Saturday, July 23, 2005

FOD Detection System

The term FOD, pronounced to rhyme with God, describes any debris present on the airside of an airport. Most people say it stands for "Foreign Object Debris." That abbreviation is a little weird, because most of the debris isn't from objects foreign to the runway, but completely native objects like airplanes and trucks. It consists of rivets and pieces of tires, and wheels off suitcases and garbage from the fuel truck driver's lunch. I notice the British say it stands for "Foreign Objects and Debris", which makes a bit more sense. I believe that FOD originally stood for "Foreign Object Damage" -- the result of debris entering a jet engine, puncturing a tire, or otherwise coming into contact with aircraft. When an engine suffers FOD, the engine is said to have been fodded, and so by back formation the culprit became FOD. Re-expanding the acronym required a slight change, but now FOD more often refers to the debris than the damage. We say "FOD damage" like "ATM machine" or "SIN number." Misnamed or not, the stuff is dangerous.

Debris on the runway from another aircraft caused the tire blowout leading to the Concorde crash. Ice and foam insulation striking the shuttle during launch caused the damage that lead to the Columbia shuttle disaster. FOD shortens the life of aircraft engines, and can cause an engine failure at the worst possible stage of a flight: just before the airplane has enough speed to fly. At best it's expensive. Reportedly it costs the industry $4 billion (I'm not sure if those are Canadian billions or British billions, as the number is on a British press release citing an American study) per year.

I can think of a couple of FOD-related problems that I've had. I landed an airplane, parked it went inside to prepare for the next flight, and came back out to discover a flat tire. Maintenance found a screw in it. I'm glad the tire picked up that screw on the way in and not the way out, or it could have made the landing more exciting. Another time, after my flight I taxiied an airplane to maintenance for a routine inspection. Later maintenance called me back to ask what happened to the propeller. I thought they were kidding but I came to look and saw a chunk the size of a quarter missing from the side of one blade of the propeller. They showed me a corresponding smaller ding on the opposite blade. That's very common, as the propeller spins fast enough to hit the object more than once. In that case they were able to "dress" the propeller, filing out the damage and making the propeller the right shape again while keeping it within tolerances. I remember being able to feel the curve of where it had been filed every time I ran my hand over that propeller on subsequent preflight inspections.

Vancouver International Airport has become the very first airport in the world to purchase a radar-based system for detecting FOD. In one test, a bolt was placed in the groove of a runway. Radar eight hundred metres away detected the bolt and the system output GPS coordinates accurate enough for airport personnel in a pickup truck to locate and remove it, in the dark, in under five minutes. The product is made by a British company called QinetiQ and it has also been tested at Heathrow and JFK in New York. Apparently it can detect all manner of FOD including gravel and animals.

I guess that means the end of conversations like

"Tower, we just saw some debris on the runway as we rolled out."
"Roger that, where was it?"
"Just past the intersection with delta, on the right there, about twenty feet from the edge."
"What did you say it was?"
"Not sure, looked like maybe some glasses."

And then someone can't resist getting on the radio and suggesting "martini glasses?" and all hell breaks loose. And that's before they have to close the runway for the guy in the pick up truck to drive up and down looking for the thing. "Just past delta" could cover half a kilometre. As soon as a crew says, "we saw something on the runway" the tower can reply "got it on Tarsier."

Tarsier is named after a cute mammal that has excellent night vison and can swivel its head 180 degrees. No word on whether it can dig a burrow. I think it's arboreal.

No comments: