AD 2013-26-12

This AD is effective February 10, 2014.

The Director of the Federal Register approved the incorporation by reference of certain publications listed in this AD as of February 10, 2014.

For service information identified in this AD, contact Boeing Commercial Airplanes, Attention: Data & Services Management, P. O. Box 3707, MC 2H-65, Seattle, WA 98124-2207; telephone 206-544-5000, extension 1; fax 206-766-5680; Internet https://www.myboeingfleet.com. You may view this referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, WA. For information on the availability of this material at the FAA, call 425-227-1221.

Bill Ashforth, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office (ACO), 1601 Lind Avenue SW., Renton, WA 98057-3356; phone: 425-917-6432; fax: 425-917-6590; email: Bill.Ashforth@faa.gov.

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2009-14-02, Amendment 39-15951 (74 FR 30919, June 29, 2009). AD 2009-14-02 applied to the specified products. The NPRM published in the Federal Register on July 3, 2013 (78 FR 40050). The NPRM proposed to continue to require repetitive inspections for wear damage and cracks of the fuselage skin in the interface area of the vertical stabilizer seal and fuselage skin, a detailed inspection for wear damage and cracks of the surface of any skin repair doubler in the area, and corrective actions if necessary. For airplanes on which the fuselage skin has been blended to remove wear damage, AD 2009-14-02 also required repetitive external detailed inspections or high frequency eddy current inspections for cracks of the blended area of the fuselage skin, and corrective actions if necessary. That NPRM also proposed to reduce the repetitive inspection interval, change certain corrective actions, and expand the applicability.

We gave the public the opportunity to participate in developing this AD. The following presents the comments received on the proposal (78 FR 40050, July 3, 2013) and the FAA's response to each comment.

Boeing requested we revise the terminating action title of paragraph (i) of the NPRM (78 FR 40050, July 3, 2013) by removing the word “Optional.” Boeing stated that Boeing Alert Service Bulletin 747-53A2478, Revision 3, dated October 17, 2011, specifies that if any crack is found or if wear damage is greater than the limit allowed, rub strips must be installed in accordance with Boeing Service Bulletin 747-53-2721, Revision 2, dated March 17, 2011. Boeing commented that in this case, the terminating action is not optional.

We do not agree with the commenter's request. We agree that in cases where any damage is found outside the limits allowed by Boeing Alert Service Bulletin 747-53A2478, Revision 3, dated October 17, 2011, rub strips are required to be installed as described in that service bulletin.

We disagree with removing the word “optional” in the title of paragraph (i) of this final rule, because the current wording in paragraphs (g) and (h) of this final rule requires the operators to do all applicable corrective actions in accordance with, and at the compliance times specified in, Boeing Alert Service Bulletin 747-53A2478, Revision 3, dated October 17, 2011. This wording in paragraphs (g) and (h) of this final rule requires installing rub strips as described in Boeing Service Bulletin 747-53-2721, Revision 2, dated March 17, 2011, before further flight if the damage is found to be outside the limits permitted as described in the service repair manual (SRM). Paragraph (i) of this final rule is provided to give the operators the option to install the rub strips as described in Boeing Service Bulletin 747-53-2721, Revision 2, dated March 17, 2011, at any time. Doing the installation of the rub strips in accordance with Boeing Service Bulletin 747-53-2721, Revision 2, dated March 17, 2011, is a terminating action for the work given in Boeing Alert Service Bulletin 747-53A2478, Revision 3, dated October 17, 2011, at the locations of the rub strip installation only. We have not changed this final rule in this regard.

Boeing and All Nippon Airways (ANA) requested we revise paragraphs (i) and (j)(3) of the NPRM (78 FR 40050, July 3, 2013) to reference the latest revision level of the referenced service information, which is Boeing Service Bulletin 747-53-2721, Revision 3, dated June 25, 2013.

Boeing requested we revise paragraph (k)(2) of the NPRM (78 FR 40050, July 3, 2013) to give credit for actions done prior to the effective date of this AD using Boeing Service Bulletin 747-53-2721, Revision 2, dated March 17, 2011.

We agree with the commenters' requests. Boeing Service Bulletin 747-53-2721, Revision 3, dated June 25, 2013, clarifies the post-modification and post-repair inspection requirements and transfers post-repair inspection instructions from the SRM and repair assessment guidelines to this service bulletin for airplanes that have the zone 1 full length repair installed. We have changed paragraphs (i) and (j)(3) of this final rule to reference Boeing Service Bulletin 747-53-2721, Revision 3, dated June 25, 2013.

We also have added Boeing Service Bulletin 747-53-2721, Revision 2, dated March 17, 2011, to paragraph (k) of this final rule to provide credit for the actions specified in paragraph (i) of this final rule, if the corresponding actions were performed before the effective date of this final rule using this service bulletin. We revised paragraph (k) by adding subparagraphs (k)(2)(i) through (iii).

