Patent Publication Number: US-7901753-B2

Title: Synthetic runway surface system

Description:
PRIORITY CLAIM 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/519,572, filed Nov. 12, 2003, entitled “Synthetic Runway Surface System”, the entire contents of which are hereby incorporated by reference and relied upon. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to aviation and more particularly to airport runway surfaces. 
     Some smaller airfields are known to have natural grass surfaces. Those airfields experience each of the same problems growing and maintaining grass that exist in any type of natural grass setting. For example, grass in such fields can die for a myriad of reasons, leaving muddy ground that becomes rutted or heaved due to moisture. The ground can also dry to the point of creating foreign object debris (“FOD”) problems for aircraft. Such natural grass surfaces require watering and feeding, which is time consuming and expensive. Moreover, such natural surfaces provide food and nesting materials for birds and other animals, which are generally unwelcome around aircraft. 
     Besides the natural hazards to maintaining natural grass, the impact of aircraft exacerbates the degradation of the natural surface. Aircraft landing in wet, muddy and/or bare areas can further rut or heave the natural surface. Moreover, the force created by the aircraft landing gear can destroy the natural grass, especially in conditions where such grass is not healthy or in areas where the root structure of the natural grass is not particularly strong. Such areas can become rutted or heaved as well, making landing thereon difficult 
     Many airstrips that should have irrigation and drainage systems do not have such systems. Moreover, installing such systems incurs cost. Those airstrips over time can become uneven, rutted, heaved and otherwise unsuitable for landing. Eventually the airstrip reaches a level where landing is not safe. At that point, while it may be more economical in the short term to tear out the existing natural grass, regrade the landing strip and thereafter replant new seed or sod, such remedy only begins anew the cycle of natural grass degradation. The same areas which had previously shown problems growing or sustaining grass growth will likely once again experience such problems due the environment and aircraft impact, especially in situations where the airstrip is not properly watered and drained. 
     A need therefore exists for an economic, rugged and readily implemented system for replacing natural turf surfaces at airstrips and airfields. 
     SUMMARY OF THE INVENTION 
     The present invention includes a system, apparatus and method for installation of an artificial or synthetic turf or covering at airfields or airstrips in place of natural grass airstrips. The terms “artificial turf”, “artificial grass”, “synthetic turf” and “synthetic grass” are used herein interchangeably. Each of those terms refers to the commonly understood artificial turf having a backing with tufted or stitched synthetic grass blades extending therefrom. Those terms also expressly encompass other types of synthetic surfaces, such as synthetic matting, porous plastic and/or rubber materials, and plastic and/or rubber fabrics. 
     In one preferred embodiment, the surface is made to look like grass and provides an aesthetically pleasing airstrip when installed. The artificial turf can include runway border indicia, any known runway symbol or marking, advertising, logos, airport names, institutional names and any combination of same. The artificial turf runway system can be installed adjacent to any type of concrete, asphalt or other manmade structure, such as a roadway, paved runway, paved taxiway, parking lot, building, etc., or be surrounded completely by natural grass, shrubs, trees, etc. 
     The turf is installed securely using a number of apparatuses and methods discussed herein, such as via pinning devices, glue, masking, or other adhesive, which each attach the turf to a beam or header, which itself is securely installed to an anchor, such as a concrete anchor. Otherwise, the turf can be supported in its middle sections via those securing apparatuses or via the weight of infill applied to the turf. 
     The base beneath the turf is compacted, e.g., to greater than 90% compaction and in one preferred embodiment to greater than 95% compaction. The base in one embodiment is crushed rock of different size particles, which are capable of being compacted to a greater extent than, for example, rolled rock or rock particles of the same size. 
     The crushed stone and compacted base are well-suited for supporting aircraft taking off and landing from the synthetic strip of the present invention. As used herein, the term “aircraft” refers to gliders, any type of small airplane, such as single engine, multi-engine, turbo-prop, bi-plane or tri-plane. It is also possible that the depth of the compacted base could be deep enough to support the weight of a large jet airliner taking off and landing thereon. The term “aircraft” therefore includes larger jet airplanes, as well as other types of aircraft, such as helicopters, hot air balloons, etc. As used herein, “aircraft” also refers to any type or size or unmanned aerial vehicle (“UAV”). These aircraft examples are in no way meant to limit the scope of the invention or to serve as any sort of disavowal or disclaimer. 
