06-3066. Airworthiness Directives; Boeing Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Final rule.

SUMMARY:

The FAA is adopting a new airworthiness directive (AD) for all Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD requires a one-time inspection for scribe lines and cracks in the fuselage skin at certain lap joints, butt joints, external repair doublers, and other areas; and related investigative/corrective actions if necessary. This AD results from reports of fuselage skin cracks adjacent to the skin lap joints on airplanes that had scribe lines. Scribe line damage can also occur at many other locations, including butt joints, external doublers, door scuff plates, the wing-to-body fairing, and areas of the fuselage where decals have been applied or removed. We are issuing this AD to prevent rapid decompression of the airplane due to fatigue cracks resulting from scribe lines on pressurized fuselage structure.

DATES:

This AD becomes effective May 5, 2006.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in the AD as of May 5, 2006.

ADDRESSES:

You may examine the AD docket on the Internet at http://dms.dot.gov or in person at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, room PL-401, Washington, DC.

Contact Boeing Commercial Airplanes, PO Box 3707, Seattle, Washington 98124-2207, for service information identified in this AD.

FOR FURTHER INFORMATION CONTACT:

Sue Lucier, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office (ACO), 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Examining the Docket

You 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 [phone]) is located on the plaza level of the Nassif Building at the street address stated in the ADDRESSES section.

Discussion

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to all Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That NPRM was published in the Federal Register on April 29, 2005 (70 FR 22272). That NPRM proposed to require a one-time inspection for scribe lines and cracks in the fuselage skin at certain lap joints, butt joints, external repair doublers, and other areas; and related investigative/corrective actions if necessary.

Comments

We provided the public the opportunity to participate in the development of this AD. We have considered the comments received.

Support for Proposed AD

One commenter (AWAS Aviation Services) agrees that fatigue cracks on the fuselage should be addressed in a suitable time period. The commenter considers the proposed compliance time acceptable.

Request To Consider Similar Rulemaking for Other Airplanes

The National Transportation Safety Board (NTSB) believes that the proposed AD will address scribe-type damage on the affected airplanes in a timely manner. However, the NTSB is concerned that this type of damage is not limited to those airplanes, but could be present on virtually every pressurized airplane currently in service. The NTSB urges the FAA to examine similar rulemaking for other makes and models of pressurized airplanes.

We acknowledge the NTSB's concerns. This is a long-term durability issue that is not limited to any particular aircraft model. The effect on each aircraft model will vary with each model's design characteristics and the conditions to which they may be operated. In support of this, we have been in contact with other governing regulatory agencies and other manufacturers, and we may consider further rulemaking applicable to other airplanes as a result of these efforts.

Request To Allow SRM for Repairs

For repairing “typical” scribed areas, this proposed AD would require operators to contact the FAA for approval of repairs. One commenter (USAir) asserts that the Boeing 737 Structural Repair Manual (SRM) provides several repair schemes for localized damage at typical scribed areas, and that omitting the SRM as a repair option could result in many requests for alternative methods of compliance (AMOCs). Another commenter (Japan Transocean Air) requests approval of the SRM for instructions for permanent rework of tactile marks, if the SRM revises the allowable damage limits for fuselage skin.

We disagree with the requests. Merely repairing the detected scribe lines may be inadequate to address the identified unsafe condition. Scribe damage has been found to exceed well beyond the region where it was originally discovered by visual inspection. Current SRM repairs may not be adequate because of the nature of damage caused by scribes. Scribe damage is widespread, frequently concealed by the upper skin of a lap splice, and thus difficult or impossible to detect. At this time, the SRM repairs for the scribed areas do not address the widespread nature of this type of damage and the follow-up inspections that may be required and therefore cannot be used. We are currently working with Boeing to develop repair schemes that may address this issue. These efforts may result in additional FAA methods of compliance that provide clarification and relief in future but are not available at this time. We have not changed the final rule regarding this issue.

Request To Allow Other Service Information for Repairs

One commenter (USAir) suggests that incorporation of Boeing Service Bulletin 737-53A1177, 737-53-1168, or 737-53-1187, which would remove scribe lines from the entire skin panel, would terminate the repetitive inspections of the area. Further, since these service bulletins are FAA approved and available, the commenter requests that we revise the proposed AD to require operators to repair all discrepancies found during the scribe line inspections in accordance with an approved FAA method; or, alternatively, in accordance with Service Bulletin 737-53A1177, 737-53-1168, or 737-53-1187, which would terminate the repetitive inspections of the repaired areas.

