Helicopter Type Research Articles

Fracture in control rods of helicopters: Same failures but different reasons

This paper presents two incidences of failures of collective control rods which resulted in accidents to a particular type of helicopter. The control rods were made of 2024 Al-alloy tubes fitted with fork at one end and a spherical bearing at the other end (eye-end). In terms of physical appearance, the two failures in the control rods were identical to each other wherein there was fracture in the Al-alloy tube at the eye-end. Fractography study confirmed that in both the cases, multiple fatigue cracks had initiated over a sector at the internal thread roots on the Al-alloy tubes corresponding to 1st/2nd thread on the eye-end stud. After initiation, the cracks had propagated progressively into the tube-wall and then along the circumferential direction. As the crack propagation progressed, the load bearing capacity of the tubes diminished resulting in final overload fracture under the operational load at the time of accidents. Although failures in both the control rods looked alike in terms of failure location, fracture pattern and fracture mechanism, the primary reasons of failures were found to be different. Investigation revealed that premature fatigue crack initiation was due to non-uniform stress distribution on the internal threads of the control tube with increased level of stress over a sector. In one case, the non-uniform stress distribution resulted from thread manufacturing deficiency, and in the other case, it was due to incorrect assembly at the eye-end.

On the modeling of urban air mobility vehicle takeoff and landing operations in the FAA Aviation Environmental Design Tool

Urban air mobility (UAM) vehicles are anticipated to operate in close proximity to the public. A possible barrier to the introduction of UAM vehicles as a transit solution is their community noise impact, particularly around vertiports. The Federal Aviation Administration Aviation Environmental Design Tool (AEDT) is the mandated tool to assess aircraft noise and other environmental impacts due to federal actions at civilian airports, vertiports, or in U.S. airspace for commercial flight operations. However, AEDT was designed to model fixed-wing aircraft and conventional helicopter operations, not UAM vehicles. Prior work by the authors showed significant differences in noise contours of UAM departures and approaches when modeling operations as fixed-wing and helicopter types in AEDT. This paper identifies the sources of those differences. Additionally, a NASA time-marching simulation tool is used to generate noise exposure data for equivalent operations to help identify differences associated with the integrated noise model implemented in AEDT and offer possible changes to assess UAM community noise impact more consistently with simulation-based modeling.

A Novel Approach to Detect Drones Using Deep Convolutional Neural Network Architecture.

Over the past decades, drones have become more attainable by the public due to their widespread availability at affordable prices. Nevertheless, this situation sparks serious concerns in both the cyber and physical security domains, as drones can be employed for malicious activities with public safety threats. However, detecting drones instantly and efficiently is a very difficult task due to their tiny size and swift flights. This paper presents a novel drone detection method using deep convolutional learning and deep transfer learning. The proposed algorithm employs a new feature extraction network, which is added to the modified YOU ONLY LOOK ONCE version2 (YOLOv2) network. The feature extraction model uses bypass connections to learn features from the training sets and solves the "vanishing gradient" problem caused by the increasing depth of the network. The structure of YOLOv2 is modified by replacing the rectified linear unit (relu) with a leaky-relu activation function and adding an extra convolutional layer with a stride of 2 to improve the small object detection accuracy. Using leaky-relu solves the "dying relu" problem. The additional convolution layer with a stride of 2 reduces the spatial dimensions of the feature maps and helps the network to focus on larger contextual information while still preserving the ability to detect small objects. The model is trained with a custom dataset that contains various types of drones, airplanes, birds, and helicopters under various weather conditions. The proposed model demonstrates a notable performance, achieving an accuracy of 77% on the test images with only 5 million learnable parameters in contrast to the Darknet53 + YOLOv3 model, which exhibits a 54% accuracy on the same test set despite employing 62 million learnable parameters.

