Another time, a long, dripping wet cedar branch materialized on the runway -- on a bright, 80-degree summer day.
These are some of the more unusual items that have been found on the Paine Field runways over the years -- things that, if they get sucked up into a jet engine, can cause serious damage.
More common items found on the runways include rocks, sticks, pieces of wire, nuts, bolts and even garbage that blows over from trash bins.
Other items include wheel covers for small planes, gas caps, flattened aluminum cans or, more rarely, a piece of pavement that may have broken off from the runway.
"You never know what you're going to find out there," said Bill Penor, maintenance supervisor for Paine Field.
The battle against "FOD" -- foreign object debris, or damage -- never ends.
While the chance of FOD causing a catastrophic accident is very low, officials say, "it's our biggest fear," said Bruce Goetz, superintendent of operations at Paine Field.
Runways and taxiways are inspected frequently. The airport has two sweeper trucks that blow debris off the runways. One is equipped with a vacuum that can be used if needed. It has another device that scoops the stuff up.
Staff members are educated about the importance of FOD fighting, to the point of being encouraged to pick up anything they may see.
When new employees come on board, "the first thing they learn is 'FOD, bad,' " Penor said.
The Paine Field runways look smooth from a distance, but actually they are cut with tiny grooves --1 ½ inches apart, ¼-inch deep and ¼-inch wide.
This helps to keep water from accumulating on the runway -- water that could turn airplanes into hydroplanes.
It also means, however, that tiny rocks and other debris can stick in those grooves and need to be blown, scooped or sucked out.
The Snohomish County-owned airport spends roughly $200,000 per year in equipment costs, staff time and fuel keeping the runways and taxiways clean, Goetz said.
It's worth it, officials said.
A single blade inside a jet engine on a Boeing 777 costs about $40,000, airport director Dave Waggoner said. If one of those blades is chipped, it can throw the engine's balance out of whack, requiring that the blade on the opposite side be replaced, as well -- an $80,000 repair bill.
Even a tiny chip can affect the engine's fuel efficiency, Waggoner said.
Jet engines create small vortexes of air that swirl up into the rotating blades. Normally, they're invisible, but if there's water on the pavement, a mini-tornado full of vapor -- a tiny waterspout -- can be seen rotating upward into the engine.
Boeing, which has its own FOD program and equipment similar to the airport's, has high praise for Paine Field's efforts.
"We view it as a good housekeeping move on their part, to take the necessary steps to preserve the integrity of the airfield there at Paine Field," Boeing spokesman Terrance Scott said. "They've been an understanding and supportive partner for what we do out here on the flight line."
Some of that vigilance is required by law.
The Federal Aviation Administration, as part of its airport certification requirements, has a list of guidelines for maintaining runways and other paved areas. Included in that is a section on keeping those areas free of debris.
"Mud, dirt, sand, loose aggregate, debris, foreign objects, rubber deposits and other contaminants must be removed promptly and as completely as practicable," the rule reads. It provides exceptions for sand and other materials applied to runways to clear snow and ice.
Officials at Paine Field say they go the extra mile.
"We're known as having one of the cleanest operations around," Penor said.
That tone is set by Waggoner, a former Navy pilot and commander at Naval Air Station Whidbey Island. There was zero tolerance for FOD in the military, he said.
"The laws of aerodynamics are the same," he said.
At Paine Field, one of the airport's two sweeper trucks, which cost about $200,000 apiece, plies the main runway every weekday morning and on weekends as needed. The runway is inspected twice more every day and trucks are sent out again if necessary, Goetz said.
The sweeper truck slowly works its way up and down the nearly 2-mile-long airstrip, from the center line outward, blowing any debris to the side.
The runway is about 150 feet wide with 35-foot shoulders. It takes the truck about 15 passes and up to two hours to cover the entire stretch of pavement.
If a plane needs to take off or land, the truck ducks off onto a taxiway until the aircraft is out of the way, then heads back out.
Also used in fighting runway debris is the "FOD Boss." It's a synthetic mat, roughly 7 feet by 5 feet. The bottom is fitted with plastic scoops that pick up debris as the mat is pulled behind a pickup truck. A FOD Boss runs about $14,000.
It's especially good for taxiways, where the maneuverability of a pickup truck is an advantage, officials said, but it's also used on all three runways.
The two shorter runways, used only by smaller planes, are routinely cleaned once a week and inspected twice a day.
"Those pavements just don't take the abuse that the big runway does," Goetz said.
The pavement is kept in good condition, partly because of the grooves that funnel water to the side, "but if we're going to have any pavement issues, it's going to be on the big runway," he said.
Any unusual item found anywhere on runways or taxiways -- basically anything larger than a small rock or a stick -- is tagged and cataloged in a plastic bag. Those bags have "FOD" printed on them with a circle and a line through it.
Each item is traced, if possible. Many airplane parts, such as gas caps from private aircraft, have numbers on them or can be easily associated with a certain type of plane. The information then is compared with flight records for around the time the item was found. Sometimes an item will be taken to an airport tenant to see whether it matches a plane there, Goetz said.
The idea is to talk to the pilot or business owner to try to prevent further occurrences, officials said.
If an airplane part is damaged by FOD or if a recurring problem pops up, the problem can be traced with a technique similar to crime forensics. These items are sent to the Failure Analysis Service Technology lab in Prescott, Ariz.
A simple piece of Scotch tape is applied to the object, its contents analyzed and entered into a database.
If it's an asphalt chip from a runway from another airport, for instance, it can be matched to that airport. If it's a metal object from a plane, the type of metal can be narrowed down by the type used on a particular aircraft.
About 15 years ago, a particular type of pavement chunk kept turning up on Paine Field runways, Waggoner said. Turned out it was from an airport that had some deteriorating asphalt, and the problem was corrected.
The cedar branch, as it turned out, came from a float plane that had been to British Columbia.
Where the lizard came from, however, is still a mystery.
Bill Sheets: 425-339-3439; firstname.lastname@example.org.
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