Helicopter Flight Research Articles

Evaluation of nighttime helicopter noise in an urban neighborhood

Sound level measurements were gathered at two locations within an urban neighborhood close to a helipad. A sound level meter was placed at each location for approximately one week, where data were collected continuously from 10:00 PM to 6:00 AM in fifteen-minute intervals. L90 was measured to establish existing background levels and LAFmax was measured to capture the helicopter noise. Additionally, a sound level trigger was set up to capture details and audio recordings of elevated levels associated with helicopter flights. Due to the lengthy data collection period, care was taken to collect as much data as needed without exceeding the storage capacity of the meter. Based on preliminary data, the trigger was set to capture only events with a minimum sound pressure level and a minimum time duration, ensuring shorter noise events not of interest (barking dogs, passing cars, etc.) were not captured. Audio files for each sound event were used to identify helicopter events, which were confirmed by comparing timestamps with the helicopter flight logs. This case study describes the details of unattended long-term data collection for this application and evaluation of the helicopter noise measurements.

Human-automation interaction for helicopter flight: Comparing two decision-support systems for navigation tasks

This paper investigates the effects of different automation design philosophies for a helicopter navigation task. A baseline navigation display is compared with two more advanced systems: an advisory display, which provides a discrete trajectory suggestion; and a constraint-based display, which provides information about the set of possible trajectory solutions. The results of a human-in-the-loop experiment with eight pilot participants show a significant negative impact of the advisory display on pilot trajectory decision-making: out of the 16 encountered off-nominal situations across the experiment, only 6 were solved optimally. The baseline and constraint-based display both lead to better decisions, with 14 out of 16 being optimal. However, pilots still preferred the advisory display, in particular in off-nominal situations. These results highlight that even when a support system is preferred by pilots, it can have strong inadvertent negative effects on their decision-making.

Helicopter flight dynamics with simulated rainfall

Sustaining flight operation that encounters with rainfall might be a challenge to a pilot due to lacking of understanding flight dynamics in the rain conditions. This paper, combined with a computational fluid dynamics (CFD) technique, develops a nonlinear flight dynamics model in the rain conditions that can be capable of exploring UH-60A single-rotor helicopter flight dynamics in the rain conditions, including trim, stability, and controllability. Firstly, in order to obtain a data-driven basis relating to multiple working conditions of the blades, a CFD-based method of simulation of the blade airfoil in the conditions of the angles of attack ranging from −26° to 26° and under a thunderstorm heavy rain scenario when the rate of rainfall is 1500 mm/h is developed. Then, these data are incorporated into a nonlinear flight dynamics model in the form of coefficient increments. Numerical simulations are conducted in the range of the flight velocities from 0 knots to 160 knots. The quantitative results indicate that rainfall degrades the blade airfoil aerodynamic performance and increases the rotor torque and required power, affecting the helicopter trim, stability, and controllability. More importantly, helicopter that flies in a small or moderate flight velocity and that encounters rainfall might be a relative serious case, which should be paid attention to.

Simultaneous swept anhedral helicopter blade tip shape and control-system design

PurposeThis paper aims to offer a simultaneous design approach for helicopter having swept anhedral blade tip shape and helicopter flight control system (HFCS) to minimize controller cost.Design/methodology/approachBy considering previously stated offer, control-oriented models and a stochastic optimization method are applied to minimize controller cost of the HFCS.FindingsUsing simultaneous design approach for helicopters having blade tip swept and blade tip anhedral causes considerably less control effort than the helicopters not benefiting this related design approach.Practical implicationsSimultaneous design approach for helicopters having blade tip swept and blade tip anhedral is applicable to consider fuel economy.Originality/valueOne important novelty of this paper is using simultaneous approach for determining optimum shape of blade tip swept and anhedral. Another considerable novelty of this paper is also using a stochastic optimization method called simultaneous perturbation stochastic approximation for previously mentioned purpose. In this paper, it is also reached that using simultaneous design approach for swept anhedral helicopter blade tip shape and HFCS causes less control effort than the helicopters not using this approach. This leads to less fuel consumption and green environment.

Trajectory Tracking Based on Active Disturbance Rejection Control for Compound Unmanned Aircraft

The compound unmanned aircraft is provided with three primary flight modes, which are helicopter flight mode in low forward speed flight, airplane flight mode in high forward speed flight and transition flight mode in middle forward speed flight. For the different flight modes, an appropriate flight control law is the need to ensure good flying qualities. In this paper, a trajectory tracking control system based on the active disturbance rejection controller (ADRC) for the compound unmanned aircraft is proposed to adapt the full flight modes. A flight dynamics model and a Simulink simulation model of the compound unmanned aircraft are developed. The transition flight control strategy is analyzed and synthesized to meet the requirement of control strategy in the full flight modes. The internal uncertainties and external disturbance of the UAV are estimated with an extended state observer to compensate control input. A genetic algorithm-particle swarm optimization (GA-PSO) algorithm is utilized to optimize the controller parameters. The simulation of route tracking and spiral climb with different flight modes is conducted, which demonstrates the tracking ability, interference rejection, robustness and effectiveness of the developed controller in the full flight modes.