We partially agree with the requests. Service Bulletins 737-53A1177, 737-53-1168, and 737-53-1187, which were developed to address a specific unsafe condition, involve a significant level of complexity. The actions specified in the service bulletins might be adequate to terminate the repetitive inspections in certain areas; we may consider a fleetwide AMOC presented by the manufacturer as acceptable for terminating action. In the meantime, we may approve individual operator requests for alternative repair methods under the provisions of paragraph (p) in this final rule, if the requests include data that prove that the alternative method would provide an acceptable level of safety.

Request To Revise Cost Estimates

Several commenters (USAir, Alaska Airlines, America West, and KLM) allege that the figures provided in the Costs of Compliance section of the proposed AD do not accurately reflect the actual cost to the airline industry. The commenters assert that most airplanes will need the exterior paint stripped, and the surface prepared for inspection and repainted. These additional actions will add considerable downtime to the inspection required by this proposed AD. One commenter suggests that either the Limited Return to Service (LRTS) should be made less complex or the work hours necessary for planning and engineering should be considered in the cost estimates. The commenters add that the cost estimates do not include the cost to repeat the inspection or do any repairs if scribe lines are found, which would result in additional downtime for the airplanes and a substantial impact on operations. Therefore, the commenters request that we revise the Costs of Compliance section to reflect the whole effect of the proposed AD on operators.

We acknowledge the commenters' concerns and recognize the additional preparatory work that could be involved on some airplanes, but disagree with the requests. While the LRTS is indeed complex, it is not required. This option was intended to provide operators flexibility in deciding the best compliance method for their fleet. Moreover, the cost information included in an AD describes only the direct costs of the specific actions required by the AD. Based on the best data available, the manufacturer provided the number of work hours necessary to do the required actions. We recognize that, in doing the actions required by the AD, operators may incur incidental costs in addition to the direct costs. The cost analysis in AD rulemaking actions, however, typically does not include incidental costs such as the time for planning or handling other administrative actions, or gaining access and closing up. These costs are almost impossible to calculate. Also, the economic analysis of an AD does not consider the costs of conditional actions, such as repairing a crack detected during a required inspection. Such conditional repairs or follow-on actions would be required—regardless of AD direction—to correct an unsafe condition identified in an airplane and to ensure that the airplane is operated in an airworthy condition, as required by the Federal Aviation Regulations.

Request To Refine Definition of “Scribe Line”

Boeing Alert Service Bulletin 737-53A1262, dated December 9, 2004 (cited as the appropriate source of service information for the actions of the proposed AD), describes a scribe line as damage up to 0.006 inch deep. Two commenters (AWAS and Japan Transocean Air) assert that the use of this definition has led to many findings of damage that had no appreciable depth and therefore contributed to no appreciable decrease in fatigue life, yet resources were expended to repair or repetitively inspect this damage to accomplish the actions specified in this service bulletin. Including a minimum depth would eliminate many of these positive findings and allow better use of Boeing and FAA engineering resources and decrease operators' costs. Therefore, the commenters request that a “typical scribe” be further defined by including a minimum measurement limit.

We acknowledge and share these commenters' concerns, but cannot include the definitive criteria that these commenters desire in this final rule because of the complicated nature of the definition of scribe lines. We do agree that a better definition may enhance the inspection process. To this end, we are working with Boeing to develop and present the criteria in a usable format. These efforts may result in additional FAA methods of compliance that provide clarification and relief in the future but are not available at this time. We have not changed the final rule regarding this issue.

Request To Delay AD Pending Issuance of Repair Service Bulletin

The proposed AD does not provide for repairs for scribe marks that are outside the limits of Alert Service Bulletin 737-53A1262. One commenter (Alaska Airlines) notes that Boeing is in the process of developing a new service bulletin that will address many conditions that might be found during the inspection. Therefore, the commenter requests that we delay issuing the final rule until repair procedures are published in a new service bulletin that addresses scribe lines outside the limits addressed in Alert Service Bulletin 737-53A1262. The commenter recommends that the final rule refer to this new, as yet unpublished service bulletin as well as Alert Service Bulletin 737-53A1262 for repair procedures.

