bluuebunny/crossref_metadata_2025 huggingface dataset:
New dimensions towards the restaurant waste management based on black soldier fly larvae (BSFL, Hermetiaillucens) model in Ratnapura district
Authors: Ellawidana E. W. D. M. , Magamage M. P. S.
Published: July 2023

The uncontrolled waste generation is a prevailing environmental concern where waste management is a critical issue in Sri Lanka. Even though different methods are practicing, insect-basedbio-degradation is forthcoming. Black soldier fly larvae (BSFL,Hermetia illucens) based emerging technology has recognized for the conversion of biodegradable waste into potentially more sustainable and marketable nutrient rich compost and animal feed rich with crude proteins. The study aims evaluate the potentials to introduce BSFL based biodegradation and to upgrade protein livestock feed sources by overwhelming urban catering bio-degradable waste in Ratnapura, Balangoda and Embilipitiyaurban council areas. Eighty-eight questionnaires were administrated through random sampling and the results were interpreted by descriptive statistics and bivariate correlation. More positively 97.7% were having the waste collection service supplied by local authorities (LA) with 93.2% daily collection. Importantly LA had a policy to collect the separated waste only. Even though 98.8%, 56.8% and 92.0% of the respondents were not known regarding BSFL protein production, live feeding and composting, 55.7% were willing to produce BSFL by their own bio-degradable waste. 46.6% and 71.6% were willing to sell 1kg of compost and BSFL larvae by Rs. 100-Rs.200 price for expected protein upgrade program in future. Further 60.2% were willing to use a BSFL based compost bin where it was requested to be compatible with the limited space. Since locally it is hardly evidenced regarding this insect-based technology, correlation results indicated the need of more awareness mainly BSFL bio-conversion and relevant technical knowhow procedures along with popularize BSFL based protein production.
Attack Helicopter Generations
Authors:   The Boeing Company, Leong Michael
Published: July 2023

Attack helicopters have gone through several notable changes in development and capabilities throughout their history, changes which are continuing to this day. These changes can be captured in distinct generations of attack helicopters, with significant similarities to generations of fighter aircraft development. Understanding the technological development contained in each generation of attack helicopters gives a relative comparison of the capabilities contained in each and the technology trajectory of improvement. This paper will attempt to categorize attack helicopter development by generations, providing the various characteristics and rationale for each, as well as defining the implications of this development for current design and future attack helicopter improvements.
A Design Worthy of Success: Bernard W. Sznycer, Selma G. Gottlieb and the Intercity SG-VI
Authors:   Canada Aviation and Space Museum, Fortier Renald
Published: July 2023

As imbedded as it is in technology, the history of flight is also chock full of people stories. The history of the helicopter, one of the most versatile flying machines ever designed, abounds in such stories. This text looks at the development of Intercity Airlines Company's SG Mark VI by a unique team based for a time in Montreal, Quebec. Bernard W. Sznycer and Selma G. Gottlieb conceived one of the most advanced and innovative helicopter of its day. Designed to minimize vibrations and facilitate production, the SG Mark VI first flew in July 1947. Canada's Department of Transport awarded a Certificate of Airworthiness to a second prototype, in April 1951. The SG Mark VI was the first helicopter designed within the British Commonwealth of Nations to be so honored. Sadly, by then, American helicopters all but dominated the civilian and military markets. The SG Mark VI was abandoned during the winter of 1953-54 and both Sznycer and Gottlieb returned to the United States.
Signal Processing to Reduce the Effect of Gear Dynamics
Authors:   GPMS In, Bechhoefer Eric ,   Turkish Aerospace, Ozturk Yalin
Published: July 2023

An improved conditioning monitoring technique is provided for rotating components in gearboxes that account for gear system dynamics. A rotation rate for the component is generated from vibration data by estimating the rotation rate based on a tachometer measurement of another shaft and the shaft ratio. This estimated rotation rate is used, together with the known configuration of the component, to estimate a known gear mesh frequency of the component. By filtering for a range of frequencies around the gear mesh frequency based on variation in the shaft rate, the gear mesh frequency can be determined, and from that signal, an actual rotation rate for the component can be determined. The exact rate can then be used in deriving an analytic vibration spectrum for the component that is not degraded due to gear system dynamics effects. Further, this allows the calculation of the gearbox transfer function.
Rotor Fault Detection and Identification on a Hexacopter under Varying Flight States Based on Global Stochastic Models
Authors:   Rensselaer Polytechnic Institute, Dutta Airin , McKay Michael , Kopsaftopoulos Fotis , Gandhi Farhan
Published: July 2023

