Naval Aircraft Research Articles

Advanced finite element modeling methods for tensile and bending analysis of arresting gear cables

This study addresses the gap in understanding the dynamic bending behavior of multi-layer twisted steel cable, pivotal in various industrial applications such as naval aircraft arresting systems. Utilizing advanced finite element modeling, the research explores the mechanical responses of these cables under macroscopic bending scenarios. By integrating beam elements and connectors within the finite element framework, the study simulates complex inter-strand interactions under various loading conditions. Results indicate that this method significantly enhances the prediction accuracy of the cables’ mechanical properties, thus offering substantial improvements in design and performance analysis of arresting gear systems. This study’s value lies in its potential to refine mechanical modeling of complex cable systems, thereby optimizing operational efficiency and safety in engineering applications.

Numerical Simulation of the Unsteady Airwake of the Liaoning Carrier Based on the DDES Model Coupled with Overset Grid

The wake behind an aircraft carrier under heavy wind condition is a key concern in ship design. The Chinese Liaoning ship’s upturned bow and the island on the deck could cause serious flow separation in the landing and take-off area. The flow separation induces strong velocity gradients and intense pulsations in the flow field. In addition, the sway of the aircraft carrier caused by waves could also intensify the flow separation. The complex flow field poses a significant risk to the shipboard aircraft take-off and landing operation. Therefore, accurately predicting the wake of an aircraft carrier during wave action motion is of great interest for design optimization and recovery aircraft control. In this research, the aerodynamic around an aircraft carrier (i.e., Liaoning) was analyzed using the computational fluid dynamics technique. The validity of two turbulence models was verified through comparison with the existing data from the literature. The upturned bow take-off deck and the right-hand island were the main areas where flow separation occurred. Delayed detached eddy simulation (DDES), which combines the advantages of LES and RANS, was adopted to capture the full-scale spatial and temporal flow information. The DDES was also coupled with the overset grid to calculate the flow field characteristics under the effect of hull sway. The downwash area at 15° starboard wind became shorter when the hull was stationary, while the upwash area and turbulence intensity increased. The respective characteristics of the wake flow field in the stationary and swaying state of the ship were investigated, and the flow separation showed a clear periodic when the ship was swaying. Comprehensive analysis of the time-dependent flow characteristic of the approach line for fixed-wing naval aircraft is also presented.

Modeling the Transient Dynamics of Arresting Hooks and Cables through the Parameter Inversion Method

Arresting gear systems play a vital role in carrier-based aircraft landing. In order to accurately understand the process of arresting hook and cable, this study introduces a parameter inversion method to model the arresting cable and applies it to the transient dynamics model of the arresting hook and cable. The feasibility of the arresting cable model and its application to the transient dynamics model of the arresting hook and cable are validated through arresting hook and cable impact tests. The study compares three different models of arresting cables for simulation results and concludes that assuming the arresting cable to be a beam with metal elastic parameters during the modeling process cannot ignore the influence of the cable’s torsional and bending stiffness on the modeling. The study also investigates the dynamic response of the arresting hook during the aircraft arrestment and hooking process and concludes that the stress peak of the hook arm is much lower throughout the entire arrestment process than at the moment of hooking the cable. The study further identifies factors that affect the stress on the arresting hook arm, such as the aircraft’s yaw angle, deck angle, cruising speed, and the initial position of the arresting hook and cable before engagement. The research results have significant implications for improving the design optimization of the structural strength of the functional components of the naval aircraft arresting system and provide theoretical guidance and technical reserves for subsequent related studies.

