensors were used to evaluate wake unsteadiness impinging on the horizontal stabilizer. The horizontal stabilizer in clean flow exhibited lift and pitching moment in agreement with XFOIL predictions. With the low-drag hub upstream it measured lift fluctuations at a frequency of 2/rev, 4/rev, 8/rev and 12/rev. Downstream velocity and pressure fluctuations of 2/rev 4/rev and notably 6/rev were measured with the baseline hub upstream. Drag reduction on the low-drag hub was measured to be >25% compared to the baseline hub at full-scale Reynolds number. Both drag and wake harmonics measured at the hub and downstream on the stabilizer were found to be dependent on the upstream hub geometry. Pressure frequencies taken on the horizontal stabilizer yielded similar results and were consistent with those measured via the force balance.
Installation effects of the Volocopter 2-X beam structures are studied by performing high-fidelity CFD simulations of a single and three-rotor configurations in hover. The studied cases are compared with simulations without airframe to investigate the installation effects. In addition, the noise emission of the configurations is simulated by using a Ffowcs Williams-Hawkings based CAA code. Scattering effects are also included by using a BEM code. The rotors are simulated at an identical RPM and are placed in their mounting position. Furthermore, an additional setup with individual rotor RPMs is simulated for the three-rotor configuration. The installation mainly affects the rotor wake, thrust and pressure fluctuations on the rotor, while the integral aerodynamic quantities remain almost unchanged. This resulted in additional oscillations in the acoustic pressure signal. Overall, the installation increases the OSPL by about 1.5 dB, but has a greater effect on the 3-20 harmonics. The simulation data were compared with the Volocopter measurements and showed good agreement. For the three-rotor configurations, the rotor-rotor interactions were found to be dominant for the aerodynamic and acoustic performance, while the installation effects only locally influenced the noise emission by 3-4dB.
Army rotorcraft operations demand precision and adaptability to navigate challenging terrain, respond to real-time mission requirements, and ensure time-to-target arrival. Navigating complex terrain, making real-time trajectory adjustments, and ensuring timely arrival at designated objectives while considering other problems are challenging. This paper focuses on the concept of 4D conformal pilot cueing that can facilitate a significant reduction in pilot workload. To enhance the rotorcraft operations with Army scenarios, a visual cueing method based on Tau Theory for obstacle avoidance is proposed so that the pilot can make a coordinated turn away from the obstacle and safely change the helicopter's trajectory to avoid the collision. To demonstrate the visual cueing method, desktop simulations are performed in Matlab/Simulink environment using simulated pilots.
Airfoil optimization for rotor blades is a critical endeavor aimed at enhancing aerodynamic performance and reducing noise. This paper employs a Kriging surrogate model combined with a multi-objective genetic algorithm to optimize thrust, power, and broadband noise. Three airfoil parameterization methods including ParFoil, PARSEC, and CST are compared when used to generate various airfoil shapes for the surrogate model and optimization process. We utilize low-fidelity aerodynamic tools such as XFOIL and blade element momentum theory for aerodynamics. In addition, acoustic modeling is conducted using Lee's wall pressure spectrum model alongside Amiet's trailing-edge noise model. The paper focuses on small-scale rotor configurations, specifically an ideally twisted rotor using the NACA 0012 airfoil and a modified XV-15 blade. Both blades are used as baseline models for hover optimization. The optimization of the ideally twisted rotor across various parameterization methods demonstrates a significant reduction in A-weighted overall sound pressure level by approximately 4.0 dBA. The primary contributors to this noise reduction are identified as a decrease in the chordwise pressure gradient and wall shear stress, which are key factors that contribute to the wall pressure spectrum and resulting trailing-edge noise. Similarly, the optimization of the modified XV-15 blade using the ParFoil method achieves a notable decrease in noise of 3.5 dBA. Further analysis is extended to axial flight conditions, with axial velocities of 5.0, 10.0, and 20.0 m/s, to simulate vertical climb. The results show that these hover-optimized blades are capable of sustaining noise decreases of 3.0-4.0 dBA compared to the baseline, provided that the thrust coefficient is maintained through adjustments in collective pitch.
Deos includes an industry standard lightweight TCP/IP stack (LwIP) with a DAL-A sockets library so it can provide data transport during in flight or on ground as part of its standard package. While it may have high data integrity (e.g., through CRC or other such mechanisms), TCP/IP over Ethernet is a non-deterministic protocol. As such, it is not suitable for avionics applications that require determinism or high robustness. In contrast, there are several are several redundant and deterministic data network technologies such as ARINC-664/AFDX, time triggered ethernet (TTE), and time sensitive networking (TSN). These interfaces are based on switched Ethernet technologies and can include system redundancy such that they are applicable for aircraft data network applications. Their feature set enables them to be used as a digital backbone for aircraft control and other applications where both integrity and availability are essential. Each of these solutions generally requires specific end point hardware to implement the protocols in firmware in order to meet the required communication timing and throughput. The implementation of the software device drivers for these technologies on Deos can leverage Deos' I/O Infrastructure (IOI) data distribution service for data decoupling. IOI is a DO-178 DAL-A module that can distribute data based on XML configuration files that specify the data paths, access control and optionally data formatting. It implements an inter-partition communications data interface between avionics applications including ARINC-653 partitions using the ARINC-653 APEX API sampling/queueing ports. Together, these features allow developers to readily adapt to changes in communication structures all through XML configuration files, versus recompiling which would impact the verification evidence of the module. This paper will talk about the different networking standards and how the use of Deos' IOI provides a way for the system to easily adapt to different network configurations without causing the driver library or end application(s) to be modified and thereby minimize change impact for reuse/reverification.
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 This study examines the performance of a quadcopter in edgewise flight conditions with flow simulated using the commercial Navier-Stokes solver, AcuSolve, with a Detached Eddy Simulation (DES) model. The rotating volume around each rotor interfaces with the remainder of the computational domain using a sliding mesh. Simulations were conducted for an AeroQuad Cyclone quadcopter at 10 m/s forward speed, 5 deg nose-down pitch attitude, operating in both cross and plus configurations. From the results it was observed that in the cross configuration, the aft (South) rotors showed a 19% reduction in lift (relative to an isolated rotor at the same forward speed, pitch attitude and RPM), with an associated 3% reduction in torque. The loss in lift was primarily at the front of the aft rotors due to the downwash induced by the forward rotors, therefore reducing the aft rotor nose-up pitching moments by 54% (relative to operation in isolation). In the plus configuration, sections of the East and West rotors close to the aircraft center-body operate in upwash induced by the North rotor, increasing the lift generated by 5.5% and 7.6% respectively, relative to operation in isolation. The South rotor sees both upwash (and increased lift) along the advancing and retreating edges induced by the East and West rotors, as well as downwash at the front (and reduced lift) induced by the North rotor, but no significant overall changes in thrust or torque.
ABSTRACT The paper investigates the influence of a dynamic active twist control on BVI noise in descent flight for a Mach-scaled Bo 105 model rotor. Therefore, a numerical study has been carried out with DLR's aeromechanics rotor code S4. In addition, sound pressure levels have been computed with DLR's acoustic code APSIM. The intensity of BVI noise is determined by different vortex parameters as well as the blade-vortex miss-distance and the BVI location. In this paper, all parameters that influence the intensity of the radiated BVI noise are analyzed. The analysis is carried out for a rotor shaft angle of attack of αᴿₒ = 4° for which the most intensive BVI noise was identified for the passive rotor blade. The study lays emphasis on the effect of different control amplitudes and phases but concentrates on a control frequency of the third multiple of the rotor rotational frequency for which highest reductions in BVI noise were identified.
ABSTRACT This paper introduces the Shape Adaptive Blades for Rotorcraft Efficiency (SABRE) Horizon 2020 research program and presents initial comprehensive analysis results on the efficacy of adapting blade shapes as a means of reducing rotorcraft power requirements and emissions. The aims of the research program are introduced, followed by discussion of the six different morphing concepts that will be explored. The morphing mechanisms are based on active camber, chord extension, twist, and active tendon morphing technologies. SABRE will explore the use of these concepts individually and in combination, for rotor quasi-steady configuration-type morphing and up to 2/rev actuation of some of the mechanisms, with the objective being to find the best balance between emissions reductions versus complexity and added weight. Initial investigations into the potential power reductions compared to the baseline full-scale BO-105 main rotor achievable with the morphing concepts were performed using Blade Element Momentum Theory and a comprehensive analysis model that was developed using CAMRAD II. The analytical model was validated by full-scale rotor wind tunnel measurements. A combination of active twist and active chord extension achieved up to 11% performance gain in hover. Active camber morphing performance was very sensitive to the combination of deflection, morphing section radial length and placement on the blade, as well as the actuation phasing and blade loading coefficient. The active camber morphing showed power reductions of up to 5.5% in hover and 5% at an advance ratio of 0.313 with a 2/rev actuation, while the active tendon concept showed the capability to change the dynamic response of the rotor blade.
This study examines the acoustics of a wing operating in the wake of a propeller. The propeller wing system is simulated at 24 knots cruise and 8° wing angle of attack. The propeller is simulated using an actuator line model, while the wing is simulated using two different turbulence models: a DDES turbulence model and a higher fidelity LES model. Chordwise compact loads, on-wing pressure surfaces, and pressure surfaces at distances of 2.34% and 10% thickness around the wing surface are used as inputs to PSU-WOPWOP to predict noise at an observer below the wing. Using on-wing surface pressures, the LES broadband noise predictions are 13.5 dB higher than DDES. Chordwise compact loads result in lower noise predictions than on-wing surface pressures, by 11.3 dB for LES and 2.3 dB for DDES. Using off-body pressure surfaces, DDES results remain similar to noise predictions from on-wing pressure surfaces, but with LES the broadband noise predictions are about 2.5 dB lower.
Corrosion occurs in diverse environments mainly on metallic parts. Helicopters are made of a huge percentage of metallic parts and need to have several maintenance steps to guarantee its functioning and its durability. The military helicopters are flying in different kinds of environment, which cover large spectrum of severity of the atmospheric corrosion [1]. In maritime conditions, the most influencing factor is the Time of Wetness, which is a direct result Relative Humidity and Salt loading. The main material used for aircraft and that is suffering from corrosion is aluminium. There are plenty of data to follow the corrosion as a function of the environmental conditions, mainly on the sensitivity with sodium chloride, Relative Humidity, film thickness, etc... [2][3]. The maintenance efficiency on helicopters is dependent on the environmental severity. The U.S. armed forces estimate $10.2 billion in corrosion costs for their aviation and missile fleets during 2016 [4] [5] [6]. The aim of the present analysis consists of defining the Condition Based Maintenance related to corrosion risk to better apply a maintenance program when it is really needed.
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