완전분해 점검을 통한 장기운영 전투기 전기배선시스템의 신뢰성분석

이호용 한국항공운항학회 2018 한국항공운항학회지 Vol.26 No.4

According to the incresement of aging aircraft, Republic of Korea Air Force (RoKAF) conducted a teardown inspection of aircraft’s EWIS (electrical wiring interconnection system) to determine the status of deterioration and the influence of failure occurrences due to it. The inspected aircraft were the retired fighter jets that had been used for more than 40 years. By analyzing defect type and the defect tendency, RoKAF can establish the necessary measures for the usage extension of their fleet and furthermore, the analysis results can be used as a basic data for the preparation of it’s aircraft aging. EWIS inspection was done throughout careful visual inspection technique by removing all the ducts and pipes located in the fuselage and wings. For the aircraft wiring where no damage was found, the elongation tests were performed to determine the deterioration of wiring according to the location of the aircraft. The connectors, which is the main cause of intermittent failure, were completely disassembled and inspected for internal damage such as corrosion, abrasion, and traces of foreign objects. The detected defects were classified into 4 severity levels based on the type of damage, and the classified defects were weighted according to the criticality which may affects to it’s system to establish the action plan.

A study on optimizing the electrical load analysis for modifying the avionics equipment in an aged aircraft

윤인복,안경수 항공우주시스템공학회 2021 항공우주시스템공학회지 Vol.15 No.4

In the management of aged aircraft, used avionics equipment is replaced with new ones to improve the performance and extend the life cycle of the aircraft. In this case, considering airworthiness, it is necessary to check whether the aircraft has sufficient electricity in the electric generator or the electrical distribution system, in accordance with the maximum electricity consumption of the new avionics equipment. Accordingly, this paper reviews a few airworthiness standards and guidelines associated with the electrical load analysis when an avionics equipment is upgraded in an aged aircraft, and proposes an optimization method for the electrical load analysis. In addition, it verifies the validity of the proposed method via the QFD theory, and is currently available for upgrading the performance of aged aircraft.

Crack growth life model for fatigue susceptible structural components in aging aircraft

Chou, Karen C.,Cox, Glenn C.,Lockwood, Allison M. Techno-Press 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.1

A total life model was developed to assess the service life of aging aircraft. The primary focus of this paper is the development of crack growth life projection using the response surface method. Crack growth life projection is a necessary component of the total life model. The study showed that the number of load cycles N needed for a crack to propagate to a specified size can be linearly related to the geometric parameter, material, and stress level of the component considered when all the variables are transformed to logarithmic values. By the Central Limit theorem, the ln N was approximated by Gaussian distribution. This Gaussian model compared well with the histograms of the number of load cycles generated from simulated crack growth curves. The outcome of this study will aid engineers in designing their crack growth experiments to develop the stochastic crack growth models for service life assessments.

노후 항공기 신규 블레이드 타입 안테나 장착에 따른 피로 해석 연구

이상훈,이숙,최상민 항공우주시스템공학회 2019 항공우주시스템공학회지 Vol.13 No.5

In this study, as a part of the aging aircraft performance improvement project for which no design information is provided, a new type of blade antenna is installed on the main part of the aging aircraft, and the method of proving the fatigue life of the main part of the aircraft is reviewed and summarized. There are various methods to prove fatigue life according to the manufacturer and aircraft design conditions. The fatigue life prediction and damage tolerance range of the relevant site were obtained through related regulations and industry examples. From these results, the fatigue life of newly installed antennas around the main parts of the aging aircraft was evaluated and the maintenance period and criteria were set according to the damage tolerance. 본 논문에서는 성능개량사업의 일환으로 설계 정보가 제공되지 않은 노후 항공기의 블레이드 형상 신규 안테나를 항공기 외부 주요 부위에 장착 시, 이에 대한 피로 수명을 입증하는 방법을 검토하고 정리하였다. 각 항공기 제조사 및 설계 조건에 따라 피로 수명을 입증하는 여러가지 방법들이 존재하며, 본 연구에서는 관련 규정과 항공기 산업체들의 예를 통하여 안테나가 장착된 항공기 동체의 해당 부위에 피로 수명 예측과 손상 허용 범위를 계산하였다. 이 계산 결과를 통해서 노후 항공기 주요 부위에 신규로 장착된 안테나 주변 구조물에 대한 피로 수명을 평가하고 손상 허용에 따른 정비 주기 및 관련 기준들을 설정하였다.

