Results 191 to 200 of about 30,315 (234)

Model helicopter rotor impulsive noise

Journal of Sound and Vibration, 1981
An investigation of helicopter rotor blade slap was performed on a 1·27 m diameter model rotor. The rotor blades were a NACA 0012 section with a −8° linear twist. The experiments were conducted in the M.I.T. Anechoic Wind Tunnel. The effects of number of blades, blade pitch, advance ratio, and shaft angle on the generation and intensity of blade slap ...
J.E. Hubbard, W.L. Harris
openaire   +1 more source

Rotational Noise of Helicopter Rotors

The Journal of the Acoustical Society of America, 1965
An analysis procedure has been developed to predict propeller rotational noise during nonuniform, as well as uniform, inflow conditions. Although many studies have been conducted since the development of Gutin's equations (NACA TM I195), none have been developed that adequately describe the near and far rotational-noise fields of a helicopter rotor ...
Robert King, Ronald G. Schlegel
openaire   +1 more source

The Stiff‐hinged Helicopter Rotor

Aircraft Engineering and Aerospace Technology, 1955
THE continual development of helicopter rotor systems has so far resulted in the use of about six main types, and it will be of value briefly to recapitulate their advantages and disadvantages in order to obtain a balanced picture against which the stiff‐hinged rotor can be judged.
openaire   +1 more source

HELICOPTER ENGINE-ROTOR SYSTEM COMPATIBILITY

2017
<div class="section abstract"> <div class="htmlview paragraph">This SAE Aerospace Recommended Practice (ARP) recommends a methodology to be used for the design, analysis and test evaluation of modern helicopter gas turbine propulsion system stability and transient response characteristics. This methodology utilizes the computational power
openaire   +2 more sources

Composite-Material Helicopter Rotor Hubs

1973
Abstract : This report describes the development work for construction of helicopter rotor hubs from fibrous composite materials. The prototype hubs were designed to be structurally and functionally equivalent to the metallic hub used on the Sikorsky CH-54B HELICOPTER.
openaire   +1 more source

Rotor Dynamics and Helicopter Stability

Aircraft Engineering and Aerospace Technology, 1963
The component of velocity, μ0ΩR, along the x‐axis is specified, and also X, the angle of inclination of the flight path. The concept of the ‘internal’ and ‘external’ parameters of the motion is introduced, the ‘internal’ parameters consisting of certain combinations of the control and flapping angles θ0, θ1, θ2, β0, β1, β2 and the ‘external ...
openaire   +1 more source

Helicopter Rotor Blade Radar Antenna

Journal of the American Helicopter Society, 1966
The helicopter main rotor blade can be used as a scanning radar antenna. Its large aperture gives a narrow azimuth beam‐width and the natural rotor scanning motion provides a fast scan. It is much lighter than conventional antennas and since it is integral with the rotor blade, it induces no additional drag.
openaire   +1 more source

Advances in Helicopter Rotor Technology

2004
Since the beginning of the helicopter development (see “First Helicopters and Rotor Systems”) there was a need to place hinges and bearings as close to the rotor center as possible to guarantee low rotor stiffness and hence good control characteristics at low cabin vibrations.
openaire   +1 more source

Research on Helicopter Rotor Noise

1978
Abstract : Research was conducted on aspect of noise generation by helicopters. A general review of helicopter noise was prepared and published as one part of the work. Methods were developed for the analysis of high frequency broadband noise from rotors.
openaire   +1 more source

Failure of a Helicopter Rotor

2019
Abstract Helicopter rotor blade components that included the horizontal hinge pin, the associated nut, and the locking washer were examined. Visual examination of the submitted parts revealed that the hinge pin, fabricated from 4340 steel, was broken and that the fracture face showed a flat beach mark pattern indicative of a preexisting ...
openaire   +1 more source