GB2164905A

GB2164905A - Device for the automatic control of an aerodynamic trimmer associated with an aerodynamic control surface of an aircraft

Info

Publication number: GB2164905A
Application number: GB08523633A
Authority: GB
Inventors: Jacques Poccard
Original assignee: Airbus Group SAS
Current assignee: Airbus Group SAS
Priority date: 1984-10-02
Filing date: 1985-09-25
Publication date: 1986-04-03
Also published as: GB2164905B; GB8523633D0; DE3534611A1; ES8703373A1; FR2571021B1; ES548100A0; FR2571021A1

Abstract

An aerodynamic trimmer (9) is articulated on the rear of an aerodynamic control surface (8) (e.g. a rudder) which is itself articulated on the structure (6) of an aircraft. A rod (19) articulated on said trimmer (9) is connected to the aircraft structure (6) through a lever (12), itself articulated on said structure (6) of the aircraft and having a point of articulation (11) with the rod (19) remote from the trimmer, so that an angular displacement of the control surface (8) automatically leads to the angular displacement of said trimmer (9) relative to said control surface (8). Cam means (14) are provided to displace the point of articulation (11) of the rod (19) and lever (12) in a direction at least approximately transverse to said aerodynamic surface (8), in conjunction with the controlled angular displacement of said surface. Movable ramps (23) may be mounted on the cam (14) and deployed to modify the cam profile and thus the movement of the trimmer (9) relative to the surface (8), in say the event of an engine failure in a twin engined aircraft. <IMAGE>

Description

SPECIFICATION Device for the automatic control of an aerodynamic trimmer associated with an aerodynamic control surface of an aircraft The present invention relates to a device for the automatic control of an aerodynamic trimmer associated with an aerodynamic control surface of an aircraft, particularly a rudder.

For reasons of stability, of control and of equilibrium, it is already known to associate with an aerodynamic control surface of an aircraft, such as an aileron, an elevator or a rudder for example an aerodynamic trimmer itself consisting of a flap articulated on said aerodynamic surface, at the trailing-edge, and capable of assuming either an aligned position or oblique positions in relation to said aerodynamic surface. It is likewise known to provide devices for the automatic control of said trimmers from the movement imposed on said aerodynamic surface by the pilot. Such devices generally consist of a linkage articulated on the structure on which said aerodynamic surface is itself articulated.Examples of aerodynamic trimmers and of their control mechanisms are described, for example, in the documents US-A-2 094 488, US-A-2 252 284, US-A-2 357 465, US-A-2 435 922, US-A-2 557 426, US-A-2 743 889, US-A-3 000 595, US-A-3 261 573, and US-A-3 295 797.

In these known devices, the variation in the angle of the trimmer in relation to the aerodynamic surface is generally a linear function of the angle of displacement of the aerodynamic surface.

Sometimes, this function is not linear so as to be able to ensure an increased balancing force when the angle of the aerodynamic surface increases.

The present invention relates to a device of the type described above which can enable at least some of the following conditions to be satisfied, in particular when it is associated with a rubber: (1) to provide sufficiently powerful aerodynamic balancing of the full angular movement of the rudder, at low speed, to ensure the control of the aircraft according to the standard criteria, in the event of engine failure or take-off or of opening out the engine again when landing on a single engine, without demanding physical effort from the pilot greater than is defined by the standard;; (2) to provide sufficiently powerful aerodynamic balancing to permit, at low speed, the movement of the control surface necessary to obtain stabilized side-slipping flight to ensure the control of the aircraft in accordance with the standard criteria in the event of landing or taking off with a strong cross wind, without demanding from the pilot effort greater than is defined by the standard; (3) to maintain forces in the correct direction on the controls in the entire flight envelope; (4) not to lead to the structural strength of the aircraft being exceeded in the entire flight envelope through excessive movement of the control surface when the forces specified by the standard are applied to the controls;; (5) not to lead to an irreversible catastrophic situation in the event of the temporary application of a control instruction in the opposite direction to the required direction in the case of an engine failure; (6) to ensure homogeneous forces in normal symmetrical cases of flight permitting a satisfactory return of the control surface to zero when no force is applied to the controls.

It is known that such conditions are the more difficult to meet, the greater the size of the aircraft, the variations in speed and the asymmetry in flight. Such asymmetry appears, in particular, in multi-engined aircraft when one or more engines from one side break down while propulsion remains assured by the engine or engines from the other side.

