What happened
On June 7, 2000, a VARIG Boeing 767-200ER, registration PT-VNN, was performing a passenger flight from Guarulhos (SBGR) to Lima, Peru. The aircraft was carrying 178 passengers and 13 crew members. During the takeoff roll on runway 09L, as the aircraft reached approximately 60 knots with engines at 97% N1, a loud bang occurred in the number 2 (right) engine. This was immediately followed by an uncontained engine failure and fire. Although the aircraft's internal fire warning systems did not alert the crew, the air traffic control tower notified the pilots of visible fire. The pilot aborted the takeoff and brought the aircraft to a stop approximately 540 meters from the opposite runway threshold. During the emergency evacuation, four passengers sustained minor injuries, including one leg fracture.
The investigation
CENIPA investigators examined the wreckage and the GE CF6-80C2B2 engine. The investigation revealed that fragments from the engine pierced the fuselage ahead of the right main landing gear and struck the right wing, though the passenger cabin remained intact. The failure was traced to a rupture in the high-pressure compressor (HPC) 3-9 stage spool. Metallurgical analysis conducted in Brazil and the United States determined that the fracture originated in the stage 7 hub due to a combination of low-cycle fatigue and dwell-time fatigue (DTF). The investigation found that the microstructure at the fracture origin was inconsistent with the required Ti-6-2-4-2 alloy specifications, featuring an excess of alpha primary grains. Furthermore, while a crack was estimated to be detectable during the previous inspection, the physical difficulty of inspecting the internal surfaces of the spool prevented detection.
Findings
- The engine failure was caused by an uncontained rupture of the HPC 3-9 stage spool.
- Manufacturing defects resulted in an area of quasi-cleavage within the component.
- Design deficiencies meant that standard liquid penetrant inspections were insufficient to detect cracks caused by dwell-time fatigue in these specific compressor stages.
- The fire was fueled by the fuel pump supply line being severed by the outward movement of the compressor casing.
- The crew's ability to respond was aided by timely notification from the control tower regarding the external fire.