Removing foreign object debris (FOD) from the airfield is a safety-critical task all airports must complete on a regular basis. Earlier this year, Centennial Airport (APA) just outside Denver added a new strategy to its existing program that is getting great reviews from the maintenance staff.
For a total cost of $11,000, the general aviation airport installed four FOD Prevention Mats at the end of a gravel road that connects two paved portions of the airfield used by heavy equipment and airport vehicles. The mats are designed to remove stones, mud, metal and other debris from the vehicles’ tires before they travel onto the airfield. If left unattended, such debris can be ingested into aircraft engines and cause dangerous and costly damage.
“The gravel haul road often leads to debris buildup on the tires of our vehicles, and over time, they accumulate rocks, mud and other material,” states APA Maintenance Director Matt Smith. “To prevent this debris from reaching paved surfaces of the airfield, the FOD mats were installed to clean the tires before vehicles reenter areas where aircraft operate.”
 FACTS&FIGURES
Project: Foreign Object Debris Prevention Location: Centennial Airport, in Englewood, CO Product: FODS (Foreign Object Debris System) Prevention Mats Manufacturer: FODS LLC Size: 12 ft. x 7 ft. Configuration: 4 mats arranged to form 28-foot-long path How They Work: When a vehicle drives over the nubby mats, debris falls out of its tire treads & from the undercarriage Cost: $11,000 for 4 mats, plus special shovel to remove debris from mats Installation: March 2024 Duration: 45 minutes Key Benefit: Reducing risk of foreign object debris damage; labor savings |
Previously, APA used a somewhat similar unit built in its own maintenance shop. “Our staff created a giant metal device, similar to a cattle grate,” Smith explains. “We hollowed out a hole under this grate to collect larger rocks from the tires. It was not very effective because its metal rods frequently broke, and we had to weld them back together. It also was very time-consuming to remove the debris that was picked up.”
The four FODS manufactured by FODS LLC installed this March are proving to be more effective and easier to clean. “They have worked great,” Smith reports. “They collect significantly more debris than our old cattle grates. And when we do our regular clearing of runways and taxiways with our brooms or sweepers, there is less debris collected by those trucks.”
The mats get a lot of use throughout the day. Airport-owned vehicles, FAA vehicles, dump trucks and even an occasional 644 front loader drive over them.
Installation and Cleaning
Smith reports that maintenance workers at APA installed four 12- by-7-foot FODS mats in about 45 minutes, using stakes to anchor them into the ground. Naturally, installation time varies per site.
The mats are made of high-density polyethylene (HDPE), a strong thermoplastic polymer also used for underground pipes. This makes them durable enough to withstand more than 3 million pounds and more than 1 million vehicle passes, says Chris Hefner, commercial manager for
FODS LLC.
As vehicles drive over the mats, alternating rows of HDPE pyramids cause the tread in their tires to flex and deform, allowing trapped debris to fall out. The process also creates slight vibrations that help loosen debris on the undercarriage of vehicles. The expelled debris collects
at the base of the mat to prevent it from re-collecting on subsequent vehicles.
APA also purchased a special shovel to remove the debris left behind in the base of the mats. The mat manufacturer created the shovel to fit into the grooves between pyramids. The shovel makes removing debris and rocks very easy, Smith attests.
Street sweepers and skid-steers with broom attachments can also be used to clean the mats. Pressure washers and water tanks are other options, but they leave behind water, which eventually creates mud.
The mats can be relocated and are designed to last for more than 10 years. From an environmental standpoint, the HDPE material from which they are made can be recycled at least 10 times.
Tested Performance
Hefner notes that the 12-by-7-foot FODS mats can be combined and configured to best match the traffic pattern of each airfield entry point. He suggests having at least four mats in a row to allow suitable distance of travel for multiple full tire rotations. The most common mat layout is one mat wide and four mats deep to create a swath that is 12 feet wide and 28 feet long. This was the design APA selected.
“Some of the larger airports have ordered enough mats to cover all of their access points,” he adds. “At one point, O’Hare International Airport was using 80 of our mats. Denver International Airport has many of them throughout their property.”
A product test commissioned by the U.S. Navy this June documented the mats’ performance. In Phase One, the number of FOD pieces collected by the Navy’s “inspect and rotate” protocol was measured over several days. In this system, tires are inspected for debris by hand after one full revolution, and any FOD is tossed into a bucket. In Phase Two, FODS mats were used, and there was more than a 982% increase in the number of FOD collected over the same period, Hefner reports.
The FODS mats help prevent vehicles from carrying gravel and other potentially dangerous debris onto the airfield.
After eight months using their new FODS mats, maintenance crews at APA were so pleased, the airport plans to order four more by winter. “They will be placed adjacent to the giant milling pad in another part of the airport, where fully loaded dump trucks filled with snow go to stockpile their snow after a snowstorm,” Smith remarks. “I am sure the new mats will be effective in that area as well.”
