Discussion \n\n\tThe FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that supersedes AD 2006-10-17, amendment 39-14601 (71 FR 28766, May 18, 2006). The existing AD applies to certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. That NPRM was published in the Federal Register on October 31, 2008 (73 FR 64894). That NPRM proposed to continue to require replacing brackets that hold the P5 panel to the airplane structure, the standby compass bracket assembly, the generator drive and standby power module, and the air conditioning module. That NPRM also proposed to continue to require, among other actions, inspecting for wire length and for damage of the connectors and the wire bundles and doing applicable corrective actions if necessary. That NPRM also proposed to require an additional operational test of the P5-14 panel. \n\nComments \n\n\tWe provided the public the opportunity to participate inthe development of this AD. We have considered the comments that have been received on the NPRM. \n\nRequest To Align AD Action With Related Service Bulletin \n\n\tOne commenter, Boeing, requests that the NPRM wording for paragraph (f)(4) be revised to align with Boeing Service Bulletin 737-24A1141, Revision 3, dated February 20, 2008. Boeing states that the current wording in the NPRM indicates that the standby compass bracket assembly must be replaced with a new assembly. Boeing states that Boeing Service Bulletin 737-24A1141, Revision 3, dated February 20, 2008, states that the standby compass bracket assembly need not be replaced for all groups of airplanes. Boeing Service Bulletin 737-24A1141, Revision 3, dated February 20, 2008, also states to replace the standby compass bracket if necessary. \n\tWe agree that clarification may be necessary. Paragraph (f)(4) is a restatement of actions required by AD 2006-10-17, and is retained in this supersedure. Paragraph (f) of this AD states that the corrective actions (including replacing the standby compass bracket assembly as required by paragraph (f)(4) of this AD) must be done, as applicable. In addition, we note that a new requirement of this AD, paragraph (i) of this AD, requires that after the effective date of this AD, only Revision 3 of Boeing Service Bulletin 737-24A1141, dated February 20, 2008, be used to do all applicable actions. We have not made any changes to the AD in this regard. \n\nRequest To Clarify Terminology \n\n\tOne commenter, the Air Transport Association (ATA), on behalf of its member Delta Airlines, requests that the terminology in Boeing Service Bulletin 737-24A1141 be clarified. In its comment, Delta states that it believes that Boeing Service Bulletin 737-24A1141 contains material that is vague in nature, which would leave information subject to interpretation. \n\tDelta states that Boeing Service Bulletin 737-24A1141 includes figures that contain statements such as, "Some airplanes may have different wires, panels or connectors'' (e.g., in Figures 6-11 and 94 of the service bulletin). Delta is concerned that statements such as these, when dealing with compliance situations in which many different individuals are left to determine the intent and method prescribed by such instructions, can lead to problems determining the state of compliance of aircraft that have had work accomplished per the required accomplishment instructions. In the past, this has led to the grounding of airplanes at significant expense to the airlines, while confusion over the interpretation of said instructions is determined and resolved. Therefore, Delta believes that either Boeing Service Bulletin 737-24A1141 should be revised to clarify the meaning of vague terms (e.g., "typical''), or the AD should include notes to accomplish the same intent. \n\tDelta states that failure to clarify the vague terms will likely lead to the same compliance issues that operators previously experienced with the B737 Rudder System Enhancement Program (AD 2007- 03-07, Amendment 39-14918, 72 FR 4625, February 1, 2007) and MD88 auxiliary hydraulic pump feeder wire inspection/modification (AD 2006- 15-15, Amendment 39-14696, 71 FR 43035, July 31, 2006). \n\tWe find that clarification of certain material contained in Boeing Service Bulletin 737-24A1141, Revision 3, dated February 20, 2008, is necessary. We discussed the material referenced by the commenter as "vague'' with Boeing to clarify the intended meaning. \n\tBoeing noted that Boeing Service Bulletin 737-24A1141, Revision 3, dated February 20, 2008, was initially released in January 2004, and since then has been revised three times (December 2004, December 2005, and February 2008) to update and correct information. As specified in Boeing Service Bulletin 737-24A1141, Revision 3, dated February 20, 2008, required actions include: replacing brackets to lower the P5 overhead panel to increase the space between the wire bundles and the dripshield panel and modules; inspecting to determine if unwanted wire length or damage exists; retying the wire bundle or reterminating the wire bundle into the connector to eliminate the unwanted wire; and repairing damaged wire and using teflon tape, nylon sheet, and lacing tape to give greater protection to the wire bundles. Also, depending on airplane configuration, the service bulletin specifies replacing the standby compass bracket assembly with a new assembly, and replacing the stud assemblies with new assemblies. \n\tBoeing