An apparatus and procedure for measuring and regulating the relative vertical displacement of helicopter blades from a rotational plane, comprising a stroboscopic illuminating means, intended to be directed across a reflective tape placed at the extremity of each blade, and a means for controlling the timing of the stroboscopic emissions, whereby the passage of a reflective tape, located at the extremity of each blade, through the line of sight of the lamp, permits a visualization of the relative positions of the different reflecting tapes, the apparatus may be used while on the ground or during flight.
A detector for checking the symmetry of a helicopter rotor while it is rotating has a scanner (11) which scans vertically a field of view (15) and the view is interrupted by a vertical strip on the blade tip (16). A slot (18) in the strip gives a characteristic signal as at (L.sub.2). The position of the signal (L.sub.2) in a scanning cycle gives an indication of the height of the blade tip and also the circumferential spacing between blades.
In a method of detecting the deflection of the blades 13 of a helicopter rotor as it rotates, a beam 14 of radiation from a transmitter/receiver 11 encounters the tips of the rotating blades which send reflected signals to the receiver. The phase difference due to deflection of the blade tip can be used to give a measure of the deflection of each blade, and that can be displayed graphically as shown in FIGS. 7-10 for the various blades at various speeds. In a related method of measuring deflections of the blades 111 for a tail rotor, a laser beam transmitter 16 in FIG. 14 has its reflected beam 122, 123 from an undeflected blade 111 or a deflected blade 111' received by a particular receiver in a linear array 119 of receivers so that the particular receiver gives an indication of the amount of deflection.
A helicopter blade tracking system including an apparatus and method having a self-contained light unit on each blade; each light unit being of similar construction and matched in size and weight. Rings of light formed by the light units during blade rotation are observed by the operator during hover and blade angular position is changed to bring the rings of light into one multi-colored ring of light.
Red, green and white colored lights are emitted from navigation orientation indicating light emitting devices mounted within a helicopter rotor blade near its tip. The light emissions from such devices are under control to respectively indicate passage of the rotor blade through limited arcuate portions of the travel path of the rotor blade end tip. Operational control over the light emitting devices is effected by data processing of outputs from air-speed responsive sensors on the blade end tip.
Visually observable safe limits for the proximity of an aircraft, such as a helicopter, to obstructions are provided by pairs of lights which provide collimated beams intersecting at limit points located radially outwardly of the arc of the helicopter rotor blades so that light scattered from the intersecting beams at the limit points provides the helicopter pilot with visual references of the rotor arc. Each light of each pair has a concave reflector and a lamp at the focal point of the reflector to provide the collimated beams and transparent plastic shields over the open ends of the reflectors have concavities in central portions to provide diverging beams that illuminate the obstructions.