We disagree with the request. Boeing has not yet developed a repair service bulletin. To address the unsafe condition in a timely manner, we must proceed with inspection of the fleet for this safety-related damage. When a repair service bulletin becomes available we anticipate it will be approved through the AMOC process. We have not changed the final rule regarding this issue.

Request To Revise Inspection Requirements for Certain Locations

One operator (Alaska Airlines) requests that we revise the proposed AD to exempt the inspection of the area around the wing-to-body fairing if the sealant has been removed in accordance with the procedures in Appendix A of Alert Service Bulletin 737-53A1262. The commenter provides no further explanation or technical justification for the request.

We disagree with the request. The wing-to-body fairings are removed more often than the airplane is stripped and repainted and are therefore subject to many more scribe opportunities. The sealant removal procedures documented in Appendix A were not available before the service bulletin was issued; the subject area therefore will probably have scribe lines. Considering the age of the fleet and the frequency of fairing removal for standard maintenance, this exemption would not apply. We have not changed the final rule regarding this issue.

Request To Clarify Figure References

One commenter (Alaska Airlines) notes an error in the Accomplishment Instructions of Alert Service Bulletin 737-53A1262. The figure cited in Part 8, step 3, should be Figure 39, not Figure 38. The figure cited in Part 9, step 3 [sic], should be Figure 38, not Figure 39.

We acknowledge these errors in the service bulletin; however, the error in Part 9 is in step 4. In this final rule, we have clarified this requirement in new paragraph (j) and renumbered subsequent paragraphs accordingly.

Request To Clarify Certain Compliance Times

One commenter (United Airlines) identifies conflicting compliance times in Alert Service Bulletin 737-53A1262 for the Figure 44 inspections as part of the LRTS plan. The commenter observes that Part 12, item 10.a.(4), recommends doing the Figure 44 inspections between 40,000 and 45,000 flight cycles; however, for airplanes with 40,000 flight cycles, Figure 40 specifies doing a nondestructive test (NDT) inspection before further flight. The commenter requests that we clarify these compliance thresholds.

The compliance times do not conflict with each other but merely refer to different stages of the overall program. Figure 40 is part of the Special Lap Joint inspections, which are required before certain airplane-level scribe inspections; these inspections take place for higher-cycle unmodified airplanes and allow service to extend into the approved 4,500-flight-cycle grace period (as stated in Figure 1 of the service bulletin). The inspections specified in Part 12 of the service bulletin occur after an airplane-level inspection has identified scribe damage. The inspection program in Part 12 allows continued operation with ongoing inspections. Figure 44 identifies additional lap joint inspections affiliated with this program. We have not changed the AD regarding this issue.

Request To Revise Inspection Requirements for Decals

The proposed AD would require inspection of areas where any decal, regardless of size, has been removed. One commenter (United Airlines) requests that we address decals the same way we address external repair doublers for scribe inspections, i.e., that we require inspections only for decal edges with a dimension of 18 inches or longer. The commenter considers that decal damage would be equivalent to a damaged external doubler of the same size.

We disagree with the request. Although the damage from decals may be equivalent, unlike major repairs, decals are easily removable without leaving any indication of their size or location. Additionally, operators may not have detailed records regarding decal application and removal so the extent of possible damage would not be known. However, according to the provisions of paragraph (p) of the final rule, we may approve requests for relief from certain associated requirements, if the operator's records can conclusively determine the decal dimensions and if supporting data are provided that would ensure an acceptable level of safety. We have not changed the final rule regarding this issue.

Requests To Remove Certain Inspection Requirements Under Certain Conditions

The proposed AD would require inspection of the area under the dorsal fin fairing. One commenter (United Airlines) requests that this area be treated the same as the wing-to-body fairing; i.e., if the area under the dorsal fin fairing has never been stripped or repainted since delivery, then the scribe inspection should not be required in that area.

We agree. The area under the dorsal fin fairing is similar to the area under the wing-to-body fairing. We have added new paragraph (k) in this final rule to remove the requirement to inspect that area, under the conditions specified by the commenter. We have reidentified subsequent paragraphs accordingly.

