[Federal Register Volume 72, Number 182 (Thursday, September 20, 2007)]
[Proposed Rules]
[Pages 53706-53709]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-18554]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-29255; Directorate Identifier 2007-NM-085-AD]
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).

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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 doing repetitive 
internal eddy current and detailed inspections to detect cracked 
stringer tie clips; doing applicable corrective and related 
investigative actions, if necessary; and measuring the fastener spacing 
and the edge margin; as applicable. As a temporary alternative to doing 
the actions described previously, this proposed AD would require 
repetitive external general visual inspections of the skin and lap 
joints for cracks and evidence of overload resulting from cracked 
stringer tie clips, and applicable corrective actions if necessary. 
This proposed AD results from a report of several cracked stringer tie 
clips. We are proposing this AD to prevent multiple cracked stringer 
tie clips and damaged skin and frames, which could lead to the skin and 
frame structure developing cracks and consequent decompression of the 
airplane.

DATES: We must receive comments on this proposed AD by November 5, 
2007.

ADDRESSES: Use one of the following addresses to submit comments on 
this proposed AD.

[[Page 53707]]

     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: 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 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-
29255; Directorate Identifier 2007-NM-085-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 level 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 of 15 cracked stringer tie clips in the 
crown skin area between station (STA) 500B and STA 907 between stringer 
(S) 10L and S-10R, on a Boeing Model 737 airplane. The airplane had 
accumulated total 31,415 flight cycles. This airplane had three 
adjacent cracked clips at two consecutive body station frames (six 
clips total). The six stringer tie clips were cracked along the joint 
common to the stringer. The six total stringer tie clips were the same 
formed bonded stringer tie clips that were installed as terminating 
action in accordance with Boeing Service Bulletin 737-53-1085, Revision 
1, dated May 10, 1990.
    Stringer tie clip cracking along the joint common to the stringer 
occurs primarily as a result of cyclic loading associated with cabin 
pressure and flight loads. If three adjacent stringer tie clips on one 
frame crack, it could result in an inability of the fuselage frame 
structure to support operating loads. This could result in local skin 
buckling and deformation of the skin and frame. Multiple cracked 
stringer tie clips and damaged skin and frames, if not corrected, could 
lead to the skin and frame structure developing cracks, which could 
result in decompression of the airplane.

Other Relevant Rulemaking

    We previously issued AD 93-08-04, amendment 39-8551 (58 FR 25546, 
April 27, 1993), for certain Boeing Model 737-100, -200, and -200C 
series airplanes. That AD requires structural inspections of older 
airplanes and is part of the Aging Airplane Service Bulletin Structural 
Modification and Inspection Program. Boeing Service Bulletin 737-53-
1085, Revision 1, is one of several service bulletins required by that 
AD.
    This proposed AD would affect the requirements of AD 93-08-04 
pertaining to Boeing Service Bulletin 737-53-1085, Revision 1.
    We previously issued AD 2002-07-08, amendment 39-12702 (67 FR 
17917, April 12, 2002), applicable to certain Boeing Model 737-200, -
200C, -300, -400, and -500 series airplanes. That AD requires 
repetitive inspections to find cracking of the lower skin at the lower 
row of fasteners in the lap joints of the fuselage, and repair of 
cracking found. That AD also requires modification of the fuselage lap 
joints at certain locations, which constitutes terminating action for 
certain repetitive inspections.
    This proposed AD would not affect the current requirements of AD 
2002-07-08.

