
[Federal Register Volume 77, Number 143 (Wednesday, July 25, 2012)]
[Proposed Rules]
[Pages 43547-43550]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-18147]


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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2012-0723; Directorate Identifier 2011-NM-137-AD]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: We propose to adopt a new airworthiness directive (AD) for 
certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 
series airplanes. This proposed AD was prompted by a report of cracks 
found in the skin at body station (STA) 540 just below stringer S-22L 
on a Model 737-700 series airplane. This proposed AD would require 
repetitive detailed and high frequency eddy current inspections for 
cracking of the skin around the eight fasteners common to the ends of 
the STA 540 bulkhead chords between stringers S-22 and S-23, left and 
right sides; and corrective actions and preventive modification if 
necessary. We are proposing this AD to detect and correct fatigue 
cracking in the skin, which can result in rapid decompression of the 
cabin.

DATES: We must receive comments on this proposed AD by September 10, 
2012.

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, 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: Deliver to Mail address above between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    For service information identified in this proposed AD, contact 
Boeing

[[Page 43548]]

Commercial Airplanes, Attention: Data & Services Management, P.O. Box 
3707, MC 2H-65, Seattle, WA 98124-2207; telephone 206-544-5000, 
extension 1; fax 206-766-5680; Internet https://www.myboeingfleet.com. 
You may review copies of the referenced service information at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, WA. For 
information on the availability of this material at the FAA, call 425-
227-1221.

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 (phone: 800-647-5527) is in the ADDRESSES 
section. Comments will be available in the AD docket shortly after 
receipt.

FOR FURTHER INFORMATION CONTACT: Alan Pohl, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue SW., Renton, WA 98057-3356; phone: 425-917-6450; fax: 
425-917-6590; email: alan.pohl@faa.gov.

SUPPLEMENTARY INFORMATION: 

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments about this proposal. Send your comments to an address listed 
under the ADDRESSES section. Include ``Docket No. FAA-2012-0723; 
Directorate Identifier 2011-NM-137-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 received a report of cracks found in the skin at body station 
(STA) 540 just below stringer S-22L on a Model 737-700 series airplane. 
Subsequent investigation revealed that the design at the STA 540 
bulkhead chords has insufficient load path where the chords meet 
between stringers S-22 and S-23 on both the left and right sides of the 
airplane. This condition, if not corrected, could result in fatigue 
cracking in the skin, which can result in rapid decompression of the 
cabin.

Relevant Service Information

    We reviewed Boeing Special Attention Service Bulletin 737-53-1294, 
dated March 31, 2011. The service information describes procedures for 
repetitive detailed and high frequency eddy current (HFEC) inspections 
for cracking of the skin around the eight fasteners common to the ends 
of the STA 540 bulkhead chords between stringers S-22 and S-23, and 
corrective actions and preventive modification if necessary. The 
preventive modification includes doing an open-hole HFEC inspection for 
cracking of the skin and STA 540 bulkhead chords, installing a new 
chord splice plate, and repair if necessary. The corrective actions 
include repairing cracking, and doing preventive modifications on any 
side on which cracking is not found.

FAA's Determination

    We are proposing this AD because we evaluated all the relevant 
information and determined the unsafe condition described previously is 
likely to exist or develop in other products of these same type 
designs.

Proposed AD Requirements

    This proposed AD would require accomplishing the actions specified 
in the service information described previously, except as discussed 
under ``Differences Between the Proposed AD and the Service 
Information.''

Differences Between the Proposed AD and the Service Information

    Boeing Special Attention Service Bulletin 737-53-1294, dated March 
31, 2011, 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:
     In accordance with a method that we approve; or
     Using data that meet the certification basis of the 
airplane, and that have been approved by the Boeing Commercial 
Airplanes Organization Designation Authorization (ODA) whom we have 
authorized to make those findings.

Clarification of Repetitive Inspections

    The Repeat Interval column of table 1 of paragraph 1.E., 
``Compliance,'' of Boeing Special Attention Service Bulletin 737-53-
1294, dated March 31, 2011, specifies repetitive detailed and HFEC 
inspections at intervals not to exceed 4,000 flight cycles, and the 
Accomplishment Instructions of Boeing Special Attention Service 
Bulletin 737-53-1294, dated March 31, 2011, specify repetitive detailed 
inspections only. We have determined that doing both repetitive 
detailed and HFEC inspections is necessary to address the unsafe 
condition of this AD.

