Instrumental evaluations (e.g. Dobrzynski, InterNoise 90) showed that propeller noise can be reduced by asymmetrical blade spacing. Compared to conventional propellers with 6 blades and symmetrical spacing of 60°, propellers with asymmetric spacing of 15° produce about 3 dB(A) less level, in particular for high helical blade tip Mach numbers HBTMN. Since the aerodynamic propeller performance is...

Using entropy statistics we analyse scaling patterns in terms of changes in the ratios among product characteristics of 143 designs in civil aircraft. Two allegedly dominant designs, the piston propeller DC3 and the turbofan Boeing 707, are shown to have triggered a scaling trajectory at the level of the respective firms. Along these trajectories different variables have been scaled at differen...

INTRODUCTION There have been increasing reports of annoyance, fatigue, and even neck and back pain during prolonged operation of military propeller aircraft, where persistent multi-axis vibration occurs at higher frequencies beyond human whole-body resonance. This paper characterizes and assesses the higher frequency vibration transmitted to the occupants onboard these aircraft. METHODS Multi...

The Helicopter Adaptive Aircraft (HADA) is a morphing aircraft which is able to take-off as a helicopter and, when in forward flight, unfold the wings that are hidden under the fuselage, and transfer the power from the main rotor to a propeller, thus morphing from a helicopter to an airplane. In this process, the reliable folding and unfolding of the wings is critical, since a failure may deter...

Propeller and rotor based propulsion systems are the dominating choice of power delivery system in upcoming Urban Air Mobility market. Fully electric air-taxis (car sized vehicles with Vertical Take-off Landing, VTOL, capabilities) concepts using benefits scalable properties motors to distribute propulsor units all over airframe. The large variety configurations these poses a serious issue pred...

Composite propellers offer high damping characteristics and corrosion resistance when compared with metal propellers. But the design of a hybrid composite propeller with the same strength of metal propeller is the critical task. For this purpose, the present paper focusses on fluid-structure interaction analysis of hybrid composite propeller with Carbon/Epoxy, R-Glass/Epoxy and S2-Glass/Epoxy t...