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APPENDIX N

MEMBRANES AND MATS

Mats and membranes are used to improve existing assault-type airfields or to construct new airfield surfaces in all areas of the world where field commanders require expedient surfacing or support of air mobile operations.
Initial selection of the airfield site should be made by utilization of available data, such as topographic maps, aerial photographs, and geological and climatological data. Final selection is based on the in-place or the average in-place soil bearing strength and its capacity to support anticipated aircraft traffic. Chapter 10 discusses the number of traffic cycles versus bearing strength for mats and membranes.

MEMBRANES

TYPES

Membranes consist mainly of coated fabrics intended for use as airfield surfacing to dust-proof and waterproof soil subgrades. Currently, there are two types of membranes that meet acceptable standards--heavy-duty and medium-duty.

The WX-18 heavy-duty membrane is a neoprene-coated, four-ply, nylon fabric that is woven from continuous filament nylon yarns. The membrane is 5/64 inch thick, and a runway section is 66 feet wide by 53 feet long and weighs about 0.5 pound per square foot. It was developed as a result of the T-17 medium-duty membrane's failure to support C-130 braking action. The medium-duty membrane is made of the same material as the heavy-duty membrane except that it is only a two-ply fabric and weighs approximately 0.33 pound per square foot.

Heavy-Duty Membrane

The WX-18 heavy-duty membrane is capable of withstanding the braking action of C-130 aircraft. The WX-18 can be used in two configurations to support C-130 operations, either all heavy-duty membrane for the entire airfield or with T-17 medium-duty membrane. In this configuration, the initial 500 feet at each end of the runway will be heavy-duty membrane while the remainder will be T-17 membrane.

To provide adequate braking during inclement weather, a nonskid compound has been applied to the middle 32 feet of the heavy-duty membrane that will be used for the traffic areas of the airfield. The nonskid compound is a polka-dot pattern; white stripes are painted on the membrane surface to outline the nonskid treated area, provide alignment of the surfacing during placement, and serve as runway marking for aircraft operations. Table N-1, shows a detailed listing of the components contained in each heavy-duty membrane set.

Medium-Duty Membrane

The T-17 is a medium-duty membrane that is capable of withstanding operations of helicopters and light, fixed-wing aircraft. When used in conjunction with the heavy-duty membrane, the T-17 membrane can be used to support C-130 operations. T-17 membrane is manufactured from two-ply, 5.1-ounce, neoprene-coated, nylon material and weighs 3 pounds per square yard. For adequate skid resistance, a nonskid paint must be applied to the membrane after it is installed.

Packaging

Complete sets of heavy-duty membrane can be ordered using SC 5680-97-CL-E05. Set components and matting sizes differ according to airfield requirements. The T-17 membrane will be available until current stocks are depleted after which only heavy-duty will be available. Membrane sections will be in crates weighing several thousand pounds, and membrane splices will come in rolls similar to tar-paper rolls. A mechanical lifting device should be used to move the crates. Table N-2 shows membrane panel sizes.

During packing of the membrane at the factory, the sections are folded when placed into crates. Often the membrane will develop wrinkles when folded for a long period of time because of the difference in the residual tension in the nylon. These wrinkles will not affect the usefulness of the membrane to any great degree. Stretching the section will normally remove or reduce the wrinkles.

MEMBRANE ACCESSORIES

Accessories required for constructing, emplacing, securing, maintaining, and repairing the WX-18 heavy-duty and the T-17 membrane surfacing are similar and are as follows:

Anchors

Disc-type, steel anchors are used to expedite placement of the membrane surfacing by securing the surfacing in place. Each anchor consists of a 3/4-inch-diameter steel reinforcing rod approximately 12 inches long that has been arc-welded to a 1/8-inch-thick, shaped steel plate that is 8 inches in diameter. The anchor weighs approximately 3 pounds. These come with the membrane kits or may be locally fabricated.

Adhesive

Adhesive is used to form membrane construction joints and to repair membrane in the field. The adhesive consists of a synthetic rubber resin dispersed in solvent that evaporates rapidly after exposure to air, thus developing the bond strength of the resin. The adhesive used during dry weather is supplied in 5-gallon, tight-head pails with pouring spouts. Each 5-gallon pail of adhesive weighs approximately 40 pounds. Adhesive used for wet weather repairs and replacement of surfacing is furnished in 1-gallon pails with accelerator. This adhesive must be mixed in the field (basic cement and accelerator) before use. It has a short pot life and no more of the adhesive should be mixed than that planned for use during a period of two hours. The adhesive and accelerator are packaged in cases. Each case contains four 1-gallon pails of adhesive and four 1-pint cans of accelerator.

Nonskid Compound

Nonskid compound consisting of catalyzed epoxy binder with abrasive particles applied in compartmented 5 1/4-gallon pails provides an adequate braking surface during inclement weather. Each pail of compound weighs approximately 65 pounds.

Paint Rollers, Handles, and Covers

Paint rollers that are 9 inches wide with 48-inch-long wooden handles are used to apply adhesive and nonskid compound. Lamb's wool or synthetic fabric disposable roller covers are provided so that after use, the covers can be removed from the rollers and new covers placed on the rollers before reuse.

Joint Sealer, Caulking Gun, and Putty Knife (Heavy-Duty Membrane Only)

A one-part sealant, which cures upon exposure to air and/or moisture, is supplied in a cartridge for application with a half-barrel-type caulking gun. The sealer is used to seal the edges of the 36-inch-wide reinforcing strip used on adhesive construction joints and for rapid repairs to seams and joints during all weather conditions. To remove excess sealant from areas, a 1 1/4-inch-wide putty knife is used to strike and draw the sealant from the surfacing.

Roll Of Membrane (3 X 66 Feet)

One roll of membrane is supplied per set. The roll of membrane is used to reinforce adhesive construction joints and to provide a single-layer cushion of membrane over the heads of disk-type anchors used in each adhesive construction joint.

MEMBRANE PLACEMENT

The placement of both the T-17 and the WX 18 membrane is similar in nature. The differences occur in the design of the membrane. The minimum size unit required for efficient placement is a platoon and six equipment operators (see Table N-3). Troops with any military occupational specialty (MOS) can place and maintain membrane with minimal instruction and on-the-job training.

After a site with adequate average bearing strength for wheel load and anticipated aircraft traffic has been chosen (Chapter 11), the area should be cleared and grubbed to remove all vegetation. The area should be graded to obtain a crown anti minimum grade changes in accordance with the design aircraft. After the site is prepared. 2-foot-deep, L-shaped anchor ditches should be constructed at one end and on both sides of the area to be surfaced. The remaining end anchor ditch should not be constructed until placement of all membrane sections are complete. This will permit access to the area by vehicles and will also permit an exact determination of the location of the final end anchor ditch. A full 3 feet of membrane will be placed in the ditches before backfilling and compaction (Figure N-1). The side ditches should be parallel to the established centerline.

All soil removed from the anchor ditches should be windrowed outside the placement area. and the soil can be used for fill after the membrane has been placed in the ditch. Motor graders are best used to construct anchor ditches, but other pieces of equipment can also perform this function.

Vehicles are required for transporting the wooden crates of membrane to the site and for use during placement. The 5-ton dump truck or any 6x6 cargo truck of at least 2 1/2-ton capacity is suitable for this purpose. After crates have been stockpiled on the placement site, the tops and sides of the crates should be removed just before lifting the skid platform with the banded surfacing on placement vehicles. Medium wreckers can be used to lift the platform.

WX-18 Heavy-Duty Membrane Placement

Placement of the first section of membrane will be initiated by removing approximately 3 feet of the folded surfacing from the skid and placing it in the end anchor ditch that was constructed transversely across the runway. The words top and bottom stenciled on the uppermost surface of the accordion-folded section of surfacing will be disregarded during this stage of placement. Next, the placing vehicle will move slowly along the centerline of the airfield while the membrane surfacing is unfolded from the rear of the vehicle and placed on the ground. Care will be taken by the driver of the vehicle to maintain alignment of the membrane with the centerline of the area. The placing crew will also exercise care to ensure one edge of the surfacing, as it is being placed on the ground, is aligned with the centerline; the surfacing is placed flat on the ground, and all slack is removed from the surfacing.

When the membrane is first placed on the ground, it will consist of an accordion-folded surfacing that is approximately 48 inches wide and 53 feet long. After the surfacing is unloaded from the vehicle, troops will be stationed at equal intervals along the 53-foot length of the surfacing and will unfold the surfacing to one side of the area and place the edge of the surfacing in a side anchor ditch. Then, the remaining half of the surfacing will be unfolded to the other side of the area and placed in the side anchor ditch. The section of membrane will be unfolded so that the side marked top will face upward and the side marked bottom will face downward to contact the soil subgrade. If the section is unfolded incorrectly, the smooth side of the section will face upward, and it will be necessary to turn the section over so that the nonskid treated area faces upward. The section must be repositioned so that alignment of edge and centerline striping is maintained. Every effort will be made to align, position, and remove slack from the surfacing before steel anchors are placed in the surfacing and the ditches backfilled. The anchors will be driven through the factory, single-lap construction joints where the membrane thickness is doubled.

Once the surfacing is positioned on the area and most of the slack removed, steel anchors will be driven through the surfacing in the end anchor ditch approximately 6 inches from the edge of the surfacing (Figure N-1). Eight steel anchors will be used to secure the membrane surfacing in the end anchor ditch. Anchors will be driven in the three alternative factory, single-lap construction joints located immediately on each side of the centerline of the section of membrane and in each corner of the section that is placed in the end anchor ditch. The end anchor ditch will then be backfilled and compacted. Additional slack will be removed from the surfacing by troops pulling on the free end of the surfacing that has not been placed in the anchor ditch. As slack is removed, steel anchors will be driven through alternative single-lap adhesive construction joints on approximately 9-foot centers and 1 foot from the outer edge of the free end of the surfacing. The protective paper on this end of the membrane will not be completely removed during the operation. The top portion will be peeled back to allow the driving of the anchors, and then the paper will be put back on the top portion to protect it against dirt and debris before application of the construction joint. White lines, 1/8 inch wide and located 1 foot from each end of the section of membrane, have been painted on the section to provide alignment for driving the anchors. Steel anchors will then be driven through the surfacing placed in the side anchor ditches on 17-foot centers and approximately 6 inches from the outer edge of the surfacing (Figure N-2).

After anchors are driven in the side ditches, backfill will be placed in the ditches in 6-inch lifts and compacted. Loaded 5-ton dumps are suitable for all compaction. If motorized graders are used to compact the lifts, care must be taken to prevent the grader blade from snagging or cutting the membrane. The side ditches will not be backfilled completely to the free end of the section of surfacing because room will be needed to construct the adhesive construction joint. Backfilling of the side ditches will stop approximately 6 feet from the free end of the surfacing. While the side ditches are being backfilled on the first section of surfacing, the next section of surfacing will be unloaded on the area in the manner described previously for the first section of surfacing. Before the second section of surfacing is unloaded on the ground, the vehicle will be positioned and a sufficient amount of surfacing unfolded from the vehicle so that the second section overlaps the first section by approximately 24 inches. The membrane should be unfolded and placed over the area, and the sides should be placed in the side anchor ditches. The protective paper will be removed from the top of the first panel and the bottom of the second panel. The paper from the first panel will be folded out onto the ground and remain in place. This helps keep dirt off the membrane during the application of adhesive when fabricating the construction joint.

After the paper on both sections has been folded back, the overlapping end of the second section will be positioned over the end of the first section so the 1/8-inch-wide white line on the second section will be placed directly over the white line on the end of the first section. The second section will be positioned so the 12-inch-wide white centerline will be aligned with the centerline of the first section. Before any effort is made to remove slack from the second section of surfacing, steel anchors will be driven through the overlapping ends of both membrane sections and into the subgrade to a depth of approximately 6 inches. These anchors will be located between the anchors driven previously through the first section of membrane and will be driven through the overlapping section and positioned on the 1/8-inch-wide white line located 1 foot from the edge of the surfacing (Figure N-2). After the anchors are driven through the surfacing, initial slack will be removed from the second section of surfacing, and then anchors will be driven through the factory constructed, single-lap joints located in the free end of the membrane the same way it was done for the first panel. Anchors will then be driven through the membrane placed in the side anchor ditches on 17-foot centers as they were for the first panel. After the second panel has been anchored, the construction of the adhesive construction point between the first and second panels can be completed. To construct the construction joint, the 2-footwide overlapping end of the second section will be raised with 48-inch-long paint-roller handles so adhesive can be poured onto the underlying surfacing. The joint will be constructed in increments approximately every 8 feet along the entire membrane width. Uniform spreading of the adhesive onto the surfacing is accomplished with the long-handled rollers so that the adhesive covers an area that extends approximately 1 foot beyond the anchor heads. Ample time (usually two to five minutes) will be allowed for the adhesive to become tacky to the touch; however, more or less time may be required, depending on weather conditions. When the adhesive becomes tacky, the overlapping ends of the sections will be placed in contact and the anchors driven flush with the surfacing. Care should be exercised to avoid overdriving the anchors. When a snug fit is obtained between the surfacing and anchor head, driving should be stopped.

