AD 2001-16-06

[Federal Register Volume 66, Number 161 (Monday, August 20, 2001)]
[Rules and Regulations]
[Pages 43463-43465]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 01-20697]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-367-AD; Amendment 39-12374; AD 2001-16-06]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100 and -200 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 
initial and repetitive inspections of certain areas of the wing spars 
to detect cracking or corrosion; and follow-on corrective actions and 
repair, if necessary. This amendment is prompted by reports of cracks 
and corrosion in the upper chord of the front and rear spars of the 
wing and reports of cracks propagating from previously repaired areas. 
The actions specified by this AD are intended to detect and correct 
such cracking or corrosion of the upper and lower chords of the wing 
spars, which could result in reduced structural integrity of the wing.

DATES: Effective September 24, 2001.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of September 24, 2001.

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 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: James Blilie, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
227-2131; 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 737-100 and -
200 series airplanes was published in the Federal Register on May 1, 
2001 (66 FR 21700). That action proposed to require initial and 
repetitive inspections of certain areas of the wing spars to detect 
cracking or corrosion; and follow-on corrective actions and repair, if 
necessary.

Comments

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    The manufacturer recommends adding certain wording for 
clarification to the section of the Notice of Proposed Rulemaking 
(NPRM) which is entitled ``Explanation of Relevant Service 
Information.'' The FAA acknowledges that the suggested wording is more 
precise. However, since that wording does not reappear in the AD 
itself, no change is necessary.
    The manufacturer also suggests that the ``Applicability'' section 
be changed to read ``Model 737-100 and -200 series airplanes, line 
number 1 through 310 inclusive, and 323; certificated in any 
category.'' The effect of the suggested wording would be to clarify 
that the next generation of 737 models is specifically excluded. The 
FAA agrees

[[Page 43464]]

with the need for this clarification and has changed the AD 
accordingly.

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 168 Boeing Model 737 series airplanes of 
the affected design in the worldwide fleet. The FAA estimates that 45 
airplanes of U.S. registry will be affected by this AD.
    The FAA estimates that it will take approximately 30 work hours per 
airplane to do the initial detailed visual and eddy current 
inspections, and that the average labor rate is $60 per work hour. 
Based on these figures, the cost impact of the initial inspections on 
U.S. operators is estimated to be $81,000, or $1,800 per airplane.
    The FAA estimates that it will take approximately 30 work hours per 
airplane to do the repetitive inspections, and that the average labor 
rate is $60 per work hour. Based on these figures, the cost impact of 
the inspections on U.S. operators is estimated to be $81,000, or $1,800 
per airplane, per inspection cycle.
    The cost impact figure discussed above is 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. 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 adopted herein will 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. Therefore, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    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:

2001-16-06  Boeing: Amendment 39-12374. Docket 99-NM-367-AD.
    Applicability: Model 737-100 and -200 series airplanes, line 
number 1 through 310 inclusive, and 323; 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 (g) 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 detect and correct cracking or corrosion of the upper and 
lower chords of the front and rear spars of the wing, which could 
result in reduced structural integrity of the wing, accomplish the 
following:

Initial Detailed Visual and Eddy Current Inspections (Part I)

    (a) Within 12 months after the effective date of this AD: Do an 
initial detailed visual inspection to detect cracking or corrosion 
of the upper and lower chords of the front and rear spars, and an 
eddy current inspection to detect cracking of the vertical legs of 
the upper chords of the front and rear spars, per Part I of the 
Accomplishment Instructions of Boeing Service Bulletin 737-57-1067, 
Revision 4, dated November 7, 1991. Before further flight following 
the inspections, do the follow-on corrective actions required by 
paragraph (d) of this AD.

    Note 2: For the purposes of this AD, a detailed visual 
inspection is defined as: ``An intensive examination of a specific 
structural area, system, installation, or assembly to detect damage, 
failure, or irregularity. Available lighting is normally 
supplemented with a direct source of good lighting at an intensity 
deemed appropriate by the inspector. Inspection aids such as 
mirrors, magnifying lenses, etc. may be used. Surface cleaning and 
elaborate access procedures may be required.''