Distributed active vibration control for helicopter based on diffusion collaboration

The active vibration control technology has been successfully applied to several helicopter types. However, with the increasing of control scale, traditional centralized control algorithms are experiencing significant increase of computational complexity and physical implementation challenging. To address this issue, a diffusion collaboration-based distributed Filtered-x Least Mean Square algorithm applied to active vibration control is proposed, drawing inspiration from the concept of data fusion in wireless sensor network. This algorithm distributes the computation load to each node, and constructs the active vibration control network topology of large-scale system by discarding the weak coupling secondary paths between nodes, achieving distributed active vibration control. In order to thoroughly validate the effectiveness and superiority of this algorithm, a helicopter fuselage model is designed as the research object. Firstly, the excellent vibration reduction performance of the proposed algorithm is confirmed through simulations. Subsequently, specialized node control units are developed, which utilize STM32 microcontroller as the processing unit. Further, a distributed control system is constructed based on multi-processor collaboration. Building on this foundation, a large-scale active vibration control experimental platform is established. Based on the platform, experiments are carried out, involving the 4-input 4-output system and the 8-input 8-output system. The experimental results demonstrate that under steady-state harmonic excitation, the proposed algorithm not only ensures control effectiveness but also reduces computational complexity by 50%, exhibiting faster convergence speed compared with traditional centralized algorithms. Under time-varying external excitation, the proposed algorithm demonstrates rapid tracking of vibration changes, with vibration amplitudes at all controlled points declining by over 94%, proving the strong robustness and adaptive capability of the algorithm.

Optimal control for quadrotors during inspection of power utility assets

Renewable energy and power utilities inspection by autonomous aircraft enables rapid and effective risk-free assessment of the state of systems, and provides a qualitative and accurate assessment of defects and damages. To realize maximum operational benefits of aerial inspections, effective controls for autonomous aircraft must be ensured and the system should be operated in an optimal policy. Hence, the objective of this paper is to consider optimal control strategies for a quadrotor helicopter type UAV. Based on some structural properties of the considered system, in particular the flatness property, we suggest a control strategy that ensures tracking a time parameterized path that connects two given points in the state space while minimizing the energy consumption. The proposed controller enables longer-endurance missions for the quadrotor and effective supervision and inspection of large energy systems and power plants. In this paper the analysis of the control law takes into consideration the highly nonlinear dynamic model of the quadrotor and the electrical actuator model. The current approach in solving the optimal control problem under consideration allows one to eliminate the differential equation and to reformulate the optimal control problem to a nonlinear dynamic programming problem. The approach can make monitoring operations of renewable energy plants by aerial vehicles, more efficient.

СONSTRUCTION OF AN OPTIMAL ROUTE FOR OVERFLYING UNPREPARED LANDING PADS

The problem of constructing an optimal route for overflying unprepared landing pads by the unmanned aerial vehicle (UAV) helicopter type in purpose to choose a useful unprepared landing to make an emergency landing is considered. The description of mathematical models that form the basis of the optimal algorithm of unprepared landing pads overflying is given. The decision to fly to an unprepared landing pad is based on the probabilistic criterion that considers the next following information: the probability of availability of an unprepared landing pad, the probability of failure of the UAV’s helicopter type onboard system, the error of a digital elevation map (DEM) positional information, the error of the UAV’s helicopter type coordinates information and the flight specifications of the UAV helicopter type.The comparison of the computational time of the algorithms of unprepared landing pads overflying is completed. The combined approach to find an optimal route for overflying unprepared landing pads depending on the computational time to solve it is proposed to use. The results of a simulation modelling of the proposed optimal algorithm for the estimation of its efficiency under conditions of variability of parameters of the probabilistic loss function are presented.

Comparison of kinetic changes during helicopter medical evacuations: civilian versus military flights

BackgroundHelicopter evacuation is crucial for providing medical care to casualties. Previous civilian studies have demonstrated that air transport can enhance survival rates compared with ground transport. However, there has been...

Robust Controller Design for a Generic Helicopter Model: An AI-Aided Application for Terrain Avoidance

This paper focuses on robust controller design for a generic helicopter model and terrain avoidance problem via artificial intelligence (AI). The helicopter model is presented as a hybrid system that covers hover and forward dynamics. By defining a set of easily accessible parameters, it can be used to simulate the motion of different helicopter types. A robust control structure based on reinforcement learning is proposed to ensure the system is robust against model parameter uncertainties. The developed generic model can be utilized in many helicopter applications that have been attempted to be solved with sampling-based algorithms or reinforcement learning approaches that take the dynamical constraints into consideration. This study also focuses on the helicopter terrain avoidance problem to illustrate how the model can be useful in these types of applications and provide an artificial intelligence-aided solution to terrain avoidance.

