Rotary Wing Research Articles

Sistema de Guerra Eletrônica para autodefesa de helicópteros de combate

The present work proposes a methodology to support in the design phase of an Electronic Warfare Self-protection System for battlefield helicopters. Hence, the main threats and alternative systems were pointed out through literature review aiming the increase of survival probability in a hostile environment. The awareness of helicopter pilots on the degree of importance of the possible configurations of a self-protection system was also evaluated. The proposed methodology is based on the Analytic Hierarchy Process (AHP) method. A hypothetical situation employing three aerial platforms was analyzed by ten rotary wings pilots as a procedures validation. The results were consistent with possible real situations according to recent conflicts. This methodology gathers quantitative values to the results analysis instead of qualitative criteria, reducing the subjectivity in decision making process for acquisition and in the development of new projects.

Neural Network Design and Training for Longitudinal Flight Control of a Tilt-Rotor Hybrid Vertical Takeoff and Landing Unmanned Aerial Vehicle

This paper considers a hybrid vertical take-off and landing (VTOL) unmanned aerial vehicle (UAV). By tilting its propellers, the aircraft can transition from rotary-wing (RW) multirotor mode to fixed-wing (FW) mode and vice versa. A novel architecture of a neural network-based controller (NNC) is presented. An “imitative learning” approach is employed to train the NNC to mimic the response of an expert but computationally expensive model predictive controller (MPC). The resulting NNC approximates the MPC’s solution while significantly decreasing the computational cost. The NNC is trained on the longitudinal axis. Successful simulations and real flight tests prove that the NNC is suitable for the longitudinal axis control of a complex nonlinear system such as the tilt-rotor VTOL UAV through a sequence of transitions between the RW mode to the FW mode, and vice versa, in a forward flight.

Research on aerodynamic and ballistic characteristics of rotary wing type aerodynamic layout rocket

Abstract Rockets with a rotating wing type pneumatic layout as the research object, using the method of numerical simulation of subsonic stage of the rocket was studied at different attack angles, Mach Numbers and aerodynamic characteristics under different conditions of rudder Angle, and obtained the corresponding pneumatic parameters, and the influence of the relationship between the aerodynamic parameters. The motion equations of rocket are established, the force and moment of rocket during flight are analyzed, and the ballistic characteristics under different muzzle velocity and different launch elevation are simulated and analyzed, and the ballistic effects of different muzzle velocity conditions are obtained.

Aerodynamic efficiency enhancement effect of the energy capture technique on a flyable flapping wing rotor system

Aerodynamic efficiency enhancement effect of the energy capture technique on a flyable flapping wing rotor system

Numerical Simulation and Experimental Verification of Rotor Airflow Field Based on Finite Volume Method and Lattice Boltzmann Method

The primary focus of research in agricultural unmanned aerial vehicle (UAV) pesticide application technology is the investigation of droplet drift and deposition. The influence of the rotor airflow on droplets is particularly significant, making numerical simulations a crucial tool for airflow field analysis. Among existing numerical simulation methods, the Finite Volume Method (FVM) and the Lattice Boltzmann Method (LBM) are commonly used, but there is limited research that compares the two approaches. Therefore, this paper conducts numerical simulations of the rotor airflow of an agricultural UAV using Fluent, representing the FVM, and XFlow, representing the LBM. This research aims to reveal the distribution patterns of airflow field numerical simulations under different theoretical methods, validate them through practical experiments, and select the optimal method for simulating rotor airflow. The ultimate goal is to establish an effective airflow field model to enhance the precision of pesticide application by an agricultural UAV. The results indicate that the lift error calculated by XFlow in this paper is 2.57% smaller than that by Fluent. The wind field of Fluent entered the “stable state” earlier than XFlow, and the speed value of Fluent was smaller than that of XFlow. The difference between the two speed values became larger and larger as the distance from the rotor was longer. Compared with XFlow, Fluent changes more obviously in the core region, and the center region gradually disappears with the distance from the rotor. However, in the velocity field calculated by XFlow, there are still more turbulent flows outside the core region, indicating that the transient calculation method based on the LBM can better show the details of fluid flow than the steady-state calculation method based on the FVM. Through comparison with the actual test data, it is found that the relative error of the velocity value of XFlow at 0.2 m and 0.4 m is small, while that of Fluent at 0 and 0.2 m is small. It shows that XFlow simulation has higher accuracy for external turbulent flow, while Fluent simulation has higher accuracy for steady laminar flow. The research results provide data comparison and a basis for further analysis of the wind field model of the rotor wing of the plant protection UAV, and they lay a foundation for further research on precision application technology.

