AD 2006-07-12

[Federal Register Volume 71, Number 62 (Friday, March 31, 2006)]
[Rules and Regulations]
[Pages 16211-16217]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 06-3066]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2005-20918; Directorate Identifier 2004-NM-269-AD; 
Amendment 39-14539; AD 2006-07-12]
RIN 2120-AA64


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 <a href="http://dms.dot.gov">http://dms.dot.gov</a> 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 
(425) 917-6438; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Examining the Docket

    You may examine the airworthiness directive (AD) docket on the 
Internet at <a href="http://dms.dot.gov">http://dms.dot.gov</a> 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.

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

[[Page 16212]]

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

[[Page 16213]]

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

[[Page 16214]]

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,

[[Page 16215]]

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
----------------------------------------------------------------------------------------------------------------
                                                                                         Number of
                                                                Average      Cost per      U.S.-
        Zone                   Action             Work hours   labor rate    airplane    registered   Fleet cost
                                                                per hour                 airplanes
----------------------------------------------------------------------------------------------------------------
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

[[Page 16216]]

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

0
Accordingly, under the authority delegated to me by the Administrator, 
the FAA amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
1. The authority citation for part 39 continues to read as follows:

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


Sec.  39.13  [Amended]

0
2. The Federal Aviation Administration (FAA) amends Sec.  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

[[Page 16217]]

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 <a href="http://dms.dot.gov">http://dms.dot.gov</a>; or 
at the National Archives and Records Administration (NARA). For 
information on the availability of this material at the NARA, call 
(202) 741-6030, or go to <a href="http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html">http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html</a>.

    Issued in Renton, Washington, on March 20, 2006.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 06-3066 Filed 3-30-06; 8:45 am]
BILLING CODE 4910-13-P