This work introduces the use of "global" stochastic models to detect and identify rotor failures in multicopters under different operating conditions, turbulence, and uncertainty. The identification of an extended class of time-series models known as Vector-dependent Functionally Pooled AutoRegressive models, which are characterized by parameters that depend on both forward velocity and gross weight, using scalar or vector aircraft response signals under white noise excitation has been described. A concise overview of the residual based statistical decision making schemes for fault detection and identification of rotor failures is provided. The scalar and vector statistical models, along with residual variance and residual uncorrelatedness methods were validated and their effectiveness was assessed by a proof-of-concept application to aircraft flight for healthy and faulty states under severe turbulence and intermediate operating conditions. The results of this study demonstrate the effectiveness of all the proposed residual-based time series methods in terms of prompt rotor fault detection, although the methods based on Vector AutoRegressive models exhibit improved performance compared to their scalar counterparts with respect to their performance in identifying rotor failures in the post-failure controller compensated state.
Towards Unified Probabilistic Rotorcraft Damage Detection and Quantification via Non-parametric Time Series and Gaussian Process Models
Authors:   Rensselaer Polytechnic Institute, Amer Ahmad , Kopsaftopoulos Fotis
Published: July 2023

The complex dynamics of rotorcraft structures under varying operational and environmental conditions demand the development of accurate and robust-to-uncertainties structural health monitoring (SHM) approaches. The inherent uncertainty within monitoring data makes it difficult for conventional methods to accurately and robustly detect and quantify damage without the need for a large number of data sets. In addition, due to the time-varying nature of rotorcraft operations, such conventional metrics might still fail even with abundance of data. In this paper, we propose a unified probabilistic damage detection and quantification framework for active-sensing, guided-wave SHM that focuses on monitoring rotorcraft structural "hotspots". The proposed framework involves three stages: The first stage incorporates statistical damage detection based on stochastic non-parametric time series (NP-TS) models of ultrasonic wave propagation signals within a hotspot sensor network configuration. The second stage involves the statistical path selection, where a NP-TS representation is used for the sole purpose of identifying damage-intersecting signal (wave propagation) paths, that is the paths that are most sensitive to damage, in order to use them in the subsequent damage quantification stage. That last stage achieves probabilistic damage quantification, where the results of the NP-TS models are used to train Bayesian Gaussian Process regression and classification models. This unified framework ensures accurate and robust damage detection and quantification in a data-efficient manner since only damage-intersecting paths are selected and used in the analysis. The performance of the proposed framework is compared to that of conventional state-of-the-art damage indices (DIs) in detecting and quantifying simulated damage in two representative coupons: a Carbon Fiber Reinforced Polymer (CFRP) coupon and a stiffened aluminum (Al) panel. It is shown that the proposed framework outperforms conventional DI-based active-sensing guided-wave SHM methods.
XV-15 Tilt Rotor Research Aircraft Photogrammetry and Metrology Measurement
Authors:   NASA Ames Research Center, Cummings Haley , Dominguez Michelle , Solis Eduardo , Silva Christopher , Bowman Belen , Burek Shirley
Published: July 2023

A new measurement capability was created by combining photogrammetry and metrology techniques to accurately measure one half of the XV-15 Tilt Rotor Research Aircraft at the Smithsonian’s Udvar-Hazy museum. The challenges imposed by the fuselage and surrounding environment at Udvar-Hazy were overcome by careful application of photogrammetry and metrology techniques. Data analyses and processing included the use of multiple reverse engineering programs to accurately generate a complete 3-dimensional water-tight geometry of the aircraft and rotor blade. This paper describes the photogrammetry and metrology measurement systems, technology and hardware set-up, data analysis and processing methods, future work, and lessons learned. In addition, selected measurement results of the fuselage and rotor blade are presented.
Utilizing Casting Technologies on Legacy Part
Authors:   Sikorsky a Lockheed Martin Company, Woodworth Heather , Featheringham Andrew
Published: July 2023

Sikorsky has developed a specification outlining the use of three casting technologies: simulation, additive manufacturing of the mold and low pressure casting. This specification has been used in the past on new development projects with positive results, reducing lead times and number of pours to produce a useable part. When the S-92 program needed to develop a second source for a casting, they worked with Magellan Aerospace to implement the specification. The project proceeded on time with all castings able to be used. Some elements of the specification were modified to work with a legacy part design, including the use of statistical process controls to reduce variability in crucible pouring.
Enhancement and Validation of VPM-Derived State-Space Inflow Models for Multi-Rotor Simulation
Authors:   Advanced Rotorcraft Technology Inc., Gladfelter Matthew ,   US Army CCDC AvMC, Tischler Mark ,   US Naval Academy, Juhasz Ondrej , He Chengjian , Chang Chongseok , J. Mark
Published: July 2023

