Method and a device for assisting low altitude piloting of an aircraft

Abstract

A method of assisting low altitude piloting of an aircraft and comprising determining at least one main guard curve, determining all of the obstacles present in at least one search zone, and performing a comparison between a top of each obstacle of a search zone and the main guard curve. In order to perform the comparison, if at least one potentially dangerous obstacle is situated above the main guard curve in a search zone, then, for each potentially dangerous obstacle, a sight angle () is determined for the top of the potentially dangerous obstacle, and it is considered that the most dangerous obstacle is the potentially dangerous obstacle presenting the greatest sight angle ().

Claims

1. A method of assisting low altitude piloting of an aircraft, the method comprising: determining, by a processor of a piloting assistance device on-board the aircraft, a main guard curve associated with the aircraft as the aircraft is flying forward in a direction of advance, the main guard curve being determined as a function of predetermined pull-up and pitch-down maneuvering capabilities of the aircraft; determining, by at least one obstacle locating system of the piloting assistance device, all the obstacles present in a search zone of a forward field situated in front of the aircraft; performing, by the processor, a comparison between a top of each obstacle present in the search zone and the main guard curve; wherein when at least one of the obstacles present in the search zone is a potentially dangerous obstacle having a top situated above the main guard curve, determining, by the processor, a sight angle () for the top of each potentially dangerous obstacle; and determining, by the processor, the potentially dangerous obstacle presenting the greatest sight angle () as being a most dangerous obstacle present in the search zone; wherein when no obstacle present in the search zone is a potentially dangerous obstacle having a top situated above the main guard curve, determining, by the processor, a value of a difference criterion for each obstacle present in the search zone representing the difference between the obstacle present in the search zone and the main guard curve, wherein the difference criterion of an obstacle is a height between a top of the obstacle and the main guard curve in a vertical direction; and determining, by the processor, a most dangerous obstacle present in the search zone as being the obstacle present in the search zone having a smallest value of the difference criterion; and communicating, by a display or an alarm of the piloting assistance device, information to a pilot about the most dangerous obstacle present in the search zone.

2. The method according to claim 1, wherein in order to determine the sight angle () for the top of each potentially dangerous obstacle, the following steps are performed by the processor: determining the position of a safety point situated above the potentially dangerous obstacle at a predetermined guard height above the potentially dangerous obstacle; determining a sight angle of the safety point; and setting the sight angle () for the top of the potentially dangerous obstacle as being equal to the sight angle of the safety point.

3. The method according to claim 1, wherein a sight angle of an obstacle is considered as being positive when a point associated with the obstacle and identified by the sight angle of the obstacle is located above a horizontal reference plane containing the aircraft and as being negative when the point associated with the obstacle and identified by the sight angle of the obstacle is located below the horizontal reference plane containing the aircraft.

4. A method of assisting low altitude piloting of an aircraft, the method comprising: determining, by a processor of a piloting assistance device on-board the aircraft, a main guard curve associated with the aircraft as the aircraft is flying forward in a direction of advance, the main guard curve being determined as a function of predetermined pull-up and pitch-down maneuvering capabilities of the aircraft; determining, by at least one obstacle locating system of the piloting assistance device, all the obstacles present in a search zone of a forward field situated in front of the aircraft; performing, by the processor, a comparison between a top of each obstacle present in the search zone and the main guard curve; wherein when at least one of the obstacles present in the search zone is a potentially dangerous obstacle having a top situated above the main guard curve, determining, by the processor, a sight angle () for the top of each potentially dangerous obstacle; and determining, by the processor, the potentially dangerous obstacle presenting the greatest sight angle () as being a most dangerous obstacle present in the search zone; wherein when no obstacle present in the search zone is a potentially dangerous obstacle having a top situated above the main guard curve, determining, by the processor, a secondary guard curve that is offset in time relative to the main guard curve, by being situated at least in part downstream from the main guard curve in the direction of advance of the aircraft; determining, by the processor, a most dangerous obstacle in the search zone as being the obstacle present in the search zone having its top situated the highest relative to the secondary guard curve; and communicating, by a display or an alarm of the piloting assistance device, information to a pilot about the most dangerous obstacle present in the search zone.

