[Federal Register Volume 73, Number 7 (Thursday, January 10, 2008)]
[Proposed Rules]
[Pages 1846-1848]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-251]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-0395; Directorate Identifier 2007-NM-157-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-300 and -400 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 737-300 and -400 series airplanes. This 
proposed AD would require testing and inspecting a certain web panel of 
the main wheel well pressure deck to determine the material type and 
thickness; and related investigative and corrective actions if 
necessary. This proposed AD results from several reports indicating 
that cracks ranging from 0.8 to 8.0 inches long were found on a certain 
web panel of the main wheel well pressure deck. We are proposing this 
AD to prevent fatigue cracking in the web panel of the main wheel well 
pressure deck, which could result in venting and consequent rapid 
decompression of the airplane.

DATES: We must receive comments on this proposed AD by February 25, 
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: 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-2007-0395; 
Directorate Identifier 2007-NM-157-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 have received several reports indicating that cracks ranging 
from 0.8 to 8.0 inches long were found on a certain web panel of the 
main wheel well pressure deck. These cracks were found on certain 
Boeing Model 737-300 and -400 series airplanes. Boeing analyzed pieces 
of the cracked web sections on three airplanes and found that in each 
case, the webs were made of the wrong material type and thickness. 
According to design, the web should be 0.050 inch thick 2024-T42 bare 
sheet. The webs were found to be 7075 Clad material, with thicknesses 
of 0.040 inches nominal. (Webs made from this material and thickness 
are more likely to crack.) The flight cycles on the airplanes when the 
cracking was found ranged from 13,332 to 22,849 total flight cycles. 
Cracking in the web panel, if not corrected, could result in venting 
and consequent rapid decompression of the airplane.

[[Page 1847]]

Relevant Service Information

    We have reviewed Boeing Special Attention Service Bulletin 737-57-
1289, dated June 13, 2007. The service bulletin describes procedures 
for testing and inspecting a certain web panel of the main wheel well 
pressure deck to determine if the material type and thickness are 
discrepant, and performing related investigative and corrective actions 
if necessary.
    The testing and inspection procedures include performing either a 
one-time chemical spot test or a one-time evaluation with a Scanning 
Electron Microscope (SEM) of the web material of the main wheel well 
pressure deck to determine the type of web material, and performing a 
one-time ultrasonic inspection to determine the material thickness. For 
airplanes on which the web thickness is discrepant (the thickness is 
less than 0.047 inches, or if the web material is 7000 series 
aluminum), the procedures for the related investigative and corrective 
actions include the following:
     For airplanes on which the web thickness is less than 
0.037 inches, replace the web panel before further flight.
     For airplanes on which the web thickness is greater than 
or equal to 0.037 inches and less than 0.047 inches, or the web 
material is 7000 series aluminum: Perform a detailed inspection for any 
crack and a general visual inspection for any corrosion before further 
flight. If no crack or corrosion is found, repeat the inspections until 
the web panel is replaced. Accomplishing the replacement eliminates the 
need for the repetitive inspections.
    If any crack or corrosion is found during any inspection, replace 
the web panel or contact Boeing for repair instructions and repair 
before further flight.
    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 31 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 1 airplane of U.S. 
registry. The proposed tests and inspections would take about 3 work 
hours per airplane, at an average labor rate of $80 per work hour. 
Based on these figures, the estimated cost of the proposed AD for this 
U.S. operator is $240.

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.

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-2007-0395; Directorate Identifier 2007-NM-
157-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by February 
25, 2008.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-300 and -400 series 
airplanes, certificated in any category; as identified in Boeing 
Special Attention Service Bulletin 737-57-1289, dated June 13, 2007.

Unsafe Condition

    (d) This AD results from several reports indicating that cracks 
ranging from 0.8 to 8.0 inches long were found on a certain web 
panel of the main wheel well pressure deck. We are issuing this AD 
to prevent fatigue cracking in the web panel of the main wheel well 
pressure deck, which could result in venting and consequent 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.

[[Page 1848]]

Testing/Inspecting/Investigative and Corrective Actions

    (f) Within 6 months after the effective date of this AD: Do a 
test of the web panel of the main wheel well pressure deck to 
determine the material type, and do an ultrasonic inspection to 
determine material thickness, by doing all the applicable actions 
specified in the Accomplishment Instructions of Boeing Special 
Attention Service Bulletin 737-57-1289, dated June 13, 2007.
    (g) For airplanes on which the web thickness or material is 
found to be discrepant during the test and inspection required by 
paragraph (f) of this AD, accomplish the applicable actions 
specified in paragraphs (g)(1) and (g)(2) of this AD at the time 
specified, in accordance with the Accomplishment Instructions of 
Boeing Special Attention Service Bulletin 737-57-1289, dated June 
13, 2007.
    (1) Do all applicable related investigative and corrective 
actions (including detailed and general visual inspections) before 
further flight, by doing all the actions specified in the 
Accomplishment Instructions of the service bulletin; except as 
provided by paragraph (h) of this AD. Repeat the inspections 
thereafter at intervals not to exceed 1,000 flight cycles until 
paragraph (g)(2) of this AD has been done.
    (2) Within 30 months or 6,000 flight cycles after accomplishing 
the actions required by paragraph (g)(1) of this AD, whichever is 
later, replace the web panel in accordance with the Accomplishment 
Instructions of the service bulletin. Doing this replacement ends 
the repetitive inspections required by paragraph (g)(1) of this AD.

Corrective Actions

    (h) If any crack or corrosion is found during any inspection 
required by paragraph (g)(1) of this AD, and Boeing Special 
Attention Service Bulletin 737-57-1289, dated June 13, 2007, 
specifies to contact Boeing for repair instructions: Before further 
flight, repair according to a method approved in accordance with the 
procedures specified in paragraph (i) of this AD.

Alternative Methods of Compliance (AMOCs)

    (i)(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 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 December 21, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-251 Filed 1-9-08; 8:45 am]
BILLING CODE 4910-13-P