Summary
The Federal Aviation Administration (FAA) proposes to supersede an existing airworthiness directive (AD), that is applicable to Pratt & Whitney JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -15A, -17, -17A, -17R, and -17AR turbofan engines. That AD currently requires a determination of the utilization rate and protective coating type of the 7th, 8th, 9th, 10th, 11th, and 12th stage high pressure compressor (HPC) disks, and removal, inspection for corrosion, and recoating of those HPC disks based on utilization rate. This proposal would require removal and replacement of protective coating of 7th, 8th, 9th, 10th, 11th, and 12th stage HPC disks, initial and repetitive inspections for corrosion pits and cracks, and removal from service as required. This proposal is prompted by operator reports of cracks found on several JT8D steel HPC disks since the existing AD was published. The actions specified in the proposed AD are intended to prevent fracture of the HPC disks, which can result in uncontained release of engine fragments, inflight engine shutdown, and airframe damage.