Method And Device For Automatically Monitoring Lateral Guidance Orders Of An Aircraft

Abstract

Method and device for automatically monitoring lateral guidance orders of an aircraft.

Description

The present invention relates to a method and a device for automatically monitoring lateral guidance orders of an aircraft, in particular of a transport airplane.

It applies to the monitoring of lateral guidance orders being provided for a flight control system of the aircraft and being generated by a calculation stage for lateral guidance orders of an aircraft guidance system. Such a calculation stage comprises, in general, more specifically:

• • a large feedback loop, determining, from guidance parameters, a turning initiation order corresponding to a roll control order; and
  • a small feedback loop, determining, from said roll control order, lateral guidance orders of the aircraft, provided for said flight control system.

Although not exclusively, the present invention more particularly applies to operations with required navigation performance with authorization required, of the RNP AR (<<Required Navigation Performance with Authorization Required>>) type. These RNP AR operations are based on a surface navigation of the RNAV (<<aRea NAVigation>>) type and on required navigation performance operations of the RNP (<<Required Navigation Performance>>) type. They have the particular feature of requiring a special authorization for being able to be implemented on an aircraft.

The RNAV type surface navigation allows an aircraft to fly from a waypoint to another waypoint, and no longer from ground stations (of radio-navigation means of the NAVAID type) to other ground stations.

As known, the RNP concept corresponds to a surface navigation, for which (on board the aircraft) monitoring and warning means are added, allowing to ensure that the aircraft remains in a corridor, referred to as RNP, around a reference trajectory and authorizing taking into consideration curved trajectories. Outside this corridor, potentially relief or other aircrafts could be present. The performance required for a RNP operation type is defined by a RNP value representing half the width (in nautical miles: NM) of the corridor around the reference trajectory, in which the aircraft should remain 95% of the time during the operation. A second corridor (around the reference trajectory) of half a width twice the RNP value is also defined. The probability that the aircraft goes out of this second corridor should be lower than 10-7 per hour of flight.

The concept of RNP AR operations is still even more stringent. The RNP AR procedures are indeed characterized by:

• • RNP values:
    • being lower than or equal to 0.3 NM in approach, and that could go down to 0.1 NM; and
    • being strictly lower than 1 NM at the start and during a throttling up, and that could also go down to 0.1 NM;
  • a final approach segment that could be curved; and
  • obstacles (mountains, traffic, . . . ) that could be located at twice the RNP value with respect to the reference trajectory, while for usual RNP operations, an additional margin with respect to obstacles is provided.

The air authorities have defined a target level of safety TLS of 10-7 per operation, whatever the type. In the case of RNP AR operations, as the RNP values can go down to 0.1 NM and the obstacles could be located at twice the RNP value of the reference trajectory, this objective results in a probability that the aircraft goes out of the half-width corridor D=2.RNP that should not exceed 10-7 per procedure.

The equipment embedded on board aircrafts (flight management system, inertial unit, means for updating GPS data and means for guiding the autopilot), as well as the usual architecture, do not allow to reach the target level of safety, if mitigation operational means are not provided, including for detecting and managing possible breakdowns. This is why a special authorization is required for this type of operation, so as to ensure that the operational procedures and the pilots' training allow the target level of safety to be reached. Moreover, as the crew should take in charge some breakdowns, the aircrafts are to-day not able to guarantee a RNP value of 0.1 NM in a breakdown situation, as the crew are not able to meet the performance requirements in manual piloting.

On current aircrafts, the monitoring of RNP AR operations is implemented by means of two usual functions, that is:

• • a first function monitoring the accuracy and the integrity of the position calculation:
    • the accuracy of the position is compared to once the RNP value;
    • the integrity is compared to twice the RNP value; and
    • if one of the two parameters, accuracy or integrity, exceeds the allotted threshold, a warning is emitted and the crew should take appropriate actions; and
  • a second function allowing the crew to monitor the guidance of the aircraft:
    • the lateral and vertical deviations of the aircraft with respect to the reference trajectory are displayed and shown to the crew;
    • the crew monitor the deviations compared to the budgets allotted for each deviation. If the crew detects an excessive deviation, it should keep the aircraft under control again and take the adequate corrective actions.