Clarification of Post-Repair Inspections

    Paragraph (j), and Note 1 to paragraph (j), of this proposed AD 
clarify that the post-repair inspections specified in Table 2 of 
paragraph 1.E., ``Compliance,'' of Boeing Special Attention Service 
Bulletin 737-53-1294, dated March 31, 2011, are not required by this 
proposed AD.

Costs of Compliance

    We estimate that this proposed AD affects 903 airplanes of U.S. 
registry.
    We estimate the following costs to comply with this proposed AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
            Action                Labor cost      Parts cost   Cost per product       Cost on U.S. operators
----------------------------------------------------------------------------------------------------------------
Inspection (left and right     3 work-hours x             $0   $255 per          $230,265 per inspection cycle.
 sides).                        $85 per hour =                  inspection
                                $255 per                        cycle.
                                inspection
                                cycle.
----------------------------------------------------------------------------------------------------------------

    We estimate the following costs to do any necessary repairs and 
inspections that would be required based on the results of the proposed 
inspection. We have no way of determining the number of aircraft that 
might need these repairs:

[[Page 43549]]



                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
               Action                       Labor cost               Parts cost            Cost per  product
----------------------------------------------------------------------------------------------------------------
Preventive modification (each side).  6 work-hours x $85 per  $894                     $1,404.
                                       hour = $510.
Skin repair (each side).............  55 work-hours x $85     Up to $5,635             Up to $10,310.
                                       per hour = $4,675.
----------------------------------------------------------------------------------------------------------------

    According to the manufacturer, some of the costs of this proposed 
AD may be covered under warranty, thereby reducing the cost impact on 
affected individuals. We do not control warranty coverage for affected 
individuals. As a result, we have included all costs in our cost 
estimate.

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 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),
    (3) Will not affect intrastate aviation in Alaska, and
    (4) 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.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, 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 
airworthiness directive (AD):

The Boeing Company: Docket No. FAA-2012-0723; Directorate Identifier 
2011-NM-137-AD.

(a) Comments Due Date

    We must receive comments by September 10, 2012.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to The Boeing Company Model 737-600, -700, -
700C, -800, and -900 series airplanes; certificated in any category; 
as identified in Boeing Special Attention Service Bulletin 737-53-
1294, dated March 31, 2011.

(d) Subject

    Joint Aircraft System Component (JASC)/Air Transport Association 
(ATA) of America Code 53, Fuselage.

(e) Unsafe Condition

    This AD was prompted by a report of cracks found in the skin at 
body station (STA) 540 just below stringer S-22L. We are issuing 
this AD to detect and correct fatigue cracking in the skin, which 
can result in rapid decompression of the cabin.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(g) Inspection and Corrective Action

    (1) Except as required by paragraphs (g)(2), (i)(2), (i)(3), and 
(i)(4) of this AD, at the applicable time specified in table 1 of 
paragraph 1.E. ``Compliance,'' of Boeing Special Attention Service 
Bulletin 737-53-1294, dated March 31, 2011: Do detailed and high 
frequency eddy current (HFEC) inspections of the skin for cracking 
in the area around the eight fasteners securing the STA 540 bulkhead 
chords between stringers S-22 and S-23, and do all applicable 
corrective actions, in accordance with Parts 1, 2, 3, 4, and 5 of 
the Accomplishment Instructions of Boeing Special Attention Service 
Bulletin 737-53-1294, dated March 31, 2011, except as required by 
paragraph (i)(1) of this AD. If no cracking is found, repeat the 
detailed and HFEC inspections at the intervals specified in table 1 
of paragraph 1.E., ``Compliance,'' of Boeing Special Attention 
Service Bulletin 737-53-1294, dated March 31, 2011, except as 
required by paragraph (g)(2) of this AD, until the optional 
preventive modification specified in paragraph (h) of this AD is 
done. Do all applicable corrective actions before further flight.
    (2) For airplanes that have incorporated Boeing Business Jet 
Lower Cabin Altitude Supplemental Type Certificate (STC) ST01697SE 
(6,500 feet maximum cabin altitude in lieu of 8,000 feet), the 
flight-cycle related compliance times are different from those 
specified in Boeing Special Attention Service Bulletin 737-53-1294, 
dated March 31, 2011. All initial compliance times specified in 
total flight cycles or flight cycles must be reduced to half of 
those specified in Boeing Special Attention Service Bulletin 737-53-
1294, dated March 31, 2011. All repetitive interval compliance times 
specified in flight cycles must be reduced to one-quarter of those 
specified in Boeing Special Attention Service Bulletin 737-53-1294, 
dated March 31, 2011.