Detection of Second-Layer Corrosion in Aging Aircraft

Nohyu Kim,Seunyong Yang 한국비파괴검사학회 2009 한국비파괴검사학회지 Vol.29 No.6

The Compton backscatter technique has been applied to lap-joint in aircraft structure in order to determine mass loss due to exfoliative corrosion of the aluminum alloy sheet skin. The mass loss of each layer has been estimated from Compton backscatter A-scan including the aluminum sheet, the corrosion layer, and the sealant. A Compton backscattering imaging system has been also developed to obtain a cross-sectional profile of corroded lap-splices of aging aircraft using a specially designed slit-type camera. The camera is to focus on a small scattering volume inside the material from which the backscattered photons are collected by a collimated scintillator detector for interpretation of material characteristics. The cross section of the layered structure is scanned by moving the scattering volume through the thickness direction of the specimen. The theoretical model of the Compton scattering based on Boltzmann transport theory is presented for quantitative characterization of exfoliative corrosion through deconvolution procedure using a nonlinear least-square error minimization method. It produces practical information such as location and width of planar corrosion in layered structures of aircraft, which generally cannot be detected by conventional NDE techniques such as the ultrasonic method.

장기운용항공기 구조물의 잔여 피로수명예측 기법

이은경,정유인,김상식,Lee, Eungyeong,Jeong, Yooin,Kim, Sangshik 한국재료학회 2015 한국재료학회지 Vol.25 No.10

Aging aircraft structures are inevitably exposed to environment for a long time facing many potential problems, including corrosion and wide spread fatigue damage, which in turn cause the degradation of flight safety. In this study, the environmental surface damages on aging aircraft structures induced during service were quantitatively analyzed. Additionally, S-N fatigue tests were performed with center hole specimens extracted from aging aircraft structures. From the results of quantitative analyses of the surface damages and fatigue tests, it is concluded that corrosion pits initiated during service reduce the fatigue life significantly. Finally, using the fracture mechanics and the EIFS (equivalent initial flaw size) concepts, the remaining fatigue life was predicted based on actual fatigue test results.

신규 블레이드 안테나 장착을 위한 노후 회전익 항공기 구조 해석 연구

유정오,김재용,최항석 항공우주시스템공학회 2021 항공우주시스템공학회지 Vol.15 No.5

In this study, we performed a design and structural analysis of a blade-shaped antenna installation on the rear fuselage of a rotary wing aircraft operated by the military. When the structure is damaged while the aircraft is in operation, it is separated from the aircraft main structure and may collide with the rotor or blades to cause the aircraft to crash. Therefore, structural safety for the modified structure must be secured. The design requirement for the newly installed modified part were established, and the load condition was constructed by applying the load that may occur in the aircraft after the modification. Structure safety for the modified structure was secured by performing structure analysis. To analysis stress and deformation of aircraft structure, we developed finite element model and verified it by using hand calculation method. We confirmed the safety of the modified structure through the final structural integrity analysis. 본 논문에서는 군에서 운용하고 있는 회전익 항공기의 후방 동체 상부에 블레이드 형상을 가진 안테나 장착 설계와 구조 건전성 해석을 수행하였다. 항공기 운항 중 안테나 또는 지지 구조물이 파손되면 기체에서 분리되어 로터 부위 및 블레이드와 충돌할 수 있다. 이 경우 항공기가 추락에 이를 수 있는 위험한 상황이 되기 때문에 반드시 개조 구조물들에 대한 구조 해석을 통해 구조적인 안전성을 확보해야 한다. 안테나 신규 장착 부위와 개조 부위에 대한 설계 요구 조건을 분석하고, 개조 전/후 항공기에 작용하는 하중을 적용하였다. 본 연구에서는 안테나 신규 장착 부위와 개조 부위에 대한 설계 요구 조건을 분석하고, 개조 전/후 항공기에 작용하는 하중을 적용하여 지지 구조물에 대한 구조해석을 수행하여 안전성을 확보하였다. 유한요소 모델을 구성하여 응력과 변형량을 확인하고 이론적인 분석 방법을 통해 유한요소 모델을 검증하였다. 이를 토대로 설계된 구조물의 구조 건전성을 확인하였다.

