Rotorcraft experiences high level of vibration as its cruise speed increases. When the number of main rotor blade is N, N/rev vibration dominates relative to vibrations at other frequencies. To reduce that vibration, CG offset in the x-y plane from the baseline position was introduced in the previous study. The authors have analytically examined the effect of CG positions on the vibration of SH-60K as an example helicopter. SH-60K is a mid-sized helicopter which has 4-bladed articulated rotor. It has been revealed that when the CG moves toward right and also backward from the baseline position, the 4/rev vibration reaches 40% of the baseline vibration. This article discusses about the effect of SH-60K CG positions on its inherent stability. This discussion about the inherent stability restricts the CG offset. By considering the limitation of the CG offset, the vibration decrease owing to the CG offset is limited up to 20%.

In this paper, an active cooling method for an array of tiles laid with gaps over the surface of a hypersonic vehicle was proposed and investigated by both the Navier-Stokes analysis and the wind tunnel experiment at Mach number 7 in Kashiwa campus, the University of Tokyo. In this method, the cold air is injected in the upstream direction from a slit set on the wall of the tile gap. The slit is parallel to the surface and is located at the intersection of the lateral and longitudinal gaps. The numerical and experimental results show that the peak heating at the corner of the forward-facing gap wall is successfully suppressed by the injection. The mechanism of the gap heating suppression was clarified in the numerical study by detailed observation of the flow field near the surface and in the cavity.

This paper investigates the influence on aerodynamic performance of the rotor/winged-body configuration due to change of advance ratio and the lift share ratio between a rotor and a wing through numerical simulations. A computational model of compound helicopter is constructed with a main rotor of UH-60A helicopter and a winged-body configuration where the fuselage is designed by JAXA and the wing is rectangular. Flight conditions at various cruising speed corresponding to an advance ratio of 0.1 to 0.7 is simulated. As a result, the flow around the wing is deflected in a direction of decreasing angle of attack. This trend becomes stronger as the advance ratio decreases. The lift share of the rotor increases between 0.05 and 0.08 at the advance ratio of 0.1 to 0.7. The total effective drag coefficient increases due to the aerodynamic interaction, the increase of the rotor effective drag coefficient is greater than that of the winged-body. The drag coefficient of the wing of the winged-body becomes negative at the advance ratio of 0.1 and 0.15. The rotor effective drag coefficient and the winged-body drag coefficient increase significantly at high advance ratio. Therefore, the total effective lift-to-drag ratio decreases as the advance ratio increases, and it decreases by 18% at the advance ratio of 0.7. In addition, the advance ratio of the maximum total lift-drag ratio is smaller than that designed without aerodynamic interaction between the rotor and wing-body.

To verify the applicability of UTCart (a compressible flow solver based on the hierarchical Cartesian grid method) to high Reynolds number flows, a flow field analysis around a commercial airliner at cruise was conducted. The analysis is performed in the range of Reynolds number from that in general wind tunnel tests to the flight Reynolds number, and the reproducibility of the Reynolds number effect is verified through comparison with the results in the high Reynolds number wind tunnel tests. The simulations were able to reproduce the Reynolds number effects (lift coefficient increase and drag coefficient decrease, etc.) observed in the wind tunnel tests.

Deployable flexible aeroshells have the potential to innovate atmospheric entry systems and space transportation technology. This study constructed and validated a shape measurement system for deployable flexible aeroshells during low-speed wind tunnel ventilation. The system consists of two Time of Flight (ToF) cameras with a wide measurement range and a high sampling rate. By software control, these can simultaneously capture and store depth images at 30 fps. A post-analysis method for ToF camera data with moving objects is proposed, and the obtained front projected area of the flexible aeroshell was verified. The proposed method could provide reasonable results and adapt to the object's position changes without readjusting parameters. The front projected area of the flexible aeroshell estimated from the ToF measurement data was consistent with trends that can be visually observed and with the results of structural strength tests. A positive correlation between aerodynamic forces and the front projected area was also confirmed.

In this paper, we describe two issues that have been discovered during the design of a flight control system of Mars airplane and an experimental vehicle. The first issue is that both, the experimental and Mars aircraft, easily tend to entry to the backside region. This has been observed even at higher speeds and lower angle of attack than in conventional aircraft due to different flight environments and aerodynamic characteristics. The second issue arises due to the aircraft being lightweight and able to fly at high cruising speeds. This results in a high natural frequency of short period mode. Due to this high natural frequency, usually negligible time delay effects have a significant effect. Therefore, the phase margin of the system decreases and its control performance tends to deteriorate.