To reinforce the adhesive construction joint, a 36-inch-wide strip of membrane will be placed over the joint and bonded to the surfacing with adhesive. In placing the strip over the joint, the roll of membrane strip will be aligned so that it straddles the 1/8-inch-wide white line located on the overlapping section. Care will be exercised when placing the reinforcing strip to ensure that the edges of the strip do not extend onto the nonskid-treated area of the surfacing. Adhesive will be spread at intervals of 10 to 12 feet along the joint in a width of approximately 38 inches. After the adhesive becomes tacky, the roll of membrane will be rolled across the adhesive-covered area. Care will be exercised to maintain alignment of the strip and to remove all slack and wrinkles from the membrane. This procedure of applying adhesive and then rolling the membrane across the adhesive-covered area will be continued for the full length of the joint. After the strip has been allowed to set for approximately 15 minutes, the strip may be rolled with a light rubber-tired vehicle. Rolling of the reinforcing strip with a light wheeled vehicle is optional. If a visual inspection of the strip reveals that air pockets exist beneath the strip, then the joint should be rolled to remove these pockets. If no such pockets are found, then rolling the joint is not required. The edges of the construction joint will be sealed with sealant after each reinforcing strip has been allowed to set for approximately 15 minutes and/or has been rolled with a light wheeled vehicle. Sealing of the strips may be delayed until near the end of the working day, but because of the cure time required for the sealant, no traffic of any kind will be allowed on the sealed strips for a minimum period of 48 hours. Any foreign material that may have accumulated adjacent to the edges of the reinforcing strips will be removed before the sealant is applied to the surfacing. A 1/4-inch-wide continuous bead of sealant will be applied to each edge of the reinforcing strip with a caulking gun. The bead of sealant will be beveled with a putty knife in order for the sealant to be flush with the upper surface of the reinforcing strip.

The placement of additional sections of membrane will be accomplished in the same manner as described above. When the last membrane section is placed, the end anchor ditch will be cut in the required location for the membrane placement. The membrane will then be anchored after which the trench will be backfilled and compacted.

T-17 Membrane Placement

The placement of T-17 membrane is very similar to heavy-duty membrane with a few exceptions. T-17 is used with heavy-duty membrane for C-130 capable runways or by itself for fixed-wing rotary aircraft or helipads. When used with heavy-duty membrane, the first 500 feet of both ends of the runway will be heavy-duty membrane and the rest of the airfield can be T-17. Placement of the first section of membrane will be initiated by removing approximately 3 feet of the folded surfacing from the crate and placing it in the anchor ditch that was constructed transversely across the runway. The vehicle should then be driven slowly along the centerline of the runway while the membrane is unfolded from the rear of the vehicle and placed on the ground. Care should be taken to ensure the alignment of the membrane with the centerline of the runway. When the membrane is placed on the ground, it will consist of an accordion-folded surfacing approximately 50 to 60 inches wide and 100 feet long. After the surfacing has been unloaded from the vehicle, troops should be stationed at equal intervals along the length of the surfacing.

Half the surfacing should be unfolded to one side and placed in a side anchor ditch. The remaining half of the surfacing should then be unfolded and placed in the other side anchor ditch. There is no top or bottom to this membrane.

After the membrane is aligned and positioned, the initial slack is removed from the surfacing. The end anchor ditch is then backfilled and compacted, and the free end of the membrane is pulled over the area to be surfaced. As slack is removed from the surfacing, the side ditches should be backfilled and compacted to within 6 feet of the free end of the membrane. The side ditches should not be backfilled to the free end of the membrane because space will be needed to join the end of the next section. There is no marking on the T-17 membrane to direct where the placement of the anchors should be. When anchors are used, the locations for the anchors in the end and side ditches should be 6 inches from the outer edge of the membrane on 17-foot centers. On the free end of the membrane, the anchors will be driven on 9-foot centers and 1 foot from the outer edge. A motor grader can be used for compaction but care must be taken to prevent the grader from ripping the membrane. Backfilling of the side ditches should stop approximately 6 feet from the free end of the membrane to allow for construction of the construction joint.

While the side ditches are being backfilled, the second section of membrane should be unloaded onto the area in the same manner as the first section. The placement vehicle should be positioned so that the second section overlaps the first section by approximately 24 inches. The membrane should then be unfolded and placed over the area. The sides should be placed in the side ditches. Anchors should be driven through the overlapping ends of both membranes, between the previously driven anchors, to a depth of 6 inches. Once slack is removed, side anchors and end anchors on the free end of the membrane can be loaded and the construction joint constructed.

To construct the joint, the 2-foot-wide overlapping end of the second section will be raised with 48-inch-long paint-roller handles so adhesive can be poured onto the underlying surfacing. The joint will be constructed in increments approximately 9 feet long. Uniform spreading of the adhesive onto the surfacing will be accomplished with the long-handled rollers. Ample time (usually two to five minutes) will be allowed for the adhesive to become tacky to the touch: however, more or less time may be required, depending on weather conditions. When the adhesive becomes tacky, the overlapping ends of the sections will be placed in contact and the anchors driven flush with the surfacing. Care should be exercised to avoid overdriving the anchors if they are used. When a snug fit is obtained between the surfacing and anchor head, driving should be stopped. To reinforce the adhesive construction joint, a 36-inch-wide strip of membrane will be placed over the joint and bonded to the surfacing with adhesive. In placing the strip over the joint, the roll of membrane should be aligned so that it is centrally located along the edge of the overlapping section.

Adhesive will be spread at intervals of 10 to 12 feet along the joint in a width of approximately 38 inches. After the adhesive becomes tacky, the roll of membrane will be rolled across the adhesive-covered area. Care will be exercised to maintain alignment of the strip and to remove all slack and wrinkles. This procedure of applying adhesive and then rolling the membrane across the adhesive-covered area will be continued for the full length of the joint. After the strip has been allowed to set for approximately 15 minutes, the strip may be rolled with a rubber-tired vehicle. If a visual inspection of the strip reveals that air pockets exist beneath the strip, then the joint should be rolled to remove these pockets. If no such pockets are found, then rolling the joint is not required.

The edges of the reinforcing strip may be sealed with sealant in the same manner as the heavy-duty membrane, but it is not required. Sealant is not part of the T-17 set and must be ordered separately. After sealing the reinforcing strip, no traffic of any kind will be allowed on the sealed strip for a minimum of 48 hours because of the sealant cure time.

Placement of additional sections of membrane will be accomplished in the same manner as above. When the last section is placed, the end anchor ditch will be cut in the required location for the membrane placement. Then, the membrane will be anchored, backfilled, and compacted.

The application of the nonskid compound paint can be accomplished in the same manner discussed in repair of the nonskid compound later in this appendix.

MAINTENANCE, REPAIR, AND REPLACEMENT OF MEMBRANE SURFACING

Maintenance and Repair of Membrane

Service tests have indicated that repair and maintenance of membrane surfacing for operation of current US Army aircraft will be minor. However, more repairs and maintenance can be expected for traffic with maximum-loaded C-130 aircraft. Most, if not all, repairs will be needed in the first 300 feet of surfacing at each end of the runway. The size of the repair and maintenance crew will be determined by the size of the area surface. For airfield complexes, a crew of six men is normally adequate. The surfacing should be inspected thoroughly just before initiation of sustained aircraft operations to determine the condition of the surfacing and to perform essential maintenance. When aircraft operations begin, the surfacing must be inspected by the maintenance crew with binoculars to permit uninterrupted use of the surfacing. If a failure occurs in the surfacing during aircraft operations, the failure should be repaired as soon as aircraft operations permit. Ballooning of the surfacing that has been punctured or torn can occur when air is forced through these openings in the surfacing by the prop wash of aircraft engines causing the surfacing to become airborne. Service tests on the surfacing have shown that small surface failures may be trafficked by aircraft for a limited period without severe damage or ballooning of the surfacing; nevertheless, the best practice is to repair all failed areas as soon as possible. Less time and effort will be required to repair a small area immediately after failure than to risk the small area developing into a major repair problem.

Failures in the traffic area will be repaired by slitting the failed surfacing in the form of a cross and folding the four flaps back. An area approximately 2 feet wide surrounding the failure on all sides will be cleaned to remove dirt or dust that may have accumulated on the underneath side of the surfacing. After the surfacing has been cleaned, the area will be allowed to dry before the adhesive is applied. Adequate membrane surfacing will then be cut and placed beneath the membrane surfacing so that it extends beyond the failed area of surfacing approximately 2 feet on all sides. Adhesive will then be applied to the top of the membrane patch being used for the repair and to the bottom of the surfacing being repaired. After the adhesive becomes tacky (2 to 5 minutes), the flaps that were folded back previously will be placed in their original positions, and the adhesive allowed to set for approximately 15 minutes before rolling the patched areas with a wheeled vehicle. This manner of patching may also be used for areas of surfacing that are not in the main traffic area, but it is permissible to patch these areas on the top side. However, should considerable traffic occur on the area that must be repaired, the patch should be applied to the bottom side of the membrane. If free water is found on the soil subgrade beneath the membrane, patching can be expedited by applying the patch to the top surface of the membrane. When a failure is patched from the top, an area approximately 2 feet wide surrounding the failure will be cleaned to remove all dirt and foreign material. Then adhesive will be applied to the cleaned area and to the swatch of membrane used for the repair.

After the adhesive becomes tacky, the adhesive-coated swatch of membrane and the adhesive-coated surfacing will be placed in contact and allowed to set for approximately 15 minutes. The patched area is then rolled with a light wheeled vehicle. If the failure is large or irregular, it may be necessary to use some of the anchors furnished with the maintenance kit to anchor and reinforce the repaired surfacing. When anchors are used to repair the surfacing, care will be exercised to ensure that adequate patching material is used to cover the heads of all anchors completely and extend 2 feet beyond the failed area of surfacing.

Procedures described above for repairs during dry weather are also applicable for membrane repairs during inclement weather with the exception that the surfacing does not have to be dry, but it must be free of mud. The wet-weather adhesive (adhesive furnished in 1-gallon pails) will adhere to wet membrane surfacing, and it can be applied to the surfacing during rains. The bond strength of the wet adhesive usually decreases after a period of two to three weeks; therefore, it will be necessary to replace the wet-weather patch with a dry-weather patch as soon as the weather permits.

The thickness and stiffness of the heavy-duty membrane surfacing are such that it is always necessary to exercise care in the construction of adhesive joints to prevent wrinkled joints. If wrinkles extend the full width of a joint, water will pass through the wrinkles and wet the underlying soil subgrade. Cartridges of sealant are furnished in the maintenance kits that will be used to seal these wrinkles. The sealant will be applied with a caulking gun to the wrinkled joint area. The bead of sealant will be beveled with a putty knife so it will be flush with the upper surface of the membrane.

The minimum crew and equipment required to perform routine maintenance to membrane-surfaced airfields are as follows:

Maintenance and Repair of Nonskid Compound

When 25 percent or more of the original factory-applied nonskid compound has been removed from the membrane surfacing, it will be necessary to apply nonskid compound to the surfacing. The nonskid compound will be applied to the surfacing with paint rollers at a rate of 80 to 100 square feet per gallon. The compound consists of two components: the accelerator, which is contained in a steel compartment located in the top of the 5 1/4-gallon pail, and the basic compound located in the lower part of the pail. The nonskid compound will be mixed by pouring the accelerator into the pail with the basic compound and thoroughly mixing these components for a minimum period of 15 minutes. One of the 1x4-inch braces on the maintenance kit can be used to mix the nonskid compound. When the components are mixed adequately, the compound will be allowed to set for a period of 45 minutes before it is applied to the membrane surfacing. Paint rollers with 48-inch-long handles will be used to apply the nonskid compound to the surfacing. It will be applied to provide complete coverage of the surfacing in the traffic area. A minimum cure time of 24 hours will be allowed for the nonskid compound before traffic is resumed on the surfacing.

The minimum crew and equipment required to apply nonskid compound to membrane surfacing are as follows below:

Replacement of Membrane Surfacing

Replacement kits are provided so that one or more sections of membrane surfacing can be replaced.

These kits will be used only when it is not feasible to perform expedient repairs to an installed section of surfacing. A failed section of membrane surfacing will be removed by first cutting it at the sides parallel to and approximately 6 feet from the side anchor ditches and end anchor ditches if the panel is the first or last panel in the pad. These cuts will extend to the 3-foot-wide construction joint located at the ends of a section. The surfacing will also be cut free at each end where the edge of the reinforcing strips joins the section of membrane. The failed section of membrane surfacing will be removed after it has been cut free on all four sides. The reinforcing strip at each end of the removed section will also be cut approximately 6 feet from the side anchor ditches. Although the full width of the strips will be cut, extreme care will be exercised so that only the reinforcing strip is cut and not the underlying surfacing. After the strips are cut, they may be removed by peeling one end loose by hand for a length of 4 to 5 feet and then attaching the loose end to the bumper of a vehicle. The vehicle will be moved slowly so that the remaining length of the strip is peeled loose. The steel anchors will be exposed when the strip is peeled loose. These anchors will be pried out of the ground with picks and/or shovels. The 2-foot-wide piece of membrane from the failed panel forming the construction joint at the ends will also be cut and removed. The replacement section of the membrane surfacing will be unfolded and positioned on the runway in the same manner as that described for membrane placement and will overlap the cutaway areas or adjacent membrane panels. Care will be exercised to ensure that the centerline of the replacement section is aligned with the centerlines of the adjacent sections of membrane. Transverse construction joints will be constructed on both ends of the replacement section in the same manner as in membrane placement. The sides of the replacement section ill be lifted and adhesive will be spread at intervals 10 to 12 feet long and approximately 2 feet wide. After the adhesive becomes tacky, the two sections will be placed together. This procedure will be continued for the full length of the repair. Reinforcing strips are not required for these adhesive joints at the sides. Adhesives supplied in the replacement kits may be used during both dry and wet weather.

