[Federal Register Volume 72, Number 226 (Monday, November 26, 2007)]
[Proposed Rules]
[Pages 65911-65913]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-22928]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-0224; Directorate Identifier 2007-NM-188-AD]
RIN 2120-AA64


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

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

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for certain Boeing Model 737-100, -200, -300, -400, and -500 series 
airplanes. This proposed AD would require repetitive inspections for 
fatigue cracking in the longitudinal floor beam web, upper chord, and 
lower chord located at certain body stations, and repair if necessary. 
This proposed AD results from several reports of cracks in the center 
wing box longitudinal floor beams, upper chord, and lower chord. We are 
proposing this AD to detect and correct fatigue cracking of the upper 
and lower chords and web of the longitudinal floor beams, which could 
result in rapid loss of cabin pressure.

DATES: We must receive comments on this proposed AD by January 10, 
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 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: 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: 

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-2007-0224; 
Directorate Identifier 2007-NM-188-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory,

[[Page 65912]]

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 have received several reports of fatigue cracks in the center 
wing box longitudinal floor beams on certain Boeing Model 737-100, -
200, -300, -400, and -500 series airplanes. The cracks were found in 
the longitudinal floor beam web, upper chord, and lower chord at left 
buttock line (LBL) 24.8, right buttock line (RBL) 24.8, LBL 45.5 and 
RBL 45.5, between Station (STA) 656 and STA 727B. The airplanes had 
accumulated between 17,000 and 70,000 total flight cycles. These 
fatigue cracks are attributed to cyclic pressurization loads, fuel 
loads, and passenger loads. Fatigue cracking of the upper and lower 
chords and web of the longitudinal floor beams, if not corrected, could 
result in rapid loss of cabin pressure.

Related Rulemaking

    On December 30, 1998, we issued AD 98-11-04 R1, amendment 39-10984 
(64 FR 987) applicable to Boeing Model 737-100 and -200 series 
airplanes. That AD requires revising the FAA-approved maintenance 
program to include inspections that will give no less than the required 
damage tolerance rating for each structural significant item (SSI) if 
they are not effective for the SSI, and repair of cracked structure. 
Certain actions in this proposed AD are considered alternative methods 
of compliance (AMOCs) for paragraphs (b) and (c) of AD 98-11-04 R1.

Relevant Service Information

    We have reviewed Boeing Service Bulletin 737-57-1296, dated June 
13, 2007. The service bulletin describes procedures for the following:
     Detailed inspections for any crack in the upper chord of 
the longitudinal floor beam at LBL 24.8 and RBL 24.8, between STA 656 
and STA 685.
     High frequency eddy current inspections for any crack in 
the lower chord of the longitudinal floor beam at LBL 24.8 and RBL 
24.8, between STA 660 and STA 666.
     Detailed inspections for any crack in the longitudinal 
floor beam web at LBL 24.8, RBL 24.8, LBL 45.5, and RBL 45.5, between 
STA 705 and STA 715.
     Detailed inspections for any crack in the horizontal 
flange of the upper chord of the longitudinal floor beam at LBL 24.8, 
RBL 24.8, LBL 45.5, and RBL 45.5, at STA 727B.
    The compliance times specified are as follows:
    For Groups 1 and 2 airplanes: Before the accumulation of 20,000 
total flight cycles, or within 6,000 flight cycles after the service 
bulletin date, whichever occurs later. Repeat the inspections 
thereafter at intervals not to exceed 6,000 flight cycles.
    For Group 3 airplanes: Before the accumulation of 20,000 total 
flight cycles, or within 7,000 flight cycles after the service bulletin 
date, whichever occurs later. Repeat the inspections thereafter at 
intervals not to exceed 7,000 flight cycles.
    If a crack is found, the service bulletin recommends contacting 
Boeing before further flight for repair instructions. If no crack is 
found, the procedures in the service bulletin specify repeating the 
inspections. Accomplishing the actions specified in the service 
information is intended to adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to exist or develop on other airplanes 
of this same type design. For this reason, we are proposing this AD, 
which would require accomplishing the actions specified in the service 
information described previously, except as discussed under 
``Difference Between the Proposed AD and Service Information.''