Maximization of Flight Performance of Eight-Rotor Multirotor with Differentiated Hub Angle

The aim of this article is to design a rotary wing aircraft autopilot system that improves flight performance by changing the body shape during flight. The method is to obtain values that stabilize the longitudinal and lateral flight of the aircraft, where the amount of metamorphosis and Proportional-Integral-Derivative (PID) coefficients are determined using the simultaneous perturbation stochastic approximation (SPSA) optimization algorithm. The rotary wing aircraft has a deformable structure with eight rotors. Shape-changing rotary-wing aircraft are aircraft that can fly with the lift generated by propellers. Aerial platform; It consists of arms and trunk. The angle between mechanism A and the arm to which the rotors are connected can be changed with the horizontal plane and different configurations are obtained. When the angle between the arms is 45°, the octo configuration turns into a stable structure, while when the angle between the arms is 0°, the X8 configuration provides high maneuverability and increased controllability. Metamorphosis, its effect on longitudinal and lateral flight stability and improvement studies were carried out in a simulation environment and the results are presented in this study. As a result of the shape change, longitudinal and lateral narrowing occurred by 26.8° percent. Simulation tests were modeled in a closed environment, free from atmospheric effects. The obtained flight performance values are presented in Tables.

Statistical Analysis of Airfoil Usage in Aircraft

The study aims to answer how frequently airfoils are used in fixed and rotary wing aerial vehicles produced both individually and based on airfoil families. Frequency distribution analysis of airfoil utilization in fixed-wing and rotary-wing aircraft helps in understanding design preferences and performance needs and constraints. The literature study provides the history of airfoils, the subjects mostly studied regarding airfoils and mentions the current state of the field. The study investigates the airfoil families to which the wing profiles of approximately 6,000 fixed-wing and approximately 450 rotary-wing aircraft belong through frequency distribution. The results indicate that in fixed-wing aircraft, NACA airfoils are used in 52.2%, Clark-Y airfoils in 8.2%, Goettingen airfoils in 5.9%, Wortman airfoils in 4.8%, and TsAGI airfoils in 3.1%. When considered as singular airfoil use rather than airfoil families, Clark-Y is the most widely used airfoil, followed by the NACA 23XXX series. In rotary-wing aircraft, NACA 0012 and NACA 0015 airfoils, both symmetrical profiles developed by NACA, are the most widely used. The study is valuable as it provides statistical data on the use of both airfoil families and singular airfoil design in fixed and rotary-wing aircraft. However, it is important to note that the airfoil data is incomplete, and the study aims to provide a general impression of the findings.

CFD Analysis of Takeoff from a Water Surface for an Insect-Scale Aerial/Aquatic Robot

To develop an insect-scale aerial/aquatic robot, we analyzed takeoff mechanisms to counteract surface tension, such as paddling, slapping, and clap-and-fling. Because a diving beetle, Eretes griseus, takes off directly from the water surface, a flapping-wing robot is promising as an alternative to a drone with multiple rotary wings. In this study, we first investigated diving beetle flight with a three-dimensional high-speed camera system and analyzed the motion characteristics. Subsequently, we developed a computational fluid dynamics method that tracked the water surface using a volume of fluid method, reproduced the motion with a multibody model, treated the deformation of the elastic membrane wing with the phase delay of the joint angle functions, and simulated takeoff, that is, the transition from water to air, and hovering near the water surface. The simulation result showed that during the transition, the slapping motion exerted the maximum and average lift per unit of body weight of 18 and 9.2, respectively, while those of paddling produced 0.46 and 0.23, respectively. The water surface effect improved the lift by 25% at the normalized height of less than 0.44 and disappeared at a height greater than 0.7. During hovering, while the clap-and-fling motion improved lift by 2.6% and the water surface effect was 9.8%, the synergy effect was 22%. In addition, the former enhanced it significantly after the fling, while the latter was remarkable during the wing acceleration phase. In contrast to ground effects, flapping reduced the water level and caused the ripples, dynamically changing the water surface effect.

