Examining the Docket \n\n\tYou may examine the airworthiness directive (AD) docket on the Internet at http://dms.dot.gov or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone (800) 647-5227) is located on the plaza level of the Nassif Building at the street address stated in the ADDRESSES section. \n\nDiscussion \n\n\tThe FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that supersedes AD 2003-23-01, amendment 39-13364 (68 FR 64263, November 13, 2003). The existing AD applies to certain Boeing Model 747-400, 747-400D, and 747-400F series airplanes. That NPRM was published in the Federal Register on February 13, 2006 (71 FR 7446). That NPRM proposed to continue to require certain requirements of the existing AD. That NPRM also proposed to expand the applicability and discontinue certain requirements of the existing AD. That NPRM also proposed to require repetitive inspections of the power control modules (PCMs) and replacement of the PCMs if necessary. \n\nComments \n\n\tWe provided the public the opportunity to participate in the development of this AD. We have considered the comments that have been received on the NPRM. \n\nSupport for the NPRM \n\n\tOne commenter, Northwest Airlines (NWA), expresses support for the NPRM, stating that the type of failure event addressed in the NPRM has occurred on a NWA airplane. \n\nRequest to Cite Revised Service Information \n\n\tThree commenters, Boeing, South African Airways, and NWA request that we revise the NPRM to refer to current service information. The commenters state that Boeing Service Bulletin 747-27A2397, Revision 2, dated September 1, 2005, has been issued. \n\n\tWe agree with this request. We have determined that Boeing Service Bulletin 747-27A2397, Revision 2, shows changes of operators in the effectivity and clarifies the compliance information, but does not add any further actions or increase the economic burden on operators. Therefore, we have revised the AD to refer to Boeing Service Bulletin 747-27A2397, Revision 2, as the appropriate source of service information for accomplishing the requirements of the AD. We have also revised paragraph (k) of the AD to indicate that actions done previously in accordance with Boeing Alert Service Bulletin 747- 27A2397, Revision 1, dated March 31, 2005, are also acceptable for compliance with the corresponding requirements of this AD. \n\nRequest to Remove Certain Part Numbers (P/Ns) \n\n\tOne commenter, Boeing, requests that two P/Ns be removed from the NPRM. Boeing states that P/Ns 332700-1009 and 333200-1009 are internal supplier P/Ns that are stamped on the PCM manifold and are not PCM top assembly P/Ns. Boeing states that these P/Ns are not referenced on the equipment identification plate for either the upper or lower PCM. \n\n\tWe agree with this request. Though all revisions of the Boeing service bulletin specify P/Ns 332700-1009 and 333200-1009 as replacement P/Ns for cracked PCMs, we have determined that these P/Ns do not refer to PCM top assemblies; instead, these P/Ns refer only to the PCM manifolds. Only top assembly P/Ns of the upper or lower rudder PCMs should be identified in the AD; that is P/N 332700-1003, -1005, or -1007; or P/N 333200-1003, -1005, or -1007. Therefore, to prevent confusion on the part of operators attempting to track PCM installations, we have removed the reference to P/Ns 332700-1009 and 333200-1009 as top assembly P/Ns from paragraph (l) of the AD. \n\nRequest to Revise Paragraph (j)(2) of the NPRM \n\n\tOne commenter, Fortner Engineering, requests that we revise paragraph (j)(2) of the NPRM to read "PCMs or manifolds" rather than "PCMs" only. Fortner Engineering states that certified repair stations in addition to Parker Hannifin, which is the PCM original equipment manufacturer (OEM), overhaul the valve (manifold) and that those repair stations should not be required to send the entire PCM to the OEM if a crack is discovered in the manifold. Fortner Engineering asserts that, as long as all information required by paragraph (j)(1) of the NPRM is included with the manifold, there is no need to send the entire PCM to the OEM. \n\n\tWe agree with this request. The intent of paragraph (j)(2) of this AD is to return PCMs having cracked manifolds to the manufacturer for analysis of the cause of the cracking. If the PCM can be returned to service with a new or serviceable manifold, there is no need to send the entire assembly to the OEM. Therefore, we have revised paragraph (j)(2) of the AD to read "PCMs or manifolds." \n\nRequest to Revise Paragraph (l) of the NPRM \n\n\tThe same commenter requests that we delete the phrase, "either by the operator or the supplier" from paragraph (l), "Parts Installation," of the NPRM. Fortner Engineering asserts that the operator should be free to determine whetherthe PCMs will be inspected by the operator, the supplier, or any other appropriately rated and equipped facility. \n\n\tWe agree with this request. The intent of paragraph (l) of the AD is to ensure that all affected PCMs are inspected for cracks before any return to service. The primary concern is not which facility inspects the PCMs, but rather that the inspections are performed by properly equipped and authorized