2016-11170. Airworthiness Directives; The Boeing Company Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

We propose to supersede Airworthiness Directive (AD) 2009-21-01, which applies to certain Boeing Model 737-300 and 737-400 series airplanes. AD 2009-21-01 currently requires repetitive inspections to detect cracking of the aft fuselage skin, and related investigative and corrective actions if necessary. Since we issued AD 2009-21-01, an evaluation by the design approval holder (DAH) indicates that the aft fuselage skin is subject to widespread fatigue damage (WFD). This proposed AD would add new aft fuselage skin inspections for cracking, inspections to detect missing or loose fasteners and any disbonding or cracking of bonded doublers, permanent repairs of time-limited repairs, related investigative and corrective actions if necessary, and skin panel replacement. The proposed AD also removes Model 737-400 series airplanes from the applicability. We are proposing this AD to detect and correct cracking in the aft fuselage skin along the longitudinal edges of the bonded skin doubler, which could result in possible rapid decompression and reduced structural integrity of the airplane.

DATES:

We must receive comments on this proposed AD by June 27, 2016.

ADDRESSES:

You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: [phone].
• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE., Washington, DC 20590.
• Hand Delivery: Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this NPRM, contact Boeing Commercial Airplanes, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, WA 98124-2207; telephone: [phone], extension 1; fax: [phone]; 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. It is also available on the Internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2016-6667.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2016-6667; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (phone: [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Wade Sullivan, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office (ACO), 1601 Lind Avenue SW., Renton, WA 98057-3356; phone: [phone]; fax: [phone]; email: [e-mail].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2016-6667; Directorate Identifier 2015-NM-125-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because of those comments.

We will post all comments we receive, without change, to http://www.regulations.gov,, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this proposed AD.

Discussion

Fatigue damage can occur locally, in small areas or structural design details, or globally, in widespread areas. Multiple-site damage is widespread damage that occurs in a large structural element such as a single rivet line of a lap splice joining two large skin panels. Widespread damage can also occur in multiple elements such as adjacent frames or stringers. Multiple-site damage and multiple-element damage cracks are typically too small initially to be reliably detected with normal inspection methods. Without intervention, these cracks will grow, and eventually compromise the structural integrity of the airplane. This condition is known as widespread fatigue damage. It is associated with general degradation of large areas of structure with similar structural details and stress levels. As an airplane ages, WFD will likely occur, and will certainly occur if the airplane is operated long enough without any intervention.

The FAA's WFD final rule (75 FR 69746, November 15, 2010) became effective on January 14, 2011. The WFD rule requires certain actions to prevent structural failure due to WFD throughout the operational life of certain existing transport category airplanes and all of these airplanes that will be certificated in the future. For existing and future airplanes subject to the WFD rule, the rule requires that DAHs establish a limit of validity (LOV) of the engineering data that support the structural maintenance program. Operators affected by the WFD rule may not fly an airplane beyond its LOV, unless an extended LOV is approved.

The WFD rule (75 FR 69746, November 15, 2010) does not require identifying and developing maintenance actions if the DAHs can show that such actions are not necessary to prevent WFD before the airplane reaches the LOV. Many LOVs, however, do depend on accomplishment of future maintenance actions. As stated in the WFD rule, any maintenance actions necessary to reach the LOV will be mandated by airworthiness directives through separate rulemaking actions.

In the context of WFD, this action is necessary to enable DAHs to propose LOVs that allow operators the longest operational lives for their airplanes, and still ensure that WFD will not occur. This approach allows for an implementation strategy that provides flexibility to DAHs in determining the timing of service information development (with FAA approval), while providing operators with certainty regarding the LOV applicable to their airplanes.

On September 25, 2009, we issued AD 2009-21-01, Amendment 39-16038 (74 FR 52395, October 13, 2009) (“AD 2009-21-01”), for certain Boeing Model 737-300 and 737-400 series airplanes. AD 2009-21-01 requires repetitive inspections to detect cracking of the aft fuselage skin, and related investigative and corrective actions if necessary. AD 2009-21-01 resulted from reports of cracks in the aft fuselage skin on both sides of the airplane. We issued AD 2009-21-01 to detect and correct cracking in the aft fuselage skin along the longitudinal edges of the bonded skin doubler, which could result in reduced structural integrity of the airplane.

Actions Since AD 2009-21-01 Was Issued

Since we issued AD 2009-21-01, additional cracks have been found on airplanes in the skin panels from station 727 to station 1016 and from stringer S-14 to stringer S-25 on the left and right sides of the airplanes. Cracks at fastener holes in the bonded doubler have also been reported on several airplanes in the area above stringer S-17 on the left and right side of the airplanes.

An evaluation by the DAH indicates that the aft fuselage skin is subject to WFD. On the existing skin panel assemblies, the doubler is chemically milled to create pockets of various depths. At these skin panel locations on the airplane, the loads could cause a condition where cracks could form along the longitudinal edges of the doubler.

