CA2318804A1 - Aircraft ice detection and de-icing using lasers - Google Patents
Aircraft ice detection and de-icing using lasers Download PDFInfo
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- CA2318804A1 CA2318804A1 CA 2318804 CA2318804A CA2318804A1 CA 2318804 A1 CA2318804 A1 CA 2318804A1 CA 2318804 CA2318804 CA 2318804 CA 2318804 A CA2318804 A CA 2318804A CA 2318804 A1 CA2318804 A1 CA 2318804A1
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Abstract
An aircraft ice detection and de-icing system (10) is disclosed in which an aircraft (20) is positioned remotely from a laser beam generator (12), a beam of radiant energy (14) is reflected from a mirror (16) so that the beam (14) impinges upon an aircraft surface (18) and the mirror (16) moves the footprint (36) about the aircraft (20). The beam (14) has a wavelength that is preferentially reflected by the aircraft surface (18) and absorbed by ice, such that the beam (14) heats and removes ice from aircraft surfaces (18). A remote thermal monitoring system (22) may also be used to monitor temperatures along the surface (18) for detecting regions experiencing temperature rises at relatively increased rates as they are treated with the beam (14), thus indicating the presence of ice. A visible light beam (27) may also be used to track and indicate movement of the footprint (36) of the treating beam (14).
Description
This invention relates to aircraft ice detection and de-icing, and more particularly, to a system and method of ice detection and de-icing using lasers.
Ice formation on aircraft surfaces, particularly wing surfaces, during cold weather is a problem that can have catastrophic consequences. Ice increases aircraft weight and can reduce lift and interfere with the functioning of moving parts. A number of systems are available and in use for preventing icing or for de-icing an aircraft surface while an aircraft is 1 o in flight. Fewer options are available for detecting and removing ice from an aircraft surface while the aircraft is on the ground. Conventional aircraft de-icing systems for use on the ground are largely limited to the use of large quantities of glycol-based solutions to reduce the freezing point of ice, snow or water on an aircraft surface. During icing conditions, an aircraft waiting for take-off in a parking area is typically sprayed with a mixture of water and 15 ethylene glycol. An aircraft must often wait in line on a runway several minutes before being cleared for take-off, and during this wait, ice may of course reform on regions of the aircraft surface. When this occurs, the aircraft must be removed from the line, returned to the de-icing area and treated again.
It has been proposed to use laser light to de-ice an aircraft, using complex, bulky and 2o cumbersome booms to hold laser liglit~generators in close proximity to an aircraft surface and to manipulate the laser light generators about the aircraft surface to be de-iced. While this approach might reduce or eliminate the need to spray outer surfaces with glycol solutions, it is not without problems. For example, the need to physically manipulate the laser generators about the aircraft surface would appear to require a relatively long amount of time to treat an 25 entire aircraft and would appear to significantly limit the flexibility of the system to de-ice hard to reach regions of an aircraft surface.
Similarly, it has been proposed to use various electro-optical measurement systems for the remote detection of ice on a surface such as an aircraft surface. These systems typically rely upon changes in the phase of reflected optical energy that is related to the thickness of 3o the ice on the surface. Phase sensitive ice detection systems are extremely sensitive but are subject to many situations that inject phase differences, causing inaccuracies.
S~imm»v of the Inyg It is therefore an object of the present invention to provide a system and method of de-icing an aircraft surface using a laser beam.
It is a further object of the present invention to provide a system and method of the above type that allows the laser beam generator to be disposed remotely from the aircraft to be de-iced.
It is a still further object of the present invention to provide a system and method of the above type that permits the laser beam generator to remain stationary as the beam is moved about the aircraft surface.
to It is a still further object of the present invention to provide a system and method of the above type that permits the laser beam generator to be disposed near or below the ground or deck.
It is a still further object of the present invention to provide a system and method of the above type that permits simple telescopic frames or towers to be positioned alongside 15 decks such as ramps and runways for use with the ice detection and de-icing system.
It is a still further object of the present invention to provide a system and method of the above type that provides great flexibility in treating hard to reach regions of an aircraft surface.
It is a still further object of the present invention to provide a system and method of 2o the above type in which the directivity of the laser permits the laser to reach and treat interior compartments compartments such as air brakes and ailerons when they are opened during de-icing.
It is a still further object of the present invention to provide a system and method of the above type in which underside illumination may be used to treat landing gear and other 25 lower areas of an aircraft.
it is a still further object of the present invention to provide a system and method of the above type that permits a beam generated by a single laser beam generator to quickly and easily treat a large region on an aircraft surface without regard for whether the region is horizontal, vertical, sloping, rounded or any combination thereof.
30 It is a still further object of the present invention to provide a system and method of the above type in which a mirror is manipulated to move the footprint of the beam about an aircraft surface.
It is a still further object of the present invention to provide a system and method of the above type that provides for simultaneous remote ice detection.
. It is a still further object of the present invention to provide a system and method of the above type that uses the absorptive properties of ice, snow and water relative to the absorptive properties of an aircraft surface to remotely detect ice on the aircraft surface.
It is a still further object of the present invention to provide a system and method of the above type that monitors temperatures at the aircraft surface to remotely detect ice, snow or water thereon.
It is a still further object of the present invention to provide a system and method of 1 o the above type that remotely detects the presence of ice, snow or water on an aircraft surface by monitoring for regions experiencing temperature rises at relatively increased rates.
It is a still further object of the present invention to provide a system and method of the above type that provides for simultaneous use of a visible light source to track the footprint of the treating beam about the aircraft surface to provide a visible indication of the 15 region a being treated.
It is a still further object of the present invention to provide a system and method of the above type in which laser intensity is controllable in sub-second time scales such that the laser power can be quickly adjusted over a large range.
Toward the fulfillment of these and other objects and advantages, the aircraft ice 20 detection and de-icing system of the present invention involves positioning an aircraft remotely from a laser beam generator, reflecting a beam of radiant energy from a mirror so that the beam impinges upon and creates a footprint upon a surface of the aircraft and manipulating the mirror to move the footprint about the aircraft surface. The beam has a wavelength that is preferentially reflected by the aircraft surface and absorbed by ice, snow 25 and water, so the beam heats and removes ice, snow and water from the aircraft surface as the beam's footprint is moved thereabouts. A remote thermal monitoring system rnay also be used to monitor temperatures at the aircraft surface for detecting regions experiencing temperature rises at relatively increased rates as the regions are treated with the beam, thereby indicating the presence of ice, snow or water. A visible light may also be used 3o simultaneously to track and indicate movement of the footprint of the treating beam about the aircraft surface.
The above brief description, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of the presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a front elevation view of an ice detection and de-icing system of the present invention;
FIG 2 is a view showing overlapping footprints created on an aircraft surface by a to laser beam and visible light source in accordance with a system of the present invention;
FIG. 3 is a side elevation view of an ice detection and de-icing system of the present invention;
FIG. 4 is a schematic view of an ice detection and de-icing system of the present invention;
15 FIG. S is an elevated perspective view of an alternate embodiment of an ice detection and de-icing system of the present invention; and . FIG. 6 is an overhead schematic view of a gauntlet using an ice detection and de-icing system of the present invention.
FIG. 7 is a front elevation view of an alternate embodiment of an ice detection and de-2o icing system of the present invention; and FIG. 8 is an overhead schematic view of the alternate embodiment of FIG. 7.
Detailed Description of the Preferred mhodimp..i Referring to FIG. 1, the reference numeral 10 refers in general to ice detection and de-icing systems of the present invention. A laser beam generator 12 generates a laser beam 14 25 which passes through a salt window 1 S with wavelength selective layers and is reflected by mirrors 16 to a surface 18 of an aircraft 20. An infrared thermal camera 22 of a thermal monitoring system also generates a beam 23 which passes through a near infrared narrow band transmission filter 24 and is reflected by the salt window 15 and minors 16 to the aircraft surface 18. A visible light source 26 generates a visible light beam 27 which passes 3o through a visible narrow band transmission filter 28, is reflected by visible mirror 29 through the beam splitter 25 and is reflected by salt window 15 and mirrors 16 to the aircraft surface 18. Telescopic poles or frames 30 support mirrors 16, and drivers, motors and/or sensors, referred to individually or collectively as numeral 32, manipulate or move the mirrors 16 to move the beams 14, 23 and 27 about the aircraft surface 18.
The laser beam generator 12, preferably a COZ laser beam generator, is used to generate an efficient, high power, infrared laser beam 14. The laser efficiency is preferably within a range of approximately 30% to approximately 50%, and more preferably approximately 33%. It is understood that other laser beam generators may be used. For example, a CO laser beam generator may generate a beam approximately in the range of approximately 9 to approximately 10 micron wavelength that has similar efficiencies. The power of the generated beam 14 is preferably substantially within a range of approximately l0 50 kW to approximately 100 kW and is more preferably approximately 98 kW.
The wavelength of the beam 14 is selected from a range that is preferentially reflected by the aircraft surface 18 and absorbed by ice, snow and water 33. The wavelength is preferably substantially within a range of approximately 8 microns to approximately 15 microns, is more preferably substantially within a range of approximately 9 microns to approximately 11 microns, and is most preferably within a range of approximately 10.5 microns to approximately 10.7 microns.
