• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.27-34
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• 2004

In the Smart UAV Development Program, one of the 21c Frontier R&D Program, the tiltrotor has been studied as the concept of vehicle. The tiltrortor aircraft take-off and land in rotary wing mode like conventional helicopter, and cruise in fixed wing mode like conventional propeller airplane. For the conversion of the flight mode from helicopter to airplane, the nacelle located at wing tip has to be tilted from about 90 degrees of helicopter mode to about 0 degree of airplane mode. In this study, the aerodynamic characteristics of the wing with tilted nacelle is investigated using computation fluid dynamics technique. In order to feature out aerodynamic interferences between wing and nacelle, the flow calculations are conducted for the wing and the nacelle separately and for the combined geometry of wing and nacelle, respectively. Through this computations, not only the aerodynamic data-base for the wing-nacelle is constructed but also its contribution to the configuration design of the wing-nacelle is anticipated.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.8-13
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• 2007

Unsteady flow simulation for the tiltrotor Smart UAV configuration was performed to investigate the powered rotor wake effect on aerodynamic characteristics. Calculations were performed to simulate various flow conditions based on different flight modes including hover, conversion and cruise. Three-dimensional compressible Navier-Stokes equation code were used for flow calculation and Chimera grid technique overlapping individually generated grids was employed. A dynamic grid method was adopted in simulation of the rotating blades. Flow calculations were also conducted for the un-powered case. Aerodynamic interaction between the rotor and airframe was investigated comparing three data sets from the un-powered, powered, and isolated rotor cases.

• Journal of Aerospace System Engineering
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• v.15 no.2
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• pp.10-15
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• 2021

The propeller wake of tiltrotor-type aircrafts, such as TR-60 and quad tilt propeller (QTP) UAV, in hover substantially impinges the upper surface of the primary wing and generates a downward load. This load is directly proportional to the thrust of the propeller and reduces the available payload. Therefore, wing and nacelle mechanisms should be carefully designed to reduce downward load. This study conducted a numerical analysis of the rotating propeller in hover to predict the downward load of a QTP UAV. An unsteady three-dimensional Navier-Stokes solver was used along with a sliding mesh for the simulation of the rotating propeller. To reduce the downward load, the tilting mechanisms of the partial wing and nacelle were simultaneously introduced and numerically analyzed. Finally, the downward load was predicted by 14% of isolated propeller thrust; further, the downward load could be reduced by adopting the partial wing and nacelle tilting concept.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.2
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• pp.133-139
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• 2017

Flight control computer of tiltrotor UAV was designed by redundancy system with primary and secondary channels to improve reliability. The redundancy functions consist of channel switching and data recovery. The channel switching function consists of software method by using cross channel data link and hardware method by using watchdog timer. The data recovery is the function to maintain flight condition when the flight control computer is restarted exceptionally in operation. The redundancy system was verified by flight control computer bench test, system integration test and HILS test. This paper describes the redundancy function of tiltrotor UAV flight control computer and test-verification method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.9
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• pp.16-26
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• 2005

The aerodynamic design of a proprotor for the Smart UAV adopting tiltrotor aircraft concept is conducted in this study. Since proprotor of tiltrotor aircraft is operated at both rotary and fixed wing mode with single configuration rotor, the proprotor has to be designed to meet performance requirements for both flight modes. The aerodynamic design of proprotor is accomplished by combining three sources of data - the proprotor performance data, the aerodynamic data of vehicle, and the performance data of engine. The performance analysis code for proprotor is based on the combined momentum and blade element theory and validated by comparison with the TRAM data. In order to design configuration for a proprotor satisfying requirements for both rotary and fixed wing mode, various kind of performance maps are constructed for many performance and configuration parameters. From the analysis the twist angle of 38 degrees and the solidity of 0.118 are decided to be the optimal geometric parameters for both operating conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.6
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• pp.75-82
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• 2006

Tiltrotor aircraft can fly about twice faster and several times further than conventional helicopters. These aircraft provide advantages preventing compressibility of advancing side and stall of retreating side of blades because they take forward flight with tilting rotor systems. However, they have limit on forward flight speed because of the aeroelastic instability known as whirl flutter. First, the parametric study on the aeroelastic stability of the isolated rotor system has been performed in this paper. And the effects of pitch-link stiffness, gimbal spring constant, and precone angle on the whirl flutter stability of Smart-UAV have been investigated through CAMRAD II analysis.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.64-71
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• 2006

For SUAV is required to have the capacity of VTOL and fast forward flight, the SUAV development program has decided to adopt the tiltrotor mechanism which includes helicopter and turboprop mechanisms. From the engine point of view, the key engine parameters such as engine operating mechanism, engine control scheme, the dynamics characteristic of power train, engine intake/exhaust concept, and engine installation requirements should fulfill the requirements of the two different mechanisms, helicopter and turboprop. And for the maximum efficiency of the rotor, rotational speed for the two modes are 20% different, the power train shall find a way to make it so. Meeting these specific requirements for the tiltrotor mechanism, this research begins with a conventional OTS(off-the-shelf) turboshaft engine survey and minimizes engine modification to develop an economical propulsion system. The engine technical review has been performed on the basis of those requirements and capabilities.

• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.45-55
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• 2023

This study conducted aeromechanics modeling and structural load analyses of Tilt Rotor Aeroacoustic Model (TRAM), a 25% scaled V-22 tiltrotor model used in wind tunnel tests. A rotorcraft comprehensive analysis code, CAMRAD II, was used. Analysis results of this study in low-speed forward flights were compared with DNW test and previous analysis results. Blade flap bending moments were in good agreement with measured data. Mean values and oscillatory loads for lead-lag bending and torsion moments were slightly different from measured data. However, when mean values were removed, results of structural loads for one rotor revolution were moderately compared with wind tunnel tests and previous analyses. Total forces and half peak-to-peak forces of the pitch link reasonably well matched with previous analysis results and measured data. Finally, harmonic magnitudes of blade structural loads were investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.301-307
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• 2005

In this study, simplified whirl flutter analyses using quasisteady aerodynamic theory have been performed for a 2-DOF tilt-rotor system with both pitch and yaw motions of a rotor-nacelle. The present dynamic system consists of the rotor (propeller), forming the gyroscopic and aerodynamic element, supported horizontally by a pylon that is pivoted at some wing attachment point. Several design parameters (or rotor-nacelle system are considered and the effect of whirl flutter stability are also investigated for various design parameters.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.415-421
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• 2006

The unsteady flow calculation around the proprotor of Smart UAV was conducted. Using the flight scenario of SUAV which composed of hover, transition, and airplane mode, the aerodynamic analysis of proprotor were performed for the variation of collective pitch, rpm, forward speed, and tilt angle. The unsteady compressible Navier-Stokes equations were used for the calculation and the dynamic overset grid technique was applied for the rotating proprotor. The aerodynamic performance of proprotor calculated in this way were validated by comparing with the performance data obtained from the blade element momentum method.