
[Federal Register: August 29, 2008 (Volume 73, Number 169)]
[Proposed Rules]               
[Page 50899-50902]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr29au08-17]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-29255; Directorate Identifier 2007-NM-085-AD]
RIN 2120-AA64

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

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Supplemental notice of proposed rulemaking (NPRM); reopening of 
comment period.

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SUMMARY: We are revising an earlier proposed airworthiness directive 
(AD) for certain Boeing Model 737-100, -200, -200C, -300, -400, and -
500 series airplanes. The original NPRM would have required doing 
repetitive internal eddy current and detailed inspections to detect 
cracked stringer tie clips; measuring the fastener spacing and the edge 
margin if applicable, and doing applicable corrective and related 
investigative actions. As a temporary alternative to doing the actions 
described previously, the original NPRM would have required repetitive 
inspections of the skin and lap joints for cracks and evidence of 
overload resulting from cracked stringer tie clips, and applicable 
corrective actions if necessary. The original NPRM resulted from a 
report of several cracked stringer tie clips. This action revises the 
original NPRM by including repetitive external eddy current sliding 
probe inspections of the lap joints for cracks and evidence of overload 
resulting from cracked stringer tie clips. We are proposing this 
supplemental NPRM to detect and correct multiple adjacent cracked 
stringer tie clips and damaged skin and frames, which could lead to the 
skin and frame structure developing cracks and consequent decompression 
of the airplane.

DATES: We must receive comments on this supplemental NPRM by September 
23, 2008.

ADDRESSES: You may send comments by any of the following methods:
     Federal eRulemaking Portal: Go to http://
www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 202-493-2251.
     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: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.
    For service information identified in this AD, contact Boeing 
Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

Examining the AD Docket

    You may examine the AD docket on the Internet at http://
www.regulations.gov; 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

[[Page 50900]]

regulatory evaluation, any comments received, and other information. 
The street address for the Docket Office (telephone 800-647-5527) is in 
the ADDRESSES section. Comments will be available in the AD docket 
shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Wayne Lockett, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6447; fax (425) 917-6590.

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-2007-
29255; Directorate Identifier 2007-NM-085-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

    We issued a notice of proposed rulemaking (NPRM) (the ``original 
NPRM'') to amend 14 CFR part 39 to include an airworthiness directive 
(AD) that would apply to certain Boeing Model 737-100, -200, -200C, -
300, -400, and -500 series airplanes. That original NPRM was published 
in the Federal Register on September 20, 2007 (72 FR 53706). That 
original NPRM proposed to require doing repetitive internal eddy 
current and detailed inspections to detect cracked stringer tie clips; 
measuring the fastener spacing and the edge margin if applicable; and 
doing applicable corrective and related investigative actions. As a 
temporary alternative to doing the actions described previously, that 
original NPRM proposed to require repetitive external general visual 
inspections of the skin and lap joints for cracks and evidence of 
overload resulting from cracked stringer tie clips, and applicable 
corrective actions if necessary.

Comments

    We gave the public the opportunity to participate in developing 
this AD. We considered the comments received from the four commenters.

Requests To Revise Grace Period for Accomplishing Inspections A and B

    US Airways requests that, for certain airplane configurations, the 
grace period for accomplishing the initial inspections specified in 
paragraph (g) of the original NPRM (Inspection A) be extended from 2 
years to 4 years. KLM requests that the grace period of Inspection A be 
extended to 8 years, and that the intervals for accomplishing the 
temporary alternative inspection specified in paragraph (h) of the 
original NPRM (Inspection B) be reduced.
    US Airways states that it has been successfully inspecting the same 
area for corrosion and other damage per the Corrosion Prevention and 
Control Program (CPCP), as required by AD 90-25-01, amendment 39-6789 
(55 FR 49263, November 27, 1990). US Airways states that the compliance 
time should be extended for operators accomplishing the CPCP. US 
Airways and KLM state extending the compliance time for accomplishing 
Inspection A would allow operators to better schedule that inspection, 
and thus would limit the economic impact. US Airways also states that 
temporary alternative inspections specified in paragraph (h) of the 
original NPRM (Inspection B) are not as desirable as Inspection A. US 
Airways believes Inspection B would increase the risk of damage to 
airplanes due to operators' need to use various lift equipment to reach 
the inspection area.
    We do not agree with the commenters' request to extend the 
compliance time specified in paragraph (g) of the supplemental NPRM 
(Inspection A) or to reduce the compliance time specified in paragraph 
(h) of the supplemental NPRM (Inspection B). We have determined that 
the visual inspections required by AD 90-25-01 do not detect multiple 
adjacent cracks at stringer tie clips, which is the identified unsafe 
condition of this supplemental NPRM. The CPCP inspections cited do not 
focus on the areas of affected stringer tie clips. In developing an 
appropriate compliance time for this supplemental NPRM, we considered 
not only the degree of urgency associated with addressing the 
identified unsafe condition, but the practical aspect of incorporating 
the proposed inspections into affected operators' maintenance schedules 
in a timely manner. Further, deferral of Inspection A for multiple clip 
failures does not provide an acceptable level of safety. In light of 
these items, we have determined that the applicable compliance times 
identified in paragraphs (g) and (h) of the supplemental NPRM are 
appropriate. However, paragraph (o) of the supplemental NPRM provides 
affected operators the opportunity to apply for an adjustment of the 
compliance time if the operator also presents data that justify the 
adjustment.

