Vortex detection and mitigation system

Abstract

A vorticity detection means for an aircraft is disclosed, comprising an array of vorticity probes 10 arranged to detect a level of vorticity in the air flow adjacent the aircraft and an output means (

Description

20 02 25 FIELD OF THE INVENTION

[0001] The present invention relates to systems and methods for measuring and calming or reducing vorticity, in particular close to the ground around aircraft take-off and landing sites, and mid-air turbulence such as wake turbulence. BACKGROUND TO THE INVENTION

[0002] The demand for runway capacity is increasing with increased accessibility to travel and the use of aircraft for the import and export of goods in globalised markets. The capability of the aviation industry to cope with this demand is limited in one aspect by runway capacity. Runway capacity can be affected, in one aspect, by requirements for spacing of aircraft on approach to, and departure from, the runway. Spacing of aircraft for safety reasons results in a minimum delay between aircraft which can land on or take off from a particular runway. One factor affecting a need for such spacing between aircraft is wake turbulence caused by arriving or departing aircraft disturbing the local airflow, which can have an effect for several minutes.

[0003] Wake turbulence is a phenomenon that occurs during the generation of lift. Differential pressure at the wing tip causes the airflow aft of the wing to "roll up". This results in two counter-rotating vortices, one generated aft of each of the port and starboard wings of a flying aircraft. These vortices can be hazardous and remain in the local airflow for several minutes after the passage of an aircraft. If one aircraft encounters the wake of another aircraft, the turbulent airflow can lead difficulties in controlling of the aircraft.

[0004] To mitigate these hazards, aviation authorities worldwide stipulate a minimum time separation following the take-off or landing of one aeroplane, only after which another aeroplane may take-off or land. The vorticity of wake flow is a function of several features including weight, speed, wing geometry and weather. Within the UK, minimum time separation is based on the weight class of the two aircraft in question (light, small, lower or upper medium, or heavy). In some instances, the waiting time required may be less than the regulatory minimum time separation. Measuring the vorticity in local airspace can enable reduced delay by indicating when vorticity is sufficiently low - which may be in a lesser amount of time than the minimum time separation - therefore increasing the efficiency of operations by increasing the availability of runways.

[0005] U.K. Patent GB2142439 granted to the present inventor discloses an invention relating to a vorticity measuring means for aerodynamic testing. It discloses an array of two-tube yaw meter probes arranged such that the differences in pressure registered 20 02 25 between the two tubes of each probe are combined to produce an output responsive primarily to the vorticity component along the longitudinal axis of the array.

[0006] Other known means for detecting vortices include Airport Low-level Wind Information (hereinafter referred to as 'ALWIN'), Low-level Turbulence Advisory Systems (hereinafter referred to as ’LOTAS') and Sodar-based Low-level Wind Information (hereinafter referred to as 'SOLWIN'). Both ALWIN and LOTAS use Doppler radar or lidar, whilst LOTAS uses Doppler Sonic Detection and Ranging. ALWIN and LOTAS systems are expensive to implement. SOLWIN systems are limited by a narrow observation area and thus are limited to application in regional airports. With each of these techniques, their implementation requires significant investment in infrastructure. The current accessibility of these techniques is thus limited to larger airports.

[0007] There is therefore a need for an improved method of detecting vorticity characteristics affecting aircraft, in particular in take-off and landing. SUMMARY OF THE INVENTION

[0008] A first aspect of the invention provides an aircraft comprising a vorticity detection means, the vorticity detection means comprising: an array of vorticity probes arranged to detect a level of vorticity in the air flow adjacent the aircraft; an output means, arranged to output a vorticity signal to a pilot or autopilot of the aircraft, indicative of the detected level of vorticity in the airflow adjacent the aircraft; a first array of vorticity probes configured to detect a level of vorticity in a first direction of rotation and a second array of vorticity probes configured to detect a level of vorticity in a second direction of rotation; and a comparator, arranged to detect a difference in magnitude between the detected level of vorticity in the first direction and the detected level of vorticity in the second direction; wherein the output means is arranged to output the vorticity signal indicative of the difference in magnitude between the detected level of vorticity in the first direction and the detected level of vorticity in the second direction.

[0010] The invention can decrease the severity of vortices such that vorticity can represent a reduced hazard. 20 02 25

[0011] The vorticity detection means may comprise pressure sensing means.

[0012] The vorticity detection means may comprise a pair of manifolds.

[0013] Preferably, the vorticity detection means may comprise a pressure transducer.

[0014] The output means may comprise a flight instrument.

[0015] The first array and the second array may have an equal number of vorticity probes to one another.

[0016] The output means may be configured to compare the detected vorticity to a preset threshold level of vorticity. Preferably, the output means is configured to compare the detected vorticity to a pre-set threshold level of vorticity via one or more manifolds.

[0017] The output means may be configured to output a warning when vorticity exceeds the pre-set threshold level of vorticity. The output means may be configured to send a warning output to a flight controller.

[0018] The output means may be configured to deliver the output to a flight controller when vorticity exceeds the pre-set level. The flight controller may be configured to react to the output to mitigate the effect of the detected vorticity on the aircraft, such as by taking evasive action, or by applying a flight control to counter the effect of the vorticity on the aircraft. Such flight control may comprise applying a roll input opposite to the direction of the detected vorticity.

[0019] The aircraft may be a fixed-wing aircraft.

[0020] The first array of vorticity probes and the second array of vorticity probes may be arranged about the circumference of the fuselage of the aircraft.

[0021] The vorticity probes of the array may be substantially evenly distributed about the longitudinal axis of the fuselage. The angular distance about the longitudinal axis of the fuselage between the vorticity probes may be substantially equal.

[0022] The vorticity probes may be positioned to detect vorticity in the free stream of local airflow, which airflow is local to the aircraft fuselage.