State-space inflow models have long been the standard for rotor wake modeling for flight dynamics and control simulation. As rotorcraft design continues to trend toward Future Vertical Lift (FVL) multi-rotor configurations in order to overcome the limitations of traditional design, the use of state space inflow models must similarly evolve to capture the complex aerodynamic interactions inherent to these new rotorcraft configurations. There is a demand for a state-space inflow model that accurately captures the significant aerodynamic interactions that occur between multiple rotors, ducted fans, wings, and complex airframes that preexisting inflow formulation fails to address. This paper discusses the ongoing effort to establish a robust methodology for deriving a state-space inflow model suitable for FVL applications from first-principle based viscous Vortex Particle Method (VPM) using the CIFERR system identification tool. The paper focuses on areas of enhancement that expand the identified inflow model's accuracy and usefulness as a tool for flight dynamics simulation of multi-rotor configurations. First, the effects of wake distortion due to rotor tip-path plane (TPP) rotation are thoroughly investigated for a co-axial configuration across a number of airspeeds and implemented into the inflow model formulation for improved simulation accuracy. Next, the rotor interference on the aerodynamic surfaces and the fuselage is explored, with attention placed on addressing this interference as a unified formulation. For the rotor interference on fuselage (3-D body) estimation, investigation of improvement through multi-point sampling is performed. The paper also examines the control design application through constructing the linear time invariant aircraft model with integrated state-space inflow model and verifying the accuracy of gain and phase margins and crossover frequencies. For each of these areas of investigation, the impacts on precision flight dynamics simulation are assessed through frequency and time domain response analysis and comparison to the simulation with first principle based VPM. The validation results of the predicted response data show excellent agreement with VPM simulation and further justify this method of inflow model identification as an effective tool for multi-rotor and FVL applications.
UAV Dynamics and Electric Power System Modeling and Visualization using Modelica and FMI
Authors:   Rensselaer Polytechnic Institute, Podlaski Meaghan , Vanfretti Luigi , Nademi Hamed , Chang Hao
Published: July 2023

This paper presents an object-oriented, equation-based framework for multi-engineering modeling of a quadrotor UAV, which includes the rigid body dynamics, simplified aerodynamics, gyroscopic effects, electrical power system and battery losses, and DC motor dynamics. An open-source drone modeling library is introduced by explaining the mathematical models and multi-domain components used to model the drone. Animation and visualization techniques for the drone using CAD models are also introduced and explained. The proposed drone model is simulated under different flight scenarios using motor and power system models with different levels of detail, aiming to provide better means for design and understanding, of multi-engineering aspects of UAVs. This model provides a foundation for future UAV open-source model development, electrified power propulsion design, visualization and interaction, and system identification.
Redistributed Pseudoinverse Control Allocation for Actuator Failure on a Compound Helicopter
Authors:   Rensselaer Polytechnic Institute, Vayalali Praneet , McKay Michael , Gandhi Farhan
Published: July 2023

The present study focuses on applying a redistributed pseudoinverse control allocation method on a 20,110 lb compound helicopter in order to utilize the redundant control effectors in feedback control pre- and post-actuator failure. A range of tolerable positions for locked-in-place actuator failures is established for the aircraft at a cruise speed of 150 knots. A model following linear dynamic inversion control system is implemented for the nonlinear simulation model. Stability margins, phase delay, and bandwidth evaluated for the longitudinal and lateral axis according to ADS-33E specifications show level 1 for most cases except minimum failed aft actuator position (level 2 stability margin) and maximum failed stabilator (level 3 stability margin). Nonlinear simulations are used to examine the control reconfiguration and the aircraft response for failure in the longitudinal axis (swashplate aft actuator and stabilator) and lateral axis (swashplate lateral actuator and ailerons) demonstrating the capability of the redistributed pseudoinverse method. For certain failures, especially for actuators locked in extreme positions, the post-failure response is considerably degraded (showing limit cycle oscillations, actuator saturation, or sluggish response), which was not evident from the handling qualities metrics evaluated from the extracted linear models.
A Turbulence Model for Flight Simulation and Handling Qualities Analysis based on a Synthetic Eddy Method
Authors:   University of Liverpool, Huecas Sergio ,   University of Glasgow, Barakos Prof. , White Prof.
Published: July 2023

A turbulence model based on a Synthetic Eddy Method has been adapted for flight simulation purposes and coupled to two FlightLab helicopter models. The model is based on the generation of a random distribution of turbulence generating Eddies within a control model surrounding the aircraft. Eddies are convected by the flow and regenerated at the inflow as they leave the simulation domain. Adjustment of Reynolds stresses and Eddy shape and sizes should allow adjustment of turbulence intensities and frequency spectra. Compared to other random turbulence models, preserving the location of the Eddies in the control volume ensures automatically that turbulence across different aircraft locations is automatically correlated. Offline and piloted flight simulation has been conducted to test the viability of the concept. Results show that the turbulence model generates upsets in all aircraft axis which result in higher workload requirements for the pilot.
Performance of Recent Large-angle Extensions to Classical Simulator Washout Algorithms
Authors:   Carleton University, Micomonaco Mikayla , Irani Rishad , John M. , Langlois Robert
Published: July 2023