5. The method according to claim 1, wherein the forward field situated in front of the aircraft is subdivided into a plurality of search zones, and a most dangerous obstacle is determined for each search zone.

6. The method according to claim 5, wherein a symbol is displayed on the display for the most dangerous obstacle in each search zone and a safety cordon is displayed interconnecting the symbols.

7. The method according to claim 6, wherein a speed vector of the aircraft collimated at infinity is determined and a sign is displayed representing the speed vector on the display, with an alarm being triggered when the speed vector is below the safety cordon.

8. The method according to claim 6, wherein in each search zone the coordinates are determined of a reference point situated at a predefined distance above the top of the most dangerous obstacle in the search zone, the symbol representing the reference point.

9. The method according to claim 1, wherein the main guard curve includes a downstream circular arc presenting a downstream radius equal to the sum of a predetermined minimum pull-up radius plus a predetermined minimum pitch-down radius.

10. The method according to claim 9, further comprising determining a secondary guard curve, wherein the main guard curve and the secondary guard curve present two different respective downstream radii.

11. The method according to claim 9, wherein the main guard curve includes a rectilinear portion upstream from the downstream circular arc, the rectilinear portion extending from a vertical plane containing the aircraft to the downstream circular arc.

12. The method according to claim 1, wherein the main guard curve is constructed from a static guard curve including (i) a downstream circular arc presenting a downstream radius equal to the sum of a predetermined minimum pitch-down radius plus a predetermined minimum pull-up radius and (ii) an upstream circular arc presenting a secondary radius equal to the sum of the predetermined minimum pull-up radius plus a predetermined guard height, the upstream circular arc and the downstream circular arc presenting a common tangent at the point where they join together.

13. A piloting assistance device for use on-board an aircraft, the piloting assistance device comprising: at least one obstacle locating system configured to determine all the obstacles present in a search zone of a forward field situated in front of the aircraft; a processor unit configured to determine a main guard curve associated with the aircraft as the aircraft is flying forward in a direction of advance, the main guard curve being determined as a function of predetermined pull-up and pitch-down maneuvering capabilities of the aircraft; perform a comparison between a top of each obstacle present in the search zone and the main guard curve, when at least one of the obstacles present in the search zone is a potentially dangerous obstacle having a top situated above the main guard, determine a sight angle () for the top of each potentially dangerous obstacle; and determine the potentially dangerous obstacle presenting the greatest sight angle () as being a most dangerous obstacle present in the search zone; when no obstacle present in the search zone is a potentially dangerous obstacle having a top situated above the main guard curve, determine a value of a difference criterion for each obstacle present in the search zone representing the difference between the obstacle present in the search zone and the main guard curve, wherein the difference criterion of an obstacle is a height between a top of the obstacle and the main guard curve in a vertical direction; and determine a most dangerous obstacle present in the search zone as being the obstacle present in the search zone having a smallest value of the difference criterion; and at least one of a display or an alarm configured to communicate information to a pilot about the most dangerous obstacle present in the search zone.

14. An aircraft comprising: at least one obstacle locating system configured to determine all the obstacles present in a search zone of a forward field situated in front of the aircraft; a processor unit configured to determine a main guard curve associated with the aircraft as the aircraft is flying forward in a direction of advance, the main guard curve being determined as a function of predetermined pull-up and pitch-down maneuvering capabilities of the aircraft; perform a comparison between a top of each obstacle present in the search zone and the main guard curve, when at least one of the obstacles present in the search zone is a potentially dangerous obstacle having a top situated above the main guard curve, determine a sight angle () for the top of each potentially dangerous obstacle; and determine the potentially dangerous obstacle presenting the greatest sight angle () as being a most dangerous obstacle present in the search zone; when no obstacle present in the search zone is a potentially dangerous obstacle having a top situated above the main guard curve, determine a secondary guard curve that is offset in time relative to the main guard curve, by being situated at least in part downstream from the main guard curve in the direction of advance of the aircraft; and determine a most dangerous obstacle present in the search zone as being the obstacle present in the search zone having its top situated the highest relative to the secondary guard curve; and at least one of a display or an alarm configured to communicate information to a pilot about the most dangerous obstacle present in the search zone.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The invention and its advantages appear in greater detail from the context of the following description of implementations given by way of illustration and with reference to the accompanying figures, in which:

(2) FIG. 1 is a diagram of an aircraft of the invention;

(3) FIG. 2 is a diagram showing the main guard curve in a first implementation;

(4) FIG. 3 is a diagram showing the main guard curve in a second implementation;

(5) FIG. 4 is a diagram showing the comparison of an obstacle with the main guard curve as established in a first implementation;

(6) FIG. 5 is a diagram showing the comparison of an obstacle with the main guard curve as established in a second implementation;

(7) FIG. 6 is a diagram showing the comparison of an obstacle that is not potentially dangerous with the main guard curve established in the first implementation;

(8) FIG. 7 is a diagram showing a method making use of a main guard curve and of a secondary guard curve; and

(9) FIGS. 8 and 9 are diagrams showing the information transmitted to a pilot on a display.

(10) Elements present in more than one of the figures are given the same references in each of them.

DETAILED DESCRIPTION OF THE INVENTION

(11) FIG. 1 shows an aircraft 1 of the invention. For example, the aircraft 1 is a rotorcraft.

(12) The aircraft 1 includes a piloting assistance device 2 for facilitating flight at low altitude. This piloting assistance device 2 includes at least one locating system for locating obstacles.

(13) Under such circumstances, the piloting assistance device may include a locating system 3 of the database type. Such a database usually stores a list of obstacles and their locations. Such databases are commercially available.

(14) As an alternative or in addition, the piloting assistance device may include a telemeter 4. For example, the aircraft 1 may be fitted with a telemeter of the kind known under the acronym Lidar. A telemeter serves in particular to measure the bearings and the distances for all obstacles situated in at least one search zone.

(15) Furthermore, the piloting assistance device includes a processor unit 5, which is connected to each locating system.

(16) The processor unit is provided with computer means 6, such as a processor, for example. Furthermore, the processor unit includes a memory 7. The memory 7 may comprise one or more storage means. The memory 7 contains instructions executed by the computer means in order to perform the method of the invention.

(17) Thus, the processor unit determines all obstacles that are present in at least one search zone by using data transmitted over a wired or wireless connection by the locating systems. Furthermore, the processor unit establishes at least one main guard curve associated with the aircraft.

(18) In addition, an alarm system 9 is connected to a display 8 or to the processor unit 5. Such an alarm system may generate an alarm that is audible, visible, and/or tactile, for example.

(19) FIG. 2 shows a guard curve established in a first implementation.

(20) Independently of the implementation, the aircraft 1 travels in a direction of advance 50 with a speed vector 40. The maneuver for enabling the aircraft 1 to avoid an obstacle consists in a pull-up maneuver followed by a pitch-down maneuver to return to a guard height Hg above the obstacle 100. By applying maximum load factors for pulling up nc and for pitching down np, the optimum path T1 is made up of two circular arcs of respective radii Rc and Rp.

(21) Under such circumstances, the processor unit determines, at each computation instant, at least one main guard curve associated with the aircraft. The main guard curve 20 is defined as being the curve for which the aircraft flying on its current path will avoid obstacles that are situated externally (EXT) relative to the guard curve, and for which the aircraft flying on its current path needs to maneuver in order to avoid obstacles that are situated internally (INT) relative to the guard curve. Consequently, an obstacle situated above the guard curve represents an obstacle that is potentially dangerous.

(22) The term above means that an item is situated above another item in the vertical gravity direction. Thus, the term obstacle situated above the guard curve means an obstacle that is situated higher than and over the guard curve.

(23) Independently of the implementation, the guard curve presents a downstream circular arc 21. This downstream circular arc presents a downstream radius R1 equal to the sum of a predetermined minimum pull-up radius Rc and a predetermined minimum pitch-down radius Rp for the aircraft.

(24) The predetermined minimum pitch-down radius Rp and the predetermined minimum pull-up radius Rc may be respectively defined by way of example by the following relationships:

(25) $\mathrm{Rc}=\frac{V^2}{g*\left(\mathrm{nc}-1\right)}$$\mathrm{Rp}=\frac{V^2}{g*\left(1-\mathrm{np}\right)}$
in which V is the speed of the aircraft, g is the acceleration due to gravity, Rc is the pull-up radius of curvature, Rp is the pitch-down radius of curvature, nc is a maximum pull-up load factor, and np is a maximum pitch-down load factor.