The proposed AD specifies that no inspections would be required where an existing repair covers a potential scribe line, provided the repair spans a minimum of three rows of fasteners beyond each side of the potential scribe line location. One commenter (United Airlines) requests that this provision be revised to allow for a ten-inch extension of the repair beyond the scribe damage, instead of a three-row overlap. The commenter contends that some existing FAA-approved repairs do not meet the three-row criteria. The commenter refers to section 53-00-01, Figure 217, of the Boeing 737 SRM. The commenter states that the proposed AD criteria would add a burden by requiring operators to remove and replace existing FAA-approved repairs.

We disagree with the request to change the inspection requirements for those conditions. Repairs that span less than three rows above and below potential scribed areas will not provide an adequate alternative load path for a lap joint with a scribe. For repairs of locations that do not meet the three-row criteria, this AD requires operators to contact the FAA for options to removing the repair (i.e., through inspections), for which operators may request AMOCs in accordance with paragraph (p) of this AD.

Request To Clarify Provisions for Continued Operation with Scribe Lines

One commenter (America West) requests that we revise the proposed AD to clarify that Part 14 of the service bulletin, while not mandatory, is an FAA-approved method for continued operation if scribe lines are found before the compliance times.

We agree. We have explained this provision in paragraph (g) in this final rule.

Request To Extend Certain Compliance Times

One commenter, an operator (Delta Air Lines), reports that a number of its airplanes have been inspected using procedures developed before Alert Service Bulletin 737-53A1262 was issued. The operator plans to request AMOC approval for these procedures. The commenter raises several questions regarding compliance times for submitting AMOCs and reports (of cracks) for these airplanes, and requests that we revise the proposed AD to require a report within 30 days after the AMOC is approved for those airplanes.

We disagree. Individual operator deviations to the required inspection and reporting procedures may be handled as AMOCs, which operators may request in accordance with paragraph (p) of this AD. We have not changed the final rule regarding this issue.

Request To Clarify Service Bulletin Instructions

Boeing requests that we revise the proposed AD to address some inadvertent omissions in Alert Service Bulletin 737-53A1262.

1. Figure 37 is intended to identify “Restricted Zones” at door cutouts as both the affected structure and Zone 1B. However, Figure 37 does not identify Zone 1B. This information is necessary compliance information for Figure 1, “Compliance Threshold Calculation for Zone 1.”

2. Figure 1, sheets 2 and 3, contain two errors for Areas B, C, and E. Where the service bulletin refers only to “areas where the cutout modification shown in Service Bulletin 737-53A1177 was accomplished,” this text should be followed by “or Zone 1B.” And the phrase “[i]n areas where the cutout modification shown in Service Bulletin 737-53A1177 was not accomplished” should be preceded by “For Zone 1A.” The commenter states that a 4,500-flight-cycle grace period is incorporated into the threshold calculation for locations without potential multisite damage (MSD), and a 1,200-cycle grace period is incorporated into the threshold calculations for locations with potential MSD. Not subject to MSD, Zone 1B locations are subject to the 4,500 cycles grace period only.

We agree with the requested changes. We have clarified these omissions in new paragraphs (l), (m), and (n) in this final rule. These additional paragraphs do not require additional work by any operator; therefore, we do not need to revise the proposed AD to reopen the period for public comment on this issue.

Request To Emphasize Importance of Crack Reports

Boeing requests that we revise the proposed AD to describe the fleet experience of numerous “false positive” indications, i.e., discrepancies that were initially identified as cracks but were upon further analysis determined not to be cracks. Boeing also requests that we recommend that operators submit cracked parts to Boeing for analysis. In support of these requests, Boeing asserts that further analysis of crack findings could change the compliance specifications in Alert Service Bulletin 737-53A1262. Correctly identifying cracks is imperative to reflect actual fleet findings in any future changes to the service bulletin. One operator provided Boeing with nine cut-out samples, which contained positive crack indications based on ultrasonic nondestructive inspections. However, metallurgical analysis revealed no cracks. Boeing emphasizes that potential future changes to the compliance requirements of the service bulletin should be based on confirmed crack findings—not positive crack indications, which may be false positive findings.

We acknowledge Boeing's concerns. But we disagree with the request to require operators to submit cracked parts to Boeing. Although operators may benefit from coordinated efforts to minimize the number of false positive results, requiring operators to send cracked parts to Boeing will add to the costs associated with this AD without further enhancing safety. We have not changed the final rule regarding this issue.