[0023] The first array of vorticity probes and the second array of vorticity probes may be arranged forward of a wing section of the aircraft.

[0024] The term vorticity as used herein generally refers to the stream-wise component of vorticity.

[0025] A vorticity probe may comprise a means of measuring a property of local airflow indicative of vorticity. The vorticity probe may be comprised of, but is not limited to, 20 02 25 pressure sensors or anemometers of any suitable configuration including but not limited to tube, vane, cup or hot wire anemometers.

[0026] The comparator may comprise a pair of manifolds. Preferably, with this arrangement the two-tube vorticity probes are in fluid communication with the pair of manifolds via pitot tubes. Alternatively the comparator may comprise a computing device.

[0027] The output means may comprise a flight instrument. With this configuration, the output means may be configured to display measurements to a pilot. A flight instrument may comprise either one of, but is not limited to, a gauge or an HUD instrument for example.

[0028] The output means may comprise a computing device. With this configuration, the output means may be configured to output measurements to a pilot. Alternatively or additionally, the output means may be configured to output measurements to a flight controller of an aircraft. The computing device may be configured to communicate data to an air traffic control centre.

[0029] The output means may be configured to monitor a pre-set range of vorticity values. The pre-set range of vorticity values refers to a range of values, which may comprise a maximum value and a minimum value. Above the maximum value, the output means may determine a hazard. Below the minimum value, the output means may determine safe flight. Between the minimum value and the maximum values, the output means may determine a level of vorticity which may be mitigated with input to flight controls. The output means may be configured to a pre-set hazard level of vorticity. The pre-set hazard level of vorticity refers to a single value, above which the output means determines a hazard.

[0030] The flight controller may comprise an automated flight control system. The flight controller may comprise a partially automated flight control system. With this configuration, the flight controller may output vorticity measurements to enable the flight controller to counteract vorticity.

[0031] An aspect of the disclosure provides a vorticity detection system, arranged to detect a level of vorticity at a take-off or landing site for aircraft, the detection system comprising: an array of vorticity probes arranged on or adjacent to the take-off or landing site to detect a local vorticity level at the site of the probes, a measuring means, configured to detect a property of at least one of the vorticity probes, indicative of a vorticity detected by the probe, and 20 02 25 an output means, configured to output a vorticity value indicative of the vorticity detected by the probe.

[0032] Preferably, the measuring means for detecting a property of at least one of the vorticity probes comprises an optical measuring means.

[0033] The vorticity probes may comprise tube yaw meters.

[0034] The vorticity probes may comprise vane anemometers.

[0035] The vane anemometers may be configured to rotate about an axis substantially parallel to the longitudinal take-off or landing direction of the take-off or landing site.

[0036] The vorticity detection system may comprise an illumination means arranged to illuminate the vane anemometers in low visibility conditions.

[0037] The output means may be configured to output a signal indicative of detected vorticity levels at the take-off or landing site to an air traffic controller.

[0038] The output means may be configured to output a signal indicative of detected vorticity levels at the take-off or landing site to an air traffic controller.

[0039] In addition to and independent of the means of vortex detection, devices may be deployed in order to remove partly or completely the vortices shed by aircraft which may cause problems for users of runways. These comprise systems to detect the vortices in real time, and to deploy means to suppress or otherwise ameliorate the effects of vorticity.

[0040] The vorticity detection system may further comprise at least one flow straightener at the take-off or landing site.

[0041] A take-off or landing site may comprise, but is not limited to, a runway of any one of an airport, airfield, aircraft carrier, an airstrip or any other suitable location for the takeoff or landing of a fixed-wing aircraft. A take-off or landing site may comprise a helicopter pad, helicopter deck, a vertiport or any other substantially flat surface on which a helicopter, rotorcraft or vertical take-off and landing aircraft may take-off or land.

[0042] 'At' a take-off or landing site may refer to the aircraft or to probes being positioned on or adjacent to the take-off or landing site. The term may otherwise refer to a location in proximity to the take-off or landing site. The person skilled in the art would appreciate 'in proximity' in the context of the present disclosure to be within a distance whereby local wake turbulence may disrupt flight of an aircraft.

[0043] An air traffic control centre may comprise an air traffic control tower. It may otherwise comprise a ground control centre, or a remote control centre or tower. The person skilled in the art will recognise and appreciate that an air traffic control centre may 20 02 25 refer to any suitable environment for monitoring the location of aircraft and managing the flow of aircraft traffic.

[0044] A further aspect of the disclosure provides a method for detecting vorticity at an aircraft take-off or landing site, the method comprising: providing a vorticity detection probe, configured to detect vorticity of air at an aircraft take-off or landing site; providing a measuring means, configured to detect a property of the vorticity probe, indicative of a vorticity detected by the probe; providing an output means, configured to output a vorticity output signal indicative of the vorticity detected by the measuring means; detecting vorticity at the take-off or landing site using the probe; receiving the output signal from the measuring means; communicating data based upon the vorticity output signal to an aircraft in response to the vorticity output signal.

[0045] The method may further comprise comparing the vorticity output signal to at least one stored vorticity level.

[0046] The data communicated to the aircraft may comprise one or more of: a signal representative of the detected vorticity level, a hazard alert, a flight instruction, generated in response to the vorticity output signal.

[0047] The method may further comprise providing an array of vorticity probes and wherein the measuring means is configured to detect a property of the array of vorticity probes, indicative of a vorticity detected by the array of probes.

[0048] The array of vorticity probes may comprise vane anemometers.

[0049] The measuring means may comprise an optical measuring means for measuring the movement of the probe(s). Such means may be for measuring the movement of the vane anemometers.

