Helicopter

Summary

A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft and many forms of short take-off and landing (STOL) or short take-off and vertical landing (STOVL) aircraft cannot perform without a runway. In 1942, the Sikorsky R-4 became the first helicopter to reach full-scale production. Although most earlier designs used more than one main rotor, the configuration of a single main rotor accompanied by a vertical anti-torque tail rotor (i.e. unicopter, not to be confused with the single-blade monocopter) has become the most common helicopter configuration. However, twin-main rotor helicopters (bicopters), in either tandem or transverse rotors configurations, are sometimes in use due to their greater payload capacity than th

Official source

https://en.wikipedia.org/wiki/Helicopter

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Embedded ultra-low power driver for a 7.2g helicopter and IrDA remote control

Patrick Clerc

In a previous project, a 7.2g helicopter made of carbon was designed and realized at the LAI. The goal of this project is to design and realize a tiny receiver and a remote capable of driving the helicopter from a distance of 2 to 4 meters. Challenges are here to make the receiver small and light enough to be embedded in the helicopter without disturbing the flight. Ultra-low consumption is also required. Both emitter and receiver will have to be designed and mounted by the student. The microcontroller is to be chosen in the MSP430F21x2 family. Well-known for their low-power consumption, they also possess an IrDA serial communication interface which will be used for a bi-directional communication between the helicopter and the remote. The remote will have to control 3 channels (lift, yaw and eventually pitch) and display the battery level of the helicopter.

2011

We report a state-prepared, state-resolved study of rotational scattering of a diatomic molecule from a solid surface. Specifically, H-2 molecules with 80 meV kinetic energy are rotationally aligned in the j = 3 rotational state via stimulated Raman pumping and then scattered from a Si(100) surface at normal incidence. The rotational alignment of the scattered molecules is determined by measuring, for both the incident and scattered molecules, the ionization yield of a probe laser, tuned to selectively ionize molecules in the j = 3 rotation level, as the probe laser polarization is rotated. The measurement is performed for two initial rotational alignments: a "helicoptering " alignment with the bonds constrained to lie primarily parallel to the surface and a "cartwheeling " alignment with the bonds lying primarily normal to the surface. For both initial alignments, the modulation of the probe ionization yield with laser polarization for the scattered molecules is pronounced, although significantly weaker than the modulation measured for the incident molecules. This indicates a significant modification but not a complete elimination of the initial alignment. The modulation is found to be stronger for the scattered molecules originating in the cartwheeling alignment than for the helicoptering alignment. These results contribute toward an improved understanding of the role of rotational motion in molecule-surface dynamics.

AIP Publishing2021

Characterisation of blade tip vortices by simultaneous time-resolved velocity and density field measurements

Karen Ann J Mulleners

The flow field around a helicopter is dominated by strong coherent vortices originating from the blade tip as a result of the pressure difference between suction and pressure side and a high radial velocity at the tip (Leishman, 2001; Green and Acosta, 1991). These vortices have a strong impact on the rotorcraft acoustics and performance due to its interactions with the rotor blades and the helicopter fuselage (Conlisk, 2001). Detailed knowledge of the vortex development, in particular of the formation process, and the scaling of characteristic parameters, e.g. vortex size and strength, are necessary for the design and the optimisation of vortex control measures. Due to the complexity and the inherent unsteady character of the vortex dynamics, this can only be achieved by time-resolved measurements of the velocity and density field simultaneously.

2012