Requests To Clarify Inspection B

    The Air Transport Association (ATA), on behalf of one of its 
members, United Airlines, and Boeing request that paragraph (h) of the 
NPRM be clarified as to which affected airplanes the temporary 
alternative inspections specified in paragraph (h) of the original NPRM 
(Inspection B) may be done on. The commenters state that a note in the 
Accomplishment Instructions of Boeing Special Attention Service 
Bulletin 737-53-1268, dated August 25, 2006 (referred to as the 
appropriate source of service information for doing the proposed 
actions), limits Inspection B to airplanes having stringer tie clips 
replaced in accordance with Boeing Service Bulletin 737-53-1085, 
Revision 1, dated May 10, 1990. The commenters note that the AD does 
not have such a limitation.
    We agree with the commenters that clarification is necessary. 
Paragraph (h) of the supplemental NPRM specifies to do all 
``applicable'' actions in accordance with the Accomplishment 
Instructions of Boeing Special Attention Service Bulletin 737-53-1268. 
As noted by the commenters, a note in the Accomplishment Instructions 
states, ``The Option B Inspection is not allowed on airplanes that have 
not accomplished terminating action of replacing the stringer tie clips 
as given in Service Bulletin 737-53-1085.'' However, the note does not 
explain that Boeing Service Bulletin 737-53-1085 affects only airplanes 
having line numbers 1 through 1000 inclusive. Without such an 
explanation, operators could misinterpret that paragraph (h) of the 
supplemental NPRM may be done on airplanes having line numbers 1001 and 
subsequent, which are also subject to the proposed actions of this 
supplemental NPRM. Therefore, we have added Note 3 to this supplemental 
NPRM to clarify this point.
    Boeing also requests that the first sentence of paragraph (h) of 
the NPRM be revised to include eddy current inspections of the lap 
joints. Boeing states that, for Inspection B, Boeing Special Attention 
Service Bulletin 737-53-1268 specifies eddy current inspections of the 
lap joints.

[[Page 50901]]

    We agree. It was our intent that the proposed inspections align 
with those specified in Boeing Special Attention Service Bulletin 737-
53-1268. Therefore, we have revised paragraph (h) of the supplemental 
NPRM accordingly.

Request To Clarify Unsafe Condition

    Boeing requests that, for clarification purposes, the unsafe 
condition throughout the original NPRM be revised from ``* * * multiple 
cracked stringer tie clips * * *.'' to ``* * * multiple adjacent 
cracked stringer tie clips * * *.'' Boeing states that the safety 
concern is when there are multiple ``adjacent'' stringer tie clips 
(three or more) that are cracked.
    We agree and have revised the supplemental NPRM accordingly.

Request To Clarify Relevant Service Information Section

    Boeing requests several editorial changes to the Relevant Service 
Information section of the original NPRM for clarification purposes.
    We partially agree. We acknowledge that Boeing's suggested changes 
to that section would further clarify the information specified in the 
service bulletin. However, the Relevant Service Information section of 
the original NRPM does not reappear in the supplemental NPRM. 
Therefore, we have made no change to this supplemental NPRM in this 
regard.