The minimum number of personnel and equipment required to replace one or more sections of membrane surfacing are as shown at the bottom of the page.

REPAIR AND MAINTENANCE OF SOIL SUBGRADE

When the soil subgrade beneath the membrane surfacing becomes rutted by aircraft traffic to the extent that the ruts constitute a hazard to aircraft operation, the subgrade will be repaired. If possible, the subgrade will be repaired by leaving the membrane surfacing in place and cross-rolling the rutted area to smooth out the cuts and compact the area. Rolling can be accomplished with a steel wheel roller, rubber-tired roller, or a loaded 5-ton dump truck. If any of this equipment causes the subgrade to pump, it will be necessary to slit the membrane surfacing and fold the surfacing back to provide working room for construction equipment. Sometimes, the subgrade can be dried by scarifying the soil and allowing it to air dry; in other cases, the wet soil will have to be excavated and replaced with dry backfill material. The dry soil will be compacted with one of the pieces of construction equipment listed previously. Operation of construction equipment, especially steel-tracked bulldozers, should be in a direction parallel to the width of the surfacing. This will allow the equipment to enter and leave the area without traversing the membrane surfacing. Once the area has been repaired, the membrane surfacing will be returned to its original position and patched, as discussed previously in the section on membrane maintenance.

RECOVERY OF MEMBRANE SURFACING

When aircraft operations are completed on a membrane-surfaced airfield, the surfacing may be removed from the airfield and installed at new locations. This may be accomplished by two methods--deliberate and hasty.

 

Deliberate Recovery

Deliberate recovery of membrane is accomplished in the reverse manner in which it was placed. This method does not damage the membrane and is used to recover 90 to 100 percent of the surfacing. This method is slow and requires careful supervision and much work. The procedure is as follows:

The soil backfill will be removed from the end and side anchor ditches with a motor grader. Approximately 2 to 3 inches of soil should be left in contact with the surfacing to prevent cutting the surfacing with the blade of the motor grader. This leftover soil backfill will be removed from the anchor ditches with hand shovels. The 3-footwide strips of membrane that reinforce each adhesive construction joint will be removed first by peeling one end loose for a distance of approximately 5 feet, and then attaching the loose end to the bumper of a vehicle. The vehicle will then be used to pull the 3-foot-wide strip loose from the surfacing. When all backfill is removed from the ditches, anchors that have been exposed in each adhesive construction joint and in anchor ditches will be removed after prying them loose from the subgrade with picks and shovels.

After anchors are removed, one corner of the uppermost section of membrane will be peeled loose by hand for approximately 5 feet, then the loose corner will be wrapped around the bumper of a truck, and the truck will be moved slowly across the runway until the sections are separated. After sections are peeled apart and all anchors removed, they will be turned over so that the dirt and mud that have accumulated on the bottom side of the surfacing can be removed with shovels and brooms. Failures that are found when the underneath side is cleaned will be repaired. The repairs will be made with materials from the maintenance kits. When the supply of membrane material in the maintenance kits is depleted, the 3-foot-wide reinforcing strips that were peeled from the adhesive construction joints will be used to repair additional failures. After the sections are swept clean and repaired, troops stationed at equal intervals along the lengths of the sections will accordion-fold each section of membrane into a bundle approximately 48 inches wide and 53 to 100 feet long. Each folded section will then be accordion-folded onto wood pallets. The end of the folded section will be placed on a pallet and held in place by troops while three 10-foot-long pipes are positioned at equal intervals beneath the membrane surfacing for a distance of 12 to 15 feet. The troops will hold the surfacing with the pipes high enough to clear the pallet while a forklift truck moves the pallet beneath the surfacing. As the forklift truck moves forward, the surfacing will be lifted with the pipes and accordion-folded onto the pallet. Steel straps will be used to secure each section of membrane to the wood pallet.

NOTE: Steel straps are not furnished with membrane kits. Prior to recovery, adequate banding equipment, steel strapping, and nails must be obtained from depot stocks.

Personnel and Equipment

The number of personnel and equipment required to remove the membrane surfacing will be determined by the size of the area that is surfaced. The minimum number of personnel and equipment required to handle sections of membrane and perform tasks are listed below.

Hasty Recovery

The hasty recovery is identical to the deliberate recovery except that the membrane is cut at the edges and the portions in the anchor ditches are left in place. The hasty method is faster and requires less supervision, but the width and length of the membrane are shortened by the amount left in the anchor ditches. The shortened membrane can be reused on another field with narrower runway requirements or as a taxiway, warmup apron, or helipad surfacing.

STORAGE OF MEMBRANE SURFACING

The crated sections of membrane surfacing and accessories, maintenance kits, and replacement kits can be stored in open or closed depot storage. The crates are constructed so they can be stacked three high in tiers. The materials used to construct the crates will last indefinitely in closed storage and approximately 10 years in open storage. The items contained in the wood crates will last indefinitely in open or closed storage. If the crated sections of membrane are stored in the open, they will be placed on an area that has adequate drainage so rainwater will not puddle under the wood crates, which will shorten the life of the crates.

MATS

LANDING MAT

The use of a landing mat to construct an airfield will depend on many factors. The type of airfield and using aircraft, characteristics of the subgrade, time to construct, and the number of sorties desired will all impact on the decision.

Time is the most critical factor, and it is essential that TO airfields be completed at the specific time requested and remain operational long enough for the pertinent military mission to be completed. The proper use of the items described herein will enable troops to construct an assault airfield in a minimum amount of time.

MAT CLASSIFICATION

There are currently five types of mats available for use as airfields (Table N-4). These have been placed into three classifications based on the following criteria:

Light-Duty Mats

Light-duty mats must be able to withstand 1,000 coverages of a 30,000-pound, singlewheel load with a tire pressure of 100 psi on a subgrade with a CBR value of 4 (AI = 6). These criteria must be met without the occurrence of excessive deflection under load and no more than 10 percent replacement of failed panels. Other requirements are that the mats weigh 3 pounds per square foot or less of usable area and be in sections small enough to be readily placed by hand.

Medium-Duty Mats

Medium-duty mats must be able to withstand 1,000 simulated coverages of a 25,000-pound, single-wheel load with tire pressures of 250 psi on a subgrade with a CBR value of 4 (AI = 6). These criteria must be met without the occurrence of excessive deflection under load and no more than 10 percent replacement of failed panels. Other requirements are that the mats must weigh 4.5 pounds per square foot or less of usable area and be in sections small enough to be readily placed by hand.

Heavy-Duty Mats

Heavy-duty mats must be able to withstand 1,000 simulated coverages of a 50,000-pound, single-wheel load with a tire pressure of 250 psi on a subgrade with a CBR value of 4 (AI = 6). These criteria must be met without the occurrence of excessive deflection under load and no more than 10 percent replacement of failed panels. Other requirements are that the mats must weigh 6.5 pounds per square foot or less of usable area and be in sections small enough to be readily placed by hand.

Preliminary Considerations

Proper evaluation and grading of the subgrade are critical for the proper use of landing mat. A profile to the depth of 24 inches will indicate the soil strength pattern to preclude the possibility of overstress at some point in the underlying subgrade. The length and design of the airfield must be determined from Chapter 11, and the subgrade must be crowned within the proper grades allowable. Mats must not bridge any gaps or a failure may occur.

Membrane must be placed under all landing mat in high-traffic areas, such as runways or taxiways, to waterproof and dustproof the subgrade. The membrane must meet MIL-C-43006D. Type 1 specifications and be at least single-ply, vinyl-coated, nylon cloth weighing approximately 18 ounces per square yard or the equivalent. Current Army membrane is adequate for this. The membrane is not required to be placed in a trench, as with a membrane-only airfield, but it must extend at least 6 inches past the edges of the matting. If two or more sections of membrane overlap, an adhesive joint must be formed or the matting overlapped by 1 foot to prevent water from passing into the subgrade. An adhesive joint is preferred.

You must also consider and plan for drainage. Placement of culverts and ditches may be required across the airfield and should be emplaced before the landing mat is laid.

Material Requirements

After the airfield or helipad dimensions have been determined from Chapter 11 or 13, respectively, and the runway length calculated from Chapter 10, the material requirements can be calculated in four steps: width determination, length determination, total panels, and additional ancillary requirements. Table N-5 provides formulas for calculating landing mat requirements for the M19. Table N-6 provides formulas for calculating landing matting and ancillary requirements for the M19. Table N-6 can also be used to determine the ancillary requirements for all other mats. The matting and ancillary items will be delivered to the airfield on pallets.

Prior to mat placement, the baseline for one edge of the proposed runway should be established by using a transit and should be clearly marked with a string line or stakes. As the laying of the mat progresses, the alignment of the mat edge or sides should be checked periodically to ensure straightness of the runway. This is very important because straightness is necessary for landing aircraft and attaching mat to make 90-degree turns.

Pallet Distribution M8A1 Steel Mat

The pallets of mat should be distributed along each edge of the proposed runway and in a line equal to two-thirds of the runway width plus 4 feet inside the runway edge that will have the starting row of runway mats (Figure N-3). With this arrangement, the longest carrying distance will be slightly more than one-third of the runway width. Pallet spacing can be computed as follows:

Place additional equipment pallets at the edge of the runway at intervals required for best distribution in relation to mat pallets.

Airfield Layout

The determination of the lengths and widths of airfields is discussed in Chapter 12, and sample airfield layouts are given in various figures throughout this section. There are some additional design patterns that may be needed due to terrain and mission requirements.

Fillets. A fillet will normally be used to round off an area where aircraft are required to turn, such as where a warm-up apron meets the taxiway or runway. The purpose of the fillet is to increase the mat-surfaced area to help in preventing aircraft from going off the matting during a turn. In constructing the fillet, the mats are placed to cover the required design area but the edge is left stepped (Figure N-4). The matting will also be anchored as required by the mat type.

Oblique taxiways/warm-up aprons. Occasionally, it may be necessary to place matting obliquely at an intersection. To do this, the mat is offset for the required design area and the edge is left stepped (Figure N-5), The mat is also anchored as required by the mat type.

M8A1 Steel Mat

The M8A1 mat is classified as a light-duty mat formed of 0.125-inch-thick steel plates that can be placed on a crowned subgrade of up to 2 percent. The panels are 11 feet 9 3/4 inches long, 1 foot 7 1/2 inches wide, and weigh 144 pounds (or 7.5 pounds per square foot). The mat is classified as a light-duty mat: however, it does not qualify based on performance or weight. The panels can be placed at a rate of 243 square feet per man-hour. The mat comes in pallets of 13 standard and 2 half panels.

The panels are solid planks, and the end connectors incorporate moment transferring end joints made up of four sliding steel bars that are 3/4 x 3/4 x 10 1/2 inches. A bayonet connector is along one side of the panel, and the other side rolls under the bayonet slots when attached to another panel to form a smooth contour at the subgrade and furnish additional strength along the side. The locking lug can be bent up or down to facilitate removing and replacing (Figure N-6).

The two ends of the mat form underlap and overlap edges. When placing panels, the underlap end must be placed on the bottom, and the overlap end is then placed on the top. A reversal of the underlap and overlap positions is not possible because the underlap end ribs will not seat fully and will also prohibit an even surface.

When laying an airfield with M8A1, the first panel to be placed should be the panel in the upper left-hand corner of the field as the crew faces its work, with the bayonet lugs facing away from the laying crew and the slot side adjacent to them. This places the underlap end on the right and the overlap end on the left. After the first panel is placed in the upper left-hand corner of the field, the second panel is joined to the first panel by sliding the four end connector bars into the receiving slots. The remaining panels in the first run are continued in this manner for the entire width.

The first run must be completed for alignment purposes before any other run can be started. The second and following runs, however, can be started as soon as enough panels have been laid in a run to allow for the placement of the next run of panels. The follow-on runs, however, may not surpass the previous run since proper locking of the runs together will be impossible.

After the first row of panels has been placed, the second and follow-on rows of panels are placed by holding the panel at approximately a 45-degree angle to the previous row's panel. The bayonet lugs of the panel being laid are engaged in the side slots of the laid panels. The panel is then slid until the bayonet lugs are securely locked in the slots and the locking lug behind the bayonet lugs is positioned in the slots. The locking lug will fit into one of the two locking lug slots of the laid panel to prevent future sliding when the loose plank is lowered back to the ground in its final position.