facilities in accordance with the applicable service information. Therefore, we have revised paragraph (l) by deleting the phrase specified by Fortner Engineering. \n\nRequest to Include Alternative Method of Inspection \n\n\tThe same commenter requests that we include an alternative method of inspecting for cracking of the manifolds of suspected PCMs. Fortner Engineering states that a dye penetrant inspection performed in accordance with ASTM-E474, Type 1, Method A, Sensitivity Level 4, will better ensure detection of any manifold defects. Further, Fortner Engineering asserts that the OEM, Parker Hannifin, has already received approval of this dye penetrant method as an alternative method of compliance (AMOC) with AD 2003-23-01. \n\n\tWe agree that a dye penetrant inspection is an acceptable alternative to the ultrasonic inspection specified by the AD, because the dye penetrant technique provides a more thorough method for detecting cracking of the area of interest on the PCM manifold. However, we do not agree that ASTM-E474, Type 1, Method A, Sensitivity Level 4, has already been approved as an AMOC with AD 2003-23-01. In fact, the AMOC using dye penetrant inspection that was requested by Parker Hannifin and approved as of November 21, 2003, was in accordance with ASTM-E1417, Type 1, Method A, Sensitivity Level 4, and does not actually specify that it applies to the manifold. We are not aware of the dye penetrant inspection specification ASTM-E474, Type 1, Method A, Sensitivity Level 4; therefore, no change is necessary to the AD in this regard. However,as specified in paragraph (m) of the AD, a further AMOC may be requested if data are submitted to substantiate that ASTM-E474, Type 1, Method A, Sensitivity Level 4, specifies an acceptable method of inspection for compliance with the requirements of this AD. \n\nNotification of Compliance Time Conflict \n\n\tThe Air Transport Association (ATA), on behalf of its member NWA, states that there are errors in a chronology described in the preamble of the NPRM. NWA points out an apparent conflict between the compliance times specified in different sections of the NPRM. NWA notes that the third paragraph of the "Actions Since Existing AD Was Issued" section of the preamble states, "The compliance time for the initial inspection (for airplanes not previously inspected as required by AD 2003-23-01) has been revised to the earlier of 56,000 total flight hours or 9,000 total flight cycles * * *." NWA then notes that paragraph (h) of the NPRM states, "For airplanes not inspected prior to the effective date of this AD as specified in paragraph (g) of this AD: At the later of the times specified * * * prior to the accumulation of 56,000 total flight hours or 9,000 total flight cycles * * *." \n\n\tWe acknowledge NWA's concern; however, we do not agree that there is a conflict in the compliance time statements. Paragraph (h) of the AD more fully states, "For airplanes not inspected prior to the effective date of this AD as specified in paragraph (g) of this AD, At the later of the times specified in paragraph (h)(1) or (h)(2) of this AD * * *." Paragraph (h)(1) of the AD states, "Prior to the accumulation of 56,000 total flight hours or 9,000 total flight cycles, whichever occurs first." Paragraph (h)(2) of the AD states, "Within 24 months after the effective date of this AD." The "later of the times" statement of paragraph (h) refers to the relationship between paragraphs (h)(1) and (h)(2). In paragraph (h)(1), the statement, "whichever occurs first" is consistent with the statement "the earlier of" that appears in the "Actions Since Existing AD Was Issued" section of the preamble. Paragraph (h)(2) is the grace period for airplanes not inspected prior to the effective date of the AD. No change is needed to the AD in this regard. \n\nRequest to Withdraw NPRM \n\n\tATA, on behalf of its member United Airlines (UAL), states that it is opposed to the NPRM. UAL states that, based on the original AD 2003- 23-01, there have been no further reports of cracked PCM manifolds. UAL asserts that the original incident of a cracked PCM manifold airplane failure was an isolated event, and further asserts that the event was controllable. Although UAL made no specific statement to this effect, we infer that UAL considers the AD to be unnecessary and requests us to withdraw the NPRM.\n \n\tWe do not agree with this request. Although UAL correctly states that no other cracked PCM manifolds have been discovered since the release of AD 2003-23-01, the root cause for the premature fatigue failure of the lower rudder PCM on the event airplane has yet to be determined; and although analysis of the results of accomplishing AD 2003-23-01 did not yield that root cause, that analysis highlighted a previously unidentified single point failure of the PCMs. This new AD is intended to protect against such a single point failure occurring on the upper rudder PCM. Without the on-going inspections required by this AD, a developing crack of either the upper or lower PCM could remain latent and grow to the point of failure, which, under certain phases of flight, could be catastrophic. For these reasons, we have determined that this AD is necessary to