The optical absorption depth of a beam 14 having a wavelength of approximately microns to 11 microns in ice, snow and water 33 is approximately 0.1 mm, so the infrared optical energy is absorbed at the surface of the ice, snow or water, and the ice, snow or water 2o is melted or evaporated selectively without significant amounts of the optical energy reaching the aircraft surface 18. In contrast, the metals comprising much of the aircraft surface 18 reflect approximately 90% to approximately 95% of optical energy at a wavelength of approximately 10 microns to approximately 11 microns, so little of the optical energy is absorbed by the metal surfaces, making it possible to use such beams without significantly 2s increasing the temperature of such metal surfaces. Composite structures located at various portions or regions of an aircraft surface 18 may be painted with a metal pigment paint to reflect the optical energy. Also, the optical absorption depth of 10 to 11 micron energy in plastic and glass is approximately 1 to 2 mm, so passengers and pilots are protected from scattered light in the unlikely event that the beam 14 is accidentally pointed at an aircraft 3o window. Similarly, work crews may be protected using protective clothing, optical glasses or goggles and helmets as would typically be worn in cold weather. As shown in FIG. 5, because COz laser systems are compact and efficient, small lasers can be used that can be ' WO 99/38774 PCT/US98/01700 mounted in a truck 34 with a turbine generator and used to de-ice engines and running gear at gates and other locations.
The mirrors 16 are high average power metal minors, such as cooled copper mirrors, similar to those developed by the military for directing laser beams in applications such as anti-missile systems for aircraft. The metal mirrors 16 expand the 50 kW laser beam 14 such that the intensity or power density is approximately equivalent to 100 kW/mz, or about 100 times that of sunlight at sea level on the equator. The mirrors 16 reflect the beams 14, 23 and 27 toward the aircraft surface 18 so that the beams 14, 23 and 27 impinge upon and create overlapping footprints 36, 38 and 40, respectively, on the aircraft surface having an area of 1o approximately 0.5 m2. Drivers or motors 32 are used to align and control movements of the mirrors 16 to permit the minors to move the reflected beams 14, 23 and 27 so that the footprint of each beam may be moved about the aircraft surface. The speed at which the footprints 36, 38 and 40 will.move across the surface 18 will vary depending upon such things as ice thickness and other conditions but can easily fall within a range of approximately 1 m/s to approximately 10 m/s. As shown in FIGS. 1 and 3, movable mirrors 16' are controlled by drivers or controllers 32' to direct the beams 14, 23 and 27 selectively to different frames 30. Germanium or salt beam splitters or laser windows may be used to pass the beam simultaneously to more than one frame 30 but are not preferred because of the cost and complexity of fabricating such beam splitters or laser windows with sufficient 2o capabilities for use with the system.
Telescopic bearri transport frames 30 provide for easy treatment of upper and lower surfaces of an aircraft 20, and the heights of the frames may be adjusted as desired for aircraft of different shapes, sizes and heights. An upper minor 16 and driver 32 are supported near the top of a frame 30 for reflecting the beams 14, 23 and 27 toward an aircraft 20 and for moving footprints 36, 38 and 40 of the beams about an aircraft surface 18. An inner bore or channel 42 extends through a central portion of the frame 30 over substantially the entire length of the frame 30, and one or more lower mirrors 16 is disposed near or below the bottom of the frame 30 and aligned for reflecting beams 14, 23 and 27 from sources 12, 22 and 26 through the bore 42 to the upper minor 16. Beam splitters 44 may be used so that a 3o single beam 14 may be split and directed to and through more than one frame 30 at a time for simultaneously treating two or more areas on an aircraft surface 18. As shown in FIGS. 1 and 3, a series of frames 30 may be positioned in a gauntlet at or near an entrance to a runway.
For remote detection of ice, the present invention uses a thermal monitoring system that is not phase sensitive and that instead relies upon the difference in absorption characteristics of ice, snow and water 33 as compared to the underlying aircraft surface 18.
As mentioned earlier, the wavelength of the beam 14 is selected from a range that is s preferentially reflected by the aircraft surface 18 and absorbed by ice, snow and water 33. In that regard, for a beam 14 having a wavelength within a range of approximately 10 microns to approximately 11 microns, the aircraft surface 18 reflects such a beam 14 with approximately 90% to 95% efficiency, whereas ice, snow and water strongly absorb such radiation.
Accordingly, as the beam 14 scans the aircraft surface 18, regions of the aircraft surface that are covered with ice, snow or water 33 will experience temperature rises at relatively increased rates as compared to regions clear thereof.
The present thermal monitoring system uses an infrared thermal camera 22 that generates a beam 23 having a wavelength different from that of beam 14. The wavelength of beam 23 is preferably within a range of approximately 1 to 2 microns and is more preferably 15 approximately 1.5 microns. As best shown in FIG. 4, the beam 23 passes from the infrared thermal camera 22 through the 1 to 2 micron near infrared narrow band transmission filter 24 and is reflected by the near infrared beam splitter 25, salt window 15 and mirrors 16 to the aircraft surface 18. The camera 22 can resolve temperature differences of approximately 1 or 2 degrees C and can create an image of a scanned aircraft surface 18 to highlight regions 2o experiencing temperature rises at relatively increased rates, indicating the presence of ice, snow or water 33 which are preferentially absorbing the long wavelength thermal energy.
The thermal monitoring system can therefore be used to detect the presence of ice, snow or water on an aircraft surface 18 and to document the location of the ice, snow or water 33 by imaging the region of interest as it is scanned. The system may also be used to determine ice 2s thickness by determining the time required to melt through the ice to the underlying reflective aircraft surface 18 using a stationary beam 14. Pre-programmed point measurement of ice thickness over the surface can also be used to build a point-by-point map of the surface ice thickness. The remote ice detection and imaging capabilities of the thermal monitoring system also permit the thermal monitoring system to continually monitor the aircraft surface 30 18 for the presence of ice, snow or water and to verify, confirm or certify that the aircraft 20 is substantially free of ice, snow or water after treatment.
For added safety, a visible Iight source 26, for example a source of a visible, low power laser beam 27, such as a red HeNe beam having a wavelength of approximately 0.62 microns, may be used in connection with the system to highlight the location of the footprint 36 of beam 14 as the beam 14 footprint 36 scans, or is moved about, the aircraft surface 18.
s As an alternative, a more efficient semiconductor laser diode may be used to generate the beam 27. The visible beam 27 passes through a visible beam narrow band transmission filter 28, is reflected by visible minor 29, passes through beam splitter 25 and is reflected by salt window 15 and mirrors 16 so that it creates a footprint 40 on the aircraft 18 that substantially overlaps with the footprints of beams 14 and 23. The footprint 40 of beam 27 also moves with the footprints 36 and 38 created by beams 14 and 23 as the footprints scan or move about the aircraft surface 18..
As indicated in FIG. 4, computer based controls 50 may be used for such things as aircraft image recognition, laser or mirror positioning and control, and temperature sensing and imaging. Image recognition may be used to identify the aircraft 20 to be de-iced and to ~ 5 follow a pre-determined scan pattern for a particular type of aircraft.
Computer controls 50 also permit instantaneous beam positioning and intensity control for safety purposes. In that regard, the laser intensity is controllable by the computer controls in a sub-second time scale such that the laser power can be adjusted over a large range, such as from approximately 10%
to approximately 100% as the beam 14 is scanned across an aircraft. The computerized 20, control 50 permits the system to recognize aircraft type, apply thermal energy in a predetermined pattern, monitor surfaces for ice, snow and water 33, control exposure for instantaneous safety control and certify aircraft condition at the end of the de-icing procedure.
In operation, an aircraft 20 is driven or moved onto a deck 52, such as a taxi way 52a, runway 52b, ramp, tarmac, parking area or other treatment area, and is positioned remotely 25 from the laser beam generator 12, thermal camera and visible light source 26. Computerized image recognition is used to identify the aircraft 20 to be de-iced and to determine the pattern for scanning the aircraft 20 with beams 14, 23 and 27. Beams 14, 23 and 27 from the laser beam generator 12, thermal camera 22 and visible light source 26 are reflected by the mirrors 16 to impinge upon and create substantially overlapping footprints 36, 38 and 40 upon the 30, aircraft surface 18. Drivers 32 manipulate the mirrors 16 to move the footprints 36, 38 and 40 of the beams about the aircraft surface in a predetermined pattern. Beam 14 melts or evaporates the ice, snow or water 33 as its footprint moves about the surface 18 of the s aircraft, and the thermal monitoring system monitors the aircraft surface for the continued presence of ice, snow or water 33.Unlike radiant systems ~or laser systems lacking the flexibility to treat hard to reach areas, the directivity of the laser beam 14 permits the present system 10 to treat interior compartments, such as air brakes and aileron, when they are opened during de-icing. In that regard, once the beam 14 enters the interior compartments, it will reflect from the metal surfaces and bounce around the interior compartment to reach most of all of the areas therein.