Detection of Second-Layer Corrosion in Aging Aircraft

김노유,양승용 한국비파괴검사학회 2009 한국비파괴검사학회지 Vol.29 No.6

The Compton backscatter technique has been applied to lap-joint in aircraft structure in order to determine mass loss due to exfoliative corrosion of the aluminum alloy sheet skin. The mass loss of each layer has been estimated from Compton backscatter A-scan including the aluminum sheet, the corrosion layer, and the sealant. A Compton backscattering imaging system has been also developed to obtain a cross-sectional profile of corroded lap-splices of aging aircraft using a specially designed slit-type camera. The camera is to focus on a small scattering volume inside the material from which the backscattered photons are collected by a collimated scintillator detector for interpretation of material characteristics. The cross section of the layered structure is scanned by moving the scattering volume through the thickness direction of the specimen. The theoretical model of the Compton scattering based on Boltzmann transport theory is presented for quantitative characterization of exfoliative corrosion through deconvolution procedure using a nonlinear least-square error minimization method. It produces practical information such as location and width of planar corrosion in layered structures of aircraft, which generally cannot be detected by conventional NDE techniques such as the ultrasonic method.

Detection of Second-Layer Corrosion in Aging Aircraft

Kim, Noh-Yu,Yang, Seun-Yong The Korean Society for Nondestructive Testing 2009 한국비파괴검사학회지 Vol.29 No.6

The Compton backscatter technique has been applied to lap-joint in aircraft structure in order to determine mass loss due to exfoliative corrosion of the aluminum alloy sheet skin. The mass loss of each layer has been estimated from Compton backscatter A-scan including the aluminum sheet, the corrosion layer, and the sealant. A Compton backscattering imaging system has been also developed to obtain a cross-sectional profile of corroded lap-splices of aging aircraft using a specially designed slit-type camera. The camera is to focus on a small scattering volume inside the material from which the backscattered photons are collected by a collimated scintillator detector for interpretation of material characteristics. The cross section of the layered structure is scanned by moving the scattering volume through the thickness direction of the specimen. The theoretical model of the Compton scattering based on Boltzmann transport theory is presented for quantitative characterization of exfoliative corrosion through deconvolution procedure using a nonlinear least-square error minimization method. It produces practical information such as location and width of planar corrosion in layered structures of aircraft, which generally cannot be detected by conventional NDE techniques such as the ultrasonic method.

장기운영 항공기의 확률론적 위험도평가 접근에 관한 연구

김근원 ( Keun Won Kim ),김용대 ( Yong Dae Kim ),신기수 ( Ki Su Shin ) 한국항공경영학회 2012 한국항공경영학회지 Vol.10 No.2

내구성해석의 궁극적인 목적은 구조물의 사용수명을 예측하는 것이다. 사용수명을 예측하기 위하여 과거에는 결정론적 해석 기법이 적용되었다. 그러나 최근 미국, 호주 등 선진 항공운영국들에서는 비행안전을 향상시키기 위하여 확률론적 해석 기법을 적용하고 있다. 특히 확률론적 해석 접근은 파손확률을 이용하여 위험도평가를 수행할 수 있다. 그리고 확률론적 위험도평가는 적절한 점검시간 산출 등의 유용한 정보를 의사결정자들에게 제공하여 정비비용 감소를 창출할 수 있는 이점이 있다.본 연구에서는 파손확률을 이용하여 항공기 구조물의 점검주기 개선을 위한 확률론적 위험도평가를 수행하였다. 이를 위해 장기운영 항공기 구조물의 점검주기 개선을 위한 위험도평가 모델을 제시하였다. 그리고 제안된 프로세스를 평가하기 위하여 F-00 항공기 wing 15% spar 부품 균열에 대하여 확률론적 위험도평가를 수행하였다. 본 연구수행 결과 초기점검시간을 늘리고 점검주기를 단축하여도 항공기 안전운영이 가능한 것으로 도출되었다. 그리고 본 연구결과에 따라 초기점검시간 및 점검주기 개선은 항공기 정비 비용감소로 이어져 경제적인 항공경영에 이바지할 수 있을 것으로 판단된다. The main purpose of durability analysis is to predict the service life of the structure. In the past, the deterministic analysis approach has been frequently employed to predict service life. However, the probabilistic analysis approach has recently been adopted as a advanced approach to determine the safety of flight by leading countries in aerospace fields. Especially, probabilistic analysis approach can perform probabilistic risk assessment by using probability of failure. The result of probabilistic risk assessment can provide useful information for determining proper inspection time of the fleet in order to maintain airworthiness. In this paper, the risk assessment for aging aircraft structure was conducted to refine the inspection interval by using probability of failure. To achieve this goal, we propose new process which can apply risk assessment to aging aircraft structure. Also to evaluate the proposed process, wing 15% spar was selected as a numerical example. In conclusion, it was revealed that extension of inspection interval and initial inspection time can assure the safety operation of aging aircraft structure. Also these results can lead to new way of economical aviation management.