• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.7
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• pp.642-652
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• 2009

Most of lap jointed aircraft structures encounter the fretting damages, which provoke fretting cracks prematurely and lead to significant reduction of fatigue life. In the case of ageing aircrafts especially, this fretting fatigue problem is a fatal threat for the safety and airworthiness. Recently, as the service life extension program(SLEP) of ageing aircrafts has become a hot issue, the prediction of fretting fatigue life is also indispensable. On these backgrounds, a series of experimental tests of fretting fatigue on bolted lap joint specimens, were performed. And the fretting crack initiation and propagation life of each specimen were evaluated using existing and newly proposed prediction models with the fretting parameters obtained from the FEA results for elasto-plastic contact stress analyses. The validations of prediction models were also discussed, comparing the prediction results with experimental test ones.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.11
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• pp.80-87
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• 2005

T-50 supersonic jet trainer aircraft using digital flight-by-wire flight control system receives aircraft flight conditions such as altitude, VCAS(Calibrated Airspeed) and Angle of Attack from IMFP(Integrated Multi-Function Probe). IMFP sensors information have triplex structure using three IMFP sensors. Air-data selection logic is mid-value selection in three information from three IMFP sensors in order to have more reliability. From supersonic flight test at high altitude, air-data information is dropped simultaneously because of supersonic shock wave effect. This error information may affect to aircraft stability and safety in supersonic area at low altitude. This paper propose that sensitivity analysis and HQS(Handling Quality Simulator) pilot simulation in order to analyze flight stability and controllability in supersonic area at low altitude when these information is applied to flight control law.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.102-109
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• 2003

The number of engines for fighters has been decided by thrust required and available engines at the time since the beginning of the jet age. However, many factors such as combat effectiveness, survivability, performance, and cost were considered as engine technology has been progressed. From the vietnam war and desert storm, a twin engine fighter was shown slight superiority to a single engine one in an vulnerability，but single engine fighters were a little predominant in susceptibility This paper includes the trade-off study results on the number of engines for the supersonic light attack aircraft with single and twin engines. Twin engine configuration is 8%, 26%, and 13% higher than single engine one in MTOGW, Flyaway Cost, and LCC respectively. Little difference has been found in RM&S, Maneuver and field performance. According to the factors above, single engine fighter is profitable for low class and twin engine one for medium and higher class.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.117-125
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• 2004

This paper describes the test technique for the full-scale airframe durability test according to the military handbook(MIL-HDBK-1530) and ASIP(Aircraft Structure Integrity Program) to evaluate structural integrity and to obtain basic data for IPA(Initial Production Approval) of the Korean advanced trainer(T-50). This paper covers the full-scale airframe floating setup technique, the optimized test load simulation method, test rig design technique, test setup design and installation techniques, test safety device design and operation technique, and durability test results. As 1st life durability test was successfully performed, it was confirmed that this method is available in a full-scale airframe structural test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.2
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• pp.149-156
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• 2007

The present study provides structural design and analysis of main wing and horizontal tail of a small scale WIG(Wing in Ground Effect) vehicle which has been developed as a part of the high speed maritime transportation system for the future of Korea. Weight saving as well as structural stability could be achieved by skin-spar with foam sandwich design and with wide application of carbon/epoxy composite material. A commercial FEM code, NASTRAN, was utilized to confirm the structural safety and stability through sequential design modifications to meet the final design goal. In addition, each wing and the fuselage were fastened together by eight insert bolts with high strength to accomodate easy assembling and disassembling as well as to guarantee a service life longer than 20 years.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.618-626
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• 2011

In order to complete missions in a complicated terrain or highly dangerous area, an unmanned aerial vehicle(UAV) needs a fine controller to precisely follow the desired path. A PID controller used for the path following feeds forward path curvature information to the control input to improve the path following performance. High gain for PID controller is necessary to follow path tightly. However the high gain could cause instability or performance degradation when the vehicle has slow dynamics. We present PID controller design method which considers response delay of vehicle as well as path curvature. In order to obtain path curvature the desired path is described as a 3rd order polynomial by applying cubic spline interpolation. We apply the proposed controller to the path following of a UAV which is operated in high altitude and has very slow lateral dynamics. The lateral dynamics are modelled as a first order delayed system in the controller design. Nonlinear simulation shows the UAV with proposed controller follows an arbitrary path very tightly.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.10
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• pp.821-829
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• 2020

Health management system of airborne software repairs runtime errors to provide safety and to reduce cost of maintenance. It is critical to on-the-fly repair order violation errors, because it is difficult to identify them at the development phase. Previous work, called Repairing Atomicity Violations (Repairing-AV) diagnoses order violations for each access event by comparing execution order of accesses. As a result, Repairing-AV has time overhead that is proportional to the number of access events to shared variable. This paper presents a tool called On-the-fly Repairing System (ORS) that can repair order violations of object methods containing access events. The ORS diagnoses order violations by using correct order of object methods, and treats them by stalling its thread where the error is about to occur. Experimentation with five synthetic programs shows that ORS is more efficient than Repairing-AV when the number of access events is greater than sixty.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.5
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• pp.127-133
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• 2002

The general requirements to achieve the structural integrity of the airframe are described in the military specification, MIL-STD-1530A. One of these requirements is the durability and damage tolerance of the airframe, which should be shown through the analysis and test based on the related specifications. This paper introduces the full scale durability test to evaluate the structural safety and durability of the basic trainer, KT-1. The test was performed according to the procedure in the military specification. The flight by flight load spectrum was developed by KT-1 fatigue load criteria and used for the durability test. The durability test had been performed for 4 service lives and was completed successfully. Therefore, it was shown that KT-1 airframe satisfied the durability requirements.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.8
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• pp.621-629
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• 2020

LRU layout is a complex problem that requires consideration of various criteria such as airworthiness, performance, maintainability and environmental requirements. As aircraft functions become more complex, the necessary equipment is increasing, and unmanned aerial vehicles are equipped with more equipment as a substitute for pilots. Due to the complexity of the problem, the increase in the number of equipment, and the limited development period, the placement of equipment is largely dependent on the engineer's insight and experience. For optimization, quantitative criteria are required for evaluation, but criteria such as safety, performance, and maintainability are difficult to quantitatively compare or have limitations. In this study, we consider the installation and maintenance of the equipment, simplify the deployment model to the traveling salesman problem, Optimization was performed using a genetic algorithm to minimize the weight of the connecting cable between the equipment. When the optimization results were compared with the global calculations, the same results were obtained with less time required, and the improvement was compared with the heuristic.

• Journal of Platform Technology
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• v.8 no.4
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• pp.47-58
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• 2020

DO-330 Software Tool Qualification Considerations is a guideline for development of tools used to develop/verify software and hardware installed on aircraft. And among several processes, the verification process is very crucial as it occupies a large proportion for DO-330. Especially, in order to qualify tool with high safety level, test objectives must be performed with independence, accordingly, more time, cost, and manpower are required than other objectives. In addition, even if the test cases or test procedures are well defined, the higher the complexity of the test the higher probability of human error occurs. In this paper, we propose Script-based Test Automation Agent software structure for efficient DO-330 verification process of A661UAGEN tool developed by Hanwha Systems. Compared to the test performed manually by the test engineer, testing time of the Script-based Test Automation Agent is reduced by 87.5% and testing productivity is increased by 43.75%.