Differential equations of oscillation of thin plates with point bonding

Abstract The relevance of the research results presented in this article lies in the general concept of elasticity theory, which integrates the bases of theoretical-empirical physics, practical mathematics and the natural implementation of modelling results in the fields of industrial (to a large extent in the design and manufacture of aircraft and naval aircraft shells and fuselages), construction (more so in the design and formation of multi-layer building structures), electronics and other areas of the science and industry complex. The aim of the study is to form a mathematical model of thin plate vibration based on a system of differential equations for the computational case of point bonding. The method of scientific search (Multilocal Literature Review) is used to achieve the set goal, which made it possible to establish the actual scientific-theoretical basis of the investigated problem, the method of mathematical modelling allowing to systematize the systems of differential equations developed earlier and formed in the framework of the present study, both for the general concept of the theory of elasticity of thin plates and for a selected calculation situation with partial constraints in the form of point bond imposing. As a result of the investigations conducted in the framework of this study, a mathematical model of the oscillations of thin plates bounded by special point-coupling conditions has been obtained, consisting of a system of differential equations obtained by successive iterations of mathematical transformations for the generated local boundary conditions. The mathematical model obtained is of practical scientific interest. The developed model environment forms a complete mathematical theory of elasticity for the formulated problem of the oscillatory process of thin plates with bounding point couplings. This problem has not received a satisfactory mathematical apparatus because of the complexity and cumbersomeness of analytical methods to describe the investigated elastic object.

Study on the Corrosion Resistance of Laser Clad Al0.7FeCoCrNiCux High-Entropy Alloy Coating in Marine Environment

In the marine atmosphere, the corrosion rate of ship components is 4–5 times higher than that of the inland atmosphere. To solve the serious corrosion problem arising from long-term service in the marine environment of naval aircraft and ships, etc., this paper takes Al0.7FeCoCrNiCux system high-entropy alloy coating prepared by laser melting technology with 5083 aluminum alloys as the base material and analyzes the aging and failure mode of equipment coating under a marine atmospheric environment. XRD and SEM were utilized to study the microscopic morphological structure of the coatings. The laws of influence of Cu elements on the electrochemical corrosion behavior of the Al0.7FeCoCrNiCux system high-entropy alloy in 3.5 wt.% NaCl neutral solution was investigated by using dynamic potential polarization and electrochemical impedance spectroscopy, and neutral salt spray acceleration tests and outdoor atmospheric exposure tests were carried out. The results show that the Al0.7FeCoCrNiCux (x = 0) high-entropy alloy coating has a single BCC phase structure and the Al0.7FeCoCrNiCux (x = 0.30, 0.60, 0.80, 1.00) high-entropy alloy coating consists of both BCC and FCC phases with a typical dendrite morphology. With the increase in Cu content, the self-corrosion potential of Al0.7FeCoCrNiCux gradually increases and the current density gradually decreases, which with the results of the electrochemical impedance spectrum analysis, indicating that the corrosion resistance of Al0.7FeCoCrNiCu1.00 is optimal. The results of the neutral salt spray acceleration test and the outdoor atmospheric exposure test were integrated to conduct a comprehensive evaluation of the corrosion resistance of the coating. The corrosion resistance of Al0.7FeCoCrNiCux coating increases with the increase in Cu content, and the impressive strength and plastic deformation are best when x = 0.80. Neutral salt spray accelerated the test with no corrosion at 5040 h, and even if the coating is broken, it can last up to 4320 h. In the outdoor atmospheric exposure test, which was conducted 12 months after the coating surface test, no corrosion occurred.

Automated Sortie Scheduling Optimization for Fixed-Wing Unmanned Carrier Aircraft and Unmanned Carrier Helicopter Mixed Fleet Based on Offshore Platform

Optimizing naval aircraft deck sortie scheduling is important for improving the sortie efficiency of naval aircraft groups. It is also an important link in realizing the automated scheduling of aircraft carriers. Firstly, a single-aircraft surface transit path library was constructed. This paper used the improved A* algorithm and the optimal control deck path planning algorithm to construct the transit path library between the deck parking position and take-off position, or between warmable and non-warmable parking positions. Secondly, a mathematical optimization model was constructed for the sortie scheduling of a mixed fleet of fixed-wing carrier aircraft and carrier helicopters. The model took the maximum sortie time of the fleet and taxiing time of the fleet of fixed-wing aircraft as the optimization objectives, and considered the process flow, spatial, and resource constraints. Thirdly, a discretized improved whale optimization algorithm (IWOA) was designed to solve the problem. To improve the optimization-seeking capability of the algorithm, we discretized the algorithm, optimized its coding method, and introduced pre-constraints, learning factors, parameter improvements, and population restart. Finally, we set up various cases and proposed a new strategy for simulation experiments: these simulations verified the validity of the model, the excellent optimization performance of the IWOA, and the superiority of the sortie strategy. The research in this study will help to implement automated aircraft carrier scheduling.