(h) Optional Preventive Modification

    Accomplishing the preventive modification, including an HFEC 
inspection for cracking of the skin and STA 540 bulkhead chords, and 
all applicable repairs, in accordance with paragraph 3.B, Part 2 or 
Part 4 (left side), and Part 3 or Part 5 (right side), of the 
Accomplishment Instructions of Boeing Special Attention Service 
Bulletin 737-53-1294, dated March 31, 2011, terminates the 
inspection requirements of paragraph (g) of this AD for the side on 
which the modification is done, except as required by paragraph 
(i)(1) of this AD.

(i) Exceptions to Service Bulletin Specifications

    (1) If any cracking is found during any inspection required by 
this AD, and Boeing Special Attention Service Bulletin 737-53-1294, 
dated March 31, 2011, specifies to contact Boeing for appropriate 
action: Before further flight, repair using a method approved in 
accordance with the procedures specified in paragraph (k) of this 
AD.

[[Page 43550]]

    (2) Where Boeing Special Attention Service Bulletin 737-53-1294, 
dated March 31, 2011, specifies to do the action after the original 
issue date of that service bulletin, this AD requires the compliance 
time after the effective date of this AD.
    (3) Where the Condition column of table 1 of paragraph 1.E., 
``Compliance,'' of Boeing Special Attention Service Bulletin 737-53-
1294, dated March 31, 2011, specifies a condition as of the original 
issue date of that service bulletin, this AD specifies the condition 
as of the effective date of this AD.
    (4) Note 1 of paragraph 3.A. of the Accomplishment Instructions 
of Boeing Special Attention Service Bulletin 737-53-1294, dated 
March 31, 2011, is to be disregarded when accomplishing the actions 
required by this AD.

(j) Post-Repair Inspections

    The post-repair inspections, specified in Table 2 of paragraph 
1.E., ``Compliance,'' of Boeing Special Attention Service Bulletin 
737-53-1294, dated March 31, 2011, are not required by this AD.

    Note 1 to paragraph (j) of this AD: The damage tolerance 
inspections specified in Table 2 of paragraph 1.E., ``Compliance,'' 
of Boeing Special Attention Service Bulletin 737-53-1294, dated 
March 31, 2011, may be used in support of compliance with Section 
121.1109(c)(2) or 129.109(c)(2) of the Federal Aviation Regulations 
(14 CFR 121.1109(c)(2) or 14 CFR 129.109(c)(2)). The corresponding 
actions specified in the Accomplishment Instructions of Boeing 
Special Attention Service Bulletin 737-53-1294, dated March 31, 
2011, are not required by this AD.

(k) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Seattle ACO, FAA, has the authority to approve 
AMOCs for this AD, if requested using the procedures found in 14 CFR 
39.19. In accordance with 14 CFR 39.19, send your request to your 
principal inspector or local Flight Standards District Office, as 
appropriate. If sending information directly to the manager of the 
ACO, it may be emailed to: 9-ANM-Seattle-ACO-AMOC-Requests@faa.gov.
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.
    (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 the 
Boeing Commercial Airplanes Organization Designation Authorization 
(ODA) that has been authorized by the Manager, Seattle Aircraft 
Certification Office (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.

(l) Related Information

    (1) For more information about this AD, contact Alan Pohl, 
Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft 
Certification Office, 1601 Lind Avenue SW., Renton, WA 98057-3356; 
phone: 425-917-6450; fax: 425-917-6590; email: alan.pohl@faa.gov.
    (2) For service information identified in this AD, contact 
Boeing Commercial Airplanes, Attention: Data & Services Management, 
P.O. Box 3707, MC 2H-65, Seattle, WA 98124-2207; telephone 206-544-
5000, extension 1; fax 206-766-5680; Internet https://www.myboeingfleet.com. You may review copies of the referenced 
service information at the FAA, Transport Airplane Directorate, 1601 
Lind Avenue SW., Renton, WA. For information on the availability of 
this material at the FAA, call 425-227-1221.

    Issued in Renton, Washington, on July 17, 2012.
Michael Kaszycki,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2012-18147 Filed 7-24-12; 8:45 am]
BILLING CODE 4910-13-P


