[Federal Register Volume 72, Number 164 (Friday, August 24, 2007)]
[Proposed Rules]
[Pages 48594-48597]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-16657]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-29031; Directorate Identifier 2007-NM-130-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-600, -700, -700C, -
800, and -900 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 737-600, -700, -700C, -800, and -900 series 
airplanes. This proposed AD would require repetitive inspections of 
either the aft side or forward side of the aft pressure bulkhead for 
oil can conditions or bulges, a one-time inspection of the aft pressure 
bulkhead to identify any previously installed web repair, and 
corrective actions if necessary. This proposed AD results from web oil 
can conditions found on the aft pressure bulkhead of several airplanes. 
We are proposing this AD to detect and correct oil can conditions, 
bulges, or previous repairs in the aft pressure bulkhead, which could 
lead to web cracks and consequently result in rapid decompression of 
the airplane.

DATES: We must receive comments on this proposed AD by October 9, 2007.

ADDRESSES: Use one of the following addresses to submit comments on 
this proposed AD.
     DOT Docket Web site: Go to http://dms.dot.gov and follow 
the instructions for sending your comments electronically.
     Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your 
comments electronically.
     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.
     Fax: (202) 493-2251.
     Hand Delivery: Room W12-140 on the ground floor of the 
West Building, 1200 New Jersey Avenue, SE., Washington, DC, between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, 
Washington 98124-2207, for the service information identified in this 
proposed AD.

FOR FURTHER INFORMATION CONTACT: Howard Hall, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6430; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to submit any relevant written data, views, or 
arguments regarding this proposed AD. Send your comments to an address 
listed in the ADDRESSES section. Include the docket number ``FAA-2007-
29031; Directorate Identifier 2007-NM-130-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of the proposed AD. We will 
consider all comments received by the closing date and may amend the 
proposed AD in light of those comments.
    We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will 
also post a report summarizing each substantive verbal contact with FAA 
personnel concerning this proposed AD. Using the search function of 
that Web site, anyone can find and read the comments in any of our 
dockets, including the name of the individual who sent the comment (or 
signed the comment on behalf of an association, business, labor union, 
etc.). You may review DOT's complete Privacy Act Statement in the 
Federal Register published on April 11, 2000 (65 FR 19477-78), or you 
may visit http://dms.dot.gov.

Examining the Docket

    You may examine the AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Operations office between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays. The 
Docket Operations office (telephone (800) 647-5527) is located on the 
ground floor of the West Building at the DOT street address stated in 
the ADDRESSES section. Comments will be available in the AD docket 
shortly after the Docket Management System receives them.

Discussion

    We have received a report indicating that ``oil cans'' or 
``bulges'' have been found on the aft pressure bulkhead web of several 
Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. (An 
oil can is defined as an area on the pressure dome web that has visibly 
deviated forward from the initial contour of the pressured dome web. A 
bulge is defined as an area on the pressure dome web that has visibly 
deviated aft from the initial contour of the pressure dome web.) Oil 
can conditions or bulges in the aft pressure bulkhead, if not 
corrected, could lead to web cracks and consequently result in rapid 
decompression of the airplane.
    In addition, some operators may have previously repaired an oil can 
condition in accordance with the Boeing 737-600/700/700C/800/900 
Structural Repair Manuals (SRMs). The latest revision of

[[Page 48595]]