AD 2009-21-01 applies to certain Boeing Model 737-300 and 737-400 series airplanes. This proposed AD is applicable to certain Model 737-300 series airplanes. We are considering issuing additional rulemaking that will apply to Model 737-400 series airplanes. We have determined that, in this case, a less burdensome approach is to issue separate ADs applicable only to each model type.

Related Service Information Under 1 CFR Part 51

We reviewed Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015. The service information describes procedures for doing inspections of the fuselage skin, repairs, and skin panel replacement. This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.

FAA's Determination

We are proposing this AD because we evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design.

Proposed AD Requirements

Although this proposed AD does not explicitly restate the requirements of AD 2009-21-01, this proposed AD would retain all of the requirements of AD 2009-21-01 for Model 737-300 series airplanes, except the skin panel replacement is terminating action only if the skin panel replacement is done with a production skin panel after 53,000 total flight cycles. Those requirements are referenced in the service information identified previously, which, in turn, is referenced in paragraphs (g) and (h) of this proposed AD. This proposed AD would require accomplishing the actions specified in the service information described previously, except as discussed under “Differences Between this Proposed AD and the Service Information.” For information on the procedures and compliance times, see this service information at http://www.regulations.gov by searching for and locating Docket No. FAA-2016-6667.

The phrase “related investigative actions” is used in this proposed AD. “Related investigative actions” are follow-on actions that (1) are related to the primary action, and (2) further investigate the nature of any condition found. Related investigative actions in an AD could include, for example, inspections.

The phrase “corrective actions” is used in this proposed AD. “Corrective actions” are actions that correct or address any condition found. Corrective actions in an AD could include, for example, repairs.

Differences Between This Proposed AD and the Service Information

Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, specifies to contact the manufacturer for instructions on how to repair certain conditions and also to obtain certain work instructions, but this proposed AD would require repairing those conditions and also to obtain those work instructions in one of the following ways:

• In accordance with a method that we approve; or
• Using data that meet the certification basis of the airplane, and that have been approved by the Boeing Commercial Airplanes Organization Designation Authorization (ODA) whom we have authorized to make those findings.

Table 6 of paragraph 1.E., “Compliance,” of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, specifies post-repair airworthiness limitation inspections in compliance with 14 CFR 25.571(a)(3) at the repaired locations, which support compliance with 14 CFR 121.1109(c)(2) or 129.109(b)(2). As airworthiness limitations, these inspections are required by maintenance and operational rules. It is therefore unnecessary to mandate them in this AD. Deviations from these inspections require FAA approval, but do not require an alternative method of compliance. This difference has been coordinated with Boeing.

Explanation of Compliance Time

The compliance time for the modification specified in this proposed AD for addressing WFD was established to ensure that discrepant structure is modified before WFD develops in airplanes. Standard inspection techniques cannot be relied on to detect WFD before it becomes a hazard to flight. We will not grant any extensions of the compliance time to complete any AD-mandated service bulletin related to WFD without extensive new data that would substantiate and clearly warrant such an extension.

Costs of Compliance

We estimate that this proposed AD affects 168 airplanes of U.S. registry.

We estimate the following costs to comply with this proposed AD:

Estimated Costs

Action	Labor cost	Parts cost	Cost per product	Cost on U.S. operators
Inspections	Up to 1,791 work-hours × $85 per hour = $152,235	$0	Up to $152,235	Up to $25,575,480.
Skin replacement	624 work-hours × $85 per hour = $53,040	$98,275	$151,315	$25,420,920.

We estimate the following costs to do any necessary repairs that would be required based on the results of the proposed inspections. We have no way of determining the number of aircraft that might need these repairs:

On-Condition Costs

Action	Labor cost	Parts cost	Cost per product
Time limited repair	24 work-hours × $85 per hour = $2,040 per repair	[1]	$2,040 per repair.
Permanent repair	Up to 43 work-hours × $85 per hour = $3,655 per repair	[1]	Up to $3,655 per repair.
[1] We have received no definitive data that would enable us to provide the part cost estimates for the on-condition actions specified in this proposed AD.

We estimate the following costs to do any necessary post-repair inspections that would be required. We have no way of determining the number of aircraft that might need these inspections:

Post-Repair Inspection Costs

Action	Labor cost	Parts cost	Cost per product
Post-repair inspection	Up to 7 work-hours × $85 per hour = $595	$0	Up to $595.

Authority for This Rulemaking

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.

Regulatory Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would 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 the proposed regulation:

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

(2) Is not a “significant rule” under the 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.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• Safety

The Proposed Amendment

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

PART 39—AIRWORTHINESS DIRECTIVES

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

Authority: 49 U.S.C. 106(g), 40113, 44701.