Washout algorithms are typically used in flight simulator motion control software to give the pilots flying the simulator the impression that they are experiencing an unlimited range of motion when the Gough-Stewart hexapod providing the motion cues has a comparably very small motion envelope. Since hexapods have generally been adopted by the motion simulator industry and the washout algorithms developed in the 1970s have performed extremely well at giving pilots a very high fidelity training experience despite the very small angular workspace of the motion platforms, research in the area generally came to a halt in the 1980s. We have succeeded in development of the Atlas motion platform which possesses an unbounded orientation workspace that is singularity free, hence we have the need to revisit washout algorithm development to take advantage of the unlimited orientation workspace. In this paper, after a brief review of existing approaches, we outline the development of our unlimited angular washout. Several benchmark cases are presented for two aircraft having very different flight characteristics: a Cessna 172 and a Columbia 400. Additionally, a quantitative comparison of small, large, and unlimited angular washout algorithm performance is reported.
Preliminary Insights on Small eVTOL Design Trends from Surrogate Modeling for Operations Research
Authors:   US Army CCDC, Scott Robert , Battey Luke
Published: July 2023

A multidisciplinary approach combining conceptual vehicle sizing, surrogate performance modeling, and affordability analysis is presented as a solution to a system of systems operations problem. The approach is utilized in the design analysis of battery-powered quadcopter drones operating in a rapid package delivery system with time and system cost used as objective functions. To facilitate data flow between the design routine and external simulation tools, a software script is developed for rapid design and performance assessment of quadcopters in the size range between 3 and 9 pounds of gross weight. Beginning with a review of the surrogate modeling procedure, the implementation and operation of the software are demonstrated. The aircraft concepts generated in the routine are considered in a preliminary cost-benefit analysis within the system of systems context. The study concludes with observations on quadcopter capability and effectiveness advantages and limits, along with possible future expansion plans of the software tool to investigate these limits.
Leveraging Additive Manufacturing for Low-Volume, Out-of-Production Spare Parts
Authors:   Bell Textron Inc., Reilly Thomas
Published: July 2023

Additive Manufacturing (AM) and/or 3-D printing has been used for decades for fabrication of prototyping parts to validate design, geometries and kinematics. The ability to rapidly "grow" one-off and low-volume parts for evaluation and iterative design development is a perfect use of AM processes. As AM materials and machines advance, the repeatability, reproducibility and quality are maturing. Today, AM parts are moving into limited production applications with opportunity for future design features, competitive pricing, lower weight through design optimization, and potential for "on-demand" deliveries. The vast majority of AM parts remain limited to development and prototype phases of a program. As production ramps up, production part fabrications transition to more traditional processes. The higher quantities and schedule demand of production as well as conformity with certified materials and processes still favor traditional manufacturing methods. However, as production ends and the product moves fully into a sustainment phase, the demand for parts plummets (as shown in Figure 1) and subsequent fabrication schedules are dependent on forecasts that are often overwhelmed by "surprise" spares orders. In the latter part of the product life cycle, high rate, production-driven manufacturing processes may no longer be optimal and an alternative that permits a transition back to prototyping methods and one-off "on-demand" fabrication is needed.
Atmospheric Sampling in Urban Areas and Complex Terrain using UAS Swarms
Authors:   Barron Associates Inc., Cooper Jared ,   Air Force Research Laboratory Information Directorate, Andrekanic Alex ,   University of Virginia, Wekker Stephan , Neal David , Paulini Matthew
Published: July 2023

This paper reports on work performed under a program of research and development to design a team of unmanned aerial vehicles to efficiently and accurately sample atmospheric data in an urban environment or an area with complex terrain. The gathered wind field data are used to initialize weather models, thereby increasing the accuracy of these models. To achieve program objectives, the micro-Swarm Environmental Sensing (µSENS) technology was developed. µSENS enables a swarm, of small unmanned aerial systems (sUAS) to efficiently collect atmospheric data at high spatial and temporal resolution to assimilate with weather prediction tools. A swarm of intelligent sUAS equipped with wind and atmospheric sensors is deployed into an urban environment and collects atmospheric data at so-called information-rich locations. The data that are transmitted to the base station and used to initialize or update the weather prediction tools. µSENS includes compact sUAS vehicles designed specifically for atmospheric sampling, novel wind sensors, intelligent swarm control algorithms, and a ground control station to allow a single operator to manage the swarm and data collection process. This paper presents some of the main components of µSENS and lays a scientific foundation for sampling strategies for data collection in urban settings. Autonomous behaviors are described and the system is demonstrated through simulation and flight tests.
Vision-based Autonomous Guidance Approach for a Nano Unmanned Aerial Vehicle Rotorcraft Towards Indoor Flight Environment
Authors:   Beijing Intelligent Dynamics Rotorcraft Company, Wang Guanlin , Li Dehui , Xu Panpan , Luo Biuzhou , Wang Xiuli , Xu Beiju
Published: July 2023

Autonomous flight remains a major challenge for Nano Unmanned Air Vehicles (NUAVs). This research presented a light-weight vision-based navigation system which is suitable for NUAV rotorcrafts with restrictively limited payload capacity and computing resources. A visual-inertia compensation approach was proposed to obtain accurate indoor navigation and guidance for the homemade NUAV which weighting less than 50 g. The proposed visual guidance algorithm have been successfully recognized targets such as windows, gates, and narrow-corridor with 25 Hz guidance command output. Flight experiments shown that the NUAV rotorcraft can follow the path planning to achieve autonomous flight, and guide through gates and windows within GPS-denied indoor environment.
A Machine-Learning Approach for Time-Optimal Trajectory Generation for UAV's
Authors:   Rensselaer Polytechnic Institute, Lai Runyu , Zhao Di , Mishra Sandipan
Published: July 2023