[0050] The method may further comprise providing at least one flow straightener, the at least one flow straightener configured to reduce vorticity at the take-off or landing site. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0052] Figure 1 is a perspective view illustrating a vortex detection means according to a first embodiment of the present invention;

[0053] Figure 2 is a schematic diagram illustrating a pressure averaging means according to a first embodiment;

[0054] Figure 3a is a front view of an aircraft according to an embodiment;

[0055] Figure 3b is a side view of the aircraft of Figure 3a;

[0056] Figure 4 is a front view of alternative configurations of the aircraft of Figure 3a;

[0057] Figure 5 is a schematic diagram illustrating a control method for a vorticity detection system in an aircraft;

[0058] Figure 6 is a graph illustrating an example of the roll output of a following aircraft when subject to turbulent local airflow;

[0059] Figure 7 is a schematic diagram illustrating an array of vorticity probes according to a second embodiment of the present invention;

[0060] Figure 8 is a schematic diagram illustrating an array of vorticity probes according to a second embodiment of the present invention;

[0061] Figure 9a is a front view of a vane vorticity probe according to a second embodiment of the present invention;

[0062] Figure 9b is a side view of a vane vorticity probe according to a second embodiment of the present invention;

[0063] Figure 10 is a front view illustrating a wind tunnel section comprising a flow straightener;

[0064] Figure 11 is a schematic diagram illustrating a flight control system; and

[0065] Figure 12 is a flow diagram illustrating a method for detecting local vorticity. DETAILED DESCRIPTION OF EMBODIMENT(S)

[0066] Figure 1 is a perspective view of a vorticity detection means 10 as described in GB2142439B. The detailed functionality of such probes is discussed in that document and is not reproduced here in the interests of efficiency of the present disclosure.

[0067] The vorticity detection means 10 comprises a first array 101 of vorticity probes 1, 3, 5, 7 and a second array 102 of vorticity probes 2, 4, 6, 8. In this embodiment, the vorticity probes may comprise four two-tube probes. Alternatively, the vorticity probes utilised in the systems described herein may comprise any other suitable form of vorticity probe. For example, the vorticity probes may comprise hot wire anemometers. Probes as described in GB2142439B have to date been employed in academic research environments to measure specific point vorticities adjacent to marine (e.g. submarines) or aeronautical (e.g. aerofoil) bodies, to determine local flow characteristics in a research environment. However, no system level implementation of such probes to assess risks presented by a measured vorticity during flight operations has been proposed.

[0068] Preferably, in one implementation of the present disclosure, vorticity probes such as the vorticity probes 1-8 of figure 1 are mounted to an aircraft to measure a level of vorticity being experienced by the aircraft. An array of such probes is preferably configured to be parallel to a longitudinal axis X of an aircraft (not shown). The plane of X = 0 in the figure defines the plane of the probe tube ends. The person skilled in the art will recognise the longitudinal axis X to be the axis about which the aircraft rolls. Preferably, the angular distance y about the longitudinal axis X between adjacent vorticity probes 1-8 is equal. In this example, the angular distance between two-tube probe 1, 8 and two-tube probe 2, 3 is 90° or radians. This is the same angular distance between two-tube probe 2, 3 and two-tube probe 4, 5. However other arrays may be implemented and the angular distances between adjacent sets of probes may vary. However, an equal spacing about the axis X can simplify signal processing calculations.

[0069] Figure 2 is a schematic diagram illustrating how outputs from an array of probes arranged as illustrated in figure 1 can be combined to provide a convenient output reflecting a measured vorticity. A first array of probes (1, 3, 5, 7) can be connected to a first signal averaging device 11. The signal averaging device 11 can be a configured to average the plurality of incoming pressure signals from the first array of probes. The signal averaging device 11 can be a manifold configured to combine the incoming pressures to output an average pressure of the pressures of the first array of probes. In an alternative arrangement, pressure signals from the first array of probes may be electronically measured using electronic pressure probes, and their signals averaged in a computing device. A second array of vorticity probes (2, 4, 6, 8) can be connected to a second signal averaging device 12 in a similar manner. Outputs of the signal averaging devices 11, 12 can be combined to give an indication of overall vorticity detected by the first and second arrays of probes. The combination of the first output and second output may comprise determining a difference between the first output and the second output. Where the difference is zero, zero vorticity is present. Where vorticity results in increased pressure in the first array, the pressure of the first array will dominate the signal and vice versa. A signal indicative of a vorticity detected by the first and second arrays of probes can thus be detected. The signal averaging and difference calculation can of course be carried out in one or more computing devices.

[0070] The first array 11 of vorticity probes (1, 3, 5, 7) can therefore be configured to detect a level of vorticity in a first direction and the second array 12 of vorticity probes (2, 4, 6, 8) can be configured to detect a level of vorticity in a second direction. The first array and the second array can therefore be configured to deliver output signals to a comparator (not shown) arranged to detect a difference in magnitude between the detected level of vorticity in the first direction and the detected level of vorticity in the second direction.

[0071] The comparator (not shown) may comprise one or more pressure sensing means. The comparator may comprise, for example, a pair of manifolds 11, 12. The comparator may comprise at least one pressure transducer, preferably a pair of pressure transducers. When the comparator comprises at least one pressure transducer, the comparator may further be configured to deliver an output signal to a computing device. The comparator can be configured to detect the pressure difference detected between the two arrays in order to detect the level of vorticity detected by the two arrays, and to output a signal indicative of the pressure difference, or indicative of the detected vorticity.

