Aircraft terrain and obstacle avoidance systems

• US 5,442,556 A
• Filed: 02/18/1993
• Issued: 08/15/1995
• Est. Priority Date: 05/22/1991
• Status: Expired due to Term

• Current Assignee: Atlantic Inertial Systems Incorporated (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: GEC Marconi Limited (Gooding Consumer Electronics Ltd.)
• Inventors: Hewitt, Charles, Boyes, Jonathan D.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/969,809
• Time in Patent Office: 908 Days
• Field of Search: 364/433, 364/460, 364/454, 364/449, 364/424.01, 364/424.06, 364/427, 364/428, 364/461
• US Class Current: 701/9
• CPC Class Codes: G01C 21/005 with correlation of navigation data from several sources, e.g. map or contour matching G01C21/30 takes precedence
• CPC Class Codes: G08G 5/0021 located in the aircraft
• CPC Class Codes: G08G 5/0086 for monitoring terrain radar or analogous systems specially adapted for terrain avoidance G01S13/935
• CPC Class Codes: G08G 5/045 Navigation or guidance aids, e.g. determination of anti-collision manoeuvers radar or analogous systems specially adapted for anti-collision between aircraft G01S13/933

Abstract

A system for generating, in an aircraft, a warning signal whenever the aircraft is on a potentially hazardous course with respect to the terrain and obstacles thereon imminently to be overflown. The system involves the computation of pull-up trajectories which the aircraft could carry out at a reference point (RP) on the current aircraft flight path (FP) forward of the aircraft current position (CP), taking account of uncertainties of at least aircraft position, which trajectories define collectively a region moving notionally forwardly of the aircraft at a spacing ahead of the aircraft which is a function of aircraft velocity and acceleration and aircraft dynamic response to pilot demands and pilot reaction time, and therefore constitutes a region which the aircraft can imminently overfly. A warning signal is produced if any point on the trajectories has a predetermined relationship with data stored in a map data storage means containing height data relating to the region defined by the trajectories.

Claims

1. A method of generating in an aircraft a warning signal output whenever the aircraft is on a potentially hazardous course with respect to the terrain and obstacles thereon imminently to be overflown, comprises the steps of:

using a navigation system for obtaining values of aircraft current position, attitude, velocity and acceleration, and uncertainties assigned to the current values of at least aircraft position;

storing co-ordinate values of map terrain and obstacle height data in a map data storage means;

using a computer system for determining, repetitively, a multiplicity of hypothetical pull-up trajectory sets, each said set including a hypothetical wings-level pull-up trajectory the length and rate of change of gradient whereof are determined by the aircraft current velocity and acceleration, an aerodynamically safe hypothetical acceleration value, aircraft pitch attitude, and a zero bank angle attitude of the aircraft;

determining where the aircraft has a non-zero bank angle attitude in excess of a predetermined value, at least one additional hypothetical pull-up trajectory notionally extending along the present aircraft flight path, the number of said additional trajectories being determined by the magnitude of the bank angle, and the length and rate of change of gradient of each said additional trajectory being determined by the aircraft current velocity and acceleration, the aerodynamically safe hypothetical acceleration value, the aircraft pitch attitude, and the value of the non-zero bank angle;

notionally collectively determining from said multiplicity of hypothetical pull-up trajectory sets a region of uncertainty of the terrain and obstacles to be imminently overflown determined by said uncertainties, said region moving notionally with the aircraft forwardly thereof with a spacing between the aircraft and a predesignated point within said uncertainty region which is a function involving at least said aircraft present velocity and acceleration, and values for pilot reaction time and aircraft aerodynamic response time to pilot demands;

determining, taking into account uncertainty in aircraft height, whether any of the pull-up trajectories have any point with co-ordinate values having a predetermined relationship with the co-ordinate values stored in the map data storage means in said region; and

developing a warning signal output in the event that such predetermined relationship is determined.

2. A method according to claim 1, wherein said predetermined relationship is that the aircraft height for any point along a trajectory, allowing for uncertainty, is equal to or less than the height data in the storage means relating to a point corresponding to that trajectory point.

3. An apparatus for generating in an aircraft a warning signal output whenever the aircraft is on a potentially hazardous course with respect to terrain and obstacles thereon imminently to be overflown, comprising:

an aircraft navigation system providing outputs representing aircraft present velocity, attitude, and geographical position in three dimensions, and uncertainties assigned to the current values of at least the said aircraft position;

map data storage means adapted to store map terrain and obstacle height data; and

a computer system having;

a first computer sub-system adapted to receive the horizontal aircraft position output from said navigation system and operable to develop outputs defining a notional grid pattern of size and shape dictated by the magnitude of the aforesaid aircraft position uncertainty output, the said grid pattern being notionally in the form of an areal distribution of grid points;

a second computer sub-system adapted to receive from the navigation system said output representative of aircraft present position, velocity and attitude, and operable to develop therefrom outputs representative of the forward displacement of a reference point along aircraft present flight path relative to aircraft present position, the reference point being, notionally, at a pre-designated position within the grid pattern;

a third computer sub-system adapted to receive outputs from the said first and second computer sub-systems and operable to develop outputs representative of the said multiplicity of hypothetical pull-up trajectory sets, each trajectory commencing at an individual said grid point, and the trajectories in each set commencing notionally at the same grid point; and

a fourth computer sub-system adapted to receive outputs from the third computer sub-system, outputs from the map data storage means and a navigation system output defining height uncertainty, and operable to develop a warning output whenever a predetermined relationship is detected between a map data output and any aircraft hypothetical pull-up trajectory vertical position taking into account uncertainty of aircraft height.

4. An apparatus according to claim 3 having a pilot input operable to develop an output which is variable at the will of the pilot within prescribed limits, and which, received by the third computer sub-system, is operable to set the said third computer sub-system to store data corresponding to constants to be employed in the computation of the pull-up trajectories of the said pull-up trajectory sets.