The present invention relates to a method and a device for automatically monitoring the ability of an aircraft, in particular of a transport airplane, to follow a flight trajectory comprising at least one turn.
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 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 type operation 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:
The air authorities have defined a target level of safety TLS (<<Target Level of Safety>>) 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 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:
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.
The ability of an aircraft to follow a RNP AR trajectory comprising at least one turn, could be comprised under certain particular conditions, including in case of unfavourable winds. Under this type of conditions and depending on the wind force being encountered, the aircraft is sometimes no longer able to follow the defined trajectory. This type of problem could also occur when the speed of the aircraft exceeds a reference speed for the turn being started. This situation could, more specifically, occur as a result of a breakdown or of an error from the crew concerning a manually selected speed.
It is thus advantageous to be able to monitor the ability of the aircraft to meet the RNP AR performance. If the required performance level is not reached, the crew should be made aware of this, so as to be able to most appropriately react.
The present invention aims at solving the above mentioned drawbacks. It relates to a method for automatically monitoring the ability of an aircraft to follow a flight trajectory comprising at least one turn.
To this end, according to this invention, said method is remarkable in that, during a flight of the aircraft, for at least one turn of said flight trajectory, automatically:
a) the radius of said turn is determined;
b) a limit speed is determined up to which the aircraft may flight according to said turn without any risk of excursion of the flight trajectory;
c) a current speed value of the aircraft is determined;
d) said current speed value is compared to said limit speed; and
e) from this comparison, it is inferred:
Preferably, said steps c), d) and e) are repeatedly implemented, upon a flight of the aircraft.
Thereby, thanks to the invention, through comparing the current speed of the aircraft, in particular a current ground speed, to an appropriately calculated limit speed, it is possible to monitor the adaptation of the speed of the aircraft to the turn(s) to be encountered, that is the ability of the aircraft to follow its trajectory with no risk of excursion.
Monitoring according to this invention performance of follow up of a trajectory with turn(s) is particularly adapted to the RNP context, but could be extended to any guidance context implemented according to a flight plane.
Advantageously, at step e), a warning is emitted if there is a risk of excursion. Thus, if the required performance level is not met, the crew are made aware and are able to react in a most adapted way, either reducing its speed, or throttling up.
Additionally, advantageously, at step a):
Furthermore, in a preferred embodiment, the following operations are implemented:
In this case, preferably, at step e):
Thus, the warning level (warning, alarm) can be adapted to the actual situation: a simple risk of excursion without overspeed or an overspeed.
Additionally, advantageously, at step b):
Furthermore, said steps a) to e) are implemented:
Furthermore, advantageously, at step e), an automatic regulation of the speed can also be implemented in the case of a risk of excursion.
The present invention further relates to a device for automatically monitoring the ability of an aircraft, in particular of a transport airplane, to follow a flight trajectory comprising at least one turn.
According to this invention, said device is remarkable in that it comprises:
Moreover, in a preferred embodiment, said device further comprises:
The present invention further relates to:
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.
The device 1 according to this invention and schematically shown on
It is known that the navigation, in or out of a RNP context, is based on the information supplied by the flight plane. The latter is broken down in a succession of segments S1 to S6 defined in the side plane, as shown on
As set forth above, the ability of an aircraft AC to follow a flight trajectory TV1 comprising at least one turn VD could be compromised under certain particular conditions including in the case of unfavourable winds, as shown on
The device 1 according to this invention aims at monitoring the ability of the aircraft AC to follow its flight trajectory so as to be able to detect a situation such as mentioned hereinabove.
To this end, said device 1 on-board the aircraft AC, comprises according to the invention:
Thus, through comparing the current speed Vc of the aircraft AC, in particular a current ground speed, to an appropriately calculated limit speed Vlim, said device 1 according to this invention is able to monitor the adaptation of the speed of the aircraft to the turn(s) to be encountered, that is the ability of the aircraft AC to follow its trajectory TV, and more specifically, to reach RNP AR performance.
