The present invention relates to a method for optimizing the landing of an aircraft on a runway, as well as a corresponding optimization device.
As known, according to standard procedure rules, an aircraft (for instance a civil transport airplane) switches from a descent start altitude to a final approach start altitude:
either while carrying out a descent at a constant speed, followed by a defined approach level, for instance, by an altitude of 3,000 feet (that is about 914 meters), for decelerating and then stabilizing at a predetermined intermediary speed, the aircraft maintaining this level, with this intermediary speed, until it intercepts a predefined final approach path Ai; or
Intercepting the approach level, or the last segment of the approach in a continuous descent, and the approach path defines the initiation of the final approach phase.
The standard slope associated with this approach path and defined in relation to the ground (the reason why it will be referred to as “ground slope” later on) is usually set at −3°. During the approach phase, the aircraft decelerates again,keeping track of the approach path, while spreading the slats, the flaps and the landing gears, so as to exhibit a landing configuration. At approximately 1000 feet (that is about 305 meters), the aircraft keeps a stabilized approach at a predefined approach speed (being, more specifically, a function of the configuration of the aircraft and of the meteorological conditions) up to 50 feet (that is about 15 meters), and then initiates its flare so as to join the runway and complete the landing.
It is known as well that, in order to avoid obstacles (for instance formed by the relief, buildings, etc.), an increased ground slope approach phase (that is for instance, switching from a −3° standard ground slope to a −4° ground slope) could be carried out. It should be noticed that, whatever the final ground slope to track, the latter is published in the operational approach procedures as defined by the air authorities.
It is also known that, in addition to air safety considerations, an increased ground slope approach phase enables to reduce the environmental impacts in the vicinity of airports (including noise and polluting emissions), as, thru the geometric structure, the aircraft flies higher for a same distance to the threshold of the runway and that the motor speed necessary to maintain this slope is lower in general. This explains why the different actors of the aeronautic field (aircraft manufacturers, airports, air companies) are eager to develop increased ground slope approaches.
Furthermore, it is known that transport civil dedicated aircrafts generally carry out their final approach on a ground slope set at −3°, while being certified for flying up to −4.49° ground slopes. Beyond this slope value, the approach phase is considered, by the international rules, as an approach on a steep slope and the aircraft should suit additional certification requirements.
Although such increased ground slopes (that is higher than −3° but lower than −4.5°) are regularly followed on numerous international airports, in order to avoid obstacles, it is not usual for the aircraft to land abruptly (this is referred to, in such a case, as a “hard” landing), comprising the good behaviour of the aircraft, especially when such hard landings are daily occurring.
In other words, in order to stand up to regular increased ground slope approaches (equal for instance to −4°), it is indispensable to review the design criteria of the aircraft in terms of performance, maneuverability, or even of structure, so as to ensure a secured landing, whatever the characteristics of the aircraft, the meteorological conditions and the geographical situations in the vicinity of airports.
Indeed, increasing the ground slope during a final approach results, on the one hand, in an increase of the vertical speed of the aircraft in relation to the ground (also referred to as “ground vertical speed” subsequently) and, on the other hand, in a decrease of the deceleration abilities of the aircraft (at the origin of hard landings). It can, for instance, be shown that, in the case of a conventional speed Vgs, a −1° increase of a ground slope initially at −3° (that is an increased ground slope equal to) −4° could result in the vertical speed Vz increasing By more than 30%.
An increase of the ground slope (and thus of the vertical ground speed) involves a review of maneuverability and deceleration abilities, even redimensioning landing gears, resulting in an additional embedded load, important modifications of the systems of the aircraft, as well as the need of an adapted training of pilots.
The present invention aims at solving these drawbacks.
To this end, according to this invention, the method for optimizing the landing of an aircraft on a runway, said landing comprising an approach phase, defined by an approach path to be tracked with which a predefined ground slope is associated, and a flaring phase, is remarkable in that:
Thus, thanks to this invention, the ground slope of the approach path is optimized, during the approach phase, while determining an optimized ground slope (with respect to the ground slope issued from standard procedure rules) from a target vertical speed predefined, based on characteristics being specific to the aircraft and one or more outside parameters, such as those associated with meteorological conditions, environmental conditions and characteristics specific to the aircraft.