On the Growth of Small Cracks in 2024‐T3 and Boeing Space, Intelligence and Weapon Systems AM LPBF Scalmalloy®

ABSTRACTThe desire to use additively manufactured (AM) parts to ensure the availability of military aircraft, and to build limited‐life unmanned aerial vehicles (drones), coupled with the United States Air Force (USAF) approach to the airworthiness certification of AM parts has focused attention on durability analysis/assessment, and hence on the growth of small cracks in AM parts. Previous studies have shown that laser powder fusion built (LPBF) Scalmalloy® has: i) A yield stress and an ultimate strength that are greater than that of AA2024‐T3 and comparable to that of AA7075‐T6; ii) A resistance to crack growth that is better than that of AA7075‐T6 and comparable to that of AA2024‐T3. However, since the ability to predict the durability of a part is essential for its airworthiness certification, the present paper illustrates how to perform a linear elastic fracture mechanics (LEFM)‐based durability assessment of Boeing Space, Intelligence and Weapon System (BSIWS) LPBF Scalmalloy®. The durability study includes specimens with both machined surfaces and surfaces left in the as‐built condition. As a result, it would appear that BISWS AM LPBF Scalmalloy® is an ideal candidate for building limited‐life AM replacement parts for fixed and rotary wing aircraft and drones.

Burden and Risk Factors of Cervical Spine Conditions in Military Aircrew From 1997 to 2015: A Retrospective Cohort Study.

Military aviators may have increased risk of cervical spine injuries because of exposure to supraphysiologic forces and vibration during dynamic flight. Aviator medical attrition impairs mission readiness, decreases operational capabilities, increases overall DoDcosts, and decreases retention of seasoned aviators. This study evaluated incidence and risk factors for cervical spine conditions in U.S. military aviators from 1997 to 2015. The Defense Medical Epidemiological Database was queried for aviators with a diagnosis of cervical spine conditions. Pertinent ICD-9 codes for cervical spine pathology were ascertained from U.S. Army, Air Force, and Naval Air Forces aeromedical references. Negative binomial regressions assessed sex, age, service, aircraft, and year on incidence of conditions. Rates were compared to non-aviator controls. The study was approved by the Institutional Review Board at the Naval Health Research Center (NHRC.2020.0205-NHSR). Incidence rates were 9.78 to 12.57/1,000 person-years for neck pain, 2.04 to 3.89/1,000 person-years for degenerative conditions without neurological involvement, and 0.94 to 1.36/1,000 person-years for degenerative conditions with neurological involvement. Aviation occupation (relative risk [RR] 1.41-2.05), female sex (RR 3.32-7.89), age over 40 (RR 2.39-4.62), and service in the Army or Marine Corps (RR 1.62-2.14) were risk factors. Military aviators had a statistically significant increase in risk of neck pain and medically disqualifying degenerative cervical spine conditions compared to non-aviator controls. Rates of neck pain increased in all aviators over the study epoch. Possible explanations could be related to the operational demands and the increased use of forward helmet-mounted display systems during the study period, a supposition that requires further investigation. There was no significant difference in rates of neck pain or degenerative cervical conditions between aircraft platforms (fighter/bomber, other fixed wing, and rotary wing). Female sex, age over 40 years, and Army/Marine Corps service were the greatest risk factors for neck pain and degenerative cervical spine conditions. Targeted prevention programs and expanded treatment modalities are necessary to reduce aviator attrition and Department of Defense cost burden.

Hypothermia and the Global War on Terror: 18 Years of Minimal Progress.

The association between hypothermia, coagulopathy, and acidosis in trauma is well described. Hypothermia mitigation starts in the prehospital setting; however, it is often a secondary focus after other life-saving interventions. The deployed environment further compounds the problem due to prolonged evacuation times in rotary wing aircraft, resource limitations, and competing priorities. This analysis evaluates hypothermia in combat casualties and the relationship to resuscitation strategy with blood products. Using the data from the Department of Defense Joint Trauma Registry from 2003 to 2021, a retrospective analysis was conducted on adult trauma patients. Inclusion criteria was arrival at the first military treatment facility (MTF) hypothermic (<95ºF). Study variables included: mortality, year, demographics, battle vs non-battle injury, mechanism, theater of operation, vitals, and labs. Subgroup analysis was performed on severely injured (15 < ISS < 75) hypothermic trauma patients resuscitated with whole blood (WB) vs only component therapy. Of the 69,364 patients included, 908 (1.3%) arrived hypothermic; the vast majority of whom (N = 847, 93.3%) arrived mildly hypothermic (90-94.9°F). Overall mortality rate was 14.8%. Rates of hypothermia varied by year from 0.7% in 2003 to 3.9% in 2014 (P <0.005). On subgroup analysis, mortality rates were similar between patients resuscitated with WB vs only component therapy; though base deficit values were higher in the WB cohort (-10 vs -6, P < 0.001). Despite nearly 20 years of combat operations, hypothermia continues to be a challenge in military trauma and is associated with a high mortality rate. Mortality was similar between hypothermic trauma patients resuscitated with WB vs component therapy, despite greater physiologic derangements on arrival in patients who received WB. As the military has the potential to conduct missions in environments where the risk of hypothermia is high, further research into hypothermia mitigation techniques and resuscitation strategies in the deployed setting is warranted.

Application of Time-Variant Systems Theory to the Unsteady Aerodynamics of Rotary Wings

This work employs the principles of time-variant systems theory to investigate the unsteady aerodynamics of rotary-wing configurations under periodic equilibrium conditions. Their application enables an extension of the pulse technique for system identification, as well as the adaptation of the linear-frequency-domain formulation commonly utilized in fixed-wing to rotary-wing scenarios. These methodologies effectively incorporate the aerodynamic nonlinearities associated with the equilibrium state into an efficient time-variant linearized representation of the unsteady aerodynamics. To promote its application in the context of rotary-wing aeroelasticity, a state-space realization based on a periodic autoregressive model with exogenous input is subsequently employed. Upon transformation from discrete to continuous time, the resulting aerodynamic model adopts a linear continuous-time periodic state-space formulation, offering compatibility for its coupling with a wide range of structural models. The proposed aerodynamic framework tailored to rotary-wing aeroelasticity holds applicability across a spectrum of aerodynamic models of arbitrary complexity, spanning from incompressible potential flow approximations to potentially more sophisticated methods. Showcasing the potential of this framework, the widely studied lossy Mathieu equation and the aerodynamic response to a flap perturbation about the periodic equilibrium condition of a prototypical rotor blade section, incorporating nonlinearities through an analytical dynamic stall model, are considered.

Prevalence of barodontalgia in military pilots of the Brazilian Air Force

Introduction: Barodontalgia refers to the painful condition affecting previously asymptomatic teeth and periodontal tissues, caused by changes in atmospheric pressure during flight. This study aimed to evaluate the prevalence of barodontalgia in Brazilian Air Force (FAB) pilots. Materials and Methods: An exploratory study was carried out, with a convenience sample, made up of military pilots, regardless of age group and type of aircraft, using a structured questionnaire and descriptive analysis of the data. Results: 141 pilots participated; men; 37.3 ± 3.6 years; 40.6% were transport pilots, 14.1% fighter, 9.4% rotary wing, and 35.8% Instruction/Demonstration. The prevalence of barodontalgia was 12.8% (18 occurrences). Three missions were interrupted. Regarding knowledge of barodontalgia, 56 (39.7%) reported regular knowledge and 21 (15%) declared they had no knowledge on the subject. Conclusions: It is concluded that the prevalence of barodontalgia in Brazilian military pilots is higher than the values reported by some air forces of developed countries, already indicating the need for a more in-depth look at the oral health of FAB military personnel.

Inter hospital transfers in rotor wing aircraft. Patterns and challenges. Protocol for a scoping review.

