AD Aimed At Delinquent CF6 Operators

FAA is issuing an extensive inspection for General Electric CF6-45/50 engines amidst growing concerns that several operators outside the U.S. are compromising safety by not complying with maintenance practices.

The airworthiness directive (AD) targets what GE describes as a “small group of operators that have not incorporated GE Service Bulletins into their maintenance programs.” The engine maker says that after numerous attempts failed to ensure proper compliance from far-flung operators, it worked with the FAA on the AD with the aim that it will “serve as a strong enforcement mechanism to get operators to adopt more disciplined maintenance practices, consistent with the industry standards, for these engines.”

The action comes after a series of low-pressure turbine (LPT) failures in early CF6-45 and -50 engines, beginning with an initial incident in July 2008. The failures, some of which were uncontained, were traced to a rotor imbalance in the high-pressure turbine, leading to failure of the LPT rotor Stage 3 disk forward spacer arm. The AD, which supersedes an existing directive, requires an engine core vibration check as well as an ultrasonic inspection of the LPT spacer arm for fatigue caused by the HPT imbalance. The directive “reinforces the inspections introduced in the GE Service Bulletins issued during the last two years and requires all operators to comply with proper engine maintenance practices,” says GE.

The focus is on a group of fewer than 20 operators of older CF6 engines built between 1972 and 1982 for Airbus A300s, early Boeing 747-200s and McDonnell Douglas DC-10s. Although more than half of the 42 operators of these vintage widebody aircraft have complied, the remainder has not. Part of the issue, says GE, is being able to track the current ownership of the engines, many of which have passed to third- or fourth-tier operators. Although GE declines to identify specific operators, it is believed the targets of the AD are largely based in Africa and Asia.

About 620 of the 2,000 CF6-50 engines built remain in service, with 85% used to power freighters. The CF6-50 engine has been in service for 39 years and has accumulated more than 125 million hours.