For these purposes, according to the invention, the device for the automatic control of an aerodynamic trimmer articulated on the rear of an aerodynamic control surface of an aircraft, itself articulated on the structure of said aircraft, comprises a rod articulated on said aerodynamic trimmer and connected to the structure of the aircraft in such a manner that a controlled movement of said aerodynamic control surface automatically results in the angular deflection of said aerodynamic trimmer in relation to said aerodynamic control surface, remote from its articulation on the aerodynamic trimmer said rod being articulated on a lever that is itself articulated on said structure of the aircraft, and means being provided to displace the point of articulation of the rod and of the lever in a direction at least approximately transverse to said aerodynamic surface, in conjunction with the controlled movement of said aerodynamic surface.

Thus said displacement means enable a desired law of variation to be given to the rate of automatic operation of the device (ratio of angular deflection of the trimmer and of the angular deflection of the control surface).

The point of articulation of the rod and of the lever is preferably at least approximately in the transverse plane passing through the axis of rotation of the aerodynamic control surface on the structure of the aircraft, and in an eccentric position in relation to said axis.

In an advantageous form, the displacement means for said point of articulation comprises a cam which is articulated on the structure of the aircraft, which is rigidly connected to said aerodynamic control surface for rotation therewith, and against which said lever bears.

Thus the non-linear variation in the proportion of automatic operation is imposed by the profile of said cam.

The profile of this cam can be designed in such a manner as to achieve, in the domain of symmetrical flight: -a reduced rate of automatic operation in the vicinity of the neutral position of the control surface, with the object of improving the return of the surface to its neutral position; -an increased rate of automatic operation at a sufficient level to enable the angular movement of a rudder to be obtained corresponding to the stabilized side-slip necessary against a cross wind on take-off and landing (angular movement about half the maximum angular movement of the rudder). This value of the rate of automatic operation enables stabilized side-slip to be obtained at low speeds with control forces according to the standard and ensures a limitation of the side-slip at high speed through saturation of force.

-a rate of automatic operation which then decreases down to zero at the maximum angular deflection of the control surface, which eliminates the reversal of the forces at the controls on high angular deflection of the control surface with strong side-slip.

The arrangement of the lever and of the cam may advantageously be such that the lever is applied against said cam by the aerodynamic forces acting on the control surface.

Nevertheless, resilient means are preferably also provided to press said lever against said cam.

In an advantageous form, the profile of said cam can be modified by means of movable ramps mounted on said cam.

Thus, inthe event of asymmetrical engine failure, the profile of the cam can be modified by the displacement of one or the other of said movable ramps, which has the effect of causing the rate of automatic operation to increase to a maximum for the maximum angular deflection of the rudder but only at the side of for an angular deflection to the side opposite to the engine failure that has occured.

It is then possible to obtain the maximum angular deflection of the rudder to the side in question with forces at the controls corresponding to the standard, while avoiding the risk of a reversal of force in the event of an action by the pilot exerted in the wrong direction.

The displacement of one or the other of the movable ramps may be effected by an electric actuator which is controlled by an engine-failure signal discriminated according to the position of said failed engine on the left or on the right. The retraction of the ramp is obtained when the engine-failure signal disappears.

The figures of the accompanying drawings exemplify how the invention may be carried out. In these figures, corresponding references designate similar elements.

Figure 1 shows diagrammatically the outline of a twin-engine aircraft provided with the device according to the invention.

The diagrams a b, c, d and e of Figure 2 illustrate diagrammatically different positions of the fin, of the rudder and of the aerodynamic trimmer associated with the aircraft of Fig. 1 in normal flight.

The diagrams g and f of Figure 3 illustrate diagrammatically two relative positions of the fin, of the rudder and of the associated aerodynamic trimmer, in flight with one engine failed.

Figure 4 enables the angles involved in the definition of the rate of automatic operation of the device to be defined.

Figures 5, 6 and 7 illustrate the variations in the rate of automatic operation in dependence on the angular deflection of the rudder, in flight with the two engines and with one of said engines failed respectively.

Figure 8 illustrates one form of the device according to the invention.

Figure 9 and 10 show two positions of operation of the embodiment of Fig. 8.

By means of these figures and of the following description,the present invention is illustrated more particularly with reference to its application to the rudder of a twin-engine propeller aircraft, equipped with unassisted flight controls.