Inter-hospital transfer is necessary for the transport of patients to specialized treatment. Rotor-wing aircraft may be used in lieu of ambulances in time-critical conditions over long distances and when specialist team skills are called for. The purpose of the review is to assess the current scientific literature that describes the scenario to develop a national guideline for inter-hospital transfers using rotor-wing aircraft. The aim is to describe the patterns and challenges. The authors will conduct a scoping review as per Joanna Briggs Institute guideline. The protocol for the scoping review will adhere to the Open Science Framework guideline for scoping reviews and we will report the findings of the scoping review as per PRISMA-ScR guideline. We have developed the search strategy with the help of a research librarian and will conduct search in relevant electronic databases and include gray literature as well, using the PRESS and PRISMA-S guidelines. Two authors will independently screen titles and abstracts for inclusion as per eligibility criteria and conflicts will be resolved by a third reviewer. Full text retrieval will be conducted accordingly. We will analyze the extracted data using validated statistical methods. According to Danish law, scoping reviews are exempt from ethics committee approval. The findings of this scoping review will provide the scientific foundation for a national guideline on rotor-wing aircraft conveyed inter-hospital transfers in Denmark. Furthermore, we will publish the results of the scoping review in a relevant scientific journal.

An Experimental Investigation Of µUAV Rotor Wingtip Vortices Through High Spatial Resolution PIV

The interest for µ UAVs platforms with VTOL capabilities dramatically rose over the last decade due to the fast-paced advancements in electronics and control. However, the vortical structures shedded from the rotary wings -and their interaction-, which are responsible for high power usage and high noise level emissions, are yet to be fully understood. In this work, an experimental PIV campaign was conducted on a commercially available propeller with a 230mm diameter. The operating angular velocity was chosen to be 5750RPM, producing a chord Reynolds number of about Re_{c,75%} ≃ 11000, generating 3.42N of thrust while requiring 55W of power. The resolution of the PIV setup was able to reliably fit 8 measurement points in the vortex core when using narrowest field-of-view (FOV), while the widest FOV comprises a measurement area of about 0.5D×0.57D. Time averaged as well as phase averaged measurements were performed. The evolution and interaction of the wingtip vortices and shear layers shedded in the flow field is captured with an azimuthal angle step increment of ∆Ψ = 5º. The thrust produced by the multirotor configuration was indeed found to be approximately 5% lower than the one produced by the isolated propeller in hovering conditions. Additionally, the PIV setup successfully met the target spatial accuracy requirements: induced velocities are accurately captured in every stage of the wingtip vortex evolution.

The Impact of Location and Asset Type on the Success of Advanced Airway Management in a Critical Care Transport Environment

ObjectiveAdvanced airway management (AAM) is a critical component of prehospital critical care. Airway management in flight can be more challenging because of spatial, ergonomic, and environmental factors. This study examines the frequency of in-flight intubation (IFI), first-pass success (FPS) rates, and definitive airway sans hypoxia/hypotension on first attempt (DASH-1A) across different locations of airway management. MethodsWe conducted a retrospective database analysis of all patients transported between January 2016 and July 2021 who received AAM from a single air medical service. Patient records were reviewed for location of intubation, patient characteristics, and FPS and DASH-1A rates. The primary outcome was the frequency of IFI. The secondary outcomes included FPS and DASH-1A rates by location and type of transport asset. ResultsDuring the study period, 473 patients required AAM. Three percent (15/473) of patients were intubated in an in-flight setting, 28% (130/473) were intubated on scene, and 70% (328/473) were intubated in a health care facility. The primary reason for IFI was unanticipated cardiac arrest or clinical deterioration. The overall FPS rate was 69% (328/473), and the DASH-1A rate was 49% (194/399). Based on the location of AAM, the FPS and DASH-1A rates were the lowest for on-scene intubations (56% [74/130] and 27% [20/74], respectively). Most of the on-scene AAM took place with rotor wing flight crews. ConclusionAirway management occurs infrequently in an in-flight setting and is necessary because of patient deterioration or cardiac arrest. Based on our results, we identified opportunities for targeted AAM quality improvement and clinical governance.