     The turf system is graded so that water flows outwardly towards one or more edges of the system. The artificial turf does not require watering, seeding or separate drainage but instead requires only infrequent maintenance of the system to remove weeds and other sparse grass that may grow through the compacted base. The artificial turf runway therefore provides a stable, lasting, aesthetically pleasing and highly functional landing and takeoff area for aircraft. 
     The artificial turf surface also removes food and nesting materials for birds and other animals over a relatively large area, tending to dissuade those birds and animals from entering and loitering on the turf system. Further still, the artificial turf, which in one preferred embodiment is made of polypropylene, is fire and bum resistant, and therefore tends to mitigate a fire spreading from an aircraft accident occurring on the system. Still further, the sand or other infill layer tends to absorb noise and engine fuel, which lessens the noise disturbance from propeller engines, turbo-propeller engines or jet engines and reduces accident fires, respectively. Further still, the artificial turf system provides an all-weather structure that can be traversed in rainy or snowy conditions by safety and maintenance vehicles without obstruction. 
     It is therefore an advantage of the present invention to provide an artificial turf runway system and surface for small, medium and large aircraft. 
     It is another advantage of the present invention to reduce the possibility of bird strikes and accidents caused by other animals. 
     It is a further advantage of the present invention to minimize the fuel and fire damage from an aircraft accident. 
     Moreover, it is an advantage of the present invention to provide a synthetic turf system that reduces noise. 
     Further still, it is an advantage of the present invention to provide an artificial turf system that provides an all-weather, stable apparatus for emergency and safety vehicles. 
     Additional features and advantages of the present invention are described in, and will be apparent from, the following Detailed Description of the Invention and the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a sectioned perspective view of one embodiment of the artificial turf runway system of the present invention. 
         FIG. 2  is an elevation sectioned view taken along line II-II shown in  FIG. 1 . 
         FIG. 3  is an elevation sectioned view taken along line III-III shown in  FIG. 1 . 
         FIG. 4  is a sectioned elevation view taken along IV-IV shown in  FIG. 1 . 
         FIG. 5  is a sectioned elevation view taken along V-V shown in  FIG. 1 . 
         FIGS. 6 to 8  are schematic illustrations showing various embodiments for grading the synthetic turf systems of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides an artificial turf runway surface suitable for supporting takeoff, landing and taxiing of aircraft as that term has been described herein. The turf system cures many of the problems and pitfalls associated with natural grass systems, such as rutting, bare spots, unevenness, standing water as well as other problems associated with natural grass surfaces. The synthetic surface also removes nesting materials and food and thereby dissuades birds and other animals from landing and congregating thereon. 
     Referring now to the drawings and in particular to  FIG. 1 , one embodiment of the synthetic turf system of the present invention is illustrated by system  10 . System  10  includes an area of synthetic turf  12 . Various preferred embodiments for the synthetic turf used in the present invention are described in U.S. Pat. No. 6,620,482, entitled “Safety System for Airports and Airfields”, assigned to the eventual assignee of the present invention, the entire contents of which are expressly incorporated herein by reference. That patent describes an artificial turf having polypropylene fibers in one embodiment tufted or stitched to a backing, which in one embodiment includes a double woven polypropylene layer and a second flexible backing, which is polyurethane. Polypropylene fibers are one preferred type of fiber in this application, which is not a sports field requiring the softer polyurethane fibers. Polypropylene is better-suited for withstanding the riggers of aircraft landings. It should be appreciated however that any suitable turf can be used as the artificial surface  12 . 
     Further, while artificial turf is used in one preferred embodiment, the present invention is expressly not limited to artificial grass, but can instead use any type of synthetic matting, which for example can be porous or perforated. The “turf” specified by element number  12  also includes synthetic coverings that are made of a combination of plastic and rubber, which are bound together in a granulated fashion, and which allow water and moisture to percolate through same. 
     Artificial turf  12  in one embodiment is green but can have any other color or be of a multitude of colors, any one or more of which can be fluorescent. Turf  12  includes and defines multiple different types of painted-on, sown-in or integral markings, such as runway borders  14 , which divide the entire area of turf  12  into multiple runways. The turf markings also include any known type of airport or runway marking, such as the chevron markings  16  shown in  FIG. 1 . The runway markings  16  also include the runway numbers which are displayed in any suitable fashion and quantity on artificial turf  12 . The runway markings are not limited to those shown in  FIG. 1  and indeed can include each of the markings shown in U.S. Pat. No. 6,794,007, entitled “Artificial Turf Airport Marking Safety System”, assigned to the assignee of the present invention, the entire contents of which are incorporated herein by reference. 
