Federal Aviation Administration October 20, 2011 – Federal Register Recent Federal Regulation Documents

These special conditions are issued for the Gulfstream Aerospace Corporation Model GIV-X airplane. This airplane will have novel or unusual design features associated with the architecture and connectivity capabilities of the airplane's computer systems and networks, which may allow access by external computer systems and networks. Connectivity by external systems and networks may result in security vulnerabilities to the airplane's systems. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for these design features. These special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards.

This action removes two modified VHF Omnidirectional Range (VOR) Federal airways, V-320 and V-440, from a final rule published in the Federal Register of April 28, 2011. That rule amended 29 Air Traffic Service (ATS) routes in Alaska affected by the relocation of the Anchorage VOR navigation aid. The FAA is taking this action as a result of these VOR Federal airways not passing flight inspections to retain existing minimum enroute altitude (MEA) requirements in the vicinity of Anchorage, AK.

We propose to supersede an existing airworthiness directive (AD) that applies to 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 this proposed AD. The existing 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 proposed AD would continue to require those repetitive inspections and follow-on corrective actions, and it would change the definition of a shop visit to be less restrictive. We are proposing 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.