As set forth previously, the current aircrafts are not able to guarantee a RNP value of 0.1 NM in a breakdown situation and the crew should be trained specially for flying the RNP AR procedures. The crew should, indeed, be able to detect and process adequately breakdowns being able to compromise the ongoing operation.

The objective for future aircrafts is to be able to fly RNP AR procedures with RNP values up to 0.1 NM, and this without restriction (in a normal situation and in the case of a breakdown) in start, approach and throttling up phases. To this end, the crew should no longer be considered as the main means for detecting and processing breakdowns.

As set forth above, an aircraft is generally provided with a guidance system comprising at least one calculation stage for guidance orders, being intended to a flight control system of the aircraft. Now, for the aircraft to have the ability to fly particular procedures and including RNP AR procedures, it is necessary to be able to remove from the guidance loop an erroneous source of calculation for guidance orders, so as to counteract its possible effects on the trajectory of the aircraft.

The present invention aims at providing such a solution allowing detecting an erroneous source of calculation of lateral guidance orders. It relates to a method for automatically monitoring the lateral guidance orders of an aircraft, in particular of a transport airplane, being provided with at least one calculation stage for guidance orders, intended for a flight control system of the aircraft.

To this end, according to the invention, said method for monitoring the lateral guidance orders of an aircraft being provided with at least one calculation stage for lateral guidance orders, said calculation stage comprising:

• • at least one large feedback loop, determining, from guidance parameters, a turning initiation order corresponding to a roll control order; and
  • at least one small feedback loop, determining, from said roll control order, said lateral guidance orders of the aircraft, intended for the flight control system,is remarkable in that:
  • on said calculation stage for lateral guidance orders an architecture is provided comprising at least N pieces of equipment, each of which is provided at least with one large feedback loop and is able to generate, in outlet of the associated large feedback loop, a roll control order, N being an integer higher than or equal to 3;
  • automatically and repeatedly, comparisons are made, comparing therebetween, two to two, the roll control orders generated by said N pieces of equipment;
  • from these comparisons, if applicable, a piece of equipment with failure is determined concerning the generation of lateral guidance orders of the aircraft; and
  • when one piece of equipment has a failure, at least one corresponding warning is emitted in the cockpit of the aircraft.

Thus, thanks to the invention, comparisons are made between the roll control orders generated by said N pieces of equipment so as to be able to detect a diverging source as soon as an error occurs, that is as soon as a piece of equipment is failing concerning the generation of lateral guidance orders. Furthermore, as detailed herein below, this detection of a failure is reliable.

The determination and the exclusion of the source of erroneous lateral guidance orders allow, more specifically, the following objectives to be met, consisting in:

• • informing the crew about the piece of equipment with a failure (or defective);
  • avoiding going on to use a source, with a proven failure; and
  • preparing the maintenance operations for the replacement of the piece of equipment with a failure.

Advantageously, for each piece of equipment:

• • the deviations are calculated between the roll control order generated by this piece of equipment and each of the control orders generated by each of the other pieces of equipment;
  • each of the thus calculated deviations is compared to a monitoring threshold; and
  • it is considered that said piece of equipment has a failure if all the corresponding deviations are higher than said monitoring threshold.

In addition, in a preferred embodiment, providing for an anticipation of the detection of a failure, for at least one inlet parameter of said large feedback loops, the following operations are additionally implemented:

• • comparisons are made, comparing therebetween, two to two, the values relative to said inlet parameter, used respectively by said equipment; and
  • from these comparisons, if applicable, a piece of equipment is determined, anticipatively, being failing concerning the generation of lateral guidance orders of the aircraft.

In this preferred embodiment, advantageously, for each piece of equipment:

• • the deviations are calculated between the value of the inlet parameter being considered, used by this piece of equipment, and each one of the values of said inlet parameter, used by each of the other pieces of equipment;
  • each of the thus calculated deviations is compared to an auxiliary monitoring threshold; and
  • it is considered that said piece of equipment has a failure if all the corresponding deviations are higher than said auxiliary monitoring threshold.