[0072] An output means (not shown) may be included in the system and is preferably arranged to output a vorticity signal indicative of the difference in magnitude between the detected level of vorticity in the first direction and the detected level of vorticity in the second direction. The output means may be, for example, a flight instrument. With this configuration, the output means can indicate the difference in the detected level of vorticity in the first direction and the detected level of vorticity in the second direction on a flight instrument to a pilot such that the pilot can make flight control inputs to counteract the detected local vorticity. The flight instrument may be a gauge comprising a dial that indicates the net detected vorticity. The flight instrument may otherwise be an electronic display. The output means may alternatively be a computing device. The computing device may be configured to output a signal to a remote location. For example, the computing device may output a signal of the difference in the detected level of vorticity in the first direction and the detected level of vorticity in the second direction to an air traffic control centre, or to an aircraft to which the probes are mounted, or to another aircraft. The aircraft may comprise a fly-by-wire or autopilot system which may be configured to receive the signal representative of the net vorticity from the computing device such that the fly-bywire or autopilot system can make flight control inputs to counteract the local vorticity. The person skilled in the art will appreciate that, in this instance, the aircraft may be manned or unmanned. The output means may be configured to a pre-set range of vorticity. In this instance the output means may be configured such that above the upper limit of the pre-set range of vorticity the output means outputs a warning signal. The warning signal may be output to a remote location. For example, the warning signal may be an audible or visual signal in a cockpit. Alternatively, the output means may be configured such that above the upper limit of the pre-set range of vorticity the output means delivers inputs to an aircraft fly-by-wire or autopilot which divert the flight path of the aircraft. For example, the output means may deliver inputs to an aircraft fly-by-wire or autopilot system which divert the aircraft to perform a go-around or other evasive manoeuvre.

[0073] Figures 3a and 3b illustrate an aircraft 30 comprising vorticity detection means, such as the vorticity detection means 10 of Figure 1.

[0074] Figure 3a is a front view of an aircraft according to a first embodiment. The aircraft 30 of Figure 3a and 3b comprises a fixed-wing arrangement, however the person skilled in the art would appreciate that the in alternative embodiments the aircraft 30 may also be implemented as a rotary wing aircraft, helicopter or rotorcraft. The aircraft 30 may therefore comprise a fixed-wing arrangement or a rotary-wing arrangement, or a combination of the two.

[0075] The illustrated aircraft 30 comprises a starboard wing 31 and a port wing 32. In this configuration, the aircraft 30 comprises a monoplane arrangement. Alternatively, the aircraft 30 may comprise a biplane arrangement. The aircraft 30 may comprise a multiplane arrangement. In the illustrated example, aft of the starboard wing 31, during flight a first wake vortex 33 may be generated. Similarly, aft of the port wing 32 a second wake vortex 34 may be generated during flight.

[0076] In the embodiment depicted in Figures 3a and 3b, the vorticity probes 1-8 are arranged around an outside of the fuselage 35 of the aircraft 30 and sufficiently distanced from the fuselage 35 to be effectively outside the boundary layer. The vorticity detection means 10 may be fixed to the fuselage 35 by any suitable means.

[0077] As can be seen in Figure 3b, the vorticity detection means 10 may be mounted on the fuselage 35 forward of the wings 31, 32. The vorticity detection means 10 is preferably placed forward of the wings 31, 32 to measure the vorticity of the local airflow before it is influenced by the aerofoil of the aircraft 30 itself. The vorticity detection means 10 is arranged such that the array of vorticity probes 1-8 are disposed outside the boundary layer 36 of local airflow over the fuselage 35 during flight. Specifically, the vorticity probes 1-8 are preferably arranged in the free stream of local airflow during flight. With this arrangement, the vorticity detection means 10 is configured to observe the local vorticity properties of the airflow around the aircraft, in the free stream of local airflow. If placed in the boundary layer 36 of the fuselage 35, the accuracy of the vorticity detected may be adversely affected by local disturbances such as turbulence in the boundary layer. The person skilled in the art will appreciate that the thickness of the boundary layer 36 varies with the configuration and flight conditions of the aircraft 30. For example, the aircraft 30 may be a conventional airliner, helicopter, rotorcraft or an unmanned air vehicle. Each of these will have different boundary layer characteristics during different modes of flight. It will also be recognised that the thickness of the boundary layer 36 is a function of the Reynolds number, which in turn depends on the speed of the local air flow. The person skilled in aircraft design will be able to calculate the expected boundary layer configuration and thickness during different flight conditions, such as at cruising speed and altitude and at speeds and altitudes expected during take-off and landing.

[0078] Figures 4a and 4b illustrate two alternative configurations of the vorticity detection means 10 on the fuselage 35 of the aircraft 30.

[0079] Figure 4a illustrates a front view of an aircraft 30 comprising a vorticity detection means 10. The vorticity detection means 10 in this example comprises three two-tube vorticity probes. There are therefore six vorticity probes 1-6. The vorticity probes 1-6 are arranged on the circumference of the fuselage of the aircraft. The angular distance about the longitudinal axis of the fuselage between the vorticity probes is substantially 120°, or radians. Figure 4b illustrates a front view of an aircraft 30 comprising a vorticity detection means 10. The vorticity detection means 10 in this example comprises five two-tube vorticity probes. There are therefore ten vorticity probes 1 to 10. The vorticity probes 1 to 10 are arranged on the circumference of the fuselage of the aircraft. The angular distance about the longitudinal axis of the fuselage between the vorticity probes is preferably substantially 72°, or|jr radians. It will therefore be understood that the vorticity detection means 10 may comprise N number of vorticity probes 1 to N. The vorticity probes 1 to N may be arranged on the circumference of a fuselage of an aircraft. The angular distance about the longitudinal axis of the fuselage between the vorticity probes 1 to N is preferably substantially °, or radians. In this configuration, the distribution of vorticity about the fuselage is observed most evenly. However, it is not essential that the probes be distributed evenly around the fuselage. It is generally beneficial to have a first array of probes arranged to detect vorticity about the fuselage in a first direction and a second array of probes arranged to detect vorticity a bout the fuselage in a second direction. It may be beneficial for these arrays to have at least some degree of symmetry about a vertical or horizontal plane of the fuselage, to gather balanced data representing the airflow around the fuselage.