§ 39.13

[Amended]

2. The FAA amends § 39.13 by removing Airworthiness Directive (AD) 2009-21-01, Amendment 39-16038 ( 74 FR 52395, October 13, 2009), and adding the following new AD:

The Boeing Company: Docket No. FAA-2016-6667; Directorate Identifier 2015-NM-125-AD.

(a) Comments Due Date

The FAA must receive comments on this AD action by June 27, 2016.

(b) Affected ADs

This AD replaces AD 2009-21-01, Amendment 39-16038 (74 FR 52395, October 13, 2009) (“AD 2009-21-01”).

(c) Applicability

This AD applies to Boeing Model 737-300 series airplanes, certificated in any category, as identified in Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015.

(d) Subject

Air Transport Association (ATA) of America Code 53, Fuselage.

(e) Unsafe Condition

This AD was prompted by an evaluation by the design approval holder (DAH) indicates that the aft fuselage skin is subject to widespread fatigue damage (WFD). We are issuing this AD to detect and correct cracking in the aft fuselage skin along the longitudinal edges of the bonded skin doubler, which could result in possible rapid decompression and reduced structural integrity of the airplane.

(f) Compliance

Comply with this AD within the compliance times specified, unless already done.

(g) Inspections, Related Investigative and Corrective Actions

At the applicable times specified in tables 1 and 2 of paragraph 1.E., “Compliance,” of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, except as required by paragraph (h)(1) and (h)(2) of this AD: Do the applicable inspections to detect cracks in the aft fuselage skin panels; and do all applicable related investigative and corrective actions; in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, except as required by paragraphs (h)(3) and (h)(4) of this AD. Do all applicable related investigative and corrective actions before further flight. Repeat the applicable inspections thereafter at the applicable intervals specified in tables 1 and 2 of paragraph 1.E., “Compliance,” of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015. Accomplishment of a repair in accordance with “Part 4: Repair” of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, except as required by paragraph (h)(3) of this AD, is terminating action for the repetitive inspections required by this paragraph at the repaired locations only.

(h) Exceptions to Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, Dated June 3, 2015

(1) Where Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, specifies compliance times “after the Revision 4 date of this service bulletin,” this AD requires compliance within the specified compliance times after the effective date of this AD.

(2) The Condition column of Paragraph 1.E., “Compliance,” of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, refers to airplanes in certain configurations as of the “issue date of Revision 4 of this service bulletin.” However, this AD applies to airplanes in the specified configurations “as of the effective date of this AD.”

(3) Where Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, specifies contacting Boeing for repair instructions or work instructions, before further flight, repair or perform the work instructions using a method approved in accordance with the procedures specified in paragraph (n) of this AD, except as required by paragraph (h)(4) of this AD.

(4) For airplanes on which an operator has a record that a skin panel was replaced with a production skin panel before 53,000 total flight cycles: At the applicable time for the next inspection as specified in tables 1 and 2 of paragraph 1.E., “Compliance,” Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, except as provided by paragraph (h)(1) and (h)(2) of this AD: Perform inspections and applicable corrective actions using a method approved in accordance with the procedures specified in paragraph (n) of this AD.

(i) Actions for Airplanes With a Time Limited Repair Installed

(1) For airplanes with a time limited repair installed as specified in Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 2006: At the applicable times specified in table 3 of paragraph 1.E., “Compliance,” of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, except as provided by paragraphs (h)(1) and (h)(2) of this AD: Do the actions specified in paragraphs (i)(1)(i) and (i)(1)(ii) of this AD.

(i) Do the applicable inspections to detect missing or loose fasteners and any disbonding or cracking of bonded doublers; and do all applicable related investigative and corrective actions; in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, except as required by paragraph (h)(3) of this AD. Do all applicable related investigative and corrective actions before further flight. Repeat the applicable inspections thereafter at the applicable intervals specified Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015.

(ii) Make the time limited repair permanent; and do all applicable related investigative and corrective actions; in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, except as required by paragraph (h)(3) of this AD. Do all applicable related investigative and corrective actions before further flight. Accomplishing the permanent repair required by this paragraph terminates the inspections required by paragraph (i)(1)(i) of this AD for the permanently repaired area only.

(2) For airplanes with a time limited repair installed as specified in Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015: At the applicable times specified in table 4 of paragraph 1.E., “Compliance,” of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015: Do the actions specified in paragraphs (i)(2)(i) and (i)(2)(ii) of this AD.

(i) Do the applicable inspections to detect missing or loose fasteners and any disbonding or cracking of bonded doublers; and do all applicable related investigative and corrective actions; in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, except as required by paragraph (h)(3) of this AD. Do all applicable related investigative and corrective actions before further flight. Repeat the applicable inspections thereafter at the applicable intervals specified in table 4 of paragraph 1.E., “Compliance,” of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015.