Qantas Airways Limited (QAN) requested that we allow it to continue with the inspection program mandated in AD 2009-14-02, Amendment 39-15951 (74 FR 30919, June 29, 2009), as an alternative method of compliance (AMOC) to the actions specified in the NPRM (78 FR 40050, July 3, 2013). The FAA interprets this as a request to withdraw the NPRM and not supersede AD 2009-14-02. QAN commented that it understands the FAA's concern over the report of wear damage at earlier times than the AD 2009-14-02 inspection mandates. QAN stated that its fleet utilization and related extensive service experience with robust data collection on repetitive inspection results since the AD 2009-14-02 compliance period commenced support the adequacy of the repetitive inspection interval of 7,500 flight hours in AD 2009-14-02. QAN also stated that minor wear damage in its fleet remains under SRM-allowable rework limits.

We do not agree with the commenter's request. The service and analytical data from the airplane manufacturer do not support the request to keep the current mandated repetitive inspection thresholds required by AD 2009-14-02, Amendment 39-15951 (74 FR 30919, June 29, 2009). An operator has reported wear through the fuselage skin between body station (STA) 2598 and STA 2638, stringers S-2L to S-3L. The wear developed in less than 3,657 flight hours since the previous inspection, which was less than the repetitive inspection interval given in Boeing Alert Service Bulletin 747-53A2478, Revision 2, dated July 15, 2010. The wear occurred through both the Teflon-filled coating and the full thickness of the 0.050-inch-thick skin to create a hole approximately 16 inches in length.

In developing the compliance times for this final rule, we considered not only the safety implications of the identified unsafe condition, but the average utilization rate of the affected fleet and the practical aspects of an orderly inspection, repair, and modification of the fleet during regular maintenance periods. We have considered the commenter's request, and we have concluded that the proposed repetitive compliance times remain appropriate. However, under the provisions of paragraph (l) of this AD, we may consider requests for approval of an AMOC if sufficient data are submitted to substantiate that an alternative inspection plan would provide an acceptable level of safety. We have not changed this final rule in this regard.

QAN requested clarification on the rate of wear damage and the compliance times specified in the NPRM (78 FR 40050, July 3, 2013). QAN noted that on the airplanes that have not started the inspections described in Boeing Alert Service Bulletin 747-53A2478, Revision 2, dated July 15, 2010, the compliance time for the initial inspection is 20,000 total flight hours. QAN also noted that, on the airplanes that have started the inspections described in Boeing Alert Service Bulletin 747-53A2478, Revision 2, dated July 15, 2010, the initial inspection compliance time is reduced to 2,000 or 3,000 flight hours, depending on the condition. QAN stated that, based on the inspection program in AD 2009-14-02, Amendment 39-15951 (74 FR 30919, June 29, 2009), it understands that the rate at which the wear damage develops is a primary concern to the FAA.

We agree to clarify. We agree with QAN that the AD 2009-14-02, Amendment 39-15951 (74 FR 30919, June 29, 2009), inspection program rate at which the wear damage developed is a primary concern because at least one operator has reported wear through the fuselage skin in less than 3,657 flight hours after a mandatory inspection, but before the specified repetitive inspection interval of 7,500 flight hours or 6,000 flight hours. However, we do not agree with the commenter that the 20,000-total-flight-hour threshold is reduced. Rather, the initial inspection threshold of 2,000 flight hours is not a reduced threshold as the commenter implied, but is instead a required time by which additional inspections must resume if any inspection has already been accomplished. With the service and analytical data from the airplane manufacturer, a new repetitive inspection program is required, as specified in Boeing Alert Service Bulletin 747-53A2478, Revision 3, dated October 17, 2011. The compliance time depends on when operators have previously inspected their airplanes and the condition of the fuselage skin.

We disagree with QAN that AD 2009-14-02, Amendment 39-15951 (74 FR 30919, June 29, 2009), has an adequate mandated repetitive interval because service history has shown defects reported before the AD 2009-14-02 mandatory repetitive inspection interval. We have not changed this final rule in this regard.

We have revised the Exceptions to Service Information, paragraph (j)(3) of this final rule, to include Boeing Alert Service Bulletin 747-53A2478, Revision 3, dated October 17, 2011.

We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this AD with the changes described previously and minor editorial changes. We have determined that these minor changes:

• Are consistent with the intent that was proposed in the NPRM (78 FR 40050, July 3, 2013) for correcting the unsafe condition; and

• Do not add any additional burden upon the public than was already proposed in the NPRM (78 FR 40050, July 3, 2013).

We also determined that these changes will not increase the economic burden on any operator or increase the scope of this AD.

We estimate that this AD affects 917 airplanes of U.S. registry.

We estimate the following costs to comply with this AD:

We have received no definitive data that would enable us to provide cost estimates for the on-condition actions specified in this AD.

According to the manufacturer, some of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected individuals. We do not control warranty coverage for affected individuals. As a result, we have included all costs in our cost estimate.

Title 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.

We 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.

We 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.

For the reasons discussed above, I certify that this AD:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979),

(3) Will not affect intrastate aviation in Alaska, and

(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.

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows:

1. The authority citation for part 39 continues to read as follows:

2. The FAA amends § 39.13 by removing Airworthiness Directive (AD) 2009-14-02, Amendment 39-15951 (74 FR 30919, June 29, 2009), and adding the following new AD: