• 한국전산유체공학회:학술대회논문집
• /
• 2002.10a
• /
• pp.121-126
• /
• 2002

Aircraft propulsion systems often use diffusing S-duct to convey air flow from the wing or fuselage intake to the engine compressor, Well designed S-duct should incur minimal total pressure losses and deliver nearly uniform flow with small transverse velocity components at the engine compressor entrance. Reduced total pressure recovery lowers propulsion efficiency and nonuniform flow conditions at the engine face lower engine stall limits. In this study, S-duct which has maximum total pressure recovery and nearly uniform flow profiles at the compressure intake should be found using design optimization methods with 3-dimensional Wavier-Stokes analyses.

• Journal of Aerospace System Engineering
• /
• v.8 no.4
• /
• pp.7-17
• /
• 2014

Objective of this paper is to introduce a new technology known as prognostics and health management (PHM) which enables a real-time life prediction for safety critical systems under extreme loading conditions. In the PHM, Bayesian framework is employed to account for uncertainties and probabilities arising in the overall process including condition monitoring, fault severity estimation and failure predictions. Three applications - aircraft fuselage crack, gearbox spall and battery capacity degradation are taken to illustrate the approach, in which the life is predicted and validated by end-of-life results. The PHM technology may allow new maintenance strategy that achieves higher degree of safety while reducing the cost in effective manner.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.18 no.4
• /
• pp.343-349
• /
• 2015

This is a study for the improvement of the fractured lug structure that connects the landing gear to the fuselage of the aircraft using the composite leaf spring landing gear. The lug surface was analyzed to find out the cause of fracture. The lug was destroyed by the crack initiation and propagation under the repeated stresses. The frictional wears of the lug structure were proceeded and that affected adversely to the crack. Also, the square protrusion of the lug has a weak shape to bring about stress concentration. The design changes were conducted and the test was performed to verify changed design results.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.6
• /
• pp.490-497
• /
• 2017

The Main Landing Gear(MLG) of Rotary Wing Aircraft is an essential equipment in Landing System for pilot to perform a flight mission. It supports the fuselage at ground and absorbs the impact from the ground when landing, thereby, these functions sustain operational capability for pilot and crew. However, the A aircraft caused asymmetry and leakage hydraulic when it was stationed on the ground. Therefore, this paper summarizes pilot comments in operation which are classified by cause of occurrence and the troubleshooting process about each comment. It also describes design improvements which was derived from troubleshooting and suggests verification results of flight test.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.8
• /
• pp.766-773
• /
• 2016

This paper proposes an aircraft-installed compact offset-parabolic-reflector antenna for the spinning direction-finding applications. The feeder of the reflector antenna is a LPDA antenna that has the ultra-wideband characteristics and the $45^{\circ}$ slant linear polarization. The reflector is designed to be slanted by $5^{\circ}$ in the elevation and to be small in size on the basis of the reference parabolic shape for the purpose of the high gain and mounting on the underside of aircraft fuselage. Over the ultra-wideband 20:1 bandwidth from S to Ka band, the measured average gain of the proposed antenna is 27.97 dBi, and the average half-power beam width is $4.55^{\circ}$ in the azimuth and $4.3^{\circ}$ in the elevation which is the pencil-beam radiation pattern. All the measured data are similar to the simulation results. The designed compact offset-parabolic-reflector antenna that is installed in the limited area has the ultra-wideband and high-gain characteristics. We expect that the newly designed antenna can be applied to the spinning direction-finding antenna system installed in an aircraft.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.7
• /
• pp.527-534
• /
• 2018