[0080] Figure 5 shows schematic representation of a control system incorporating the vorticity detection means of the present disclosure. As can be seen in the figure, the vorticity detection means may comprise a vorticity probe, and may comprise one, or preferably two, arrays of vorticity probes 101 and 102. Outputs from the one or more probes may be communicated to the computing device 105 for the computing device to process the output of the one or more probes or arrays and determine a vorticity output signal, indicative of a detected level of vorticity at the probe(s). The computing device may comprise averaging means 103 to determine an average pressure reading as described above. Where the averaging means 103 are present, the output of the averaged signals may be communicated to a comparator 104 which compares the averaged output signals from the first and second arrays. The averaging means and the comparator may be logical blocks in a software module of the computing device, or may be hardware coded into a computing device using devices such as field programmable gate arrays (FPGAs) or other suitable computing circuitry. However, as described above, the averaging means may also be a manifold for averaging pressures received at the probes. The computing device may comprise the comparator and may not necessarily comprise the averaging means. The computing device 105 can thus receive an input from the probe(s) and output a signal indicative of the vorticity detected at the probe(s), which may be a vorticity output signal. The vorticity output signal can be communicated to a pilot 107 via an output device 106, such as a visual gauge, an audible signal, a numerical value or visual representation presented on a screen, or other known means for communicating flight information to a pilot. Additionally, or in the alternative, the vorticity output signal may be communicated to an autopilot 108. The pilot 107 and / or the autopilot 108 may then react to the vorticity output signal and make inputs to the flight control system 109 to make adjustments in response to the vorticity output signal. The adjustments may affect changes to flight control hardware to change the course or aerodynamics of the aircraft to compensate for the detected vorticity. Examples of a response include, adjusting the trim of the aircraft, banking up, down, left or right, by adjusting control surfaces on fixed wing aircraft or making changes to the rotors of a rotary wing aircraft or rotorcraft, any of which can be implemented in response to a vorticity output signal. Using the system described, the pilot or autopilot is therefore able to react to vorticity levels detected in the airflow in the immediate vicinity of the aircraft, i.e. adjacent a surface of the fuselage, and preferably in the freestream just outside of the boundary layer on the aircraft fuselage.

[0081] Figure 6 illustrates a graphical representation of an example of a roll moment experienced by a following aircraft when subject to turbulent local airflow, which may be generated by a leading aircraft flying upstream of the following aircraft. The following aircraft, travelling over a distance D shown in the graph may, as it encounters a first vortex, be subject to a rolling moment R.l causing it to roll left, and indicated by a first rise in the line of the graph. The following aircraft may subsequently, for example, be subject to a rolling moment Rr causing the aircraft to roll to the right, as it encounters a second vortex in the opposite direction. These rolling effects are not caused by flight control input, but rather by vorticity of the airflow about the flight path of the aircraft. Using the system described above, upon detection of an upstream vorticity at the vorticity probe or probes, the system can enable a pilot, autopilot or flight control system to counteract the roll by adjustment to the flight controls of the aircraft. Such dynamic reaction to roll input from vortices generated by leading aircraft can enable the distances between aircraft in flight to be reduced while compensating at least in part for the undesired effects of vorticity encountered by the following aircraft.

[0082] Figure 7 illustrates a scenario in which an aircraft is on the approach to a runway to make a landing. In such a scenario it can be desirable to measure vorticity levels at the landing site 65. An array of vorticity probes may be arranged at or adjacent the landing site to measure the vorticity at the vorticity probes and thus give an indication of vorticity levels at the landing site to determine whether the vorticity is at a safe level for landing and otherwise whether any adjustment may be needed to compensate for residual vorticity levels at the landing site when the aircraft 60 lands.

[0083] The landing site 65 is depicted as a runway, however could be any suitable takeoff or landing site. For example, the landing site 65 may comprise a runway of an airport, airfield, aircraft carrier, an airstrip or any other suitable location for the take-off or landing of a fixed-wing aircraft. The landing site 65 may comprise a helicopter pad, helicopter deck, a vertiport or any other substantially flat surface on which a helicopter, rotorcraft or vertical take-off and landing aircraft may take-off or land. The aircraft 60 of Figure 6 comprises a fixed-wing arrangement however the person skilled in the art would appreciate that for the purposes of the description of the benefits of the disclosed system, the aircraft 60 may also be a helicopter or a rotorcraft. The aircraft 60 thus may comprise a fixed-wing arrangement or a rotary-wing arrangement.

[0084] The aircraft 60 is flared to land on the runway 65. An array 50 of vorticity probes 64 is arranged on the runway 65. The array 50 may be arranged adjacent to the runway 65. The array 50 is preferably arranged along the flight path. The array 50 is preferably arranged on or adjacent to a non-landing portion of the runway 65 such that the array 50 of vorticity probes 64 is positioned to observe the wake turbulence of approaching aircraft whilst giving sufficient clearance for any landing aircraft or taxiing aircraft. The array 50 may be arranged to be deployed for vorticity measurements and retracted for landing of the aircraft. The array of vorticity probes is preferably arranged such that the vorticity probes 50 detect vorticity in the same plane. As in the embodiment depicted, the array 50 can be arranged orthogonally to the runway 65. Alternatively, the array 50 may be arranged to lie in a plane parallel to the runway 65. There may be a plurality of arrays, arranged either orthogonally or parallel to the runway 65. The array may comprise any number of vorticity probes, which may be arranged in rows and columns, and is depicted comprising 42 vorticity probes by way of mere example. Preferably, the array of vorticity probes comprises a sufficient number of probes to indicate the distribution of wake vortices behind an aircraft. With the arrangement of the array 50 of vorticity probes, the grid structure 52 enables the removal of the array of vorticity probes.