Upon completion of the predetermined pattern, or upon certification through the thermal monitoring system that the aircraft 20 has been placed in an acceptable condition, the 1 o system 10 is deactivated and the aircraft 20 is moved or driven on as desired. Of course, the present ice detection and de-icing system 10 may also by used in combination with other de-icing methods. For example, after de-icing an aircraft 20 using the present system, a light application of chemicals such as a glycol-based solution may be used to deter re-icing.
. The time needed to de-ice an aircraft will of course depend upon a number of factors, 15 including the amount and thickness of ice present and the number and configuration of systems 10 used. With a number of systems 10 arranged in a gauntlet configuration such as showwin FIG. 6, approximately 5 to 20 minutes should provide sufficient time for de-icing.
As best shown in FIG. 6, multiple systems 10 may be deployed along both sides of a taxi way 52a to de-ice aircraft 20 and to maintain aircraft in acceptable condition up until the time the 2o aircraft enters the main runway 52b for takeoff. This deployment also permits takeoff in either direction shortly after de-icing. The use of multiple systems provides redundancy and permits de-icing to be performed over longer periods of time if necessary or desirable.
The theoretical cost of electricity and the size of the laser required to perform melt and vaporize ice in 10 minutes according to the present invention for a wing section that is 1 m by 2s 20 m and that has a I cm layer of ice is calculated as illustrated in Table 1 below. For comparison purposes, Table 2 includes the theoretical cost of electricity and size of laser required to instead raise the temperature of a 1 m by 20 m wing section having an effective thickness of 0.5 m for melting a 1 cm layer of ice 1 in 10 minutes.
Laser Power Required to Melt Ice According to the Present Invention Ice thickness (m) ~ 0.01 Wing area height (m) 1.00 Wing area length (m) 20.00 Volume of ice (m3) 0.20 Mass of ice (kG) @ 997.1 kG/m3 199 Melting energy required (J) @ 333 kJ/kG .
6.64E+07 De-ice time (min.) 10 Average laser power required to melt ice 110 (kW) 68 Efficiency of transport .
~ 0 Efficiency of absorption .
0.75 1o Average laser power required from laser98.4 (kW) Laser efficiency 0.33 Average electrical power required (kW) 298 Average electrical power required (MW) 0.298 Energy required (kW-hr) 99 15 Energy costs ($/kW-hr) .
0.08 Electrical energy costs of melting ice $7.95 Laser Power Required to Vaporize Ice According to Present Invention Mass of ice (kG) 199 Specific energy of vaporization (kJ/kG) .
2o Energy required for vaporization (kJ) , 4.49E+OS
Energy required for melting (kJ) 6.64E+04 Total energy to melt and vaporize (kJ) . 5.1 SE+OS
De-ice time (min.) 10 Power required to melt and vaporize (kW) 859 25, Efficiency of transport 0 Efficiency of absorption .
0.75 Average laser power required from laser 1 (kW) 530 Laser efficiency , 0.33 Average electrical power required (kW) 4 ~ 630 3o , Average electrical power required (MW) 4 Energy required (kW-hr) .
Energy costs ($/kW-hr 0.08 Electrical energy cost of melting and vaporizing$6I .68 TA~LF
I
~
I
Laser Power Required to Raise Temperature of Wing Wing temperature (F) 10 Wing temperature (C) .
Desired wing temperature (F) .
4o Desired wing temperature (C) .
Effective thickness aluminum wing (m) .
Effective length of aluminum wing (m) .
Effective width of aluminum wing (m) .
Effective volume of aluminum wing {m') .
45 Density of aluminum (kG/m3) .
2,300 to Mass of aluminum (kG) 23,000 Specific heat of aluminum (kJ/kG-C) 1.05 Specific heat of ice (kJ/kG-C) 4.18 Energy necessary to raise wing temperature5.37E+08 (n Time to raise temperature of wing (min.)10 Average optical power required at surface 894 (kW) Efficiency of transport 0.75 Efficiency of absorption 0.75 Average laser power required from laser 1,590 (kW) 1o Laser efficiency 0.33 Average electrical power required (kW) 4,820 Average electrical power required (MW) 4.82 Energy required (kW-hr) 803 Energy costs ($/kW-hr) ~ 0.08 Electrical energy cost to raise wing $64.25 temperature The above results indicate that several hundred kilowatts are required to melt or melt and vaporize the ice in 10 minutes and that the energy required to melt the ice according to 2o the present invention is significantly less than that required to melt the ice by raising the temperature of the wing, although the electrical energy cost is low in both cases. The calculations suggest that a de-icing system of the present invention is feasible because commercially available COZ lasers are presently on the market with average power levels of 50 kW and larger, and lasers having power levels of several megawatts are presently in use for military purposes. The calculations suggest that the use of multiple lasers is desirable, requiring total power levels of several megawatts, which should be easily within the capability of typical power systems.
In an alternate embodiment, as depicted in FIGS. 7 and 8, a boom 54 extends between frames 30, and a plurality of mirrors 56 and 58 and presence monitors 60 are supported on the 3o boom 54 or frames 30.
Mirrors 58 are secured near upper portions of the frames 30 and direct the beam 14 to the mirrors 56. The mirrors 56 are secured to the boom 54, and drivers 62 move each mirror into or out of the path of the beam 14 as desired to selectively direct the beam 14 down to the aircraft 20. In that regard, the mirrors 56 are moved between a first position, in which the 3s beam 14 does not intercept any portion of the beam 14, and a second position, in which the mirrors 56 intercept only a portion of the beam 14. The mirrors 56 are curved so that they spread the beam out to a desired optical or thermal intensity at the surface of the aircraft 20 and so that they create a plurality of adjacent or overlapping footprints 64 at the surface of the aircraft. It is understood that additional beams, such as a beam 23 from a thermal monitoring system and a visible light beam 27 may also be routed as desired along with the beam 14 as is done in the embodiment depicted in FIG. 1.
A presence monitor 60, preferably a video camera whose image can be processed to detect the edges of an aircraft, is also supported on the boom 54 or the frames 30. Two or more presence monitors 60 are preferably used, one disposed at a center portion of the boom 54 to detect the presence or absence of a fuselage 66, one disposed remotely from the center portion to detect the presence or absence of a wing 68 and one disposed between the other two to detect the presence or absence of a tail assembly 70 of an aircraft 20.
It is understood i o that the system may be used with or without presence monitors and that presence monitors may be disposed in any number of locations. It is also understood that any conventional presence monitor may be used.
In operation, as a fuselage 66 of an aircraft moves under the boom 54, a presence monitor 60 detects the presence of the fuselage 66, and drivers 62 are activated to move one or more mirrors 56, located near a center portion of the boom 54, from the first position in which the mirrors do not intercept any portion of the beam 14 to the second position in which the mirrors 56 intercept a poition of the beam 14 and direct a portion of the beam down to the aircraft 20 to form one or more footprints 64 on the fuselage 66. As the aircraft 20 advances under the boom 54, a portion of the wings 68 moves below the boom 54. A
presence monitor 60 detects the presence of a wing 68 under the boom 54, and drivers 62 are activated to move one or more minors 56, located remotely from the center portion of the boom 54, from the first position to the second position so that the mirrors 56 intercept a portion of the beam 14 and direct a portion of the beam down to the aircraft to form one or more footprints 64 on wings 68. When the wings 68 move out from under the boom 54, a presence monitor 60 detects the absence of a wing under the boom, and the drivers 62 are activated to move mirrors 56, located remotely from the center portion of the boom 54 from the second position to the first position. A similar procedure is followed as the tail assembly 70 passes below and out from under the boom 54 and as the fuselage 66 passes out from under the boom. In one example, illustrated in FIG. 8, when the fuselage 66 first passes under the boom 54, two 3o centrally located mirrors are moved from the first position to the second position to intercept portions of the beam and to direct portions of the beam down to the aircraft to create two footprints 64 on the fuselage 66. These two minors 56 remain in the second position for the ' WO 99/38774 PCTNS98/01700 for the entire time as the fuselage 66 passes below the boom 54 and are moved back to the first position when the fuselage passes out from under the boom. When a front edge of a wing passes under the boom, all of the mirrors, or as many as are necessary to treat the entire upper wing surface, are placed in the second position to direct portions of the beam down to s create additional footprints on the wings 68. When a rear edge of one of the wings passes the boom so that the wing is no longer under the boom, all of the mirrors 56, except the centrally located mirrors treating the fuselage, are returned to the first position in which they do not intercept any portion of the beam 14. When a front edge of the tail assembly 70 passes under the boom, additional mirrors 56 adjacent to the centrally located mirrors are moved to the I o' second position to direct portions of the beam down to create footprints on the surface of the tail assembly 70. When a rear edge of the tail assembly passes the boom so that the tail assembly is not longer under the boom, all of the mirrors 56, except the centrally located mirrors treating the fuselage 66, are returned to the first position in which they do not intercept any portion of the beam 14.
I5 The laser intensity is controlled as more or fewer mirrors are moved into the path of the beam 14. For example, when ten mirrors 56 are in the path of the beam 14, illuminating the fuselage and wings, much more power is required from the laser beam generator 12 than when only two mirrors 56 are in the path of the beam 14, illuminating only the fuselage 66.
