• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.5
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• pp.50-56
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• 2005

The objective of this study is to find the optimal thrust condition and wing loading of a vertical take-off and landing (VTOL) fixed-wing aircraft through a single engine failure analysis during landing approach and an analysis of transition flight. The aircraft analysis modules used in the study are based on the aircraft synthesis program. To achieve the computing infrastructure for aircraft design and analysis, the EMDIOS was employed as a design framework, which is a semi-completed application program and ready to customize. Simulation results reveal the most critical height at the event of single engine failure is approximately 40 ft. And, in order to avoid a significant loss in altitude during the transition, the thrust to weight ratio must be kept high, while both the engine tilt speed and the wing loading must be kept low, as confirmed by the analysis results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.12
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• pp.1011-1018
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• 2021

This numerical study conducts the modeling and the hover performance analyses of coaxial co-rotating rotor(or stacked rotor), using a rotorcraft comprehensive analysis code, CAMRAD II. The important design parameters such as the index angle and axial spacing for the coaxial co-rotating rotor are varied in this simulation study. The coaxial co-rotating rotor is trimmed using the torque value of the upper rotor of the previous coaxial counter-rotating rotor or the total thrust value of the previous coaxial counter-rotating rotor in hover. The maximum increases in the rotor thrust is 1.84% for the index angle of -10° when using the torque trim approach. In addition, the maximum decreases in the rotor power is 4.53% for the index angle of 20° with the thrust trim method. Thus, the present study shows that the hover performance of the coaxial co-rotating rotor for e-VTOL aircraft can be changed by the index angle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.299-302
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• 2008

A unified numerical analysis including combustion was conducted in order to study on performance of ramjet propulsion. The geometry of concern includes the entire flow path of a ramjet extending from intake to exhaust nozzle. Acceleration mode and cruise mode were considered in several equivalence ratios. Pressure distributions, terminal shock train range at the intake, temperature distributions in the combustors, and fuel mass fraction at the nozzle exit were investigated for each flight mode.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.89-96
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• 2005

This study has been performed on the mechanism of heat transfer between stratospheric airship and its surroundings while the airship is staying in the air at the altitude of 20km. The computational grid of airship has been generated and the results influenced by the number and the shape of grids have been compared. The temperature distributions have been obtained through this thermal analysis considering three modes of heat transfer - conduction, convection and radiation - in stratospheric conditions. Based on the airship's surface and inner temperature variations, the influence of temperature distributions on the helium envelope and the payload has been predicted.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.35-39
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• 1993

항공기의 플러터 현상을 예방키 위한 개발시의 주요 공학적 임무로는 플러 터 해석, 풍동 플러터 시험, 실기체에 대한 지상진동시험 및 비행 플러터 시 험이 있다. 이들 업무는 군용 항공기의 경우에는 군사 규격서, 민간 항공기 의 경우는 FAR 규정 등에 항공기 개발 및 개조시에는 필히 수행토록 명시 되어 있으며, 특히 개발항공기의 인증을 받기 위해서는 초도 비행전까지 필 수적으로 완료되어야 하는 업무이다. 이중 항공기 지상진동시험은 개발항공 기의 초도 비행전에 실기체를 대상으로 하는 구조 동특성 규명시험으로써 플러터 해석 모델의 정확도를 입증하고 그 해석모델을 수정하거나 개선시키 는데 필요한 구조의 동특성 변수들을 실험적으로 규명하는 시험이다. 이 시 험은 개발된 항공기의 초도비행허가를 획득하고 비행속도제한을 설정키 위 해서 초도비행 직전에 초도 개발 비행기를 대상으로 필수적으로 수행되어야 하는 필수적 시험이다. 이에 따라 개발된 항공기의 전기체 지상진동시험을 수행하였고, 시험데이터의 모달해석을 하였다. 이 시험을 수행하기 위해 3개 의 가진기를 사용하였고, 모두 159개의 지점에서 주파수응답 함수를 얻었다. 최대 48 채널의 데이터 획득시스템을 사용하였으므로, 네번에 걸쳐 측정위치 를 옮겨 전체데이타를 획득하였다. 지상진동 시험의 최종해석 결과는 유한요 소 모델의 유효성을 검토하는데 사용되었고, 시험 데이타를 이용한 가진응답 해석(Forced Response Analysis)을 통하여 비행플러터 시험시에 사용되는 플러터 가진기의 위치선정 및 가진력의 크기를 결정하는데 이용하였다.ncy)가 저주 파수대로 천이(Lower Shift)하는 현상이 나타났으며, 일정한 작업량이라도 작업중량을 줄이고 작업 빈도를 높여서 작업할 경우에 이러한 현상이 더욱 두드러졌다. 작업시간의 경과에 따른 MVIS의 감소 현상은 작업빈도가 높고 비대칭형 작업일 때 가장 크게 나타났다. 총손실을 줄이고, 상대적 비용절감효과를 갖게할 수 있다고 하였다. 따라서 본 연구에서는 성인 여성기성복의 치수적합성을 높이기위하여 출산 후 중년에 접어 들면서 체형이 변화되는 것을 고려하여 연령을 분류하고(18세-34세, 30세-51세), 각 연령 집단에 따른 체형을 각각 3가지로 분류하였다. 이에 따라 의복 생산시의 총손실을 줄이기위한 상의, 하의생산시 필요한 부위별 최적규격치 간격을 제시하였다.적인 기능으로 보여지는 것에 좁혀서 작업능력의 연령증가 변화에 대하여다원적 평가를 하는 것이 실제적이라고 할 수 있다. 따라서 본 연구에서는 인간이 가지고 있는 다수의 기능중에서 수지교 치성과 연령증가와의 관계를 조사한다. 만약 연령증가 만으로 수지교치성을 평가 할 수 없는 경우에는 어떠한 요인이 수지기민성의 변화에 영향을 미치는가를 검토한다.t list)에서 자동적으로 사건들의 순서가 결정되도록 확장하였으며, 설비 제어방식에 있어서도 FIFO, LIFO, 우선 순위 방식등을 선택할 수 있도록 확장하였다. SIMPLE는 자료구조 및 프로그램이 공개되어 있으므로 프로그래머가 원하는 기능을 쉽게 추가할 수 있는 장점도 있다. 아울러 SMPLE에서 새로이 추가된 자료구조와 함수 및 설비제어 방식등을 활용하여 실제 중형급 시스