Improved Instrument Approach Stability Analysis for Helicopters Using Data Fusion and Analytics

Approach and landing are among the most challenging and dangerous tasks required of helicopter pilots. Helicopter accident statistics suggest that the majority of helicopter accidents occur during the approach and landing phases of flight. Unstabilized approaches are a leading cause of these accidents due to the increased potential for loss of control, loss of situational awareness, or controlled flight into terrain. In the present work, routine flight data records obtained as part of a voluntary helicopter flight data monitoring program are used to identify, analyze, and evaluate the stability of instrument approach events. A data fusion process is developed that enables detection of the approach phase, identification of an associated instrument approach procedure, analysis of approach stability, and knowledge discovery through data mining. The process identified 385 instrument approach events in a set of 7063 operational helicopter flight data records. Manual analysis of these events reveals some common errors, including crossing the final approach fix far below the assigned altitude and violating the minimum altitude requirement during initial and intermediate approach legs and course reversal maneuvers. Data mining algorithms are tested and found to be capable of automatically identifying atypical or unstable approach events.

An excellent harmonic feedforward-sliding mode output feedback hybrid algorithm for helicopter active vibration control

Higher harmonic control algorithms in frequency domain are generally used for active vibration control of helicopter fuselage. However, these algorithms are inefficient to control transient vibration caused by rapid changing of helicopter flight conditions. Time domain feedback algorithms are efficient to control the transient vibration. In this paper, an excellent harmonic feedforward-sliding mode output feedback hybrid algorithm by combining frequency and time domain algorithms is presented to improve the effect and performance of active vibration control of helicopter fuselage, meanwhile to avoid the requirement of full state information of control system due to using the time domain algorithms. The convergence criterions of the harmonic feedforward algorithm and the hybrid algorithm are theoretically derived, respectively. The convergence speed of the hybrid algorithm is theoretically proved to be faster than that of the harmonic feedforward algorithm. Active vibration control simulation and experiment on a dynamically similar and geometrically scaled frame structure of a helicopter fuselage verify the proposed hybrid algorithm with excellent control effect and performance.

Contribution of general aviation to ensuring transport accessibility to the Arctic regions: the challenges and areas of focus

The article defines the dominant position of general aviation to ensure passenger transportation, to render the sanitary aviation and the Ministry of Emergencies services, taking into consideration the natural and climatic conditions of the Russian Federation Eastern Arctic. It analyzes the current state of the transport system of this territory, which is characterized by the railway communication lack, available roads for only seasonal purpose – winter roads, and the key role of water transport in the organization of freight transport based on the complex long-term (more than one year) multimodal delivery schemes, extremely high cost of regional and local air transportation. The purpose of the study is to analyze the state of the general aviation system in the Eastern Arctic of Russia and identify the factors, constraining its development, and to formulate proposals for their elimination. The article examines the state of the operating airport network, route network and operators’ fleet of aircraft – in service which render services to these territories. The limited airport network does not provide aviation accessibility to each settlement of the Arctic zone and causes transport discrimination. The lack of scheduled flights in local communication leads to increased waiting time for transportation and reduces demand. The outdated general aviation fleet with low economic efficiency is outcompeted by the helicopter service. The cost of a helicopter flight hour in the Arctic is 500–650 thousand rubles. The article considers the legal restrictions, that are associated with overstated requirements for companies and aviation enterprises serving the general aviation activities and hinder the development of local air transportation in the Arctic zone. Based on the analysis of foreign experience, the areas of focus to improve the Russian legislation, regulating the general aviation activities, which will allow us to reduce the costs to maintain the airport network, thereby stimulating its expansion for the purpose of increasing the level of transport accessibility to remote settlements of the Arctic zone, are proposed. The proposed measures to improve the air transport system in the Arctic zone are aimed to achieve the formulated targets.