     Artificial turf  12  also displays other types of markings, such as advertising  18 , logos  20 , airport names  22 , institution names  24  (such as a university name, a company name, a military organization, etc.) and any combination thereof. The present invention expressly contemplates subsidizing the cost of the artificial turf system  10  to the end user by displaying advertising  18  and obtaining revenue from one or more advertisers. Such advertising and revenue can be used to lower the cost of the system  10  to the end user. Advertising can also yield licensing and/or lease fees, which can be paid to either the system installer or to the end user. Thus, system  10  can provide each of the operational and functional advantages described herein as well as provide an ongoing revenue stream to the system supplier and/or the end user. 
     As illustrated in  FIG. 1 , artificial turf  12  is adaptable to be installed adjacent to a number of different types of materials and surfaces, such as a paved concrete or asphalt or otherwise non-natural surfaces  26  as well as a natural surface  28 , which can include any type of grass, shrubs, trees, etc., which may or may not be common to the area in which the system  10  is installed. 
     System  10  is adaptable to provide virtually any size artificial runway surface, which can be used for one or more aircraft runways. One example for the width and length of turf  12  is a width “w” of 500 feet and a length “l” of 4,500 feet. It should be appreciated however that such numbers are only an example, and the area of turf  12  can be larger or smaller as desired. The area of turf  12  as illustrated shows four separate runways, which can be evenly spaced apart to allow multiple aircraft  30  to land, taxi and/or park on artificial turf surface  12 . System  10  is also suitable to be used as a taxiway that may or may not be implemented in combination with a runway. 
     Referring now to  FIG. 2 , a sectioned view taken along line II-II of  FIG. 1  is illustrated. The section shows one embodiment for installing turf  12  alongside a concrete, asphalt or otherwise manmade surface  26 . System  10  includes a weed barrier  32 , which is applied to a compacted and graded surface of a natural material or soil or sand  34 . Weed barrier  32  provides one line of defense against the propagation of vegetation, grubs or other insects through the remainder of system  10 , including through turf  12 . Weed barrier  32  in one embodiment is a plastic or other type of geo-textile fabric that retards upward weed growth and allows a steady and unimpeded stream of water to flow in the opposite direction, namely into soil or sand  34 . 
     A compacted rock or crushed rock base  36  is applied on top of weed barrier  32 . Each of the embodiments for the base described in U.S. Pat. No. 6,620,482 is suitable for use in the present invention. The depth of the base  36  in one embodiment is one to twenty inches or deeper. For lighter aircraft, such as gliders, the thickness of the compacted base  36  is in one embodiment about two to three inches and consists of quarter inch minus road base, which is crushed rock having a diameter of about one quarter inch down to rock that has virtually a zero diameter, e.g., sand or dust. The different sized particles enable base  36  to be compressed to a more compacted state than if rolled rock or rock of approximately the same size diameter particulate is used. Such rolled and similarly sized particles create interstices regardless of how much pressure is applied to compact those materials. The quarter inch minus base  36  on the other hand can be compacted to greater than or equal to 90% (less than or equal to 10% air), in one embodiment greater than or equal to 95%, and it may even approach or surpass a 99% level of compaction. 
     A second weed barrier  32  or sheeting membrane  38  is applied in one embodiment on top of compacted base  36 . Upper geo-textile  32  or other suitable fabrics, like lower layer  32 , enable water to permeate through same but does not enable weeds, plant life and other vegetation or insects from growing or moving from base  36  and out through turf  12 . Alternatively, a substantially water impermeable membrane  38 , such as a plastic sheet, is applied on top of base  36  instead of the second weed barrier  32 . 
     The surface of soil or sand  34  and each of the layers applied thereon are graded to a desired slope, such as a 2% slope, which enables water to drain to a desirable area. In  FIG. 2 , it is likely that the slope will be graded so that water flows away from manmade structure  26 . When moisture enters system  10 , it permeates through the infill  40  of turf  12 , which in one embodiment is compacted sand. The water then flows either through weed barrier  32  to base  36  or flows on top of membrane  38 . In either case, the water is generally and gradually moved out of system  10  by flowing along the grade of compacted soil or sand  34 . That is, even in the flow-through system employing weed barrier  32 , the compaction of base  36  is such that the water tends to flow sideways rather than downwardly through the base  36  (although some downward flow does occur). Indeed, sand infill  40  soaks up much of the water and much of the water therefore drains along the top of a matting  42 , which holds the turf fibers  44  in place. 
