Air Force flies and fights from its air bases. However, it is at the air
base that air power is most vulnerable. They can be most immediate and
lucrative targets for an adversary. After all, it is by far more effective
to destroy aircraft while they are on the ground than to hunt them in the
air. From a practical perspective, it is reasonable to say that during some
phase of a conventional conflict, repair of airfield pavement damage will be
one of the civil engineer’s primary wartime missions. It is a complex and
difficult tasking that requires the total commitment of all involved to
succeed. Proper preparation must be accomplished prior to the moment of
need…for time will not be available during the conflict to accomplish
American military leaders recognized
the vital need for airfields to support operations in all theaters of
operation. This could mean repairing and maintaining existing airfields
quickly and at times close to the front as possible. To provide this level
of support, Aviation engineers experimented with several different runway
materials. For example the attempt to construct and repair airfields with
wooden planks proved too costly and labor intensive. Precast concrete was
another alternative but after extended testing it was too heavy and not
feasible. However, work continued and by the mid 1990’s
HQ Air Force Civil Engineering Support Agency (AFCESA) had perfected the
Folded Fiberglass Mat (FFM) System that is the primary method now employed
Air Force wide.
The Folded Fiberglass Mat (FFM)is the current Airfield Damage Repair (ADR) method used for Rapid
Runway Repair. The FFM is a 30 ft. by 54 ft
panel. Each FFM panel consist of 9 independent 6 foot by 30 foot composite
panels joined by rubber hinges. The NSN for this product is
5680-01-368-9032. Each FFM Kit consist of two 30 foot by 54 foot FFM’s and
two each 24 foot by 2 foot joining panels and two each 30 foot by 2 foot
After an attack the RRR team receives
its order to proceed to the repair location. The damaged is then assessed.
The upheaval and dunnage is removed. The bomb crater is back filled with
crushed stone and the FFM assembly is towed over the filled crater and
anchored to the airfield pavement. The FFM prevents the fill from becoming
foreign object debris (FOD) . Once in place the FFM makes for a virtually
flush pavement repair. The FFM’s have been tested to be effective for all
fighter jets and heavies up to the C-130.A detailed
description of the crater repair and FFM installation is described below.
Airfield Damage Repair partA: Filling the Crater
Crushed Stone Repair
(1) Clear debris from around the
crater at least 6 meters (20 feet) in all
directions to allow identification of
the upheaved pavement surface. Identification and removal of all upheaval or
damaged pavement is critical. It cannot be rolled down flush with the
existing pavement and left. The upheaved pavement will eventually break
up and create additional problems adjacent to the crater repair.
(2) Perform profile measurement and
visual inspection to identify and mark
upheaval around the crater.
(3) Remove upheaved pavement using an
excavator with bucket or moil
point attachment, and the front-end
loader. The dozer may also be used, depending on the runway surface.
(4) All debris material in excess of
304 millimeters (12 inches) must be
removed or reduced in size. Breaking
the pavement into smaller pieces will minimize the potential for voids and
settling problems in the future.
(5) Push unusable debris at least 9
meters (30 feet) off the Minimum Operating Strip (MOS) and pile no higher
than 0.9 meter (3 feet).
(6) Place backfill material into the
crater in accordance with the repair
procedure chosen. Note: If
settling problems are anticipated, placement of membrane fabric between
dissimilar backfill materials is recommended.
(7) Fill and compact the crater with
crushed stone material, placing it in lifts
approximately 152 to 177 millimeters
(6 to 7 inches) thick. For C-17 operations, limit the aggregate size to a
maximum of 25 millimeters (1 inch) in the top 152 millimeters (6 inches) of
the crushed stone repair. Overfill the crater by approximately 76
millimeters (3 inches) above the original pavement surface height. Compact
each lift of crushed stone using a minimum of four passesof a single drum vibratory roller or two passes
with a 10-ton vibratory roller. One
pass of the roller means traveling across and back in the same lane. If the
crushed stone material is placed upon soft subgrade materials, it may be
beneficial to separate the material using geomembrane fabric and place the
crushed stone material in thicker lifts. In any case, the crushed stone
compacted with a minimum of four
passesof a single drum vibratory roller or two passesof a 10-ton vibratory roller per each 152 millimeters (6 inches)
of thickness. A 457-millimeter (18-inch) crushed stone layer should receive
a minimum of 12 passeswith a single drum vibratory
roller or sixpasseswith a 10-ton vibratory
roller prior to cut for the final grade.