maintain safety of the fleet and will not be withdrawn. Further, the inspection reports required by this AD will enable the manufacturer to obtain better insight into the nature, cause, and extent of the cracking, and to possibly develop final action to address the unsafe condition. Once final action has been identified, we may consider further rulemaking. \n\nRecommendation to Develop In-Flight Procedures to Deal with a Failed PCM \n\n\tAir Line Pilots Association (ALPA) recommends that procedures to deal with an in-flight situation of a failed rudder PCM be developed and provided to the flightcrews. ALPA states that this procedure would aid pilot workload in the event of a failed rudder PCM. ALPA submitted the same comment to the docket for AD 2003-23-01, asserting that "industry must develop a set of operational procedures to allow flightcrews to deal with such an in-flight situation." ALPA states that no such procedures have yet been provided and reiterates its recommendation that industry supply such procedures. \n\n\tWe acknowledge ALPA's concern. We understand that any such procedures would be provided by industry; in this case, Boeing. However, we have concluded, and Boeing concurs, that the repetitive inspections required by this AD will detect any cracking or potential cracking of the PCM before any PCM failure. Therefore, non-normal operational procedures are not needed to maintain fleet safety in this regard. As ALPA did not request any specific change to the NPRM, we have not changed the AD as regards this comment. \n\nRequest to Reduce Compliance Time \n\n\tThe same commenter, ALPA, requests that we change the compliance time of the NPRM from 24 months to 12 months. ALPA states that the potential hazard for an "uncommanded rudder hardover, consequent increased pilot workload, and possible runway departure upon landing" warrants a more conservative initial inspection period. ALPA asserts that allowing a longer initial time period may allow failed yaw damper actuators to remain in operation much longer than necessary and put may aircraft at risk of experiencing a failure similar to the one on the incident airplane. \n\n\tWe do not agree. AD 2003-23-01 has already required the inspection of Model 747-400 airplanes with suspected high usage rudder PCMs, and the compliance period to complete the original inspections has passed with no additional failures detected. This, along with the knowledge the rudder PCMs have undergone extensive investigation, provides us with a degree of confidence that there are no imminent failures predicted. Instead, we have determined that on-going inspections are needed because the root cause for the premature fatigue failure on the incident airplane has not been determined. Further, this AD is intended to protect against a failure condition not previously analyzed: failure of the upper rudder PCM. The existing initial compliance time of 24 months provides a balance between further possible failures due to the unknown cause of the failed part and the additional burden of on-going inspections. No revision is needed to the AD in this matter. \n\nClarification of Parts Installation Paragraph \n\n\tThe clear intent of this AD is that PCMs having cracked manifolds must be removed from service and replaced with serviceable PCMs having manifolds without cracks. To prevent confusion and ensure conformity with the intent of the AD, we have added the phrase "and found to be without cracks" to paragraph (l) of the AD. \n\nConclusion \n\n\tWe have reviewed the available data, including the comments that have been received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We have determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nInterim Action \n\n\tBecause the root cause of the cracking addressed in AD 2003-23-01 has not yet been determined, we consider this AD to be interim action and have continued the requirement to return cracked PCMs or manifolds to Parker Hannifin in paragraph (j)(2) of this AD. If final action is later identified, we may consider further rulemaking then. \n\nCosts of Compliance \n\n\tThere are approximately 636 airplanes of the affected design in the worldwide fleet. We estimate that 86 airplanes of U.S. registry will be affected by this AD, and that it will take approximately 4 work hours per airplane to accomplish the ultrasonic inspection, at an average labor rate of $65 per work hour. Based on these figures, the cost impact of the inspection is estimated to be $22,360, or $260 per airplane, per inspection cycle. \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\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 findsnecessary 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 have determined 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\n\tFor the reasons discussed above, I certify that this AD:\n \n\t(1) Is not a "significant regulatory action" under Executive Order 12866; \n\n\t(2) Is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and \n\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 FlexibilityAct. \n\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 39-13364 (68 FR 64263, November 13, 2003) and adding the following new airworthiness directive (AD):