Earlier this month at Boeing Field, stripes on the tarmac were repainted. Something went badly awry. Reflective beads embedded in the paint on one taxiway came loose and were sucked...

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Earlier this month at Boeing Field, stripes on the tarmac were repainted. Something went badly awry.

Reflective beads embedded in the paint on one taxiway came loose and were sucked into the expensive engines of Boeing jets set for delivery to airline customers.

The paint job could end up costing $50 million.

Boeing has had to replace as many as 10 damaged 737 engines and is examining the engines of the last 757 ever built to see if it, too, is affected.

The search for clues to what went wrong intensified Monday, when the extent of the problem became apparent.

The airport’s insurance company is investigating, along with Boeing and the Federal Aviation Administration (FAA). The damaged engines, which cost about $5 million each, have been returned to the engine manufacturer for inspection.

A person close to the investigation said that as many as 10 engines had been damaged and replaced.

“One possibility is that they could be scrapped if deemed beyond repair,” Boeing spokesman Peter Conte said.

The damaged engines were never a safety issue, he said; the planes could fly perfectly well. It was rather a quality issue for the new jets.

“Foreign debris in the engine can cause a deterioration in performance over a more rapid period than would normally occur,” Conte said. “A customer would just find it unacceptable to take an airplane with such a damaged engine.”

To help illuminate airport runways and taxiways at night, the paint used for striping these surfaces is mixed with tiny reflective glass beads the consistency of granulated sugar.

Boeing uses the runway to do final flight tests and first flights with customers upon delivery. Conte said thousands of the glass beads were ingested by the engines of the airplanes involved.

Mechanics could see the beads in the engine intakes when they shone a flashlight. Further inspection found the tiny beads deep in the interior of the engines.

Boeing Field, officially King County International Airport, is owned and maintained by the county. It has more than 900 take-offs and landings every day, most of those by smaller aircraft. It also is used by large commercial cargo jets.

Airport Director Bob Burke said the restriping was done Dec. 3. Three days later, Boeing informed the airport that it had found paint flakes and glass beads on the landing gear of a 737.

Airport maintenance staff inspected the area and spent three days and 300 hours of machine time sweeping the area for debris.

“We found nothing. We gave it a clean bill of health,” Burke said.

But on Monday, Boeing came back with the bigger problem — glass beads in the engines.

Boeing and airport staff walked the runway and found that along one stretch — taxiway Bravo, on the west side of the runway — beads were separating from the paint.

“We don’t know why,” Burke said. “We were at a loss to figure out what was going on. We made the decision to take the paint up.”

The county is removing the paint and cleaning the whole area. Afterward, it will repaint without the glass beads.

Employees also are rechecking the entire airfield. The runways were shut down for an hour on Wednesday afternoon for inspection by Boeing and airport staff.

Burke said the weather on the day of the restriping was dry and didn’t appear to be a factor.

With the cause unknown, inspections continue.

“We’ve been out most of the day today looking for things, checking landing gear to see if we can find any of this material,” Burke said yesterday. “So far, we haven’t.”

The airport has issued an advisory to other aircraft owners who might be affected. So far, it has received no reports of problems besides those Boeing has had, Burke said.

He said the airport has adequate liability insurance and that insurance-company adjusters are seeking the cause of the problem. The paint batch is being tested, and the machinery used to do the striping has been quarantined for inspection.

FAA technical inspectors are assisting with the investigation.

“The process that they use for painting taxiways and runways is the same process they use nationwide,” FAA spokesman Allen Kenitzer said. “We’re trying to figure out why things were ingested here and we haven’t seen it anywhere else.”

Meanwhile, Boeing is towing its jets to the east side of the airfield before starting the engines and taking off.

For Boeing, the problem arrived out of the blue. But the company has already delivered some of the airplanes involved, with replacement engines. The engines are made by CFMI, a joint venture between General Electric of the United States and Snecma of France.

“We fully expect to make all our December deliveries and to make all the delivery targets for this year,” spokesman Todd Blecher said.

Dominic Gates: 206-464-2963 or dgates@seattletimes.com