(8) Grade the compacted crushed stone
to approximately 25 millimeters (1
inch) above the pavement surface.
(9) Compact the crushed stone using
two passesof a single drum vibratory roller or
one passwith a 10-ton vibratory roller. The crushed stone
layer should have a minimum 15 CBR to support C-130 and fighter jet
(10) Perform profile measurement. The
repaired crater must not exceed the
maximum RQC of ± 19 millimeters (±
0.75 inch). A repair outside this tolerance may still be useable, depending
on its location, but will have a much shorter life before requiring
additional maintenance to bring it back within this limitation.
(11) The crushed stone repair is
complete at this point.
Airfiled Damage Repair part B:
Installing the FFM
Air Force FFM.
Force FFM is manufactured by ReadyMat US LLC Inc., 337-528-3443.
The FFM is
air-transportable, can be moved easily by vehicles, can be
positioned at greater distances from
airfield pavement surfaces, and can be stored indoors out of the elements.
A standard FFM weighs
about 1360 kilograms (3,000 pounds) and consists of nine fiberglass panels,
each 1.83 meters wide by 9.14 meters long by 12.7 millimeters thick (6 feet
wide by 30 feet long by 0.30 inch thick nominally). Elastomer hinges 76.2
millimeters (3 inches) wide connect the panels. When folded, these mats are
1.83 meters wide by 9.14 meters long and 203 to 254 millimeters thick (6
feet wide by 30 feet long and 8 to10 inches thick). This repair system also
includes joining panels and two support mat kits. The joining panels come in
7.32-meter and 9.14-meter (24-foot and 30-foot) lengths. One of each size is
needed to connect two 9.14-meter by 16.46-meter (30-foot by 54 -foot) mats.
The resulting 16.46-meter by 18.29-meter (54-foot by 60-foot) mat is the
normal size suitable for most crater repairs. If larger FOD covers are
required, additional mats may be spliced together. There are two types of
support mat kits for the FFM. Mat Kit A contains all the necessary tools and
hardware required to assemble, install, and maintain the system. Mat Kit B
contains the anchor bolts required to attach the mat to the pavement
(1) The mat assembly area can be any
area near the crater repair. This area must be cleared of all debris and
swept. It must be large enough to accommodate the unfolding of both mats,
allow equipment operations around the mat, and not interfere with crater
preparations. This area should be approximately 30.4 meters by 30.4meters
(100 feet by 100 feet) square, and located a minimum of 30.4 meters (100
feet) from the crater and off the MAOS.
(2) Mats are placed end-to-end about
1.2 meters (4 feet) apart, with the first panel up and positioned such that
both mats unfold in the same direction. Unfold the mats in preparation for
being joined together. The top panel of the mat is attached to a tow vehicle
with a nylon strap. A crew of four people, or a forklift positioned on
the opposite side of the mat, lifting each successive panel as the mat is
being pulled open, speeds the unfolding process.
(3)Join the mats together so they are
aligned, the 9.14-meter (30-foot) edges are even, and the 16.46-meter
(54-foot) edges are roughly parallel with each other. Lift one end of the
16.46-meter (54-foot) edge and slip either the 7.32-meter (24-foot) or the
9.14-meter (30-foot) section of joining panel underneath the raised edge.
Align the holes in the mat with the joining panel bushing holes and lower
the mat. Install the top joining bushings and tighten by hand. This process
is repeated at the other end of the 16.46-meter (54-foot) edge of the same
mat using the remaining joining panel. Hand-tighten these bushings; final
tightening will be accomplished later.The second mat is then towed over to
the first mat with joining panel attached. One of the holes near the end of
the second mat is aligned with its counterpart on the joining panel and a
top joining bushing is installed. This end connection acts as a pivot point
when the second mat is moved into position so all the remaining holes on the
joining panel are in alignment.