(26) In the first implementation, the main guard curve 20 has a rectilinear portion 22 upstream from the downstream circular arc 21. This rectilinear portion 22 extends from a vertical plane P1 containing the aircraft 1 as far as the downstream circular arc 21 over a warning length P.

(27) The main guard curve may be positioned at a guard height Hg under the aircraft.

(28) Such a guard curve may be established in application of the teaching of Document FR 2 712 251.

(29) In the second implementation of FIG. 3, the main guard curve 20 is constructed from a static guard curve 30 including an upstream circular arc 23 presenting a secondary radius R2. This secondary radius R2 is equal to the sum of the predetermined minimum pull-up radius Rc plus a predetermined guard height Hg. Under such circumstances, the upstream circular arc 23 and the downstream circular arc 21 present a common tangent 300 at the point 301 where they join together.

(30) The main guard curve is the locus of points situated at a normal distance D from the static guard curve and satisfying the relationship:

(31) $D+=\frac{dD}{dt}=0$
where is a predetermined warning time and

(32) $\frac{dD}{dt}$
is the derivative of D relative to time.

(33) This main guard curve may move together with the aircraft under conditions that depend on the successive orientations of the speed vector during flight. For example, while the aircraft is pulling up, the guard curve remains stationary. The aircraft is then capable, while continuing its pull-up movement to a greater or lesser extent, of passing over any obstacle that is external relative to the static guard curve.

(34) In contrast, as soon as the aircraft begins a pitch-down path, the guard curve pivots with the aircraft.

(35) Such a guard curve is also referred to as a dynamic guard curve and it may be established in application of the teaching of Document FR 2 886 439.

(36) With reference to FIGS. 4 and 5, the processor unit performs a comparison by comparing the top 110 of each obstacle 100 in a search zone with the main guard curve 20. Among the obstacles 100 identified by the locating system, the processor unit determines the obstacle 130 that is said to be the most dangerous.

(37) The processor unit determines in particular the coordinates of the top 110 of the obstacles 100, and then determines the positions of these tops, at least relative to the main guard curve 20.

(38) If an obstacle 100 has a top 110 situated above the main guard curve 20, and thus internally INT relative to the main guard curve 20, then the obstacle is a potentially dangerous obstacle 120. FIG. 4 shows a first obstacle 101 and a second obstacle 102, each of which represents a potentially dangerous obstacle 120.

(39) Under such circumstances, the processor unit determines the sight angle for each potentially dangerous obstacle 120 that is detected.

(40) The processor unit then considers that the potentially dangerous obstacle 120 having the greatest sight angle constitutes the most dangerous obstacle 130 that needs to be taken into consideration for directing the aircraft.

(41) In a first variant, the sight angle of an obstacle may be established by determining the angle between a horizontal reference plane P0 containing the aircraft 1 and a straight line passing from said aircraft 1 to the top 110 of the obstacle.

(42) In this variant, the first obstacle 101 presents a first sight angle 1 and the second obstacle 102 presents a second sight angle 2.

(43) By convention, each sight angle of an obstacle is said to be positive when a point associated with the obstacle and identified by the sight angle lies above the horizontal reference plane P0 containing the aircraft 1, and negative when it is below the reference plane.

(44) Under such circumstances, the first sight angle 1 has a negative value and the second sight angle 2 has a positive value. As a result, the second obstacle 102 presents a second sight angle that is greater than the first sight angle of the first obstacle. Consequently, the second obstacle constitutes the most dangerous obstacle 130.

(45) In a second variant, in order to determine the sight angle of a potentially dangerous obstacle:

(46) the processor unit determines the position of a safety point 140 situated above the potentially dangerous obstacle at a predetermined guard height Hg above the potentially dangerous obstacle 120; and

(47) the processor unit determines a sight angle of said safety point, said sight angle of the potentially dangerous obstacle then being equal to said sight angle of said safety point.

