
[Federal Register: May 2, 2008 (Volume 73, Number 86)]
[Rules and Regulations]               
[Page 24164-24168]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr02my08-13]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-29043; Directorate Identifier 2007-NM-177-AD; 
Amendment 39-15494; AD 2008-09-13]
RIN 2120-AA64

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

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are adopting a new airworthiness directive (AD) for all 
Boeing Model 737-300, -400, and -500 series airplanes. This AD requires 
revising the FAA-approved maintenance inspection program to include 
inspections that will give no less than the required damage tolerance 
rating for each structural significant item (SSI), doing repetitive 
inspections to detect cracks of all SSIs, and repairing cracked 
structure. This AD results from a report of incidents involving fatigue 
cracking in transport category airplanes that are approaching or have 
exceeded their design service objective. We are issuing this AD to 
maintain the continued structural integrity of the entire fleet of 
Model 737-300, -400, and -500 series airplanes.

DATES: This AD is effective June 6, 2008.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of June 6, 
2008.

ADDRESSES: 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 AD, the regulatory evaluation, 
any comments received, and other information. The address for the 
Docket Office (telephone 800-647-5527) is the Document Management 
Facility, U.S. Department of Transportation, Docket Operations, M-30, 
West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., 
Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Nancy Marsh, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind, Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6440; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION: 

Discussion

    We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR 
part 39 to include an airworthiness

[[Page 24165]]

directive (AD) that would apply to all Boeing Model 737-300, -400, and 
-500 series airplanes. That NPRM was published in the Federal Register 
on August 24, 2007 (72 FR 48597). That NPRM proposed to require 
revising the FAA-approved maintenance inspection program to include 
inspections that will give no less than the required damage tolerance 
rating for each structural significant item (SSI), doing repetitive 
inspections to detect cracks of all SSIs, and repairing cracked 
structure.

Comments

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

Requests To Allow Alternative Inspections for Previously Repaired/
Altered Structure

    Boeing, Southwest Airlines, and United Airlines request that the 
NPRM be revised to include a provision for alternative inspections when 
a repair area prohibits operators from doing the inspections specified 
in paragraph (h) of the NPRM. The commenters request that the initial 
alternative inspection be done within 12 months after the repair is 
discovered during the initial inspection required by paragraph (h). Two 
of the commenters point out that there is a similar provision in 
paragraph (e) of AD 98-11-04 R1, amendment 39-10984 (64 FR 987, January 
7, 1999). The commenters state that including such a provision will 
assist operators.
    We agree. We have added a new paragraph (i) to this AD (and 
reidentified subsequent paragraphs) that provides alternative 
inspections to those in paragraph (h) of this AD.

Request To Allow Compliance With the Repair Assessment Program (RAP)

    Southwest and United request that the RAP be considered an 
alternative method of compliance (AMOC) for the supplemental structural 
inspection document (SSID) inspections of any repaired or modified SSI 
specified in paragraph (h) of the NPRM. United States that the FAA 
approved the RAP as an AMOC for those areas of the fuselage covered by 
repairs for Models 737-100, -200, and -200C series airplanes. Southwest 
states that multiple requirements for an individual repaired or 
modified area will create confusion, and that eventually the alternate 
inspection procedures will either be duplicated or only approved for 
one program.
    We partially agree. We agree with the commenters that some of the 
inspection areas subject to the requirements of this AD also may be 
included in the RAP. The owner/operator of an affected airplane or 
Boeing, on behalf of the owner/operator, will need to perform an 
evaluation of each of these areas of the airplane to determine if the 
actions performed in accordance with the RAP meet the requirements of 
the SSID inspection program. Our understanding is that Boeing is 
looking into this evaluation; however, we have not received any data 
supporting a request for an AMOC. Once the evaluation has been 
completed, the owner/operator or Boeing may submit the data to 
substantiate that those actions performed in accordance with the RAP 
would provide an acceptable level of safety, under the provisions of 
paragraph (l) of this AD. We have made no change to the AD in this 
regard.

Request To Delegate Approval of Structure Affected by Winglet 
Modifications

    Southwest requests that the NPRM be revised to allow an Authorized 
Representative (AR) for the Boeing Commercial Airplanes Delegation 
Option Authorization Organization to approve AMOCs for modified or 
altered structure such as winglets. Without such a provision, Southwest 
states that operators of airplanes on which winglets have been 
installed in accordance with a supplemental type certificate (STC) will 
need to seek AMOCs directly from the FAA. Southwest believes that such 
a provision would reduce the workload for operators and the FAA.
    We do not agree. At this time, we cannot authorize Boeing ARs to 
approve repair data or AMOCs for non-Boeing type design products such 
as STCs for which Boeing does not have access to the design data. We 
have made no change to the AD in this regard.

