Alpha-gamma flight path display

Claim 1

An aircraft display instrument for displaying aircraft flight path and a glide slope angle to the pilot, said instrument including a partially reflective combining glass positionable into the pilot''s line of sight to permit the pilot to observe real world objects including a selected touchdown point, and to reflect a projected image into the aforesaid line of sight pilot; a reticle carrier positioned to project first and second reticle images onto said combining glass to be reflected thereby; a plurality of moveable reticles positioned by servomechanisms responsive to signals representing aircraft angle of attack and glide angle; and optical means for projecting at infinity an image of said plurality of reticles upon said combining glass; said plurality of moveable reticles comprising: a first moveable reticle comprising an opaque tape having a transparent numeral scale calibrated in degrees of glide slope angle; a second moveable reticle comprising a backlighted aperture of a width substantially corresponding to the width of said tape of said first reticle, said second reticle having transparent horizontal slots laterally extending from said aperture for projecting a horizontal bar upon said combining glass; said first reticle overlying the backlighted aperture of said second reticle to provide a substantially single focal plane to said optical means, whereby the pilot may direct the aircraft pitch so that the reticle image of the horizontal bar appears across the selected touchdown point, and so that the pilot can adjust the aircraft speed so that the reticle image of the calibrations of a desired glide slope angle may also coincide with the selected touchdown point.