     Water that does flow through matting  42  will tend to flow along the top of impermeable membrane  38  or substantially along the top of the compacted base  36 . Some of the water eventually flows through compacted base  36 . Water that reaches weed barrier  32  is allowed to flow eventually into compacted surface  34 . It should be appreciated however that system  10  is configured to mainly move water along the graded surfaces to a desired location within or on the exterior of system  10 , which includes suitable drainage that carries water away from the runway, taxiway, etc. System  10  does not require elaborate drainage, which is advantageous from a cost and feasibility standpoint. 
     For lighter aircraft, such as gliders and UAV&#39;s, base  36  can be less substantial. It is expressly contemplated for example to create a quick but functional landing and take-off area for a UAV by simply clearing an area of debris and rolling out a length of turf  12  on the cleared area. The area could be a dirt area or a sand or dessert area. Grass could be removed from the dirt or left beneath turf  12 . In any case, the cleared area may or may not be compacted depending on the size of the aircraft and immediacy of the need for a functional airstrip. Different strips of turf  12  can be quickly stitched or glued together to provide a landing strip with a desired length and width. 
     Turf  12  in one embodiment has a pile height of approximately one-half inch to six inches. In one preferred embodiment, the pile height is about two inches. The sand infill  40  is compacted to about 1⅜ inches to about 1¾ inch in one embodiment. While pure sand is preferred in one embodiment, it should be appreciated that some percentage or all of the infill  40  can be comprised of other materials, such as granulated rubber and/or cryogenically ground rubber particles. It may be desired that a partial or full rubber infill be used in some instances to provide a softer landing. To that end, some or all of the base  36 , depending on the size and weight of the intended aircraft, can be of a softer and more compressible material such as sand and/or rubber. 
     The spacing of the fibers  44  is provided in straight or curves rows, which can be spaced apart from about ¼ inch to about 2½ inches. In one preferred embodiment, the fibers  44  extend past the infill layer  40  a distance of about ⅛ inch to two or more inches. The extension of the fibers  44  over the infill layer  40  helps to prevent sand or other infill  40  particles from flying up into a jet, propeller or turbo-prop engine. Further, the extended pile height prevents sand or other infill type from being dragged up and from being blown or gusted up via ambient wind, becoming a FOD. 
     In an alternative embodiment, infill  40  is not employed. Such application could allow a relatively inexpensive turf  12  having a short pile height, e.g., one-half inch to be employed. Removing the infill may be desirable if the infill is seen as potentially providing a FOD. It is believed however that the sand or other infill compacts further over time, reducing a likelihood of the infill being kicked-up as an aircraft rolls over turf  12  and system  10 . In a further alternative embodiment, infill  40  may include a stabilizer, such as polymer fibers placed within the sand or other infill particles. 
     Referring now to  FIG. 3 , a sectioned elevation view taken along line III-III of  FIG. 1  is illustrated.  FIG. 3  illustrates one embodiment for creating a seam between turf  12  and natural grass  28 . Each of the embodiments and alternatives discussed above for turf  12 , soil or sand  34 , weed barrier  32 , compacted base  36  and membrane  38  are applicable to the description in connection with  FIG. 3 . In  FIG. 3 , a section of the turf  48  is folded between soil or sand  34  located beneath system  10  and soil or sand  34  beneath natural grass  28 . In one embodiment, turf section  48 , which can be from about four inches to about 3 feet in length is rolled out past base  36 , etc. A trench is dug next to system  10 . Turf section  48  is folded into the trench and soil or sand  34  is backfilled and compressed to hold section  48  in place. Sod or grass seed is then planted to grow natural grass  28  adjacent to section  48 , which creates an esthetically pleasing and secure seam between the end of system  10  and the beginning of natural grass  28 . 
     Referring now to  FIGS. 4 and 5 , sectioned elevation views taken along lines IV-IV and V-V, respectfully, of  FIG. 1  show another embodiment for securing an edge of the turf  12  to an edge of the natural grass  28 . Each of the element numbers shown here and common to the figures shown above incorporate all of the description and alternatives described above for such numbers. The instant embodiment is shown in two directions in  FIGS. 4 and 5 . 