Request To Extend Compliance Time for Reporting

If the inspection reveals any cracks, the proposed AD would require operators to submit a report within 30 days after the inspection. Two operators (Southwest Airlines and America West) speculate that most airplanes will be inspected at a heavy check maintenance facility, and that obtaining the information for the report could take longer than 30 days. The commenters request that we revise the proposed AD to require reports within 30 days after the airplane is returned to service, rather than 30 days after the inspection.

In light of the issue described above, we do not find it appropriate to change this compliance time. The purpose of the report is to gather timely information on crack findings. Heavy checks can take a long time, and delaying the report until the end of the heavy check could defeat the purpose of the report. Further, this AD requires a report only when cracks are found, so a report will likely not be necessary for all airplanes.

Requests To More Accurately Describe Corrective Actions

As written, paragraph (h) of the proposed AD would require operators to repair scribe lines and cracks. Two commenters note that appropriate corrective actions for scribe lines may also include further inspections. Boeing requests that we distinguish the corrective actions in paragraph (h) to identify both inspections and repairs, as applicable. Another commenter (Delta Air Lines) requests that we replace “repair” with “inspection/repair” in paragraph (k)(2) of the proposed AD.

We partially agree that clarification may be necessary. We have revised paragraph (h) accordingly in this final rule. But we cannot revise paragraph (p)(3) (paragraph (k)(2) in the proposed AD) because Boeing authorized representatives for the Boeing Commercial Airplanes Delegation Option Authorization Organization are not delegated to approve changes to inspection programs.

Request To Allow Previous FAA-Approved Repairs

One commenter (Alaska Airlines) requests that we revise the proposed AD to address scribed areas repaired before the effective date of the AD in accordance with a method approved by the FAA. The commenter states that the proposed AD would not allow previously approved repairs for scribe lines as AMOCs.

We agree. New paragraph (p)(4) in this AD provides AMOC credit for repairs approved by the Seattle Aircraft Certification Office (ACO) or a Boeing Company designated engineering representative or authorized representative, via FAA Form 8110-3 or 8100-9 issued before the effective date of this AD, provided the repair plan specifically addressed scribe line damage as stated in the title of the form.

Request To Clarify Requirements for Demonstrating Compliance

One commenter (KLM) notes that the initial inspection thresholds and the LRTS inspection intervals are based on the first scribing opportunity, which the commenter contends is basically the first repainting. The commenter adds that maintenance records may show the dates an airplane has been repainted, but not the order of the repainting (first repainting, second, etc.). The commenter surmises that, if the date of the first repainting cannot be determined, the airplane must be inspected before the airplane accumulates 5,000 total flight cycles. To avoid defaulting to this threshold, the commenter asks how an operator can prove that a certain repainting was the first for a specific airplane. The commenter requests that we revise the proposed AD to include this consideration in the definition of the “first scribing opportunity.”

We disagree with the request. Each operator's system of records will vary in detail, scope, and retrievability; developing a standard protocol would most likely burden rather than help operators. An operator's showing of compliance regarding maintenance records will vary based on whether the operator has owned the airplane since it was delivered from Boeing or purchased it from another source. Any operator who owned the airplane since delivery from Boeing may be able to determine the date of the first repainting and the extent of work performed such as a complete stripping or a scuff-and-paint operation. If the airplane has a maintenance history from a previous owner/operator, then assembling complete repainting records might be more difficult. The level of detail for recording maintenance such as painting varies from operator to operator depending on acceptability by local airworthiness authorities; a standard protocol would be impossible to develop. Individual operators should contact their airworthiness authorities for a showing of compliance. We have not changed the final rule regarding this issue.

Request To Revise Inspection Requirement

One commenter (Air North) requests that the present level of inspection be permitted to monitor the condition of the pressure skin per Boeing SB 737-53A1177 until the lap splice terminating action, at 1200 flight cycles (LFEC), with 250-flight-hour visual inspections.

We have worked extensively with Boeing to align this AD's inspection and LRTS program with existing inspection and modification programs on the 737 Classic fuselage skin. We do not find it necessary to further revise the proposed inspection program. However, under the provisions of paragraph (p) in this final rule, we may approve requests for AMOCs that include data substantiating that the alternative method would provide an acceptable level of safety. We have not changed the final rule regarding this issue.

