[Federal Register Volume 66, Number 71 (Thursday, April 12, 2001)]
[Proposed Rules]
[Pages 18880-18882]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-9020]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-403-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-700 and -800 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 737-700 and -
800 series airplanes. This proposal would require inspections of 
certain tension bolts at the attachment of the aft pressure bulkhead to 
the fuselage at body station 1016 to determine if the correct parts are 
installed, and corrective action, if necessary. This action is 
necessary to prevent fatigue cracking along the bulkhead-to-fuselage 
attachment, which could result in structural failure of the aft 
pressure bulkhead and consequent rapid decompression of the airplane. 
This action is intended to address the identified unsafe condition.

DATES: Comments must be received by May 29, 2001.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-403-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9 a.m. and 3 p.m., Monday through Friday, except 
Federal holidays. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. Comments sent via fax or the Internet must 
contain ``Docket No. 2000-NM-403-AD'' in the subject line and need not 
be submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 for Windows or 
ASCII text.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

[[Page 18881]]


FOR FURTHER INFORMATION CONTACT: Nenita Odesa, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
227-2557; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this action may be changed in 
light of the comments received.
    Submit comments using the following format:
     Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
     For each issue, state what specific change to the proposed 
AD is being requested.
     Include justification (e.g., reasons or data) for each 
request.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2000-NM-403-AD.'' The postcard will be date stamped 
and returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 2000-NM-403-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received a report that numerous Boeing Model 737-700 
and -800 series airplanes may have been delivered with the wrong 
tension bolts or nuts installed at the attachment of the aft pressure 
bulkhead to the fuselage at body station (BS) 1016. The subject tension 
bolts attach the forward frame chord, the Y-chord, and the aft frame 
chord to the fuselage, and the bolts may be the wrong length or the 
wrong nut could be installed. If incorrect tension bolts are installed, 
the fatigue life of the aft pressure bulkhead may be reduced. This 
condition, if not corrected, could result in fatigue cracking along the 
bulkhead-to-fuselage attachment, structural failure of the aft pressure 
bulkhead, and consequent rapid decompression of the airplane.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 737-53-
1212, including Appendix A, dated August 13, 1998, which describes 
procedures for various inspections of tension bolts at the attachment 
of the aft pressure bulkhead to the fuselage at BS 1016 to determine 
whether the correct parts are installed. The inspections include:
     A visual inspection of the nuts above stringer 10 on both 
sides of the airplane, measuring the height of the nut to determine if 
the correct nut is installed.
     An inspection of bolts using a special measuring gage to 
determine if any long bolts are installed.
     A visual inspection of bolts to determine if any short 
bolts are installed.
     A torque test of the nuts on any long bolts found above 
the main deck floor to determine whether the bolts are properly 
clamped.
    Corrective actions are also described in the service bulletin. If 
any long or short bolt is installed, the corrective action is 
replacement of the bolt and nut, as applicable. In cases where short 
bolts are installed between two adjacent stringer end fittings or at 
stringer end fittings, repetitive inspections of the nuts to determine 
if bolts are properly clamped are provided as an option that extends 
the compliance time for the replacement of bolts. The compliance time 
for the replacement of bolts varies by condition, and Section 1.D. 
(``Compliance'') of the service bulletin contains a table summarizing 
the conditions, appropriate corrective actions, and compliance times.
    Accomplishment of the actions specified in the service bulletin is 
intended to adequately address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require accomplishment of the actions specified in 
the service bulletin described previously, except as discussed below.

Differences Between Proposed Rule and Service Bulletin

    Operators should note that, although the service bulletin refers to 
visual inspections, this proposed AD identifies these inspections as 
``special detailed inspections.'' A note defining a special detailed 
inspection is included after paragraph (a) of this AD.
    Operators should also note that, although the service bulletin 
specifies that the manufacturer must be contacted for disposition of 
certain repair conditions, this proposed AD would require those 
conditions to be repaired per a method approved by the FAA, or per data 
meeting the type certification basis of the airplane approved by a 
Boeing Company Designated Engineering Representative who has been 
authorized by the FAA to make such findings.

Cost Impact

    There are approximately 31 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 14 airplanes of U.S. registry 
would be affected by this proposed AD, that it would take approximately 
2 work hours per airplane to accomplish the proposed inspections, and 
that the average labor rate is $60 per work hour. Based on these 
figures, the cost impact of the proposed AD on U.S. operators is 
estimated to be $1,680, or $120 per airplane.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the proposed requirements of 
this AD action, and that no operator would accomplish those actions in 
the future if this proposed AD were not adopted. The cost impact 
figures discussed in AD rulemaking actions represent only the time 
necessary to perform the specific actions actually required by the AD. 
These figures typically do not include incidental costs, such as the 
time required to gain access and close up, planning time, or time 
necessitated by other administrative actions.