(4)Install the remaining top bushing
and tighten the entire second mat bushing with an impact wrench. Revert to
the first top joining bushings and tighten them with the impact wrench. All
joining bushings should be tightened and the joined mats are now ready to be
towed over the repaired crater.
(5)Before any towing operation can
commence, the area between the mat
assembly area and the repaired crater
must be completely swept. Any debris that is picked up under the mat as it
is being towed could damage the matting and affect the smoothness of the
When the width of the MAOS permits,
the mat should be towed parallel to and next to the crater. Align the
joining panel with the center of the crater. Use a front-end loader or
similar vehicle to tow the mat over the crater with the hinges perpendicular
to the tow direction. Position the mat so the hinges are parallel to the
direction of the MAOS traffic. The mat should not be more than 5 degrees off
(6) With the mat in position over the
crater, it must be anchored in place. Techniques for anchoring the FFM will
depend on the type of pavement surface. The FFMs are predrilled for
anchoring bolts. All three anchoring techniques use a 101.6-millimeter
(4-inch) bushing through which the bolt passes to hold down the mat.
Concrete Pavements. The concrete anchor is normally a rock bolt that is
127 to 152.4 millimeters long and 15.9
to 19.1 millimeters in diameter (5 to 6 inches long and 0.625 to 0.75 inch
in diameter). At each predrilled hole in the leading and trailing edges of
the mat, drill a hole into the pavement corresponding to the diameter of the
bolt being used. Position an anchor bushing in the predrilled hole as a
guide for centering the drill bit. The depth of the hole must be at least 12
millimeters (0.5 inch) longer than the length of the bolt. Clean out the
drill cutting with compressed air and insert the bolt through the bushing.
Stand on the mat and bushings and tighten the bolt
with an impact wrench.
Pavements. Asphalt-overlaid concrete usually
entails using a rock bolt that is
241.3 millimeters long and 15.9 to 19.1 millimeters in diameter (9.5 inches
long and 0.625 to 0.75 inch in diameter). The installation procedure is the
same as those for all-concrete pavements. The key factor in this
installation is to ensure the bolt has been set deep enough into the
concrete layer for a firm grip.
Asphalt Pavements. Anchoring in asphalt pavement requires a 241.3-
millimeter (9.5-inch) bolt and
polymer. A hole 254 millimeters deep and 38 millimeters in diameter (10
inches deep and 1.5 inches in diameter) is drilled at the center of each
predrilled mat hole. A two-part resin polymer is mixed and poured into each
hole to about 38 millimeters (0.5 inch) below the surface of the pavement.
An anchor bushing and bolt are immediately placed into each hole and pressed
firmly (standing on the bolt and bushing) against the mat. The polymer will
harden in about three minutes. Unless
extra people are available, there may
not be time to drill all the holes before beginning to pour the polymer.
Drilling and setting the bolts are usually accomplished concurrently..
(7)Surface Roughness. The final
grade of the repair must be checked using
line-of-sight profile measurement
stanchions, upheaval posts, or string lines to ensure the repair meets
surface roughness criteria contained in T.O. 35E2-4-1.
Procedures are described in T.O. 35E2-5-1,
Crushed-Stone Crater Repair and Line-Of-Sight Profile
Measurement for Rapid Runway Repair.
FOD covers should be no more than 5
degrees off parallel with the runway
(8)Check connection bolts and verify
that all connections between panels are tight and secure.Check anchor bolts
and verify that all bolts are secure and that the FOD cover is held snugly
against the pavement surface. In taxiway and apron applications, the leading
and trailing edges of the FOD cover must be anchored. The side edges must
also be anchored if the cover is located in an area where aircraft will be
required to turn.
(9) Clean-up..For all repair
methods, verify that the repair and adjacent area is cleared of any excess