• Journal of the Korean Society for Nondestructive Testing
• /
• v.36 no.5
• /
• pp.345-352
• /
• 2016

As aircrafts are being operated at high altitude, wing structures experience various fatigue loadings under cryogenic environments. As a result, fatigue damage such as a crack could be develop that could eventually lead to a catastrophic failure. For this reason, fatigue damage monitoring is an important process to ensure efficient maintenance and safety of structures. To implement damage detection in real-world flight environments, a special cooling chamber was built. Inside the chamber, the temperature was maintained at the cryogenic temperature, and harmonic fatigue loading was given to a wing structure. In this study, piezoelectric active-sensing based guided waves were used to detect the fatigue damage. In particular, a beamforming technique was applied to efficiently measure the scattering wave caused by the fatigue damage. The system was used for detection, growth monitoring, and localization of a fatigue crack. In addition, a sensor diagnostic process was also applied to ensure the proper operation of piezoelectric sensors. Several experiments were implemented and the results of the experiments demonstrated that this process could efficiently detect damage in such an extreme environment.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.1
• /
• pp.18-31
• /
• 2018

Rotorcrafts have more severe crashworthiness conditions than fixed wing aircraft owing to VTOL and hovering. Recently, with the increasing demand for highly efficient transportation system, application of composite materials to aircraft structures is increasing. However, due to the characteristics of composite materials that are susceptible to impact and crash, demand to prove the crashworthiness of composite structures is also increasing. The purpose of present study is to derive the structural concept of composite subfloor for rotorcrafts and verify it. In order to design a crashworthy composite subfloor, the conceptual design of the testbed helicopter for the demonstration and the derivation of energy absorbing requirement were carried out, and the composite energy absorber was designed and verified. Finally, the testbed for the demonstration of a crashworthy composite structure was fabricated, and performed free drop test. It was confirmed that the test results meet the criteria for ensuring occupant survivability.

• Journal of Advanced Navigation Technology
• /
• v.26 no.5
• /
• pp.325-330
• /
• 2022

The sensors of aircraft are necessity for mission performance and fusion process of data from them is applied for increase of mission efficiency and decrease of aircraft pilot workload. Data fusion is applied and developed to provide pilot a series of more processed data format about a specific target from sensors in aircraft. Military aircraft currently in operation are linked with a tactical data link such as Link-16 to display improved tactical situation to pilots to increase mission efficiency. By fusing the sensor data with improved accuracy obtained as the sensors' performance mounted on the aircraft become higher and the tactical situation information received through the tactical data link, it provides the pilot with a highly reliable tactical situation and mission environment, and expects efficient mission performance and high survivability. In this paper, a fusion architecture to produce fused data with realtime information from the sensors and data through a tactical data link is shown.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.36 no.12
• /
• pp.1229-1235
• /
• 2008

ELT(emergency locator transmitter) has assisted in the rescue of thousands of lives in distress. Aviators, mariners and land users being equipped with distress beacons are capable of transmitting distress signals to the satellites in emergency situations anywhere in the world. In this paper, Drop/Impact simulation was performed for ELT Body-case. FE model for Body-case was constructed with MSC/Dytran and refined using the Karas example simulation for Body-case prototype. Shock/impact survivability analysis was performed for ELT operations. FE model constructed with MSC/Nastran. Transient response analysis for refined ELT model was perfomed for ELT under impact shock loading condition.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.5
• /
• pp.605-611
• /
• 2019

The fuel sloshing due to the rapid manoeuvre of the aircraft causes significant loads on internal components, which may break components or piping. In particular, a significant load is applied to the joint of the external fuel tank by sloshing movement, which may affect the safety of the aircraft when the joint of the external fuel tank is damaged. Therefore, in order to improve the survivability of aircraft and crew members, the design of external fuel tanks, and joints should be performed after evaluating the sloshing load through a numerical analysis of the fuel sloshing conditions. In this paper, a numerical analysis was performed on the sloshing test of the external fuel tank for rotorcraft. ALE (Arbitrary Lagrangian Eulerian) technique was used, and the test conditions specified in the U.S. Military Specification (MIL-DTL-27422D) was applied as the conditions for numerical analysis. As a result of the numerical analysis, the load on the joint of the external fuel tank was calculated. Moreover, the effects of sloshing movement on structural soundness were assessed through analysis of stress levels and margin of safety on metal fittings and composite containers.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.3
• /
• pp.777-783
• /
• 2021

Aircraft are affected by various vibrations during maneuvering. These vibrations may have a fatal effect on the survival of aircraft in some cases, so the safety of components applied to the aircraft should be proven against various vibrations through random vibration analysis. In this study, the structural robustness of an external fuel tank and pylon for military aircraft was evaluated under random vibration conditions using commercial software, MSC Random. In the random vibration analysis, a frequency response analysis was performed by imposing a unit load on the boundary condition point, and then excitation was performed with a PSD profile. In this process, the required mode data was extracted through a modal analysis method. In addition, the random vibration profile specified in the US Defense Environment Standard was applied as random vibration conditions, and the PSD profile given in units of G's was converted into units of gravitational acceleration. As a result of the numerical analysis, we evaluated the structural robustness of the external fuel tank and pylon by identifying the safety margins of beam elements, shell elements, and solid elements in a numerical model for random vibration in the x, y, and z directions.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.25 no.5
• /
• pp.405-411
• /
• 2012