Accordingly, Iaser intensity is increased as mirrors are moved from the first position to the 20' second position in which they intercept a portion of the beam 14, and laser intensity is decreased as mirrors are moved from the second position to the first position in which the mirrors do not intercept a portion of the beam 14.
Although the alternate embodiment depicted in FIGS. 7 and 8 is primarily for treating upper surface areas of an aircraft 20, it is understood that the alternate embodiment may be 25 used in conjunction or in combination with a system or portions of a system like the one depicted in FIG. 1. In particular, a system like the one depicted in FIG. 1 may be used in conjunction or in combination with the alternate embodiment to treat lower surfaces of the aircraft. A separate laser beam generator 12 may be used.to treat lower surfaces of the aircraft, or a portion of the beam 14 may be intercepted before the beam passes to the minors 3Q 56 and 58. Similarly, although the alternate embodiment depicted in FIGS. 7 and 8 is described with the mirrors 56 disposed above the aircraft20 , one or more mirrors 56 may be disposed below an aircraft for treating lower surfaces thereof.
Other modifications, changes and substitutions are intended in the foregoing, and in some instances, some features of the invention will be employed without a corresponding use of other features. For example, although the present invention is described for use in connection with aircraft 20, the system may be used to detect and remove ice, snow and water 33 from other surfaces, as well. Also, the system may be used in connection with the removal of substances other than or in addition to ice, snow and water. Further, the ice detection system may be used regardless of whether a laser beam 14 or visible light source 26 is used for de-icing the aircraft surface 18. Similarly, the de-icing system may be used without using the ice detection system described and without using the accompanying visible light source 26 for tracking. Further still, the ice detection system may operate independently of the de-icing system, and beam 23 need not track beam 14 as the footprints 38 and 36 of the beams move about the aircraft surface 18. Also, any number of different frames 30 or supports may be used for supporting mirrors 16 above the deck, and the frames 30 or supports need not be telescopic and need not have an inner bore 42. Although a COZ laser beam 14 is preferred, any number of suitable coherent beams of radiant energy may be used, including but not limited to CO lasers. Also, although the beams 14, 23 and 27 are shown as traveling over the same path over much of their lengths, separate mirror or optical systems may be used for one or more of the beams. Of course, measurements and other numerical values given in connection with such things as preferred ranges for efficiencies, power, wavelengths and other values, are given by way of example and are not intended to limit the scope of the invention. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.
Ice formation on aircraft surfaces, particularly wing surfaces, during cold weather is a problem that can have catastrophic consequences. Ice increases aircraft weight and can reduce lift and interfere with the functioning of moving parts. A number of systems are available and in use for preventing icing or for de-icing an aircraft surface while an aircraft is 1 o in flight. Fewer options are available for detecting and removing ice from an aircraft surface while the aircraft is on the ground. Conventional aircraft de-icing systems for use on the ground are largely limited to the use of large quantities of glycol-based solutions to reduce the freezing point of ice, snow or water on an aircraft surface. During icing conditions, an aircraft waiting for take-off in a parking area is typically sprayed with a mixture of water and 15 ethylene glycol. An aircraft must often wait in line on a runway several minutes before being cleared for take-off, and during this wait, ice may of course reform on regions of the aircraft surface. When this occurs, the aircraft must be removed from the line, returned to the de-icing area and treated again.
It has been proposed to use laser light to de-ice an aircraft, using complex, bulky and 2o cumbersome booms to hold laser liglit~generators in close proximity to an aircraft surface and to manipulate the laser light generators about the aircraft surface to be de-iced. While this approach might reduce or eliminate the need to spray outer surfaces with glycol solutions, it is not without problems. For example, the need to physically manipulate the laser generators about the aircraft surface would appear to require a relatively long amount of time to treat an 25 entire aircraft and would appear to significantly limit the flexibility of the system to de-ice hard to reach regions of an aircraft surface.
Similarly, it has been proposed to use various electro-optical measurement systems for the remote detection of ice on a surface such as an aircraft surface. These systems typically rely upon changes in the phase of reflected optical energy that is related to the thickness of 3o the ice on the surface. Phase sensitive ice detection systems are extremely sensitive but are subject to many situations that inject phase differences, causing inaccuracies.
S~imm»v of the Inyg It is therefore an object of the present invention to provide a system and method of de-icing an aircraft surface using a laser beam.
It is a further object of the present invention to provide a system and method of the above type that allows the laser beam generator to be disposed remotely from the aircraft to be de-iced.
It is a still further object of the present invention to provide a system and method of the above type that permits the laser beam generator to remain stationary as the beam is moved about the aircraft surface.
to It is a still further object of the present invention to provide a system and method of the above type that permits the laser beam generator to be disposed near or below the ground or deck.
It is a still further object of the present invention to provide a system and method of the above type that permits simple telescopic frames or towers to be positioned alongside 15 decks such as ramps and runways for use with the ice detection and de-icing system.
It is a still further object of the present invention to provide a system and method of the above type that provides great flexibility in treating hard to reach regions of an aircraft surface.
It is a still further object of the present invention to provide a system and method of 2o the above type in which the directivity of the laser permits the laser to reach and treat interior compartments compartments such as air brakes and ailerons when they are opened during de-icing.
It is a still further object of the present invention to provide a system and method of the above type in which underside illumination may be used to treat landing gear and other 25 lower areas of an aircraft.
it is a still further object of the present invention to provide a system and method of the above type that permits a beam generated by a single laser beam generator to quickly and easily treat a large region on an aircraft surface without regard for whether the region is horizontal, vertical, sloping, rounded or any combination thereof.
30 It is a still further object of the present invention to provide a system and method of the above type in which a mirror is manipulated to move the footprint of the beam about an aircraft surface.
It is a still further object of the present invention to provide a system and method of the above type that provides for simultaneous remote ice detection.
. It is a still further object of the present invention to provide a system and method of the above type that uses the absorptive properties of ice, snow and water relative to the absorptive properties of an aircraft surface to remotely detect ice on the aircraft surface.
It is a still further object of the present invention to provide a system and method of the above type that monitors temperatures at the aircraft surface to remotely detect ice, snow or water thereon.
It is a still further object of the present invention to provide a system and method of 1 o the above type that remotely detects the presence of ice, snow or water on an aircraft surface by monitoring for regions experiencing temperature rises at relatively increased rates.
It is a still further object of the present invention to provide a system and method of the above type that provides for simultaneous use of a visible light source to track the footprint of the treating beam about the aircraft surface to provide a visible indication of the 15 region a being treated.
It is a still further object of the present invention to provide a system and method of the above type in which laser intensity is controllable in sub-second time scales such that the laser power can be quickly adjusted over a large range.
Toward the fulfillment of these and other objects and advantages, the aircraft ice 20 detection and de-icing system of the present invention involves positioning an aircraft remotely from a laser beam generator, reflecting a beam of radiant energy from a mirror so that the beam impinges upon and creates a footprint upon a surface of the aircraft and manipulating the mirror to move the footprint about the aircraft surface. The beam has a wavelength that is preferentially reflected by the aircraft surface and absorbed by ice, snow 25 and water, so the beam heats and removes ice, snow and water from the aircraft surface as the beam's footprint is moved thereabouts. A remote thermal monitoring system rnay also be used to monitor temperatures at the aircraft surface for detecting regions experiencing temperature rises at relatively increased rates as the regions are treated with the beam, thereby indicating the presence of ice, snow or water. A visible light may also be used 3o simultaneously to track and indicate movement of the footprint of the treating beam about the aircraft surface.
The above brief description, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of the presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a front elevation view of an ice detection and de-icing system of the present invention;
FIG 2 is a view showing overlapping footprints created on an aircraft surface by a to laser beam and visible light source in accordance with a system of the present invention;
FIG. 3 is a side elevation view of an ice detection and de-icing system of the present invention;
FIG. 4 is a schematic view of an ice detection and de-icing system of the present invention;
15 FIG. S is an elevated perspective view of an alternate embodiment of an ice detection and de-icing system of the present invention; and . FIG. 6 is an overhead schematic view of a gauntlet using an ice detection and de-icing system of the present invention.
FIG. 7 is a front elevation view of an alternate embodiment of an ice detection and de-2o icing system of the present invention; and FIG. 8 is an overhead schematic view of the alternate embodiment of FIG. 7.
Detailed Description of the Preferred mhodimp..i Referring to FIG. 1, the reference numeral 10 refers in general to ice detection and de-icing systems of the present invention. A laser beam generator 12 generates a laser beam 14 25 which passes through a salt window 1 S with wavelength selective layers and is reflected by mirrors 16 to a surface 18 of an aircraft 20. An infrared thermal camera 22 of a thermal monitoring system also generates a beam 23 which passes through a near infrared narrow band transmission filter 24 and is reflected by the salt window 15 and minors 16 to the aircraft surface 18. A visible light source 26 generates a visible light beam 27 which passes 3o through a visible narrow band transmission filter 28, is reflected by visible mirror 29 through the beam splitter 25 and is reflected by salt window 15 and mirrors 16 to the aircraft surface 18. Telescopic poles or frames 30 support mirrors 16, and drivers, motors and/or sensors, referred to individually or collectively as numeral 32, manipulate or move the mirrors 16 to move the beams 14, 23 and 27 about the aircraft surface 18.