Request To Revise Work-Hour Estimate

    Boeing requests that the work hours for Inspection A in the Costs 
of Compliance section of the original NPRM be revised from between 40 
and 103 to between 253 and 307. Boeing states that Inspection A 
requires internal access, which requires many more hours than that 
shown in the Estimated Costs table.
    We do not agree. The Costs of Compliance section describes only the 
direct costs of the specific actions proposed by this supplemental 
NPRM. The estimated work hours represent the time necessary to perform 
only the actions actually proposed by this supplemental NPRM. We 
recognize that, in doing the actions required by an AD, operators might 
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 required to gain access and close up, 
time necessary for planning, or time necessitated by other 
administrative actions. Those incidental costs, which might vary 
significantly among operators, are almost impossible to calculate. 
Therefore, we have made no change to the supplemental NPRM in this 
regard.

Clarification of Unsafe Condition

    The Summary section and paragraph (d) of the NPRM state, ``We are 
proposing this supplemental NPRM to prevent multiple cracked stringer 
tie clips and damaged skin and frames * * *'' For clarification 
purposes, we have changed the phrase ``to prevent'' to ``to detect and 
correct'' in that section and paragraph of this supplemental NPRM.

FAA's Determination and Proposed Requirements of the Supplemental NPRM

    We are proposing this supplemental NPRM because we evaluated all 
pertinent information and determined an unsafe condition exists and is 
likely to exist or develop on other products of the same type design. 
Certain changes described above expand the scope of the original NPRM. 
As a result, we have determined that it is necessary to reopen the 
comment period to provide additional opportunity for the public to 
comment on this supplemental NPRM.

Costs of Compliance

    We estimate that this proposed AD would affect 787 airplanes of 
U.S. registry. The following table provides the estimated costs for 
U.S. operators to comply with this proposed AD.

                                                 Estimated Costs
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                                                                                    Number of
                                                     Average    Cost per airplane     U.S.-
            Action                Work hours \1\    labor rate         \1\          registered   Fleet cost \1\
                                                     per hour                       airplanes
----------------------------------------------------------------------------------------------------------------
Inspection A..................  Between 40 and             $80  Between $3,200             787  Between
                                 103.                            and $8,240, per                 $2,518,400 and
                                                                 inspection cycle.               $6,484,880, per
                                                                                                 inspection
                                                                                                 cycle.
Inspection B (temporary         Between 2 and 109           80  Between $160 and           787  Between $125,920
 alternative to Inspection A).                                   $8,720.                         and $6,862,640,
                                                                                                 per inspection
                                                                                                 cycle.
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\1\ Depending on the airplane configuration.

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 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 this 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), 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.
    You can find our regulatory evaluation and the estimated costs of 
compliance in the AD Docket.

[[Page 50902]]

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, 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.


Sec.  39.13  [Amended]

    2. The FAA amends Sec.  39.13 by adding the following new AD:

Boeing: Docket No. FAA-2007-29255; Directorate Identifier 2007-NM-
085-AD.

Comments Due Date

    (a) We must receive comments by September 23, 2008.

Affected ADs

    (b) AD 93-08-04, amendment 39-8551.

Applicability

    (c) This AD applies to Boeing Model 737-100, -200, -200C, -300, 
-400, and -500 series airplanes, certificated in any category; as 
identified in Boeing Special Attention Service Bulletin 737-53-1268, 
dated August 25, 2006.

Unsafe Condition

    (d) This AD results from a report of several cracked stringer 
tie clips. We are issuing this AD to detect and correct multiple 
adjacent cracked stringer tie clips and damaged skin and frames, 
which could lead to the skin and frame structure developing cracks 
and consequent decompression of the airplane.

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.

Service Bulletin References

    (f) The term ``the service bulletin,'' as used in this AD, means 
the Accomplishment Instructions of Boeing Special Attention Service 
Bulletin 737-53-1268, dated August 25, 2006.

Inspection A: Required Internal Inspections, Applicable Corrective and 
Related Investigative Actions, and Measurement

    (g) Do repetitive internal eddy current and detailed inspections 
to detect cracked stringer tie clips; measure the fastener spacing 
and the edge margin if applicable; and do applicable corrective and 
related investigative actions. Do all applicable actions at the 
applicable compliance times and repeat intervals identified in 
Tables 2 through 8 inclusive of paragraph 1.E., ``Compliance,'' of 
the service bulletin; except as provided by paragraphs (i) through 
(l) of this AD. Do all applicable actions in accordance with the 
Accomplishment Instructions of the service bulletin, except as 
provided by paragraph (m) of this AD.

    Note 1: The service bulletin refers to Boeing Service Bulletin 
737-53A1177, Revision 6, dated May 31, 2001, as an additional source 
of service information for doing an internal eddy current inspection 
of the lap joint for certain airplane configurations.