Difference Between the Proposed AD and Service Information

    The service bulletin specifies to contact the manufacturer for 
instructions on how to repair certain conditions, but this proposed AD 
would require repairing those conditions in one of the following ways:
     Using a method that we approve; or
     Using data that meet the certification basis of the 
airplane, and that have been approved by an Authorized Representative 
for the Boeing Commercial Airplanes Delegation Option Authorization 
Organization whom we have authorized to make those findings.

Costs of Compliance

    There are about 2,852 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 652 airplanes of 
U.S. registry. The proposed inspection would take approximately 13 work 
hours per airplane, at an average labor rate of $80 per work hour. 
Based on these figures, the estimated cost of the proposed inspection 
for U.S. operators is $678,080, or $1,040 per airplane, per inspection 
cycle.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, Section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701, ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

Regulatory Findings

    We have determined that this 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 that the 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.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this proposed 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, Safety.

[[Page 65913]]

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 Federal Aviation Administration (FAA) amends Sec.  39.13 by 
adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-0224; Directorate Identifier 2007-NM-
188-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by January 
10, 2008.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-100, -200, -300, -400, 
and -500 series airplanes, certificated in any category; as 
identified in Boeing Service Bulletin 737-57-1296, dated June 13, 
2007.

Unsafe Condition

    (d) This AD results from several reports of cracks in the center 
wing box longitudinal floor beams, upper chord, and lower chord. We 
are issuing this AD to detect and correct fatigue cracking of the 
upper and lower chords and web of the longitudinal floor beams, 
which could result in rapid loss of cabin pressure.

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.

Repetitive Inspections

    (f) Do the various inspections for fatigue cracks in the 
longitudinal floor beam web, upper chord, and lower chord, located 
at the applicable body stations specified in the Accomplishment 
Instructions of Boeing Service Bulletin 737-57-1296, dated June 13, 
2007, by doing all the actions specified in the Accomplishment 
Instructions of the service bulletin, except as provided by 
paragraph (g) of this AD. Do the inspections at the time specified 
in paragraph (f)(1) or (f)(2) of this AD, as applicable.
    (1) For Groups 1 and 2 airplanes as identified in the service 
bulletin: Do the inspections at the applicable initial compliance 
time listed in paragraph 1.E., ``Compliance,'' of the service 
bulletin; except, where the service bulletin specifies a compliance 
time after the date on the service bulletin, this AD requires 
compliance within the specified compliance time after the effective 
date of this AD. Repeat the inspections thereafter at the intervals 
specified in paragraph 1.E., ``Compliance,'' of the service 
bulletin.
    (2) For Group 3 airplanes as identified in the service bulletin: 
Do the inspections at the applicable initial compliance time listed 
in paragraph 1.E., ``Compliance,'' of the service bulletin; except, 
where the service bulletin specifies a compliance time after the 
date on the service bulletin, this AD requires compliance within the 
specified compliance time after the effective date of this AD. 
Repeat the inspections thereafter at the intervals specified in 
paragraph 1.E., ``Compliance,'' of the service bulletin.
    (g) If any crack is found during any inspection required by this 
AD, and Boeing Service Bulletin 737-57-1296, dated June 13, 2007, 
specifies contacting Boeing for repair instructions: Before further 
flight, repair using a method approved in accordance with the 
procedures specified in paragraph (h) of this AD.

Alternative Methods of Compliance (AMOCs)

    (h)(1) The Manager, Seattle ACO, FAA, has the authority to 
approve AMOCs for this AD, if requested in accordance with the 
procedures found in 14 CFR 39.19.
    (2) 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.

    Issued in Renton, Washington, on November 13, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E7-22928 Filed 11-23-07; 8:45 am]
BILLING CODE 4910-13-P