This paper presents a data-driven approach towards time-optimal trajectory generation for Unmanned Aerial Vehicles (UAV's) using a machine-learned trajectory generation mechanism for point-to-point time-optimal trajectories on-the-fly. To train this machine-learned black box trajectory generator off-line, a model-based optimization problem is first constructed for point-to-point time-optimal trajectory generation, with physical constraints on inputs, states, and rates. The formulated optimization problem is then solved off-line for a range of initial and terminal flight states to generate point-to-point data-sets that consist of the optimal state and input trajectories. This information is compressed by parameterizing the input and state trajectories using a set of basis functions. This data is then used to train the neural network-based trajectory planner. The output of the neural network is the basis function coefficient sets for the state and input trajectories (and the total flight time) which can then be used to reconstruct the flight trajectory. Once the neural network is trained, the data-driven on-board trajectory generator is ready to be deployed on the UAV for on-board planning. This approach is demonstrated for two scenarios: (1) the input to the neural network being the initial and terminal flight states and (2) the input to the neural network being initial and terminal flight states as well as physical constraints. To validate the performance of the machine-learned black-box trajectory generator, the root mean squared error between the neural network generated trajectories and the trajectories obtained from solving the optimization problem directly is statistically evaluated. These trajectories are also tested for violation of path constraints (which are not included explicitly in the training or input to the black box planner) by evaluating the mean constraint violation for each path-constrained variable.
Coupled Pitch-Lag Hinge for High Inertia Electric Rotors
Authors:   CCDC Army Research Laboratory, Reddinger Jean-Paul
Published: July 2023

As rotor diameter and inertia increases, the quickness of the thrust response to pilot inputs slows, yielding negative implications to handling qualities and limitations on scaling electric propulsion. This study presents a novel approach to alleviating these scaling effects by introducing a pitch-lag coupled hinge to the root of 40" and 50" diameter props. The impacts of chordwise hinge placement and hinge angle are examined and compared to a baseline rigid rotor to provide physical understanding of the rotor dynamics. It is shown that a coupled hinge can be designed to maintain propeller efficiency for a design thrust, while increasing the sensitivity of thrust to rotor speed and the maximum thrust of an RPM-limited rotor. Finally, the dynamic implications of this are tested using a first-order motor model. When a 40" diameter trimmed rotor is set to max throttle, rotors with a coupled hinge angle achieve a 6% higher thrust in 9% less time. The dynamic response improvement scales favorably when the rotor diameter is increased. For the 50" diameter rotor, the introduction of pitch-lag coupling reduces the time constant of the rotor’s thrust response by 32%.
A Prediction Model of Transient Variable Speed Rotor Performance for Small UAS Propulsion Scalability
Authors:   Kent State University, Stringer D. ,   NASA Glenn Research Center, Valco Mark ,   Virginia Polytechnic and State University, Edmonds Kendy
Published: July 2023

This paper is an extension of the first, titled "Experimental Results of Transient Variable Speed Rotor Performance for Small UAS Propulsion Scalability." The material presented in that paper illustrated how rotor inertia is only one input variable that governs the transient response of electrical UAS rotor-motor configurations. To better understand how it and other parameters affect transient time, it is necessary to generate a model. The transient response can be readily modeled using a first principles analysis. However, due to the number of unknown parameters, other modeling methods are needed to develop a representative prediction model such as response surface modeling. This paper presents the second part of a Department of the Army funded research effort that experimentally measured the transient response of different sUAS rotor-motor configurations used for quadcopter applications, in order to predict the effect of scalability on the transient response. In the authors' assessment, this is one of the first papers in the literature, if not the first, dedicated to publishing a transient response prediction model. As mentioned in the first paper, we define the transient response as the settling time between two different "throttle," or electrical power settings.
Recent Developments of the Arrayed Controlled Turn-less Structures (ACTS) Motor
Authors:   Polarix Corporation, Zucker Oved ,   Bolder Electronics, Demolder Carl , Le Thanh
Published: July 2023

The paper discusses the application of the Array Controlled Turn-less Structures (ACTS) motor for VTOL application. The motor enhances the three main competing characteristics of electric motors; namely specific power, efficiency and reliability. The motor arrays an ensemble of elemental turn-less motors which include turn-less elements each with their dedicated inverters which are operated in synchronism. The resulting small pole size enhances the power density, the enhanced conductor packing enhances the efficiency, and the massive parallelism enhance the reliability.

Vertical takeoff requires much higher thrust compared to wing assisted takeoff. With limited on-board power, this higher thrust is presently provided by in ordinary larger propulsion disk area which reduces the craft aerodynamics, and the cruising Lift-to-Drag (L/D) ratio and accordingly the flight efficiency and range.