Preferably, at least one of the following inlet parameters is used:

• • a deviation of position of the aircraft with respect to the trajectory, impacting on the roll control order for correcting this deviation;
  • a deviation of orientation of the aircraft with respect to the trajectory, impacting as well on the roll control order; and
  • a nominal roll representing the roll control order applicable by default for a next turn.

Said nominal roll is calculated in phase lead compared to the next turn. Its monitoring allows a building failure of the trajectory to be anticipated. This information may be employed for invalidating a defective piece of equipment before it could generate an erroneous roll control order.

In a particular embodiment, the values of several of said inlet parameters are simultaneously analyzed for monitoring a piece of equipment concerning the generation of lateral guidance orders. By way of illustration, the monitoring of the above mentioned position and orientation deviations, if they are combined, allows identifying a problem of definition for the flight plane or the trajectory built therefrom. Their impact is instantaneous on the roll control order.

Furthermore, advantageously, when a defective piece of equipment is detected, the maintenance means are notified about this failure, so as to prepare more specifically the maintenance operations for replacing or repairing this piece of equipment with a failure.

In addition, advantageously it is considered that a piece of equipment is definitely failing if all the corresponding deviations are higher than the threshold being considered (monitoring threshold or auxiliary monitoring threshold) for a predetermined period of time.

The present invention also relates to a device for automatically monitoring lateral guidance orders of an aircraft, in particular of a transport airplane, being provided with at least one calculation stage for lateral guidance orders provided for a flight control system of the aircraft.

According to the invention, said device of the type comprising at least one calculation stage for lateral guidance orders, said calculation stage comprising:

• • at least one large feedback loop, determining, from guidance parameters, a turning initiation order; and
  • at least one small feedback loop, determining, from said turning initiation order, lateral guidance orders of the aircraft, provided for the flight control system,is remarkable in that:
  • said calculation stage has an architecture comprising at least N pieces of equipment, each of which is provided at least with one large feedback loop and is able to generate, in outlet of the associated large feedback loop, a roll control order, N being an integer higher than or equal to 3;
  • said device further comprises monitoring means being formed so as to make, automatically and repeatedly, comparisons, comparing therebetween, two to two, the roll control orders generated by said N pieces of equipment, and to determine, if applicable, from these comparisons, a piece of equipment being failing concerning the generation of lateral guidance orders of the aircraft; and
  • warning means for emitting at least one corresponding warning in the cockpit of the aircraft, when a piece of equipment is regarded as having a failure.

In a preferred embodiment, said monitoring means comprise anticipation means for determining, if applicable, anticipatively, a piece of equipment being failing (concerning the generation of lateral guidance orders of the aircraft).

Preferably, said anticipation means are formed so as to make, for at least one inlet parameter of said large feedback loops, comparisons, for instance a position or orientation deviation or a nominal roll, comparing therebetween, two to two, the values relative to said inlet parameter, used respectively by said piece of equipment, and to determine, if applicable, from these comparisons, anticipatively, a piece of equipment being failing concerning the generation of lateral guidance orders of the aircraft.

The present invention also relates to:

• • a guidance system comprising a monitoring device such as mentioned herein above; and/or
  • an aircraft, in particular a transport airplane, being provided with such a guidance system and/or such a monitoring device.

The FIGS. of the appended drawing will better explain how this invention can be implemented. In these FIGS., like reference numerals relate to like components.

FIGS. 1 and 2 are block diagrams of two different embodiments of a device according to this invention.

The device 1 according to this invention and schematically shown on FIGS. 1 and 2 is intended for automatically monitoring the lateral guidance orders of an aircraft AC, in particular a transport airplane.

The device 1 being on-board the aircraft A comprises at least one calculation stage 3 for lateral guidance orders, being intended for a usual flight control system of the aircraft, as illustrated by a link 4 on the FIGS. The device 1 could, in particular, be used so as to help carrying out air operations with required navigation and guidance performance, and more specifically RNP AR operations.