Request To Approve NPRM as a Method of Compliance With Aging Airplane 
Safety Final Rule (AASFR)

    Southwest and United request that the NPRM be approved as a method 
of compliance for the AASFR for the relevant SSIs.
    We partially agree. We agree with the commenters that compliance 
with this AD would be an acceptable means of compliance with the AASFR 
for the baseline structure of Model 737-300, -400, and -500 series 
airplanes. The Costs of Compliance section of the NPRM included such a 
statement, which is restated in this final rule. In addition, the 
Supplemental Inspections section of the AASFR states, ``The FAA will 
accept a SSID program for the baseline structure of an airplane 
developed by the OEM and approved by the FAA. If a SSID does not 
consider repairs, alterations, and modifications (RAMs), as required by 
this rule, the FAA would not accept it as a means to comply with this 
portion of the rule.'' Therefore, we find that no change to the final 
rule is necessary.

Request To Allow Zonal and Surveillance Inspections

    British Airways requests that zonal and surveillance inspections be 
considered acceptable for the general visual inspection specified in 
Boeing Document D6-82669, ``Supplemental Structural Inspection Document 
Models 737-300/400/500 Airplanes,'' Original Release, dated May 2007 
(hereafter ``the SSID'') (referred to in the NPRM as the appropriate 
source of service information for the proposed actions).
    We do not agree. Each operator's maintenance inspection program 
defines inspection terminology. That maintenance inspection program 
might be defined by different revisions of the Maintenance Steering 
Group (MSG) procedures or other procedures accepted by the operator's 
Certificate Management Office. Because inspection definitions have 
changed over time, each operator must confirm that the maintenance 
inspections procedures (e.g., surveillance or general visual 
inspections) it performs are equivalent to those specified in section 
5.0 of the SSID to take damage tolerance rating (DTR) credit for the 
SSID program. In addition, while zonal inspection programs include 
general visual inspections of an area, including the structure in that 
area, the zonal program might not include the same general visual 
inspection required by the SSID such as the specific structural detail, 
the frequency to do the inspection, and the requirement to do the 
inspection in the direction specified. Therefore, we have made no 
change to the AD in this regard.

Request To Extend Compliance Time of Reporting Requirement

    Southwest and United also request that the compliance time for the 
reporting requirement in Section 6.0, ``SSI Discrepancy Reporting,'' of 
the SSID be revised from 5 to 30 days. The commenters state that 5 days 
is insufficient time for reviewing documentation from various 
maintenance bases.
    We do not agree. In developing an appropriate compliance time for 
this action, we considered the urgency associated with cracks involving 
an SSI or related structure in close vicinity to the SSI as well as the 
recommendations

[[Page 24166]]

of the manufacturer. In consideration of these items, we have 
determined that a 5-day compliance time for reporting discrepant 
inspection findings will enable the manufacturer to obtain better 
insight into the nature, cause, and extent of the cracking, and 
eventually to develop a final action to address the unsafe condition. 
However, according to the provisions of paragraph (l) of this AD, we 
might approve requests to adjust the compliance time if the request 
includes data that prove that the new compliance time would provide an 
acceptable level of safety.

Request To Identify Differences Between the AD and the SSID

    British Airways requests that all differences between the AD and 
the SSID be identified. British Airways states that such differences 
were identified in other SSID ADs.
    We partially agree. We agree with the commenter to identify 
differences between the AD and the SSID and did so in the Differences 
Between the Proposed AD and Service Information section of the NPRM. 
However, we find that no change to the final rule is necessary, since 
that section of the NPRM does not reappear in the final rule.

Request To Clarify a Certain Section of the Preamble of the NPRM

    Boeing requests that the Issuance of Advisory Circular (AC) section 
in the preamble of the NPRM be clarified. Boeing states that AC No. 91-
56, ``Supplemental Structural Inspection Program for Large Transport 
Category Airplanes,'' dated May 6, 2001, applies to airplanes certified 
under the fail-safe and fatigue requirements of Civil Air Regulations 
(CAR) 4b or part 25 of the Federal Aviation Regulations (14 CFR part 
25), not damage tolerance structural requirements as stated in the 
Issuance of AC section of the NPRM.
    We agree with Boeing that the identified section could be 
clarified. However, no change has been made to the final rule since the 
identified sections of the NPRM do not reappear in the final rule.

Explanation of Change to Reported Incidents

    We have revised the AD to specify that this AD results from a 
report of incidents involving fatigue cracking only.