Development of visual helicopter emergency rescue system

Abstract Helicopter rescue is an important part of emergency rescue syste m, an d is oft en ca r r ie d out under complex terrain and low-visibility meteorological conditions. In order to ensure the safety of helicopter flight and the timely and efficient implementation of emergency rescue, it is necessary to establish a visual emergency rescue system. This paper selects Chongqing as the reference city, and it is preliminarily planned to take “GeoSim” as the 3D simulation platform, combined with the secondary development technology of geographic information system (GIS). According to the current flight performance of helicopters, and through the analysis of obstacle crossing, the intelligent algorithm can realize the visual simulation demonstration of single helicopter rescue system and multi-helicopter rescue system along the optimized path and user-defined path, and give the quality evaluation of emergency rescue drills, as well as the suggestions of the best emergency rescue plan.

ASSESSMENT OF THE IMPACT OF THE FUNCTIONAL SYSTEMS OF Mi-8MSB-V AND Mi-8MT(MTV) HELICOPTERS ON THEIR SAFETY INDICATORS IN 2017-2021

The paper proposes an integrated approach to determining long-term trends in quantitative indicators of reliability of Mi-8MSB-V and Mi-8MT(MTV) helicopter systems by specialty and their impact on the operational reliability of helicopters.
 An integrated approach consists in determining the impact of the reliability of helicopter systems on the operational performance of helicopters: the mean time between failures, the average failure rate parameter, the probability of helicopter flight reliability per hour, and the maximum allowable indicative levels of helicopter reliability indicators.
 The reliability of functional systems for helicopter specialties was determined: helicopter and engine, aviation armament, aviation equipment, radio-electronic equipment based on statistical data on helicopter malfunctions for the period between 2017 and 2021.
 Proposals have been developed to determine the maximum allowable indicative levels of helicopter reliability indicators based on information about the technical condition during military operation, which will allow adjusting the terms of maintenance, repair, life extension and provide for areas for the modernization of aviation equipment.
 For an in-depth analysis of the causes of malfunctions and the development of recommendations for their elimination, it is necessary to supplement the information provided in the fault record sheets with information on the number of aircraft, the flight time of which takes into account the developed recommendations for improving the system for collecting operational information on the reliability of the aircraft and its reflection in the fault record sheets.
 In order to objectively take into account, the impact of aviation armament on the reliability of helicopter engines, it is necessary to provide information on the helicopters flight time using the functional systems of aviation armament.
 Recommendations are given to improve the reliability of the least reliable elements of helicopter systems.

Flight performance of helicopter tail rotors with extendable chord

To investigate the potential of Statically and Dynamically Extendable Chord (SEC/DEC) in performance improvement of helicopter tail rotors, a prediction model of helicopter flight performance is developed and validated. It is suitable to deploy the SEC and DEC close to the blade tip for power reduction of tail rotor in hover and high-speed flight. The deployment locations of SEC and DEC for tail rotors are similar to that of main rotors. In hover, the deployment of the SEC and DEC results in little power reduction. From low to medium speed flight, the deployment of the DEC and SEC increases the power. In high-speed flight, the SEC and DEC can significantly decrease the power, especially at a large take-off weight. At 300 km/h, when the chord extension is 20% of blade chord, the SEC and DEC with 1/rev input decrease the power by 14.44% and 20.47% at a take-off weight coefficient of 0.0091. The DEC shows greater potential in power reduction than the SEC. There is an optimal phase input for the maximum power reduction, which does not vary with forward speed. For the DEC with 1/rev input, the optimal phase is [Formula: see text]. The optimal phase input for the maximum power reduction of tail rotors is different from that of main rotors.

Conversion Flight Control for Tiltrotor Aircraft via Active Disturbance Rejection Control

The tiltrotor aircraft consists of three primary flight modes, which are helicopter flight mode in low forward speed flight, airplane flight mode in high forward speed flight and conversion flight mode. This paper presents an active disturbance rejection controller for tiltrotor aircraft conversion flight. First, a tiltrotor aircraft flight dynamics model is developed and verified. Then, conversion flight control laws, designed via the active disturbance rejection control (ADRC) and sliding mode control (SMC) techniques, are proposed for the tiltrotor aircraft with model uncertainties and external disturbance, which are estimated with an extended state observer. Finally, the simulation of automatic conversion flight is carried out, which shows the effectiveness of the developed controller.