A calculation stage 3 for lateral guidance orders comprises, usually:

• • at least one large feedback loop, usually determining, from guidance parameters, a turning initiation order corresponding to a roll control order. These guidance parameters are received from usual means 6 for managing the trajectory, via a link 7. These means 6 use, for their processings, the flight plane received by the usual means 8 via a link 9, as well as the data of attitude and position of the aircraft received from sensors and usual calculation means as illustrated by a link 10 in mixed lines on FIG. 1; and
  • at least one small feedback loop 12 determining, usually, from said roll control order and from data coming from actuators and sensors (as illustrated by a link 13 in mixed lines), said lateral guidance orders of the aircraft AC, provided for the flight control system.

Consequently, from information present in the flight plane and the data reflecting more specifically the position of the aircraft AC with respect to the desired trajectory, the transfer function of the large side loop 5 calculates a turning initiation order of the aircraft AC. This order is afterwards transmitted to the transfer function of the small loop 12 for slaving the aircraft AC.

Furthermore, in a particular embodiment, passivation means 14 to be further detailed below are arranged between the feedback loops 5 and 12, to which they are linked respectively via the links 15 and 16.

The monitoring device 1 is part of a guidance system 2 of the aircraft AC. It is known that, generally, a guidance system 2 comprises, in addition to said calculation stage 3 for guidance orders, at least the following successive stages (not specifically shown):

• • one calculation stage for the position of the aircraft;
  • one management stage for the flight plane of the aircraft;
  • one calculation stage for the position of the aircraft; and
  • one calculation stage for deviations.

According to the invention, and as shown on FIG. 1:

• • said calculation stage 3 for lateral guidance orders has an architecture comprising at least N pieces of equipment E1, E2, E3, each of which is provided at least with one large feedback loop 5 and is able to generate, in outlet of the associated large feedback loop 5, a roll control order, N being an integer higher than or equal to 3. The introduction of this redundancy allows to produce several comparable roll control orders; and
  • said device 1 further comprises monitoring means 18. Such monitoring means 18 comprise a unit 17 comprising integrated elements (not shown):
    • for making, automatically and repeatedly, comparisons, comparing therebetween, two to two, the roll control orders generated by said N large feedback loops 5 of said pieces of equipment E1, E2, E3, and received via the links 19 (linked to the links 15); and
    • for determining and identifying, if applicable, from these comparisons, a piece of equipment being failing concerning the generation of lateral guidance orders of the aircraft AC, that is an equipment that is no longer able to generate valid (not erroneous) lateral guidance orders; and
  • warning means 20 being linked via a link 21 to said monitoring means 18 and being formed so as to emit at least one (either visual or sound) warning in the cockpit of the aircraft AC, when a piece of equipment is regarded as having a failure by said monitoring means 18.

Thus, the device 1 according to this invention makes comparisons between the roll control orders generated by the N large feedback loops 5 of said N pieces of equipment E1, E2, E3, so as to be able to detect a diverging source as soon as an error occurs, that is as soon as a piece of equipment is failing concerning the generation of lateral guidance orders. Furthermore, this detection of failure is reliable.

The architecture according to this invention for the detection and the isolation of equipment or systems with a failure thus relies on a principle of triplex architecture (or with N pieces of equipment (N≧3)) and provides using three sources (pieces of equipment E1 to E3), or more, at least at the level of the calculation stage 3 for orders of guidance for slaving the aircraft on the trajectory, allowing to automatically detect and isolate the failures at the level of this stage 3. Furthermore, this stage 3 could be made up of identical equipment (symmetric stage) or different equipment (dissymmetric stage).

In a preferred not shown embodiment, each of the above mentioned stages of the guidance system 2 has such an architecture comprising at least N pieces of equipment.

Furthermore, when the monitoring means 18 determine that a piece of equipment is failing, they inform maintenance means 22 about this failure, via the link 21, allowing more specifically to prepare the maintenance operations for the replacement of the piece of equipment with a failure.

Furthermore, in a particular embodiment, the analysis of the orders coming from each chain of calculation is implemented by the passivation means 14. These passivation means 14 aim at comparing the orders coming from each guidance string and isolating the defective values. They transmit afterwards a valid order to the feedback loop 12. This known principle allows the impact to be omitted of any simple failure of a guidance string on the trajectory of the aircraft AC. With this type of architecture, it is possible to passivate an erroneous guidance order so that the latter does not affect the trajectory of the aircraft AC. This solution of passivation does not however identify the source of the error, this being on the other hand implemented by the monitoring means 18 according to this invention.