Monitoring according to this invention is particularly adapted to the RNP context, but could be extended to any guidance context implemented according to a flight plane.
Said device 1 further comprises means 16 being connected via a link 17 to said means 14 and being formed so as to emit a warning, of the visual or sound type, in the cockpit of the aircraft AC, as soon as the means 14 consider that there is a risk of excursion. Thus, if the performance level is not met, the crew are immediately made aware and are able to react in a most adapted way, either manually reducing the speed of the aircraft AC, or controlling a throttling up.
This invention thus provides warnings to the crew, so that they are able to react accordingly should a problem occur, manually adjusting the speed of the aircraft AC. It is also possible to implement an automatic regulation of the speed of the aircraft AC.
To this end, in a particular embodiment, said device 1 further comprises means 18 being connected via a link 19 to said means 14 and being formed so as to implement an automatic regulation of the speed in the case of a risk of excursion, preferably bounding it systematically to the limit speed Vlim. If, however, the automatic regulation of the speed does not allow meeting the desired performance level, this approach could be completed by relevantly selected warning levels (and emitted by the means 16).
Moreover, in a preferred embodiment, said device 1 further comprises:
In such a case, the means 16 are formed so as:
Thus, the warning level can be adapted (warning, alarm) to the actual situation: a simple risk of excursion without overspeed or an overspeed.
Furthermore, the means 10 determine usually the current speed Vc of the aircraft AC in a referential adapted for the implementation context. This could be the speed of the aircraft AC relative to the speed of the air or even the speed of the aircraft AC in the ground benchmark, for instance. In order that any turn could be triggered without risk of excursion, it is thus advisable to compare the current speed Vc to the limit speed Vlim for ensuring that the speed of the aircraft AC is adapted for the trajectory to be followed, for instance, for ensuring that the speed of the aircraft AC allows to remain on a trajectory of the RNP type, despite unfavourable winds. The theoretical maximum speed Vmax may be employed as a complement for evaluating the level of risk, to which the current speed Vc submits the aircraft AC.
Furthermore, the means 8 calculate said limit speed Vlim based on the following expression:
Vlim=√{square root over (R.g.tg(Φlim))}
wherein:
Furthermore, the means 20 calculate said theoretical maximum speed Vmax based on the following expression:
Vmax=√{square root over (R.g.tg(Φmax))}
wherein ømax corresponds to a maximum, preferably predetermined, roll, for instance 30° as shown on
Being integrated into the systems involved in the guidance loop of the guidance system 2 (being only partially shown on
Furthermore, in a second embodiment, including the means 8, 11, 14, 16, 20, and 22 of said device 1 are integrated into a Flight Control and Guidance System of the FCGS type. In this second embodiment, monitoring is distributed between the FCGS and FMS systems, the FMS system supplying in particular the information relative to the flight plane.
It should be noticed, in an alternative, that, contrarily to the previously detailed principle, for which a controlled roll margin ølim is determined on a constant basis, a speed margin could also be selected as constant CS. In this case, the device 1 can calculate the limit speed Vlim from the following relationship:
Vlim=Vmax−CS
With a constant speed margin CS and depending on the selected value, it is possible to tolerate higher rolls for high ground speeds.
The previously presented approaches are based on data or radiuses of turn extracted from the navigation database 3. It is also possible to rely on a turn nominal roll, allowing the means 6 to infer the radius of the turn. To this end, it is known that on the current flight management systems FMS, the nominal roll of the turn is calculated for each turn of the flight plane.
A particular application of the device 1 according to this invention relates to a monitoring covering all the future turns on an ongoing RNP procedure. However, it could also be contemplated that the device 1 only monitors a sub-part of all these turns, only analyzing the or one reduced number of next turns, that could be sufficient for giving the crew some time to react should a problem occur. Beyond a certain number of next turns, the current speed of the aircraft AC in the ground benchmark is no longer able to be implemented: a prediction of the ground speed of the aircraft AC could then be used for implementing this invention.
Number | Date | Country | Kind |
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1060314 | Dec 2010 | FR | national |