Document ID: FAA-2007-28283-0009
Agency: faa
Document Type: Rule
Title: Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800 and -900 Series Airplanes
Posted Date: 2008-08-19T04:00Z

[Federal Register: August 19, 2008 (Volume 73, Number 161)]
[Proposed Rules]               
[Page 48307-48309]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr19au08-26]                         

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Proposed Rules
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains notices to the public of 
the proposed issuance of rules and regulations. The purpose of these 
notices is to give interested persons an opportunity to participate in 
the rule making prior to the adoption of the final rules.

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[[Page 48307]]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-28283; Directorate Identifier 2006-NM-254-AD]
RIN 2120-AA64

 
Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800 
and -900 Series Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

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

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

SUMMARY: We are revising an earlier proposed airworthiness directive 
(AD) for certain Boeing Model 737-600, -700, -700C, -800 and -900 
series airplanes. The original NPRM would have required a one-time 
general visual inspection of frames between body station (BS) 360 and 
BS 907 to determine if certain support brackets of the air conditioning 
(A/C) outlet extrusions are installed; medium- and high-frequency eddy 
current inspections for cracking of the frames around the attachment 
holes of the subject brackets; and repair if necessary. The original 
NPRM would also have required installing new, improved fittings for all 
support brackets of the A/C outlet extrusions between BS 360 and BS 
907. The original NPRM resulted from numerous reports of multiple 
cracks in the frames around the attachment holes of certain support 
brackets of the A/C outlet extrusions. This action revises the original 
NPRM by adding an airplane to the applicability and reducing the 
compliance time for certain airplanes. We are proposing this 
supplemental NPRM to prevent frame cracking, which, if not corrected, 
could lead to a severed frame that, combined with cracking of the skin 
lap splice above stringer 10, could result in rapid decompression of 
the airplane.

DATES: We must receive comments on this supplemental NPRM by September 
15, 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, 
for the service information identified in this proposed AD.

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 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-
28283; Directorate Identifier 2006-NM-254-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 737-600, -700, -700C, -
800 and -900 series airplanes. That original NPRM was published in the 
Federal Register on May 25, 2007 (72 FR 29280). That original NPRM 
proposed to require a one-time general visual inspection of frames 
between body station (BS) 360 and BS 907 to determine if certain 
support brackets of the air conditioning (A/C) outlet extrusions are 
installed; medium- and high-frequency eddy current inspections for 
cracking of the frames around the attachment holes of the subject 
brackets; and repair if necessary. That original NPRM also proposed to 
require installing new, improved fittings for all support brackets of 
the A/C outlet extrusions between BS 360 and BS 907.

Actions Since Original NPRM Was Issued

    Since we issued the original NPRM, Boeing has issued Special 
Attention Service Bulletin 737-25-1544, Revision 1, dated January 16, 
2008. The revised service bulletin adds an airplane to the effectivity 
and deletes all references to an unreleased service bulletin. The 
service bulletin also reduces inspection thresholds for airplanes on 
which Boeing Business Jet (BBJ) lower cabin altitude modification has 
been incorporated in accordance with Supplemental Type Certificate 
(STC) ST01697SE.

Comments

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

[[Page 48308]]

Support for the Original NPRM

    Boeing concurs with the content of the original NPRM.

Request To Clarify Inspection Requirements

    AirTran Airways requests that we clarify the inspection 
requirements of the NPRM. AirTran suggests that we revise paragraphs 
(g) and (h) of the NPRM to specify that, in accordance with Boeing 
Special Attention Service Bulletin 737-25-1544, dated October 4, 2006, 
some frames between body station (BS) 360 and BS 907 are excluded from 
the inspection requirements of the service bulletin. AirTran asserts 
that this will help to ensure that the inspection requirements of the 
original NPRM do not deviate from the procedures described in the 
service bulletin.
    We partially agree with this request. Some frames are machined or 
fabricated from a thicker material or have a three-rivet attachment 
fitting, rather than the two-rivet attachment fitting. Further, the 
notes of Step 3.B.1 of ``Part 1--Access'' of the Accomplishment 
Instructions of the service bulletin specify that these frames are not 
subject to the inspections. Therefore, we have revised paragraph (g) of 
the supplemental NPRM to clarify that certain frames are not subject to 
the inspection requirements of the proposed AD.
    However, paragraph (h) of the supplemental NPRM refers to the 
modification, which affects all frames between BS 360 and BS 907; 
therefore, it is not appropriate to exempt the frames specified by the 
commenter from the requirements of paragraph (h) of the supplemental 
NPRM. As specified in paragraph (h) of the supplemental NPRM all frames 
are affected. We have not changed the supplemental NPRM in this regard.

Compliance Time for Certain Airplanes

    We have determined from Boeing Special Attention Service Bulletin 
737-25-1544, Revision 1, dated January 16, 2008, that the compliance 
time for airplanes on which BBJ lower cabin altitude modification has 
been incorporated in accordance with STC ST01697SE must be reduced by 
one-half for the flight cycle compliance time. Therefore, we have added 
new paragraph (i) to the supplemental NPRM to define the compliance 
time for these airplanes as: Before the accumulation of 18,000 total 
flight cycles, or within 72 months after the effective date of this AD, 
whichever occurs later.

Credit for Use of Original Issue of Service Bulletin

    We have revised this supplemental NPRM to refer to Boeing Special 
Attention Service Bulletin 737-25-1544, Revision 1, dated January 16, 
2008, as the appropriate source of service information for doing the 
requirements of the proposed AD. Therefore, we have added new paragraph 
(j) to the supplemental NPRM to give credit for actions done prior to 
the effective date of the AD according to Boeing Special Attention 
Service Bulletin 737-25-1544, dated October 4, 2006. We have also re-
identified paragraph (i) of the original NPRM as paragraph (k) of the 
supplemental NPRM.