The laser beam generator 12, preferably a COZ laser beam generator, is used to generate an efficient, high power, infrared laser beam 14. The laser efficiency is preferably within a range of approximately 30% to approximately 50%, and more preferably approximately 33%. It is understood that other laser beam generators may be used. For example, a CO laser beam generator may generate a beam approximately in the range of approximately 9 to approximately 10 micron wavelength that has similar efficiencies. The power of the generated beam 14 is preferably substantially within a range of approximately l0 50 kW to approximately 100 kW and is more preferably approximately 98 kW.
The wavelength of the beam 14 is selected from a range that is preferentially reflected by the aircraft surface 18 and absorbed by ice, snow and water 33. The wavelength is preferably substantially within a range of approximately 8 microns to approximately 15 microns, is more preferably substantially within a range of approximately 9 microns to approximately 11 microns, and is most preferably within a range of approximately 10.5 microns to approximately 10.7 microns.
The optical absorption depth of a beam 14 having a wavelength of approximately microns to 11 microns in ice, snow and water 33 is approximately 0.1 mm, so the infrared optical energy is absorbed at the surface of the ice, snow or water, and the ice, snow or water 2o is melted or evaporated selectively without significant amounts of the optical energy reaching the aircraft surface 18. In contrast, the metals comprising much of the aircraft surface 18 reflect approximately 90% to approximately 95% of optical energy at a wavelength of approximately 10 microns to approximately 11 microns, so little of the optical energy is absorbed by the metal surfaces, making it possible to use such beams without significantly 2s increasing the temperature of such metal surfaces. Composite structures located at various portions or regions of an aircraft surface 18 may be painted with a metal pigment paint to reflect the optical energy. Also, the optical absorption depth of 10 to 11 micron energy in plastic and glass is approximately 1 to 2 mm, so passengers and pilots are protected from scattered light in the unlikely event that the beam 14 is accidentally pointed at an aircraft 3o window. Similarly, work crews may be protected using protective clothing, optical glasses or goggles and helmets as would typically be worn in cold weather. As shown in FIG. 5, because COz laser systems are compact and efficient, small lasers can be used that can be ' WO 99/38774 PCT/US98/01700 mounted in a truck 34 with a turbine generator and used to de-ice engines and running gear at gates and other locations.
The mirrors 16 are high average power metal minors, such as cooled copper mirrors, similar to those developed by the military for directing laser beams in applications such as anti-missile systems for aircraft. The metal mirrors 16 expand the 50 kW laser beam 14 such that the intensity or power density is approximately equivalent to 100 kW/mz, or about 100 times that of sunlight at sea level on the equator. The mirrors 16 reflect the beams 14, 23 and 27 toward the aircraft surface 18 so that the beams 14, 23 and 27 impinge upon and create overlapping footprints 36, 38 and 40, respectively, on the aircraft surface having an area of 1o approximately 0.5 m2. Drivers or motors 32 are used to align and control movements of the mirrors 16 to permit the minors to move the reflected beams 14, 23 and 27 so that the footprint of each beam may be moved about the aircraft surface. The speed at which the footprints 36, 38 and 40 will.move across the surface 18 will vary depending upon such things as ice thickness and other conditions but can easily fall within a range of approximately 1 m/s to approximately 10 m/s. As shown in FIGS. 1 and 3, movable mirrors 16' are controlled by drivers or controllers 32' to direct the beams 14, 23 and 27 selectively to different frames 30. Germanium or salt beam splitters or laser windows may be used to pass the beam simultaneously to more than one frame 30 but are not preferred because of the cost and complexity of fabricating such beam splitters or laser windows with sufficient 2o capabilities for use with the system.
Telescopic bearri transport frames 30 provide for easy treatment of upper and lower surfaces of an aircraft 20, and the heights of the frames may be adjusted as desired for aircraft of different shapes, sizes and heights. An upper minor 16 and driver 32 are supported near the top of a frame 30 for reflecting the beams 14, 23 and 27 toward an aircraft 20 and for moving footprints 36, 38 and 40 of the beams about an aircraft surface 18. An inner bore or channel 42 extends through a central portion of the frame 30 over substantially the entire length of the frame 30, and one or more lower mirrors 16 is disposed near or below the bottom of the frame 30 and aligned for reflecting beams 14, 23 and 27 from sources 12, 22 and 26 through the bore 42 to the upper minor 16. Beam splitters 44 may be used so that a 3o single beam 14 may be split and directed to and through more than one frame 30 at a time for simultaneously treating two or more areas on an aircraft surface 18. As shown in FIGS. 1 and 3, a series of frames 30 may be positioned in a gauntlet at or near an entrance to a runway.
For remote detection of ice, the present invention uses a thermal monitoring system that is not phase sensitive and that instead relies upon the difference in absorption characteristics of ice, snow and water 33 as compared to the underlying aircraft surface 18.
As mentioned earlier, the wavelength of the beam 14 is selected from a range that is s preferentially reflected by the aircraft surface 18 and absorbed by ice, snow and water 33. In that regard, for a beam 14 having a wavelength within a range of approximately 10 microns to approximately 11 microns, the aircraft surface 18 reflects such a beam 14 with approximately 90% to 95% efficiency, whereas ice, snow and water strongly absorb such radiation.
Accordingly, as the beam 14 scans the aircraft surface 18, regions of the aircraft surface that are covered with ice, snow or water 33 will experience temperature rises at relatively increased rates as compared to regions clear thereof.
The present thermal monitoring system uses an infrared thermal camera 22 that generates a beam 23 having a wavelength different from that of beam 14. The wavelength of beam 23 is preferably within a range of approximately 1 to 2 microns and is more preferably 15 approximately 1.5 microns. As best shown in FIG. 4, the beam 23 passes from the infrared thermal camera 22 through the 1 to 2 micron near infrared narrow band transmission filter 24 and is reflected by the near infrared beam splitter 25, salt window 15 and mirrors 16 to the aircraft surface 18. The camera 22 can resolve temperature differences of approximately 1 or 2 degrees C and can create an image of a scanned aircraft surface 18 to highlight regions 2o experiencing temperature rises at relatively increased rates, indicating the presence of ice, snow or water 33 which are preferentially absorbing the long wavelength thermal energy.
The thermal monitoring system can therefore be used to detect the presence of ice, snow or water on an aircraft surface 18 and to document the location of the ice, snow or water 33 by imaging the region of interest as it is scanned. The system may also be used to determine ice 2s thickness by determining the time required to melt through the ice to the underlying reflective aircraft surface 18 using a stationary beam 14. Pre-programmed point measurement of ice thickness over the surface can also be used to build a point-by-point map of the surface ice thickness. The remote ice detection and imaging capabilities of the thermal monitoring system also permit the thermal monitoring system to continually monitor the aircraft surface 30 18 for the presence of ice, snow or water and to verify, confirm or certify that the aircraft 20 is substantially free of ice, snow or water after treatment.
For added safety, a visible Iight source 26, for example a source of a visible, low power laser beam 27, such as a red HeNe beam having a wavelength of approximately 0.62 microns, may be used in connection with the system to highlight the location of the footprint 36 of beam 14 as the beam 14 footprint 36 scans, or is moved about, the aircraft surface 18.
s As an alternative, a more efficient semiconductor laser diode may be used to generate the beam 27. The visible beam 27 passes through a visible beam narrow band transmission filter 28, is reflected by visible minor 29, passes through beam splitter 25 and is reflected by salt window 15 and mirrors 16 so that it creates a footprint 40 on the aircraft 18 that substantially overlaps with the footprints of beams 14 and 23. The footprint 40 of beam 27 also moves with the footprints 36 and 38 created by beams 14 and 23 as the footprints scan or move about the aircraft surface 18..
As indicated in FIG. 4, computer based controls 50 may be used for such things as aircraft image recognition, laser or mirror positioning and control, and temperature sensing and imaging. Image recognition may be used to identify the aircraft 20 to be de-iced and to ~ 5 follow a pre-determined scan pattern for a particular type of aircraft.
Computer controls 50 also permit instantaneous beam positioning and intensity control for safety purposes. In that regard, the laser intensity is controllable by the computer controls in a sub-second time scale such that the laser power can be adjusted over a large range, such as from approximately 10%
to approximately 100% as the beam 14 is scanned across an aircraft. The computerized 20, control 50 permits the system to recognize aircraft type, apply thermal energy in a predetermined pattern, monitor surfaces for ice, snow and water 33, control exposure for instantaneous safety control and certify aircraft condition at the end of the de-icing procedure.
