[Federal Register Volume 71, Number 74 (Tuesday, April 18, 2006)]
[Proposed Rules]
[Pages 19835-19838]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-5723]


=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

[Docket No. FAA-2006-24496; Directorate Identifier 2005-NM-141-AD]

14 CFR Part 39

RIN 2120-AA64


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

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

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 
series airplanes. This proposed AD would require repetitive inspections 
to detect cracks in the vertical beam webs of the body station (BS) 178 
bulkhead, and corrective actions if necessary. This proposed AD also 
would require a terminating modification for the repetitive 
inspections. This proposed AD results from reports of numerous cracks 
in the vertical beam webs. We are proposing this AD to prevent fatigue 
cracks in certain vertical beam webs, which could result in loss of 
structural integrity of the BS 178 bulkhead, and consequently could 
impair the operation of the control cables for the elevators, speed 
brakes, and landing gear, or could cause the loss of cabin pressure.

DATES: We must receive comments on this proposed AD by June 2, 2006.

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: Docket Management Facility, U.S. Department of 
Transportation, 400 Seventh Street SW., Nassif Building, room PL-401, 
Washington, DC 20590.
     Fax: (202) 493-2251.
     Hand Delivery: Room PL-401 on the plaza level of the 
Nassif Building, 400 Seventh Street SW., 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 98055-4056; 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-2006-
24496; Directorate Identifier 2005-NM-141-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

[[Page 19836]]

person at the Docket Management Facility office between 9 a.m. and 5 
p.m., Monday through Friday, except Federal holidays. The Docket 
Management Facility office (telephone (800) 647-5227) is located on the 
plaza level of the Nassif 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 several reports of numerous cracks in the vertical 
beam webs at buttock lines (BL) 5.7 and 17.0 of the body station (BS) 
178 bulkhead on Boeing Model 737-100, -200, -200C, -300, -400, and -500 
series airplanes, line numbers 1 through 3132 inclusive. Five cracks 
nearly severed the upper web of the BL 17.0 vertical beam. One crack 
severed the lower web of the BL 17.0 vertical beam. The cracks initiate 
from holes in the web of the vertical beams and at fastener locations 
common to the forward and aft chords of the vertical beams. These 
airplanes have accumulated between 15,556 and 64,881 total flight 
cycles. The cracks occur as a result of structural fatigue due to cabin 
pressure loads. Fatigue cracks in the vertical beam webs at BL 5.7 and 
17.0 of BS 178 bulkhead, if not detected and corrected, could result in 
loss of structural integrity of the bulkhead, which could impair the 
operation of the control cables for the elevators, speed brakes, and 
landing gear, or could cause the loss of cabin pressure.

Other Relevant Rulemaking

    We have previously issued AD 2000-05-29, amendment 39-11639 (65 FR 
14834, March 20, 2000), applicable to Boeing Model 737-100, -200, -300, 
-400, and -500 series airplanes, line numbers 1 through 2,737 
inclusive. That AD requires repetitive inspections to detect fatigue 
cracking of the web, vertical chords, and side chords of the forward 
pressure bulkhead, and repair if necessary. That AD also provides for 
certain optional preventative modifications (reference Boeing Alert 
Service Bulletin 737-53A1173, Revision 3, dated May 6, 1999), which, if 
done, ends the repetitive inspection requirements for the affected 
areas.
    In addition, we have previously issued AD 2001-02-01, amendment 39-
12085 (66 FR 7576, January 24, 2001), applicable to Boeing Model 737-
300, -400, and -500 series airplanes, line numbers 2,738 through 3,071 
inclusive. That AD requires repetitive inspections to detect fatigue 
cracking in the vertical chords and side chords of the forward pressure 
bulkhead, and repair if necessary. That AD also requires certain 
preventative modifications (reference Boeing Alert Service Bulletin 
737-53A1208, dated May 6, 1999), which ends the repetitive inspection 
requirements for the affected areas.
    For certain airplanes, accomplishing the preventative modification 
in this proposed AD may affect accomplishing the preventative 
modifications specified as optional in AD 2000-05-29 and required by AD 
2001-02-01. See ``Effect of Accomplishing Concurrent Requirements'' 
section for further information.