To make the locking lugs line up, all panels in a run must be slid in the same direction--right or left. Panels in alternate runs are then slid in the opposite direction to maintain edge alignment and to ease removal for maintenance.

M8A1 mat can be placed by using multiple crews. Figure N-7 depicts this procedure. Notice that when multiple crews are used, the mats are welded where the placement crews meet.

The welded juncture may be formed in many ways. The planks of the junction may be cut to form a butt weld, or for a stronger joint, both planks are cut in a rib valley and joined. This joint can also be strengthened by welding short pieces of scrap steel at intervals over the joint.

If the pad should have an even finish, all odd-numbered runs will start with a full panel to ensure staggering of the joints (Figure N-8a). All even rows will start and finish with a half panel. If the pad is not required to have an even finish, all even runs will start with a full panel offset from the previous run (Figure N-8b).

After every 60 to 70 linear feet of matting has been placed, laying operations are stopped and the mat is stretched tight by using truck winches or other equipment as available. This stretching is necessary to maintain alignment and prevent buckling of panels due to temperature changes.

The placement of panels will continue as outlined until the pad is completed or one crew meets the next crew, whereupon the mat sections are welded.

Runway alignment of the matting must be assured throughout the placement procedure. To assure alignment during placement, the survey party should be available to keep constant check on alignment. This may be accomplished with a transit or by using the 3-4-5 triangle method. Drift or realignment can be corrected at the time the mat is being stretched. The use of temporary anchor stakes at the runway edge after the planking is stretched will assist in maintaining alignment.

Alignment may also be controlled by placing a line along the centerline. This line is then used to control placement by assuring the alignment of joints that fall along it.

To prevent curling and shifting of panels during operations, the panels along the edge of the runway or taxiway must be anchored. This may be done in several ways.

  • Where full panels are offset in the even runs, as in Figure N-8b, the extended portions of panels are bent downward into a 2:1 trench, and the trench is backfilled (Figure N-9).
  • Where half panels are being used to finish the sides of the runway (Figure N-8a) to an even line, a full panel will be used at the ends of every fourth or sixth run and bent into a 2: 1 trench and then backfilled (Figure N-9).
  • The extended sections to be buried can be bent by a roller or a truck. Panels may also be bent or beaten into shape with a sledgehammer as required. A cutting torch may be used to cut out a small notch in the ribs, which will greatly reduce the load required to bend the panel and help in controlling the point of bending.
  • Where half panels are used to an even edge, an alternative method is to anchor the mat with cables tied to deadmen buried along the sides. Earth anchors consisting of 3/4-inch reinforcing rod, 40 inches long, are also used to anchor sides of runways, taxiways, or helipads. The top 6 inches of the rod should be bent over the mat.
  • At the ends of runways, a 2:1 trench is excavated at each end of the runway across the entire runway width. The panels are continued down the slope of the trench for 6 panels. After the panels are in place, the trench is backfilled and compacted (Figure N-10).

Warm-up Aprons, Hardstands, and Fillets

Construction of hardstands and fillets can be preceded in two ways--by making them an extension of the trafficway or, preferably, by running the panels perpendicular to the line of travel and welding the panels at the junctures. The first method places the panels parallel to the line of travel, but it has advantages such as ease of construction and saving time and material. It is a satisfactory method when traffic will be light.

Warm-up apron panels must be placed perpendicular to the line of travel due to the amount of traffic involved. The juncture of the panels will be welded in the same manner as described for runway/taxiway placement. A fillet may also be used to round off corners.

Staking down of the panels in these areas is generally satisfactory anchorage. When time permits, the edges should be buried in the same manner as for the runway/taxiway to prevent curling.

Recovery, Cleaning, and Bundling of M8A1 Matting

Removing. Generally, the panels will be removed in the reverse order they were placed. The connecting tabs will be unlocked and the panels will be raised to a 45-degree angle with the ground. The panels will be slid about 3/4 inch to the left or right to align the bayonet hook with the hook slot and then removed. It may be necessary to pry a panel from the side connection in order to lift the panel. After two or more panels in a run are removed, removal of the adjacent run's panels may begin, resulting in a stair-step pattern for removal.

Before bundling the panels for shipment, the connecting tabs should be inspected and tack welded as required.

Cleaning. Most of the adhered soil can be loosened from the panels by dropping the panel 4 to 6 feet, flat onto a hard surface, such as a concrete pad or other panels. Bars can be used to loosen the soil by running the bar down the ribs of the panel before or after dropping the panel. Soil must be removed from the connecting edges, or the panels will not connect properly for reuse. It may be necessary to use water under high pressure to remove soil wedged in the female side connection.

Bundling. M8A1 mat is repackaged in bundles containing 13 full and 2 half panels. The panels will be nested in pairs, bottom to bottom, with like panel ends together and the connector protected between the box edge and the first rib of the other panel in the pair. (The two half panels will be stacked with a full panel to make a nested pair, and the pair will be placed in the interior of the bundle.) The nested pairs are then stacked on two 2x4s for skids so that the ends of alternate pairs are reversed. A bundle will be secured with six flat, steel traps. Four of the straps will be placed transversely (to encompass the two longitudinal straps) around the short dimension of the bundle, two of which will be 18 inches from the ends with the interior straps equally spaced. The two longitudinal straps will be at the one-third points, and all straps will be properly tensioned for shipment.

Criteria for Mats to Be Reusable

Used panels can be grouped into three separate classes: Class 1, reusable as is; Class 2, reusable, but in need of minor repair; and Class 3, unusable. The essential factor in deciding if a panel is reusable is whether it will fit together with a new panel (used as a standard gauge). Acceptable panels may have--

  • One of the end locking bars missing.
  • Four of the bayonet hooks missing. (No two adjacent bayonets may be missing.)
  • Minor cracks not exceeding 1 inch in length (no sharp or protruding edges).
  • One of the end connector bars (hooks) missing. Bent or slightly deformed bayonets should not cause a panel to be unusable because the bayonets can be easily straightened with hand-tools.

AM-2 Mat

AM-2 mat is a non-Army, medium-duty mat used by the Air Force, Navy, and Marines. Army units can expect to encounter AM-2 in the TO, especially during joint operations.

AM-2 mat is a fabricated aluminum panel that is 1 1/2 inches thick, 12 feet long, and 2 feet wide. It consists of a hollow, extruded, one-piece main section with extruded end connectors welded on each end. The mat weighs 5.8 pounds per square foot, qualifying as a medium mat on performance, not on weight. The panels can be placed at a rate of 163 square feet per man-hour and on a subgrade crowned up to 1.5 percent (Figure N-11).

The connectors of the mat consist of an overlap/underlap on the ends and a male/female hinge joint on the sides. A flat locking bar is inserted into the slot common to the panels to form a nonseparable joint (Figure N-12).

AM-2 Pallets

Mats and necessary ancillary items are packaged in pallets for movement to the TO.

Standard pallet. The standard pallet contains enough matting to construct three runs (6 feet) on a runway or taxiway that is 72 feet wide.

Ancillary pallets. AM-2 ancillary equipment is packaged by like items, and the sizes will conform to the item sizes.

Ancillary Items

The AM-2 mat uses various ancillary items that are different from other mats.

Keylock adapters are bars that are very similar to the access turning and starter adapters of M19 matting. These are also locked to other keylock adapters by a socket head screw. Five types of keylock adapters are available and listed below:

Starter keylock (Figure N-13). A starter keylock is used most often to mate the female ends of an 80-degree adjustable connector and adjoining mats. Starter keylocks are furnished in 3-, 8-, and 12-foot lengths to provide for staggering of joints in matting patterns. The starter keylock is coated with nonskid material.

Typical keylock (Figure N-14). A typical keylock is inserted every 100 feet in the pattern to permit the easy removal of sections of mat for multiple mat replacement. Thus, a maximum of 50 feet of any section need only be removed to replace mats that could not economically be replaced as individual units by replacement mats. Typical keylocks are furnished in 3-, 9-, and 12-foot lengths to provide for staggering of joints of mat patterns. The typical keylock is coated with nonskid material. Typical keylocks may also be used alone or in combination with adjustable keylocks and/or spacer mats to fill the last row of replacement mat when the run space is less than 24 inches in width.

Female keylock (Figure N-15). A female keylock is used to join two adjacent male mats. The female keylock is coated with nonskid material.

Adjustable 90-degree connector (Figure N-16). The adjustable 90-degree connector is used to join two mat patterns that are adjacent to each other at a 90-degree angle, such as the main runway and a taxiway. Connectors are 12-foot-long, aluminum sections that can be adjusted in width from 6 1/2 inches to 9 1/2 inches to facilitate the joining of two adjacent matting sections.

Adjustable keylocks (Figure N-17). Adjustable keylocks are provided to fill the last run of installed matting when the run space is less than 24 inches wide. These keylocks may be used alone or in combination with typical keylocks and/or spacer mats, depending on the width of the row space. Adjustable keylocks are furnished in 3-, 6-, and 12-foot lengths and can be adjusted to expand from 6 to 9 inches in width. Right and left adjustable keylock assemblies are comprised of a combination of 6-foot, male and female keylock assemblies.

Expansion in width of these keylock assemblies is controlled by a keylock screw in the male keylock assembly that rides in a slot in the female keylock assembly.

Adjustable keylocks are coated with nonskid material.

Adjustable keylocks provide a dual function--they are used for linear expansion due to temperature change, and they facilitate the joining of previously installed landing mat with adjoining mat.

Adjustable keylocks are not to be used in runway areas. They are to be used on parking and taxiway areas only.

Locking bars. Locking bars are used to interlock the mats and are inserted in the upturned-downturned connection in the mats as the mat is laid. Locking bars come in 2-foot lengths and are 5/8 inch wide.

Blast-deflector adapter (Figure N-18). The blast deflectors are provided to protect the area surrounding the airfield from the blast of the engine exhaust. The deflectors also help to limit the amount of dust caused by jet engines. These deflectors consist of mat sections held at about a 60-degree angle to the horizontal by blast-deflector adapters, which are 2 feet long. They can be installed along the edges of the taxiways and parking areas but are not used along the runway.

The Type I adapter joins to the male edge of the mat and to the female edge of the mat. Type II joins to the prongs-up end of the mat. Type III joins to the prongs-down end of the mat.

Tie-downs (Figure N-19). Tie-downs are provided for aircraft anchorage and are bolted in place on the site by drilling and tapping the necessary holes in the AM-2 mats, according to aircraft configuration in the parking areas.

Removable end connectors (Figure N-20). Removable end connectors are used to expand the runway width from 72 to 96 feet as required to enlarge an air base. The removable end connectors separate into two halves, which enables the quick replacement of 6-foot mats with 12-foot mats. A flat, locking bar is inserted into the slot common to the removable end connector and the mats to form an inseparable joint.

Mat push-pull fixture (Figure N-21). The mat push-pull fixture is used to remove and replace a partial or complete row of mats. Rows of mat are removed for replacing damaged mats and for installing removable end connectors on existing installations. The fixture provides a fork pocket for pushing a single end mat or an entire row with the tines of a forklift. The fixture is provided with shackles to accommodate a wire-rope sling for pulling the mats out of the brickwork pattern.

Replacement mats (Figure N-22). Replacement mats allow for the replacement of damaged mats with a replacement item that duplicates the original installation, reestablishes the brickwork pattern, and requires only the removal (by cutting) of the original damaged piece. These mats are complete with a nonskid coating. Replacement mats are prepared from AM-2 mats by cutting off the prongs-up edge and the male-connector edge and welding on adapters. Additional adapters must be bolted on at the time of installation. In case of site disassembly, replacement mats may be disassembled and used as standard mats without further alteration. They may also be disassembled and saved as prepared replacement mats for the next installation.

Heavy-duty mats (Figure N-23). Heavy-duty mats are provided under the arresting gear pendant to eliminate damage during aircraft arrestment procedures. These mats are 6 feet long and 18 inches wide. Heavy-duty mats are painted green, and the top surface is also coated with nonskid material of the same color. Locking bars used to secure heavy-duty mats together are approximately 6 feet long.

Spacer mats (Figure N-24). Spacer mats are also provided to fill the last row of replacement matting when the row space is less than 24 inches wide. These mats may be used alone or in combination with typical keylocks and/or adjustable keylocks. Spacer mats are furnished in 6- and 12-foot lengths and are 12 inches wide. The spacer mat is coated with nonskid material.

Edge clamps and stakes (Figure N-25). Edge clamps are provided to secure AM-2 mat at aircraft taxiing and parking area turning points. Stakes are driven into the ground to anchor the edge clamps to the mats.

There are four types of edge clamps:

  • Type I edge clamp anchors female edge of mat.
  • Type II edge clamp anchors male edge of mat.
  • Type III edge clamp anchors downturned prongs of mat.
  • Type IV edge clamp anchors upturned prongs of mat.

Short locking bars are used to secure Type III and IV edge clamps to the mat.

The quantity and location of edge clamps may vary for a specific installation, depending on soil and environmental conditions.

INSTALLATION INSTRUCTIONS

Installation of an AM-2 airfield can be conducted by either starting at one end of the runway and proceeding in one direction down the runway or by starting at the transverse centerline of the runway and proceeding toward each end simultaneously.