In operation, an aircraft 20 is driven or moved onto a deck 52, such as a taxi way 52a, runway 52b, ramp, tarmac, parking area or other treatment area, and is positioned remotely 25 from the laser beam generator 12, thermal camera and visible light source 26. Computerized image recognition is used to identify the aircraft 20 to be de-iced and to determine the pattern for scanning the aircraft 20 with beams 14, 23 and 27. Beams 14, 23 and 27 from the laser beam generator 12, thermal camera 22 and visible light source 26 are reflected by the mirrors 16 to impinge upon and create substantially overlapping footprints 36, 38 and 40 upon the 30, aircraft surface 18. Drivers 32 manipulate the mirrors 16 to move the footprints 36, 38 and 40 of the beams about the aircraft surface in a predetermined pattern. Beam 14 melts or evaporates the ice, snow or water 33 as its footprint moves about the surface 18 of the s aircraft, and the thermal monitoring system monitors the aircraft surface for the continued presence of ice, snow or water 33.Unlike radiant systems ~or laser systems lacking the flexibility to treat hard to reach areas, the directivity of the laser beam 14 permits the present system 10 to treat interior compartments, such as air brakes and aileron, when they are opened during de-icing. In that regard, once the beam 14 enters the interior compartments, it will reflect from the metal surfaces and bounce around the interior compartment to reach most of all of the areas therein.
Upon completion of the predetermined pattern, or upon certification through the thermal monitoring system that the aircraft 20 has been placed in an acceptable condition, the 1 o system 10 is deactivated and the aircraft 20 is moved or driven on as desired. Of course, the present ice detection and de-icing system 10 may also by used in combination with other de-icing methods. For example, after de-icing an aircraft 20 using the present system, a light application of chemicals such as a glycol-based solution may be used to deter re-icing.
. The time needed to de-ice an aircraft will of course depend upon a number of factors, 15 including the amount and thickness of ice present and the number and configuration of systems 10 used. With a number of systems 10 arranged in a gauntlet configuration such as showwin FIG. 6, approximately 5 to 20 minutes should provide sufficient time for de-icing.
As best shown in FIG. 6, multiple systems 10 may be deployed along both sides of a taxi way 52a to de-ice aircraft 20 and to maintain aircraft in acceptable condition up until the time the 2o aircraft enters the main runway 52b for takeoff. This deployment also permits takeoff in either direction shortly after de-icing. The use of multiple systems provides redundancy and permits de-icing to be performed over longer periods of time if necessary or desirable.
The theoretical cost of electricity and the size of the laser required to perform melt and vaporize ice in 10 minutes according to the present invention for a wing section that is 1 m by 2s 20 m and that has a I cm layer of ice is calculated as illustrated in Table 1 below. For comparison purposes, Table 2 includes the theoretical cost of electricity and size of laser required to instead raise the temperature of a 1 m by 20 m wing section having an effective thickness of 0.5 m for melting a 1 cm layer of ice 1 in 10 minutes.
Laser Power Required to Melt Ice According to the Present Invention Ice thickness (m) ~ 0.01 Wing area height (m) 1.00 Wing area length (m) 20.00 Volume of ice (m3) 0.20 Mass of ice (kG) @ 997.1 kG/m3 199 Melting energy required (J) @ 333 kJ/kG .
6.64E+07 De-ice time (min.) 10 Average laser power required to melt ice 110 (kW) 68 Efficiency of transport .
~ 0 Efficiency of absorption .
0.75 1o Average laser power required from laser98.4 (kW) Laser efficiency 0.33 Average electrical power required (kW) 298 Average electrical power required (MW) 0.298 Energy required (kW-hr) 99 15 Energy costs ($/kW-hr) .
0.08 Electrical energy costs of melting ice $7.95 Laser Power Required to Vaporize Ice According to Present Invention Mass of ice (kG) 199 Specific energy of vaporization (kJ/kG) .
2o Energy required for vaporization (kJ) , 4.49E+OS
Energy required for melting (kJ) 6.64E+04 Total energy to melt and vaporize (kJ) . 5.1 SE+OS
De-ice time (min.) 10 Power required to melt and vaporize (kW) 859 25, Efficiency of transport 0 Efficiency of absorption .
0.75 Average laser power required from laser 1 (kW) 530 Laser efficiency , 0.33 Average electrical power required (kW) 4 ~ 630 3o , Average electrical power required (MW) 4 Energy required (kW-hr) .
Energy costs ($/kW-hr 0.08 Electrical energy cost of melting and vaporizing$6I .68 TA~LF
I
~
I
Laser Power Required to Raise Temperature of Wing Wing temperature (F) 10 Wing temperature (C) .
Desired wing temperature (F) .
4o Desired wing temperature (C) .
Effective thickness aluminum wing (m) .
Effective length of aluminum wing (m) .
Effective width of aluminum wing (m) .
Effective volume of aluminum wing {m') .
45 Density of aluminum (kG/m3) .
2,300 to Mass of aluminum (kG) 23,000 Specific heat of aluminum (kJ/kG-C) 1.05 Specific heat of ice (kJ/kG-C) 4.18 Energy necessary to raise wing temperature5.37E+08 (n Time to raise temperature of wing (min.)10 Average optical power required at surface 894 (kW) Efficiency of transport 0.75 Efficiency of absorption 0.75 Average laser power required from laser 1,590 (kW) 1o Laser efficiency 0.33 Average electrical power required (kW) 4,820 Average electrical power required (MW) 4.82 Energy required (kW-hr) 803 Energy costs ($/kW-hr) ~ 0.08 Electrical energy cost to raise wing $64.25 temperature The above results indicate that several hundred kilowatts are required to melt or melt and vaporize the ice in 10 minutes and that the energy required to melt the ice according to 2o the present invention is significantly less than that required to melt the ice by raising the temperature of the wing, although the electrical energy cost is low in both cases. The calculations suggest that a de-icing system of the present invention is feasible because commercially available COZ lasers are presently on the market with average power levels of 50 kW and larger, and lasers having power levels of several megawatts are presently in use for military purposes. The calculations suggest that the use of multiple lasers is desirable, requiring total power levels of several megawatts, which should be easily within the capability of typical power systems.
In an alternate embodiment, as depicted in FIGS. 7 and 8, a boom 54 extends between frames 30, and a plurality of mirrors 56 and 58 and presence monitors 60 are supported on the 3o boom 54 or frames 30.
Mirrors 58 are secured near upper portions of the frames 30 and direct the beam 14 to the mirrors 56. The mirrors 56 are secured to the boom 54, and drivers 62 move each mirror into or out of the path of the beam 14 as desired to selectively direct the beam 14 down to the aircraft 20. In that regard, the mirrors 56 are moved between a first position, in which the 3s beam 14 does not intercept any portion of the beam 14, and a second position, in which the mirrors 56 intercept only a portion of the beam 14. The mirrors 56 are curved so that they spread the beam out to a desired optical or thermal intensity at the surface of the aircraft 20 and so that they create a plurality of adjacent or overlapping footprints 64 at the surface of the aircraft. It is understood that additional beams, such as a beam 23 from a thermal monitoring system and a visible light beam 27 may also be routed as desired along with the beam 14 as is done in the embodiment depicted in FIG. 1.
A presence monitor 60, preferably a video camera whose image can be processed to detect the edges of an aircraft, is also supported on the boom 54 or the frames 30. Two or more presence monitors 60 are preferably used, one disposed at a center portion of the boom 54 to detect the presence or absence of a fuselage 66, one disposed remotely from the center portion to detect the presence or absence of a wing 68 and one disposed between the other two to detect the presence or absence of a tail assembly 70 of an aircraft 20.
It is understood i o that the system may be used with or without presence monitors and that presence monitors may be disposed in any number of locations. It is also understood that any conventional presence monitor may be used.
In operation, as a fuselage 66 of an aircraft moves under the boom 54, a presence monitor 60 detects the presence of the fuselage 66, and drivers 62 are activated to move one or more mirrors 56, located near a center portion of the boom 54, from the first position in which the mirrors do not intercept any portion of the beam 14 to the second position in which the mirrors 56 intercept a poition of the beam 14 and direct a portion of the beam down to the aircraft 20 to form one or more footprints 64 on the fuselage 66. As the aircraft 20 advances under the boom 54, a portion of the wings 68 moves below the boom 54. A
presence monitor 60 detects the presence of a wing 68 under the boom 54, and drivers 62 are activated to move one or more minors 56, located remotely from the center portion of the boom 54, from the first position to the second position so that the mirrors 56 intercept a portion of the beam 14 and direct a portion of the beam down to the aircraft to form one or more footprints 64 on wings 68. When the wings 68 move out from under the boom 54, a presence monitor 60 detects the absence of a wing under the boom, and the drivers 62 are activated to move mirrors 56, located remotely from the center portion of the boom 54 from the second position to the first position. A similar procedure is followed as the tail assembly 70 passes below and out from under the boom 54 and as the fuselage 66 passes out from under the boom. In one example, illustrated in FIG. 8, when the fuselage 66 first passes under the boom 54, two 3o centrally located mirrors are moved from the first position to the second position to intercept portions of the beam and to direct portions of the beam down to the aircraft to create two footprints 64 on the fuselage 66. These two minors 56 remain in the second position for the ' WO 99/38774 PCTNS98/01700 for the entire time as the fuselage 66 passes below the boom 54 and are moved back to the first position when the fuselage passes out from under the boom. When a front edge of a wing passes under the boom, all of the mirrors, or as many as are necessary to treat the entire upper wing surface, are placed in the second position to direct portions of the beam down to s create additional footprints on the wings 68. When a rear edge of one of the wings passes the boom so that the wing is no longer under the boom, all of the mirrors 56, except the centrally located mirrors treating the fuselage, are returned to the first position in which they do not intercept any portion of the beam 14. When a front edge of the tail assembly 70 passes under the boom, additional mirrors 56 adjacent to the centrally located mirrors are moved to the I o' second position to direct portions of the beam down to create footprints on the surface of the tail assembly 70. When a rear edge of the tail assembly passes the boom so that the tail assembly is not longer under the boom, all of the mirrors 56, except the centrally located mirrors treating the fuselage 66, are returned to the first position in which they do not intercept any portion of the beam 14.
