Discussion \n\n\n\tWe issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to the specified products. That NPRM was published in the Federal Register on June 22, 2011 (76 FR 36390). That NPRM proposed to require replacing or modifying the upper and lower rudder PCMs. \n\nComments \n\n\n\tWe gave the public the opportunity to participate in developing this AD. The following presents the comments received on the proposal and the FAA's response to each comment. \n\nSupport for the NPRM (76 FR 36390, June 22, 2011) \n\n\n\tThe National Transportation Safety Board fully supports the NPRM (76 FR 36390, June 22, 2011). \n\nRequest To Clarify the Discussion Section and Paragraph (e) of NPRM (76 FR 36390, June 22, 2011) \n\n\n\tBoeing requested that we revise the Discussion section and paragraph (e) of the NPRM (76 FR 36390, June 22, 2011) to clarify that the corrective actions are not intended to prevent the manifoldfrom cracking, but rather to prevent the cracking of the manifold from progressing to a rudder surface hard-over. Boeing pointed out that the secondary retention device incorporated in Boeing Alert Service Bulletin 747-27A2497, dated September 30, 2010, prevents the yaw damper modulating piston assembly from shifting after a manifold failure, therefore, preventing a rudder surface hard-over. Boeing suggested removing the phrase, ''if not corrected,'' from the sentence, ''Cracking in a rudder PCM manifold, if not corrected, could result in a failure of the upper or lower rudder PCM manifold which could result in a hard-over of the rudder surface leading to an increase in pilot workload and a possible high-speed runway excursion upon landing.'' In addition, Boeing suggested revising the sentence, ''Although commanding full retract, pilot pedal inputs were ineffective in moving the lower rudder back to the right,'' to replace the term ''retract'' with ''right rudder,'' and revising the sentence, ''These events did not result in a hard-over, but created the need for a retention feature solution specified in AD 2008-13-03, Amendment 39-15566, for Model 747- 400, -400D, and -400F series airplanes,'' to clarify that the additional three events did not result in end-cap separation or a hard- over. \n\tWe agree that replacement or modification of the upper and lower rudder PCMs is intended to prevent the yaw damper modulating piston assembly from shifting after a manifold failure, consequently preventing a rudder surface hard-over. Therefore, we have revised paragraph (e) and the corresponding language in the Summary of this AD to clarify the intent. However, we cannot revise the Discussion section of this AD, because that section is not re-stated in this final rule. \n\nConclusion \n\n\n\tWe reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously and minor editorial changes. We have determined that these minor changes: \n\tAre consistent with the intent that was proposed in the NPRM (76 FR 36390, June 22, 2011) for correcting the unsafe condition; and \n\tDo not add any additional burden upon the public than was already proposed in the NPRM (76 FR 36390, June 22, 2011). \n\tWe also determined that these changes will not increase the economic burden on any operator or increase the scope of the AD. \n\nCosts of Compliance \n\n\n\tWe estimate that this AD affects 7 airplanes of U.S. registry. \n\tWe estimate the following costs to comply with this AD: \n\n((Page 7522)) \n\n\n\n\n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost on U.S. \n\tAction Labor cost Parts cost Cost per product operators ---------------------------------------------------------------------------------------------------------------- Replace rudder PCM (P/N 241700- 11 work-hours x $85 $5,856 $6,791 $47,537 \n\t1007). per hour = $935. Replace rudder PCM (P/N 241700- 11 work-hours x $85 8,568 9,503 66,521 \n\t1005). per hour = $935. Modify rudder PCM (P/N 241700-1007) 3 work-hours x $85 1,374 1,629 11,403 \n\tper hours = $255. Modify rudder PCM (P/N 241700-1005) 3 work hours x $85 4,086 4,341 30,387 \n\tper hour = $255. ---------------------------------------------------------------------------------------------------------------- \n\nAuthority for This Rulemaking \n\n\n\tTitle 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority. \n\tWe are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: ''General requirements.'' Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action. \n\nRegulatory Findings \n\n\n\tThis AD will not have federalism implications under Executive Order 13132. This AD will not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. \n\tFor the reasons discussed above, I certify that this AD: \n\t(1) Is not a ''significantregulatory action'' under Executive Order 12866, \n\t(2) Is not a ''significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979), \n\t(3) Will not affect intrastate aviation in Alaska, and \n\t(4) Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. \n\nList of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.