Relative velocity gunsight system and method

Claim 1

A method for controlling the gunfire of an aircraft utilizing a headup display comprising the steps of: maneuvering said aircraft to align a target in said headup display; projecting a sighting index on said display; controlling the position of said sighting index on said display so that it appears in the immediate vicinity of said target and moves in the direction and with the velocity that a target appearing at the same relative position on said display would have to have to intercept, one bullet flight-time later, a bullet fired from said aircraft, the motion of said sighting index being defined by the rate of change of traverse and elevation display coordinate angles λ t and λ e as: ##EQU6## additionally maneuvering said aircraft to null the apparent relative motion of said target and said sighting index; and firing said aircraft gun when said relative motion appears to be zero.

Claim 2

A method for controlling the gunfire of an aircraft utilizing a headup display comprising the steps of: maneuvering said aircraft to align a target in said headup display; projecting a sighting index on said display; controlling the position of said sighting index on said display so that it appears in the immediate vicinity of said target and moves in the direction and with the velocity that a target appearing at the same relative position on said display would have to have to intercept, one bullet flight-time later, a bullet fired from said aircraft, the motion of said sighting index being defined by the rate of change of traverse and elevation display coordinate angles λ t and λ e as: ##EQU6## additionally maneuvering said aircraft to null the apparent relative motion of said target and said sighting index; and firing said aircraft gun when said relative motion appears to be zero.

Claim 3

A method for controlling the gunfire of an aircraft utilizing a head-up display comprising the steps of: tracking a target located in the field of view of said display to determine the position of said target relative to said aircraft and to generate position signals describing said position; projecting a first sighting index on said display at a location thereon coincident with said target as viewed in said display; and controlling the position of said first sighting index on said display to move it in accordance with the equation ______________________________________ ##STR11## where --·β= angular rate of the line of sight represented by said sighting index --λ'= position of said target as represented by said position signals T.sub.n = sensitivity in terms of predicted bullet time of flight -a.sub.n = acceleration of said aircraft --S= unit vector along line of sight V.sub.f ' = approximate mean bullet relative velocity with respect to said aircraft ______________________________________ whereby said first sighting index describes the angular velocity of the line of sight to a hypothetical target located at the range of said target and for which λ' is the correct lead angle.

Claim 4

A method for controlling the gunfire of an aircraft utilizing a head-up display comprising the steps of: tracking a target located in the field of view of said display to determine the position of said target relative to said aircraft and to generate position signals describing said position; projecting a first sighting index on said display at a location thereon coincident with said target as viewed in said display; and controlling the position of said first sighting index on said display to move it in accordance with the equation ______________________________________ ##STR11## where --·β= angular rate of the line of sight represented by said sighting index --λ'= position of said target as represented by said position signals T.sub.n = sensitivity in terms of predicted bullet time of flight -a.sub.n = acceleration of said aircraft --S= unit vector along line of sight V.sub.f ' = approximate mean bullet relative velocity with respect to said aircraft ______________________________________ whereby said first sighting index describes the angular velocity of the line of sight to a hypothetical target located at the range of said target and for which λ' is the correct lead angle.

Claim 13

A method for controlling the gunfire of an aircraft utilizing a head-up display comprising the steps of; tracking a target located in the field of view of said display to determine the position of said target relative to said aircraft and to generate position signals describing said position; projecting a first sighting index on said display at a location thereon coincident with the target as viewed in said display; and controlling the position of said first sighting index on said display such that the motion of said sighting index is defined by the rate of change of traverse and elevation display coordinate angles λ t and λ e as: ______________________________________ ##STR13## ##STR14## where K = a constant less than 1 and greater than 0.67 r = yaw rate of said aircraft p = roll rate of said aircraft q = pitch rate of said aircraft λ.sub.t ' = traverse angle of target line of sight λ.sub.e ' = elevation angle of target line of sight T.sub.n = sensitivity in terms of predicted bullet time of flight P.sub.r = precession rate = ##STR15## where A.sub.w = lift acceleration of said aircraft V.sub.f = bullet mean velocity relative to said aircraft V.sub.m = muzzle velocity V.sub.a = true airspeed of said aircraft α.sub.g = gun angle of attack ρ = relative air density ______________________________________ whereby said first sighting index describes the angular velocity of the line of sight to a hypothetical target located at the range of said target and for which λ t ' and λ e ' are the traverse and elevation display coordinate angles of the correct lead angle.

Claim 14

A method for controlling the gunfire of an aircraft utilizing a head-up display comprising the steps of; tracking a target located in the field of view of said display to determine the position of said target relative to said aircraft and to generate position signals describing said position; projecting a first sighting index on said display at a location thereon coincident with the target as viewed in said display; and controlling the position of said first sighting index on said display such that the motion of said sighting index is defined by the rate of change of traverse and elevation display coordinate angles λ t and λ e as: ______________________________________ ##STR13## ##STR14## where K = a constant less than 1 and greater than 0.67 r = yaw rate of said aircraft p = roll rate of said aircraft q = pitch rate of said aircraft λ.sub.t ' = traverse angle of target line of sight λ.sub.e ' = elevation angle of target line of sight T.sub.n = sensitivity in terms of predicted bullet time of flight P.sub.r = precession rate = ##STR15## where A.sub.w = lift acceleration of said aircraft V.sub.f = bullet mean velocity relative to said aircraft V.sub.m = muzzle velocity V.sub.a = true airspeed of said aircraft α.sub.g = gun angle of attack ρ = relative air density ______________________________________ whereby said first sighting index describes the angular velocity of the line of sight to a hypothetical target located at the range of said target and for which λ t ' and λ e ' are the traverse and elevation display coordinate angles of the correct lead angle.