(48) As shown in FIG. 4, the first obstacle 101 presents a first sight angle 11 and the second obstacle 102 presents a second sight angle 21.

(49) Under such circumstances, the first sight angle 11 has a small positive value and the second sight angle 21 has a large positive value. As a result, the second obstacle 102 presents a second sight angle that is greater than the first sight angle of the first obstacle. Consequently, the second obstacle constitutes the most dangerous obstacle 130.

(50) FIG. 5 shows the described method being applied with a primary guard curve that is established in the second implementation.

(51) With reference to FIG. 6 and in a first alternative, if no obstacle is a potentially dangerous obstacle 120, a value for a different criterion 200 is determined for each obstacle 100, which value represents a difference 201 between the obstacle 100 and the main guard curve 20. The most dangerous obstacle 130 is then the obstacle presenting the smallest difference criterion 200.

(52) The difference criterion 200 may for example be a height between the top 110 of the obstacle 100 and the main guard curve 20 in a vertical direction AX.

(53) FIG. 6 shows a main guard curve in the first implementation. Nevertheless, the first alternative is applicable to the second implementation.

(54) In the second alternative of FIG. 7, the processor unit determines a secondary guard curve 25 that is offset in time relative to the main guard curve 20.

(55) The secondary guard curve 25 is thus situated at least in part downstream from the main guard curve 20 in the direction of advance 50 of the aircraft 1.

(56) Under such circumstances, if no obstacle constitutes a potentially dangerous obstacle situated above the main guard curve, then the most dangerous obstacle 130 represents the obstacle having its top 110 situated the highest relative to the secondary guard curve 25.

(57) In the example of FIG. 7, a first obstacle 103 is situated at a first height H1 above the secondary guard curve 25. However, a second obstacle 104 is situated at a second height H2 below the secondary guard curve 25.

(58) As a result, the first height H1 has a positive value and the second height has a negative value. The first obstacle 103 then represents the most dangerous obstacle 130.

(59) FIG. 7 shows a main guard curve and a secondary guard curve in application of the first implementation. Nevertheless, the first alternative is applicable to the second implementation.

(60) Likewise, the main guard curve and the secondary guard curve could be different.

(61) Furthermore, and independently of the alternative that is applied, in the absence of any obstacle, the ground may represent the obstacle that is the most dangerous.

(62) With reference to FIG. 8, the forward field 30 situated in front of the aircraft may be subdivided into a plurality of search zones 35. For example, the forward field is subdivided into four angular sectors forming four search zones 35, namely a first search zone 31, a second search zone 32, a third search zone 33, and a fourth search zone 34.

(63) The processor unit then determines the most dangerous obstacle in each of the search zones.

(64) Furthermore, the processor unit provides a pilot with information about the most dangerous obstacle in each search zone.

(65) Thus, the processor unit is connected to a display 8.

(66) As a result, the processor unit causes the display 8 to display a symbol 65 in association with each most dangerous obstacle 130. Each symbol 65 thus represents the most dangerous obstacle 130 in a given search zone 35.

(67) Furthermore, the processor unit may cause a safety cordon 80 to be displayed interconnecting said symbols 65.

(68) With reference to FIG. 9, the display 8 may display by way of example a representation of the external landscape. The display superposes each symbol 65 on this representation.

(69) Each symbol 65 may be positioned at the top of the most dangerous obstacle shown.

(70) In another obstacle, in each search zone 35, the processor unit determines the coordinates of a reference point 66 situated at a predefined distance 67 above the top 110 of the most dangerous obstacle 130. The symbol 65 then represents the reference point 66.

(71) In order to facilitate piloting the aircraft, the processor unit determines a speed vector 40 of the aircraft 1 collimated at infinity, by using appropriate members of the aircraft. The processor unit then displays a sign 75 representing this speed vector 40 on the display 8.

(72) Furthermore, the piloting assistance device may trigger an alarm when the speed vector 40 lies below the safety cordon 80, as in the example shown.

(73) The display options of Document FR 2 712 251 are also applicable in the present invention.

(74) Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several implementations are described, it will readily be understood that it is not conceivable to identify exhaustively all possible implementations. It is naturally possible to envisage replacing any of the means described by equivalent means without going beyond the ambit of the present invention.