The determination and the exclusion of a source of erroneous lateral guidance orders enable more specifically, to meet the following objectives consisting in:

• • informing the crew about the failure of the piece of equipment, by means of the warning means 20;
  • avoiding going on to use a source, with a proven failure, by means, more specifically, of the passivation means 14; and
  • preparing the maintenance operations for the replacement of the piece of equipment with a failure, as a result of the information supplied to the means 22.

In the basic embodiment of FIG. 1, by monitoring the roll control orders generated by the N large feedback loops 5, having a direct impact on the trajectory of the aircraft, the monitoring means 18 are able to identify a failure once it is directly observable.

For anticipating the occurrence of the anomaly, an additional mechanism is provided in the preferred embodiment of FIG. 2. Its principle involves monitoring at least one inlet parameter of the transfer function of the large feedback loops 5.

In this preferred embodiment, said monitoring means 18 comprise anticipation means 23 for determining, if applicable, anticipatively, a piece of equipment being failing concerning the generation of lateral guidance orders of the aircraft AC.

In this preferred embodiment, said monitoring means 18 are linked via the links 24 to the inlets of the large feedback loops 5 of the equipment E1 to E3 for recovering the values of one or more inlet parameters, as shown on FIG. 2. For clarity reasons, the links 10 and 13 and the means 8 are not shown on this FIG. 2, although they are also present on the system 2.

Said anticipation means 23 comprise the integrated elements (not shown) for implementing, for each piece of equipment E1 to E3, the following operations consisting in:

• • calculating the deviations between the roll control order generated by this piece of equipment and each of the control orders generated by each of the other pieces of equipment;
  • comparing each of the thus calculated deviations to an auxiliary monitoring threshold; and
  • considering that said piece of equipment has a failure if all the corresponding deviations are higher than said auxiliary monitoring threshold.

Preferably, the anticipation means 23 use at least one of the following inlet parameters:

• • a deviation of position of the aircraft AC with respect to the trajectory, impacting on the roll control order for correcting this deviation;
  • a deviation of orientation of the aircraft AC with respect to the trajectory, impacting as well on the roll control order; and
  • a nominal roll representing the roll control order applicable by default for a next turn.

Said nominal roll is calculated in phase lead compared to the next turn. Its monitoring allows a building failure of the trajectory to be anticipated. This information may be employed for invalidating a defective equipment before it could generate an erroneous roll control order.

In a particular embodiment, said anticipation means 23 simultaneously analyze the values of several of said inlet parameters, for monitoring a piece of equipment concerning the generation of lateral guidance orders. By way of illustration, the monitoring of the above mentioned position and orientation deviations, if they are combined, allows for identifying a problem of definition of the flight plane or the trajectory built therefrom. Their impact is instantaneous on the roll control order.

In addition, the monitoring means 18 consider:

• • that a source is (at least temporarily) regarded as having a failure as soon as it goes out of the predefined monitoring threshold; and
  • that a source is finally regarded as having a failure as soon as exceeding the threshold (monitoring threshold or auxiliary monitoring threshold) is confirmed for an also predefined period of time.

In a preferred embodiment, shown on FIGS. 1 and 2:

• • said pieces of equipment E1, E2, E3 are integrated each in a flight management system S1, S2, S3 of the FMS (<<Flight Management System>>) type; and
  • said monitoring means 18 are integrated in at least one flight control and guidance system S4 of the FOGS (<<Flight Control and Guidance System>>) type.

In a RNP-AR context, the detection of an anomaly on one of these parameters results in a defective (flight management) system 51, S2, S3 being notified to the maintenance systems 22 and to warnings (means 20) being triggered in the cockpit for notifying the crew. The architecture and the above described different monitoring functions thus allow the aircraft AC to meet the safety requirements inherent to RNP AR operations, being able to automatically detect, identify and isolate a system with a failure.

The monitoring mechanism according to this invention thus operates:

• • basically (FIG. 1), from orders of turning initiation, in outlet of the transfer function of the large guidance loop; and
  • in addition (FIG. 2), from inlet parameters of the transfer function of the large guidance loop.

