The US FAA is proposing that operators of 1,600 Rolls-Royce AE3007-powered aircraft replace the fan spinners on the turbofan engines at a total cost of approximately $21 million across the fleet.
The proposed airworthiness directive (AD), to be published tomorrow, resulted from an incident in which the fan spinner released from an AE3007A turbofan engine in flight. The crew shut down the engine after noticing "noise and vibration" and performed an uneventful landing, says the FAA. The regulator did not provide details on the operator or when the event occurred.
Investigators determined that the left engine's fan spinner popped off, causing damage to the engine's fan blades. Debris from the spinner penetrated the forward engine cowl in three locations and cut through the aircraft outer skin in two locations.
At the time of the incident, the left engine had accumulated 11,682 operating hours and 8,535 cycles since new, indicating that the operator was likely an airline. The AE3007 engine is used on the Embraer ERJ regional jet line, including the ERJ145, as well as the Cessna Citation business jet.
During spin pit testing in the aftermath of the incident, Rolls-Royce found a high stress concentration in a bolt arrangement holding the spinner to the engine, a condition the FAA says could "potentially develop" into low-cycle fatigue cracks, adding, "This condition, if not corrected, could result in the fan spinner releasing, which could result in injury, damage to the engine and damage to the airplane".
The proposed fix, a replacement spinner, is expected to cost $12,943 per engine. That amount includes all the hardware but not the expected 1h labour cost to perform the change. Fleet wide, the cost would be nearly $21 million, according to FAA estimates. Operators would be required to install the new hardware at the next shop visit or within 1,500 additional cycles of the final issue date of the AD.
Source: Air Transport Intelligence news