Explanation of Change to Costs of Compliance

    The requirements for the baseline structure of Model 737-300, -400, 
and -500 series airplanes are currently described in 14 CFR 
121.1109(c)(1) and 129.109(b)(1), not in 14 CFR 121.370(a) and 129.16 
as indicated in the third paragraph of the Cost of Compliance section 
of the NPRM. Therefore, we have revised the Costs of Compliance section 
of the AD accordingly.

Explanation of Editorial Changes

    We have revised references to the title of Boeing Document D6-82669 
from ``Supplemental Structural Inspection Document,'' to ``Supplemental 
Structural Inspection Document Models 737-300/400/500 Airplanes'' in 
this AD.

Conclusion

    We reviewed the relevant data, considered the comments received, 
and determined that air safety and the public interest require adopting 
the AD with the changes described previously. We also determined that 
these changes will not increase the economic burden on any operator or 
increase the scope of the AD.

Costs of Compliance

    There are about 1,961 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 U.S.-
            Action                Work hours    Average  labor        Cost         registered       Fleet cost
                                                rate  per hour                      airplanes
----------------------------------------------------------------------------------------------------------------
Revision of maintenance        1,200 per                   $80  $96,000 per                 599  $2,496,000.
 inspection program.            operator (26                     operator.
                                U.S.
                                operators).
Inspections..................  600 per                      80  $48,000, per                599  $28,752,000 per
                                airplane.                        airplane, per                    inspection
                                                                 inspection                       cycle.
                                                                 cycle.
----------------------------------------------------------------------------------------------------------------

    The number of inspection work hours, as indicated above, is 
presented as if the accomplishment of the actions in this AD are to be 
conducted as ``stand alone'' actions. However, in actual practice, 
these actions for the most part will be done coincidentally or in 
combination with normally scheduled airplane inspections and other 
maintenance program tasks. Therefore, the actual number of necessary 
additional inspection work hours will be minimal in many instances. 
Additionally, any costs associated with special airplane scheduling 
will be minimal.
    Further, compliance with this AD will be a means of compliance with 
the AASFR for the baseline structure of Model 737-300, -400, and -500 
series airplanes. The AASFR requires certain operators to incorporate 
damage tolerance inspections into their maintenance inspection 
programs. These requirements are described in 14 CFR 121.1109(c)(1) and 
129.109(b)(1). Accomplishment of the actions required by this AD will 
meet the requirements of these CFR sections for the baseline structure. 
The costs for accomplishing the inspection portion of this AD were 
accounted for in the regulatory evaluation of the AASFR final rule.

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

    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

[[Page 24167]]

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

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

2008-09-13 Boeing: Amendment 39-15494. Docket No. FAA-2007-29043; 
Directorate Identifier 2007-NM-177-AD.

Effective Date

    (a) This airworthiness directive (AD) is effective June 6, 2008.

Affected ADs

    (b) None.

Applicability

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

Unsafe Condition

    (d) This AD results from a report of incidents involving fatigue 
cracking in transport category airplanes that are approaching or 
have exceeded their design service objective. We are issuing this AD 
to maintain the continued structural integrity of the entire fleet 
of Model 737-300, -400, and -500 series airplanes.

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 Information

    (f) The term ``the SSID,'' as used in this AD, means Boeing 
Document D6-82669, ``Supplemental Structural Inspection Document 
Models 737-300/400/500 Airplanes,'' Original Release, dated May 
2007.

Revision of the FAA-Approved Maintenance Inspection Program

    (g) Before the accumulation of 66,000 total flight cycles, or 
within 12 months after the effective date of this AD, whichever 
occurs later, incorporate a revision into the FAA-approved 
maintenance inspection program that provides no less than the 
required damage tolerance rating (DTR) for each structural 
significant item (SSI) listed in the SSID. (The required DTR value 
for each SSI is listed in the SSID.) The revision to the maintenance 
inspection program must include and must be implemented in 
accordance with the procedures in Section 5.0, ``Damage Tolerance 
Rating (DTR) System Application,'' and Section 6.0, ``SSI 
Discrepancy Reporting'' of the SSID. 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.