Unmanned helicopter flight control actuator specification through mission profile analysis

Helicopter dronization is expanding, as for example with the VSR700 project, and leads to the design and the integration of electromechanical actuators (EMA) into the primary flight control system (PFCS). The PFCS is in charge of controlling the helicopter flight over its 4 axis (roll, pitch, yaw, vertical). It controls the blade pitch through dedicated mechanical kinematics and actuators. The hydraulic technology has been conventionally used in actuators for more than 60 years. On the other hand, the introduction of the EMA technology requires the reconsideration of design practices right at development start. Indeed, the establishment and synthesis of the specification need to deal with – new design drivers (high performance points, wear, fatigue) and - new inherent technological imperfections (friction, inertia and reduction ratio). To address these topics, this paper draws a list of the main EMA design drivers to focus on along with a brief description of the main EMA components. Then, it proposes indicators evaluated over a complete mission profile in time coming from measurement on a given applicative helicopter flight. These indicators are chosen and elaborated to provide an image of the design drivers responsible for rapid and gradual degradations of the actuator components. Also, they give an idea of the importance taken by the actuator imperfections into the global performance. Furthermore, we explain how mission profiles are processed depending of data sources. Finally, through a comparison with a standard aircraft mission profile, we emphasize the specificity of the helicopter application use case.

CASE ANALYSIS ON FLIGHT CONTROL SYSTEM SIKORSKY S76 C++ FAILURE FROM YAW CONTROL ASPECT

Flight Control is a system that functions as a helicopter control center. Failure that occurs in flight control would certainly result inconvenience of the pilot in operating the helicopter, even the movement of the helicopter can out of control causing incident or accident. The continuity of the helicopter operation is affected by the maintenance system applied. One of mode moving system helicopter is yaw control, that could control the nose helicopter to move right and left. Fault Tree Diagram could described analytical technique, whereby an undesired state of the system is specified (usually a state that is critical from a safety or reliability standpoint). The system then analyzed in the context of its environment and operation to find the solution. Based on the analysis results of failures that occurred in the Sikorsky S76 C ++ helicopter flight control from yaw control aspect in the period of January 2015 to May 2018 with an average use of helicopter’s 2092.05 flight hours, there were 46 failures which caused by yaw control. Based on diagram, there were 4 basic events which caused unschedule maintenance on Sikorsky S76 C ++ helicopter flight control system because of yaw fail control, so that a replacement or repair was needed for the components that affected to the system failure.

Chewing gum reduces visually induced motion sickness

Visually induced motion sickness (VIMS) is a common side-effect of exposure to virtual reality (VR). Its unpleasant symptoms may limit the acceptance of VR technologies for training or clinical purposes. Mechanical stimulation of the mastoid and diverting attention to pleasant stimuli-like odors or music have been found to ameliorate VIMS. Chewing gum combines both in an easy-to-administer fashion and should thus be an effective countermeasure against VIMS. Our study investigated whether gustatory-motor stimulation by chewing gum leads to a reduction of VIMS symptoms. 77 subjects were assigned to three experimental groups (control, peppermint gum, and ginger gum) and completed a 15-min virtual helicopter flight, using a VR head-mounted display. Before and after VR exposure, we assessed VIMS with the Simulator Sickness Questionnaire (SSQ), and during the virtual flight once every minute with the Fast Motion Sickness Scale (FMS). Chewing gum (peppermint gum: M = 2.44, SD = 2.67; ginger gum: M = 2.57, SD = 3.30) reduced the peak FMS scores by 2.05 (SE = 0.76) points as compared with the control group (M = 4.56, SD = 3.52), p < 0.01, d = 0.65. Additionally, taste ratings correlated slightly negatively with both the SSQ and the peak FMS scores, suggesting that pleasant taste of the chewing gum is associated with less VIMS. Thus, chewing gum may be useful as an affordable, accepted, and easy-to-access way to mitigate VIMS in numerous applications like education or training. Possible mechanisms behind the effect are discussed.

Prediction and Assessment of Exposure to Electromagnetic Field During a Helicopter Flight

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

The Demonstrator of Structural Health Monitoring System of Helicopter Composite Blades

The health and usage monitoring systems are widely used for the monitoring of vibrations of power plant units on helicopters. At the same time critical helicopter structures like main and tail rotors or tail boom are still out of permanent monitoring. Practically all non-destructive techniques (NDT), like ultrasound, eddy current, X-ray and others make the inspection of structural components available on the ground only, during the maintenance check or overhaul. The article considers the promising technique for structural health monitoring (SHM) of a helicopter in flight, inter alia, of rotating blades. Actively developing methods of modal analysis, especially “operational” one, open the new opportunity for structural monitoring and its attendant issues. The Operational Modal Analysis (OMA) techniques and the methods of its data application are the basis of the novel concept of “modal passport” for monitoring of helicopter’s blades. There is brief description of basic principles of the modal passport and its trial application. The paper discusses the problems associated with practical application of modal passport to rotating helicopter blades and ways to overcome it. The light coaxial helicopter Ka-26 became the operating platform for experimental study of OMA application and works as the demonstrator of advance SHM techniques. Brief description of measurement system, including equipment and transducers on the blades is presented. The discussed research stage aims to demonstrate the potential of OMA techniques for monitoring of rotating blades, applying the seeded faults to estimate sensitivity of the SHM system. The paper discusses analytical and experimental study of the blade, including FE modelling and comparative analysis with the experimental data. The conclusions of the paper summarize the results of the research stage, outline the novelties and its practical application. The tasks of further works for SHM research stages using the demonstrator are formulated.

