Airworthiness Directives; Boeing Model 747-100 and -200 Series Airplanes

[Federal Register Volume 64, Number 161 (Friday, August 20, 1999)]
[Proposed Rules]
[Pages 45481-45483]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-21686]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-88-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747-100 and -200 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 747-100 and -
200 series airplanes. This proposal would require repetitive 
inspections of the upper and lower chords of the wing front spar for 
cracks, and corrective action, if necessary. For airplanes on which no 
cracking is detected, this proposal would also provide optional 
terminating action in lieu of repetitive inspections. This proposal is 
prompted by reports of cracks in the upper chord of the wing front 
spar. The actions specified by the proposed AD are intended to detect 
and correct fatigue cracking of the upper and lower chords of the wing 
front spar, which could result in reduced structural capability and 
possible fuel leakage onto an engine and a resultant fire.

DATES: Comments must be received by October 4, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-88-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: Tamara L. Anderson, Aerospace 
Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane 
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, 
SW., Renton, Washington 98055-4056; telephone (425) 227-2771; 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 99-NM-88-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. 99-NM-88-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports of cracks in the upper chord of the 
wing front spar at the fastener holes in the area of the number 2 and 
number 3 strut outboard upper link fitting. The cracks are believed to 
initiate by fatigue on the forward surface of the chord and propagate 
into the thickness of the part. The lower chord of the wing front spar 
is similar in design to the upper chord; therefore, the lower chord may 
be subject to the same unsafe condition. This condition, if not 
corrected, could result in reduced structural capability and possible 
fuel leakage onto an engine and resultant fire.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 747-57-
2305, Revision 1, dated January 21, 1999, which describes procedures 
for repetitive ultrasonic inspections of the upper and lower chords of 
the wing front spar for cracks, and corrective action, if necessary. 
The corrective action involves accomplishment of a terminating action 
that includes a high frequency eddy current inspection of the upper and 
lower chords of the spar, repair of cracks, and installation of 
oversized fasteners. For airplanes on which cracking is not detected, 
accomplishment of the terminating action is optional, and eliminates 
the need for the repetitive inspections.

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. 
This proposed AD also would provide optional terminating action for the 
repetitive inspections for airplanes on which no cracking is detected.
    Operators should note that the FAA has determined that the 
repetitive inspections proposed by this AD can be

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allowed to continue in lieu of accomplishment of a terminating action. 
In making this determination, the FAA considers that, in this case, 
long-term continued operational safety will be adequately assured by 
accomplishing the repetitive inspections to detect fatigue cracking of 
the upper and lower chords of the wing front spar before it represents 
a hazard to the airplane.

Differences Between the Proposed Rule and Service Bulletin

    Boeing Service Bulletin 747-57-2305, Revision 1, specifies 
accomplishment of the actions that would be required by paragraphs (a) 
and (b) of this AD in accordance with either the Boeing-specified 
manuals or ``operator's equivalent procedure.'' However, this proposed 
AD would require that the ultrasonic inspection and high frequency eddy 
current inspection actions required by those paragraphs be accomplished 
in accordance with the procedures specified in the Boeing 747 NDT 
Manual D6-7170. ``Operator's equivalent procedures'' may be used for 
Boeing-specified manuals with the exception of the Boeing 747 NDT 
Manual D6-7170. ``Operator's equivalent procedures'' to the Boeing 747 
NDT Manual D6-7170 may be used only if approved as an alternative 
method of compliance in accordance with paragraph (c) of this AD.
    Operators should note that, although the service bulletin specifies 
that the manufacturer may be contacted for disposition of certain 
repair conditions, this proposed AD would require the repair of those 
conditions to be accomplished in accordance with a method approved by 
the FAA, or in accordance with 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. For a repair method to be approved by the Manager, 
Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate, as specified by paragraph (a)(3) of this proposed AD, the 
Manager's approval letter must specifically reference this AD.

Cost Impact

    There are approximately 332 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 137 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 inspection, 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 $16,440, or $120 per airplane, per inspection cycle.
    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 AD were not adopted.
    Should an operator elect to accomplish the optional terminating 
action rather than continue the repetitive inspections, it would take 
approximately 37 work hours per airplane to accomplish the 
modification, at an average labor rate of $60 per work hour. Required 
parts would cost approximately $5,000 per airplane. Based on these 
figures, the cost impact of this optional terminating action is 
estimated to be $7,220 per airplane.

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 99-NM-88-AD.

    Applicability: Model 747-100 and -200 series airplanes, listed 
in Boeing Service Bulletin 747-57-2305, Revision 1, dated January 
21, 1999, 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 detect and correct fatigue cracking of the upper and lower 
chords of the wing front spar, which could result in reduced 
structural capability and possible fuel leakage onto an engine and a 
resultant fire, accomplish the following:

Inspections and Corrective Action

    (a) Prior to the accumulation of 12,000 total flight cycles, or 
within 24 months after the effective date of this AD, whichever 
occurs later, accomplish an ultrasonic inspection for cracking of 
the upper and lower chord of the wing front spar, in accordance with 
Boeing Service Bulletin 747-57-2305, Revision 1, dated January 21, 
1999.
    (1) If no cracking is found, repeat this inspection thereafter 
at intervals not to exceed 6,000 flight cycles, until the 
requirements of paragraph (c) of this AD have been accomplished.
    (2) If any cracking is found, prior to further flight, 
accomplish ``Part 2--Terminating Action'' of the Accomplishment 
Instructions of the service bulletin, except as provided by 
paragraph (b) of this AD. Accomplishment of this action constitutes 
terminating action for the requirements of this AD.
    (b) During accomplishment of the terminating action required by 
paragraph (a)(2) of this AD, if any crack is found in the upper 
chord that is outside the limits specified in Boeing Service 
Bulletin 747-57-2305, Revision 1, dated January 21, 1999; or if any 
crack is found in the lower chord; prior to further flight, repair 
in accordance with a method approved by the Manager, Seattle 
Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate; or in

[[Page 45483]]

accordance with 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. For a repair method to be approved by the Manager, Seattle 
ACO, as required by this AD, the Manager's approval letter must 
specifically reference this AD.

Optional Terminating Action

    (c) Accomplishment of ``Part 2--Terminating Action'' of the 
Accomplishment Instructions of Boeing Service Bulletin 747-57-2305, 
Revision 1, dated January 21, 1999, constitutes terminating action 
for the requirements of 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 2: 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 
Secs. 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 August 16, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-21686 Filed 8-19-99; 8:45 am]
BILLING CODE 4910-13-P