[Federal Register Volume 73, Number 131 (Tuesday, July 8, 2008)]
[Rules and Regulations]
[Pages 38885-38887]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-14475]


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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; 
Amendment 39-15588; AD 2008-13-25]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-300 and -400 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 certain 
Boeing Model 737-300 and -400 series airplanes. This AD requires 
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 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 decompression of the airplane.

DATES: This AD is effective August 12, 2008.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of August 12, 
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: 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: 

Discussion

    We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR 
part 39 to include an airworthiness directive (AD) that would apply to 
certain Boeing Model 737-300 and -400 series airplanes. That NPRM was 
published in the Federal Register on January 10, 2008 (73 FR 1846). 
That NPRM proposed to 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.

Comments

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

Request To Change the Description of the Unsafe Condition

    Boeing asks that the unsafe condition (end level effect) specified 
in the applicable sections of the NPRM be changed from ``rapid 
decompression'' to ``controlled decompression.'' Boeing states that the 
most probable result of the cracking would be pressure loss or 
controlled depressurization. Boeing has received reports of cracks 
ranging from 4.5 to 8 inches in the web panel of the main wheel well 
pressure deck; the reports included the following data:
     Cabin crews reported a loud hissing noise coming from the 
area below seats 14A, B, and C. No depressurization was reported.
     The crew reported a loud hissing noise from the cabin 
lining on the left-hand side at row 15. The cabin windows along the 
left-hand side progressively frosted up until, after about 2 hours, all 
the windows were frosted up between rows 11 through 17.
     It was reported that it was not possible to pressurize 
another airplane.
    We partially agree with Boeing. We agree to change the end level 
effect of the unsafe condition by removing the word ``rapid,'' since 
Boeing has provided data verifying that the decompression does not 
happen quickly. However, we do not agree that

[[Page 38886]]

the decompression is ``controlled'' because of the safety implications 
and consequences associated with cracking on a web panel of the main 
wheel well pressure deck. We have changed the applicable sections in 
this AD accordingly.

Request To Clarify Certain Compliance Times

    Boeing asks that we clarify the different compliance times for 
replacing discrepant web panels, depending on the thickness, as 
specified in Table 1 of Part 1.E., Compliance, of Boeing Special 
Attention Service Bulletin 737-57-1289, dated June 13, 2007. (The 
service bulletin was referenced in the NPRM as the appropriate source 
of service information for accomplishing the specified actions.) Boeing 
states that, as written, paragraphs (g)(1) and (g)(2) of the NPRM would 
allow 30 months or 6,000 flight cycles, whichever is later, to replace 
discrepant web panels. Boeing notes that this is acceptable for 
discrepant web panels with a material thickness that is found to be 
greater than or equal to 0.037 inch, and less than 0.047 inch; however, 
for web panels with a material thickness of less than 0.037 inch the 
specified compliance time is before further flight. Boeing adds that 
web panels with a material thickness of less than 0.037 inch do not 
meet the ultimate regulatory load requirements. Boeing also asks that 
the related investigative and corrective actions be clarified.
    We agree with Boeing that some clarification is necessary. 
Paragraph (g)(1) of the AD requires accomplishing all applicable 
related investigative and corrective actions before further flight 
(which includes replacing any discrepant web panels) by doing all the 
actions specified in the Accomplishment Instructions of the service 
bulletin. The Accomplishment Instructions do not clearly identify web 
panels with a material thickness of less than 0.037 inch; however, the 
web panels are clearly identified in paragraph 1.E. of the service 
bulletin. Paragraph 1.E. specifies replacing web panels with a material 
thickness of less than 0.037 inch, as specified in paragraph 3.B.7. of 
the Accomplishment Instructions of the service bulletin. Therefore, we 
have clarified paragraph (g)(1) of this AD to add that the corrective 
actions include replacing any web panel with a material thickness of 
less than 0.037 inch before further flight. We have also changed 
paragraph (g)(2) of this AD to clarify that the compliance time in that 
paragraph is separate from the compliance time specified in paragraph 
(g)(1). The related investigative and corrective actions are defined in 
the service information section of the NPRM; therefore, no change is 
necessary in this regard.

Request To Clarify That Additional Action Is Necessary

    Boeing also asks that we change paragraph (e) of the NPRM to 
clarify that additional action is necessary for operators that 
inspected web panels using instructions that were contained in Boeing 
Communication messages that were sent out on January 17, 2006, prior to 
the release of the referenced service bulletin. Boeing states that the 
messages were sent to airlines that were operating airplanes that could 
have a discrepant web panel. Boeing adds that following release of 
those messages, as part of the information being developed for release 
in the referenced service bulletin, it was determined that additional 
details were necessary to accurately define the instructions to inspect 
for discrepant web panels. Boeing notes that the additional details, 
which affect both the chemical spot test and the ultrasonic thickness 
inspections, have been included in the service bulletin referenced in 
the NPRM as the source of service information for doing the specified 
actions; therefore, inspections accomplished without these additional 
steps could result in incorrect identification of discrepant web 
panels. Boeing also suggests that this language be added to paragraph 
(e) of the AD.
    We acknowledge Boeing's concerns; however, paragraph 1.E, 
``Compliance,'' of the referenced service bulletin specifies that the 
inspection instructions contained in the subject Boeing messages sent 
out on January 17, 2006, did not include certain steps. That section 
specifies that the chemical spot test and ultrasonic thickness 
inspections must be done again by following the procedures in the 
referenced service bulletin. In addition, paragraph (e) of this AD 
states that if the actions required by this AD have been done 
previously, they do not need to be done again. Therefore, we have made 
no change to the AD in this regard.

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 31 airplanes of the affected design in the 
worldwide fleet. This AD affects 1 airplane of U.S. registry. The 
required tests and inspections 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 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

    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 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.

[[Page 38887]]

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:

2008-13-25 Boeing: Amendment 39-15588. Docket No. FAA-2007-0395; 
Directorate Identifier 2007-NM-157-AD.

Effective Date

    (a) This airworthiness directive (AD) is effective August 12, 
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 
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.

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 Boeing Special Attention Service 
Bulletin 737-57-1289, dated June 13, 2007.
    (1) Except as provided by paragraph (h) of this AD: 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. Repeat the inspections thereafter at 
intervals not to exceed 1,000 flight cycles until the actions 
required by paragraph (g)(2) of this AD have been done. For any web 
panel with a material thickness of less than 0.037 inch, replace the 
web panel before further flight, in accordance with paragraph 3.B.7. 
of the Accomplishment Instructions of the service bulletin. Doing 
this replacement ends the repetitive inspections required by this 
paragraph.
    (2) Except as required by paragraph (g)(1) of this AD: 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 Aircraft Certification Office (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.

Material Incorporated by Reference

    (j) You must use Boeing Special Attention Service Bulletin 737-
57-1289, dated June 13, 2007, to do the actions required by this AD, 
unless the AD specifies otherwise.
    (1) 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.
    (2) For service information identified in this AD, contact 
Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 
98124-2207.
    (3) 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 June 10, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E8-14475 Filed 7-7-08; 8:45 am]
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