Aircraft head up display system

An aircraft head up display system operably configured to display an aircraft unusual attitude, said head up display system operating in modes comprising:

• a basic display mode, an en route display mode, or an approach/landing display mode;
• an unusual attitude display mode, said head up display system switching from the basic display mode, the en route display mode, or the approach/landing display mode to the unusual attitude display mode when an aircraft predefined unusual attitude limit is exceeded;
• and
• a display for displaying the basic display mode, the en route display mode, the approach/landing mode, or the unusual attitude display mode, and wherein the display in the unusual attitude display mode displays an air speed indicator, an altitude indicator, and an attitude indicator, wherein the attitude indicator includes
• an unusual attitude ball display sized to occupy a substantial portion of a display field of view,
• a horizon symbol indicating a horizon, said horizon symbol comprising a straight line that forms a movable and rotatable chord of the unusual attitude ball display,
• a series of simulated section lines angularly spaced apart and generally converging toward the horizon symbol with one of said section lines being a center line perpendicular to the horizon symbol and the remaining simulated section lines symmetrically arranged about the center line, said series of simulated section lines being displayed in an area of the unusual attitude ball display below the horizon symbol indicating an area below the horizon, and
• a pitch ladder for indicating aircraft degrees of pitch, said pitch ladder further comprising a series of steps spaced apart in predetermined pitch increments with numerals indicating the predetermined pitch increment adjacent each of the series of steps, each of said steps being a line perpendicular to the center line in the series of simulated section lines,
• wherein the attitude indicator truncates the pitch ladder to preserve a predetermined minimum length of the horizon symbol when the pitch of the aircraft is such that the horizon symbol would otherwise disappear from the display.

An aircraft head up display system, which changes from a basic display mode, an en route display mode, or an approach/landing display mode to an unusual attitude display mode when a predefined unusual aircraft attitude limit is exceeded, comprising a display, said display in the unusual attitude display mode further comprising:

• an air speed indicator;
• an altitude indicator;
• and
• an attitude indicator located between the air speed indicator and the altitude indicator on the display, said attitude Indicator further comprising:
• an unusual attitude ball display sized to occupy a substantial portion of a display field of view;
• a horizon symbol indicating a horizon, said horizon symbol comprising a straight line that forms a movable and rotatable chord of the unusual attitude ball display;
• a series of simulated section lines angularly spaced apart and generally converging toward the horizon symbol with one of said section lines being a center line perpendicular to the horizon symbol and the remaining simulated section lines symmetrically arranged about the center line, said series of simulated section lines being displayed in an area of the unusual attitude ball display below the horizon symbol indicating an area below the horizon;
• and
• a pitch ladder for indicating degrees of aircraft pitch, said pitch ladder further comprising a series of steps spaced apart in predetermined pitch increments with numerals indicating the predetermined pitch increment adjacent each of the series of steps, each of said steps being a line perpendicular to the center line in the series of simulated section lines;
• wherein the attitude indicator truncates the pitch ladder to preserve a predetermined minimum length of the horizon symbol when the pitch of the aircraft is such that the horizon symbol would otherwise disappear from the display.