(ii) Make the time limited repair permanent; and do all applicable related investigative and corrective actions; in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, except as required by paragraph (h)(3) of this AD. Do all applicable related investigative and corrective actions before further flight. Accomplishing the permanent repair required by this paragraph terminates the inspections required by paragraph (i)(2)(i) of this AD for the permanently repaired area only.

(j) Modification of Certain Permanent Repairs

For airplanes with an existing time limited repair that was made permanent as specified in Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 2006: At the applicable times specified in table 5 of paragraph 1.E., “Compliance,” of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, except as provided by paragraphs (h)(1) of this AD: Modify the existing permanent repair; and do all applicable related investigative and corrective actions; in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, except as required by paragraph (h)(3) of this AD. Do all applicable related investigative and corrective actions before further flight.

(k) Post-Repair Inspections

Table 6 of paragraph 1.E., “Compliance,” of Boeing Service Bulletin Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015, specifies post-repair airworthiness limitation inspections in compliance with 14 CFR 25.571(a)(3) at the repaired locations, which support compliance with 14 CFR 121.1109(c)(2) or 129.109(b)(2). As airworthiness limitations, these inspections are required by maintenance and operational rules. It is therefore unnecessary to mandate them in this AD. Deviations from these inspections require FAA approval, but do not require an alternative method of compliance.

(l) Skin Panel Replacement

At the later of the times specified in paragraphs (l)(1) and (1)(2) of this AD: Replace the applicable skin panels, and do all applicable related investigative and corrective actions, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1168, Revision 4, dated June 3, 2015. Do all applicable related investigative and corrective actions before further flight. Doing the skin panel replacement required by this paragraph terminates the inspection requirements of paragraphs (g), (i), and (j) of this AD for that skin panel only, provided the skin panel replacement was done with a production skin panel after 53,000 total flight cycles.

(1) Before 60,000 total flight cycles, but not before 53,000 total flight cycles.

(2) Within 6,000 flight cycles after the effective date of this AD, but not before 53,000 total flight cycles.

(m) Credit for Previous Actions

(1) This paragraph provides credit for the actions required by paragraph (g) of this AD, if those actions were performed before the effective date of this AD using Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 2006, except as required by paragraph (h)(4) of this AD. Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 2006, was incorporated by reference in AD 2009-21-01.

(2) This paragraph provides credit for the actions required by paragraph (l) of this AD, if those actions were performed before the effective date of this AD using Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 2006, except as required by paragraph (h)(4) of this AD; provided the skin panel replacement was done with a production skin panel after 53,000 total flight cycles. Boeing Service Bulletin 737-53-1168, Revision 3, dated November 28, 2006, was incorporated by reference in AD 2009-21-01.

(3) This paragraph provides credit for the actions required by paragraph (l) of this AD, if those actions were performed before November 17, 2009 (the effective date of AD 2009-21-01), using any service information specified in paragraphs (m)(3)(i), (m)(3)(ii), and (m)(3)(iii) of this AD, except as required by paragraph (h)(4) of this AD; provided the skin panel replacement was done with a production skin panel after 53,000 total flight cycles. The service information specified in paragraphs (m)(3)(i), (m)(3)(ii), and (m)(3)(iii) of this AD are not incorporated by reference in this AD.

(i) Part 3 of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1168, dated March 16, 1995.

(ii) Part 3 of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1168, Revision 1, dated August 17, 1995.

(iii) Part 3 of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1168, Revision 2, dated November 27, 1996.

(n) Alternative Methods of Compliance (AMOCs)

(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the manager of the ACO, send it to the attention of the person identified in paragraph (o)(1) of this AD. Information may be emailed to: [e-mail].

(2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district office.

(3) An AMOC that provides an acceptable level of safety may be used for any repair, modification, or alteration required by this AD if it is approved by the Boeing Commercial Airplanes Organization Designation Authorization (ODA) that has been authorized by the Manager, Seattle ACO, to make those findings. To be approved, the repair method, modification deviation, or alteration deviation must meet the certification basis of the airplane and the approval must specifically refer to this AD.

(4) AMOCs approved previously for repairs for AD 2009-21-01 are approved as AMOCs for the corresponding provisions of paragraph (g) of this AD.

(5) AMOCs approved for previous modifications done as optional terminating action for AD 2009-21-01 are approved as AMOCs for the modification required by paragraph (l) of this AD provided the previous modification was done after the airplane had accumulated 53,000 total flight cycles or more.

(o) Related Information

(1) For more information about this AD, contact Wade Sullivan, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle ACO, 1601 Lind Avenue SW., Renton, WA 98057-3356; phone: [phone]; fax: [phone]; email: [e-mail].

(2) 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: [phone], extension 1; fax: [phone]; 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.

Issued in Renton, Washington, on May 4, 2016.

Michael Kaszycki,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.