Aerodynamic optimization of a micro flapping rotary wing in hovering flight

Aerodynamic optimization of a micro flapping rotary wing in hovering flight

Stochastic optimal tuning for flight control system of morphing arm octorotor

PurposeThis study aims to discuss the simultaneous longitudinal and lateral flight control of the octorotor, a rotary wing unmanned aerial vehicle (UAV), for the first time under the effect of morphing and to improve autonomous flight performance.Design/methodology/approachThis study aims to design and control the octorotor flight control system with stochastic optimal tuning under morphnig effect. For this purpose, models of different arm lengths of the octorotor were drawn in the Solidworks program. The morphing was carried out by simultaneously lengthening or shortening the arm lengths of the octorotor. The morphing rate was estimated by using simultaneous perturbation stochastic approximation (SPSA). The stochastic gradient descent algorithm, which is frequently used in machine learning, was used to estimate the changing moments of inertia with the change of arm lengths. The proportional integral derivative (PID) controller has been preferred as an octorotor control algorithm because of its simplicity of structure. The PID gains required to control both longitudinal and lateral flight were also estimated with SPSA.FindingsWith SPSA, three longitudinal flight PID gains, three lateral flight PID gains and one morphing ratio were estimated. PID gains remained within the limits set for SPSA, giving satisfactory results. In addition, the cost index created was 93% successful. The gradient descent algorithm used for the moment of inertia estimation achieved the optimum result in 1,570 iterations. However, in the simulations made with the obtained data, longitudinal and lateral flight was successfully carried out.Originality/valueOctorotor longitudinal and lateral flight control was performed quickly and effectively with the proposed method. In addition, the desired parameters were obtained with the optimization methods used, and the longitudinal and lateral flight of the octorotor was successfully carried out in the desired trajectory.

Aircraft Designed for Cargo Transportation and Investigation of its Benefits

In this study, an Octorotor UAV capable of carrying 10 desi/2 kg cargo was designed. It is an eight-rotor rotary wing aircraft and its body consists of eight arms connected to each other by two moving mechanisms. When requested in emergency situations, the fastest intervention can be provided by aircrafts. The auxiliary battery and generator system carried by the aircraft is to provide enough energy to reach the nearest electric charging station for the stranded vehicles. In cases such as disasters, the rapid delivery of health supplies can also be provided by this method. The aircraft designed for this purpose has a rotary wing and a feature that can change its body structure according to different load and weather conditions. The shape change improves its performance compared to conventional aircraft and increases its ability to fulfil its mission. For this purpose, the design of a shape-changing aircraft was realized.

Tip of the Spear: Developing Predictive Military Planning Tools Using Hidden Markov Models

The evolution of the modern battlefield is increasingly complex as new technologies emerge. However, the nature of the battlefield still can be explained by Baron De Jomini’s “Grand Tactics.” Military planners’ success is in their ability to develop synergy through layering effects of a complex system at a decisive point on the battlefield. Synergistic effects require subject matter experts (SME) working in planning cells to integrate systems and units in time and space. These planning cells have large footprints and become prioritized in the opposition’s targeting cycle. Without these SMEs, planners are unable to identify the latent variables to achieve the massing of forces at the decisive point. This paper explores the application of Hidden Markov Models (HMMs) to enhance existing Correlation of Forces and Means (COFM) calculators as predictive tools in military planning. Current tools focus on a 3 to 1 force ratio for an offensive operation. They get improved through applying a force equivalent factor. The force equivalent factors are scalars that adjust relative combat power from a single main battle tank to a mechanized infantry vehicle. These tools lack the ability to identify the physics of the battlefield in time and space. The utilization of wargames during planning and training provides a venue for serious games to improve planning tools. It allows a visualization of target pairing and dynamics that a linear equation would miss. This study employs scenarios generated in OneSAF, ranging from simple platoon-level ambushes to combined arms maneuver featuring rotary wing assets requiring a shaping effort to ensure favorable COFMs. The focus of the research lies in leveraging HMMs to establish a time-series indicator of success probability using potentially observable data, with an emphasis on communication dynamics. In this study, we examine observable communication by data generated through both visual and direct contact. Through observation of contact from the friendly and opposition forces will provide a predictor of the hidden state of relative advantage, in time and space. With the data generated by the OneSAF simulation, the HMM determines the states of the operation and probability of success while minimizing required presence inside the units.