Performance of dodecyl dimethyl benzyl ammonium chloride as bactericide and corrosion inhibitor for 7B04 aluminum alloy in an aircraft fuel system

In this study, the broad-spectrum antimicrobial property of dodecyl dimethyl benzyl ammonium chloride (DDBAC) was investigated against three species of bacteria, Lysinibacillus sphaericus ( L. sphaericus ), Acinetobacter lwoffii ( A. lwoffii ), and Sediminibacterium salmoneum ( S. salmoneum ) isolated and purified from a naval aircraft fuel system. Through the inhibition zone method and minimum inhibitory concentration test, DDBAC was found to have a good antimicrobial performance with a minimum inhibitory concentration of 64 mg/L. The influence of DDBAC on the corrosion behavior of fuel tank material was evaluated by electrochemical measurements, such as polarization curve and electrochemical impedance spectroscopy (EIS). The polarization curve indicated that DDBAC suppressed anodic and cathodic reactions as a mixed-type corrosion inhibitor, and the inhibition efficiency was 68.38% at the concentration of 80 mg/L after 28 days of immersion. The EIS results showed that DDBAC inhibited the corrosion of 7B04 aluminum alloy in the concentration range of 40–120 mg/L. The DDBAC adsorption on the aluminum alloy surface was in agreement with the modified Langmuir adsorption isotherm model. The quantum chemical calculations proved that a lone pair of electrons of nitrogen atoms in DDBAC were able to form coordinate bonds with the empty orbital in aluminum, resulting in a tight chemisorption layer on the aluminum alloy surface and corrosion inhibition.

Exploring a model nuclear planning and response program: Evaluating public awareness of written risk and emergency.

High-reliability organizations (HROs) including commercial airlines, the NASA Space Shuttle engineering team, US Naval aircraft carrier and nuclear submarine crews, and US nuclear power plants are relatively safe. However, these organizations experience system breakdowns often with catastrophic outcomes. This study focuses on risk information management strategies employed by a nuclear energy power plant located within 10 miles of a population center. The evacuation planning zone (EPZ) includes a hospital, several schools, and a public university. The nuclear plant provides written preparedness and evacuation information for all residents within the EPZ in the event of a radiological emergency. Focusing on the campus community within the EPZ, this study investigates individual awareness regarding the potential of a radiological event, the emergency information booklet, and the information provided within the booklet. We use descriptive statistics, frequency distribution, and cross tabulations (contingency tables) to establish awareness levels. Our study determines those participants who read the emergency instructions booklet are prepared to make an informed decision in the event of a radiological incident. We find college affiliation, educational level, university role, and age significantly related to emergency instruction booklet utilization. We also find gender is significantly linked to overall risk perception regarding a radiological event. Findings support previous research regarding women's higher levels of risk aversion and pessimism involving dangerous new risky technologies and activities like nuclear energy plants. These findings support modifying policy to ensure nuclear facilities assess the efficacy of their warning systems in alerting the public. Furthermore, our findings provide guidance regarding the evaluation of the effectiveness of emergency instruction booklet distribution.

The Criminal Jurisdiction and Applicable Law concerning the Fu Yuan Yu Leng 999 Case

Abstract On 13 August 2017, a Chinese-flagged carrier vessel, Fu Yuan Yu Leng 999, entered the Galapagos Marine Reserve (gmr) without giving appropriate notice, on the captain’s explanation that he entered the area to shelter the vessel from strong winds. Ecuadorian naval aircraft and a coastguard ship began to pursue the vessel from the internal waters and it was intercepted within the territorial sea. This area belongs to the new marine sanctuary of the gmr, where high levels of protection are implemented, and all fishing activities are prohibited. This incident reflects that, as the world’s largest distant-water fisheries (dwf) nation, much more needs to be done by China to crack down on illegal, unreported and unregulated (iuu) fishing and to promote the orderly development of dwf.

