• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.4
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• pp.55-62
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• 2020

Special airworthiness certificates can be issued if the aircraft does not meet the airworthiness standards, but it is deemed that it can be operated safely by partially limiting the scope of operation and flight performance. Currently, Korea is subject to experimental special certification for UAS(Unmanned Aircraft Systems) exceeding 150 kg of its own weight, but detailed guidelines need to be prepared on how to prove that they can be operated safely in a limited range. Recently, Korea Airworthiness Standard(KAS) Part 21 has been revised to reflect this, but it needs to be supplemented. In this study, through an understanding and analysis of the FAA's procedure of expeirmental special airworthiness certifications for UAS, we would like to suggest what we should consider when developing relevant guidelines in our country.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.25 no.2
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• pp.18-24
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• 2017

Results of the experimental research are described in this thesis, which are about braking characteristics of aircraft ABS brake system with different ground conditions. Dynamo-tests were conducted with the state of the application aircraft condition and with two different ground conditions. The Braking characteristics on each ground condition were drawn from the results of occurrence of skid, braking distance and deceleration. The braking performance of the application aircraft could be anticipated and the efficient range of braking operation could be set with those results.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.21 no.4
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• pp.41-46
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• 2013

This paper deals with an experimental technique for the measurement of dynamic stability derivatives in the roll motion of aircraft. Experimental aquisition method for aircraft's dynamic stability derivatives is conducted on the oscillation condition of aircraft model in the subsonic wind tunnel. The oscillation of aircraft model was forced by the oscillation apparatus. The forced oscillation technique is the method getting data from the internal balance inserted into the aircraft model during oscillating it. Dynamic stability derivatives of rolling motion were calculated by data reduction from the measurements of rolling moment, frequency and amplitude of aircraft model due to forced oscillation under wind conditions. Results of experiment is obtained similar one with those of roll dynamic stability derivatives measured in other institutes.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.671-679
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• 2008

The effect of Pre-cooled Turbojet Engine installation and nozzle exhaust jet on Hypersonic Turbojet EXperimental aircraft(HYTEX aircraft) were investigated by three-dimensional numerical analyses to obtain aerodynamic characteristics of the aircraft during its in-flight condition. First, simulations of wind tunnel experiment using small scale model of the aircraft with and without the rectangular duct reproducing engine was performed at M=5.1 condition in order to validate the calculation code. Here, good agreements with experimental data were obtained regarding centerline wall pressures on the aircraft and aerodynamic coefficients of forces and moments acting on the aircraft. Next, full scale integrated analysis of the aircraft and the engine were conducted for flight Mach numbers of M=5.0, 4.0, 3.5, 3.0, and 2.0. Increasing the angle of attack $\alpha$ of the aircraft in M=5.0 flight increased the mass flow rate of the air captured at the intake due to pre-compression effect of the nose shockwave, also increasing the thrust obtained at the engine plug nozzle. Sufficient thrust for acceleration were obtained at $\alpha=3$ and 5 degrees. Increase of flight Mach number at $\alpha=0$ degrees resulted in decrease of mass flow rate captured at the engine intake, and thus decrease in thrust at the nozzle. The thrust was sufficient for acceleration at M=3.5 and lower cases. Lift force on the aircraft was increased by the integration of engine on the aircraft for all varying angles of attack or flight Mach numbers. However, the slope of lift increase when increasing flight Mach number showed decrease as flight Mach number reach to M=5.0, due to the separation shockwave at the upper surface of the aircraft. Pitch moment of the aircraft was not affected by the installation of the engines for all angles of attack at M=5.0 condition. In low Mach number cases at $\alpha=0$ degrees, installation of the engines increased the pitch moment compared to no engine configuration. Installation of the engines increased the frictional drag on the aircraft, and its percentage to the total drag ranged between 30-50% for varying angle of attack in M=5.0 flight.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.754-757
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• 2005

Aircraft noise is the serious problem for inhabitants near an air force base. Noise by ground test of aircraft, however, can be minimized through test room construction. In this study, environmental effects of the noise by aircraft ground test were investigated by experiments under the standard act and by performance, prediction of the Hush house, constructed for the noise reduction.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.185-187
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• 2018

This paper presents an aircraft detection on panchromatic image using densely connected convolutional network. This algorithm connects all preceding feature-maps to all subsequent layers. It is encouraged to reuse feature-maps and enhance feature-maps representation. This algorithm is driven to learn aircraft feature to detect aircraft objects on panchromatic imagery. Based on the experimental result, it can yield accuracy of 92%.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.4
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• pp.38-43
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• 2010

A continuing challenge in the aviation industry is how to safely keep aircraft in service longer with limited maintenance budgets. Therefore, all the advanced countries in aircraft technologies put great efforts in prediction of failure rate in parts and system, but in the domestic aircraft industry is lack of theoretical and experimental research. Prediction of failure rate provides a rational basis for design decisions such as the choice of part quality levels and derating factors to be applied. For these reasons, analytic prediction of failure rate is essential process in developing aircraft structure. In this paper, a procedure for prediction of failure rate for aircraft structural parts is presented. Cargo door kinematic parts are taken to illustrate the process, in which the failure rate for Hook part is computed by using Monte Carlo Simulation along with Response Surface Model, and system failure rate is obtained afterwards.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.1
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• pp.12-19
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• 2022

The exhaust wake of an aircraft engine is discharged in a high temperature and high speed, which can damage objects such as an aircraft in the rear. The exhaust wake can lift small foreign substances lying on the ground or falling off, and the floating foreign substances can enter the intake duct of the aircraft moving from the rear and cause engine FOD (Foreign Object Damage). This study experimentally analyzed how the engine exhaust wake generated from military jet fighters affects the movement of foreign substances and evaluated the effects of foreign substances on the damaged area by measuring wake velocity. The simulation and field experimental results confirmed that the effect of exhaust wake increases as the rear position closer, and that foreign substances lifted by the wake can act as FOD to the adjacent rear aircraft.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.3
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• pp.397-404
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• 2011

The aerodynamic characteristics of a separated captive body in flow field around aircraft are studied to observe aerodynamic stability for safe separation from aircraft. Since the captive body separated from aircraft is initially exposed to unsteady flow pattern, the change of aerodynamic forces and moments should be measured to analyze how the flow pattern affects on the captive body at the vicinity of aircraft. Aerodynamic forces and moments of the separated captive body are measured at selected positions along predictable dropping trajectories. The measuring trajectories, generated by the free drop test of the dropping model in the wind tunnel, are consisted of 9 possible lines by free dropped trajectories. Experimental results show that the aerodynamic forces and moments are significantly varied with the distance between the captive body and aircraft. In conclusion, the change of aerodynamic characteristics within flow field around aircraft should be considered to simulate trajectories of the separated captive body from aircraft.

• Journal of Aerospace System Engineering
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• v.9 no.3
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• pp.23-30
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• 2015

In this study, a transient structural load analysis system was constructed to calculate the applied load on the suspension equipment corresponding to the aircraft flight conditions based on military specifications. Aircraft flight data (altitude, velocity, acceleration, angle of attack and etc. at aircraft center of gravity) were used as input parameters and the calculated load of the suspension equipment at wings on the left and right side was printed out for the structural load analysis. As a calculation procedure, first of all, load analysis was carried out at the center of gravity of the external store, Secondly, a trial reaction force analysis was conducted on hook and swaybrace of suspension equipment. All procedure of calculations was programed to analyze the structural load automatically. To verify the numerical results, structural load analysis using the experimental flight data was performed.