[Federal Register Volume 64, Number 34 (Monday, February 22, 1999)]
[Rules and Regulations]
[Pages 8500-8502]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-3935]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-148-AD; Amendment 39-11048; AD 99-04-23]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 737 series airplanes, that requires 
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 amendment 
also requires eventual replacement of the existing bolts with new, 
improved bolts, which, when accomplished, terminates the repetitive 
inspection requirements of this AD. This amendment 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 
this 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: Effective March 29, 1999.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 29, 1999.

ADDRESSES: The service information referenced in this AD may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the

[[Page 8501]]

Federal Aviation Administration (FAA), Transport Airplane Directorate, 
Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the 
Office of the Federal Register, 800 North Capitol Street, NW., suite 
700, Washington, DC.

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: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to certain Boeing Model 737 series 
airplanes was published in the Federal Register on July 15, 1998 (63 FR 
38116). That action proposed to 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. That action also proposed to require 
eventual replacement of the existing bolts with new, improved bolts, 
which, when accomplished, would terminate the requirements of the AD.

Comments Received

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    Several commenters support the proposed rule.

Request to Revise Applicability of the AD

    One commenter requests that the applicability of the proposed AD be 
revised to list the affected airplanes by specific model number. The 
commenter states that the proposed applicability could cause undue 
confusion because the next generation (737-600/-700/-800) series 
airplanes will start over with line number 001, and the proposal does 
not apply to these next generation airplanes.
    The FAA concurs with the commenter's request. The FAA has verified 
that the cumulative line numbering of the next generation airplanes 
(737-600/-700/-800) will be reset to begin with line number 001. 
Additionally, the Model 737-400 and -500 series airplanes begin with 
line number 1486 and have a design change implemented that specifies 
installation of the Inconel bolts; therefore, those airplanes are not 
subject to the identified unsafe condition. The applicability section 
of the final rule has been revised to specify Model 737-100, -200 and -
300 series airplanes only, line numbers 1 through 1485.

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the change previously 
described. The FAA has determined that this change will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

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 will be affected by this AD.
    It will take approximately 3 work hours per airplane to accomplish 
the required inspection, at an average labor rate of $60 per work hour. 
Based on these figures, the cost impact of the inspection required by 
this AD on U.S. operators is estimated to be $113,400, or $180 per 
airplane, per inspection cycle.
    It will take approximately 9 work hours per airplane to accomplish 
the required replacement, at an average labor rate of $60 per work 
hour. Required parts will cost approximately $471 per airplane. Based 
on these figures, the cost impact of the replacement required 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 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 adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under 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. A final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from the Rules Docket at the location provided under the caption 
ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 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:

99-04-23  Boeing: Amendment 39-11048. Docket 98-NM-148-AD.
    Applicability: Model 737-100, -200, and -300 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

[[Page 8502]]

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.

    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.
    (e) Except as provided by paragraphs (b)(2) and (b)(3)(ii) of 
this AD, the actions shall be done 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. This incorporation by reference was approved by 
the Director of the Federal Register in accordance with 5 U.S.C. 
552(a) and 1 CFR part 51. Copies may be obtained from Boeing 
Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-
2207. Copies may be inspected at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the 
Office of the Federal Register, 800 North Capitol Street, NW., suite 
700, Washington, DC.
    (f) This amendment becomes effective on March 29, 1999.

    Issued in Renton, Washington, on February 11, 1999.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-3935 Filed 2-19-99; 8:45 am]
BILLING CODE 4910-13-U