I5 The laser intensity is controlled as more or fewer mirrors are moved into the path of the beam 14. For example, when ten mirrors 56 are in the path of the beam 14, illuminating the fuselage and wings, much more power is required from the laser beam generator 12 than when only two mirrors 56 are in the path of the beam 14, illuminating only the fuselage 66.
Accordingly, Iaser intensity is increased as mirrors are moved from the first position to the 20' second position in which they intercept a portion of the beam 14, and laser intensity is decreased as mirrors are moved from the second position to the first position in which the mirrors do not intercept a portion of the beam 14.
Although the alternate embodiment depicted in FIGS. 7 and 8 is primarily for treating upper surface areas of an aircraft 20, it is understood that the alternate embodiment may be 25 used in conjunction or in combination with a system or portions of a system like the one depicted in FIG. 1. In particular, a system like the one depicted in FIG. 1 may be used in conjunction or in combination with the alternate embodiment to treat lower surfaces of the aircraft. A separate laser beam generator 12 may be used.to treat lower surfaces of the aircraft, or a portion of the beam 14 may be intercepted before the beam passes to the minors 3Q 56 and 58. Similarly, although the alternate embodiment depicted in FIGS. 7 and 8 is described with the mirrors 56 disposed above the aircraft20 , one or more mirrors 56 may be disposed below an aircraft for treating lower surfaces thereof.
Other modifications, changes and substitutions are intended in the foregoing, and in some instances, some features of the invention will be employed without a corresponding use of other features. For example, although the present invention is described for use in connection with aircraft 20, the system may be used to detect and remove ice, snow and water 33 from other surfaces, as well. Also, the system may be used in connection with the removal of substances other than or in addition to ice, snow and water. Further, the ice detection system may be used regardless of whether a laser beam 14 or visible light source 26 is used for de-icing the aircraft surface 18. Similarly, the de-icing system may be used without using the ice detection system described and without using the accompanying visible light source 26 for tracking. Further still, the ice detection system may operate independently of the de-icing system, and beam 23 need not track beam 14 as the footprints 38 and 36 of the beams move about the aircraft surface 18. Also, any number of different frames 30 or supports may be used for supporting mirrors 16 above the deck, and the frames 30 or supports need not be telescopic and need not have an inner bore 42. Although a COZ laser beam 14 is preferred, any number of suitable coherent beams of radiant energy may be used, including but not limited to CO lasers. Also, although the beams 14, 23 and 27 are shown as traveling over the same path over much of their lengths, separate mirror or optical systems may be used for one or more of the beams. Of course, measurements and other numerical values given in connection with such things as preferred ranges for efficiencies, power, wavelengths and other values, are given by way of example and are not intended to limit the scope of the invention. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.
Claims (27)
1. A method of de-icing an aircraft comprising:
(a) positioning an aircraft to be de-iced remotely from a laser beam generator;
(b) reflecting a first beam of radiant energy generated by said laser beam generator from a first mirror so that said reflected first beam impinges upon and creates a first footprint upon a surface of said aircraft, said first beam having a first wavelength substantially within a range that is preferentially reflected by said aircraft surface and absorbed by ice, snow or water on said aircraft surface;
and (c) manipulating said first mirror to move said first footprint about said aircraft surface for removing ice, snow or water from said aircraft surface.
(a) positioning an aircraft to be de-iced remotely from a laser beam generator;
(b) reflecting a first beam of radiant energy generated by said laser beam generator from a first mirror so that said reflected first beam impinges upon and creates a first footprint upon a surface of said aircraft, said first beam having a first wavelength substantially within a range that is preferentially reflected by said aircraft surface and absorbed by ice, snow or water on said aircraft surface;
and (c) manipulating said first mirror to move said first footprint about said aircraft surface for removing ice, snow or water from said aircraft surface.
2. The method of claim 1 wherein said first wavelength is substantially within a range of approximately 8 microns to 15 microns.
3. The method of claim 2 further comprising monitoring temperatures at said aircraft surface to detect regions experiencing temperature rises at relatively increased rates.
4. The method of claim 1 further comprising:
providing an ice detection system disposed remotely from said aircraft; and monitoring said aircraft surface for the presence of ice, snow or water.
providing an ice detection system disposed remotely from said aircraft; and monitoring said aircraft surface for the presence of ice, snow or water.
5. The method of 4 wherein:
said ice detection system comprises a thermal monitoring system that uses an infrared thermal camera to generate a second beam of radiant energy having a second wavelength to monitor temperatures at said aircraft surface; and said step of monitoring said aircraft surface for the presence of ice, snow or water comprises monitoring temperatures at said aircraft surface to detect regions experiencing temperature rises at relatively increased rates.
said ice detection system comprises a thermal monitoring system that uses an infrared thermal camera to generate a second beam of radiant energy having a second wavelength to monitor temperatures at said aircraft surface; and said step of monitoring said aircraft surface for the presence of ice, snow or water comprises monitoring temperatures at said aircraft surface to detect regions experiencing temperature rises at relatively increased rates.
6. The method of claim 5 wherein said first wavelength is substantially within a range of approximately 8 microns to approximately 15 microns and said second wavelength is substantially within a range of approximately 0.8 microns to approximately 2.2 microns.
7. The method of claim 1 further comprising:
reflecting a third beam of radiant energy, having a third wavelength substantially within a range of visible light, from said first mirror so that said reflected third beam impinges upon and creates a third footprint upon a surface of said aircraft that at least in part overlaps said first footprint.
reflecting a third beam of radiant energy, having a third wavelength substantially within a range of visible light, from said first mirror so that said reflected third beam impinges upon and creates a third footprint upon a surface of said aircraft that at least in part overlaps said first footprint.
8. The method of claim 5 wherein said second beam creates a second footprint upon said aircraft surface that at least in part overlaps said first footprint, and further comprising:
reflecting a third beam of radiant energy, having a third wavelength substantially within a range of visible light, from said first mirror so that said reflected third beam impinges upon and creates a third footprint upon said aircraft surface that at least in part overlaps said first and second footprints.
reflecting a third beam of radiant energy, having a third wavelength substantially within a range of visible light, from said first mirror so that said reflected third beam impinges upon and creates a third footprint upon said aircraft surface that at least in part overlaps said first and second footprints.
9. The method of claim 1 further comprising:
positioning said laser beam generator substantially below said aircraft;
supporting said first minor from a first frame having an inner bore; and passing said first beam through said bore of said first frame before said first beam strikes said first mirror.
positioning said laser beam generator substantially below said aircraft;
supporting said first minor from a first frame having an inner bore; and passing said first beam through said bore of said first frame before said first beam strikes said first mirror.
10. The method of claim 5 wherein said second beam is reflected from said first mirror to create a second footprint upon said aircraft surface, and further comprising:
positioning said laser beam generator and said infrared thermal camera substantially below said aircraft;
supporting said first mirror from a first frame having an inner bore; and passing said first and second beams through said bore of said first frame before said first and second beams strike said first mirror.
positioning said laser beam generator and said infrared thermal camera substantially below said aircraft;
supporting said first mirror from a first frame having an inner bore; and passing said first and second beams through said bore of said first frame before said first and second beams strike said first mirror.
11. The method of claim 9, further comprising:
supporting a second mirror from a second frame at a height lower than said first mirror, said second frame having an inner bore;
reflecting a fourth beam of radiant energy generated by said laser beam generator from a second mirror, after passing through said bore of said second frame, so that said reflected fourth beam impinges upon and creates a fourth footprint upon a surface of said aircraft, said fourth beam having a fourth wavelength substantially equal to said first wavelength; and manipulating said second mirror to move said fourth footprint about said aircraft surface for removing ice, snow or water from said aircraft surface.
supporting a second mirror from a second frame at a height lower than said first mirror, said second frame having an inner bore;
reflecting a fourth beam of radiant energy generated by said laser beam generator from a second mirror, after passing through said bore of said second frame, so that said reflected fourth beam impinges upon and creates a fourth footprint upon a surface of said aircraft, said fourth beam having a fourth wavelength substantially equal to said first wavelength; and manipulating said second mirror to move said fourth footprint about said aircraft surface for removing ice, snow or water from said aircraft surface.
12. A system for de-icing an aircraft, comprising:
(a) a deck for supporting an aircraft to be. de-iced;
(b) a laser beam generator for generating a first beam of radiant energy having a wavelength substantially within a range of approximately 8 microns to approximately 15 microns, said generator being disposed remotely from said aircraft, near or below said deck and in a substantially stationary position relative to said deck;
(c) a frame having an inner bore, at least a portion of said frame extending above said deck;
(d) a first mirror supported above said deck by said first frame for reflecting said first beam toward said aircraft to create a first footprint upon a surface of said aircraft;
(e) a driver operatively connected to said first mirror to manipulate said first mirror for moving said footprint about said surface of said aircraft; and (f) a second mirror disposed near a lower portion of said frame and positioned to reflect said first beam from said generator, through said bore and to said first mirror.