The high specific power of the ACTS motor allows for a different scenario and thus craft architecture. By substantially increasing the takeoff power which is now possible with the higher specific power of the ACTS motor, the propulsion disk area can be substantially reduced, with the resulting greater streamlined, high L/D craft, and thus longer range.

The paper discusses key aspect of the motor and inverter architecture and technology. Furthermore, it discusses its application to a high L/D VTOL and prospective performance.
Modeling and Design of a Wet Clutch Offset Compound Gear Transmission for Dual-Speed Rotorcraft Applications
Authors:   University of Tennessee, DeSmidt Hans ,   The Pennsylvania State University, Bill Robert , Su Xiaowen , Smith Edward
Published: July 2023

This paper develops a lumped-parameter multi-plates wet clutch Offset Compound Gear (OCG) transmission dynamics and its thermal model for dual-speed rotorcraft applications with an active clutch slip-speed control. This model includes the Reynolds equation for the clutch oil film thickness, the clutch thermal model, the clutch transferred torques (viscous and asperity torque) and the clutch disengagement model. The wet clutch/OCG transmission system is implemented in Matlab® Simulink™ to manage the upshift clutch temperature rise, which is a main issue need to handle for a dual-speed helicopter transmission. Here, the clutch temperature rise is treated by injecting a certain amount of coolant during engagement so that the temperature rise for the wet clutch is much lower than that of an dry clutch. In order to transfer a required torque using the available power, the sizing of the wet clutch could be evaluated via the developed wet clutch/OCG transmission model. This study shows that the temperature rise drops as the wet clutch oil flow rate increases adding extra weights compared with the dry clutch. The simulation also captures a phenomenon that a larger clutch engagement pressure might be required for the wet clutch to transfer the same torque since the wet clutch oil viscosity drops as the oil temperature increases during the clutch engagement.
Low-Order Prediction of Mineral Dust Sticking Probability in Turboshaft Engines
Authors:   University of Manchester, Ellis Matthew , Bojdo Nicholas , Filippone Antonio , Jones Merren , Pawley Alison
Published: July 2023

Rotorcraft operations in arid environments can result in the ingestion of large quantities of dust particles into turboshaft engines, where they can melt and deposit on high pressure turbine nozzle guide vanes. This can result in reduced engine life-span and in worst case scenarios, in-flight engine failure. Predicting the extent and rate at which this damage occurs has proven difficult owing to the wide range of variables relating to the dust cloud, engine and most importantly, the properties of the particulate encountered. Whilst significant work has been carried out to model the particle deposition process for both volcanic ash and coal fly-ash, there is scarce similar work for the different types of mineral dusts rotorcraft encounter. In this contribution, we assess the suitability of two opposing numerical approaches for use in a generalised, reduced-order deposition model of individual mineral particles depositing on a vane. Both models are seen to be heavily reliant upon empirical inputs, be this the thermo-mechanical properties of the particles such as their yield strength, or currently unknown experimentally determined constants. An alternative approach is therefore proposed whereby the particle yield strength is correlated using existing relationships to the Vickers hardness of the grain, a property more amenable to empirical determination. The results obtained represent the current applicability limits of the two models based upon existing empirical data and thus highlight the need for further experimentation relating to both the thermo-mechanical properties and probabilities of adhesion for both individual mineral grains and mineral dust blends.
Development of a Brushless DC Motor Sizing Algorithm for a Small UAS Design Framework
Authors:   Texas A&M University, Saemi Farid ,   Army Research Laboratory, Beals Nathan , Benedict Moble
Published: July 2023

This paper describes the development of a semi-empirical sizing algorithm for the outrunner brushless DC (BLDC) motors used in electric unmanned aerial systems (UAS) with a maximum gross takeoff weight of 25 kg (55 lb.). Given an operating torque and a desired geometric aspect ratio (stator diameter/length), the algorithm can predict the mass, geometry, and figure of merit (km) of a motor rated for the applied torque. Given an operating voltage and operating speed, the algorithm can predict the optimal torque constant (kt ), speed constant (kv), and winding resistance (R). To develop, tune, and validate the algorithm, complementary theoretical and experimental methods were used to overcome two key barriers: (1) motor performance theory was used to generate non-existent performance data, and (2) empirical trends in motor design were leveraged to connect independent theoretical torque, volume, and mass models. The resulting mass and figure of merit predictions are within ±20% of actual values for motors ranging in mass from 25 - 500 g (1-18 oz.) and varying geometries. Moreover, the derived electrical constants can be fed into equivalent circuit performance models to validate the output of the sizing algorithm and drive optimization feedback in a broader UAS conceptual design tool. The validated algorithm also revealed that motor size (and therefore mass) grows with torque, not power, which is a critical distinction for vehicle designers in the VTOL industry who are increasingly transitioning to electric powertrains.
Appropriate Calculation of Risk per Flight Hour for Rotorcraft Safety Risk Management
Authors:   Sikorsky a Lockheed Martin Company, Hewitt John , Loan Dr.
Published: July 2023

