[Federal Register Volume 63, Number 135 (Wednesday, July 15, 1998)]
[Proposed Rules]
[Pages 38116-38118]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-18779]


 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
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 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
 
 ========================================================================
 

  Federal Register / Vol. 63, No. 135 / Wednesday, July 15, 1998 / 
Proposed Rules  

[[Page 38116]]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-148-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737 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 series 
airplanes. This proposal would require repetitive ultrasonic 
inspections to detect broken bolts that attach the terminal support 
fittings to the upper part of the Body Station 1088 bulkhead, and 
corrective actions, if necessary. This proposal also would require 
eventual replacement of the existing bolts with new, improved bolts, 
which, when accomplished, would terminate the requirements of the AD. 
This proposal is prompted by reports that bolts that attach the 
terminal support fittings to the upper part of the bulkhead were found 
broken. The actions specified by the proposed AD are intended to 
prevent such broken bolts, which could result in reduced structural 
integrity of the vertical fin installation and possible loss of the 
vertical fin.

DATES: Comments must be received by August 31, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-148-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    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.

FOR FURTHER INFORMATION CONTACT: Rick Kawaguchi, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-1153; 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 notice may be changed in 
light of the comments received.
    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 notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-NM-148-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. 98-NM-148-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports indicating that broken bolts were 
found in the terminal support fittings that attach the aft spar of the 
vertical fin to the upper part of the bulkhead at Body Station 1088 on 
Boeing Model 737 series airplanes. The broken bolts were made of H-11 
steel alloy. Bolts made of such material are susceptible to stress 
corrosion cracking. Such broken bolts, if not corrected, could result 
in reduced structural integrity of the vertical fin installation, and 
multiple broken bolts could result in loss of the vertical fin.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 737-53-
1107, Revision 3, dated August 26, 1993; as revised by Notices of 
Status Change 737-53-1107 NSC 3, dated June 9, 1994, and 737-53-1107 
NSC 4, dated September 22, 1994; and Boeing Service Bulletin 737-53-
1107, Revision 4, dated February 8, 1996. These service bulletins 
describe procedures for repetitive ultrasonic inspections to detect 
broken bolts that attach the terminal support fittings to the upper 
part of the Body Station 1088 bulkhead, and replacement of the existing 
bolts with new, improved bolts. The replacement includes removing the 
bolts, performing an eddy current inspection to detect cracking or 
corrosion of the bolt holes, oversizing the bolt holes, and installing 
new Inconel bolts. Installation of the new Inconel bolts would 
eliminate the need for the repetitive inspections described previously. 
Accomplishment of the actions specified in the service bulletins 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 bulletins and notices of status change described 
previously, except as discussed below.

Differences Between Proposed Rule and Service Bulletin

    Operators should note that, although the service bulletins specify 
that the

[[Page 38117]]

manufacturer may be contacted for disposition of certain repair 
conditions, this proposal would require the repair of those conditions 
to be accomplished in accordance with a method approved by the FAA.

Cost Impact

    There are approximately 1,485 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 630 airplanes of U.S. 
registry would be affected by this proposed AD.
    It would take approximately 3 work hours per airplane to accomplish 
the proposed inspection, at an average labor rate of $60 per work hour. 
Based on these figures, the cost impact of the inspection proposed by 
this AD on U.S. operators is estimated to be $113,400, or $180 per 
airplane, per inspection cycle.
    It would take approximately 9 work hours per airplane to accomplish 
the proposed replacement, at an average labor rate of $60 per work 
hour. Required parts would cost approximately $471 per airplane. Based 
on these figures, the cost impact of the replacement proposed by this 
AD on U.S. operators is estimated to be $636,930, or $1,011 per 
airplane.
    The cost impact figures discussed above are 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 AD were not adopted.

Regulatory Impact

    The regulations proposed herein would not have substantial direct 
effects 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. Therefore, in 
accordance with Executive Order 12612, it is determined that this 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    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 98-NM-148-AD.