The endurance of the multi-copter is one of the important variables that determine the mission performance. Therefore, accurate endurance should be defined as essential for performing effective missions. In this paper, we present the results of the study on the flight performance of the aircraft, especially the hovering of the drone(multi-copter). Unlike conventional aircraft, which consider aerodynamic performance by the fuselage, the multi-copter is mostly determined by the propulsion system. Therefore, the research method classifies the various parts constituting the drone system into functions, analyzes the performance of the unit parts and obtains the experimental data by sorting out the specifications and functions at the component level and mathematical formulation, The results of this study are as follows. In addition, the 5kg class quad copter was used to predict and verify the voltage change with endurance through analysis of in situ flight. By predicting endurance under various conditions, it can help design/build the right Multi-copter for mission.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.12
• /
• pp.92-100
• /
• 2005

An aircraft wing or fuselage panel of skin-stringer assembly can fail in a variety of instable modes under compression loads. Instability modes can be buckling of the panel, local buckling of the stringer, flexure, torsion, wrinkle and combined flexural/torsional buckling of the panel assembly. Although researches on these buckling behaviors have been carried out for a long time, there are some difficulties to apply to the practice because of complex theoretical and empirical equations. Accordingly, It is well known that leading aerospace companies are using their own in-house programs for the convenience of practical usage, but our domestic situation is that no such program has been ever developed. In this study a comprehensive program has been developed, which can identify the instability modes and the magnitude of reserve factor of the modes for the skin/stringer panel assembly under compression load. The developed program is based on the theory manual of the Airbus program APA114. For the verification, calculation of the instable reserve factors for the A320 wing panel and A380 low wing panel sections were carried out and compared with results by APA114.

• Aerospace Engineering and Technology
• /
• v.11 no.2
• /
• pp.65-72
• /
• 2012

Numerical simulations were performed to study the stall characteristics of turboprop aircraft. Stall characteristics were qualitatively investigated using the computational results of various configurations based on the combinations of propeller and high lift device. For the analysis of stall characteristics, three-dimensional Navier-Stokes solver with Spalart-Allmaras turbulence model was used and the relative motion between propeller and wing was simulated using sliding mesh technique. For the cruise configurations, major flow separation was occurred at the fuselage/wing fairing and the separation was reduced under propeller slipstream condition. For the high lift device configuration without propeller, major flow separation was occurred at the outboard side of nacelle. With rotating propeller, early stall onset due to low relative velocity and high effective angle of attack was observed on the outboard wing section. Regarding rotating direction of propeller, inboard-down direction was preferred due to the stall delay effect of propeller slipstream.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.7
• /
• pp.531-538
• /
• 2017

A flush air data sensing system, which can predict flight speed, angle of attack, and angle of sideslip of the aircraft is designed and manufactured for a small UAV. Two kinds of flush pressure ports, four ports and five ports, are tapped at the same section of fuselage nose-cone. Calibration pressure data at flush ports are obtained through computations for the total aircraft by using Fluent code. Angle of attack, angle of sideslip, total pressure, and static pressure are represented with 4th-order polynomial function and calibration coefficient matrix is obtained using least square method with calibration pressure data. Flight test showed that flight speed, angle of attack, and sideslip angle predicted by four flush ports and five flush ports compared well with those by five-hole probe installed for data comparison. Especially four flush ports revealed nearly same results as those by five flush ports.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.8
• /
• pp.889-895
• /
• 2012

Carbon fiber reinforced plastic (CFRP) composites have high specific stiffness and high specific strength. Therefore, they are increasingly being use, instead of conventional metallic materials in the aviation and automobile industries, where there is a strong demand for lightweight materials. In aircraft, the fuselage is exposed to severe conditions of high temperatures and high humidity. Therefore, it is necessary to estimate the strength of CFRP composites under real conditions from the viewpoint of aircraft safety. In this study, CFRP specimens were immersed in distilled water at $75^{\circ}C$ for a long time. Then, tensile tests were performed on these specimens, and the fracture characteristics of the fractured surfaces were analyzed using SEM. A fatigue test was performed on specimens immersed for 300 days with R=0.1, and it was confirmed that the fatigue life deteriorated in immersed specimens compared to specimens that were not immersed.