• International Journal of Aeronautical and Space Sciences
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• v.18 no.1
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• pp.165-173
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• 2017

The aeromechanics predictions of HART I rotor obtained using a computational structural dynamics (CSD) code are evaluated against the wind tunnel test data. The flight regimes include low speed descending flight at an advance ratio of ${\mu}=0.151$ and cruise condition at ${\mu}=0.229$. A lifting-line based unsteady airfoil theory with C81 table look-up is used to calculate the aerodynamic loads acting on the blade. Either rolled-up free wake or multiple-trailer wake with consolidation (MTC) model is employed for the free vortex wake representation. The measured blade properties accomplished recently are used to analyze the rotor for the up-to-date computations. The comparison results on airloads and structural loads of the rotor show good agreements for descent flight and fair for cruise flight condition. It is observed that MTC model generally improves the correlation against the measured data. The structural loads predictions for all measurement locations of HART I rotor are investigated. The dominant harmonic response of the structural loads is clearly captured with MTC model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.3
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• pp.207-212
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• 2010

This paper presents a spiral descending path and a landing guidance law for net-recovery of a fixed-wing unmanned aerial vehicle. The net-recovery landing flight is divided into two phases. In the first phase, a spiral descending path is designed from an arbitrary initial position to a final approaching waypoint toward the recovery net. The flight path angle is controlled to be aligned to the approaching direction at the end of the spiral descent. In the second phase, the aircraft is guided from the approaching waypoint to the recovery net using a pseudo pursuit landing guidance law. Six degree-of-freedom simulation is performed to verify the performance of the proposed landing guidance law.

• Journal of the military operations research society of Korea
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• v.32 no.1
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• pp.176-187
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• 2006

It is difficult to estimate missile flight trajectory since a ballistic missile velocity is highly fast and has inherent behavior such as corkscrew due to unstable descending. This paper describes a comprehensive analysis of the flight trajectory characteristics of ballistic missiles. Various missile flight ranges based the comprehensive flight trajectory characteristics are derived by an analytical approach. It is shown analytically that threat due to the flight characteristics is significantly increased with reducing maximum missile ranges. This work is basic research of the establishment of operational concept for the lower tier missile defense system implementation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.5
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• pp.359-367
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• 2018

The vortex ring state that occurs during the descending flight of a rotorcraft generates a circulating flow like a donut near the rotating surface, and it often causes a rotorcraft fall due to loss of thrust. In this paper, we have physically identified the flow field in the vortex ring state of the quadcopter, one of the types of unmanned aerial vehicles. The descending flight of the quadcopter was simulated in a 1m subsonic wind tunnel of the Korea Aerospace Research Institute(KARI) and the Particle Image Velocimetry(PIV) was used for the flow field measurement. The induced velocity in the hovering state is estimated by using the momentum theory and the test was carried out in the range of descent rate at which the vortex ring condition could be caused. The development and the direction of the vortex ring were confirmed by the measurement of the flow field according to not only the descent rate but also propeller separation distance. In addition, the results of the study show the vortex ring state can be predicted sufficiently by measuring the flow velocity around the quadcopter.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.1
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• pp.83-88
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• 2010

The study is intended to help to select the pilot candidates with exceptional flight aptitude ability and to investigate the relationship between the results of the scholastic aptitude test and the flight aptitude. It is intended that the research will help to draw recommendations on the relevant fields of the scholastic aptitude test that is to be used to select the high caliber candidates with exceptional flight aptitude ability, to gauge the resulting effectiveness of its application and helping to revise the university's syllabus accordingly. From the study, korean, mathematics, english grade and the flight aptitude test results have all shown to hold mutual relationship and through simple correlation analysis, it was discovered that mathematics and English are the two factors that affect the results of the flight aptitude test, with the extent of its impact graded in descending order of English, mathematics and Korean. Lastly, the logistic regression analysis have discovered that the mathematics grade has significant effect on the classification of the flight aptitude and non aptitude category groups, and English also has significant influence close to the 0.05 p-values. It is believed that should the findings of this study be considered as part of the selection process of the university applicants of the department of aeronautical science, making discovery of candidates of higher quality is expected.

