Blowouts and Debris Occur Rarely on Runways

Sept. 2, 2000 -- An American Airlines DC-10 was in the middle of its takeoff down the runway at Puerto Rico’s Luiz Munoz Marin International Airport in 1985 when the crew heard a loud thump. Suddenly, the plane began to vibrate.

At maximum speed, the captain slammed on his brakes, aborting the takeoff. He was unable to stop on the remaining runway and the plane ended up with its nose dug deep into a lagoon at the end of the airport.

No one was injured in the accident, but an investigation showed that one of the tires burst after running over debris on the runway. Another tire failed from overload.

Although the incident happened 15 years ago, the events leading up to it are similar to those investigators now believe led to July’s fatal Concorde crash, and indicate that debris on the runway poses potentially serious risks to passengers.

A preliminary report on the Concorde crash released this week, said a metal strip on the runway from another plane had likely burst one of the plane’s tires, sending chunks of hot rubber tearing into the wing, and triggering a chain of events that caused the plane to crash in flames less than two minutes after takeoff on July 25.

The report also found that a fire drill delayed a routine inspection of the runway, leaving it uninspected for 12 hours.

Concorde Circumstances Rare

Air safety experts say the circumstances that seem to have lead to the Concorde crash are very uncommon and that the Concorde’s design — in which the wheels are directly under the wing fuel tanks — made the situation worse.

Despite isolated incidents where tires blow out on takeoff or landing, typical airliners can usually recover without major incidents.

“The tire problem doesn’t even register on the list of safety concerns,” said Jim McKenna, executive director for the Aviation Safety Alliance, a safety advocacy organization based in Washington. “It’s almost unheard of for tires to cause the kind of damage that they caused on the Concord.”

An review of more than 50 Federal Aviation Authority reports in the last two and half years involving tire blow outs or other tire problems found that only in a few cases did tire failure lead to major incidents. Furthermore, National Transportation Safety Board records since 1985, showed runway debris was reported as a cause of tire failure in just a handful of cases.

In most cases, if a tire blowout is detected on take off, the flight is aborted. Usually, passengers are deplaned on the runway.

But sometimes if the plane has reached a speed where the take off can no longer be aborted, as it was with the Concorde, the captain must make an emergency landing with defective tires.

In August 1999, an Airtran Airways 737 taking off from Dallas/Fort Worth International Airport blew out a tire and had hydraulic loss on takeoff. According to the FAA report, “at 130 knots the aircraft had the feeling like on a cobblestone road.”

Although the captain was not able to abort the takeoff, he returned to the airport and landed safely. The report did not cite the cause of the blow out, but the incident shows what industry experts say: planes are designed to withstand the tire damage.

“Tires are built to prevent catastrophic events,” said former FAA official Michael Goldfarb. “And we haven’t had accidents in which the plane tires have been the cause of structural damage.”

Hundreds of Cycles

New aircraft tires are designed to be used for about 300 cycles — a takeoff and a landing — before they are retreaded. Michelin makes more than half of the aircraft tires used by U.S. airlines. At a cost of about $800 each, airlines retread them about five or six times before new ones are installed, according to industry experts.

A wear indicator bar at the bottom of the tire — required by the FAA — is checked daily by maintenance crews. The tires also undergo holographic tests to check whether the carcass is strong enough to support another retread.

But despite the checks, if a blow out occurs at maximum takeoff speed, it could spell disaster.

“It’s like one to two sticks of dynamite going off,” said Tom Yagger, a senior research engineer at the NASA Langley Research Center, which tests and evaluates the performance of landing gear.

Heat Spells Biggest Threat

Yagger said the biggest threat to aircraft tires is extreme heat, which weakens the tire.

But he insists that if the runways are kept in good shape, it is not something airline passengers should worry about.

Airport authorities, not the FAA, are responsible for keeping the runways clear of debris. Although FAA guidelines requires airport personnel to inspect runways for debris once a day, many airports across the country do more than that.

At Dallas/Fort Worth Airport, where the runway areas are divided by a highway, two maintenance workers posted on each side spend the day picking up pavement material, rocks, trash and any other debris.

At the Los Angeles International Airport runways are hosed down once a month to remove rubber off the runway.

In the New York City area, similar procedures are followed.

“FOD [foreign object debris] is generally taken very seriously by aviation workers,” said Greg Trevor, spokesman for the Port Authority of New York and New Jersey, which manages all three major airports that serve New York City. “In addition to the organized and required checks, you have a lot of people walking around. If they see something, they instinctively pick up.”