Ринок та перспективи газотурбінних двигунів для важких транспортних гелікоптерів

The subject of this study is the current state of the market and prospects for the development of heavy transport helicopters and their power plants. This article provides a classification of helicopters and a segment of medium-heavy and heavy helicopters with gas turbine engines. The field of application of such helicopters is briefly described. The purpose of this article is to evaluate the activities of Element JSC in the field of developing electronic control systems for gas turbine engines for heavy class helicopters. Such systems for Element JSC, in particular, are RDTs-2500 and RDTs-450M-117B units for TV3-117VMA-SBM-1B series turboshaft engines, created by Motor Sich JSC. Objective: To provide information on the main types of heavy helicopters manufactured and operated today, as well as a description of the gas turbine engines installed on these helicopters. The field of application of such helicopters is briefly described. The segment of heavy helicopters with gas turbine engines is the largest in terms of money on the world market of civil helicopters, and the forecast of deliveries of such helicopters for the next 5-7 years is given. Most helicopter models are not completely new developments, but have been improved over many years. Characteristic design features of heavy helicopters with gas turbine engines, features of the arrangement of units and equipment are given. The main structural and structural features of gas turbine engines of various manufacturers and the types of helicopters on which they are installed are given. Brief information on Russian and Ukrainian gas turbine engines - VK-2500 and TV3-117VMA-SBM-1B is provided separately. The results. Despite the active development of eVTOL technologies in the sector of small rotorcrafts, the development and improvement of gas turbine engines continues. Heavy helicopters of both traditional and non-traditional designs are being developed. Conclusions. Modernization of the design and "remotorization" of the Mi-8 helicopter is a good opportunity for "Motor-Sich Helicopters", but it needs its own developments. Many promising Ukrainian developments were canceled due to the war. Analysis of the technical characteristics of TVaD for heavy helicopters shows that domestic engines are almost in no way inferior to their European and American competitors. Promising TVaD of SE "Ivchenko-Progress" AI-130 with a capacity of 3,000 hp. can become an even more attractive proposition.

Mathematical modeling of movement of multi-rotor type aircraft

The problem of determining the features and setting the problem of mathematical modeling of multirotor aircraft (LA) is considered. Differences of their mathematical models from the classical mathematical models of aircraft and single-rotor helicopter type aircraft are considered. The analysis and substantiation of the forces and moments acting on a multirotor aircraft are carried out, taking into account the peculiarities of considering the corresponding coordinate systems necessary for studying the spatial motion of the aircraft. The problem of controlling the trajectory motion of an aircraft is formulated taking into account the rotation of its structure around the center of mass. Based on the consideration of the structural diagram of one of the most common four-rotor aircraft (quadcopter), a scheme for creating control forces and moments acting on the aircraft, under the influence of which the aircraft’s trajectory in space changes, is substantiated. The main mathematical dependences characterizing the kinematics of the motion of a multi-rotor aircraft are given. On the basis of the analysis carried out, a generalized block diagram of the control process for such an aircraft is substantiated and presented. To test the performance and adequacy of the mathematical model, a study was made of the movement of a quadrocopter in a vertical plane between given points in space in accordance with the law of forced control, which ensures the movement of an aircraft in space with maximum speed. The computer simulation of the obtained analytically mathematical dependences showed that this approach is applicable to the construction of mathematical models of the motion of multirotor type aircraft of various design layouts.

A dimensionality reduction approach in helicopter level flight performance testing

AbstractEvaluation of the power required in level flight is essential to any new or modified helicopter performance flight-testing effort. The conventional flight-test method is based on an overly simplification of the induced and profile power components required for a helicopter in level flight. This simplistic approach incorporates several drawbacks that not only make execution of flight sorties inefficient and time consuming, but also compromise the level of accuracy achieved. This paper proposes an alternative flight-test method for evaluating the level-flight performance of a conventional helicopter while addressing and rectifying all identified deficiencies of the conventional method. The proposed method, referred to as the corrected-variables screening using dimensionality reduction (CVSDR), uses an original list of 36 corrected variables derived from basic dimensional analysis principles. This list of 36 corrected variables is reduced using tools of dimensionality reduction to keep only the most effective level-flight predictors. The CVSDR method is demonstrated and tested in this paper using flight-test data from a MBB BO-105 helicopter. It is shown that the CVSDR method predicts the power required for level flight about 21% more accurately than the conventional method while reducing the required flight time by an estimate of at least 60%. Unlike the conventional method, the CVSDR is not bounded by the high-speed approximation associated with the induced power estimation, therefore it is also relevant to the low airspeed regime. This low-airspeed relevancy allows the CVSDR method to bridge between the level-flight regime and the hover. Although demonstrated in this paper for a specific type of helicopter, the CVSDR method is applicable for level-flight performance flight testing of any type of conventional helicopter.