[0085] An array 62 of probes may otherwise be arranged with or without a grid structure adjacent to the runway 65. An array 64 of probes may also be arranged with or without a grid structure and disposed on the runway 65.

[0086] Alternatively or additionally, there may be provided an array 66 of flow straighteners. These flow straighteners may be arranged or deployed as required, on or adjacent to the runway 65. The array 66 of flow straighteners is preferably arranged such that the flow straighteners straighten the vortical flow about the longitudinal axis of the array 66 of flow straighteners. The array 66 can be arranged orthogonally to the runway 65. Alternatively, the array 66 may be arranged to lie in a plane parallel to the runway 65. There may be a plurality of arrays, arranged either orthogonally or parallel to the runway 65. The array may comprise any number of flow straighteners, which may be arranged in rows and columns. Preferably, the array of flow straighteners comprises a sufficient number of flow straighteners to straighten the flow of wake vortices behind an aircraft. Most preferably, the array 66 of flow straighteners is arranged such that the longitudinal axis of the array 66 is parallel to the runway. The flow straighteners may be introduced to a take-off or landing site after the take-off or landing of an aircraft. This reduces the vorticity of the local airflow and thus enables safe use of the runway with a reduced time separation. The function of a flow straightener is described in greater detail below, with reference to Figure 10.

[0087] Figure 8 illustrates in more detail a schematic diagram of an array 50 of vorticity probes 54.

[0088] The vorticity probes 54 can be of the kind described earlier in relation to figures 1 and 2. However, those probes require a significant incoming flow to give reliable readings of vorticity. At a landing site vorticity detection may be desirable in zero wind conditions and so alternative probes may be desirable. The probes 54 may therefore have a vane configuration. The vane vorticity probes may be feathered. The feathered configuration is such that the vanes are axially aligned, thus the vanes are only rotated by local airflow if the airflow itself is rotating. A suitable vorticity probe is illustrated in Figures 9a and 9b. The vorticity probes may be mounted on a grid structure 52. The grid structure 52 is preferably a rigid structure. The grid structure 52 is configured to carry the array 50 of vorticity probes 54 and may be arranged to be retractable toward the ground to move out of the way of incoming aircraft.

[0089] Figures 9a and 9b illustrate a vane vorticity probe 70 of a vortex detection means according to an arrangement for use in systems of the present disclosure.

[0090] The probe 70 comprises a hub 72 on which the vanes 74 are arranged. The vanes 74 are preferably removably attached to the hub. With this configuration, the vanes are more easily serviced, repaired or replaced. The vanes 74 are preferably mounted to the hub 72 by removable fixing means such as bolts. Alternatively, the vanes 74 may be mounted to the hub 72 by permanent means. The vanes 74 may be mounted to the hub by welding, for example. With this configuration, the construction of the vane vorticity probe will better withstand fatigue and thus have a longer service life. The vanes 74 are free to rotate about the longitudinal axis X of the probe. The vanes 74 are feathered to an alignment such that the vane vorticity probe 70 only rotates if the local airflow itself is rotating. Preferably, the vanes 74 are feathered by more than 70°. More preferably, the vanes 74 are feathered by more than 80°. Most preferably, the vanes 74 are feathered by 90°. Alternatively, the vanes may be feathered by equal and opposing amounts to achieve zero rotation when the air around them is not rotating. In Figures 7a and 7b, the vane vorticity probe 70 comprises four vanes 74. The vane vorticity probe 70 may comprise any number of vanes. Preferably the vane vorticity probe 70 comprises at least two vanes 74. The angular distance about the longitudinal axis of the hub 72 between adjacent vanes in the embodiment illustrated is preferably substantially 90°, or radians. It will be understood that the vane vorticity probe 70 may comprise N number of vanes. The vanes are preferably arranged on the hub 72 such that the angular distance about the longitudinal axis of the hub 72 between adjacent vanes 74 is preferably substantially °, or —n radians. It is desirable to have means for measuring the rotation of the vanes to determine local vorticity levels at the vanes. The vortex detection means preferably comprises a measuring means, configured to detect a property of at least one of the vorticity probes indicative of a vorticity detected by the probe. The measuring means preferably comprises an optical measuring means. The optical measuring means may be configured to observe the angular velocity of the vane vorticity probes 70. In low-visibility conditions, for instance fog, rain or at night time, the vane vorticity probes 70 may be illuminated. The optical measuring means may comprise one or more cameras, for example. Alternative measuring means may be envisaged, such as sensors mounted to the vanes to directly detect their rotation. The measuring means may further comprise a computing device. The computing device may be configured to convert the visual data or output from the sensors into numerical data. As the vane vorticity probes 70 are free to rotate and feathered at a high pitch angle, the angular velocity of the vane vorticity probes 70 will be substantially equal to the angular velocity of the local airflow. Therefore the vorticity, which is twice the angular velocity, of the vane vorticity probes 70 is substantially equal to the vorticity of the local airflow. Deriving the vorticity of an array of vane vorticity probes 70 therefore provides a distribution of local vorticity for the plane in which the array of vane vorticity probes is arranged.

[0091] The measuring means may comprise a pressure sensing means. For example, the measuring means may comprise a pair of chambers. In another example, the measuring means may comprise pressure transducers. The pressure transducers may further comprise a computing device.

