GE: Remote diagnostics helped find cracked CF34 fan blades

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GE Aviation says its remote diagnostics services "contributed substantially" to finding three cracked fan blades among the thousands of engines it analyzed during 2008.

The engine maker revealed the statistics in comments to the US FAA in response to a proposed airworthiness directive (AD) for its CF34-3A and -3B series turbofan engines.

The AD, which was finalized 30 November, calls for operators of 1,966 of the engines to perform checks, remove certain blades and repetitively inspect other blades for cracks. In total, the directive is expected to cost operators more than $50 million to implement, says the FAA.

First proposed in April, the AD was spawned by fan blade failures, the first of which was accompanied by an under-cowl fire. Though the regulator could not determine the exact cause of the fire due to thermal damage, officials say faults included the fan blade failure and failed variable geometry aft actuator head hose, a part that will leak fuel if disconnected.

Included in the required actions starting 4 January is removing certain fan blades from service, inspecting the abradable rub strip around the perimeter of engines for wear due to fan blade extension, inspecting fan blades for cracks and checking the aft actuator head hose fitting for improper positioning, an issue that could have played a part in the fire.

As part of the repetitive inspection requirement for fan blade cracks, GE had proposed using its remote diagnostics program, which analyzes data transmitted automatically or manually by operators for more than 14,000 GE engines in operation to uncover trends that point to an impending failure.

Along with Mesaba Airlines, which uses the GE engines on its CRJ fleet, GE asked that remote diagnostics be used as an alternate means of compliance to inspections for determining blade health.

"GE Aviation states that the fan blade tang cracking algorithms developed by GE have been validated analytically, as well as in the field, and contributed substantially to finding three cracked blades during 2008," the FAA states in the final AD.

The regulator discounted the suggestion however, saying it could not include the remote diagnostics program as an alternate means of compliance "because it is a program outside of regulatory control".