Clarification of Paragraph (g)(1) of the NPRM

    Paragraph (g)(1) of the NPRM specifies that for any support bracket 
not attached with a two-rivet attachment fitting, no further action is 
required by paragraph (g) of the NPRM.
    We have revised paragraph (g)(1) of the supplemental NPRM to 
specify that for any support bracket attached with three or more 
rivets, no further action is required by paragraph (g) of the 
supplemental NPRM.

Clarification of Compliance Time in Paragraph (g)(2) of the NPRM

    Paragraph (g)(2) of the NPRM does not specify a compliance time for 
doing the inspections specified in that paragraph. We intended that the 
inspections be done within the same compliance time specified in 
paragraph (g) of the NPRM. We have added the compliance time specified 
in paragraph (g) of the supplemental NPRM to paragraph (g)(2) of the 
supplemental NPRM.

Clarification of Unsafe Condition Statement

    We have replaced the phrase ``to detect and correct'' in the unsafe 
condition statement in the Summary and in paragraph (d) of the 
supplemental NPRM with the phrase ``to prevent'' to clarify that the 
actions in this supplemental NPRM are intended to prevent the 
identified unsafe condition.

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

    There are about 1,679 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 626 airplanes of 
U.S. registry. The following table provides the estimated costs for 
U.S. operators to comply with this proposed AD, at an average labor 
rate of $80 per work hour. Operators should note that special cold 
working tools and sleeves will be needed if any repair is required, 
which may increase costs.

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
             Action                   Work hours             Parts         Cost per airplane      Fleet cost
----------------------------------------------------------------------------------------------------------------
General visual inspection.......   1................  No parts required.  $80...............  $50,080.
MFEC and HFEC inspections.......   Between 170 and    No parts required.  Between $13,600     Up to $10,817,280.
                                   216.                                    and $17,280.
Replace support fittings........  Between 258 and     Between $56,095     Between $76,735     Up to $68,245,894.
                                   346.                and $81,339.        and $109,019.
----------------------------------------------------------------------------------------------------------------

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:

[[Page 48309]]

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.

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-2007-28283; Directorate Identifier 2006-NM-
254-AD.

Comments Due Date

    (a) We must receive comments by September 15, 2008.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-600, -700, -700C, -800 
and -900 series airplanes; certificated in any category; as 
identified in Boeing Special Attention Service Bulletin 737-25-1544, 
Revision 1, dated January 16, 2008.

Unsafe Condition

    (d) This AD results from numerous reports of multiple cracks in 
the frame around the attachment holes of the support bracket of the 
air conditioning (A/C) outlet extrusion. We are issuing this AD to 
prevent frame cracking, which, if not corrected, could lead to a 
severed frame that, combined with cracking of the skin lap splice 
above stringer 10, could result in rapid 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 Reference

    (f) The term ``service bulletin,'' as used in this AD, means the 
Accomplishment Instructions of Boeing Special Attention Service 
Bulletin 737-25-1544, Revision 1, dated January 16, 2008.

Inspections

    (g) Before the accumulation of 36,000 total flight cycles, or 
within 72 months after the effective date of this AD, whichever 
occurs later, except as required by paragraph (i) of this AD: Do a 
general visual inspection to determine if the support brackets of 
the A/C outlet extrusions between body station (BS) 360 and BS 907 
have two-rivet attachment fittings in accordance with Part 2 of the 
service bulletin, except at the locations identified in the notes of 
Step 3.B.1 of Part 1 of the service bulletin.
    (1) For any support bracket attached with three or more rivets: 
No further action is required by paragraph (g) of this AD.
    (2) For any subject support bracket having a two-rivet 
attachment fitting: Before the accumulation of 36,000 total flight 
cycles, or within 72 months after the effective date of this AD, 
whichever occurs later, except as required by paragraph (i) of this 
AD, do medium- and high-frequency eddy current inspections for 
cracking of the frame around the attachment holes of the support 
bracket, in accordance with Part 2 of the service bulletin. If any 
cracking is discovered, before further flight, repair the cracking 
in accordance with Part 3 of the service bulletin.

Modification

    (h) Except as required by paragraph (i) of this AD: Before the 
accumulation of 36,000 total flight cycles, or within 72 months 
after the effective date of this AD, whichever occurs later, replace 
the support fittings of all A/C outlet extrusions between BS 360 and 
BS 907 with new, improved support fittings, in accordance with Part 
4 of the service bulletin.

Compliance Time for Certain Airplanes

    (i) For airplanes on which Boeing Business Jet (BBJ) lower cabin 
altitude modification is incorporated in accordance with 
Supplemental Type Certificate ST01697SE: Before the accumulation of 
18,000 total flight cycles, or within 72 months after the effective 
date of this AD, whichever occurs later, do the actions specified in 
paragraphs (g) and (h) of this AD.

Actions Accomplished According to Previous Issue of Service Bulletin

    (j) Actions accomplished before the effective date of this AD 
according to Boeing Special Attention Service Bulletin 737-25-1544, 
dated October 4, 2006, are considered acceptable for compliance with 
the corresponding actions specified in this AD.

Alternative Methods of Compliance (AMOCs)

    (k)(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 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 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 7, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-19149 Filed 8-18-08; 8:45 am]

BILLING CODE 4910-13-P