The renewed helicopter fleet is the key factor in the social and economic development of the regions

Helicopters are the main transport in the North, Siberia, and Far East regions. The social and economic development of the regions is mostly defined by the condition and development of the helicopters’ fleet. Also, it is defined by the density and productiveness of the work of helicopter aviation companies with the customers. The ability of aviation companies to buy new types of helicopters on the one hand, and the ability of current and potential customers to order transportation services on the other hand, will define the scope and the speed of development of production and social domain of the regions.

К вопросу проектирования энергетической установки на основе водородных топливных элементов для малых беспилотных летательных аппаратов

Рассмотрены вопросы проектирования энергетической установки на основе водородных топливных элементов с протонообменной мембраной для беспилотного летательного аппарата вертолетного типа, киловаттного класса мощности. Представлены различные варианты конструкции энергоустановки, обоснован выбор оптимального варианта. Дано сравнение энергоэффективности силовой установки с различным числом двигателей, предложен способ выбора их оптимального количества. Приведена формула для выбора емкости литий-ионных аккумуляторов, работающих совместно с топливным элементом в режиме комплексирования. Решена задача оптимизации основных параметров стека топливных элементов – числа и площади ячеек. Методика может быть использована на начальном этапе проектирования для оценки характеристик и параметров системы электропитания энергетической установки на водородных топливных элементах.

Helicopter Rescue for Flood Disaster: Scheduling, Simulation, and Evaluation

Frequent severe floods have caused great losses to urban safety and the economy, which raises high requirements for the efficiency and effectiveness of emergency rescue. Due to the flood characteristics, flood rescue requires a more rapid responder and decision-making compared with other kinds of disaster rescue. In recent years, aviation emergency rescue (AER) has attracted much attention for flood applications. In order to evaluate the effectiveness of AER for flood disasters, the present study proposes a conceptual model of helicopter AER scheduling and develops a simulation system of helicopter AER scheduling using multiple agents. Seven elements are considered in the conceptual model: helicopters, the command-and-control center, temporary take-off/landing points, mission demand points, resettlement points, loading points, and unloading points. Furthermore, process-oriented and object-oriented scheduling rules are developed as the general guide for scheduling. In order to efficiently simulate and evaluate an AER mission (assisting the decision maker), the simulation system is designed with multiple agents and a user interface, which can quickly load mission settings, run the simulation, and collect data for further evaluation. A standardized mission makespan is adopted as the evaluation index. Based on that, the minimum integrated index can be derived to finally assess the different rescue schemes and choose the best. In the case study, the comparison results indicate that the rescue efficiency of large helicopters (Mi-26 in the case) could be limited by the capabilities of loading points and unloading points. This problem is solved by scheduling small/medium-size helicopters to transfer the personnel. Alternately, two types of helicopters can be used: one for passenger transfer and the other for goods/material transfer. Anyway, the analyses in the case study illustrate the correlation between effectiveness and scheduling, which demonstrates the significance of decision-making. By using the proposed scheduling and modeling methods, the simulation system can be served as a convenient decision-making support tool for practical rescue applications.

The effect of the new rescue helicopters on the rescue service's mission profile.