Initial and Repetitive Inspections

    (h) Except as provided by paragraph (i) of this AD: Before the 
accumulation of 66,000 total flight cycles, or within 4,000 flight 
cycles measured from 12 months after the effective date of this AD, 
whichever occurs later, do the applicable initial inspections to 
detect cracks of all SSIs, in accordance with the SSID. Repeat the 
applicable inspections thereafter at the intervals specified in 
Section 3.0, ``Implementation'' of the SSID.
    (i) For any SSI that has been repaired or altered before the 
effective date of this AD such that the repair or design change 
affects your ability to accomplish the actions required by paragraph 
(h) of this AD: You must request FAA approval of an alternative 
method of compliance (AMOC) in accordance with section 39.17 of the 
Federal Aviation Regulations (14 CFR 39.17), at the initial 
compliance time specified in paragraph (h) of the AD; or do the 
actions specified in paragraphs (i)(1) and (i)(2) of this AD, at the 
times specified in those paragraphs, as an approved means of 
compliance with the requirements of paragraph (h) of this AD.
    (1) At the initial compliance time specified in paragraph (h) of 
the AD, identify each repair or design change to that SSI.
    (2) Within 12 months after the identification of a repair or 
design change required by paragraph (i)(1) of this AD, assess the 
damage tolerance characteristics of each SSI affected by each repair 
or design change to determine the effectiveness of the applicable 
SSID inspection for that SSI and if not effective, incorporate a 
revision into the FAA-approved maintenance inspection program to 
include a damage-tolerance based alternative inspection program for 
each affected SSI. Thereafter, inspect the affected structure in 
accordance with the alternative inspection program. The inspection 
method and compliance times (i.e., threshold and repeat intervals) 
of the alternative inspection program must be approved in accordance 
with the procedures specified in paragraph (l) of this AD.

Repair

    (j) If any cracked structure is found during any inspection 
required by paragraph (h) or (i) of this AD, before further flight, 
repair the cracked structure using a method approved in accordance 
with the procedures specified in paragraph (l) of this AD.

Inspection Program for Transferred Airplanes

    (k) Before any airplane that is subject to this AD and that has 
exceeded the applicable compliance times specified in paragraph (h) 
of this AD can be added to an air carrier's operations 
specifications, a program for the accomplishment of the inspections 
required by this AD must be established in accordance with paragraph 
(k)(1) or (k)(2) of this AD, as applicable.
    (1) For airplanes that have been inspected in accordance with 
this AD: The inspection of each SSI must be done by the new operator 
in accordance with the previous operator's schedule and inspection 
method, or the new operator's schedule and inspection method, at 
whichever time would result in the earlier accomplishment for that 
SSI inspection. The compliance time for accomplishment of this 
inspection must be measured from the last inspection accomplished by 
the previous operator. After each inspection has been done once, 
each subsequent inspection must be performed in accordance with the 
new operator's schedule and inspection method.
    (2) For airplanes that have not been inspected in accordance 
with this AD: The inspection of each SSI required by this AD must be 
done either before adding the airplane to the air carrier's 
operations specification, or in accordance with a schedule and an 
inspection method approved by the Manager, Seattle Aircraft 
Certification Office (ACO), FAA. After each inspection has been done 
once, each subsequent inspection must be done in accordance with the 
new operator's schedule.

Alternative Methods of Compliance (AMOCs)

    (l)(1) The Manager, Seattle ACO, has the authority to approve 
AMOCs for this AD, if requested in accordance with 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

[[Page 24168]]

be approved, the repair approval must specifically refer to this AD.

Material Incorporated by Reference

    (m) You must use Boeing Document D6-82669, ``Supplemental 
Structural Inspection Document Models 737-300/400/500 Airplanes,'' 
Original Release, dated May 2007, to do the actions required by this 
AD, unless the AD specifies otherwise.
    (1) The document contains the following errors:
    (i) Pages 8.0.3 and 8.0.4 of Section 8.0, as specified in the 
List of Effective Pages, do not exist.
    (ii) There are two sets of pages (four pages total) with the 
same page numbers in Section 11.3 (i.e., pages E.30.1 and E.30.2). 
The first set of page numbers (i.e., DTR Check Form for Item E-30 
and the following blank page) is correct. The second set of page 
numbers (i.e., DTR Check Form for Item E-31 and the following blank 
page) is incorrect. Those pages should be identified as page numbers 
31.1 and 31.2, as specified in the List of Effective Pages.
    (iii) None of the pages are dated. The issue date for those 
pages is May 2007, as specified in the Revision Highlights section.
    (2) The Director of the Federal Register approved the 
incorporation by reference of this service information under 5 
U.S.C. 552(a) and 1 CFR part 51.
    (3) For service information identified in this AD, contact 
Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 
98124-2207.
    (4) You may review copies of the service information 
incorporated by reference at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the 
National Archives and Records Administration (NARA). For information 
on the availability of this material at NARA, call 202-741-6030, or 
go to: http://www.archives.gov/federal_register/code_of_federal_
regulations/ibr_locations.html.

    Issued in Renton, Washington, on April 8, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-9316 Filed 5-1-08; 8:45 am]

BILLING CODE 4910-13-P