the SRM currently requires accomplishing an initial nondestructive 
testing (NDT) inspection of the repair and incorporating repetitive 
supplemental inspections of the repair into the airplane's maintenance 
program. Repair procedures in earlier revisions of the SRMs did not 
specify doing an initial NDT inspection and/or repetitive supplemental 
inspections. If the initial NDT inspection and repetitive supplemental 
inspections of the repair are not accomplished, web cracks could also 
develop and consequently result in loss of cabin pressurization.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 737-53A1253, dated 
May 18, 2007. The service bulletin describes procedures for doing 
repetitive general visual inspections of either the aft side or forward 
side of the aft pressure bulkhead for oil can conditions or bulges, a 
one-time general visual inspection of the aft pressure bulkhead to 
identify any previously installed web repair, and corrective actions as 
applicable. The corrective actions include:
     If the oil can condition is within a certain limit, (1) 
doing repetitive inspections of aft pressure bulkhead for web cracks 
until an oil can condition is repaired, or (2) before further flight, 
doing one-time NDT inspections of aft pressure bulkhead for web cracks 
and repairing the oil can condition.
     If the oil can condition is beyond a certain limit, doing 
a one-time NDT inspection of the affected web bay at the fastener 
locations where the web intersects the surrounding structure for cracks 
and repairing the oil can condition.
     If existing bulkhead repairs or bulging of tear straps 
prevent accomplishing low and high frequency eddy current inspections, 
contacting Boeing for instructions.
     Repairing any cracks or bulges found during any inspection 
and contacting Boeing for repair instructions if necessary.
     If a previously installed oil can repair is found, doing 
one-time NDT inspections of the web at the surrounding structure 
interfaces for cracks.
     If follow-on supplemental inspections of a previously 
installed repair are not being accomplished, determining the FAA-
approved, follow-on inspection procedures, thresholds, and repetitive 
intervals and incorporating them into the airplane maintenance program.
    Table 1 of paragraph 1.E. of the service bulletin recommends the 
following compliance times for the general visual inspections for oil 
can conditions or bulges in the aft pressure bulkhead: (1) The initial 
inspection at or before 15,000 total flight cycles or within 1,200 
flight cycles from the release date of the bulletin, (2) the first 
repetitive inspection thereafter at or before 10,000 flight cycles, and 
(3) the subsequent repetitive general visual inspections thereafter at 
or before 6,000 flight cycles. Table 1 also recommends repairing an oil 
can condition at or before 12,000 flight cycles, or before further 
flight, depending upon the extent of the oil can condition. Table 1 
also recommends repairing any crack or bulge before further flight.
    Table 2 of paragraph 1.E. of the service bulletin specifies a 
compliance time of 15,000 total flight cycles or within 1,200 flight 
cycles after the date on the service bulletin, for doing the one-time 
general visual inspection to identify repairs to the gore web (i.e., 
the tapered web segments). If any repair is found that does not have 
follow-on supplemental inspections, Table 2 specifies to determine the 
FAA-approved, follow-on inspection procedures, thresholds, and 
repetitive intervals and to incorporate them into the airplane 
maintenance program within 12 months after accomplishing the inspection 
given in Section 53-80-08-2R of the Boeing 737-600/700/700C/800/900 
SRMs.
    For Model 737-700 and -800 series airplanes on which Boeing 
Business Jet (BBJ) Lower Cabin Altitude Modification has been 
incorporated in accordance with Supplemental Type Certificate (STC) 
ST01697SE: Paragraph 1.E. of the service bulletin recommends that all 
initial compliance times (thresholds) specified in flight cycles be 
reduced to one-half of those specified in the service bulletin, and 
that all repeat interval compliance times specified in flight cycles be 
reduced to one-quarter of those specified in the service bulletin.
    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 
``Differences Between the Proposed AD and Service Bulletin.''

Differences Between the Proposed AD and Service Bulletin

    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.
    The service bulletin specifies to contact Boeing for further 
instructions in developing an FAA-approved supplemental inspection 
program if an aft pressure bulkhead is found that does not have 
supplemental inspections specified in either the Boeing 737-600/700/
700C/800/900 SRMs or the service bulletin. This proposed AD would 
instead require contacting the Manager, Seattle Aircraft Certification 
Office, or an Authorized Representative for the Boeing Commercial 
Airplanes Delegation Option Authorization Organization.
    If any repair is found that does not have follow-on supplemental 
inspections, Table 2 of paragraph 1.E. of the service bulletin 
specifies to determine the FAA-approved follow-on inspections 
procedures, thresholds, and repetitive intervals and to incorporate 
them into the airplane maintenance program within 12 months after 
accomplishing the inspection in Section 53-80-08-2R of the Boeing 737-
600/700/700C/800/900 SRMs. This proposed AD, however, would require 
that those corrective actions, if applicable, be done within 12 months 
after accomplishing the one-time general visual inspection of the aft 
pressure bulkhead for any previously installed web repair.
    Tables 1 and 2 of paragraph 1.E. of the service bulletin specify a 
compliance time of 15,000 total flight cycles or within 1,200 flight 
cycles from the release date or after the date on the service bulletin, 
for the general visual inspections. This proposed AD would require 
accomplishing the applicable inspection at the later of those 
compliance times. This proposed AD would also require starting the 
compliance time from the effective date of this AD, not from the 
service bulletin date.
    Although the service bulletin specifies to submit certain 
information

[[Page 48596]]

to the manufacturer, this proposed AD does not include that 
requirement. We do not need this information from operators.