A typical placement crew is broken down as shown below.

The coated side of the mat is always up, and the interlocking prongs on the short (2-foot) edge are always to the right and up. Survey lines are used to ensure longitudinal alignment on at least one edge of the matting section. A typical keylock section is laid every 100 feet to allow easy access to panels for repair and maintenance.

AM-2 airfields are generally designed using two runway width criteria--72 feet and 96 feet. The 72-foot width is designed to meet initial runway standards; its design life is up to 6 months, and it can be easily upgraded to a 96-foot-wide temporary airfield with the use of removable end connectors. The removable end connector cannot be used when laying landing mat in two directions from the transverse centerline but only when the entire airfield has been laid in one direction. The choice of which method to use for laying the matting depends on the mission. While laying mats in two directions at once is faster, airfield upgrade may take longer without the removable end connectors.

INSTALLATION SEQUENCE

The placement of panels for an AM-2 airfield is much the same whether laying a 72- or 96-foot-wide runway or using a starting keylock and laying in two directions at once. Before laying the mats, visually inspect the sides and end connectors for foreign matter. Brooms and brushes should be capable of cleaning the mat.

If placing the mat from one end of the runway to the other, the first panel will be placed on the upper left side of the runway with the nonskid side up, the overlap hinge on the outside edge, and the male hinge inside the field. The first and all odd runs will start and end with a half panel (Figures N-26 and N-27). The next mat placed will be a fill mat on the first run. A locking bar will be inserted in the rectangular slot formed by the joining of the mats (Figure N-28). The third mat placed will be the first mat of the second row. The mat is placed by holding the panel at a 45-degree angle to the mat in the preceding run engaging the female connector over the male end and lowered to the ground. The mat placement will continue in the stair-step pattern as shown in Figures N-26 and N-27 until the entire runway is completed. If a 72-foot-wide runway is to be increased to a 96-foot-wide runway later, removable end connectors should be placed between the last full and half panel on every odd run. This will assist in upgrade of the airfield (Figure N-29).

When laying a runway in two directions, a starter keylock adapter will be placed transverse to the centerline at the midpoint of the runway. The length of starter adapters to use will be in the same configuration as the typical keylock pattern shown in Figures N-26 and N-27.

The first panel will be placed in position 1 (Figure N-30) by holding the panel at a 45-degree angle to the ground so that the female connector is engaged over the male and lowered into position. Subsequent panels will be placed left to right (facing the transverse centerline) in sequence (2, 3, 4, 5, and so forth) in a stair-step pattern as indicated in Figure N-30. Note that a half panel is used in alternate runs to provide a staggered pattern. This pattern will be maintained throughout placement. The ends of panels will be locked by inserting the locking bar in the locking bar slot. After two to four runs have been placed to ensure proper alignment, a second crew can begin placement in the opposite direction (and from the opposite side) using the same placement procedure described above. On the opposite side, however, odd runs will start and end with full mats while even runs will start and end with a half mat (Figure N-30).

For all airfields, a typical keylock will be installed every 100 feet across the entire matting field. The keylock lengths are shown in Figures N-26 and N-27. The keylocks permit the easy removal of matting for multiple mat replacement. After the keylocks are installed, matting placement will continue using the same procedures described above.

At the ends of the runway, five full mats will be buried in a 5:1 sloped trench for the full width of the runway. The trench is then backfilled and compacted to match the original subgrade contours (Figure N-31).

Along the edges of mats, edge clamps are used to secure the mat to stakes driven into the ground. There are four types available, and they will be placed in the same pattern as described for truss-web matting. The stakes used for holding the edge clamps into place are driven into the ground with sledgehammers or pavement breakers. An attachment used to prevent the deformation of the head of the stake will permit this (Figure N-32).

Heavy-duty, AM-2 mat must be placed under areas where arresting cables will be used. These mats are placed 90 degrees in relation to the placement of the standard AM-2 mats (Figure N-33).

When mats are required to make a 90-degree turn (such as for taxiways, warmup aprons, or parking aprons) enough 90-degree adjustable connector will be installed to equal the width of the sections to be joined. Placement of mat will be the same as described above for laying mat from end to end (Figure N-34).

Runway Conversion (72 to 96 Feet Wide)

The following steps outline the procedures for enlarging an existing 72-foot-wide runway. The conversion requires the laying of additional AM-2 mats and can be accomplished in two ways as follows:

With Removable End Connectors

Steps:

1. Remove four socket-head cap screws from the removable end connectors (Figure N-35).

2. Remove the half mat with half of the removable end connectors attached (Figure N-36).

3. Remove the locking bar and half of the removable end connector from the half mat.

4. Install the removable end connector to a new, full AM-2 mat.

5. Slide the new mat into the place vacated by the half mat.

6. Install the four socket-head cap screws previously removed.

7. Lay the second mat by mating the down-turned prongs with the upturned prongs of the preceding mat. A rectangular slot is formed when two mats are properly engaged.

8. Lock the mats together by inserting a locking bar.

9. Complete the first run of the new AM-2 mats by reinstalling the half mat previously removed.

10. Fill in the second run with two full mats (Figure N-36, step 3).

11. Remove the next half mat and the removable end connector in the third row before installing the next run.

12. Complete each succeeding run as shown. Complete each odd run according to steps 1 through 8 above and each even row according to step 10.

Without Removable End Connectors (Figure N-37)

Steps:

1. Install the mat push-pull fixture (Figure N-21) to the first half mat on the side of the runway to be expanded.

2. Attach the wire-rope sling to the mat push-pull fixture and the forklift truck.

3. Pull the entire run of mats out approximately 7 feet, using two other forklift trucks. Remove the wire-rope sling.

4. Remove the locking bar and the half mat.

5. Install the new, full AM-2 mat in place of the half mat removed and insert the locking bar.

6. Lay the second full mat and the half mat previously removed to complete the first run. Insert locking bars when required.

7. Push the first row in about 7 feet using mat push-pull fixture and forklift trucks as shown.

8. Remove the push-pull fixture.

9. Lay the two full AM-2 mats to complete the second run of runway expansion.

10. Repeat steps 1 through 9, as required, to complete runway expansion.

Blast-Deflector Installation

To shield the ground area around taxiways and parking areas from the blast effects of aircraft, install blast deflectors as required. Assemble blast-deflector adapters to boundaries of mats, which will be female or male edges, prongs-down ends, or prongs-up ends. Three types of adapters are supplied to fit any one of the four joints. Erect AM-2 mats to the exposed upturned edge of the adapters to provide the blast shield. Use two adapters to support each AM-2 mat. (See Figure N-38.)

Joining AM-2 Matting with M19 Matting

AM-2 and M19 can be used together on taxiways and aprons with some additional ancillary items. This is discussed under the M19 section. Mixing of mat is not recommended on the runway.

M19 MEDIUM-DUTY MATTING

The M19 mat is a sandwich-type structure containing a 1.375-inch-thick aluminum, honeycomb core bonded top and bottom to 0.063-inch-thick aluminum skins as shown in Figure N-39. Extruded aluminum connectors are bonded to the edge of the core with a potting compound and are welded to the top and bottom skins. Two edges of the panel have overlap-and underlap-type joints that are connected to adjoining panels and locked with an extruded, aluminum locking bar. The other two edges have male-and female-type hinge connections. An exploded view of the mat is shown in Figure N-40. The individual panels are 1 1/2 inches thick, 50 1/4 inches long, 49 1/2 inches wide, and weigh approximately 71 pounds. A panel covers approximately 16.7 square feet and weighs 4.25 pounds per square foot of placing area.

The M19 mat is designed to be placed on a subgrade with a strength of CBR 4 (AI 6) or greater and to sustain 1,000 coverages of a 25,000-pound, single-wheel load with 250-psi tire inflation pressure and a contact area of 111.1 square inches. The panels can be placed on a three percent crown at a rate of 350 square feet per man-hour. A basic mat-placing crew consists of seven men (one NCO and six enlisted members (EMs)); however, as many as five crews can lay mat in one direction as work progresses on the runway. The panels are normally laid with the male-female joints parallel to the direction of traffic and continuous along the runway length. The traffic is therefore always applied in a direction perpendicular to the end connector locking bars (Figure N-41).

M19 PALLETS

Mats and necessary ancillary items are packaged in crates for shipment to the TO. The crates form skid-mounted pallets for ease of handling with mechanized equipment.

Full-Mat Pallets

Full mats are stacked on four-way-entry, wood skids to make a pallet package of 32 mats. Each mat is supplied with one locking bar placed in the upward facing groove of the underlap edge of the mat plus one additional bar per bundle, making a total of 33 bars per bundle. All sides of the pallet are covered with sheets of plywood, and the corners are protected by angular aluminum strips. The package is bound with steel bands. Gross weight is 2,484 pounds, and bundle dimensions are 51 3/4 x 51 inches wide and 55 inches high.

Half-Mat Pallets

The specially marked half-mat pallets are similar to the full-mat pallets except that they are approximately half the size of the standard mat bundles. The half panels are bundled in pallets containing 32 half panels and 33 locking bars.

Additional Pallets

The ancillary equipment, such as adapters and anchor attachments, are crated in packages that conform to the sizes of the parts. The specially marked repair mat pallets are similar to the half-mat pallets in size and contain 16 panels.

Ancillary Items

Descriptions of the various ancillary items used in conjunction with the M19 landing mat are given below:

Access adapter. An access adapter is an aluminum alloy bar with an overlap connector formed on one side and an underlap connector formed on the opposite side. The adapters are placed at intervals along the runway to permit easy access into the runway by withdrawing the access adapters from between mats. This allows nondestructive removal and reinstallation of mats in order that the damaged mats can be replaced, the subgrade repaired, and utilities added or repaired. The adapters are 4 feet long, and 25 adapters are shipped with 25 locking bars per bundle.

Anchor attachment. Male, female, and overlap/underlay hinge adapters fabricated from extruded aluminum alloy are used along the runway edges for attaching edge anchors to individual mat panels. The anchor attachments should be spaced every 8 feet (every other panel) along the sides of the field. Overlap/underlap adapters are used along the ends of taxiways and pads but are not required along the ends of the runway.

Edge anchors. Edge anchors are the ballauger type, fabricated from steel with a 4-inch helix plate. They are 2 feet long. A 1-inch-diameter hole is located in one end in order that a bar, a pneumatic tool, or the opposite end of another anchor can be inserted to screw the anchor into the ground.

Half panels. The half panels are approximately 4 feet long and 2 feet wide and are used in alternate rows at runway ends or are used in conjunction with starter connectors to provide a straight edge across the width of the field while creating a staggered end-joint pattern perpendicular to the direction of traffic.

Repair mats. These mats are used to replace damaged or failed mats. Each panel is fabricated in two pieces with a diagonal overlap/underlap joint between the pieces. Use of repair mats is limited to replacement of damaged mats where it is not practical to take up a section of the runway.

Locking bars. Locking bars, which are used to interlock the mats, are inserted in the underlap/overlap connectors in adjacent mats as each panel is laid. Aluminum alloy bars, 3/16 inch thick by 5/8 inch wide by 48 1/2 inches long, are used with the standard panels. Bars in various other lengths are used in conjunction with the repair mat.

Starting adapter. A starting adapter is an aluminum-alloy bar containing two underlay connectors formed back to back that is used to form a transverse line across the pad from which mat laying is started. The starting adapter allows the mat to be placed simultaneously in two directions. These connectors can be used either to speed the laying of a new field or to extend the length of an existing pad. These adapters come in 2- and 4-foot lengths.

Turn adapters. These are 90-degree adapters and 15-degree turndown adapters, required by changes in the geometry of the mat field and used to form a positive lock between panels being joined. Ninety-degree adapters are used in runways and taxiways to create intersections with cross taxiways and to connect M19 mats to AM-2 mats. Fifteen-degree turndown adapters are used at runway ends to allow burying mats for anchoring the runway. Four 90-degree adapters are available: female/overlap, male/overlap, female/underlap, and male/underlap.

INSTALLATION INSTRUCTIONS

No special skill is required for emplacing M19 landing mat once a well-prepared subgrade has been completed and a baseline has been determined. Panels can be placed on a subgrade crowned as much as 3 percent and at a rate of 350 square feet per man-hour.

Preliminary Inspection

Before the mats are placed in position, they should be given a quick inspection. Any accumulation of dirt, chips, or material left from fabrication in the connectors must be removed since their presence will prevent the proper interlocking of the mat units. Any damaged panels should be removed from the placement area.

M19 Placement

The first step in placing M19 mat consists of placing starting adapters across the runway midpoint, transverse to the centerline of the runway. The starting adapters are placed together, end to end.

Placing mat can only be initially started in one direction from the starting adapter. The first panel will be placed in position 1 (Figure N-42) by engaging the overlap edge of the panel with the underlay edge of the starting adapter. The second panel, position 2, should be held at a 45-degree angle to panel 1, and the female connector should be engaged over the male connector overlap edges of the run. Note that panel 2 is a half panel and that half panels are used to begin alternate rows at the starting adapter to provide a staggered end-joint pattern. A row that starts with a half panel will finish with a half panel. This pattern eliminates a continuous transverse joint across the runway, thereby reducing the bow wave effect.

