U.S. Grounds Older 737s for Wiring Inspections

Reacting to new evidence of unsafe wiring in the fuel tanks of the world’s most popular airplane, the government Sunday grounded older models of Boeing 737s until they could be inspected by mechanics.

The highly unusual order, affecting about 15% of the 737s operating in the U.S., caused travel disruptions for an estimated 100,000 air passengers around the country, according to the Federal Aviation Administration.

But major airlines reported only minor disruptions, in part because this isn’t a peak travel season and because some planes had already been inspected. Cancellations and delays affected only a small fraction of scheduled flights, airline officials said.

United canceled 54 flights Sunday, including a handful at Los Angeles International Airport, United spokeswoman Mary Jo Holland said. Passengers were given seats on later flights or arrangements were made to accommodate them on other airlines, Holland said.

Julie Gardner, a spokeswoman for Continental Airlines, said less than 1% of its 2,000 daily flights were affected by delays or cancellations.

“The effect on our operations has been somewhat minimal,” she said. “We are equating it with a bad weather day.”

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Southwest Airlines, which said it has 35 planes affected by the order, was forced to cancel or delay a dozen out of 2,300 scheduled flights Sunday. As of late Sunday, all but one Southwest plane had been inspected, said spokeswoman Kristie Kerr.

The FAA is requiring immediate inspection of nearly 400 planes worldwide--including 179 in the U.S.--with 50,000 or more flight hours. Airline workers must look for evidence of exposed wires that may have generated sparks by rubbing against the inside of an aluminum casing tube, creating pinhead-sized holes. If fuel were to leak into the aluminum tube and be ignited by sparks from exposed wires, a plane could experience the sort of fuel tank explosion that is believed to have brought down Trans World Airlines Flight 800 off the coast of Long Island nearly two years ago.

The 737 grounding is the largest ordered by the FAA since 1979, when a McDonnell Douglas DC-10 lost a wing-mounted engine during takeoff and crashed, killing 273 passengers. Airlines were required to inspect their engine mounts and make any necessary repairs before the DC-10s could fly again.

“We’re just raising the safety bar,” said Marcia Adams, a spokeswoman for the FAA. The action doesn’t signal a greater concern for the overall safety of 737s, Adams said. “It could happen with any other model of aircraft,” she said.

At a news conference in Washington, Thomas McSweeny, the FAA director of aircraft certification, said he expects all planes to be in flying condition within two days.

The FAA on Thursday gave airlines one week to inspect the wiring of older 737s, which have generally been in service for 15 years or more. That order was prompted by the discovery of small holes in the aluminum tube of a Continental Airlines 737 with about 75,000 flight hours. But the agency ordered an immediate grounding Sunday after United Airlines reported signs of sparks in one of its planes, which had logged about 60,000 flight hours.

The discovery of problems in a relatively younger plane also prompted the FAA to extend its initial order to another 282 737s worldwide with as few as 40,000 flight hours. Airlines have 14 days to inspect those planes. Altogether, 2,716 737s are in service around the world.

The planes grounded Sunday include 737-100s and 737-200s, which were manufactured between 1968 and 1988. On average, an airplane logs about 3,500 flight hours per year.

Boeing, the world’s largest commercial airplane manufacturer, applauded the FAA order and pledged to work with airlines to expedite the inspections and minimize disruptions in flight schedules.

“It is in the best interests of the flying public to make sure that the affected airplanes do not have any problems that could compromise safety,” the Seattle-based company said in a statement.

United, Southwest and Continental have the most planes affected, according to the FAA. Vanguard Airlines, which primarily serves Midwest and Rocky Mountain states, America West Airlines and Frontier Airlines also use several of the older 737s.

The FAA has found that engine vibrations have caused bundles of electrical wires to rub against the inside of the metal tubes that protect them from the fuel carried inside the wings. To inspect the planes, mechanics must disconnect the wire bundles and remove them from their protective tubs.

Each wire is covered in colorful insulation, and the entire bundle is wrapped in Teflon tape. Inspectors are looking for signs that the tape and the wire insulation have rubbed away. If they find any exposed wires, they have been ordered to replace them with new bundles. Additionally, all wire bundles are to be fitted with a new Teflon sleeve, even if there is no visible damage to the tape. A Boeing spokesman said the inspection takes about 15 hours.

Boeing has already shipped about 330 sets of replacement wires and other parts to the airlines to avoid any further delays, said spokesman Russ Young. For the most part, the airlines will pay for the cost of the inspections and new parts, although in a few instances Boeing may cover the cost under warranty, Young said.

Southwest estimated the cost per plane at slightly more than $400.

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Two of Boeing’s other models, the 747 and the 767, also have bundles of electrical wires running through fuel tanks in the wings. But those wire bundles are already protected by the kind of Teflon sleeve that mechanics are installing in the 737s.

This is not the first mechanical problem to surface with the 737. Last year, the FAA ordered modifications to the 737 rudder power control unit after rudder problems were blamed for two crashes that killed 157 people. The FAA also intensified maintenance and inspection procedures for the 737 after stress corrosion caused a large piece of an Aloha Airlines plane to plunge into the Pacific Ocean in 1988, killing one flight attendant and injuring 61 others.

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Times staff writer Jeffrey L. Rabin contributed to this report.

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A Closer Look

The Federal Aviation Administration on Sunday grounded older 737s pending an inspection of electrical wiring in power lines near wing fuel tanks. Inspection of other 737s must be completed within 14 days.

* Planes affected: About 15% of the 1,088 Boeing 737s--the most common passenger aircraft in use--registered in the U.S.

* Airlines most affected: United, Southwest and Continental.

* Passengers affected: About 100,000.

* Looking for: Signs of wear in the wiring or the pipes that carry the wires through the fuel tanks.

* Time: About 15 hours per plane for inspection and repair, FAA inspections to be completed “within a day or two.”

Sources: Federal Aviation Administration, airlines, wire reports.