Costs of Compliance

    There are about 1,755 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 600 airplanes of 
U.S. registry. The proposed inspection would take about 6 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 U.S. operators 
is $288,000, or $480 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.

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-2007-29031; Directorate Identifier 2007-NM-
130-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by October 
9, 2007.

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 Alert Service Bulletin 737-53A1253, dated May 
18, 2007.

Unsafe Condition

    (d) This AD results from web oil can conditions found on the aft 
pressure bulkhead of several airplanes. We are issuing this AD to 
detect and correct oil can conditions, bulges, or previous repairs 
in the aft pressure bulkhead, which could lead to web cracks and 
consequently 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.

Repetitive Inspections

    (f) At the applicable times specified in paragraph 1.E. of 
Boeing Alert Service Bulletin 737-53A1253, dated May 18, 2007, 
except as provided by paragraph (g) of this AD: Do repetitive 
general visual inspections of either the aft side or forward side of 
the aft pressure bulkhead for oil can conditions or bulges and a 
one-time general visual inspection of the aft pressure bulkhead to 
identify any previously installed web repair, and do all applicable 
corrective actions, by accomplishing all of the applicable actions 
specified in the Accomplishment Instructions of Boeing Alert Service 
Bulletin 737-53A1253, dated May 18, 2007, except as provided by 
paragraphs (h) and (i) of this AD.

Exceptions to Compliance Times

    (g) Where Tables 1 and 2 of paragraph 1.E. of Boeing Alert 
Service Bulletin 737-53A1253, dated May 18, 2007, specify a 
compliance time of ``at or before 15,000 total flight cycles or 
within 1,200 flight cycles'' for the general visual inspections, 
this AD would require accomplishing the applicable inspection at the 
later of those compliance times. Where Tables 1 and 2 of paragraph 
1.E. of the service bulletin specify counting the compliance time 
from the ``release date of this service bulletin'' or ``after the 
date on this service bulletin,'' this proposed requires starting the 
compliance time from the effective date of this AD. Where Table 2 of 
paragraph 1.E. of the service bulletin specifies to determine the 
FAA-approved, follow-on inspection procedures, thresholds, and 
repeat intervals and to incorporate them into the airplane 
maintenance program within 12 months after accomplishing the 
inspection given in Section 53-80-08-2R of the Boeing 737-600/700/
700C/800/900 Structural Repair Manuals (SRMs), this AD requires that 
those corrective actions, if applicable, be done within 12 months 
after accomplishing the one-time general visual inspection of the 
aft pressure bulkhead for any previously installed web repair as 
required by paragraph (f) of this AD.

Exceptions to Corrective Actions

    (h) If any crack or bulge is found during any inspection 
required by paragraph (f) of this AD and Boeing Alert Service 
Bulletin 737-53A1253, dated May 18, 2007, specifies to contact 
Boeing for repair instructions, before further flight, repair 
according to a method approved by the Manager, Seattle Aircraft 
Certification Office (ACO), FAA, or according to data meeting the 
certification basis of the airplane approved by an Authorized 
Representative for the Boeing 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. If a previously installed aft 
pressure bulkhead web repair is found during any inspection required 
by paragraph (f) of this AD, and the FAA-approved supplemental 
inspection program cannot be determined from either the Boeing 737-
600/700/700C/800/900 SRMs or the service bulletin, and the service 
bulletin specifies to contact Boeing for further instructions, 
within 12 months after accomplishing the inspection, contact the 
Manager, SACO, or an Authorized Representative for the Boeing 
Commercial Airplanes Delegation Option Authorization Organization to 
develop a supplemental inspection program.

No Reporting Requirement

    (i) Although Boeing Alert Service Bulletin 737-53A1253, dated 
May 18, 2007, specifies to submit certain information to the 
manufacturer, this AD does not require that action.

[[Page 48597]]

Alternative Methods of Compliance (AMOCs)

    (j)(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 14 CFR 25.571, Amendment 45, and the approval 
must specifically refer to this AD.

    Issued in Renton, Washington, on August 14, 2007.
Stephen P. Boyd,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E7-16657 Filed 8-23-07; 8:45 am]
BILLING CODE 4910-13-P