Quantitative Risk Assessment has become essential in rotorcraft safety risk management. Measures of risk include Cumulative Fleet Risk (also called Risk Factor), Risk per Flight, and Risk per Flight Hour. Each measure applies to a different situation and can produce the same or different predictions of future risk. Risk for a large fleet of aircraft might be accurately predicted by Cumulative Fleet Risk, whereas Risk per Flight or Risk per Flight Hour might be best for a small fleet of rotorcraft, a flight test program, or a fleet with low flight hours. Calculating risk per flight hour seems as simple as dividing the number of previous occurrences by the flight hours for the total fleet, but this is appropriate only in the case of random distribution. Most failures that lead to hazards are not random because the failure mechanism has a specific cause. A more appropriate method is to develop the future event forecast using Quantitative Risk Assessment, then divide that by the future fleet hours. The simple division process requires only two numbers and can be completed quickly, but with a possibly inappropriate or misleading result for anything but a random distribution. The approach presented here results in a risk prediction that is appropriate for hazard rates that are increasing, decreasing, or constant, and for non-random distributions, which could prevent misleading or unconservative risk management decisions.
A Twenty-five-year Retrospective Analysis of Australia's Previous Defence Aviation Safety Framework
Authors:   Australian Department of Defence, Hood James ,   RMIT University, Marzocca Pier , Sinha Arvind
Published: July 2023

Australia has embarked on an extraordinary reform to design, develop and implement a new and contemporary Defence Aviation Safety Framework. The program seeks to establish a single Defence Aviation Safety Authority (DASA) and issue a comprehensive and integrated suite of Defence Aviation Safety Regulation (DASR) for initial and continuing airworthiness, flight operations, air navigation, aerodromes (inclusive of ship-borne heliports) and safety management systems. While reforms of this scale can often be triggered by reviews into major aircraft accidents, such as The Nimrod Review by Charles Haddon-Cave QC in October 2009, Australia initiated the reform when new aircraft fleets were being introduced and at a time of arguably high-levels of aviation safety. The purpose of this paper is therefore to explain the compelling reason for change; providing a twenty-five-year retrospective analysis of Australia’s previous Defence aviation safety framework to give a rich picture of the difficulties faced by increased commercialization from the late 1990s, globalization in the 2000s, and the recent emergence of strict work, health and safety legislation in Australia.
Low AOB Component Loads Derivation to Implement MH-60R HUMS
Authors:   Technical Data Analysis Inc., Moon Suresh ,   NAVAIR, Liebschutz Daniel
Published: July 2023

Presently the fatigue lives of MH-60R dynamic components and airframe are based on a usage spectrum developed using pilot surveys. In order to better define the usage spectrum and to extend component and airframe fatigue life, the Health & Usage Spectrum (HUMS) System was installed on the U.S. Navy MH- 60R Rotorcraft. So far 207 aircraft are equipped with the HUMS systems and 121,334 flight hours of good data have been recorded. The regime recognition programs recognize 315 maneuvers, but are consolidated to 94 maneuvers of MH-60R usage spectrum, for which the component measured loads are available. To better define usage spectrum in detail and compute realistic component fatigue life, an additional maneuver of low Angle Of Bank (AOB) from 10 to 25 degrees was added, but the measured component loads were not available at this AOB to implement HUMS. Thus, measured flight loads data of level flight and AOB turns at 30, 45, and 60 degrees were utilized to derive component loads at 20 degrees by spline cubic interpolation technique. The cubic interpolation technique was applied to measured minimum, average, and maximum loads of variation at 10, 30, 45, and 60 degrees to interpolate load at 20 degree. This technique was applied to interpolate loads for pitch control rod, swash-plate, drag damper, shaft bending moments, blade cuff stresses, and flap deflections. The spline interpolation loads correlated with measured available loads of pitch control rod and blade stresses. The probabilistic fleet usage spectrum of various severities was developed using the HUMS recorded data of 121, 334 hours from 179 rotorcraft with and without low AOB usage. It is evident that fatigue life with 20 AOB split is significantly higher for all dynamic components. Thus, to implement HUMS successfully, it is necessary to compute loads that are not available in the original component fatigue life calculations. Further prorates of gross weigh (GW), velocity and altitude based on the HUMS fleet usage should be implemented to extend component fatigue lives.
Investigation of Fatigue and Flaw Tolerance Performance of 18CrNiMo7-6 Case-hardening Steel
Authors:   Turkish Aerospace, Öztürk Yahu , Akcihan Ufuk , Melemez Fazh
Published: July 2023