Spray, Combustion, and Air Pollutant Characteristics of JP-5 for Naval Aircraft from Experimental Single-Cylinder CRDI Diesel Engine

This study was performed to analyze the spray, combustion, and air pollutant characteristic of JP-5 fuel for naval aircraft in a spray visualization system and a single-cylinder CRDI diesel engine that can be visualized. The analysis results of JP-5 fuel were compared with DF. The spray tip penetration of JP-5 showed diminished results as the spray developed. JP-5 had the highest ROHR and ROPR regardless of the fuel injection timings. The physicochemical characteristics of JP-5, such as its excellent vaporization and low cetane number, were analyzed to prolong the ignition delay. Overall, the longer combustion period and the lower heat loss of the DF raised the engine torque and the IMEP. JP-5 showed higher O2 and lower CO2 levels than the DF fuel. The CO emission level increased as the injection timing was advanced in two test fuels, and the CO emitted from the DF fuel, which has a longer combustion period than JP-5, turned out to be lower. NOx also reduced as the fuel injection timing was retarded, but it was discharged at a higher level in JP-5 due to the large heat release. The images from the combustion process visualization showed that the flame luminosity of DF is stronger, its ignition delay is shorter, and its combustion period is longer than that of JP-5.

Lessons from the Lunar Module Program: The Director's Conclusions

Half a century after the first piloted lunar landing, it is time to consider the program, lessons, and legacy of the lander that made it possible. This article does so from the perspective of Joseph Gavin, Jr., who led Apollo's Lunar Module (LM) Program from its unofficial origins as a controversial dream at Grumman in 1960, to its official inception by NASA in 1962, to its successful conclusion in 1972. He directed as many as 7500 employees in developing the LM and ultimately building twelve operational vehicles. All met mission requirements, and those that actually made a lunar landing worked every time. Developing the state-of-the-art machine required unprecedented innovations and maximization of reliability amid inherently unknown and untestable conditions. When congratulated on the success of each landing, Gavin typically replied that he would not be satisfied until his spacecraft and its crew got off the moon and arrived home safely. This process required three procedures in unison (firing of explosive bolts, severing by guillotine of wires and other connections between the descent and ascent stages, and firing of the ascent engine). Each function could be tested on Earth individually, but not under lunar conditions at systems level. Gavin drew lessons from his Grumman Corporation team and its subcontractors' experience that the author distills into eight principles:(1) Above all, return astronauts safely to Earth; accordingly:(2) create conditions for success,(3) attain reliability,(4) prioritize innovation over schedule over cost,(5) don't complicate things unnecessarily;(6) remove hierarchical barriers;(7) empower individuals, and(8) share information.Serving in top management subsequently returned Gavin to the naval aircraft development that remained Grumman's specialty. He applied the best practices learned from LM development, particularly improving initial construction to reduce the need for tests (per principle three). Drawing on extensive interviews with Gavin and thorough examination of his personal materials, this article explores his lessons and explains how he envisioned and applied them in practice as an aerospace project engineer leading one of history's greatest engineering achievements.

Non-Rocket Launch from Mars

In this paper, we examine a method for launching payloads from Mars, which is an alternative to a rocket launch. The idea is based on the elevator concept using a tether, one end of which is rigidly connected to the natural Martian satellite and the other end has a hook. The lifting device of the tether should capture the spacecraft on the Martian surface by the hook similar to the capturing of a ship-borne aircraft on a naval aircraft carrier. We believe that the required space elevating equipment will be developed in the coming decade.