The change of rescue helicopter type from the Sea King to the SAR Queen has been controversial. Some hospitals can no longer receive rescue helicopters because of the stronger rotor downwash from the SAR Queen. For the same reason, it has been unclear whether the SAR Queen would be able to land near patients for air ambulance missions. The objective of the study was to investigate whether the change of helicopter type has changed the rescue service's mission profile. Mission data from the first eight months with the SAR Queen at Ørland Air Base (14May 2021-14January 2022) were compared with the last equivalent period with the Sea King (14May 2020-14January 2021). The number of requests increased from 249 to 349 (40%) after the introduction of the new rescue helicopter. Response time increased from 11 to 13 minutes (18%), while the on-scene time remained unchanged at 10 minutes for primary missions and search and rescue missions. The patients' average degree of severity, assessed by NACA scores, remained unchanged at 3.7. The proportion of missions where hoisting of a rescue paramedic or a doctor was required to gain access to the patient remained unchanged. The study showed that the use of the rescue helicopter at Ørland Air Base increased after the phasing-in of the SAR Queen. The service's mission profile remained the same. The unchanged proportion of missions that involved hoisting indicates that suitable landing sites close to the patients were found to the same extent as with the Sea King.

TECHNICAL ASPECTS OF AVIATION FIREFIGHTING IN ECOSYSTEMS: THE EXPERIENCE OF FOREIGN COUNTRIES

The article examines the technical aspects of aviation firefighting in ecosystems based on the experience of leading countries around the world. The features of natural and man-made ecosystems in the plane of fire suppression are disclosed. It is specified conditionality of occurrence of requirement in aviation firefighting, first of all, by existing features of ecosystems, and also available level of technical development and possibilities of manned aviation on operative performance of tasks of firefighting in ecosystems. The state of fire aviation of the USA and Canada, European countries, China and other countries, as well as infrastructural peculiarities in organization of fire extinguishing from the air were investigated. According to the results of the study it is noted that the fleet of fire-fighting aviation or aviation involved in fire suppression consists of different types of aircrafts and helicopters, which are used depending on the ecosystem for rapid elimination of the fire occurred in the ecosystem. Attention is focused on the prospects of creating aviation firefighting means based on unmanned aviation, which develops in an avalanche-like manner and allows to optimize firefighting in different ecosystems. Attention is drawn to the direction of development, though not quite new, but useful, the essence of which is the use of aviation firefighting means in the form of special bombs on the example of Russia, China and Israel. The state of fire-fighting aviation fleet of Ukraine was analyzed. Proposals of technical and organizational character of the further development of fire extinguishing from air in Ukraine are investigated. The analysis of the given proposals showed that the direction connected with the development of unmanned aerial firefighting aircraft in natural and artificial ecosystems of Ukraine still remains at the level of ideas, though it requires further promotion in our country, which has a number of aviation enterprises, capable of successfully solving the following problems under the conditions of the necessary financing. The conclusions focus on the fact that the considered directions of development of fire aviation in Ukraine are mostly at the level of ideas, which should be, first of all, scientifically grounded. The directions of further research should be considered the development of the newest and scientifically justified technical solutions with their subsequent implementation in the infrastructure of aviation firefighting in Ukraine

Development of the technical solution to prevent a single-rotor helicopter from entering uncontrolled rotation

The phenomenon of a single-rotor helicopter entering an unintended left rotation with the further development of an uncontrolled turn periodically arises while operating this type of helicopter, both in Russia and abroad. This phenomenon can lead to serious aviation incidents and even disasters. Currently, there is no unambiguous justification for the phenomenon of "uncontrolled" U-turn and the causes of occurrence, since the operating conditions of the tail rotor (TR), especially at low-speed modes, depend on many factors. These factors include, firstly, wind direction and speed, T/R “vortex ring", as well as the impact of the main rotor vortex trace. One of the explanations for this phenomenon lies in the special specifics of the yaw trim of a singlerotor helicopter, which is provided by the tail rotor. These papers emphasize that the change in wind speed and direction which affects the helicopter, and the TR is the main cause of the unintentional left turn. Currently, there are no tools and methods for determining the wind effect on the TR in order to develop a warning signal for a pilot about a change in the nature of the TR flow and an alert about the occurrence of uncontrolled rotation. This paper proposes the system for measuring the TR air flow using a special sensor that allows us to measure the inductive air flow velocity of a small value in an aerodynamic way without additional various electronic transformations that are inherent in conventional Pitot tube probes. The use of such a measurement system makes it possible to identify the probability of a dangerous situation, to inform the pilot and help him take the proper actions.