     The attachment system includes a plurality of anchors  50 , which are imbedded into soil or sand  34  a suitable distance to provide a secure mounting structure for the edge of turf  12  of system  10 . Anchors  50  in one embodiment are concrete anchors, such as eight inch diameter anchors. Alternative anchors  50  are square or rectangular and are made of any suitable material, such as composite plastic, asphalt, metal, or wood. Concrete is desirable in one embodiment because a hole or trench can be dug, wherein the concrete is poured to a desired depth, width and shape. 
     Anchors  50  can be poured to a depth of about six inches to about six feet or deeper as needed. In one embodiment, the anchors  50  are poured to about two feet. Anchors  50 , as shown in  FIG. 4 , are spaced apart a distance “x”, which is suitable to support a plurality of structural headers  52 . Headers  52  in one embodiment are the same headers  52  used in  FIG. 2  to secure turf  12  to manmade structure  26 . In one embodiment, headers  52  are 2×4 inch or 1×6 inch recycled composite headers. One suitable supplier for headers  52  is Trex™ composite structure produced by Trex™ Company LLC, located at Trex.Com. 
     Anchors  50  have embedded studs  54  that extend from an end of the anchors.  FIGS. 4 and 5  illustrate that anchor  50  supports the ends of two studs  52 .  FIG. 5  illustrates that each header  52  defines two holes or apertures that receive the studs  54  extending from anchors  50 . Anchors  50  are spaced apart a distance “x”, which is in one embodiment from about eight feet to about twenty feet. Distance “x” may be set by the longest length available for header  52 . For example, a Trex™ header described above comes in lengths of 16 feet, so that distance “x” is either 16 feet or slightly bigger to allow a small gap to exist between headers  52  for expansion and contraction. Studs  54  extending from anchors  50  can be threaded so that the headers  52  are held against anchors  50  via nuts (not illustrated) that fasten to studs  54 . 
     The concrete anchors  50  as well as the side of manmade structure  26  in one embodiment are saw cut to provide a flush and even surface for abutting against headers  52 . Anchors  50  are saw cut (around studs  54 ) to create level supports as seen in  FIG. 4 , so that headers  52  are substantially horizontal or are angled at the desired grade of soil  44 .  FIG. 2  shows an alternative embodiment for attaching the stud  52  to manmade structure  26 . In  FIG. 2 , a ramset  56  is used in bolt or pin header  52  against the saw cut and flush edge of manmade structure  26 . Further, header  52  can be glued or mastiqued to either one or both the manmade structure  26 , which in one embodiment is a long concrete or asphalt structure, or to the top surface of anchors  50 . 
     Glue or mastique can be used in a number of places in system  10  to help secure turf  12  to, for example, upper weed barrier  32  or membrane  38 . Further, mastique or glue can be applied between barrier  32 /member  38  and the backing of turf  12  or between barrier  32 /member  38  and header  52 . Other devices are also used to secure of turf  12  to base  36  and soil or sand  34 . For example, U-shaped staples  58  or T-shaped pinning devices  60  can be hammered through turf  12  into base  36  and potentially through base  36  into soil or sand  34 . Either the staples  58  or the pinning devices  60  can include ribbed apparatuses  62  that help prevent pinning devices  60  or staples  58  from dislodging from the materials to which they are attached. 
     Referring now to  FIGS. 6 to 8 , various embodiments for the graded system  10  are shown schematically. System  10  is adaptable to fit virtually any type of environment and be placed in any type of geographical location. The goal as stated above is to move water and moisture away from system  10  to the outlying natural grass areas  28  shown in  FIG. 1 . The topography and location of manmade structures, such as structure  26 , dictate generally how the system  10  should be graded. 
       FIGS. 6 and 8  show three schematic examples, which include both the width direction “w” and the length direction “l” shown in  FIG. 1 . That is, the grade can either be lengthwise or widthwise according to one of the profiles.  FIG. 6  illustrates a constant grade from one end of the system  10  to the other. It is also possible that the grade can be made constant in length and width directions as shown in  FIG. 6 .  FIG. 7  illustrates a grade that has its highest point located approximately in the middle of width “w” and/or length “l”. Again, such a grade can be made in one direction or in both length and width directions.  FIG. 8  illustrates another example where the highest point in system  10  is located off-center in either the width “w” and/or length “l” directions. It should be appreciated that the grade does not have to be perpendicular to any particular dimension “w” or “l”. The important feature is that the grade eventually moves water off of system  10  to a suitable location where an external (or internal if desired) drainage system can collect the water and drain it properly. 
     The system is particularly well-suited for gliders and the present invention expressly contemplates a method for allowing gliders to take off and land on a synthetic turf runway. 
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.