It should be alternatively noticed that:

• • the triplex architecture described in the above mentioned particular embodiments could be replaced by a larger number of redundancies for each of the contributors of the function; and
  • each contributor could also have an internal architecture, having its redundancies not based on the same systems.

Claims

1. A method for monitoring the lateral guidance orders of an aircraft (AC) being provided with at least one calculation stage (3) for lateral guidance orders, provided for a flight control system, said calculation stage (3) comprising: at least one large feedback loop (5), determining, from guidance parameters, a turning initiation order corresponding to a roll control order; andat least one small feedback loop (12), determining, from said roll control order, said lateral guidance orders of the aircraft,

2. The method according to claim 1, wherein, for each piece of equipment: the deviations are calculated between the roll control order generated by this piece of equipment and each of the control orders generated by each of the other pieces of equipment;each of the thus calculated deviations is compared to a monitoring threshold; andit is considered that said piece of equipment has a failure if all the corresponding deviations are higher than said monitoring threshold.

3. The method according to claim 1, wherein, for each piece of equipment: the deviations are calculated between the value of the inlet parameter being considered, used by this piece of equipment, and each one of the values of said inlet parameter, used by each of the other pieces of equipment;each of the thus calculated deviations is compared to an auxiliary monitoring threshold; andit is considered that said piece of equipment has a failure if all the corresponding deviations are higher than said auxiliary monitoring threshold.

4. The method according to claim 1, wherein at least one of the following inlet parameters is used: a deviation of position of the aircraft (AC) with respect to the trajectory;a deviation of orientation of the aircraft (AC) with respect to the trajectory; anda nominal roll.

5. A method according to the claim 1, wherein the values of several inlet parameters are simultaneously analyzed for monitoring a piece of equipment with respect to the generation of lateral guidance orders.

6. A method according to claim 1, wherein, when it is determined that a piece of equipment is failing, the maintenance means (22) are informed about this failure.

7. A method according to claim 1, Wherein it is considered that a piece of equipment has definitely a failure if all the corresponding deviations are higher than a corresponding monitoring threshold for a predetermined period of time.

8. A device for automatically monitoring lateral guidance orders of an aircraft, said device (1) comprising at least one calculation stage (3) for lateral guidance orders, being provided for a flight control system, said calculation stage (3) comprising:at least one large feedback loop (5), determining, from guidance parameters, a turning initiation order; andat least one small feedback loop (12), determining, from said turning initiation order, the lateral guidance orders of the aircraft, said calculation stage (3) having an architecture comprising at least N pieces of equipment (E1, E2, E3), each of which is provided at least with one large feedback loop (5) and is able to generate, in outlet of the associated large feedback loop (5), a roll control order, N being an integer higher than or equal to 3;said device (1) further comprising monitoring means (18) being formed so as to make, automatically and repeatedly, comparisons, comparing therebetween, two to two, the roll control orders generated by said N pieces of equipment (E1, E2, E3), and to determine, if applicable, from these comparisons, a piece of equipment being failing concerning the generation of lateral guidance orders of the aircraft (AC), and warning means (20) for emitting at least one corresponding warning in the cockpit of the aircraft (AC), when a piece of equipment has a failure;said monitoring means (18) comprising anticipation means (23) for determining, if applicable, anticipatively, a piece of equipment being failing concerning the generation of lateral guidance orders of the aircraft (AC), being formed so as to make, for at least one inlet parameter of said large feedback loops, comparisons, comparing therebetween, two to two, the values relative to said inlet parameter, used respectively by said pieces of equipment, and to determine, if applicable, from these comparisons, anticipatively, a piece of equipment with a failure concerning the generation of lateral guidance orders of the aircraft (AC).

9. A guidance system of an aircraft, said guidance system (2) comprising at least one calculation stage (3) for lateral guidance orders, being provided for a flight control system of the aircraft (AC), wherein comprising a monitoring device (1) such as specified in claim 8.

10. The system according to claim 9, wherein said monitoring means (18) are integrated in a guidance and control calculator (S4) of said guidance system (2).

11. An aircraft, wherein comprising a monitoring device (1) such as specified in claim 8.

12. The aircraft, wherein comprising a guidance system (2) such as specified in claim 9.