Reducing noise from twin supersonic jets using very-low-frequency control

The intense jet noise radiated by closely spaced, twin supersonic hot jets leads to sound-induced structural vibration, fatigue and personnel related operational difficulties. Experimental, theoretical, and computational investigations into the physics and control of jet noise have identified several important sound sources, including wavepackets, screech, Mach wave radiation, and broadband shock associated noise (BBSAN). Reducing the loudest sources of jet noise, without sacrificing propulsive performance, has relied on intuition, parametric survey, or optimal control techniques. With the aim of developing a more general and robust method of jet noise reduction (JNR), we present a physics-based approach that leverages very-low-frequency jet dynamics in order to achieve JNR whilst preserving propulsive performance. Our approach formulates the control problem using the very-low-frequency global modes of the compressible Navier-Stokes operator linearized about the jet mean flow to disrupt the nonmodal transient growth processes. The presentation will showcase uncontrolled and controlled single and twin supersonic hot jets issuing from biconical nozzles, with conditions and geometries motivated by tactical Naval aircraft. The predictions utilize fully resolved numerical simulations whose data inform the control development and which evaluate its performance on the jet exhaust and on its radiated noise.

Building environmental history for Naval aircraft

Abstract The operating environment of Navy aircraft varies to a good degree depending upon the squadron location, flight requirements, and other field and ground activities. All these conditions promote corrosion of one type or the other. The aircraft operations will also have influence on the type of corrosion. Thus, building an environment history that can monitor and track the damage development in many areas of the aircraft structure based on aircraft activities, operating environment, and service history data is crucial. The development of such environmental history builder has two main advantages: first, it provides a tool to treat corrosion as a structural issue, and second, it accounts for time variation of environmental factors such as relative humidity (RH) and temperature rather than average environmental data. This paper will demonstrate how the environmental history builder could be used, in conjunction with predictive models, to predict corrosion damage.

Physical Therapists Forward Deployed on Aircraft Carriers: A Retrospective Look at a Decade of Service.

Navy physical therapists (PTs) have been a part of ship's company aboard Aircraft Carriers since 2002 due to musculoskeletal injuries being the number one cause of lost duty time and disability. This article describes a decade of physical therapy services provided aboard aircraft carriers. A retrospective survey was conducted to evaluate the types of services provided, volume of workload, value of services provided, and impact of PTs on operational readiness for personnel aboard Naval aircraft carriers. Thirty-four reports documenting workload from PTs stationed onboard aircraft carriers were collected during the first decade of permanent PT assignment to aircraft carriers. This report quantifies a 10-yr period of physical therapy services (PT and PT Technician) in providing musculoskeletal care within the carrier strike group and adds to existing literature demonstrating a high demand for musculoskeletal care in operational platforms. A collective total of 144,211 encounters were reported during the 10-yr period. The number of initial evaluations performed by the PT averaged 1,448 per assigned tour. The average number of follow-up appointments performed by the PT per tour was 1,440. The average number of treatment appointments per tour provided by the PT and PT technician combined was 1,888. The average number of visits per patient, including the initial evaluation, was 3.3. Sixty-five percent (65%) of the workload occurred while deployed or out to sea during training periods. It was estimated that 213 medical evacuations were averted over the 10-yr period. There were no reports of adverse events or quality of care reviews related to the care provided by the PT and/or PT technician. Access to early PT intervention aboard aircraft carriers was associated with a better utilization ratio (lower average number of visits per condition) than has been reported in prior studies and suggests an effective utilization of medical personnel resources. The impact of Navy PTs serving afloat highlights the importance of sustaining these billets and indicates the potential benefit of additional billet establishment to support operational platforms with high volumes of musculoskeletal injury. Access to early PT intervention can prevent and rehabilitate injuries among operational forces, promote human performance optimization, increase readiness during war and peace time efforts, and accelerate rehabilitation from neuromusculoskeletal injuries. With the establishment of Electronic Health Records within all carrier medical groups a repeat study may provide additional detail related to musculoskeletal injuries to guide medical planners to staff sea-based operational platforms most effectively to care for the greatest source of battle and disease non-battle injuries and related disability in the military.