Invited Paper: Rotorcraft Design: The Crucial Influence of Safety from Concept to Fleet Support The 41st Alexander A. Nikolsky Honorary Lecture

It is an immense honor to have been selected to hold the prestigious 41st Nikolsky Lecture and to have the opportunity to synthesize my experiences with regards to the most important principle that permeates aeronautical engineering—"the concept of safety." Having worked in the rotary-wing field for 39 years, with growing levels of involvement and responsibilities, I have been involved in the design, development, and certification of many helicopter models at the Leonardo Helicopters Division (LHD; formerly Agusta and then AgustaWestland), such as A109, A119, EH101, A129, NH90, AW609. More recently, I had the full responsibility of design, development, certification, and entry into service of three new helicopter types within the "AW Family concept", specifically the AW139, AW189, and AW169. I am profoundly grateful for the mentors encountered in my professional life—Bruno Lovera and Santino Pancotti, both of whom were also honored with the Nikolsky Lectureship. In working with them, not a single day passed where the word "safety" was not mentioned. They taught me that "safety" shall be the mantra of every aeronautical engineer because it is our principal duty and responsibility, towards those who travel in, work on, and work with our products and entrust their lives to our work and professionalism daily. I have tried hard never to forget this lesson, and to convey this to the young engineers that I have had the chance and pleasure to work with. If I have been able to pass on this lesson successfully, through my work with others through this lectureship, it would be the greatest achievement of my life. In this vein, this paper is organized in three parts: (i) definitions and principles, along with some "philosophical" concepts; (ii) the application of these principles at Leonardo in the design of the latest generation of helicopters, and finally (iii) a discussion of emerging "safety technologies" that promise to improve the safety of future helicopters and operations.

Optimization of types and quantity of the national helicopter park as a factor of customer’s cost reduction

The article shows that the main cause, which restrains wide implementation of helicopters, is the incongruity of the current park of helicopters to the character and the high cost of the performing tasks. The solvation of the problem would be a saturation of the helicopter park by the new types of helicopters. The method of calculation of the possible reduction of exploitation expenses under optimization of helicopter types in accordance with market demand is offered. The optimization of types and quantity of helicopters park enables the customers to reduce their costs and widen the possibilities of helicopters exploitation in national economy.

ПОРІВНЯЛЬНИЙ АНАЛІЗ ТА СТВОРЕННЯ БЕЗПІЛОТНИХ ЛІТАЛЬНИХ АПАРАТІВ ДЛЯ ФОРМУВАННЯ МАКЕТА РОЙОВОЇ ВЗАЄМОДІЇ

The subject of study is the process of creating an unmanned aerial vehicle of the helicopter type, which is able to perform autonomous flight and be used in the premises to test the algorithms of swarm interaction. The aim is to reduce the cost of forming and operating the UAV swarm intelligence model, ensuring compatibility with existing hardware positioning systems and simulation software platforms. Tasks: to analyze the existing prototypes of unmanned aerial vehicles of the helicopter type, used for modeling and testing of autonomous flight modes indoors; to review the systems of positioning and exchange of information between the participants of the swarm formation and to analyze the hardware systems necessary for the implementation of these systems; to develop the architecture of hardware subsystems for unmanned aerial vehicles capable of performing tasks at the level of the considered prototypes; design a case for a sound hardware platform, check its operational parameters, implement its collection and testing; install software that allows you to check the operability of the considered platform of the unmanned aerial vehicle. The methods used are: systems analysis used to compare models of unmanned aerial vehicles within the tasks, methods of analysis and synthesis of schemes for the implementation of the hardware platform, the method of graphic modeling for the design of the unmanned aerial vehicle, methods of system programming for flight program. The following results were obtained. The choice of the hardware platform of the unmanned aerial vehicle is substantiated; the hull for the helicopter was developed and implemented, two platforms of unmanned aerial vehicles were collected and tested during autonomous flight indoors. Conclusions. The study found that there are existing and widely used platforms for compatible indoor flight. These platforms are open and closed. The analysis of open hardware platforms and synthesis of architecture of own unmanned aerial vehicle is made. The designed and implemented unmanned aerial vehicle is capable of autonomous flight, has all the necessary components to perform a compatible flight program. As part of the layout of swarm interaction, it is necessary to further adjust the positioning system.