GUY NORRIS / LOS ANGELES & ANDREW DOYLE / SINGAPORE
The uncontained failure of a General Electric CF6-80A2 powering an Air New Zealand (ANZ) Boeing 767 last week was the first suspected turbine disc burst on a CF6-80A.
The failure of the left engine high-pressure turbine (HPT) occurred on 8 December, as the twinjet was climbing through 11,000ft shortly after take-off from Brisbane, Australia. The crew returned to Brisbane immediately and none of the passengers or crew on board the 767-200ER was injured. Part of the left engine's cowling came off and debris damaged the pylon and leading edge of the wing. "Preliminary inspection of the damaged engine by the manufacturer in Brisbane showed a section of a high-pressure turbine came loose and fed back through the engine, penetrating the rear casing," says ANZ.
The HPT, which is the focus of the investigation, has been sent for inspection by the Australian Transport Safety Bureau (ATSB). The aircraft is expected to be grounded for up to four weeks pending repairs.
GE is developing an inspection programme for more than 420 CF6-80As following the failure, and the US Federal Aviation Administration is expected to follow with an immediate airworthiness directive mandating the action. A US Airways-operated CF6-80C2 suffered a similar failure in September 2000, which was the first turbine disc failure in the type's 16-year history.
Although GE declines to speculate on the root cause it says "we have sent a metallurgist and a safety investigator to help the ATSB which has the suspect parts." The cause of the failure is, however, believed to be a fatigue crack in one of the high- pressure turbine discs. The suspect parts of the failed engine are thought to have been manufactured in the mid-1980s and have around 12,000 cycles.
Source: Flight International
