• Journal of Aerospace System Engineering
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• v.16 no.4
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• pp.95-108
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• 2022

Airworthiness certification is critical, in ensuring the flight safety of military aircraft for development tests and production operations. The MIL-HDBK-516C, latest airworthiness certification document, handles the field of flying qualities in Chapter 6 (flight technology), and refers to specific chapters of MIL-STD-1797B, which is the specification document for developing military aircraft. Since the MIL-STD-1797B released in 2006 by the U.S. Department of Defense is not disclosed to other countries, the Chapter 6 (flight technology) of MIL-HDBK-516B Expanded, the former certification standards pursuant to flying qualities, has to be applied to military aircraft being developed in the Republic of Korea. However the requirements of Chapter 6 of MIL-HDBK-516B Expanded comprise unclear sentences, because of contents from various development specifications. Also, clarification is needed in that the same requirements have to be verified in different criteria. In this paper, the results of this study present an effective verification method, for acquiring the airworthiness certification in field of flying qualities based on MIL-HDBK-516B Expanded.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.1
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• pp.89-96
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• 2016

TDOA(time delay of arrival) position estimate from acoustic measurement of artillery shell impact is studied in order to develop a targeting evaluation system. Impact position is calculated from the intersections of hyperbolic estimates based on the least square Taylor series method. The mathematical process of Taylor series estimation is known to be robust. However, the concern lays with the accuracy because it is sensitive to the bias caused by the randomness of measurement situation. The measurement error typically occurs from the distortion of waveform, change of travelling path, and sensor position error. For outdoor measurement, a consideration should be made on the atmospheric condition such as temperature and wind which can possibly change the trajectories of rays of sound. It produces wrong propagation time events accordingly. Ray tracing and optimization techniques are introduced in this study to minimize the bias induced by the ray of sound. The numerical simulation shows that the atmospheric correction improves the estimation accuracy.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.115-124
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• 2018

In this study, a cold flow test was carried out on a high-speed vehicle facility with a high-altitude environment simulator. Variable test was carried out according to the blockage ratio, angle, and length of the test model. It is confirmed that the blockage rate can be operated in the range of 40%, and that the model should be selected at an angle of 45 degrees or less. The variables of length are less dominant compared to the variables of blockage rate and angle. Through this, a database is obtained according to the parameters of the conical model of the high-speed vehicle test facility.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.2
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• pp.190-205
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• 2015

In this paper, the impact damage behavior of USN-150B carbon/epoxy composite laminates subjected to high velocity impact was studied experimentally and numerically. Square composite laminates stacked with $[45/0/-45/90]_{ns}$ quasi-symmetric and $[0/90]_{ns}$ cross-ply stacking sequences and a conical shape projectile with steel core, copper skin and lead filler were considered. First high-velocity impact tests were conducted under various test conditions. Three tests were repeated under the same impact condition. Projectile velocity before and after penetration were measured by infrared ray sensors and magnetic sensors. High-speed camera shots and C-Scan images were also taken to measure the projectile velocities and to obtain the information on the damage shapes of the projectile and the laminate specimens. Next, the numerical simulation was performed using explicit finite element code LS-DYNA. Both the projectile and the composite laminate were modeled using three-dimensional solid elements. Residual velocity history of the impact projectile and the failure shape and extents of the laminates were predicted and systematically examined. The results of this study can provide the understanding on the penetration process of laminated composites during ballistic impact, as well as the damage amount and modes. These were thought to be utilized to predict the decrease of mechanical properties and also to help mitigate impact damage of composite structures.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.364-367
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• 1995

In this paper, a design method of learning flight control system via input matching is proposed. The proposed learning control system is a simple structure which has an artificial neural network and feedback mechanism, and it is a useful method to control nonlinear systems.

• Smart Structures and Systems
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• v.11 no.2
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• pp.185-197
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• 2013

We developed a simultaneous strain measurement and damage detection technique using a pair of surface-mounted piezoelectric transducers and a fiber connecting them. This is a novel sensor configuration of the fiber acoustic wave (FAW) piezoelectric transducer. In this study, lead-zirconate-titanate (PZT) transducers are installed conventionally on a plate's surface, which is a technique used in many structural health monitoring studies. However, our PZTs are also connected with an optical fiber. A FAW and Lamb wave are simultaneously guided in the optical fiber and the structure, respectively. The dependency of the time-of-flight of the FAW on the applied strain is quantified for strain sensing. In our experimental results, the FAW exhibited excellent linear behavior and no hysteresis with respect to the change in strain. On the other hand, the well-known damage detection function of the surface-mounted PZT transducers was still available by monitoring the waveform change in the conventional Lamb wave ultrasonic path.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.1
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• pp.108-117
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• 2017

This paper presents a distribution simulation model for dual purpose improved conventional munitions based on flight test data. A systematic procedure for designing a dispersion simulation model is proposed. A new accumulated broken line graph was suggested for designing the distribution shape. In the process of verification and simulation for the distribution simulation model, verification was performed by first comparing data with firing test results, and an application simulation was then conducted. The Monte Carlo method was used in the simulations, which reflected the relationship between ejection conditions and real distribution data. Before establishing the simulation algorithm, the dominant ejection parameter of the submunitions was examined. The relationships between ejection conditions and distribution results were investigated. Five key distribution parameters were analyzed with respect to the ejection conditions. They reflect the characteristics of clustered particle dynamics and aerodynamics.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.5
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• pp.700-707
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• 2017

Recently, the military need more various education and training because of the increasing necessity of various operation. But the education and training of the military has the various difficulties such as the limitations of time, space and finance etc. In order to overcome the difficulties, the military use Defense Modeling and Simulation(DM&S). Although the participants in training has the empirical knowledge from education and training based on the simulation, the empirical knowledge is not shared because of particular characteristics of military such as security and the change of official. This situation obstructs the improving effectiveness of education and training. The purpose of this research is the systematizing and analysing the empirical knowledge using text mining and network analysis to assist the sharing of empirical knowledge. For analysing texts or documents as the empirical knowledge, we select the text mining and network analysis. We expect our research will improve the effectiveness of education and training based on simulation of DM&S.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.5
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• pp.52-61
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• 2015

This paper performed a numerical study to analyse the transient performance behavior of a turbofan engine with variable inlet guide vane (IGV) and bleed air schedules. The low bypass ratio mixed flow turbofan engine was considered in this study. For modeling the compressor performance with IGV, the performance maps were generated by using a one-dimensional meanline analysis and feed to the engine simulation program. The IGV and bleed air according to the rotating speed were scheduled to satisfy 10% of surge margin at steady-state condition. The transient engine performance analysis was conducted with the schedules. The engine with IGV schedule showed a higher surge margin and lower turbine inlet temperature than the engine with bleed air schedule during the transient period.

• Journal of computational fluids engineering
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• v.17 no.4
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• pp.56-68
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• 2012

Nowadays, Unmanned Combat Air Vehicle(UCAV) has become an important aircraft system for the national defense. For its efficiency and survivability, shape optimization of UCAV is an essential part of its design process. In this paper, shape optimization of UCAV was processed for aerodynamic performance improvement and Radar Cross Section(RCS) reduction using Multi Objective Genetic Algorithm(MOGA). Lift and induced drag, friction drag, RCS were calculated using panel method, boundary layer theory, Physical Optics(PO) approximation respectively. In particular, calculation applied Radar Absorbing Material(RAM) was performed for the additional RCS reduction. Results are indicated that shape optimization is performed well for improving aerodynamic performance, reducing RCS. Further study will be performed with higher fidelity tools and consider other design segments including structure.