Relevant Service Information

    We have reviewed Boeing Service Bulletin 737-53A1225, Revision 1, 
dated April 14, 2005. The service bulletin describes procedures for 
repetitive high frequency eddy current (HFEC) and detailed inspections 
to detect cracks in the BS 178 vertical beam webs, and corrective 
actions if necessary. The corrective actions include repairing or 
replacing any cracked vertical beam web and associated parts with a new 
vertical beam web and associated parts. The service bulletin also 
describes procedures for a preventative modification (i.e., repairing 
or replacing the vertical beams at BL 5.7 and 17.0 of the BS 178 
bulkhead), which ends the repetitive inspections. For certain 
airplanes, Boeing Service Bulletin 737-53A1225 recommends accomplishing 
concurrently the terminating preventative modifications specified in 
Boeing Alert Service Bulletin 737-53A1173 or 737-53A1208, as 
applicable, due to common access and structure.
    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 Proposed AD and Service Information

    Boeing Service Bulletin 737-53A1225 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.

Effect of Accomplishing Concurrent Requirements

    Operators who have not done the preventative modifications 
specified in AD 2000-05-29 (reference Boeing Alert Service Bulletin 
737-53A1173, Revision 3, dated May 6, 1999) or required by AD 2001-02-
01 (reference Boeing Alert Service Bulletin 737-53A1208, dated May 6, 
1999), as applicable, as of the effective date of this AD, must do 
those preventative modifications concurrently with the preventative 
modification of this proposed AD in accordance with Boeing Service 
Bulletin 737-53A1225, Revision 1. We realize that the concurrent 
requirements of this proposed AD will force some operators to do the 
preventative modifications required by AD 2001-02-01 early and to do 
the optional preventative modification specified in AD 2000-05-29. 
However, accomplishing the applicable preventative modifications 
together is necessary to avoid repeated disassembly and re-assembly of 
common parts, which increases the likelihood of additional assembly 
errors.

Costs of Compliance

    There are about 3,132 airplanes of the affected design in the 
worldwide fleet. The following table provides the estimated costs for 
U.S. operators to comply with this proposed AD.

[[Page 19837]]



                                                                     Estimated Costs
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                   Average
              Action                 Work hours   labor rate          Parts            Cost per airplane       Number of  U.S.-          Fleet cost
                                                   per hour                                                  registered airplanes
--------------------------------------------------------------------------------------------------------------------------------------------------------
Inspection, per inspection cycle..            4          $80  None.................  $320, per inspection   1,172................  $375,040, per
                                                                                      cycle.                                        inspection cycle.
Preventative Modification.........          240           80  Between $960 and       Between $20,160 and    1,172 (720 airplanes   Between $14,515,200
                                                               $13,620 depending on   $32,820 depending on   have had the           and $23,630,400.
                                                               kit purchased.         configuration.         preventative
                                                                                                             modification
                                                                                                             incorporated).
--------------------------------------------------------------------------------------------------------------------------------------------------------

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-2006-24496; Directorate Identifier 2005-NM-
141-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by June 2, 
2006.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-100, -200, -200C, -300, 
-400, -500 series airplanes, certificated in any category; as 
identified in Boeing Service Bulletin 737-53A1225, Revision 1, dated 
April 14, 2005.

Unsafe Condition

    (d) This AD results from reports of numerous cracks in the 
vertical beam webs. We are issuing this AD to prevent fatigue cracks 
in certain vertical beam webs, which could result in loss of 
structural integrity of the body station (BS) 178 bulkhead, and 
consequently could impair the operation of the control cables for 
the elevators, speed brakes, and landing gear, or could cause the 
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) At the applicable times specified in Table 1 of this AD, do 
a high frequency eddy current (HFEC) inspection and detailed 
inspection to detect cracks in the BS 178 vertical beam webs, in 
accordance with the Accomplishment Instructions of Boeing Service 
Bulletin 737-53A1225, Revision 1, dated April 14, 2005.