Inspection B: Temporary Alternative External Inspections and Corrective 
Actions

    (h) As a temporary alternative to doing the actions required by 
paragraph (g) of this AD, do repetitive external general visual 
inspections of the skin and lap joints and repetitive external eddy 
current sliding probe inspections of the lap joints for cracks and 
evidence of overload resulting from cracked stringer tie clips, and 
applicable corrective actions if necessary. Do all applicable 
actions at the applicable compliance times and repeat intervals 
identified in Tables 9 through 12 inclusive of paragraph 1.E., 
``Compliance,'' of the service bulletin, but not to exceed the 
flight cycles in the ``Inspection Period Allowed'' column of the 
tables; except as provided by paragraphs (i) and (l) of this AD. Do 
all applicable actions in accordance with the Accomplishment 
Instructions of the service bulletin, except as provided by 
paragraph (m) of this AD.

    Note 2: The eddy current inspection along the stringer tie clip 
radius to detect damage and replacement, as applicable, specified in 
paragraph 3.B.5. of the Accomplishment Instructions of the service 
bulletin are not required by this AD. The actions are optional and 
can be done in addition to and at the same time as the actions 
required by paragraph (g) of this AD.


    Note 3: Inspection B may be used on affected airplanes having 
line numbers 1 through 1000 inclusive on which the terminating 
action (i.e., replacement of stringer tie clips) specified in Boeing 
Service Bulletin 737-53-1085, Revision 1, dated May 10, 1990, has 
been done; and on affected airplanes having line numbers 1001 and 
subsequent. The service bulletin contains a similar note.

Exceptions to Service Information

    (i) Where the service bulletin specifies a compliance time after 
the date of the service bulletin, this AD requires compliance within 
the specified compliance time after the effective date of this AD.
    (j) For Model 737-100, -200, and -200C series airplanes, on 
which Boeing Service Bulletin 737-53-1085, Revision 1, dated May 10, 
1990, has not been done in accordance with AD 93-08-04: As of the 
effective date of this AD, do the applicable inspections from 
station (STA) 559 to STA 887 in accordance with paragraph (g) of 
this AD, at the applicable compliance times specified in paragraph 
(b) of AD 93-08-04.
    (k) In the first row of Tables 5 and 6 of paragraph 1.E., 
``Compliance,'' of the service bulletin, where the service bulletin 
specifies a compliance time of before 25,000 total airplane flight 
cycles, this AD requires a compliance time of before the 
accumulation of 25,000 total flight cycles, or within 2 years after 
the effective date of this AD, whichever occurs later.
    (l) Where the service bulletin specifies no starting point 
(e.g., ``after the date on the service bulletin'') for a grace 
period, this AD requires compliance within the specified grace 
period after the effective date of this AD.
    (m) Where the service bulletin specifies to contact Boeing for 
appropriate action: Before further flight, repair the discrepancy 
using a method approved in accordance with the procedures specified 
in paragraph (o) of this AD.

Certain Actions End Certain Requirements of AD 93-08-04

    (n) Accomplishment of the internal eddy current and detailed 
inspections for STA 559 to STA 887 in accordance with paragraph (g) 
of this AD constitutes compliance with the inspections required by 
paragraph (a) of AD 93-08-04, as it pertains to Boeing Service 
Bulletin 737-53-1085, Revision 1, dated May 10, 1990. Accomplishment 
of the internal eddy current and detailed inspections does not 
terminate the remaining requirements of AD 93-08-04, as it applies 
to other service bulletins. Operators are required to continue to 
inspect and/or modify per the other service bulletins listed in that 
AD.

Alternative Methods of Compliance (AMOCs)

    (o)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, ATTN: Wayne Lockett, Aerospace Engineer, Airframe Branch, ANM-
120S, FAA, Seattle ACO, 1601 Lind Avenue, SW., Renton, Washington 
98057-3356; telephone (425) 917-6447; fax (425) 917-6590; has the 
authority to approve AMOCs for this AD, if requested using the 
procedures found in 14 CFR 39.19.
    (2) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Before using any approved AMOC on any airplane to which the AMOC 
applies, notify your appropriate principal inspector (PI) in the FAA 
Flight Standards District Office (FSDO), or lacking a PI, your local 
FSDO.
    (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 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 repair must meet the certification basis 
of the airplane, and the approval must specifically refer to this 
AD.

    Issued in Renton, Washington, on August 20, 2008.
Kevin Hull,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-20102 Filed 8-28-08; 8:45 am]

BILLING CODE 4910-13-P