Subsequent panels in the first row (3, 7, and so on) should be placed in a similar manner as the first panel. This first row of panels can be continued down the length of the runway unimpaired, but alignment must be insured and maintenance adapters must be put in place as required. The panels in the second and successive runs should be connected in the same manner as panel 2 and placed right to left in sequence 4, 5, 6, 8, 9, 10, and so on. This pattern will create a stair-step fashion for maximum placement efficiency. Once a mat has been laid, a lock bar must be inserted into the overlap/underlap connector slot. The panel must be locked together before the next panel of the adjacent row is placed because this operation will be impossible after another row of mat has been laid. The locking bars may stick due to material waviness in the mat panels or unevenness in the subgrade, and it may be required to lift a corner of the mat or to jump on the mat while sliding in the bar. This will help to align the locking bar slots to aid in bar insertion. It may also be required to apply a few light taps with a hammer to drive the bars into their proper positions (Figure N-43).

The mats are designed with an apparent loose fit to allow for expansion and also to allow for the natural waviness of individual mats. If misalignment of mat rows occurs from this or any other cause, the mat can be aligned by using bars and sledgehammers or wooden mallets. Always place a wooden block against the mat edge to act as a cushion when using a sledgehammer. Care should be taken to strike only the wooden block and not the mat (Figure N-44). Sledgehammer blows directly against the mat edges can deform the edges and make it impossible to connect the next row of mats.

The alignment of the mat may also be lost due to the play of the panels. Alignment should be checked periodically during the placement, and if alignment is off, work should cease and the mat brought back into alignment. This can be accomplished by using vehicles to pull the mat back into alignment.

After four or five runs of mats have been placed in one direction from the starting adapter and proper airfield alignment is assured, a second crew can begin placement in the opposite direction using the same placement procedure as the first direction.

Field access adapters are metal-alloy bars that have an overlap and underlap side placed between panels to allow access into the airfield and to replace panels without taking the entire airfield apart. They are installed in the staggered transverse joints between mats to form a V-shaped line or chevron pattern. The adapters are started every 150 feet and will continue back until the midpoint of the airfield is reached, and then the placement will move forward forming the V-shape (Figures N-45 and N-46).

ANCHORAGE OF MAT

Side Anchors (Figure N-47).

After the mat has been laid in the proper position, two to four rows from the starting adapter across the entire width of the installation of earth anchors should begin. These will hold the runway down and prevent lateral slippage. The anchors and attachments should be placed a maximum of 8 feet apart at panel joints on each side of the runway and alternated on each side of the runway so that no two anchors are directly opposite each other (Figure N-48). The 24-inch-long anchor should be screwed into the ground and secured in the anchor attachment slot (Figure N-49).

The following steps should be used in the placement of anchors and anchor attachments:

1. An anchor attachment is placed in position on the edge of the mat. The point of the anchor is then placed in its proper position in the slot of the anchor attachment.

2. The attachment is then removed, and the anchor is screwed into the earth. A power tool equipped for this purpose may be used for ease of operation.

3. After the anchor has been screwed about 12 inches into the soil, the anchor attachment is reinstalled, and the anchor is screwed until it seats itself in the attachment.

Ends of Runway

When the end of the runway is reached, two full rows of panels are buried to anchor the runway by using the 15 turndown adapter (Figure N-50). Burying is accomplished by removing enough soil to allow the last two panels of mat in each row to fall in an inclined plane a distance of approximately 18 to 26 inches below the normal ground level. The excavation should be large enough at the ends to allow for mat movement. This will allow the mats to expand without buckling or causing a hump in the mat field. The ground surface should be shaped to provide full soil contact across the bottoms of the anchoring panels. The 15-degree turndown adapter should be used with a locking bar to attach the runway to the anchoring panels, with one locking bar required for each adapter. After the anchoring panels have been placed, the excavation should be backfilled to normal ground level and compacted.

Ends of Pads

Anchors will be used and placed along the edges of mat, such as the taxiway or parking aprons, in the same patterns as for the sides of the runway as discussed earlier. These are not required for the runway since the runway ends will be buried.

Turn Adapters

In the M19 mat set, there are various ancillaries (Figure N-51) that provide for a wide range of runway and taxiway combinations in rapid airfield construction. As the mat field progresses, turn adapters are used to make changes in the lay of the mat as may be desired. The following examples show areas in which the various adapters are used:

  • Male/underlap turn adapters are used to start a lay from female roll-in edge of another lay. A locking bar is used to secure the underlap side of the adapter to the overlap edge of the mat in the second lay.
  • The male/overlap turn adapters can be used to attach the female edges of a row of mats to the underlap drop-in edges of previously laid mats. A locking bar is required to attach the adapters to the underlap edges of the first lay.
  • Female/underlap adapters are used for attachment of an intersecting runway or taxiway to a male edge of the runway. These adapters are installed in the same manner as the male/underlap adapters.
  • The H-connector is used to make transitions between M19 and AM-2 mats. Mixing of mat types should not occur on the runway. The H-connector can also be used to extend existing runways or to add taxiways at 90 degrees to the existing runways.

M19 MAT REPAIR

Mat removal may be required for repair of the subgrade, for replacement of damaged mats, or for replacement due to marginal conditions that warrant preventive maintenance. If the damaged area is close to the field access adapters or if an extensive area is to be replaced, access can be gained through these adapters. If damage to a single mat is in an area some distance from the field access adapters, repair mats can be used as replacements for damaged mats.

Mat Removal Through Field Access Adapters and Replacement

Field access adapters have an overlap and underlap side, and only mats on the overlap side of the field access adapters can be removed by the method described below:

  • Remove the anchors and anchor attachments as required.
  • Remove the locking bars from the access adapter at the edge of the field.
  • Slide the adapter from position, using a sharp, pointed tool inserted into the hole in the end of the adapter to aid in removal.
  • Remove the locking bar from the opposite overlap/underlap connector.
  • Remove the panel.
  • Remove the next adapter and mat.
  • Repeat this procedure as required until a series of mats can be removed with or without removal of additional adapters to reach damaged area.

After the damaged area has been repaired, the mats and adapters should be replaced as follows:

  • Replace the mats in the reverse pattern of that used in removal.
  • Install the field access adapters in their original positions as mat laying progresses and insert the locking bars.
  • Install any anchors and anchor attachments that may have been removed.

Removal of Isolated Mat(s) and Installation of Repair Mat

The following steps outline the procedures used to cut a mat in order that a single failed panel can be removed without requiring access through field access adapters. When a mat is removed by this method, a repair mat is installed in its place.

  • Cut the mat with a portable saw as shown in Figure N-52. Use a saw with a carbide-tip blade, lubricated to prevent chips from sticking to the blade. Make the first cut on the overlap edge of the mat along line 1, with the saw blade set to make a cut 1 1/16 inches deep, located 13/16 inch from the edge of the rail flange. A guide, such as a strip of plywood, should be used to obtain an accurate cut. If cut deviates towards the edge, the blade may become jammed when it contacts the loose locking bar in the joint. If the cut deviates from the edge, the locking-bar pocket will not be exposed, resulting in additional work to remove the bar. Be sure not to cut into adjacent mats.
  • Make the second cut along line 2 (Figure N-52). Set the saw to cut 7/8 inch deep, with the blade at a 30-degree angle. Start the cut 1/4 inch from the edge of the upper surface of the mat. With this setup, the saw will penetrate the locking-bar cavity and permit the lower lip of the underlap rail to be rolled out of its groove.
  • Set the saw to a depth of 1 1/2 inches, with the blade at an angle of 30 degrees. Cut through the mat along lines 3 and 4 (Figure N-52).
  • Pry up the triangular section, the section that contains the female connector and the triangular section adjacent to cut 2. It will be necessary to break some of the material at the ends of the cuts.
  • Pry the remaining two triangular sections out of the male hinge connection and overlap joints.
  • Pry out the locking bars and flanges of the drop-in joints with a small pry bar.

The following steps should be used for the installation of M19 repair mats:

  • The repair mat section incorporating the underlap edges should be installed first, as illustrated in Figure N-53. Engage the male edge of the mat with the female edge at the edge of the opening, and lower the mat to the ground. The side underlap rail of the repair mat will not be engaged. To engage this joint, lift the adjacent mats 3 inches off the ground with a pry bar and a suitable block at the corner where the two underlap rails of the repair panel intersect. While the adjacent mats arc elevated, slide the repair mat section under the matching underlap rail, then lower the adjacent mats.
  • To install the remaining part of the repair panel, engage the female and male hinge connectors, then lower the panel to engage the overlap and underlap connectors. To lock the mat into position, first loosen the nine socket-head set screws one-half turn. Shift the locking bars into the locked position with the aid of the pointed end of a small pry bar, working through the 3/8-inch-diameter access holes adjacent to the set screws. Tighten the set screws approximately five turns to hold the locking bars in a locked position.

REPAIR OF ANTISKID SURFACE

The antiskid coating can be easily replaced in the field with an ordinary paint brush or roller if care is taken to prevent segregation of the abrasive particles within the binder during application. Follow the sequence described below.

1. Clean the mat surface with a cloth saturated with toluene or an equivalent solvent.

2. Recoat the bare areas with a suitable antiskid coating, agitating the antiskid material periodically.

REMOVING, CLEANING, AND BUNDLING PANELS FOR REUSE

When the airfield is no longer needed, M19 panels can be removed, cleaned, and bundled for reuse at another location. When the mat field is removed, care should be taken not to break or bend the locking bars or damage the mat or any of the ancillary equipment. Upon removal, individual panels should be visually inspected in detail to determine the extent of damage, if any, that has occurred as a result of prior use.

Mat Removal

Panels should be removed from the two outside rows on the runway end where the last panels were placed. A locking bar should be removed by first engaging the hole in the bar with a hook or a sharp, pointed bar and then applying force. Vise-grip pliers can be used to grip the bar and pull it out. The panel can then be raised to an angle of about 45 degrees. The hinge connector will then disengage, and the panel will be free for removal. Next, the adjacent panel in the same row should be removed in the same manner.

Mat removal can also begin wherever access adapters are located in the mat field by first removing the adapters then the panels.

Cleaning

The connecting and locking features must be free of excess soil. Soil should be removed from the surface of the panels with a hoe, square-end shovel, or similar tool. Connecting and locking edges can be cleaned with a locking bar or a pointed tool, but they may require washing with water under pressure.

Bundling

Bundles should be about the same size as those of the original shipment. Half, full, and repair panels should be bundled separately. Each bundle should be tightly strapped with four straps, two over each edge. The straps should be spaced at the quarter points and placed over 2x4s used as skids to facilitate handling.

Criteria for Determining if M19 Mat is Reusable

Panels will be considered reusable if they will fit together at the sides and ends with a new panel. The panel should not have any tears or breaks that present a tire hazard. Panels with core failure that are permanently deformed more than 0.6 inch when measured across the transverse direction are considered unsuitable for reuse.

M19 SPECIAL SURFACING LANDING MAT

In the TO environment, it is likely that an expedient airfield using matting may require the use of an arrester system. Therefore, it has been determined that an additional requirement for medium-duty matting is that it be able to sustain two aircraft arresting hook impacts in the same spot and withstand 20 rollovers of an F-4C aircraft loading on the 1-inch-diameter hook arresting cable without structural failure due to the rupture of the top surface of the mat. Standard M19 mat did not meet the requirement, so an M19 special surfacing landing mat was developed for use where these types of operations may occur.

M19 Special Surfacing Mat Placement

Figure N-54 shows the pattern for placement of M19 special surfacing mat within a standard M19 mat field. After laying the standard M19 mat from the M19 starter to the critical area, it is desirable that the special surfacing panels be placed in the order indicated by the panel numbers shown.

At the junction of the two types of mats, an overlap/D1 adapter should be placed on each row of standard mats (Figure N-54, Section A-A). The adapter to the standard mat is secured with a standard lock bar. Panel 1 of the special surfacing mat should then be placed in alignment and flush with the overlap/D1 adapter. The lock bar for the D1 connector (Figure N-55) is then inserted to lock the adapter and the special surfacing mat together. Subsequent panels in the first row (panels 2, 5, 10, and so on) are placed in a similar manner. The panels in successive rows are placed in a stair-step pattern beginning at the first row (note sequence of panel numbers in Figure N-54). The panels are held at a 45-degree angle to the ground to engage the female connector over the male connector of panels in the previous row. The panel is then dropped to the ground with the D1 connector flush with panels already in place. The D1 lock bar is then inserted to secure the panels.

The installation of lock bars, tight and loose spacing of panels, subsequent adjustments, and the installation of side anchors is similar to the procedures for standard mat.

It is anticipated that the standard M19 panels will be placed from the critical area to the end of the runway. At the junction of special surfacing mat and standard mat, a D1/underlap adapter (Figure N-54, Section B-B) will be required. The standard placement pattern and methods will then be continued to the end of the runway.