Indeed, it has been shown that the flare carried out upon a landing of an aircraft depends nearly exclusively on the ground vertical speed of the aircraft, so that is forms an efficient parameter for characterizing the flare and provides an indication on the ability of the aircraft to ensure a secured landing and to avoid an inappropriately throttling up. The present invention is advantageously based on the fact that the above mentioned outside parameters disturb the deceleration abilities of the aircraft, at a set ground slope, and increase the risk that the aircraft should abruptly land on the runway, so that taking the latter into consideration in the calculation of the optimized ground slope enables to reduce the risk of hard landings.
In other words, setting the ground vertical speed of the aircraft upon the initiation of the flare (at about 50 feet) to a preliminarily defined nominal target value, the present invention will secure the final approach phase, providing a more constant, repeated and easier flare, while increasing the slope, making advantageously use of the conditions of the approach being considered for improving the environmental aspects, without imposing new designing constraints.
The higher the ground slope of the approach, the lower the motor speed of the aircraft along the approach path, reducing the atmospheric and sound pollution, as well as the fuel consumption of the aircraft.
In addition, the optimizing method of the present invention also has the advantage of being able to be implemented:
Preferably, the outside parameter(s) belong to the group of parameters comprising:
In addition, the horizontal speed of the wind, taken into consideration during the determination of the optimized ground slope, belongs to a determined range of values able to be obtained from several technological solutions.
Furthermore, for determining the optimized ground slope preferably the following steps are carried out:
In a particular embodiment, the determination of the optimized ground slope is obtained thru geometric construction of a speed triangle.
Moreover, the target vertical speed could be defined preliminarily for each type of aircraft.
So as not to decrease the safety margins imposed by the air safety authorities, the optimized ground slope ranges between a predefined lower extreme value and a predefined higher extreme value, preferably equal respectively to −3° and to −4.49°.
Furthermore, the horizontal speed of the wind could be obtained according to at least one of the following ways:
The present invention further relates to a device for optimizing the landing of an aircraft on a runway, said landing comprising an approach phase, defined by an approach path to be tracked with which a predefined ground slope is associated, and a flaring phase. According to this invention, such a device comprises:
Moreover, as the optimized ground slope is determined from said target vertical speed, the calibrated airspeed CAS, the horizontal speed of the wind, the outside temperature at a standard height, as well as the inclination and the altitude of the runway, said determination means preferably comprise:
Furthermore, the present invention further relates to an aircraft comprising a device such as specified hereinabove.
The FIGS. of the appended drawings will better explain how this invention can be implemented. In these FIGS., like reference numerals relate to like components.
In the situation schematically shown on
As shown on
Preferably, the optimized ground slope γo ranges between a lower extreme value (for instance equal to −3°) and a higher extreme value, (for instance equal to −4.49°), so as not to decrease the safety margins imposed by the air authorities.
According to the present invention, in order to optimize the landing of the aircraft AC on the runway 2, first:
Subsequently, “outside parameters,” which refer to the parameters associated with the meteorological conditions, the environmental conditions and the characteristics specific to the aircraft AC, are determined.
In particular, outside parameters able to be involved in determining the optimized ground slope according to this invention include:
the calibrated airspeed CAS of the aircraft AC with respect to the air; This speed CAS is a function of the bulk M of the aircraft and the flight configuration of the aircraft AC associated with the approach phase. Otherwise stated, using the speed CAS, the bulk M and the flight configuration of the aircraft AC are indirectly taken into consideration. It should further be noticed that the higher the bulk of the aircraft AC upon landing, the higher too the over-all approach speed, resulting in the ground slope decreasing, associated with the path A at the vertical iso speed Vz;
the outside temperature To at a standard height ho (for instance equal to 50 feet). The temperature T of the ambient air act on the tracked ground slope associated with the path A to the vertical iso speed. If the temperature T is lower than the standard temperature To defined at destination, the tracked ground slope will be finally higher than the initial ground slope γi and conversely for higher temperatures;
thru retrieval of data measured by one or more other aircrafts located in the surrounding of the runway 2 and transmitted directly to the Aircraft AC.
Several methods for obtaining the horizontal speed of the wind Vw could be used simultaneously for minimizing error measurements. Moreover, a determined range of speed values Vw could be defined, to be taken into consideration upon determining the optimized ground slope γo. In order to maintain some safety margin, only part of the wind could be taken into consideration. For instance, up to 15 kts of front wind, 80% of the wind could be considered. For stronger winds (the speed Vw of which is higher than 15 kts), a lower consideration of the wind could be implemented. Theoretically, the method of this invention enables to achieve a final approach at iso thrust, iso altitude of the aircraft AC and iso vertical speed Vz, whatever the horizontal speed of the wind Vw.