The aim of this study is to evaluate the effect of small defects on the fatigue life of the 18CrNiMo7-6 material. The evaluations are based on comparisons of S/N curves, which are obtained through coupon-level fatigue testing of pristine and intentionally flawed specimen sets. Fractographic examinations are performed on the failed specimens from both sets in order to investigate the fracture characteristics and discover any potential differences in failure mechanisms of two sets. Experimental findings regarding endurance limit of the flawed set are also compared with analytical evaluations. In these evaluations, the small defect effect is also considered on top of the linear fracture mechanics approach. Finally, the differences between the outcomes of fatigue life evaluations, when different methods are used, are discussed.
Is Architecture Measurable? Towards Creating, Managing, and Measuring Architecture and Resulting Product Line Implementations
Authors:   Skayl LLC, Hunt Gordon ,   US Army CCDC AvMC, Wigginton Scott ,   FirePoint, Jonas Paul ,   RWT Consulting, Townsen Ronald
Published: July 2023

This research sought to distill and define the fundamentals of system and software architecture analysis and form the basis by which a design can be tested and analyzed prior to its implementation. In short, the question "can a design be measured against the business-level objectives and quality-of-use architectural requirements. The research focuses on building a body of knowledge that supports an analysis, built on fundamentals which scales and can serve as the basis by which we can transform when and how architecture validation can occur. This research supports ongoing work towards developing a strategic comprehensive architecture approach and extends the analysis and documentation of the Key Business Drivers (KBDs) and architectural drivers supporting the efficient development and sustainment of interoperable aviation mission systems. A prototype process that leverages the discovered relationships and weights for use by current Architects and Senior Systems Engineers is shown. Programs implementing this approach are expected to benefit from the planned reuse of architectural artifacts for follow up systems engineering products supporting the development of reusable component product lines avoiding the long-term challenges of unrealized architectural objectives.
Digital Twin Approach for Structural Property Evaluation of Next Generation Active Twist Blades
Authors:   Konkuk University, Hwang Hyun ,   German Aerospace Center (DLR), Kalow Steffen , Ahn Jun , Chang Sehoon , Jung Sung , Keimer Ralf
Published: July 2023

The digital twin (DT) refers to a digital replica or virtual model of actual physical product or process that can be applicable for various purposes. In this study, a digital reproduction of the next generation active twist blade, meeting superior durability characteristics and high strength requirements under severe operating environments of a helicopter rotor, is attempted using the up-to-date computed tomography (CT) scheme combined with modern digital image processing technique. The CT scan covers much portion of the blade root, transition, and tip regions where substantial variations in external geometries and/or interior structural layouts are present while limited zones in the airfoil blade region being considered as nonuniform. A three-dimensional (3D) finite element-based DT simulation model is constructed using the high-resolution CT-scan images. The detailed lamination geometries and sequences of layered composites in the blade skin and spar are implemented in the DT model which can be exploited further for durability study or strength analysis. The reconstructed 3D analysis model is used to determine the structural properties of the blade. In parallel, either mechanical or optical measurement methods along with two-dimensional (2D) blade sectional analysis are carried out to cross validate their predictions. Overall, fair to good correlation is obtained between the different set of results. The agreement is good for mass, elastic axis, and flap bending while less satisfactory results are obtained with the torsion rigidity. A sensitivity analysis is also conducted to clarify the impact of modeling cables, nose weight, and manufacturing imperfections on the structural property evaluation of the blade.
Design of a Lean Avionics Rig for Efficient System Integration and Human Factors Testing
Authors:   Kopter Group AG, Goena Nicolas , Chiella Pasquale , Meo Giovanni
Published: July 2023

Small OEM often tend to use prototype aircraft in order to test avionics software and hardware integration. This approach is frequently justified by limited allocation of manpower and budget, with the consequence of exposing the program to the risk of increased costs and schedule impacts. Kopter has developed an avionics test rig with the objective of reducing the development risk on one side, and on the other side being compatible with the effort and budget constraints of a small OEM. The result is a rig where standard and commercial off the shelf components have been integrated together by Kopter in a lean way that grants flexibility and modularity, as necessary for an small OEM. The avionics test rig has demonstrated to be able to support testing of software for safety of flight clearance, design of the SH09 cockpit and familiarization of flight crew with the new G3000H avionics suite before first flight.
Wind Tunnel Testing a Small Isolated Folding Propeller
Authors:   US Army Technology Development Directorate, Battey Luke ,   NASA Ames Research Center, Russell Carl
Published: July 2023

Aircraft with small speed-controlled propellers are becoming increasingly popular. This is conspicuous in the commercial sector, but also evident in the defense sector. Proof of the latter is the Army's Air Launched Effects (ALE) program, which aims to develop foldable, tube-launched Unmanned Aerial Systems (UAS). Such aircraft will likely use small speed-controlled folding propellers, which have unique geometry and limited publicly available data making it difficult to characterize their performance. This paper concerns performance testing of a small speed-controlled folding propeller in the U.S Army's 7- by 10-foot Wind Tunnel at NASA Ames Research Center, utilizing a new test rig that aerodynamically isolates a propeller's blades. The results of the test are presented, which include thrust and efficiency measured at various pitch angles, rotational speeds and wind speeds. Useful and expected trends are identified in the data, such as the peak efficiencies increasing with increased RPM, wind speed and blade pitch.