초기 해군 항공기 개발 역사 : 우리 항공의 선구자 조경연 선생님 업적 중심으로

초기 해군 항공기 개발 역사 : 우리 항공의 선구자 조경연 선생님 업적 중심으로

Effects of Steam Ingestion on Under Fuselage Inlet Performance During a Catapult-Assisted Takeoff Process

A naval aircraft has the potential to experience inlet performance decline when taking off from the carrier deck with the steam-driven catapult assistance. The steam ingested into inlet may cause time-dependent rise and spatial distortion of the total temperature on the inlet–exit, which would decrease the compressor stall margin and then lower the performance of the turbine engine. In this paper, these temporal and spatial temperature nonuniformities are numerically studied using the dual-time-step transient method with a real aircraft/inlet model taken into account. The flowfield characteristics of a designed baseline case are first analyzed, indicating that the engine’s suction effect and the wind velocity relative to the aircraft are two key factors affecting the steam ingestion. The former is dominant at the beginning of takeoff since the aircraft's velocity is low, while the latter is increasingly significant as the aircraft accelerates. Next, parametric studies show that the greater the wind speed is, the less significantly the flowfield of the inlet–exit would be influenced by the steam. The effects are also studied among various steam leakage profiles—two are constant in time histories of the steam leakage rate, whereas the other two are nonlinear with the maximum value at different instants. It is found that the temperature rise rate of the inlet–exit would increase apparently if the steam leakage rate reaches the maximum earlier.

Using simulation to illuminate process improvement opportunities in a U.S. naval aircraft overhaul facility

Fleet Readiness Center Southwest (FRC SW) is the largest aerospace industrial complex in the U.S. Navy. The FRC SW conducts maintenance, repair and overhaul (MRO) activities on five major airframes with many of them being more than 20 years old. With demand for the aircraft in the field high, management at FRC SW were under enormous pressure to shorten the turn-around times of aircraft – the time between an aircraft being inducted for overhaul and the time it was returned to the warfighter for use in active military operations. Leadership at FRC SW requested the development of a simulation model that would incorporate all the important aspects of the complex and variable operating environment of their MRO facility and lend insight into how various factors and changes could affect the throughput time of aircraft across the facility. This research describes how the development and use of a simulation model uncovered several significant opportunities for management at FRC SW to increase turn-around time. The model also illuminated where simple policy changes could eliminate the need for additional capital investments, and where additional capital was needed the model indicated where it would yield the greatest return.

Code for unplanned encounters at sea and its practical limitations in the East and South China Seas

ABSTRACTThe Code for Unplanned Encounters at Sea [CUES 2014 Code for Unplanned Encounters at Sea (Western Pacific Naval Symposium, 22 April 2014] was finally adopted by the Western Pacific Naval Symposium in 2014. It is an important step toward improving confidence between navies. However, as a non-legally binding document with unclear geographical scope which only applies to naval vessels and aircraft, CUES 2014 is not comprehensive or potent enough, especially in the East and South China Seas where maritime disputes are unresolved and most maritime incidents involve civilian law enforcement vessels and aircraft. This article provides a geostrategic picture of the East and South China Seas, the background of the code, and analyses the practical limitations of CUES 2014 in the context of the East and South China Seas.

Dynamic Aircraft Carrier Flight Deck Task Planning based on HTN

In the operating environment of naval aircraft carrier, the move towards an increasing unmanned operational tempo with a reduced manning environment will request more automation in the planning and scheduling of aircraft, ground vehicles, and crew. This paper investigates the aircraft carrier deck operations planning problem based on Hierarchical Task Network (HTN) planning method. An HTN based dynamic operations planning process is proposed. A feasible action plan could be rapidly derived to complete a set of takeoff and landing tasks with the constraints of flight deck layout and limited resources such as catapults, elevators, and operators, etc. Corresponding to the newly generated tasks, the replanning process is triggered to cope with the changing conditions in highly dynamic environments.