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.8-16
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• 2003

Aerodynamic characteristics over Micro Aerial Vehicle(MAV) in low Reynolds number regime are numerically studied using 3-D unsteady, incompressible Navier-Stokes flow solver with single partitioning method for multi-block grid. For more efficient computation of unsteady flows, this flow solver is parallel-implemented with MPl(Message Passing Interface) programming method. Firstly, MAV wing with not complex geometry is considered and then, we analyze aerodynamic characteristics over full MAV configuration varying the angle of attack. Present computational results show a better agreement with the experimental data by MACDL(Micro Aerodynamic Control and Design Lab.), Seoul National University. We can also find the conceptually designed MAV by MACDL has the static stability.

• Journal of Aerospace System Engineering
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• v.18 no.3
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• pp.76-85
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• 2024

Recently, from a global perspective, the use of small unmanned aerial vehicles in terrorism and warfare is increasing, and the need for anti-drone shooting training targeting small UAVs is increasing. However, in reality, there are many cases in Korea where anti-drone shooting training is restricted, due to complaints such as noise. In this paper, we describe the development and testing of an electric-powered direct strike type high-speed, low-noise small aerial target drone. To achieve the flight speed and endurance required for shooting training, target drone sizing was performed, and aerodynamic performance analysis was conducted using a CFD program. Based on the performance analysis, the motor propulsion system was selected and a variable pitch propeller system was designed, and performance tests were performed on a ground test rig. Finally, the target flight speed, flight time, and flight noise level were confirmed through flight tests.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.519-526
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• 2009

This paper describes a research result of a external shape optimization study to maximize the range of the guided missile with canards and tailfins in atmospheric flight. For this purpose, the external shape optimization program which can enhance the range of a missile was developed, incorporated with the trajectory analysis and the optimization technique. In the trajectory analysis part, Missile DATCOM which utilizes the semi-empirical method was directly connected to the trajectory code to supply the aerodynamic coefficients efficiently at every time step. In the gliding flight trajectory after apogee, a maximum $C_L/C_D$ trim condition calculation module was attached under the assumption of the missile continuously flying at maximum $C_L/C_D$ condition. In the optimization part, a Response Surface Method(RSM) was adopted to reduce the computing time.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.4
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• pp.91-99
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• 2005

Flight compatibility certification is performed to substantiate the compatibility between ALQ-X ECM pod and KF-16D/RF-4C aircraft. A certification plan for the ALQ-X flight compatibility is established. Similarity analysis, mass/inertia analysis, structural analysis/test, and ground vibration test/flutter analysis are made to support the safety of MIL-HDBK-1763 Test 250 (Captive compatibility flight profile). Aircraft flew along flight envelope boundary with representative ALQ-X configurations. Handling qualities are evaluated by comparing flight characteristics of the aircraft with and without ALQ-X. Structural integrity and endurance is evaluated using measured flight test data. Results of these flight tests showed that ALQ-X is compatible with KF-16D/RF-4C without altering the flight envelope which has originally been certified for ALQ-88 and ALQ-119 ECM pods. ALQ-X certification program made following technical achievements: Type III certification for foreign designed fighter, flutter analysis program development using GVT results, and utilization of MIL-STD-1553B data bus in flight test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.9
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• pp.796-805
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• 2016

As a part of the first stage in the helicopter flight simulator development, this study numerically evaluates handling qualities of the dynamics model. The flight dynamics model was generated using public information for AS365 N2, the target aircraft of the simulator. The flight simulator is under development as a pilot training and research tool for firefighting missions. The assessment of the model intends to validate general characteristics and suitability before the model is enhanced with flight test data. The evaluation is based on the ADS-33E-PRF(Aeroautical Design Standard Performance Specification Handling Qualities Requirement) criteria, with consideration of category of the aircraft, missions, and environment. The numerical operations follow required or recommended procedures of flight test for compliance demonstration. Evaluation results are evaluated according to the rating specified in maneuverability ADS-33E-PRF. Results have identified to provide a satisfactory platform for flight dynamic model in the general helicopter simulator generated based on the RotorLibFDM, and can be used as a base for basic training and research.