(a) a deck for supporting an aircraft to be. de-iced;
(b) a laser beam generator for generating a first beam of radiant energy having a wavelength substantially within a range of approximately 8 microns to approximately 15 microns, said generator being disposed remotely from said aircraft, near or below said deck and in a substantially stationary position relative to said deck;
(c) a frame having an inner bore, at least a portion of said frame extending above said deck;
(d) a first mirror supported above said deck by said first frame for reflecting said first beam toward said aircraft to create a first footprint upon a surface of said aircraft;
(e) a driver operatively connected to said first mirror to manipulate said first mirror for moving said footprint about said surface of said aircraft; and (f) a second mirror disposed near a lower portion of said frame and positioned to reflect said first beam from said generator, through said bore and to said first mirror.
13. The system of claim 12, further comprising:
an infrared thermal camera disposed remotely from said aircraft, near or below said deck and in a substantially stationary position relative to said deck, said camera using a second beam having a second wavelength for measuring temperatures at said aircraft surface, and said camera being aligned to direct said second beam to said second mirror, through said bore and to said first mirror which reflects said second beam toward said aircraft to create a second footprint upon said surface of said aircraft.
an infrared thermal camera disposed remotely from said aircraft, near or below said deck and in a substantially stationary position relative to said deck, said camera using a second beam having a second wavelength for measuring temperatures at said aircraft surface, and said camera being aligned to direct said second beam to said second mirror, through said bore and to said first mirror which reflects said second beam toward said aircraft to create a second footprint upon said surface of said aircraft.
14. The system of claim 13, further comprising:
a light source for generating a third beam of radiant energy, having a third wavelength substantially within a range of visible light, disposed remotely from said aircraft, near or below said deck and in a substantially stationary position relative to said deck, said light source being aligned to direct said third beam to said second mirror, through said bore and to said first mirror which reflects said third beam toward said aircraft to create a third footprint upon said surface of said aircraft.
a light source for generating a third beam of radiant energy, having a third wavelength substantially within a range of visible light, disposed remotely from said aircraft, near or below said deck and in a substantially stationary position relative to said deck, said light source being aligned to direct said third beam to said second mirror, through said bore and to said first mirror which reflects said third beam toward said aircraft to create a third footprint upon said surface of said aircraft.
15. The system of claim 14 wherein said frame is telescopic and permits height adjustments of said first mirror.
16. A method for detecting ice, snow or water on an aircraft, comprising:
(a) scanning a surface of an aircraft with a first beam of radiant energy having a first wavelength substantially within a range that is preferentially reflected by said aircraft surface and absorbed by ice, snow or water; and (b) monitoring temperatures at said aircraft surface to detect regions experiencing temperature rises at relatively increased rates, thereby indicating the presence of ice, snow or water at said regions.
(a) scanning a surface of an aircraft with a first beam of radiant energy having a first wavelength substantially within a range that is preferentially reflected by said aircraft surface and absorbed by ice, snow or water; and (b) monitoring temperatures at said aircraft surface to detect regions experiencing temperature rises at relatively increased rates, thereby indicating the presence of ice, snow or water at said regions.
17. The method of claim 16 wherein step (b) comprises scanning said aircraft surface with a second beam of radiant energy generated by an infrared thermal camera to monitor temperatures at said aircraft surface, said second beam having a second wavelength that is smaller than said first wavelength.
18. The method of claim 17 wherein said first and second beams impinge upon and create first and second footprints upon said aircraft surface; said first footprint overlapping at least in part with said second footprint.
19. The method of claim 16 wherein said first wavelength is substantially within a range of approximately 8 microns to approximately 15 microns.
20. The method of claim 17 wherein said first wavelength is substantially within a range of approximately 8 microns to approximately 15 microns and said second wavelength is substantially within a range of approximately 0.8 microns to approximately 2.2 microns.
21. A system for de-icing an aircraft, comprising:
a laser beam generator capable of generating a beam of radiant energy;
means for directing said beam by an aircraft;
a first mirror disposed remotely from said aircraft, said first mirror movable between a first position in which said first mirror does not intercept any portion of said beam and a second position in which said first mirror intercepts a first portion of said beam and directs said first portion of said beam to said aircraft to create a first footprint on said aircraft; and a second mirror disposed remotely from said aircraft, said second mirror movable between a first position in which said second mirror does not intercept any portion of said beam and a second position in which said second mirror intercepts a second portion of said beam and directs said second portion of said beam to said aircraft to create a second footprint on said aircraft.
a laser beam generator capable of generating a beam of radiant energy;
means for directing said beam by an aircraft;
a first mirror disposed remotely from said aircraft, said first mirror movable between a first position in which said first mirror does not intercept any portion of said beam and a second position in which said first mirror intercepts a first portion of said beam and directs said first portion of said beam to said aircraft to create a first footprint on said aircraft; and a second mirror disposed remotely from said aircraft, said second mirror movable between a first position in which said second mirror does not intercept any portion of said beam and a second position in which said second mirror intercepts a second portion of said beam and directs said second portion of said beam to said aircraft to create a second footprint on said aircraft.
22. The system of claim 21 further comprising a boom suspended above said aircraft, said first and second mirrors being secured to said boom.
23. The system of claim 22 further comprising a first presence monitor disposed remotely from said aircraft for detecting the presence or absence of a fuselage of said aircraft under said boom, and a second presence monitor disposed remotely from said aircraft for detecting the presence or absence of a wing of said aircraft under said boom.
24. The system of claim 23 wherein said first and second mirrors are convex.
25. A method of de-icing an aircraft, comprising:
passing a beam of radiant energy by an aircraft;
moving a first minor from a first position in which said first mirror does not intercept any portion of said beam to a second position in which said first mirror intercepts a first portion of said beam and directs said first portion of said beam to said aircraft to create a first footprint on said aircraft; and moving a second mirror from a first position in which said second mirror does not intercept any portion of said beam to a second position in which said second minor intercepts a second portion of said beam and directs said second portion of said beam to said aircraft to create a second footprint on said aircraft.
passing a beam of radiant energy by an aircraft;
moving a first minor from a first position in which said first mirror does not intercept any portion of said beam to a second position in which said first mirror intercepts a first portion of said beam and directs said first portion of said beam to said aircraft to create a first footprint on said aircraft; and moving a second mirror from a first position in which said second mirror does not intercept any portion of said beam to a second position in which said second minor intercepts a second portion of said beam and directs said second portion of said beam to said aircraft to create a second footprint on said aircraft.
26. A method of de-icing an aircraft, comprising:
passing a beam of radiant energy by an aircraft;
reflecting a first portion of said beam from a first mirror to said aircraft to create a first footprint on a fuselage of said aircraft; and reflecting a second portion of said beam from a second mirror to said aircraft to create a second footprint on a wing of said aircraft.
passing a beam of radiant energy by an aircraft;
reflecting a first portion of said beam from a first mirror to said aircraft to create a first footprint on a fuselage of said aircraft; and reflecting a second portion of said beam from a second mirror to said aircraft to create a second footprint on a wing of said aircraft.
27. A method of de-icing an aircraft, comprising:
moving an aircraft under a radiant beam of energy;
when a fuselage of said aircraft is under said beam, reflecting a first portion of said beam from a first mirror to said aircraft to create a first footprint on said fuselage;
when said fuselage moves out from under said beam, moving said first mirror so that said first mirror does not reflect said beam;
when a wing of said aircraft is under said beam, reflecting a first portion of said beam from a second mirror to said aircraft to create a second footprint on said wing; and when said wing moves out from under said beam, moving said second mirror so that said second minor does not reflect said beam.
moving an aircraft under a radiant beam of energy;
when a fuselage of said aircraft is under said beam, reflecting a first portion of said beam from a first mirror to said aircraft to create a first footprint on said fuselage;
when said fuselage moves out from under said beam, moving said first mirror so that said first mirror does not reflect said beam;
when a wing of said aircraft is under said beam, reflecting a first portion of said beam from a second mirror to said aircraft to create a second footprint on said wing; and when said wing moves out from under said beam, moving said second mirror so that said second minor does not reflect said beam.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/US1998/001700 WO1999038774A1 (en) | 1996-09-05 | 1998-01-29 | Aircraft ice detection and de-icing using lasers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2318804A1 true CA2318804A1 (en) | 1999-08-05 |
Family
ID=22266287
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2318804 Abandoned CA2318804A1 (en) | 1998-01-29 | 1998-01-29 | Aircraft ice detection and de-icing using lasers |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2318804A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114162331A (en) * | 2022-02-14 | 2022-03-11 | 中国空气动力研究与发展中心低速空气动力研究所 | Icing detection device and icing detection method |
-
1998
- 1998-01-29 CA CA 2318804 patent/CA2318804A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114162331A (en) * | 2022-02-14 | 2022-03-11 | 中国空气动力研究与发展中心低速空气动力研究所 | Icing detection device and icing detection method |
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| FZDE | Discontinued |