Sweepers Play Crucial Role Keeping Airline Passengers Safe by Protecting Engines

Every nervous flyer has his or her own checklist before taking off, just as the pilots in the cockpit have theirs.

• Flotation device under the seat: check.
• Access to the mid-plane emergency exits: check.
• Nothing suspicious or odd hanging from the wings: check.

Now, anxious flyers can add another item to the list: clean runway.
Pilot error. Terrorists. Faulty mechanics. Many things can bring down a plane, but none more quickly than a stray piece of metal on an airport runway.
Careful sweeping and daily checks of runways are a seldom-seen but integral part of keeping passengers safe. An impressive arsenal of sweeping machines, huge magnets, chemicals and even radar in some places—along with a simple scan by human eyes— keep airplanes where they belong: in the air.
The biggest single safety issue in the airline industry is FOD, or Foreign Object Debris. The FOD can be natural—such as rocks, brush or birds—or manmade—such as metal components or rubber. The rare but entirely possible result of FOD is that the object can be sucked into an aircraft engine and cause catastrophic damage or bring a plane down.
Unsecured fuel caps, tools from maintenance trucks and all sorts of other items can wind up on an airport runway. Routine sweeping—along with the use of powerful magnets—are part of nearly every airport’s maintenance routine.
“I don’t see how there is anything more important than keeping the runway clear of debris. It has tremendous negative outcomes if you have any debris on the runway,” said Bill Johnson, Executive Director of the Tallahassee-based Florida Airports Council. The group represents twenty commercial and seventy-three general aviation airports.
“Keeping a runway clear of debris,” he continued, “is the most important thing any airport can do.”.
The issue has several components. First, FOD such as small pieces of metal can end up in an engine. A second consideration is that an object on the runway can split an aircraft’s tire, peeling off rubber. The result is a piece of rubber that can wind up in an engine.
How airports deal with the issue depends on the size of the facility and frequency of flights as well as whether or not vehicles routinely cross the runways or travel on other areas that service airplanes. Additionally,. construction projects on hangars, air traffic control towers or terminals introduce hundreds of opportunities for FOD to get on a runway, Johnson noted.
Regardless, each day, the runways are checked—sometimes by highly technical radar or other devices, other times by a worker driving along the edge to look for FOD.
Airline safety experts and the federal government all place a priority on FOD and  its detection. The Air Force Safety Center has even produced special FOD prevention posters. One shows a man with a broom and another man bending down to pick up something from a runway. The caption: “One person can make a difference.” Another poster, this one with a gruesome skeleton holding pieces of metal, reads simply: “FOD: just waiting to happen.”
“People don’t understand the true implications [of FOD]. Even if a piece of material goes into an engine and doesn’t cause a crash, it can cause multiple millions of dollars worth of damage to an engine. For the airport, it is critically important that airport runways are clean of all debris all the time,” Johnson explained.
Sweeping plays a crucial role. Runways are often one or two miles long, and 100 to 200 feet wide. The size of the sweeping device depends on the size of the airport runway. Many use conventional sweepers—just like the ones for parking lots, construction sites and roads. However, to make sure that every piece of metal is collected, airport maintenance workers also use magnets, which are able to pull ferrous objects from oily or greasy surfaces. Blowers and vacuums can collect much of the debris, but they do not work as well as a strong magnet sweeper does in certain situations.
Magnet manufacturers customize their products so they can be used on trucks and conventional sweepers. Magnets are used in untold areas of industry. The magnets produced by Magnetic Products, Inc. of Michigan, for example, are mounted above food conveyers to pull out any stray metal bits that may have found their way into the food during the production process.
Two types of magnets are used with sweepers on airport runways. The first is a permanent magnet that requires no power to feed or operate it. The magnet can hold anything that is ferrous, or attracted to a magnet, at all times. A permanent magnet has no “off switch.” Debris has to be manually cleared from the magnet surface. The operation is simple, but requires more work. Usually, the magnets on sweepers have a faceplate that breaks the magnetic surface and reduces the amount of force required to clear the magnet.
The other type of magnet used with sweepers is an electromagnet, which operates with copper or aluminum coils. DC current is fed to the magnet, creating a powerful force field. Cut the electricity, and the magnet loses its power and allows items to drop away.
Conventional sweepers, sweepers with magnetic attachments and magnets used alone are all components of an airport’s runway maintenance equipment.
A final issue, according to Johnson, is the accumulation of rubber on the runways. As airplanes land, they leave a trail or skid mark from their tires. Too much rubber on a runway can hamper the aircraft’s ability to land. “Too much rubber affects the braking,” he said. “Braking with rubber on rubber instead of rubber on asphalt can affect stopping.” To counter that issue, airport operators use chemicals, water and sweepers to scrape the rubber when it begins to accumulate too thickly in vital landing areas.
Johnson compares runway cleaning with keeping a parking lot or roadway swept. The stakes, however, are much higher if an errant piece of material ends up in an aircraft engine.
“Whether it’s a parking lot at a mall or a road, you just have to sweep this stuff up. Thousands of airplanes can fly off a runway with a bolt sitting on it and nothing would happen. When it does, it’s a fluke. It’s just [that] we are trying to keep the fluke from happening,” Johnson said.
“It still comes down to the basics of how you keep stuff off any kind of runway, roadway or parking lot, except you don’t have a multi-million dollar engine at stake.
“The implication of a flat tire in a parking lot is a little different than a three-inch bolt going into a jet engine. In aviation, all accidents happen because of multiple things that go wrong,” Johnson said.
Keeping a runway clean by using road sweepers and magnets removes at least one element from the equation.
Nervous flyers: your list has now expanded.

By Marie Elium