[0092] Figure 10 illustrates a wind tunnel 75 comprising a flow straightener 76. The wind tunnel 75 depicted comprises an irregular octagonal geometry, bounded by walls 78. In an irregular octagonal geometry not all the interior angles of vertices 77 are equal. For example, in the depicted embodiment, angle A and angle B are not equal. It will be understood that angle A and angle B are selected by way of example only, and that a difference in angle may vary between any two interior angles of the wind tunnel section. The streamwise velocity of the airflow is perpendicular to the depicted plane of the section of the wind tunnel 75. The irregularity of the wind tunnel 75 geometry causes a secondary flow in close proximity to the vertices 77 of the wind tunnel 75. The arrows indicate the directions of the secondary flow. To mitigate this, flow straighteners 76 aligned to the direction of the streamwise velocity of the airflow may be fitted to the interior of the walls 78 of the wind tunnel 75.

[0093] The flow straightener 76 comprises an array of extended channels. The longitudinal axes of the extended channels 79 are parallel to the longitudinal axis of the wind tunnel. In the depicted embodiment, the extended channels 79 are cylindrical. The section of the extended channels 79 may comprise any suitable geometry such as circular, triangular, quadrilateral or any other two-dimensional geometry. Preferably, the extended channels 79 comprise a prismatic section. Specifically, it is preferable that the extended channels 79 comprise a section that is constant. Most preferably, the section of the extended channels may comprise a polygonal cross section such as a hexagonal or octagonal geometry. The array of extended channels 79 dampens the components of airflow which are lateral relative to the direction of the streamwise velocity, thus reducing vorticity. The extended channels 79 may extend longitudinally throughout the entire length of the wind tunnel. The array of extended channels 79 comprises a rectangular array in the depicted embodiment, however it may comprise any suitable geometry and is only depicted as a rectangular array by way of example. For example, the array of extended channels 79 may instead comprise a circular array, or a hexagonal array, or any other suitable geometry. With reference to the examples described in relation to Figure 7, it will now be appreciated in light of this disclosure how a flow straightener can be implemented in the examples described. Therefore, in addition to and / or independent of the means of vortex detection, devices may be deployed in order to remove, partly or completely, the vortices shed by aircraft which may cause problems for users of runways. These comprise systems to detect the vortices in real time, and to deploy means to suppress or otherwise ameliorate the effects of vorticity.

[0094] Figure 11 is a schematic diagram illustrating a flight control system. The arrows indicate communication of data. The flight control system comprises a vortex detection system 85.

[0095] The vortex detection system 85 comprises an array 86 of vorticity probes arranged at a landing site. In this example, the landing site comprises a runway, however the landing site may also comprise any suitable terrain for the take-off or landing of aircraft. The array 86 of vorticity probes in this example comprises an array of vane vorticity probes, however the array of vorticity 86 probes may comprise any suitable arrangement of vorticity probes. A measuring means 87 is arranged to detect rotation of the vorticity probes to determine vorticity local to the vorticity probes. The measuring means 87 preferably comprises an optical measuring means, configured to observe the angular velocity co of the vane vorticity probes. The measuring means 87 may also comprise a pressure sensing means, configured to observe the pressure components of the vorticity probes, if the array 86 of vorticity probes comprises two-tube vorticity probes as described in relation to earlier figures 1 and 2, for example. An output means 88 is configured to output a vorticity value indicative of the vorticity detected by the probe or probes. In this example, the output means 88 is a computing device which is configured to output a signal to a remote location. Specifically, the computing device 88 is configured to output a signal to an air traffic control centre 84. The air traffic control centre 84 may then use the vorticity data in order to determine the timing separation of aircraft using the landing site. The air traffic control centre 84 may use the data to communicate the safety level of the runway to nearby aircraft. The skilled person will understand that the remote location may comprise any suitable communication endpoint. For example, the remote location may comprise a ground control centre, or a remote control centre or tower.

[0096] An aircraft 80 which has landed is depicted schematically. The person skilled in the art will recognise that, alternatively, the following disclosure may also apply to an aircraft which has taken off as both instances can result in wake turbulence on the runway. The aircraft 80 comprises a vortex detection means further comprising two arrays of vorticity probes 81 arranged on the fuselage of the aircraft 80, though any arrangement of vorticity probes described herein may be incorporated into the aircraft 80. The first array of vorticity probes is configured to detect a level of vorticity in a first direction and the second array of vorticity probes is configured to detect a level of vorticity in a second direction. The aircraft 80 further comprises a comparator 82 arranged to detect a difference in magnitude between the detected level of vorticity in the first direction and the detected level of vorticity in the second direction.

[0097] In this example, the comparator 82 comprises a pair of manifolds which are in fluid communication with the two-tube vorticity probes via pitot tubes. The detected difference in magnitude between the detected level of vorticity in the first direction and the detected level of vorticity in the second direction from the manifolds 82 is then output to an output means 83. The output means 83 of the aircraft, in this example, comprises a flight instrument. The flight instrument 83 comprises a gauge further comprising a dial that indicates the net local vorticity and its directional tendency, being clockwise or anticlockwise.

[0098] A following aircraft 80' which is due to land is also depicted schematically. The following aircraft 80' comprises a fixed-wing arrangement and is a manned aircraft, however suitable examples are not limited to this configuration. The following aircraft 80' may otherwise comprise any suitable wing configuration and may be either manned or unmanned, including being partially automated. For the purposes of this example, the reference numerals which are the same as for the aircraft 80 represent substantially the same features but have been denoted by an inverted comma. The following aircraft 80' comprises two arrays of vorticity probes 81' arranged on the fuselage of the following aircraft 80'. The following aircraft 80' further comprises a pair of manifolds 82' and a flight instrument 83'. As above, any arrangement of vorticity probes described herein can be incorporated into the aircraft 80'. Whilst the following aircraft 80' may communicate to air traffic control 84 the level of vorticity through which it is flying, it may in turn receive communication from air traffic control 84 regarding the vorticity level detected by the vorticity detection system 87 at a take-off or landing site.