An Approach to Developing Mathematical Software of On-Board Helicopter Flight Simulator Decision Support System

Abstract The work explores methods and develops aids to improve a pilot flight training level using Full Flight Simulators. It examines their didactic advantages over real helicopters by implementing on-board intelligent decision support systems (IDSS). These simulation programs monitor actions of learner, find the best ways to correct errors and generate appropriate instructions. The training is carried out by reference point methods while the helicopter flight dynamics model simulates a flight and helps an instructor in parallel. Sufficiently simple and accurate model of helicopter flight dynamics was selected and tested to assess the proposed methods and aids. Our analysis introduces a functional structure of IDSS as an adaptive control system with a reference model. We further conducted a study on developing models, methods and means of automatic analysis, forecasting, optimization and correction of actions. Combining single-criteria conditional and vector optimization methods, we found out optimal flight parameters. The research findings revealed that the chosen optimization method requires too many system resources for the optimal solution to be found in a short time. The study thereby comes up with applying ANNs to solve this problem.

INVESTIGATION OF THE INFLUENCE OF THE INSTALLATION OF THE EXHAUST DEVICE ON THE FLIGHT AND TECHNICAL CHARACTERISTICS OF THE HELICOPTER МИ-24

The article considers the results of installation of exhaust devices on the helicopter. According to the test results, the installation of screen and exhaust devices on the helicopter reduces its thermal visibility, but at the time affects the change in its flight and technical characteristics. Thus, conducting the test of the helicopter Ми-24 with the installed “Adros” screen and exhaust devices АШ-01В the characteristics of the load capacity, height gain of the practical ceiling, maximum flight speeds, stability and handling of the helicopter are investigated.&#x0D; When performing flight tests, most of them are occupied by flight studies for the study of flight and technical characteristics (LTC) of helicopters. Since the installation of screen and exhaust devices on the helicopter affects the change in its flight and technical characteristics, the assessment of the change of the LTC helicopter is mandatory. Methods and methods of flight studies on the evaluation of LTD were based on the works of V.S.Vedrov, A.P.P roskuryakov, M.L.Milya, G.S.Kalachov, L.M.Berestov, A.I.Akimov.&#x0D; Flight research is the main scientific activity of the State Scientific Research Institute for Testing and Certification of Weapons and Military Equipment and during modernizations, the development of various new weapons and equipment is an important scientific problem.

Treatment of a newborn with birth trauma of the liver with catheter embolization of a vessel

Birth trauma of the liver with the development of subcapsular hematoma and hemoperitoneum is reported extremely rarely. The slow enlargement of the hematoma also results in delayed development of bleeding symptoms. Noticeable clinical manifestations appear simultaneously when the hematoma ruptures into the abdominal cavity. Later, the symptoms develop very quickly that doctors failed to understand the root cause of the bleeding. The diagnosis is established only during autopsy. When conservative therapy is ineffective, open surgery is conducted; however, the surgery is associated with a high risk of unfavorable outcomes. Herein, we present a clinical case demonstrating successful treatment with endovascular embolization of a vessel due to bleeding from a giant subcapsular hematoma of the liver in a newborn.&#x0D; The child was born in a settlement of the Arkhangelsk Region and weighed 3480 grams. A vacuum extractor was used to assist the weak mother during delivery. The child was in a critical condition and suffered from asphyxia. Mechanical ventilation was used. At 10 h after birth, the child was taken to a specialized neonatal center of Arkhangelsk (the helicopter flight took 2.5 h). The intensive therapy continued. Negative dynamics followed. At 25 h after birth, hemodynamic indexes decreased. X-ray and ultrasound investigations of the abdominal cavity revealed a large hematoma in the liver. It occupied the entire area of the right liver lobe. Abdominal bleeding was diagnosed. The child was taken to the X-ray department. The newborn underwent urgent endovascular embolization of the right hepatic artery. The bleeding was stopped, and the childs condition was stable. On follow-up at age 1 year and 5 months, the childs development was in accordance with age, and blood biochemical parameters were within normal limits. Ultrasound data revealed well recovery of the liver structure.&#x0D; With extensive birth trauma of the liver, minimally invasive surgery, i.e., endovascular embolization of vessels, can be considered an alternative option to surgical treatment.