Relevant Service Information

    We have reviewed Boeing Special Attention Service Bulletin 737-53-
1268, dated August 25, 2006. This service bulletin supersedes Boeing 
Service Bulletin 737-53-1085, Revision 1.
    The service bulletin describes one required inspection and one 
temporary alternative inspection. Inspection A, the one required 
inspection, involves the following:
     Doing repetitive internal eddy current and detailed 
inspections to detect cracked stringer tie clips. The inspection area 
is from STA 559 to STA 887, STA 360 to STA 540, and STA 907. The 
inspections from STA 559 to STA 887 are identical to those specified in 
Boeing Service Bulletin 737-53-1085, Revision 1. If the terminating 
action was done in accordance with Boeing Service Bulletin 737-53-1085, 
the inspections need to be restarted in accordance with Boeing Special 
Attention Service Bulletin 737-53-1268.
     Doing applicable corrective and related investigative 
actions, if necessary. The corrective actions include replacing any 
cracked stringer tie clip with a new clip, contacting Boeing for repair 
instructions, and repairing any damaged lap joints; as applicable. The 
related investigative actions include doing an internal detailed 
inspection to detect damaged or deformed skin and frame and to detect 
damaged lap joints, and doing internal eddy current inspections to 
detect cracked lap joints; as applicable.
     Measuring the fastener spacing and the edge margin; as 
applicable.
    The initial compliance time for Inspection A is before the 
accumulation of 25,000 or 35,000 total flight cycles (as applicable), 
or within 2 or 3 years (as applicable) after the date of the service 
bulletin, whichever occurs later. The repeat interval for Inspection A 
is 15,000 or 20,000 flight cycles (as applicable).

[[Page 53708]]

    Inspection B, which is a temporary alternative to doing Inspection 
A, involves the following:
     Doing repetitive external general visual inspections of 
the skin and lap joints for cracks and evidence of overload resulting 
from cracked stringer tie clips, and
     Doing applicable corrective actions if necessary. The 
corrective actions include contacting Boeing for repair instructions, 
and repairing any cracked or damaged lap joint and skin.
    For Inspection B, the threshold for the initial compliance times 
ranges between 37,500 and 47,500 total flight cycles, and the grace 
period for the initial compliance times is 25,000 flight cycles or 6 or 
12 months, depending on the number of flight cycles on the airplane. 
Inspection B must be done before exceeding an inspection period ranging 
from 5,000 to 50,000 total flight cycles. The repeat interval for 
Inspection B is 2,500 flight cycles.
    The service bulletin also describes procedures for an optional eddy 
current inspection to detect damaged stringer tie clips and replacement 
of any cracked clip with a new clip. The optional inspection can be 
done in addition to and at the same time as Inspection A described 
previously. The optional inspection will detect damaged stringer clips 
earlier than the detailed inspection, which may prevent future costly 
repairs.
    Accomplishing the actions specified in the service information is 
intended to adequately address the unsafe condition.
    The service bulletin refers to Boeing Service Bulletin 737-53A1177, 
Revision 6, dated May 31, 2001, as an additional source of service 
information for doing an internal eddy current inspection of the lap 
joint for certain airplane configurations.

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 Information.''

Differences Between the Proposed AD and Service Information

    The service information 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 2,685 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.

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                 Number of U.S.-
            Action              Work hours \1\   Average labor      Cost per       registered     Fleet cost \1\
                                                 rate per hour    airplane \1\      airplanes
----------------------------------------------------------------------------------------------------------------
Inspection A.................  Between 40 and              $80  Between $3,200              787  Between
                                103.                             and $8,240,                      $2,518,400 and
                                                                 per inspection                   $6,484,880,
                                                                 cycle.                           per inspection
                                                                                                  cycle.
Inspection B (temporary        Between 2 and                80  Between $160                787  Between
 alternative to Inspection A).  109.                             and $8,720.                      $125,920 and
                                                                                                  $6,862,640,
                                                                                                  per inspection
                                                                                                  cycle.
----------------------------------------------------------------------------------------------------------------
\1\ Depending on the airplane configuration.

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.

[[Page 53709]]

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-2007-29255; Directorate Identifier 2007-NM-
085-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by November 
5, 2007.

Affected ADs

    (b) AD 93-08-04, amendment 39-8551.

Applicability

    (c) This AD applies to Boeing Model 737-100, -200, -200C, -300, 
-400, and -500 series airplanes, certificated in any category; as 
identified in Boeing Service Bulletin 737-53-1268, dated August 25, 
2006.

Unsafe Condition

    (d) This AD results from a report of several cracked stringer 
tie clips. We are issuing this AD to prevent multiple cracked 
stringer tie clips and damaged skin and frames, which could lead to 
the skin and frame structure developing cracks 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.

Service Bulletin References

    (f) The term ``the service bulletin,'' as used in this AD, means 
the Accomplishment Instructions of Boeing Service Bulletin 737-53-
1268, dated August 25, 2006.

