Federal Aviation Administration February 24, 2012 – Federal Register Recent Federal Regulation Documents

We propose to supersede an existing airworthiness directive (AD) that applies to all PW PW4074 and PW4077 turbofan engines. The existing AD currently requires removing the 15th stage high pressure compressor (HPC) disk within 12,000 cycles since new (CSN) or using a drawdown removal plan for disks that exceed 12,000 CSN. Since we issued that AD, we received a request from an operator that we clarify our inspection schedule for 15th stage HPC disks. This proposed AD would clarify that 15th stage HPC disks that have accumulated more than 9,685 CSN require a borescope inspection (BSI) or eddy current inspection (ECI) of the disk outer rim front rail for cracks prior to accumulating 12,000 CSN. We are proposing this AD to prevent cracks from propagating into the disk bolt holes, which could result in a failure of the 15th stage HPC disk, uncontained engine failure, and damage to the airplane.

We are superseding an existing airworthiness directive (AD) for all GE CF6-80C2B series turbofan engines. That AD currently requires installing software version 8.2.Q1 to the engine electronic control unit (ECU), which increases the engine's margin to flameout. This new AD requires the removal of the affected ECUs from service. This AD was prompted by two reports of engine flameout events during flight in inclement weather conditions, eight reports of engine in- flight shutdown (IFSD) events caused by dual-channel central processing unit (CPU) faults in the ECU, and four reports of engine flameout ground events. We are issuing this AD to prevent engine flameout or un- commanded engine IFSD of one or more engines, leading to an emergency or forced landing of the airplane.