Helicopter visual-positioning aid

Claim 1

Apparatus for providing the pilot of a helicopter with a visual reference in order to facilitate his maneuvering the helicopter to a point above a desired surface area such as the deck of a ship at sea, and for enabling him to maintain the helicopter centered at such point above said surface area, said apparatus comprising: a first visual-aid unit mounted on or near said surface area, said first visual-aid unit having an optical axis which passes through said point at which the pilot of said helicopter desires to maintain his craft, said visual-aid unit having a predetermined appearance to said pilot when the latter views such unit along its optical axis, which appearance is different from that which it possesses when viewed from a location other than along its optical axis; a second visual-aid unit also mounted on or near said surface area and spaced apart from said first visual-aid unit, said second visual-aid unit also having an optical axis which passes through said point at which the pilot of said helicopter desires to maintain his craft, said second visual-aid unit being similar to said first visual-aid unit in that it has a predetermined appearance to said pilot when the latter views such unit along its optical axis which is different from its appearance when viewed by said pilot from a location other than along its optical axis; each of said first and second visual-aid units comprising a planar background display panel member lying normal to the optical axis of such unit, and a further target panel member layIng above and parallel to said background display member, said target panel member being of lesser area than said background panel member and being symmetrically arranged with respect thereto along said optical axis; each of said panel members being rectangular in configuration; each of said target panel members being of a particular color, with a surface of said background display member corresponding to the area of said target panel member being of a different particular color, such differently colored area of said background display member being obscured from the view of the pilot of said helicopter when the latter is at a point along the optical axis of such visual-aid unit; the remaining surface area of said background panel member outside of that corresponding to the area of said target panel member being so colored that, upon the visual-aid unit being viewed from a location other than along its optical axis, the appearance thereof will not only indicate to the viewer that he is off the said optical axis but will also indicate both the direction of such departure and the magnitude thereof, providing that both quantities are within the limits of the unit; further comprising means for stabilizing each of said visual-aid units at least in part when the surface area on which they are mounted is subJect to limited positional displacements; and at least one light source mounted on the rear surface of said target panel member and designed to illuminate the front surface of said background display member, the pilot of said helicopter thus being assured, after maneuvering his helicopter so that each of said two visual-aid units presents its said predetermined appearance, that he is at the intersection of the respective optical axes of such units and hence that the helicopter is centered at the desired point above said surface area.