• Journal of Advanced Navigation Technology
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• v.25 no.1
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• pp.52-59
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• 2021

According to the International Air Transport Association (IATA), 61% of the accidents occurred during the approach and landing phase of the flight, with 16% of the accidents caused by unstable access of the commercial aircraft. It was identified that the pilot's unstable approach and poor manipulation of correction led to accidents by continuing the excessive approach without go-around manuever. The causes of unstable access may vary, including airport approach procedures, pilot error, misplanning, workload, ATC (Air Traffic Contol) congestion, etc. In this study, we use the flight data analysis system to select domestic case airports and aircraft type where unstable approach events occur repeatedly. Through flight data analysis, including main events, airport approach procedures, pilot operations, as well as various environmental factors such as weather and geographical conditions at the airport. It aims to identify and eliminate the tendency of unstable approach events and the causes and risks of them to derive implications for mitigating unstable approach events and for developing navigation safety measures.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.3
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• pp.1-8
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• 2018

Aviation industry is growing rapidly, and this growth is expected to continue. However, aircraft accident rate is still high, and 65 percent of accidents occur during landing phase due to unstable approach. Therefore, this research analyzed causes and countermeasures of unstable approach. In order to derive countermeasures, this study selected P International Airport as an example case. In addition, this research analyzed A airline's FOQA data, regional Standard Operating Procedures, and 5 years of environmental factors to identified correlation of those contributing factors. In conclusion, his research concluded following results. First of all, because of P International Airport's geological features, pilots are required to conduct Circling Approach, and this advanced maneuver increases workload at the final stage of flight. Secondarily, meteorological factors such as crosswind, seasonal rain front, local visibility contributes unstable approach. Lastly, these geological and meteorological factors are interrelated, and this uncommon environment can decrease circumstantial judgement ability of pilots and jeopardize aviation safety. As a consequence, it is recommended to reinforce the Crew Resource Management and Threat & Error Management systems so that pilots can perceive identical safety target.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.1-1
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• 1998

로켓엔진 추력발생용으로 광범위하게 사용되는 액체추진제는 고성능, 대용량의 액체추진제 로켓엔진에서는 필연적으로 고주파 연소불안정의 문제를 수반하며, 이 연소불안정의 정도는 연소성능과 더불어 엔진개발의 성패를 좌우하는 중요한 여건이 된다. 따라서 안정한 로켓의 비행을 보장하기 위해서는 연소불안정의 문제가 선결되어야 한다. 연소불안정의 기본 메커니즘은 연소기에서 발생하는 압력섭동에 반응하여 불안정한 음향에너지를 되먹임하는 연소과정으로 설명된다. 연소불안정 현상이 발견된 이후 실험 및 이론적 접근에 의해 이와 같은 연소불안정 메커니즘 및 예측에 대한 체계적인 연구가 이루어져 왔으며, 현재까지의 다양한 고주파 연소불안정 예측방법 중에서 음향 및 기화 응답함수를 이용하는 방법은 직관적 고찰에 의존하는 단순한 연소모델을 적용하며 주로 음향적 섭동에 의한 연소의 반응을 연소안정성 평가의 파라메터로 사용한다. 이와 같은 음향적인 예측방법은 연소불안정 현상을 이론적으로 전개하므로 경제적으로 각종 설계변수에 대한 연소불안정의 변화를 구분할 수 있는 장점이 있어 성능 및 호환설계와 병행하여 로켓엔진 연소실의 초기 안정성 설계방법으로 주로 사용된다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.47-53
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• 2017

One of the most common causes of failure of space launch vehicles is combustion instability. Combustion instability is a phenomenon that the pressure perturbation inside the combustion chamber is greatly amplified due to the interaction of the pressure perturbation inside the combustion chamber and the heat release perturbation. When this phenomenon becomes worse, an engine failure or launch vehicle crash occurs. In order to predict and avoid such combustion instability, understanding of the phenomenon is indispensable, and numerical, theoretical, and experimental approaches to combustion instability have been carried out worldwidely.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.4
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• pp.63-77
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• 2008

This paper described the general concept of combustion instability and its mechanism in gas turbine engines. The approaching method to study this phenomenon was introduced including the up-to-date research activity in tile world. Combustion instability is one of critical problems, still now, affecting engine performance, durability and operation. In addition it is known that this problem is caused by coupling between fuel or air flow fluctuation and heat release rate in gas turbine engines, which is related with NOx reduction strategies. Therefore, in order to understand the current status of combustion instability we reviewed the combustion instability phenomenon in gas turbine engines.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.65-67
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• 2017

Various combustion modeling approaches have been developed and verified in a combustion system such as rockets, gas turbines, and so on. This study introduces basic theory and recent research activities on 1D network model where a system is divided into a series of acoustic element and mass/momemtum/energy conservations are applied in the component. Each component is connected to the neighboring ones with proper jump conditions. Flame transfer function and acoustic transfer function are determined and effects of the each function on the system instability is investigated.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2849-2851
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• 2005

본 논문에서는 소형 카오스 무인 비행체에서의 장애물 회피 기법과 목표물 탐지 기법을 제안하였다. 장애물은 불안정한 VDP(van der Pol) 방정식을 이용하였으며 목표물은 안정한 VDP 방정식을 이용하였다. UAV가 장애물과 목표물에 접근하게 되면 불안정 또는 안정한 VDP 방정식이 UAV를 밀어내거나 끌어들임으로서 장애물을 피해가거나 목표물 탐색할 수 있는 알고리즘을 제시하고 컴퓨터 시뮬레이션으로 그 결과를 검증하였다.

• Life and Agrochemicals
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• s.246
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• pp.20-23
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• 2009

지금 한국 농업이 당면한 가장 힘든 장애물은 농업에 대한 올바른 이해와 인식의 부재다. 농업정책과 농업보조는 선심성의 시혜가 아니다. 농업이 생산하는 다원적 기능에 대한 정당한 보상이며, 경제적 불안정과 사회적 갈등에 대한 안전망을 제공하는 국가존립의 기반이다. 그런 인식하에서 접근되어야 한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.8
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• pp.79-86
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• 2006

Swirl injector with adjustable backhole length was analyzed to suppress high-frequency combustion instability in Liquid Rocket Engines. In order to analyze the effect of variable backhole injector as an acoustic absorber, backhole injector was regarded as a quarter-wave resonator. As a result of theoretical approaches and acoustic tests, backhole injector with adjustable length could decrease the unstable modes of combustion chamber. And the damping efficiency was estimated by measuring damping rates experimentally.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.68-77
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• 2017

High-frequency combustion instability results from a feedback coupling between the unsteady heat release rate and the acoustic waves formed resonantly in the combustion chamber. It can be modeled as thermoacoustic problems with various degrees of the assumptions and simplifications. This paper presents numerical analysis of self-excited combustion instabilities in a variable-length lean-premixed combustor and designs of passive control devices such as baffle and acoustic resonators in a framework of 3-D FEM Helmholtz solver. Nonlinear behaviors such as steep-fronted shock waves and a finite amplitude limit cycle are also investigated with a compressible flow simulation technique.