                       Table 1.--Compliance Times
------------------------------------------------------------------------
                                                         And repeat the
                                                            HFEC and
   For airplanes on which--            Inspect--            detailed
                                                           inspections
                                                         thereafter at--
------------------------------------------------------------------------
(1) An HFEC or a detailed       Before the              Intervals not to
 inspection specified in         accumulation of         exceed 6,000
 Boeing Service Bulletin 737-    15,000 total flight     flight cycles.
 53A1225, dated October 19,      cycles, or within
 2000, has not been done as of   4,500 flight cycles
 the effective date of this AD.  after the effective
                                 date of this AD,
                                 whichever occurs
                                 later.
(2) An HFEC or detailed         Within 6,000 flight     Intervals not to
 inspection specified in         cycles since the last   exceed 6,000
 Boeing Service Bulletin 737-    HFEC inspection, or     flight cycles.
 53A1225, dated October 19,      within 1,200 flight
 2000, has been done before      cycles since the last
 the effective date of this AD.  detailed inspection,
                                 whichever occurs
                                 later.
------------------------------------------------------------------------


[[Page 19838]]

Corrective Actions

    (g) If any crack is detected during any inspection required by 
paragraph (f) of this AD, before further flight, repair or replace 
the vertical beam web and associated parts with a new vertical beam 
web, in accordance with the Accomplishment Instructions of Boeing 
Service Bulletin 737-53A1225, Revision 1, dated April 14, 2005, 
except as provided by paragraph (h) of this AD.
    (h) If any damage is beyond the scope of the service bulletin or 
structural repair manual, before further flight, repair the damaged 
vertical beam web in accordance with a method approved by the 
Manager, Seattle Aircraft Certification Office (ACO), FAA; or using 
a method approved in accordance with paragraph (l) of this AD.

Terminating Preventative Modification

    (i) Before the accumulation of 50,000 total flight cycles, or 
within 25,000 flight cycles after the effective date of this AD, 
whichever occurs later, repair or replace the vertical beams at 
buttock lines (BL) 5.7 and 17.0 of the BS 178 bulkhead, in 
accordance with the Accomplishment Instructions of Boeing Service 
Bulletin 737-53A1225, Revision 1, dated April 14, 2005. 
Accomplishing the repair or replacement ends the repetitive 
inspections required by paragraph (f) of this AD.
    (j) Actions done before the effective date of this AD in 
accordance with Boeing BOECOM M-7200-01-00546, dated March 1, 2001, 
are acceptable for compliance with the requirements of paragraph (i) 
of this AD.

Concurrent Requirements

    (k) For Group 1 airplanes identified in Boeing Service Bulletin 
737-53A1225, Revision 1, dated April 14, 2005: Concurrently with the 
requirements of paragraph (i) of this AD, unless already done before 
the effective date of this AD, do the preventative modifications of 
the center web, vertical chords, and side chord areas, including the 
side chord areas at water line 207, of the forward pressure 
bulkhead, specified in paragraph (c) of AD 2000-05-29, amendment 39-
11639 (reference Boeing Alert Service Bulletin 737-53A1173, Revision 
3, dated May 6, 1999).
    (l) For Group 2 airplanes identified in Boeing Service Bulletin 
737-53A1225, Revision 1, dated April 14, 2005: Concurrently with the 
requirements of paragraph (i) of this AD, but no later than the time 
specified in AD 2001-02-01, amendment 39-12085, do the preventative 
modifications of the vertical and side chord areas of the forward 
pressure bulkhead required by paragraph (c) of AD 2001-02-01 
(reference Boeing Alert Service Bulletin 737-53A1208, dated May 6, 
1999).

Alternative Methods of Compliance (AMOCs)

    (m)(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) Before using any AMOC approved in accordance with Sec.  
39.19 on any airplane to which the AMOC applies, notify the 
appropriate principal inspector in the FAA Flight Standards 
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 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 April 4, 2006.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E6-5723 Filed 4-17-06; 8:45 am]
BILLING CODE 4910-13-P