Charter Jet's Blown Tire Was 'On Its Sixth Retread'

Air Safety Week, Feb 21, 2005

A tire that burst as a charter flight took off from Glasgow Airport in Scotland was on its sixth retread and nearly fully worn, UK accident investigators reported on Feb. 9. The incident occurred at 1830 hours on Sept. 1, 2004, and triggered a major alert as Air Malta KM197, with 143 people on board, had to circle in a holding pattern for three hours after takeoff to burn off fuel. Debris from the tire damaged the Boeing [BA] 737's flaps and its hydraulic system -- leading to the loss of fluid. Investigators said they were particularly alarmed that debris had just missed crucial flight control cables. The Air Accident Investigation Branch (AAIB) report stated: "The most concerning aspect of the tread failure was the piece of debris which had become lodged alongside the control cables for the spoilers and ailerons on the left wing. This had the potential to result in a control restriction during a critical phase of flight."

Five seconds after takeoff, air traffic control (ATC) noticed a white stream coming from the underside of the aircraft, according to the report. Once alerted to this, the flight crew advised that the plane was too heavy for an immediate landing and opted to stay in the vicinity to burn off fuel. Tire debris was then spotted on the runway by the crew of an arriving plane and the strip was closed for inspection and clearance. The crew of the Air Malta aircraft was unable to assess the extent of the damage, so they arranged a flyby of the control tower. An engineer on the ground saw that the tire was either missing or damaged but that the main landing gear was down. The air accident investigators said the burst tire had been on its sixth and final retread, "and may have reached its ultimate fatigue life prematurely for an undetermined reason."

A detailed examination of the limited amount of retrieved tread fragments had shown that the tire was "close to its fully worn condition," the report said, adding: "The tire had probably reached its ultimate fatigue life at an earlier age than predicted by the sample testing of other tires." However, the investigators made no recommendations in the report because the airline has made several safety improvements to prevent a recurrence. These include limiting aircraft tires to three retreads, improving tire checks and briefing flight crews.

In 1963, a Swissair Caravelle had an overheated wheel and tire catch fire in the wheelwell and crashed enroute. The crew had taxied up and down the Zurich runway before departure using power against braking in order to disperse the fog. That accident wised up crews to the importance of not retracting hot brakes or a failed tire after getting airborne.

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