The outline of such an aircraft 1 is shown in Fig. 1 in which the starboard engine 2 and the port engine 3 are illustrated, carried respectively on the corresponding wings 4 and 5 and disposed symmetrically in relation to the longitudinal axis X-X of said aircraft. At its rear portion, the aircraft 1 comprises a vertical tail-fin 6 rigidly connected to the structure of said aircraft. To the rear of this fin 6, a rudder 8 is articulated about a pin 7 which is at least approximately vertical. In addition, an aerodynamic trimmer 9 is articulated, at the trailing-edge of said rudder 8, about a pin 10 at least substantially parallel to the pin 7.

The rudder 8 is actuated in known manner under the command of the pilot or of the copilot by means of means which are likewise known and not illustrated. The trimmer 9, often called a "tab" in aerodynamics, is controlled from the movement of the rudder 8 by means of a device according to the invention, such as that illustrated in detail in Figs. 8, 9 and 10.

When the aircraft 1 is propelled by its two engines 2 and 3, the rudder 8 and the aerodynamic trimmer 9 should be able to assume any one of the relative positions illustrated by the diagrams a to e in Fig. 2, depending on the flight conditions. Moreover, when the aircraft is propelled by its starboard engine 2 because the port engine 3 has failed, the assembly consisting of the fin 6, the rudder 8 and the aerodynamic trimmer 9 should be able to assume the configuration shown by the diagram f in Fig. 3. Finally, in symmetry with this latter condition, when the starboard engine 2 has failed and only the port engine 3 is working, this assembly should be able to assume the configuration illustrated by the diagram g of Fig. 3.

The control device for the trimmer 9 automatically derives the orientation of the trimmer from that given to the rudder by the pilot or the co pilot. Consequently, if the angle between the longitudinal axis X-X of the aircraft 1 and the longitudinal axis Y-Y of the rudder 8 is called R and the angle between the longitudinal axis Z-Z of the aerodynamic trimmer 9 and the axis Y-Y of the rudder 8 is called T (see Fig. 4), the dependence of the variation in orientation of the trimmer 9 in relation to the variation in orientation of the rudder 8 can be defined by the ratio:: T R This ratio t is generally called "rate" of automatic operation The device for the automatic control of the trimmer 9 is designed in such a manner that the variations in the rate t, depending on R, have the aspect of one or other of the curves K, L, M of Figs. 5, 6 and 7 according to circumstances. In these figures, it has been assumed that, in relation to its neutral position (that is to say the position 0 in extension of the fin (6), the rudder 8 can turn through the maximum angle RM, at one side and the other, about the pin 7.

When the aircraft 1 is propelled by its two engines 2 and 3, the automatic control device is such that it enables the variations illustrated by the curve K of Fig. 5 to be imparted to the rate of automatic operation t: -in the vicinity of the neutral position of the rudder 8, for which R=O, the rate of automatic operation assumes values close to a value tow corresponding to a partial minimum, so that the return of the rudder to its neutral position is encouraged; between the value R=O and value close to RM 2 the rate of automatic operation t increases up to a maximum A or B, where it assumes the maximum value tM.Thus a sufficient rate of automatic operation is reached to enable the angular deflection of the rudder 8 to be obtained corresponding to stabilized side-slip against the cross wind on take-off and landing. This value tM of the rate of automatic operation enables stabilized side-slip to be obtained at low speeds with forces at the controls in accordance with the standard and ensures a limitation of side-slip at high speed through all-out effort; between the maximum A or B and the value RM, the rate of automatic operation t decreases down to zero at the maximum angular deflection of the rudder 8, which eliminates the reversal of the forces at the controls for large angular deflections of the rudder 8 with strong side-slip.

The curve K is symmetrical with respect to the t axis.

However, when one of the engines 2 or 3 fails and the aircraft 1 is propelled by only one of its engines, the automatic device is adapted to modify the variation in the rate t, soley to the side of the angular deflection opposite to the engine failure in question, to cause it to increase up to another maximum value t'M for the maximum angular deflection RM of the rudder 8. It is then possible to obtain the maximum angular deflection of the rudder at the side in question with forces on the controls corresponding to the standard, while avoiding the risk of a reversal of force in the event of an action by the pilot exerted in the wrong direction.

In Fig. 6, the curve L represents the variation in the rate of automatic operation t provided by the device in the case of failure of the port engine 3, while the corresponding variation in the case of failure of the starboard engine 2 is illustrated by the curve M in Fig.

7.

Illustrated in Figs. 8 to 10 is an example of the control device according to the invention, adapted to permit variations in the rate of automatic operation similar to those of Figs. 5 to 7.