Inspection A: Required Internal Inspections, Applicable Corrective and 
Related Investigative Actions, and Measurement

    (g) Do repetitive internal eddy current and detailed inspections 
to detect cracked stringer tie clips; do applicable corrective and 
related investigative actions, if necessary; and measure the 
fastener spacing and the edge margin; as applicable. Do all 
applicable actions at the applicable compliance times and repeat 
intervals identified in tables 2 through 8 inclusive of paragraph 
1.E., ``Compliance,'' of the service bulletin; except as provided by 
paragraphs (i), (j), and (k) of this AD. Do all applicable actions 
in accordance with the Accomplishment Instructions of the service 
bulletin, except as provided by paragraph (m) of this AD.

    Note 1: The service bulletin refers to Boeing Service Bulletin 
737-53A1177, Revision 6, dated May 31, 2001, as an additional source 
of service information for doing an internal eddy current inspection 
of the lap joint for certain airplane configurations.

Inspection B: Temporary Alternative External Inspections and Corrective 
Actions

    (h) As a temporary alternative to doing the actions required by 
paragraph (g) of this AD, do repetitive external general visual 
inspections of the skin and lap joints for cracks and evidence of 
overload resulting from cracked stringer tie clips, and applicable 
corrective actions if necessary. Do all applicable actions at the 
applicable compliance times and repeat intervals identified in 
tables 9 through 12 inclusive of paragraph 1.E., ``Compliance,'' of 
the service bulletin, but not to exceed the flight cycles in the 
``Inspection Period Allowed'' column of the tables; except as 
provided by paragraphs (i) and (l) of this AD. Do all applicable 
actions in accordance with the Accomplishment Instructions of the 
service bulletin, except as provided by paragraph (m) of this AD.

    Note 2: The eddy current inspection along the stringer tie clip 
radius to detect damage and replacement, as applicable, specified in 
paragraph 3.B.5. of the Accomplishment Instructions of the service 
bulletin are not required by this AD. The actions are optional and 
can be done in addition to and at the same time as the actions 
required by paragraph (g) of this AD.

Exceptions to Service Information

    (i) Where the service bulletin specifies a compliance time after 
the date of the service bulletin, this AD requires compliance within 
the specified compliance time after the effective date of this AD.
    (j) For Model 737-100, -200, and -200C series airplanes, on 
which Boeing Service Bulletin 737-53-1085, Revision 1, dated May 10, 
1990, has not been done in accordance with AD 93-08-04: As of the 
effective date of this AD, do the applicable inspections from STA 
559 to STA 887 in accordance with paragraph (g) of this AD, at the 
applicable compliance times specified in paragraph (b) of AD 93-08-
04.
    (k) In the first row of tables 5 and 6 of paragraph 1.E., 
``Compliance,'' of the service bulletin, where the service bulletin 
specifies a compliance time of before 25,000 total airplane flight 
cycles, this AD requires a compliance time of before the 
accumulation of 25,000 total flight cycles, or within 2 years after 
the effective date of this AD, whichever occurs later.
    (l) Where the service bulletin specifies no starting point 
(e.g., ``after the date on the service bulletin'') for a grace 
period, this AD requires compliance within the specified grace 
period after the effective date of this AD.
    (m) Where the service bulletin specifies to contact Boeing for 
appropriate action: Before further flight, repair the discrepancy 
using a method approved in accordance with the procedures specified 
in paragraph (o) of this AD.

Certain Actions End Certain Requirements of AD 93-08-04

    (n) Accomplishment of the internal eddy current and detailed 
inspections for STA 559 to STA 887 in accordance with paragraph (g) 
of this AD constitutes compliance with the inspections required by 
paragraph (a) of AD 93-08-04, as it pertains to Boeing Service 
Bulletin 737-53-1085, Revision 1, dated May 10, 1990. Accomplishment 
of the internal eddy current and detailed inspections does not 
terminate the remaining requirements of AD 93-08-04, as it applies 
to other service bulletins. Operators are required to continue to 
inspect and/or modify per the other service bulletins listed in that 
AD.

Alternative Methods of Compliance (AMOCs)

    (o)(1) The Manager, Seattle Aircraft Certification Office (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) 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 September 12, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E7-18554 Filed 9-19-07; 8:45 am]
BILLING CODE 4910-13-P