clarified that the P5 overhead panel varies from customer to customer, as indicated in the 98 figures contained in Boeing Service Bulletin 737-24A1141, Revision 3, dated February 20, 2008. Boeing explains that the phrase questioned by the commenter--i.e., "Some airplanes may have different wires, panels or connectors''--was used in the illustrations in the figures to indicate that the configuration on any given customer's airplane may be different from that shown in the illustrations. The illustrations simply provide examples of various configurations an operator might find; therefore, the information provided in the illustrations of the figures is for reference. Boeing explained further that the word "typical'' is intended to represent a configuration that is in more than one location within an illustration. Additionally, while accomplishment of the steps specified in the tables of the figures is required, the illustrations are simply examples of the wiring configuration. \n\tIn addition, we find that the word "unwanted'' requires clarification. That term is used in various locations in the service bulletin in conjunction with wire length conditions--e.g., paragraph 3.B.9. of the Accomplishment Instructions states to "Inspect the connectors and the wire bundles in the rear, P5 aft panel to determine if unwanted wire length exists in Group 1-22 airplanes. See Figure 6.'' We clarify that the General Information section of the Accomplishment Instructions of Boeing Service Bulletin 737-24A1141, Revision 3, dated February 20, 2008, references Boeing Standard Wiring Practices Manual (SWPM) 20-10-11 for wire installation procedures, including defining the amount of slack and making sure that all wire slack is securely tied into the parent harness or clamped. Additionally, it should be noted that tables found in certain figures of Boeing Service Bulletin 737-24A1141, Revision 3, dated February 20, 2008 (Figure 6, for example), refer operators to the SWPM for general conditions for wire installation. \n\tWe have revised this final rule to include new Note 2 and Note 3 to clarify the meaning of the terminology discussed previously. \n\nUpdated Contact Information for Alternative Methods of Compliance (AMOCs) \n\n\tWe have updated the contact information for paragraph (k) of this final rule. \n\nConclusion \n\n\tWe reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting theAD with the change described previously. We also determined that this change will not increase the economic burden on any operator or increase the scope of the AD. \n\nCosts of Compliance \n\n\tThere are about 740 airplanes of the affected design in the worldwide fleet. This AD affects about 333 airplanes of U.S. registry. \n\tFor all airplanes, the required inspection, replacements, and wiring change that are required by AD 2006-10-17 and retained in this AD take about 16 or 18 work hours per airplane (depending on airplane configuration), at an average labor rate of $80 per work hour. Required parts cost about $10,231 or $11,139 per airplane (depending on the kit). Based on these figures, the estimated cost of the replacements and inspections required by this AD for U.S. operators is between $3,833,163 and $4,188,807, or between $11,511 and $12,579 per airplane. \n\tFor certain airplanes, the modification of the generator drive and standby power module assembly that is required by AD 2006-10-17 and retained in this AD takes about 2 work hours per airplane, at an average labor rate of $80 per work hour. The airplane manufacturer states that it will supply required parts to operators at no cost. Based on these figures, the estimated cost of this modification required by this AD is $160 per airplane. \n\tFor certain other airplanes, the modification of the air conditioning module assembly that is required by AD 2006-10-17 and retained in this AD takes about 1 work hour per airplane, at an average labor rate of $80 per work hour. The airplane manufacturer states that it will supply required parts to operators at no cost. Based on these figures, the estimated cost of this modification required by this AD is $80 per airplane. \n\tFor certain airplanes, the new action takes about 21 or 23 work hours per airplane depending on the airplane configuration, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the new actions required by thisAD for U.S. operators is $1,680 or $1,840 per airplane, depending on the airplane configuration. \n\nAuthority for This Rulemaking \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\tWe havedetermined that this 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 "significant regulatory 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); and \n\t(3) 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\tWe prepared a regulatory evaluation of the estimated costs to comply with this AD and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation. \n\nList of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\nAccordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows: \n\nPART 39--AIRWORTHINESS DIRECTIVES \n\n1. The authority citation for part 39 continues to read as follows: \n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\nSec. 39.13 (Amended) \n\n2. The Federal Aviation Administration (FAA) amends Sec. 39.13 by removing amendment 39-14601 (71 FR 28766, May 18, 2006) and by adding the following new airworthiness directive (AD):