NTSB Factual Report

HISTORY OF FLIGHT

On August 11, 2004, at approximately 1655 Central Daylight Time (PDT), a Boeing 777, G-VIID, operated by British Airways as flight 2024, experienced an engine failure upon takeoff from George Bush Houston Intercontinental Airport, Houston, Texas. The scheduled international passenger flight was being operated under the provisions of Title 14 CFR Part 129 and was en route to Gatwick International Airport, London, United Kingdom. The flightcrew declared an emergency and returned to Houston where an emergency evacuation was conducted. There were no injuries to the 3 flight crew, 12 cabin crew or 114 passengers.

According to the flightcrew, as the throttles were advanced for takeoff, an unusual noise and vibration was heard on the left side of the airplane. The captain, who was the non-flying pilot, initially commented that it might be the runway surface grooving. As the groundspeed increased, all engine parameters appeared normal and the takeoff proceeded. As the airplane rotated, the crew received a cockpit warning of LH Eng Vibration - Level 5. As the airplane reached 1,500 feet AGL, the crew observed smoke and haze in the cockpit. The flight was leveled off at 4,000 AGL, and the crew donned oxygen masks. At that time, the cabin crew advised that they had heard a loud noise from the left side of the airplane and that the cabin was filling with smoke. The flightcrew reduced thrust on the left engine and decided to make an immediate overweight landing back at Houston. They declared an emergency and coordinated with ATC for an immediate landing. The airplane touched down safely and the captain ordered an emergency evacuation. All doors were used in the evacuation except the L4 door, which was not used due to the firefighting activity at the left engine.

ENGINE INFORMATION

The airplane was powered by two GE90-85B engines. The GE90-85B is an ultra-high bypass (8.4:1), variable stator, dual rotor axial-flow turbofan engine that features a 10-stage high pressure compressor and is rated for 88,870 pounds takeoff thrust.

The left engine, S/N 900262, had accumulated 23,120 hours and 3,369 cycles since new. The engine had previously been removed from another airplane on September 24, 2003, with 20,586 hours and 2,999 cycles. A heavy shop visit, which included an overhaul of the High Pressure Turbine (HPT) was then performed at the GE Engine services facility in Cardiff, Wales. The engine was returned to service and installed on the accident airplane on January 26, 2004.

TESTS AND RESEARCH

Teardown of the left engine revealed that the stage 2 high pressure turbine (HPT) blade in position 35 had separated at its shank and damaged the trailing blades. This localized damage resulted in vibration and imbalance of the core rotor. As the engine continued to operate, asymmetric rotation caused the engine's #3 air/oil seal to fail. This seal failure allowed engine oil to enter the airpath, contaminating the bleed air being delivered to the airplane, and resulting in the smoke and fumes seen in the cockpit and cabin.

The investigation revealed that the stage 2 HPT blade in Position 35 had been manufactured from on obsolete P/N 1708M21P13 casting, yet was marked as a P/N 1708M21P19 blade. Blades that were manufactured from the P/N 1708M21P13 casting were limited to a service life of 1,100 cycles because of a problem with low cycle fatigue cracking. That problem was later resolved and blades subsequently manufactured as P/N 1708M21P19 blades had no life limit. Due to the mis-marking of the P/N 1708M21P13 accident blade with P/N 1708M21P19, it was not removed from service when it accumulated 1,100 cycles. At the time of the accident, the blade had accumulated 3,333 cycles. Metallurgical examination of the blade confirmed that the crack originated at the predicted stress point and failed in fatigue after exceeding the life limit.

Comprehensive review of all P/N 1708M21P19 blades produced by this manufacturer confirmed that no other blades were mis-labeled and additional review steps were added to the manufacturing process to ensure that no further mis-identified blades will be shipped.

NTSB Probable Cause

the failure of a high pressure turbine blade which damaged an oil seal and allowed smoke to enter the cabin. Contributing to the blade failure was the mis-labeling of the blade's part number by the manufacturer, which allowed the blade to remain in service far in excess of it's life limit.