Request To Advise of Related ADs

One commenter (Delta Air Lines) notes that Part 1, Step 2 (Zone 1 Threshold Determination and Pre-Threshold Special Lap Joint Inspections), of the Work Instructions of Service Bulletin 737-53A1262 refers to “Special Lap Joint Inspections in Paragraph 1.E., Compliance.” The inspections that appear as Special Lap Joint Inspection (1) are related to AD 2002-07-08, amendment 39-12702 (67 FR 17917, April 12, 2002). The inspections that appear as Special Lap Joint Inspection (2) are related to AD 2003-08-15, amendment 39-13128 (68 FR 20341, April 25, 2003).

We infer that the commenter requests that we revise paragraph (b) (“Affected ADs”) of the proposed AD to give credit for actions accomplished as part of other related airworthiness directives. We disagree. Although the actions in all three ADs are the same, the compliance times and in some cases the affected airplanes are different. For some airplanes, the inspections of this AD may be required before the compliance times required by the other cited ADs. If an operator finds that actions accomplished for one AD should be credited to another AD, we will evaluate and approve requests for credit on a case-by-case basis, based on a showing of an acceptable level of safety.

Additional Changes to Proposed AD

We have simplified paragraph (h) in this final rule by referring to the “Alternative Methods of Compliance (AMOCs)” paragraph of this AD for repair methods.

We have revised this action to clarify the appropriate procedure for notifying the principal inspector before using any approved AMOC on any airplane to which the AMOC applies.

Conclusion

We have carefully reviewed the available data, including the comments 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.

Costs of Compliance

There are about 3,132 airplanes of the affected design in the worldwide fleet. The following table provides the estimated costs for U.S. operators to comply with this AD.

Estimated Costs

Zone	Action	Work hours	Average labor rate per hour	Cost per airplane	Number of U.S.- registered airplanes	Fleet cost
1	Sealant removal	66	$65	$4,290	1,384	$5,937,360
	Inspection	4	65	260	1,384	359,840
2	Sealant removal	38	65	2,470	1,384	3,418,480
	Inspection	29	65	1,885	1,384	2,608,840
3	Sealant removal	88	65	5,720	1,384	7,916,480
	Inspection	38	65	2,470	1,384	3,418,480

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 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); and

(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.

We 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.

List of Subjects in 14 CFR Part 39

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

Adoption of the Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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 Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

2006-07-12 Boeing: Amendment 39-14539. Docket No. FAA-2005-20918; Directorate Identifier 2004-NM-269-AD.

Effective Date

(a) This AD becomes effective May 5, 2006.

Affected ADs

(b) None.

Applicability

(c) This AD applies to all Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, certificated in any category.

Unsafe Condition

(d) This AD results from reports of fuselage skin cracks adjacent to the skin lap joints on airplanes that had scribe lines. Scribe line damage can also occur at many other locations, including butt joints, external doublers, door scuff plates, the wing-to-body fairing, and areas of the fuselage where decals have been applied or removed. We are issuing this AD to prevent rapid decompression of the airplane due to fatigue cracks resulting from scribe lines on pressurized fuselage structure.

Compliance

(e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.

Inspection

(f) Do a detailed inspection for scribe lines and cracks in the fuselage skin at certain lap joints, butt joints, external repair doublers, and other areas, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1262, dated December 9, 2004, except as provided by paragraphs (g), (j), (k), (l), (m), and (n) of this AD. Do the actions at the time specified in paragraph 1.E., “Compliance,” of the service bulletin, except as required by paragraph (i) of this AD. Acceptable inspection exemptions are described in paragraph 1.E.1. of Boeing Alert Service Bulletin 737-53A1262.

(1) If no scribe line is found, no further work is required by this AD.

(2) If any scribe line is found: Do all applicable investigative and corrective actions at the time specified by doing all applicable actions specified in the Accomplishment Instructions of the service bulletin, except as required by paragraph (h) of this AD.

Note 1:

A detailed inspection is defined in Note 10 of Boeing Alert Service Bulletin 737-53A1262 under 3.A., “General Information.” Specific magnification requirements may be specified in the steps of the Work Instructions.