It is not anticipated that turns or taxiways will be adjacent to the M19 special surfacing. However, should the need exist for such configurations, the standard 90-degree turn adapters (male/overlap, male/underlap, female/overlap, and female/underlap) can be used since the male and female connectors of the M19 special surfacing mat and the standard M19 panels are interchangeable. (It is assumed that only standard M19 mats will be used in the turns and taxiways and not M19 special surfacing mat.)

Mat Removal

It should be noted that access-type adapters are not required with the special surfacing because of the transverse joint configuration. This configuration allows panels to be removed from both edges of the runway after the D1 lock bars are removed. By using a pyramid removal pattern, any M19 special surfacing panel(s) in the interior of the runway can be removed and replaced from either edge of the runway, without any undue effort or damage to panels. After bars are removed, a panel can be hinged out by raising it to about a 45-degree angle with the ground and disengaging the male/female connection. The outer rows of the mat should be removed first, and adjacent rows should be removed as the D1 lock bars are exposed and removed.

Maintenance and Repair

All methods of evaluation and maintenance, such as repair of antiskid surface, cleaning, and rebundling panels for reuse, and determination of mat reusability, are the same as standard M19 unless stated differently in the above section.

TRUSS-WEB, HEAVY-DUTY MAT

The truss-web mat panel is a one-piece, extruded section with extruded end connectors welded to each end (Figure N-56). The side connectors are integral parts of the basic extrusion. The basic section is partially hollow. The panel is approximately 1 1/2 inches thick, 2 feet wide, and 9 feet long and comprises 18 square feet of placing area. Half panels are 2 feet wide and 4 1/2 feet long. The truss-web mat, fabricated from aluminum alloy, weighs 6.3 pounds per square foot. This mat is painted Marine Corps Green, Number 23, and the top surface is coated with antiskid material of the same color.

The side connectors (female and male) are constructed to interlock with a rotating motion. The end connectors are symmetrical I-lock connectors. The end connectors of adjacent panels are locked together by a locking bar, which is inserted into the slot formed by the two end connectors (Figure N-57).

One locking bar per panel of mat is included in each mat bundle. The truss-web mat is laid with the male-female joint perpendicular to the direction of traffic.

Ancillary Items

Descriptions of the various ancillary items used in conjunction with the truss-web landing mat are as follows:

Starting connector. A starting connector is a small, extruded aluminum-alloy section with a male connector on each side (Figure N-58). This connector is approximately 3 inches wide, 1 1/2 inches thick, and 108 inches long. The starting connectors are used to form a transverse line across a runway or taxiway from which mat laying is started. The use of these starting connectors permits the number of laying crews to be doubled since two crews can begin placing mat in opposite directions from the connector toward each end of the runway or taxiway.

Access adapter. An access adapter is a small, extruded aluminum-alloy section with a female connector on one side and a male connector on the other side (Figure N-59). This adapter is approximately 2 1/2 inches wide, 1 1/2 inches thick, and 108 inches long. A hole is provided near each end for use in sliding the connector out of the mat field. The adapters are placed every 100 feet in the runway and taxiway to permit nondestructive removal and reinstallation of mats in order that damaged mat panels can be replaced or the subgrade can be reprocessed.

Turn adapters. A turn adapter is a small, extruded aluminum-alloy male or female I-lock connector (Figure N-60). These adapters are approximately 1 3/4 inches wide, 1 1/2 inches thick, and 24 inches long. The adapters are used to make 90-degree turns from a runway to a cross taxiway or to connect a taxiway to a parallel taxiway. Through use of these adapters, the mat on a cross taxiway can always be laid in such a way that aircraft traffic is applied on the mat perpendicular to the internal ribs, as it is on the runway.

Two-foot locking bars are used with these adapters to make a positive connection with the mat. H-adapters can also be used to construct 90-degree turns. Although this adapter does not provide a positive connection between the mats, it can be used to construct 90-degree turns or connections between different types of mat where the other connectors are not compatible. H-sections can be used to allow slight misalignment between the adjoining sections of mat. These adapters are 6 inches wide, 2 1/4 inches thick, and 144 inches long.

Anchor attachment. An anchor attachment connects to the edges of a mat-surfaced runway or taxiway and is used to secure the edge anchor to the mat along the edges. The type used to secure the edge anchor to the truss-web mat is an I-lock attachment (see Figure N-61).

Edge anchor. Edge anchors (Figure N-61) are used in conjunction with anchor attachments to secure the perimeter of the mat. The anchor, fabricated from carbon steel, is approximately 26 inches long. The helix, which is 4 inches in diameter, is attached to a 3/4-inch-diameter shaft. The head of the anchor has a 1-inch-diameter hole through it and a flange surface to aid in installation. One anchor per attachment is required along the runway and taxiway edges.

Repair panel. A repair panel is a special panel that is used to replace a single, damaged mat panel within a mat field without removing adjacent panels. The outside dimensions of the panel are the same as those of the basic section of a full panel, but other features are different. The repair panel is heavier than the standard trussweb mat panel. The female connector is similar to the female connector on a standard panel. The male and I-lock connectors consist of several parts separate from the repair mat extrusion (Figure N-62). These parts are placed before placement of the main body of the repair panel. The panel is then put into place, and the parts connected to the main body with cap screws, thus completing the panel.

Installation Instructions

No special skill is required for emplacement of truss-web landing mat once a well-prepared subgrade has been constructed and a baseline has been established.

On a flat subgrade, the mat can be placed in a normal brickwork pattern (Figure N-63) at the rate of 748 square feet per man-hour. The ends of alternate runs are offset by a minimum of 2 inches so the locking bars that connect the anchor attachments to the ends of the mat panels can be installed after the mat has been placed.

On a subgrade crowned as much as 3 percent, mat panels can be placed in the 1-foot offset pattern shown in Figure N-63 at a field rate of 200 square feet per man-hour. When the mat is installed over the crown, the emplacement mat normally has to be raised to reduce the curvature in order to place the panels that bridge the centerline. Therefore, additional time and effort are required, and the installation rate achieved is lower than that achieved when the subgrade contains little or no crown.

A basic mat-placing crew consists of seven men--one NCO and six enlisted men. As many as four crews can lay mats in one direction as work progresses on the runway.

The general procedure for installing mats on a runway, taxiway, or apron is for placing crews to start at the transverse centerline and lay mats toward each end, simultaneously. Baselines established on each side of the section should be used for mat alignment. The baseline and transverse centerline should be clearly marked with stakes or by other means before mat laying. The starting connectors are laid at the transverse centerline, and then individual mats are laid in a brickwork/stair-step pattern or in a 1-foot offset pattern from left to right when facing the starting connector (see arrows in Figure N-64). The coated side (the side with antiskid material) is placed up. Other sections of the airfield installation can be placed in the same manner and at the same time if baselines have been established, proper alignment of these sections with the runway has been made, mat bundle deployment has been accomplished, and sufficient personnel are available to accomplish the multiple crew mat placement. A run of access adapters should be laid every 100 feet. These adapters are placed in the runway and taxiways to permit nondestructive removal and reinstallation of mats in order that damaged mat panels can be replaced or the subgrade can be repaired. Details of installation are given in the following paragraphs:

Mat Laying Procedure

Brickwork pattern. The starting connectors are laid on the transverse centerline of the runway (Figure N-64). As the starting connectors are placed, they are butted together. After the starting connectors have been placed and aligned, the first mat is placed. On the left side of the runway (facing the starting connector), the first mat panel (a half panel) is aligned with the connector. The female connector is placed over the male connector of the starting connector. For proper engagement of the panel with the starting connector, the panel should be held at an angle approximately 45 degrees to the subgrade. With the top flange of the female connector of the panel engaged over the top of the male connector on the starting connector, the panel is rotated downward to form a joint. The next mat (a full panel) is placed to the right of the first mat. The second mat (a full panel) is placed in the same manner as the first. Once the I-lock connectors of the first and the second mats have been aligned, a locking bar is inserted (Figure N-65) to prevent the mats from separating. Because the bar might be tight in the locking bar slot, a hammer may be required for insertion. The tight condition may be due to waviness of the end connectors or locking bars, or to soil or debris in the connectors.

The third mat (a full panel) can be placed in the second run onto the first two mat panels that have been laid (Figure N-64). This mat is offset from the half panel (panel 1) in the first run by 2 inches so that the locking bar for the anchor attachment can be installed after the mat is placed. The brickwork/stair-step pattern can be continued across the runway, allowing more placement crews to work and more mat to be placed in a given amount of time.

The last panel placed in the first run will be a half panel, and the first panel placed in the second run will be a full panel. The first run of panels and each alternate run are laid using half panels at the outer edges and full panels in between. Only full panels are laid in the second run and each alternate run thereafter, and these runs are offset from the adjacent runs by a minimum of 2 inches so the locking bars for the anchor attachments can be installed anytime after the mat is placed. This method allows the end joints in adjacent runs to be staggered for greater mat strength.

After several runs have been placed in one direction and proper alignment has been maintained, placement of the mat can be started in the opposite direction. The procedure for mat placement on the opposite side of the connector is the same as that for placement on the initial side except that the first panel placed is a full panel. All panels in the first run are full panels. Alternate runs thereafter will contain only full panels. The first and last panels in the second run are half panels with full panels in between. Alternate runs thereafter will contain half panels at the outer edges with full panels in between. These runs are offset from the adjacent runs by a minimum of 2 inches so the locking bars for the anchor attachments can be installed anytime after the mat has been placed.

Care should be taken to ensure that alignment with the transverse centerline and with the runway edge is maintained for the first several runs. Then alignment should be maintained with the runway edges as more mat is placed. Any misalignment will cause a displacement of the runway from the planned position at each end of the field.

The truss-web mat panels are designed and fabricated so that when they are placed, there is an apparent loose fit. This allows for mat expansion and for the natural waviness inherent in extruded mat panels, which makes it possible to place a run of mats so misaligned that they prevent the proper engagement of one or more of the mat panels in the following run. The method of correcting misalignment is shown in Figure N-66. Misalignment must be corrected to prevent a zigzag pattern of the mat at the runway edge, which would cause misalignment with the baseline. The runway edge has to be straight at the point where a taxiway is to be laid off the runway in order that the turn adapter will properly engage the mat on the runway. In the area of the runway where the taxiway is to be tied into the runway, the mat panels are not offset. At the ends of the runs opposite the taxiway, locking bars that have been cut in half are installed in alternate runs as the mat is placed. These bars are installed as the mat is placed so that the anchor attachments and anchors can be placed at a later time. If it is necessary to use a sledgehammer to align the mat, a wooden block should be placed against the mat edge to prevent damage to the panel. After the mat panels have been aligned, the locking bar can be inserted into the locking-bar slot.

One-foot offset pattern. The starting connectors are laid on the transverse centerline of the runway (Figure N-64). As the starting connectors are placed, they are butted together. After the starting connectors have been placed and aligned, the first mat is placed. The first mat panel (a full panel is aligned with the connector of the starting connector on the left side of the runway. For proper engagement of the panel with the starting connector, the panel should be held at approximately a 45-degree angle to the subgrade. With the top flange of the female connector of the panel engaged over the top of the male connector on the starting connector, the panel is rotated downward to form a joint. The next mat (a full panel) is placed to the right of the first mat. The second mat is placed in the same manner as the first. Once the I-lock connectors of the first and the second mats have been aligned, a locking bar is inserted (Figure N-65) to prevent the mats from separating. Because the bar might be tight in the locking bar slot, a hammer may be required for insertion. The tight condition may be due to waviness of the end connectors or locking bars or to soil or debris in the connectors.

The third mat (a half panel) can be placed in the second run onto the first two mat panels that have been laid. This mat is offset from the first full panel in the first run (panel 1) by 1 foot. The fourth mat (a full panel) can be placed adjacent to panel 3 in the second run. Panels 3 and 4 can be connected at the ends with a locking bar. This stair-step pattern can be continued across the runway, allowing more placement crews to work and more mats to be placed in a given amount of time.

The sixth panel placed in runs 1, 3, 5, and so on is a half panel; five full panels are then placed with these runs ending with half panels. The seventh panel placed in runs 2, 4, 6, and so on is a half panel; five full panels are then placed with these runs ending with full panels. The half panels are placed near the center of the runway crown to allow easier mat placement.

After several runs have been placed in one direction and proper alignment has been maintained, placement of the mat can be started in the opposite direction. The procedure for mat placement on the opposite side of the starting connector is the same as that for placement on the initial side. Care should be taken to ensure that alignment with the transverse centerline and with the runway edge is maintained for the first several runs. Then alignment should be maintained with the runway edges as more mat is placed. Any misalignment will cause a displacement of the runway from the planned position at each end of the field. The procedure for correcting any misalignment is the same as for the brickwork pattern. On the area of the runway where the taxiway is to be tied into the runway, the mat panels are to be placed in the brickwork pattern and these panels are not offset at the edges.

Anchorage of Mats

Edge anchors. Anchor attachments and edge anchors are placed every 4 feet along the edges of runways and taxiways. The anchors are placed at the center of the mat panel. However, they are not placed opposite each other on the edges but are staggered 2 feet apart (Figure N-67). A full-length locking bar can be used with the anchor attachment at the ends of the panels where the anchors are to be placed. The full-length bars are used in the ends of the mat runs that are offset either by 2 inches or 1 foot. These anchors and attachments can be placed anytime after the mat has been placed. Along the edge of the mat in the runway opposite the edge where a taxiway ties into the runway, locking bars that have been cut in half are used to connect the anchor attachment to the mat. One of these half bars is inserted in the panel at the end of the run that requires an anchor.