    Applicability: Model 737 series airplanes, line numbers 1 
through 1485 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 (c) 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 broken bolts that attach the terminal support 
fittings to the upper part of the Body Station (BS) 1088 bulkhead, 
which could result in reduced structural integrity of the vertical 
fin installation and possible loss of the vertical fin, accomplish 
the following:
    (a) Within 18 months after the effective date of this AD, 
perform an ultrasonic inspection to detect broken bolts that attach 
the terminal support fittings to the upper part of the BS 1088 
bulkhead, in accordance with Boeing Service Bulletin 737-53-1107, 
Revision 3, dated August 26, 1993; as revised by Notice of Status 
Change 737-53-1107 NSC 3, dated June 9, 1994, and Notice of Status 
Change 737-53-1107 NSC 4, dated September 22, 1994; or Boeing 
Service Bulletin 737-53-1107, Revision 4, dated February 8, 1996.
    (1) If no broken bolt is found, repeat the ultrasonic inspection 
thereafter at intervals not to exceed 18 months.
    (2) If any broken bolt is found, prior to further flight, 
perform the actions specified in paragraph (b) of this AD.
    (b) Prior to the accumulation of 20 years since date of 
manufacture of the airplane, or within 18 months after the effective 
date of this AD, whichever occurs later, remove all 16 H-11 steel 
alloy bolts that attach the terminal support fittings to the upper 
part of the bulkhead, and perform an eddy current inspection to 
detect cracking or corrosion of the bolt holes, in accordance with 
Figure 2 of Boeing Service Bulletin 737-53-1107, Revision 3, dated 
August 26, 1993; as revised by Notice of Status Change 737-53-1107 
NSC 3, dated June 9, 1994, and Notice of Status Change 737-53-1107 
NSC 4, dated September 22, 1994; or Boeing Service Bulletin 737-53-
1107, Revision 4, dated February 8, 1996.
    (1) If no cracking or corrosion is found, prior to further 
flight, oversize all 16 bolt holes and install new Inconel bolts, in 
accordance with Figure 2 of the service bulletin. Accomplishment of 
this installation constitutes terminating action for the repetitive 
inspection requirements of this AD.
    (2) If any corrosion is found, prior to further flight, oversize 
the bolt hole within the limits specified in Figure 2, Step 4, of 
the service bulletin, and install a new Inconel bolt, in accordance 
with Figure 2 of the service bulletin. Accomplishment of the 
installation for all 16 bolt holes constitutes terminating action 
for the repetitive inspection requirements of this AD. If corrosion 
does not clean up within the limits specified in Figure 2, Step 4, 
of the service bulletin, prior to further flight, repair in 
accordance with a method approved by the Manager, Seattle Aircraft 
Certification Office (ACO), FAA, Transport Airplane Directorate.
    (3) If any cracking is found, prior to further flight, oversize 
the bolt hole within the limits specified in Figure 2, Step 5, of 
the service bulletin, and perform another eddy current inspection to 
ensure cracks have been removed, in accordance with Figure 2 of the 
service bulletin.
    (i) If, after oversizing, no cracking is found, prior to further 
flight, oversize the bolt hole again, and install a new Inconel 
bolt, in accordance with Figure 2 of the service bulletin. 
Accomplishment of the installation for all 16 bolt holes constitutes 
terminating action for the repetitive inspection requirements of 
this AD.
    (ii) If, after oversizing, any cracking is found, prior to 
further flight, repair in accordance with a method approved by the 
Manager, Seattle ACO.

    Note 2: Replacement of all H-11 steel alloy bolts accomplished 
prior to the effective date of this AD, in accordance with Boeing 
Service Bulletin 737-53-1107, dated October 15, 1987; Revision 1, 
dated June 22, 1989; or Revision 2, dated September 10, 1992; is 
considered acceptable for compliance with the applicable actions 
specified in paragraph (b) of this AD.

    (c) 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.


[[Page 38118]]


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

    (d) 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 July 8, 1998.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-18779 Filed 7-14-98; 8:45 am]
BILLING CODE 4910-13-U