• Journal of the Korean Society for Aviation and Aeronautics
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• v.32 no.2
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• pp.135-141
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• 2024

Despite the innovative technological advances in the aviation industry, hard landing events that occur during aircraft landing account for 13% of all accidents. Hard landing when landing an aircraft affects normal operation by generating a large load on the landing gear and the fuselage. In order to identify these risk factors, the airline monitors the high vertical acceleration event, a precursor to hard landing, through QAR (Quick Access Recorder) flight data analysis, and prepares and implements mitigation measures. In this study, it is intended to contribute to safety management based on flight data analysis that identifies the characteristics of high vertical acceleration G event data that can cause such hard landing and detailed parameters of precursor signs, and to identify the causal relationship of the occurrence of the event by applying statistical analysis methods such as variance analysis, correlation analysis, and regression analysis models to identify the characteristics of the event occurrence and eliminate the cause in advance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.11
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• pp.971-977
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• 2015

A numerical analysis for the performance of compound gyroplane in forward flight was performed. TSM(Transient Simulation Method) was used to analyze the performance of autorotating rotor. CFD was conducted for the fuselages to recognize the variation of aerodynamic performance according to flight speed. At given conditions; airspeed, shaft angle and collective pitch, the quasi-static states of autorotation were determined and the variation of rotor performance was observed. Performance analysis results showed that the effect of aerodynamic characteristics in accordance with the shape of fuselage is so important that the streamlined fuselage is essential to fly fast. Forward flight speed limit is dependent on the autorotation performance of rotor.

• Advances in aircraft and spacecraft science
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• v.3 no.3
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• pp.271-298
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• 2016

In this paper, we study a problem of passive suppression of helicopter Ground Resonance (GR) using a single degree freedom Nonlinear Energy Sink (NES), GR is a dynamic instability involving the coupling of the blades motion in the rotational plane (i.e. the lag motion) and the helicopter fuselage motion. A reduced linear system reproducing GR instability is used. It is obtained using successively Coleman transformation and binormal transformation. The analysis of the steadystate responses of this model is performed when a NES is attached on the helicopter fuselage. The NES involves an essential cubic restoring force and a linear damping force. The analysis is achieved applying complexification-averaging method. The resulting slow-flow model is finally analyzed using multiple scale approach. Four steady-state responses corresponding to complete suppression, partial suppression through strongly modulated response, partial suppression through periodic response and no suppression of the GR are highlighted. An algorithm based on simple criterions is developed to predict these steady-state response regimes. Numerical simulations of the complete system confirm this analysis of the slow-flow dynamics. A parametric analysis of the influence of the NES damping coefficient and the rotor speed on the response regime is finally proposed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.12 s.117
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• pp.1252-1261
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• 2006

This paper summarizes theoretical work on the multichannel decentralized feedback control of sound radiation from aircraft trim panels using piezoceramic actuators. The aircraft trim panels are generally honeycomb structures designed to meet the design requirement of low weight and high stiffness. They are resiliently-mounted to the fuselage for the passive reduction of noise transmission. It is motivated by the localization of reduction in vibration of single channel active trim panels. 12-channel decentralized feedback control systems are investigated in terms of the reduction of noise and vibration for three configurations of sensor actuator pairs. Local coupling of the closely-spaced sensor and actuator pairs was modeled using single degree of freedom systems. The multichannel control system is characterized using the state-space model. For the stability point of view, the relative stability or robustness is evaluated by comparing the real part of eigenvalues of the system matrix for the three configurations. The control performance is also evaluated and compared for the three configurations. It is found that the multichannel system can lead to the globalization of the reduction in vibration and radiated noise. It does not appear to yield a significant improvement in the vibration because of decreased gain margin. However, the reduction in the radiated noise is remarkably improved due to the variation of the vibration pattern with the actuation configurations.

• Journal of Aerospace System Engineering
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• v.12 no.5
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• pp.24-31
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• 2018

The objectives of this study is to carry out Bird strike analysis and tests of a blade antenna of aircraft. FEMs (Finite Element Models) were created for the analysis, while dummy and real antennas were used for the bird strike tests. In the analysis, birds were modeled with SPH (Smooth Particle Hydrodynamics) method, and the behaviors of the bird, antenna, and joint structure between antenna and aircraft fuselage were simulated with the FSI (Fluid-Structure Interaction) method. After the bird strike test was performed, the results of the analysis and test showed that they had a positive relationship. The damage of antenna and bolted joint was checked, and the structural integrity of the airframe was proved.

