| Method and device for determining at least one cue of vertical position of an aircraft -> Monitor Keywords |
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Method and device for determining at least one cue of vertical position of an aircraftMethod and device for determining at least one cue of vertical position of an aircraft description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060109167, Method and device for determining at least one cue of vertical position of an aircraft. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention relates to a method and a device for determining at least one cue of vertical position of an aircraft during landing thereof. [0002] It is known that numerous airports are equipped with a ground-based radionavigation system. emitting signals allowing instrument precision landing of the ILS ("Instrument Landing System") type of an aircraft, in particular of a civil transport plane, equipped with appropriate receivers. [0003] Such a radionavigation system comprises ground stations that are situated at the strip verge and at least one specialized radioreceiver mounted aboard the aircraft, which provides horizontal and vertical guidance before and during landing by presenting the pilot with the lateral deviation with respect to an approach axis and the vertical deviation with respect to a descent plane. Said radionavigation system generally comprises, as ground stations: [0004] a directional UHF radiotransmitter, placed downstream of the strip threshold and on one side or the other of the axis of the strip, and intended to ensure vertical guidance along an approach axis according to an ideal plane of descent during an "ILS" approach, by virtue of the emission of an appropriate vertical guidance beam ("Glide" beam). More precisely, this radiotransmitter emits two signals with different modulation which are aligned one above the other and which overlap on the approach axis where the two signals are received with equal strength; and [0005] a directional VHF radiotransmitter, generally placed on the strip axis at the opposite end from the approach threshold, and intended to ensure azimuthal guidance along the approach axis according to an ideal lateral alignment profile during an "ILS" approach, by virtue of the emission of an appropriate lateral alignment beam ("Loc" beam). More precisely, this radiotransmitter emits two signals with different modulation which overlap on the approach axis where the two signals are received with equal strength. [0006] Such a radionavigation system affords considerable and effective assistance with landing (through lateral guidance and vertical guidance), in particular through poor visibility (fog, etc.) or in the absence of visibility. [0007] However, it may happen that such a radionavigation system is incomplete or at least partially faulty so that the pilot then no longer has access to all the information allowing completely assisted landing. [0008] The present invention applies to the case where no "glide" beam (vertical guidance) is available, only a "loc" beam (lateral guidance) being detectable from the aircraft. [0009] Such a case may occur in particular in the following situations: [0010] the radionavigation system comprises only means for emitting a "loc" beam; [0011] the means of said radionavigation system which are intended for emitting a "glide" beam are faulty; [0012] the radionavigation system emits a "glide" beam forward of the strip and "loc" beams forward, as well as rearward of the strip, and the landing is carried out from the rear. [0013] When such a case occurs, the pilot must manage the vertical guidance without assistance. Such management requires a considerable workload and close attention on the part of the pilot, and this may sometimes increase the risk of errors and hence entail lesser flight safety than during an "ILS" type precision approach, for which, as indicated above, the pilot benefits in particular from assistance in respect of vertical guidance. [0014] An object of the present invention is to remedy these drawbacks. It relates to a method of determining at least one cue of vertical position of an aircraft during landing thereof on a landing strip, in the presence only of a lateral alignment beam (that is to say of a "loc" beam) which is emitted from the ground and which gives an indication regarding the lateral alignment with respect to the approach axis, and hence in the absence of a detectable vertical guidance beam ("glide" beam). [0015] For this purpose, according to the invention, said method is noteworthy in that: [0016] a) said lateral alignment beam is detected on the aircraft; [0017] b) on the basis of cues relating to said lateral alignment beam thus detected and of predetermined cues, an axis of approach of the aircraft is determined; [0018] c) the actual position of the aircraft is determined; [0019] d) a preset position of the aircraft is determined, which corresponds to the position that the aircraft would have if it were on said approach axis; and [0020] e) on the basis of said actual position and of said preset position of the aircraft, the vertical deviation of the aircraft, which represents said vertical position cue, is computed. [0021] Thus, by virtue of the invention, a cue of vertical position of the aircraft is obtained solely on the basis