The anchoring point 11 of the control of the trimmer 9, defining the proportion of automatic operation, appears as the end of a lever 12. The lever 12 is articulated at 13 on the fixed structure of the fin 6 and bears against a cam 14 which pivots about a pin 16 likewise rigidly connected to the fixed structure of the fin. A bearing or contact point 15 of the lever 12 on the cam 14 is obtained naturally on account of the aerodynamic loads on the trimmer 9 and is reinforced by a spring 17.

The cam 14 is rotated by the angular deflection of the rudder 8 by means of a link 18, the maximum angle of rotation x of the cam being, for example, of the order of +50 for a maximum angular deflection RM of the rudder of t 300.

A rod 19 is articulated at one end to a pivot 11 on the lever 12 and, at the other end, to a lever 20 mounted for pivoting about a pin 21 rigidly connected to the rudder 8. A link 22 ensures the connection between the lever 20 and the aerodynamic trimmer 9.

The profile of the cam 14 in contact with the bearing point 15 of the lever 11 is such that the law of variation of the rate of auto matic operation depending on the angular deflection of the rudder has the aspect illustrated in Fig. 5.

Two movable ramps 23 are articulated on the cam 14 and are normally retracted inside said cam. One or the other of these ramps can be brought into the projecting position by an electrical actuator, mounted on the cam 14 but not illustrated. When the bearing point 15 of the lever 12 includes contact with one or other of the ramps 23 in the projecting position, the law of variation in the rate of automatic operation depending on the angular deflection of the rudder 9 then has the form illustrated by either Fig. 6 or Fig. 7.

The relative positions of the various elements of the device in normal flight are illustrated in Figs. 8 and 9 for angular deflections of the rudder 8 equal to 0 and 15" starboard (positions a and b in Fig. 2). In Fig. 9, a ramp 23 is shown in the projecting position so that this figure likewise corresponding to the beginning of the use of said ramp in the event of failure of the starboard engine 2. In Fig.

10, the relative positions of the various elements of the device in normal flight are illustrated in full lines for an angular defection of the rudder 8 equal to 30'' to starboard (position c in Fig. 2), and there are also illustrated in broken lines the positions of the corresponding elements in the case of flight with the starboard engine 2 having failed, for an identical angular deflection of the rudder (position f of Fig. 3).

In an example in which RM was equal to 30", the rate of automatic operation had the following values: t, at 02 = 0.36 t, at+15" = 0.48 t'," at + 30 = 0.70 It goes without saying that the law of angular deflection between the trimmer 9 and the rudder 8 depends on the aerodynamic characteristics of each type of aircraft 1 and that this law results from the profile of the cam 14, which may be able to be modified.

Claims

1. A device for the automatic control of an aerodynamic trimmer articulated on the rear of an aerodynamic control surface of an aircraft, which surface is itself articulated on the structure of said aircraft, comprising a rod articulated on said aerodynamic trimmer and connected to the structure of the aircraft in such a manner that a controlled angular deflection of said aerodynamic control surface automatically results in angular deflection of said aerodynamic trimmer in relation to said aerodynamic control surface, remote from its articulation on the aerodynamic trimmer said rod being articulated on a lever that is itself articulated on said structure of the aircraft, means being provideed to displace the point of articulation of the rod and of the lever in a direction at least approximately transverse to said aerodynamic surface, in conjunction with the controlled angular deflection of said aerodynamic surface.

2. A device as claimed in claim 1, wherein the point of articulation of the rod and of the lever is at least approximately in the transverse plane passing through the axis of rotation of the aerodynamic control surface on the structure of the aircraft, and in an eccentric position in relation to said axis.

3. A device as claimed in claim 1 or claim 2, wherein the means of displacement of said point of articulation comprises a cam which is articulated on the structure of the aircraft, which is connected to said aerodynamic control surface for rotation therewith, and against which said lever bears.

4. A device as claimed in claim 3, wherein the lever is applied against said cam by the aerodynamic forces acting on the control surface.

5. A device as claimed in claim 4, wherein resilient means urge the lever against said cam.

6. A device as claimed in any one of claims 3 to 5, wherein the profile of said cam can be modified by means of movable ramps mounted on said cam.

7. A device for the automatic control of an aerodynamic trimmer constructed and arranged for use and operation substantially as described herein with reference to the accompanying drawings.

8. An aircraft having at least one aerodynamic trimmer with a control device according to any one of the preceding claims.