According to this invention, for determining the optimized ground slope γo, the following steps are carried out:
where R=287.053 J/kg/m3.
To this end, the calibrated airspeed CAS is retrieved, corresponding to the approach speed being considered. This value is for instance available from the FMS (for Flight Management System). Afterwards, the true speed TAS is determined thru the relationship
where ρo=1.225 kg/m3 and K is a coefficient of compressibility correction; and
Thus, after determining the optimized ground slope γo in the above mentioned way, upon the interception by the aircraft AC of the approach path A at point Pa, the aircraft AC is guided so that it tracks the optimized ground slope γo associated with the approach path A, and it reaches the target vertical speed Vzo upon the initiation of the flaring phase 4 (point Po).
For determining the optimized ground slope γo and guiding the aircraft AC as mentioned hereinabove, the device 5 illustrated on
an optimized ground slope determination device 6 for determining the optimized ground slope γo, associated with the approach path A to be tracked, receiving the outside temperature To at a standard height ho, the inclination γP and the altitude Zp of the runway 2, the calibrated airspeed CAS, the target vertical speed Vzo and the horizontal speed of the wind Vw; and
an aircraft guidance system 7 for guiding the aircraft upon the interception (point Pa) by the aircraft with the approach path A, for imposing to it to track the associated optimized slope γo and have it reach the target vertical speed Vzo at point Po.
The optimized grounds slope determination device 6 may comprise:
an air density calculator 8 for calculating the density of the air ρc at the standard height ho as defined hereinabove. It receives the outside temperature To and the altitude of the runway Zp, via links L1 and L2. The air density calculator is 8 able to deliver, in outlet, the density of the air ρc at the height ho;
a true speed calculator 9 for calculating the true speed TAS of the aircraft AC as set forth previously. It receives the density of the air ρc as determined By the air density calculator 8 and the calibrated airspeed CAS, via links L3 and L4. The true speed calculator 9 is able to deliver, in outlet, the true speed TAS; and
an optimized ground slope calculator 10 for calculating the optimized ground slope γo as mentioned hereinabove. It receives the true speed TAS determined by the true speed calculator 9, the target vertical speed Vzo, the horizontal speed of the wind Vw, as well as the inclination of the runway γP via links L5, L6, L7 and L9. The optimized ground slope calculator 10 is able to deliver, in outlet, the optimized ground slope γo so that it can be processed by the aircraft guidance system 7.
The optimized ground slope determination device 6 for determining the optimized slope γo could be integral with the flight management system FMS or with another embedded system in connection with the flight management system. Alternatively, it could be outside the aircraft and have the form of a laptop or be even integrated into a station on the ground able to communicate the optimized slope γo to the aircraft AC. The optimized slope γo could be transmitted from the optimized ground slope determination device 6 to the FMS, or even be entered manually in the FMS by pilots.
Moreover, the aircraft guidance system 7 comprises:
A piloting instructions calculation device 11 being intended for determining, usually, piloting instructions from information received from the optimized ground slope determination device 6 via the link L8;
at least one device for aiding piloting, for example, an automatic piloting device 12 and/or a flight director, determining, from the piloting instructions received from said piloting instructions calculation device 11, piloting instructions of the aircraft AC; and
control surface actuators 13 for actuating controlled organs, such as for instance (direction, depth) control surfaces of the aircraft, to which the thus determined piloting instructions are applied.
Furthermore, it could be contemplated that the determination of the optimized ground slope γo and guiding the aircraft along the path A with a slope γo are optional, providing activation and deactivation functions of such operations as, for instance, an activation device integrated into the cockpit of the aircraft AC.
In addition, it could also be provided that an indication should be displayed inside the cockpit (for instance) as a visual signal for notifying the pilots that the method for optimizing the landing according to this invention is activated. Thereby, pilots will not be surprised by a later interception of the increased slope approach path A with respect to that relating to conventional approaches (ground slope equal to −3°).
Number | Date | Country | Kind |
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11 51865 | Mar 2011 | FR | national |
Number | Name | Date | Kind |
---|---|---|---|
4638437 | Cleary et al. | Jan 1987 | A |
4925303 | Pusic | May 1990 | A |
5111403 | Orgun et al. | May 1992 | A |
5337982 | Sherry | Aug 1994 | A |
20090050746 | Dal Santo et al. | Feb 2009 | A1 |
Entry |
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French Patent Office, French Search Report FR 1151865 (2 pgs), Feb. 6, 2012. |
Number | Date | Country | |
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20120232725 A1 | Sep 2012 | US |