Inside a rotorcraft fuel cell, pipes and components are located for fuel storage and fuel supply into the engine. Utility helicopters, operated in battle fields, fly at lower altitude compared to fixed-wing aircraft and hence are more likely to be exposed to gunfire. Since internal pressure of fluid increases when hit, the effect on LRU due to increase in pressure must taken into account when designing the aircraft for survivability. However, it is costly and time consuming to manufacture a fuel cell for gunfire test, and due to constraints from usage of live ammunition, related data gathered through numerical simulation is needed. In this study, numerical simulation on rotorcraft fuel cell exposed to gunfire was carried out using Autodyn to analyze bullet movement inside the fuel cell after hit, and internal pressure of fluid and equivalent stress on fuel cell assessed.

• 한국항공운항학회:학술대회논문집
• /
• 2016.05a
• /
• pp.249-254
• /
• 2016

저비용항공사들은 전세계적인 항공수요 증가 등으로 약진을 하기도 했지만, 2000년대 초반부터 세계 항공산업은 테러위험, 유가급등, 오일머니를 등에 업은 중동 항공사들의 급성장, 그리고 2008년부터 시작된 세계경제위기로 미국과 유럽, 일본 등 메이저 항공사들은 일단 최소한의 생존가능 임계규모를 갖추고자 뼈를 깎는 구조조정을 수반한 인수합병, 대외악재에 대한 대응능력 제고, 새로운 보조수익원 개발을 통해 위기를 헤쳐나갔다. 그러나 2013년 11월 단행된 중동 항공사들(Emirates, Qatar, Etihad)의 역사상 유례없는, 한화 약 170조원 규모의 항공기 구매계약에 미국과 유럽은 물론이고 아시아 메이저 항공업계까지 다시 한번 커다란 위기감에 휩싸이게 되었다. 이러한 상황하에서도 효율적 경영의 선구적 역할을 미국의 Southwest, 유럽의 LCC Ryan Air, 아시아의 LCC Air Asia 등 LCC산업은 극심한 경기침체를 겪으면서도 해당 산업의 규모는 지속적 성장을 거듭할 전망이다. 결론적으로, 이러한 상황에서, 비록 미국과 유럽 항공사들이 대규모 구조조정을 겪고 2012년 이후부터 점차 회복기미를 보이고 있긴 하지만, 중동 항공사들의 영향력에 대응하기 위해 향후에도 추가적인 구조조정은 물론 인수/합병 등 생존을 위한 메이저 항공사들 간의 빅딜이 이어질 전망이며, 일본처럼 내수시장이 넓지 않은 한국도 중국 등 성장잠재력이 높은 국가들과의 항공자유화 등을 적극적으로 추진하여 보다 넓은 시장을 확보하지 못한다면 머지않아 수익성에 큰 타격을 입을 수밖에 없다는 결론에 도달하였다.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.5
• /
• pp.521-530
• /
• 2011

Since aircraft fuel tanks have many interfaces connected to the airframe as well as the fuel system, they have been considered as one of the system-dependent critical components. Crashworthy fuel tanks have been widely implemented to rotorcraft and rendered a great contribution for improving the survivability of crews and passengers. Since the embryonic stage of military rotorcraft history began, the US army has developed and practised a detailed military specification documenting the unique crashworthiness requirements for rotorcraft fuel tanks to prevent most, hopefully all, fatality due to post-crash fire. The mandatory crash impact test required by the relevant specification, MIL-DTL-27422D, has been recognized as a non-trivial mission and caused inevitable delay of a number of noticeable rotorcraft development programs such as that of V-22. The crash impact test itself takes a long-term preparation efforts together with costly fuel tank specimens. Thus a series of numerical simulations of the crash impact test with digital mock-ups is necessary even at the early design stage to minimize the possibility of trial-and-error with full-scale fuel tanks. In the present study the crash impact simulation of a few fuel tank configurations is conducted with the commercial package, Autodyn, and the resulting equivalent stresses and internal pressures are evaluated in detail to suggest a design improvement for the fuel tank configuration.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.1
• /
• pp.105-112
• /
• 2009

For the purpose of facing battle damage that a fighter is subject to in combat, following recovery procedures such as damage assessment, repair design and structural integrity evaluation are investigated. A sample study is presented on the battle damage of F-15 ECS bay, which is comprised of damage assessment and repair design based on ABDR(Aircraft Battle Damage Repair) skills and work procedure complying with AFTO(Air Force Technical Order) forms. Further, the flight safety of repaired structure is validated and the time the permanent repair should be done is estimated through the evaluation of structural integrity such as the calculation of static strength and fatigue life.