of a lateral alignment beam ("loc" beam), that is to say without using a vertical guidance beam ("glide" beam). [0022] Advantageously, in step b), to determine said approach axis: [0023] .alpha.) a set of first axes all passing through one and the same predetermined point situated on the ground at least in proximity to said landing strip and all exhibiting one and the same predetermined slope is formed; and [0024] .beta.) a first axis of said set of first axes, whose projection onto a horizontal plane is parallel to the projection onto this horizontal plane of said lateral alignment beam detected, is chosen as approach axis. [0025] Furthermore, advantageously, in step c), the actual position of the aircraft is determined on the basis of values of longitude, of latitude and of altitude of the aircraft. [0026] In a preferred embodiment, the value of altitude of the aircraft is obtained with the aid of at least one measurement carried out by at least one barometric probe. [0027] In this case, in a first variant embodiment, the altitude value which is measured is corrected, as a function of the temperature on the ground. [0028] Preferably, the altitude value Am measured is corrected with the aid of the following expression, to obtain a corrected altitude value Ac: Ac=(Am-Ap)(T1/T2)+Ap in which: [0029] Ap represents the altitude of the landing strip; [0030] T1 is the temperature on the ground; and [0031] T2 is a predetermined temperature value. [0032] Advantageously, the altitude value is corrected only if the temperature on the ground is less than a predetermined temperature value. [0033] In a second variant embodiment (which may be combined with said first variant embodiment described hereinabove, to provide the altitude value Am used in the altitude correction formula corresponding to said first variant), the altitude value measured is corrected if necessary in such a way as to obtain a corrected altitude value QNH which is referenced with respect to the level of the sea. [0034] In this second variant, firstly, when the measured altitude value QFE is referenced with respect to the landing strip, it is corrected, with the aid of the following expression, to obtain the corrected altitude value QNH: QNH=QFE+Ap, in which Ap represents the altitude of the landing strip. [0035] Furthermore, secondly, when the measured altitude value is a standard altitude STD, it is corrected, with the aid of the following expression, to obtain the corrected altitude value QNH: QNH=STD+.DELTA. with .DELTA.=QNHp-.beta., QNHp being a value dependent on the atmospheric pressure at the level of the landing strip and .beta. being a predetermined value. [0036] The present invention also relates to a method of guiding an aircraft during landing thereof on a landing strip, in the presence of a lateral alignment beam which is emitted from the ground and which gives an indication regarding the lateral alignment with respect to the landing strip. [0037] According to the invention, this method is noteworthy in that the following series of successive operations is carried out repetitively up to landing: [0038] A/the abovementioned method is implemented to determine the vertical deviation of the aircraft; [0039] B/the lateral deviation of the aircraft with respect to said lateral alignment beam detected is determined; and [0040] C/the aircraft is guided in such a way as to cancel out said vertical and lateral deviations. [0041] Additionally, the present invention also relates to a device for determining at least one cue of vertical position of an aircraft during landing thereof on a landing strip, in the presence of a lateral alignment beam which is emitted from the ground and which gives an indication regarding the lateral alignment with respect to the landing strip. This device is noteworthy, according to the invention, in that it comprises: [0042] a means of detection for detecting said lateral alignment beam on the aircraft; [0043] a database comprising cues relating to landing on said landing strip; [0044] a first means for determining an axis of approach of the aircraft, on the basis of cues relating to said lateral alignment beam that are received from said means of detection, and cues received from said database; [0045] a second means for determining the actual position of the aircraft; [0046] a third means for determining a preset position of the aircraft, which corresponds to the position that the aircraft would have if it were on said approach axis; and [0047] a fourth means for computing, on the basis of said actual position and of said preset position of the aircraft, the vertical deviation of the aircraft, representing said vertical position cue. [0048] Preferably, said first and second means form part of one and the same computation unit. Preferably also, said third and fourth means form part of one and the same computation unit. Continue reading about Method and device for determining at least one cue of vertical position of an aircraft... Full patent description for Method and device for determining at least one cue of vertical position of an aircraft Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method and device for determining at least one cue of vertical position of an aircraft patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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