These bars are installed as the mat is placed since this edge of the runway may end in such a manner that the bars cannot be inserted in the I-lock connector at the runway edge after the mat has been placed. This allows placement of the anchor and anchor attachment anytime after the mat has been placed. When the anchor is placed, it should be completely driven until the anchor head is tight against the anchor attachment.

Ends of runway. In order to anchor the mat at the ends of a runway, a trench is excavated across the entire width of the runway to contain five or six runs of mat (Figure N-68). The trench should slope away from the end of the runway and at the deepest point should be 24 to 30 inches below the level of the end of the runway. The surface of the trench should be shaped to provide full contact with the bottom of the mat. Five or six runs should be laid in the trench in the normal brickwork/stair-step pattern. The trench should then be backfilled and compacted.

Field Access Adapters

A run of access adapters is placed every 100 feet in a runway or parallel taxiway. The first access adapter is aligned with the outer edge of the preceding run of mat. The female edge of the adapter is engaged with the male edge of the preceding run of mat. Once the engagement is made, the adapter is rotated downward. The remaining adapters in the run are placed in a similar manner. Adjacent access adapters are butted. After the adapters have been placed, laying of the mat is continued in the brickwork/stair-step pattern described in previous paragraphs.

Turn Adapters

A typical airfield installation is shown in Figure N-69. Section A-A shows the starter connectors, which are used in the runway and in the parallel taxiway. Placement of mat from these starter connectors has been described previously. The various junctures formed between the runway, cross taxiways, and parallel taxiways are shown in Figure N-69. Turn adapters used to make the various junctures allow the mat to be positively locked together. As the mat is placed and the juncture areas are approached, care should be taken to ensure that the mat is aligned with the baseline. This is necessary so that the turn adapters will properly connect and the mat on the taxiways can be placed off or on the turn adapters to complete the positive connections. Two-foot-long locking bars are furnished with the turn adapters.

An alternate connector that can be used at the juncture of two facilities is the H-section adapter (Figure N-69, part d). H-sections are generally used to connect different types of mat or to allow for slight misalignment between the adjoining sections of mat and can be installed by either of two methods.

In the first method, the mat is placed on the runway, and then the taxiway mat is laid from the runway at the desired location. In this method, the H-sections are installed on the mat in the runway. As the mat in the first run is placed for the taxiway, each panel is slid into the H-section. After the first panel has been placed in the H-section, the second panel is slid into the H-section. The locking bar between the first and second panels can then be installed. This sequence is used for all the mat placed in the first run. The remainder of the mat to be placed in the taxiway is placed in the brickwork/stair-step pattern as previously described.

The second method that can be used to make the transition between a runway and taxiway with the H-sections is shown in Figure N-70. The runway and cross taxiway are placed simultaneously and should be placed so they come to within 1 to 2 inches of each other. This distance has to be carefully controlled so that when the H-section is installed, it will connect the mats effectively. It is suggested that the transverse midpoint of the taxiway be established and the H-sections be installed in each direction from the midpoint. An H-section is placed along the edge of the runway mat. The section is then driven between the runway and taxiway mat with a sledgehammer. A wooden block should be placed against the section to prevent damage. Power equipment such as a forklift or motor patrol can also be used to force the section into place. H-sections can also be used to connect a cross taxiway and parallel taxiway by either of the two methods described above.

Heavy-Duty, Truss-Web Mat Repair

It may be necessary to remove mat due to damage to an individual panel or several panels and/or to repair the subgrade beneath the mat at an existing facility. When individual panels of truss-web mat need to be replaced, they can be cut out and replaced with repair mat assemblies. When several panels or runs of panels need to be removed, the access adapters near the mat that is to be taken out are removed, or a run of mat close to the mat that is to be removed is slid out. The procedures for the two methods of replacement are given in the following paragraphs:

Method 1: Isolated Mat Replacement. As noted earlier, a repair panel is used when it is desired to replace a damaged panel without removing any of the surrounding panels. Tools that can be used in making the individual mat replacement include a power saw, pry bars, a chisel, a 5/16-inch allen wrench, an adjustable wrench, and a hammer. Removal can be accomplished by sawing the damaged panel and removing it in sections (Figure N-71). The damaged panel should be cut with a power saw in the sequence shown in Figure N-71. The depth of the cuts and positioning of the saw are shown in Figure N-71. The saw blade should be carbide-tipped for best results. A lubricant added to the saw blade will aid in preventing the chips from sticking. Care should be taken not to cut into the adjacent mat panels and locking bars that will remain engaged with the undamaged panels adjacent to each end of the panel that is to be replaced. It will be necessary to break some of the material at the ends of the cuts, as the cuts will not go completely through the panel that is to be removed. This can be done with a pry bar and/or chisel. After all cuts are made, the small triangular sections (shaded area in Figure N-71) are removed initially to provide access to the larger sections in the removal operation. Then the material at the ends of the cuts is broken. A pry bar should be used to force up section A. This part can then be unhinged and removed. Then section B should be forced up, unhinged, and removed. Prying up section E will help to break off section C, if section C has not already been separated from the rest of the damaged panel. Section C is removed and the adjacent panels can be lifted slightly so that section E can be removed easily. This procedure is repeated for sections D and F. Once all parts of the damaged panel have been removed, all soil or debris that may have collected in the surrounding mat panel connectors and any debris in the area where the repair panel is to be placed should be removed.

The procedure listed should then be followed in the installation of the repair panel (Figure N-72).

  • Disassemble the repair panel by removing the 1/2-13UNC (unified coarse thread screw, 1/2 inch long, with 13 threads per inch) with 1 1/2-inch-long socket-head cap screws from the male connector clamp and by removing the upper-end connector clamps at each end of the panel with a 5/16-inch socket-head wrench.
  • Position one lower-end connector clamp so that it engages the locking bar that is locked to section A, and one lower-end connector clamp so that it engages the locking bar that is locked to section D.
  • To simplify positioning of loose pieces so that the socket-head cap screws can be conveniently installed in the proper sequence, screw one of the threaded locating pins (Figure N-73) four or five turns into the end-threaded hole of the lower-end connector clamp that is nearest sections B and C. Also, screw one threaded locating pin four or five turns into the center hole of each lower end connector clamp. (If these locating pins are not available, a round punch may be used to make the alignment: however, care must be taken not to damage the threads in the male connectors and the lower-end connector clamps.)
  • Position the repair panel male connector on the subgrade so that it engages the female connectors of sections B and C so that the end holes fit over the locating pins that have been temporarily screwed into the end holes in the lowerend connector clamps.
  • Hook the female connector of the repair panel over the male connectors of sections E and F and lower into position over the locating pins in the lower-end connector clamps.
  • With the aid provided by the locating pins, position an end-connector upper clamp at each end of the repair panel. Install socket cap screws in all open holes in the end connector and tighten four or five turns.
  • Taking care not to disturb any of the repair mat pieces, remove the locating pins at the ends of the end connectors one at a time and replace them with socket-head cap screws.
  • Remove locating pins at the center of the end connectors and replace with socket-head cap screws.
  • Position the male connector clamp over the repair-mat male connector and over the repair panel. Insert the socket-head cap screws in each hole and tighten gently.
  • Tighten each screw in the repair mat assembly.

Method 2: Mat Replacement by Removing Access Adapters. When it is necessary to remove one or many panels to replace damaged mats or to repair the subgrade, mat removal and replacement can be accomplished by sliding out an adjacent run of either access adapters or mat panels. The methods used to remove the access adapters or a run of panels are described in the following paragraphs:

  • Access adapter removal method. With a tooth of the scarifier on a motor grader or other power equipment, engage the end of the access adapter and push out the entire run of adapters. If a binding condition exists, it may be necessary to slide out only one or two adapters at a time. The binding condition may be caused by distortion of adjacent mat and/or the access adapters or by debris that has migrated into the connectors. A light application of oil poured along the sliding joints will assist in removal.

Once the access adapters have been removed, the first run of mat panels that is to be removed must be raised high enough to slide out the locking bars. This can be done with blocking and pry bars. It is necessary to raise this run of mat panels only high enough to slide the locking bars out over the adjacent parallel run of mat on the runway. The bars can be removed by inserting a piece of wire or a sharp, pointed instrument into the locking bar holes and pulling the bars out.

The remaining mat panels that must be removed in order to gain access to the damaged area are then taken up. If necessary, the subgrade is repaired. The mat is replaced in the manner previously described for mat placement until the run is in place. The mat in the last run must be raised with pry bars to permit the installation of the locking bars. The access adapters are then replaced in reverse order from which they were taken out.

  • Mat panel removal method. A run of mat near the area where repair or replacement is necessary can be removed in the manner described for removal of a run of access adapters. As the panels are slid out, the locking bars are removed. A light application of oil along the sliding joints will assist in the removal. Once this run of the mat has been removed, the rest of the mat panels that must be taken up in order to gain access to the damaged area can be removed. After the repair has been completed, the mat is replaced in the manner previously described for mat placement until the last run is replaced. At this point, the mat in the last run is slid back into the runway with the aid of power equipment. As the panels are slid back into position, the ends of adjacent panels are connected with locking bars.

Replacement of Antiskid Coating

Replacement of antiskid coating on the truss-web mat is necessary when the original coating has been removed, loosened, or charred regardless of cause. The antiskid coating should be applied as follows:

  • Before application of the antiskid coating, all loose coating should be removed by brushing the surface of the mat thoroughly with a stiff-bristled brush. All loose matter should be removed from the brushed area by wiping thoroughly with a clean, lint-free rag or by sweeping with a clean broom. Any grease or oil should be removed with denatured alcohol (specification MIL-A-9061C) applied with a clean, lint-free rag. The alcohol should be confined to the metal surface to be cleaned and must not contact any undamaged antiskid coating.
  • The application of the antiskid coating should not be started or completed if (1) the ambient temperature is under 40F, (2) the area to be coated is wet, or (3) rain or snow is expected to fall within 24 hours after the start of the repair. A dry period of 24 hours is necessary before the recoated mat can be used. Any rain or snow during this 24-hour period will necessitate the removal of the repair coating using methyl ethyl ketone (specification TT-M-261B) and the repetition of the repair procedure.
  • The antiskid compound should be thoroughly stirred before application and agitated periodically to ensure that the abrasive particles remain in suspension. The compound should be brushed, sprayed, or troweled on at a thickness of approximately 1/16 inch and allowed to cure for at least 24 hours before the repaired area is subjected to any kind of traffic.

Removing, Cleaning, and Bundling Panels for Reuse

When an airfield is no longer needed, the mats can be removed, cleaned, and bundled for reuse at another location. When the mat field is removed, care should be taken not to break or bend the locking bars or damage the mat or any of the ancillary items. Upon removal, individual panels should be examined in detail to determine the extent of damage, if any, that has occurred as a result of prior use.

Mat removal. The anchors and anchor attachments should be detached prior to mat removal. The most efficient removal procedure requires disassembly of the mat in reverse order of placement. However, in order to expedite the operation, an entire run of mat or a run of access adapters can be slid out in several places, and at each location, two crews can take up the mat in the opposite order of placement, but the other crew would have to hinge the male connectors out of the female connectors, requiring more time and effort.

While the mat in the interior of a facility is being removed, a crew with earthmoving equipment can remove the backfill at the ends of the runway. Once the backfill has been removed, a crew can then begin removing the mat from each end of the runway toward the transverse centerline.

To remove a mat panel, first the locking bars should be removed by engaging the holes in the bars with a sharp, pointed instrument or wire and then pulling the bars out. Because of binding, it may be necessary to use vise-grip pliers in order to remove some of the bars. This binding may be caused by panel connector deformation and/or debris that has worked its way into the connectors. Once a bar has been removed, the panel can be raised. The side connection is hinged out when the panel is raised to about a 45-degree angle with the ground. The adjacent panel in the same run can be removed next in the same manner. After two or more panels in the same run have been removed, the end panel in the adjacent run can be removed. By continuing this procedure, a stair-step pattern is established during removal.

Cleaning. The connecting and locking features must be essentially free of soil. The soil can be removed from the panels with a hoe or a square-end shovel. Connecting and locking edges may require washing with water under high pressure.

Bundling. Bundles should be about the same size as those of the original shipment of mat and ancillary items. Half, full, and repair panels and the ancillary items should be bundled separately. Steel strapping should be used to secure the bundles.

Criteria for Determining if a Mat is Reusable

The following can be used as a general guide for determining whether the mat can be reused:

Panels will be considered reusable if they will fit together at the sides and ends with a new panel.

Reusable panels may not have any tears or breaks that will present a tire hazard. Panels with ribs that are permanently deformed more than 0.6 inch across the transverse direction are considered unserviceable.

Panels with weld failures at the end connectors are considered unserviceable and must be repaired if the failure is 6 inches long or longer or occurs in two places that together total 6 inches or more in length.



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