• Korean Journal of Applied Biomechanics
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• v.28 no.2
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• pp.69-78
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• 2018

Objective: The purpose of this study was to investigate the feasibility of a new vault technique through a kinematic comparison of the YANG Hak Seon and Yeo 2 vaults. Method: The photographic images of the YANG Hak Seon and Yeo 2 vaults were collected using a high-speed camera, and their kinematic characteristics were analyzed using three-dimensional image analysis. Results: During the post-flight phase of the Yeo 2 and YANG Hak Seon vaults, the time of flight, height of flight, and flight distance were similar. At the peak of the post-flight phase, the trunk rotation angle of the YANG Hak Seon vault rotated $457^{\circ}$ more than did the Yeo 2 vault. During the post-flight descending period, the twist velocity of the trunk was much faster with the YANG Hak Seon vault ($1,278^{\circ}/s$) than with the Yeo 2 vault ($1,016^{\circ}/s$). Conclusion: To succeed in the new technique, the average twist velocity during post-flight must be maintained at $1,058^{\circ}/s$ and the twist velocity must be increased from the ascending phase.

• Journal of the Korea Safety Management & Science
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• v.8 no.2
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• pp.71-80
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• 2006

There are many display panels in the flight cockpit and pilots get various flight information from those displays. The ergonomic layout of the displays must be determined based upon frequency of use and sequence of use. This study investigated the visual search patterns of the six display groups(one head-up-display: HUD, two multi function displays: MFDs, one engine group: EG, one flight display group: FD and others) in a fighting aircraft. Four expert pilots conducted Imaginary flight in the physical mock-up and the eye movements were collected using eye tracking system. Data of dwell time, frequency of use, and eye movement path were collected. Pilots spent most of time on HUD(55.2%), and others (21.6%), FD(14.2%), right MFD(4.7%), EG(3.2%), and left MFD(1.1%) in descending order. Similarly HUD(42.8%) and others(30.0%) were the most frequently visited displays. These data can be used in the layout of cockpit displays and the determination of optimal visual search pattern.

• Journal of Advanced Navigation Technology
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• v.5 no.1
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• pp.19-25
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• 2001

In this study an analysis on flight characteristics and flight control methods for a wing in ground effect vehicle is made. In order to closely view its nonlinearity a few limit cycles are examined and related to the characteristics of the linearized systems. Several flight control methods are compared for the cruise mode with initial height error and command tracking mode of ascending, cruise, and descending. In comparison performance and the implementation aspects are examined. For the possible control inputs, combinations of elevator, thrust, and flap are considered and LQR-based output command tracking scheme is applied in the control system design.

• Journal of Aerospace System Engineering
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• v.11 no.5
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• pp.20-27
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• 2017

The present paper describes the flow analysis of the flows around the multicopter for the selection of optimal position of air data sensor. For the flow analysis, the commercial fluid dynamics solver, STAR-CCM+ was used with polygon mesh and k-w SST turbulence modeling options. For the simulation of each rotating 4 propellers, unstructured overset mesh method was used. Hovering, forward flight, ascending and descending flight conditions are selected for the analysis and airspeed and flow angle errors were investigated using the CFD results. Through the flow field analysis, sensor location above one propeller diameter distance from the propeller rotating plane showed airspeed error less than 1m/s within the typical flight conditions of multicopter except descending.

• Journal of Aerospace System Engineering
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• v.9 no.4
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• pp.62-66
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• 2015

During the conceptual design of turboprop aircraft, the power effect driven from rotating propeller is typically obtained from empirical data. In the present paper, propeller power effect was obtained by using unsteady three-dimensional Navier-Stokes solver with $k-{\omega}$ turbulence model for the accurate prediction of turboprop aircraft performance. In order to simulate the relative motion between propeller and fuselage, unsteady sliding mesh method was used. During simulation, three flow conditions such as climb, cruise and descending flight were selected considering the flight envelop of the real turboprop aircraft. For the correction of aerodynamic coefficients, the thrust effect of engine exhaust gas was included based on the engine manufacturer's data. Using the computational results, the correction table for the aerodynamic coefficient of turboprop aircraft was suggested for the performance analysis of turboprop aircraft.