[0099] Returning to Figure 11, the first array of vorticity probes is configured to detect a level of vorticity in a first direction and the second array of vorticity probes is configured to detect a level of vorticity in a second direction. The first array and the second array are configured with the manifolds 82' arranged to detect a difference in magnitude between the detected level of vorticity in the first direction and the detected level of vorticity in the second direction. The flight instrument 83' is arranged to output a vorticity signal indicative of the difference in magnitude between the detected level of vorticity in the first direction and the detected level of vorticity in the second direction. In this example, the flight instrument 83' comprises a gauge further comprising a dial that indicates the net local vorticity and its directional tendency, being clockwise or anti-clockwise. Using these outputs, the pilot is provided with data of local vortices which can enable the pilot to counteract the disturbances.

[00100] Figure 12 depicts a flow diagram of a method according to the disclosure.

[00101] In this example an aircraft is in operation, either approaching a runway or taxiing to take-off from a runway. The method comprises providing, in a first instance, a vorticity detection means, configured to detect a property of local airflow. For example, an array of vorticity probes, the vorticity probes comprising vane vorticity meters. The array of vane vorticity meters is preferably arranged on a non-landing portion of the runway or otherwise as described in relation to Figure 7. Rotating freely, the vane vorticity meters are arranged to detect the angular velocity of the local airflow. In this example, the vane vorticity meters are feathered by 90° such that they only rotate when the airflow itself is rotating.

[00102] The method may further comprise providing a measuring means, configured to detect a property of the vorticity means indicative of a vorticity detected by the detection means. In this example, the angular velocity of the vane vorticity meters are observed optically. As the vane vorticity probes are free to rotate and feathered at a high pitch angle, the angular velocity of the vane vorticity probes will be substantially equal to the angular velocity of the local airflow. Therefore the vorticity, which is twice the angular velocity, of the vane vorticity probes is substantially equal to the vorticity of the local airflow.

[00103] The method further comprises providing an output means configured to output a signal of a vorticity value indicative of the vorticity detected by the measuring means. The output means in this example comprises a computing device, which may be configured to detect values in relation to a pre-set range of detected vorticity levels. The pre-set range of vorticity may comprise a value, above which the output means determines that the detected vorticity level represents a hazard. If the detected level of vorticity is below the pre-set value, or hazard value, of vorticity, the output means outputs a signal representative of the detected level of vorticity. In this example, the computing device outputs the detected level of vorticity to an air traffic control tower. The air traffic control tower in turn may communicate the detected level of vorticity to an aircraft in operation. The aircraft may be preparing for take-off or landing. If the detected level of vorticity is above the maximum value of the pre-set range of vorticity levels, then it is most preferable for the aircraft in operation to perform a go-around. Alternatively, between the minimum value and the maximum value of the pre-set range of values, the output means may determine a level of vorticity which may be mitigated with input to flight controls. The aircraft may comprise an automated input means, such as an autopilot or fly-by-wire system. If the aircraft comprises an automated input means, the computing device may be configured to output signals which the automated input means may input to the flight controls such that the local vorticity is counteracted. Alternatively, if the aircraft does not comprise an automated input means, the computing device may be configured to output signals to the aircraft. In this instance, the output means may further comprise a flight instrument. The pilot of the aircraft may then use these signals of vorticity to make inputs to counteract the vortical tendency of the local airflow.

[00104] The systems and methods described herein can provide cost effective means for measuring vorticity levels. Direct measurement of vorticity at points of interest, using probes located at those points of interest to give a comparison of the detected vorticity, can provide a more reliable measurement of vorticity. Further the systems can be implements in a cost effective manner, with the hardware being obtainable at far lower cost than for systems contemplated to date, such as the systems discussed in the above background section.

[00105] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

20 02 251. An aircraft comprising a vorticity detection means, the vorticity detection means comprising:an array of vorticity probes arranged to detect a level of vorticity in the air flow adjacent the aircraft;an output means, arranged to output a vorticity signal to a pilot or autopilot of the aircraft, indicative of the detected level of vorticity in the airflow adjacent the aircraft;a first array of vorticity probes configured to detect a level of vorticity in a first direction of rotation and a second array of vorticity probes configured to detect a level of vorticity in a second direction of rotation; anda comparator, arranged to detect a difference in magnitude between the detected level of vorticity in the first direction and the detected level of vorticity in the second direction;wherein the output means is arranged to output the vorticity signal indicative of the difference in magnitude between the detected level of vorticity in the first direction and the detected level of vorticity in the second direction.

2. The aircraft of claim 1, wherein the vorticity detection means comprises pressure sensing means, preferably a pressure transducer.

3. The aircraft of claim 1 or claim 2, wherein the output means comprises a flight instrument.

4. The aircraft of any preceding claim, wherein the first array and the second array have an equal number of vorticity probes to one another.

5. The aircraft of any preceding claim, wherein the output means is configured to compare the detected vorticity to a pre-set threshold level of vorticity, preferably via one or more manifolds.

6. The aircraft of claim 5, wherein the output means is configured to output a warning, and / or to send a warning output to a flight controller when vorticity exceeds the pre-set threshold level of vorticity.

7. The aircraft of any preceding claim, wherein the first array of vorticity probes and the second array of vorticity probes are arranged about the circumference of the fuselage of the aircraft.

8. The aircraft of claim 7, wherein the vorticity probes of the array are substantially evenly distributed about the longitudinal axis of the fuselage.

9. The aircraft of any of claims 7 or 8, wherein the vorticity probes are positioned to detect vorticity in the free stream of local airflow.

10. The aircraft of any of claims 7 to 9, wherein the first array of vorticity probes and the second array of vorticity probes are arranged forward of a wing section of the aircraft.20 02 25

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