• Advances in aircraft and spacecraft science
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• v.5 no.3
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• pp.319-334
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• 2018

In this study, the failure mode and energy absorption capabilities of a composite shock absorber device, during an emergency landing are evaluated. The prototype has been installed and tested in laboratory simulating an emergency landing test condition. The crash absorber presents an innovative configuration able to reduce the loads transmitted to a helicopter fuselage during an emergency landing. It consists of a composite tailored tube installed on the landing gear strut. During an emergency landing this crash absorber system should be able to absorb energy through a pre-designed deformation. This solution, compared to an oleo-pneumatic shock absorber, avoids sealing checks, very high values of the shock absorber pressure, and results to be lighter, easy in maintenance, inspect and use. The activities reported in this paper have become an attractive research field both from the scientific viewpoint and the prospect of industrial applications, because they offer benefits in terms of energy absorbing, weight savings, increasing the safety levels, and finally reducing the costs in a global sense.

• Advances in aircraft and spacecraft science
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• v.10 no.2
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• pp.141-158
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• 2023

In current research work, the aerodynamics performance of a newly designed large flying V aircraft is numerically investigated. Three Flying V configurations, with V-angles of 50°, 70° and 90° that represent the minimum, moderate, and maximum configurations respectively, were designed and modeled to assess their aerodynamic performance at cruise flight conditions. The unstructured mesh was developed using ICEM CFD and Ansys-Fluent was used as an aerodynamic solver. The developed models were numerically simulated at cruise flight conditions with a Mach number equal to 0.15. K-ω SST turbulence model was chosen to account for flow turbulence.The authors performed steady flow simulations.The results obtained from the experimentation reveal that the maximum main angle configuration of 90° had the highest C_Lmax value of 0.46 compared to other configurations. While the drag coefficient remained the same for all three configurations, the 50° V-angle configuration achieved the maximum stall angle of 35°. With limited stall delay benefits, the flying V possesses no sufficient stability, due to the flow separation detected at whole elevon and winglet suction side areas at AoA equal and higher than 30°.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.7
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• pp.507-514
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• 2022

The EO/IR targeting pod mounted on a fighter to acquire information about tactical targets is typically mounted and operated at the bottom of the aircraft fuselage. Since the aircraft equipped with such an external attachment has complexed aerodynamic and inertial characteristics compared to the aircraft flying without an external attachment, a method of system performance analyses is required to identify development risk factors in the early stages of development and reflect them in the design. In this study, a development plan was presented to provide the necessary modeling and simulation tools to develop a pod that can acquire measurement data stably in a highly maneuverable environment. The limiting operating conditions of the pods mounted on the highly maneuverable aircraft were derived, the aerodynamics and inertial loads of the mounted pods were analyzed according to the limiting operating conditions, and a flight data generation and transmission system were developed by simulating the mission of the aircraft equipped with the mounted pods.

• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.2
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• pp.42-51
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• 2001

The effects of pre-indentation technique are presented for A12024-T3 Alclad alloy using as skin material for aircraft fuselage and wing. Indentations were applied to specimens to be placed on the presumed path of fatigue crack growth before fatigue tests. Tension-tension fatigue tests were conducted on the edge cracked specimens in the L-T orientation. Test results were analyzed to investigate the effectiveness of pre-indentation with the variation of specimen's thickness, position of indentation and applied maximum stress. Fatigue crack retardation by pre-indentation is well recognized in the various conditions.

• Journal of Aerospace System Engineering
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• v.5 no.1
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• pp.7-12
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• 2011

The goal of fire prevention research is to eliminate fires as a cause of fatal accidents and there are two main areas of research. One is to prevent flame propagation during in-flight and it addresses fire hazards. The other is to minimize the possibility of flame penetration or fuselage burn-through and it aims toward post-crash survival include crash protection, emergency evacuation and post-evacuation survival. Civil aviation authorities world-wide are trying to identify threats and measure performance for fire prevention. The results of research are standardized and given as general directions of test methods. This paper has prepared to study and present the means of compliance to the fire prevention requirements and applicable test methods.