Repetitive Detailed Visual and Eddy Current Inspections (Part II)

    (b) Repeat the initial detailed visual inspection required by 
paragraph (a) of this AD at intervals not to exceed 12 months per 
Part II of the Accomplishment Instructions of Boeing Service 
Bulletin 737-57-1067, Revision 4, dated November 7, 1991. Before 
further flight following the inspection, do the follow-on corrective 
actions required by paragraph (d) of this AD.
    (c) Repeat the initial eddy current inspection required by 
paragraph (a) of this AD at intervals not to exceed 48 months per 
Part II of the Accomplishment Instructions of Boeing Service 
Bulletin 737-57-1067, Revision 4, dated November 7, 1991. Before 
further flight following the inspection, do the follow-on corrective 
actions required by paragraph (d) of this AD.

Follow-on Corrective Actions (Parts I, II, and III)

    (d) Do the follow-on corrective actions (including cleaning spar 
cavities, removing corrosion, and applying corrosion-inhibiting 
compound) required by paragraphs (d)(1), (d)(2), (d)(3), and (d)(4) 
of this AD, as applicable.
    (1) If no cracking or corrosion is found, apply a corrosion-
inhibiting compound to the accessible areas of the upper and lower 
chords of both the front and rear spars per Part I or Part II of the 
Accomplishment Instructions of Boeing Service Bulletin 737-57-1067, 
Revision 4, dated November 7, 1991, as applicable.
    (2) If any corrosion is found, repair per Part III of the 
Accomplishment Instructions of Boeing Service Bulletin 737-57-1067, 
Revision 4, dated November 7, 1991.
    (3) If a horizontal crack is found in the upper chords of the 
front or rear spars, repair per paragraph (f) of this AD.
    (4) If any cracking is found other than that identified in 
paragraph (d)(3) of this AD, repair per paragraph (d)(4)(i) or 
(d)(4)(ii) of this AD, as applicable.

[[Page 43465]]

    (i) If damage of the chords of the front or rear spar is within 
the limits specified in the service bulletin, before further flight, 
repair per Part III of the Accomplishment Instructions of Boeing 
Service Bulletin 737-57-1067, Revision 4, dated November 7, 1991.
    (ii) If damage of the chords of the front or rear spar exceeds 
the limits specified in the service bulletin, before further flight, 
repair per paragraph (f) of this AD.

Initial and Repetitive Eddy Current Inspections of Previous Repairs

    (e) For airplanes on which a previous repair to the upper chord 
of the front or rear spar was made per Boeing Service Bulletin 737-
57-1067, Revision 3, dated May 24, 1990, or earlier revisions: 
Within 12 months after the effective date of this AD, do an eddy 
current inspection of the repair area to detect cracking per a 
method approved by the Manager, Seattle Aircraft Certification 
Office (ACO), FAA. Repeat this inspection thereafter at intervals 
not to exceed 12 months. If any discrepancy is found, before further 
flight, repair per paragraph (f) of this AD. For a repair method to 
be approved by the Manager, SACO, as required by this paragraph, the 
approval letter must specifically reference this AD.

Repair

    (f) Repair (including removing corrosion; inspecting the rework 
area for cracks; refinishing the blend-out area; installing a 
nesting angle repair; and applying chemical film treatment, primer, 
sealant, and corrosion-inhibiting compound) any discrepancy 
specified in paragraphs (d)(3), (d)(4)(ii), and (e) of this AD, per 
a method approved by the Manager, Seattle ACO; or per data meeting 
the type certification basis of the airplane approved by a Boeing 
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

    (g) 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, FAA. 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

    (h) 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.

Incorporation by Reference

    (i) Except as provided by paragraphs (e) and (f) of this Ad, the 
actions shall be done in accordance with Boeing Service Bulletin 
737-57-1067, Revision 4, dated November 7, 1991. 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.

Effective Date

    (j) This amendment becomes effective on September 24, 2001.

    Issued in Renton, Washington, on August 9, 2001.
Vi L. Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-20697 Filed 8-17-01; 8:45 am]
BILLING CODE 4910-13-P