The FAA is superseding an existing airworthiness directive (AD) 2012-04-13 for all RR model RB211-524G2-T-19, -524G3-T-19, -524H-T-36, and -524H2-T-19; and RB211-Trent 553-61, 553A2-61, 556-61, 556A2-61, 556B-61 556B2-61, 560-61, 560A2-61; RB211-Trent 768-60, 772-60, 772B-60; and RB211-Trent 875-17, 877-17, 884-17, 884B-17, 892-17, 892B-17, and 895-17 turbofan engines that have a high-pressure (HP) compressor stage 1 to 4 rotor disc with a part number (P/N) listed in Table 1 of the AD. That AD currently requires repetitive inspections of the axial dovetail slots, and follow-on corrective action depending on findings. Since we issued that AD, we determined that the definition of shop visit is too restrictive in the existing AD. This continues to require those repetitive inspections and follow-on corrective actions. This new AD changes the definition of a shop visit to be less restrictive. This AD was prompted by our determination that the definition of ”shop visit” in the existing AD is too restrictive, in that it would require operators to inspect more often than required to ensure safety. We are issuing this AD to detect cracks in the HP compressor stage 1 and 2 disc posts, which could result in failure of the disc post and HP compressor blades, release of uncontained engine debris, and damage to the airplane.
DATES: This AD is effective April 11, 2012. The Director of the Federal Register approved the incorporation by reference of a certain publication listed in the AD as of April 11, 2012.
Based on the service information, the FAA estimates that this AD will affect about 371 products of U.S. registry. We also estimate that it will take about 20 work-hours per product to comply with this AD. The average labor rate is $85 per work-hour. No parts will be required per product. Based on these figures, the FAA estimates the cost of the AD on U.S. operators to be $630,700.