Exceptions to and Clarification of Service Bulletin 737-53A1262 Procedures

(g) This AD requires accomplishment of Parts 1 through 11 of Boeing Alert Service Bulletin 737-53A1262, dated December 9, 2004. Parts 12 and 13 of the service bulletin may be accomplished, if applicable, to allow temporary return to service. This AD does not require accomplishment of Part 14 of the service bulletin, although the FAA-approved procedures described in Part 14 are acceptable for continued operation with scribe lines found before the applicable compliance time.

(h) If any scribe line or crack is found during any inspection required by this AD, and Boeing Alert Service Bulletin 737-53A1262, dated December 9, 2004, specifies to contact Boeing for appropriate action: Before further flight, inspect or repair scribe lines and repair cracks using a method approved in accordance with the procedures specified in paragraph (p) of this AD.

(i) Where Boeing Alert Service Bulletin 737-53A1262, dated December 9, 2004, specifies a compliance time after the issuance of the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD.

(j) Certain figures are incorrectly identified in Boeing Alert Service Bulletin 737-53A1262, dated December 9, 2004. The figure cited in Part 8, step 3, should be Figure 39, not Figure 38. The figure cited in Part 9, step 4, should be Figure 38, not Figure 39.

(k) If the operator's records show that the airplane has never been stripped and repainted under the dorsal fin fairing since delivery from Boeing, then this AD does not require inspections of the butt joint, lap joint, and repair, as specified in paragraph (f) of this AD, in the areas under the dorsal fin fairing.

(l) Figure 37 of Boeing Alert Service Bulletin 737-53A1262, dated December 9, 2004, defines “Restricted Zones” at door cutouts as the only affected structure. This AD considers this area to also include Zone 1B.

(m) In Figure 1, sheets 2 and 3, of Boeing Service Bulletin 737-53A1262, dated December 9, 2004, the first condition for the initial compliance threshold for Areas B, C, and E is for areas where the cutout modification shown in Boeing Service Bulletin 737-53A1177 was accomplished. This AD considers this condition to also include Zone 1B.

(n) In Figure 1, sheets 2 and 3, of Boeing Alert Service Bulletin 737-53A1262, dated December 9, 2004, the second condition for the initial compliance threshold for Areas B, C, and E is for areas where the cutout modification shown in Boeing Service Bulletin 737-53A1177 was not accomplished. This AD considers this condition to apply only to Zone 1A.

Reporting Requirement

(o) At the applicable time specified in paragraph (o)(1) or (o)(2) of this AD, submit a report of positive findings of cracks found during the inspection required by paragraph (f) of this AD to the Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Alternatively, operators may submit reports to their Boeing field service representatives. The report shall contain, as a minimum, the following information: airplane serial number, flight cycles at time of discovery, location(s) and extent of positive crack findings. Under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.), the Office of Management and Budget (OMB) has approved the information collection requirements contained in this AD and has assigned OMB Control Number 2120-0056.

(1) If the inspection was done before the effective date of this AD: Send the report within 30 days after the effective date of this AD.

(2) If the inspection was done after the effective date of this AD: Send the report within 30 days after the inspection is done.

Alternative Methods of Compliance (AMOCs)

(p)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19.

(2) Before using any AMOC approved in accordance with 14 CFR 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office.

(3) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD, if it is approved by an Authorized Representative (AR) for the Boeing Commercial Airplanes Delegation Option Authorization Organization who has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the approval must specifically refer to this AD.

(4) A repair plan approved by a Boeing Company AR or Designated Engineering Representative before the effective date of this AD is acceptable for compliance with the requirements of paragraphs (f)(2) and (h) of this AD, provided the approval was documented via FAA Form 8110-3 or 8100-9, and identified scribe line damage in the title of the form.

Material Incorporated by Reference

(q) You must use Boeing Alert Service Bulletin 737-53A1262, dated December 9, 2004, to perform the actions that are required by this AD, unless the AD specifies otherwise. The Director of the Federal Register approved the incorporation by reference of this document in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for a copy of this service information. You may review copies at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., room PL-401, Nassif Building, Washington, DC; on the Internet at http://dms.dot.gov; or at the National Archives and Records Administration (NARA). For information on the availability of this material at the NARA, call [phone], or go to http://www.archives.gov/​federal_​register/​code_​of_​federal_​regulations/​ibr_​locations.html.

Issued in Renton, Washington, on March 20, 2006.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.