Regulatory Impact

    The regulations proposed herein would not have a substantial direct 
effect on the States, on the relationship

[[Page 18882]]

between the national Government and the States, or on the distribution 
of power and responsibilities among the various levels of government. 
Therefore, it is determined that this proposal would not have 
federalism implications under Executive Order 13132.
    For the reasons discussed above, I certify that 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); 
and (3) if promulgated, 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. A copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (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. Section 39.13 is amended by adding the following new 
airworthiness directive:

Boeing:  Docket 2000-NM-403-AD.

    Applicability: Model 737-700 and -800 series airplanes; line 
numbers 4, 6, 9 through 20 inclusive, 29, and 31 through 46 
inclusive; certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (d) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent fatigue cracking along the bulkhead-to-fuselage 
attachment, which could result in structural failure of the aft 
pressure bulkhead and consequent rapid decompression of the 
airplane, accomplish the following:

Inspections and Corrective Actions

    (a) Prior to the accumulation of 3,000 total flight cycles, or 
within 90 days after the effective date of this AD, whichever occurs 
later, do one-time special detailed inspections of tension bolts at 
the attachment of the aft pressure bulkhead to the fuselage at body 
station 1016 to determine whether the correct parts are installed, 
per the Accomplishment Instructions of Boeing Service Bulletin 737-
53-1212, including Appendix A, dated August 13, 1998.
    (1) If any long bolt is found above the main deck floor, do 
paragraphs (a)(1)(i) and (a)(1)(ii) of this AD.
    (i) Before further flight, do a torque test of the nut on the 
long bolt to determine whether the bolt is properly clamped.
    (ii) Replace the bolt and nut, as applicable, with new parts, 
per the service bulletin, except as provided by paragraph (c) of 
this AD. The correct replacement parts are listed in Figure 4 of the 
service bulletin. Do the replacement no later than the compliance 
time specified in the compliance table in Section 1.D. 
(``Compliance'') of the service bulletin. For the purposes of this 
AD, compliance times stated in flight cycles and years are to be 
counted from the time of the inspection per paragraph (a) of this 
AD.
    (2) For any long or short bolt other than those identified in 
paragraph (a)(1) of this AD, replace the bolt and nut, as 
applicable, with new parts, per the service bulletin, except as 
provided by paragraph (c) of this AD. The correct replacement parts 
are listed in Figure 4 of the service bulletin. Do the replacement 
no later than the compliance time specified in the compliance table 
in Section 1.D. (``Compliance'') of the service bulletin. For the 
purposes of this AD, compliance times stated in flight cycles and 
years are to be counted from the time of the inspection per 
paragraph (a) of this AD.

    Note 2: For the purposes of this AD, a special detailed 
inspection is defined as: ``An intensive examination of a specific 
item(s), installation, or assembly to detect damage, failure, or 
irregularity. The examination is likely to make extensive use of 
specialized inspection techniques and/or equipment. Intricate 
cleaning and substantial access or disassembly procedures may be 
required.''

Repetitive Inspections

    (b) Where short bolts are installed between two adjacent 
stringer end fittings or at stringer end fittings, doing repetitive 
inspections of the nuts to determine if bolts are properly clamped, 
per Boeing Service Bulletin 737-53-1212, including Appendix A, dated 
August 13, 1998, extends the compliance time for the replacement of 
bolts, per the compliance table in Section 1.D. (``Compliance'') of 
the service bulletin.

Exception for Certain Repair Conditions

    (c) Where Boeing Service Bulletin 737-53-1212, including 
Appendix A, dated August 13, 1998, specifies to contact Boeing for 
replacement instructions: Before further flight, replace per a 
method approved by the Manager, Seattle Aircraft Certification 
Office (ACO), FAA; or per data meeting the type certification basis 
of the airplane approved by a Boeing Company Designated Engineering 
Representative who has been authorized by the Manager, Seattle ACO, 
to make such findings. For a repair method to be approved by the 
Manager, Seattle ACO, as required by this paragraph, the approval 
letter must specifically reference this AD.

Alternative Methods of Compliance

    (d) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Seattle ACO. Operators shall submit 
their requests through an appropriate FAA Principal Maintenance 
Inspector, who may add comments and then send it to the Manager, 
Seattle ACO.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

Special Flight Permits

    (e) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.

    Issued in Renton, Washington, on April 5, 2001.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-9020 Filed 4-11-01; 8:45 am]
BILLING CODE 4910-13-U