• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.4
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• pp.17-24
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• 2006

Hydrodynamic ram of aircraft fuel tanks is one of main ballistic battle damages of an aircraft and has great importance to airframe survivability design. Basic concept, physics and research history of hydrodynamic ram are investigated. The penetration and internal detonation of a simple fuel tank and ICW(Intermediate Complexity Wing) are analyzed by computational method. Structural rupture and fluid burst are analytically realized using general coupling and coupling surface interaction. The results such as fluid pressure, tank stress and displacement are shown and future research chances are suggested based on the study.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.1
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• pp.41-49
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• 2015

Analysis and test of hydrodynamic ram in welded metallic tanks containing water were performed to investigate the phenomena and to understand the effects on the resulting structural behavior. Arbitrary Lagrange-Euler coupling method was used for the analysis of the fluid-structure interaction occurring in the hydrodynamic ram, where the projectile, tank, and water are exchanging load, momentum, and energy during the traveling of the projectile through the water of the tank. For a better representation of the physical phenomena, modeling of the welded edges is added to the analysis to simulate the earlier weld line fracture and its influence on the resulting hydrodynamic ram behavior. Corresponding hydrodynamic tests were performed in a modified gas gun facility, and the following panel-based examinations of various parameters, such as displacement, velocity, stress, and energy, as well as hydrodynamic ram pressure show that the analysis and test are well correlated, and thus the results of the study reasonably explain the characteristics of the hydrodynamic ram. The methodology and procedures of the present study are applicable to the hydrodynamic ram assessment of airframe survivability design concepts.

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

• Journal of Aerospace System Engineering
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• v.7 no.2
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• pp.35-41
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• 2013

Crashworthiness design concept in the helicopter development is still under evolutionary stage. Survivability in the event of a crash was remarkably improved and this fact can be recognized by the analysis results on the AH-64 Apache and UH-60 Black Hawk crash accidents. Those two models are the first ones in which the crashworthiness design concept was applied with a full-scale requirement. Here we need to notice that under-design of the system results in unexpected injuries and deaths while over-design of the crashworthy elements result in unnecessary weight and costs. If landing gear system would be verified to have enough energy absorption capability in the specified vertical velocity interval, then design requirements of the airframe, fuel system and seats could be modified positively. In this paper, the right and systematic crashworthiness design concept is reviewed on the assumption that design requirements of some crashworthy elements could be partially tailored.

• Composites Research
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• v.31 no.5
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• pp.238-245
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• 2018

The hydrodynamic ram (HRAM) phenomenon is one of the main types of ballistic battle damages of a military aircraft and has great importance to airframe survivability design. The HRAM effect occurs due to the interaction between the fluid and structure, and damage can be investigated by measuring the pressure of the fluid and the dynamic strains on the structure. In this paper, HRAM test of a composite T-Joint was performed using a ram simulator which can generate HRAM pressure. In addition, calibration tests of PVDF sensor were performed to determine the circuit capacitance and time constant of the measurement system. The failure behavior of the composite T-Joint due to HRAM pressure was examined using the strain gauges and a PVDF sensor which were attached to the surface of the composite T-Joint.

• Journal of Aerospace System Engineering
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• v.17 no.1
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• pp.16-23
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• 2023

The aircraft fuel system performs a number of functions such as supplying fuel, transferring fuel between fuel tanks, and measuring the amount of residual fuel in each fuel tank. Since it is a direct cause of fire hazard in crash incident, it is a must to improve survivability of crew members by designing the airframe to tolerate expected crash impact. The civil aviation authority requires intensive verification of the fuel system design to determine precise application of the airworthiness requirement. Research activity on airworthiness certification criteria and verification scheme is still insufficient, although it has a significant importance. In this paper, as part of a study to improve flight safety by developing guidelines for demonstrating fuel system crash resistance, analysis results of fuel system crash-related airworthiness certification standards, verification scheme, and cases study applicable to military rotorcraft have been reviewed.

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