[Federal Register Volume 63, Number 71 (Tuesday, April 14, 1998)]
[Proposed Rules]
[Pages 18167-18170]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-9752]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-82-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747-100 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing 
airworthiness directive (AD), applicable to certain Boeing Model 747-
100 series airplanes, that currently requires repetitive inspections to 
detect cracking of the wing front spar web above engine numbers 2 and 
3, and to detect cracked or broken fasteners in the web; and repair, if 
necessary. That AD also provides an optional terminating action for the 
repetitive inspections. This proposal would require various improved 
inspections. This proposal is prompted by a report indicating that the 
existing inspections do not adequately detect vertical cracks. The 
actions specified by the proposed AD are intended to prevent fuel 
leakage onto an engine and a resultant fire due to cracked or broken 
fasteners in the wing front spar.

DATES: Comments must be received by May 29, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 97-NM-82-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.

[[Page 18168]]

    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 97-NM-82-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. 97-NM-82-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On January 24, 1995, the FAA issued AD 95-02-15, amendment 39-9134 
(60 FR 9613, February 21, 1995), applicable to certain Boeing Model 
747-100 series airplanes, to require repetitive inspections to detect 
cracking of the wing front spar web above engine numbers 2 and 3, and 
to detect cracked or broken fasteners in the web; and repair, if 
necessary. That AD also provides for an optional terminating action for 
the repetitive inspections. That action was prompted by reports of 
broken fasteners and cracking of the web common to the upper and lower 
chords. The requirements of that AD are intended to prevent fuel 
leakage onto an engine and a resultant fire due to cracking or broken 
fasteners in the wing front spar.

Actions Since Issuance of Previous Rule

    Since the issuance of that AD, the FAA has reviewed and approved 
Revision 5 of Boeing Alert Service Bulletin 747-57A2266, dated August 
3, 1995. The revised alert service bulletin describes, among other 
things, the following various improved inspection procedures:
    1. Repetitive eddy current inspections to detect cracks along the 
web near the edges of the vertical flange of the upper and lower chords 
of the wing front spar between front spar station (FSS) 570 and FSS 
684. Certain inspection procedures specified in Revisions 3 and 4 of 
the alert service bulletin (which were referenced in AD 95-02-15 as the 
appropriate sources of service information for accomplishment of the 
inspections) do not adequately detect vertical cracks. Accomplishment 
of this new eddy current inspection will ensure that vertical cracks on 
the forward side of the web extending from behind the chord are 
detected.
    2. Repetitive ultrasonic inspections to detect cracks in the web 
around the first two fastener holes in the stiffeners and rib posts 
between FSS 570 and FSS 684. Accomplishment of this new inspection will 
ensure that vertical cracks of the web under the stiffeners that start 
from the fastener holes are detected.
    The remaining inspection procedures and follow-on actions specified 
in Revision 5 of the alert service bulletin are essentially identical 
to those described in Revisions 3 and 4.

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 supersede AD 95-02-15 to continue to require 
repetitive inspections to detect cracking of the wing front spar web 
above engine numbers 2 and 3, and to detect cracked or broken fasteners 
in the web; and repair, if necessary. The proposed AD also would 
continue to provide for an optional terminating action for the 
repetitive inspections. The proposed AD would require various improved 
inspections. The improved inspections would be required to be 
accomplished in accordance with Revision 5 of the alert service 
bulletin described previously.

Differences Between the Proposal and the Relevant Service 
Information

    Operators should note that, unlike the initial compliance time 
(specified in the alert service bulletin as within 15,000 total flight 
cycles or 6 months, whichever occurs later, for airplanes identified as 
Configuration A), the proposed AD would require that those airplanes be 
inspected prior to the accumulation of 13,000 total flight cycles or 
within 6 months. The 13,000 total flight cycle compliance threshold was 
established by AD 95-02-15, as a result of reports of cracking on 
affected airplanes that had accumulated between 13,700 and 22,000 total 
flight cycles. In light of these factors, the FAA finds that a 13,000 
total flight cycle compliance threshold for initiating the required 
actions is warranted, in that it represents an appropriate interval of 
time allowable for affected airplanes to continue to operate without 
compromising safety.

Cost Impact

    There are approximately 190 Boeing Model 747-100 series airplanes 
of the affected design in the worldwide fleet. The FAA estimates that 
95 airplanes of U.S. registry would be affected by this proposed AD.
    The actions that are currently required by AD 95-02-15, and 
retained in this proposed AD, take approximately 70 work hours per 
airplane to accomplish, at an average labor rate of $60 per work hour. 
Based on these figures, the cost impact of the currently required 
actions on U.S. operators is estimated to be $399,000, or $4,200 per 
airplane, per inspection cycle.
    For airplanes identified as Configuration A in the referenced alert 
service bulletin, the new actions that are proposed in this AD action 
would take approximately 60 work hours per airplane to accomplish, at 
an average labor rate of $60 per work hour. Based on these figures, the 
cost impact of the proposed requirements of this AD on those U.S. 
operators is estimated to be $3,600 per airplane, per inspection cycle.
    For airplanes identified as Configuration B in the referenced alert 
service bulletin, the new actions that are proposed in this AD action 
would take approximately 40 work hours per

[[Page 18169]]

airplane to accomplish, at an average labor rate of $60 per work hour. 
Based on these figures, the cost impact of these new action proposed by 
this AD on U.S. operators is estimated to be $2,400 per airplane, per 
inspection cycle.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the current or 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 (fastener replacement between FSS 570 and FSS 684) that is 
provided by this AD action, it would take approximately 306 work hours 
to accomplish it, at an average labor rate of $60 per work hour. The 
cost of required parts would be approximately $15,478. Based on these 
figures, the cost impact of the optional terminating action will be 
$33,838 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 removing amendment 39-9134 (60 FR 
9613, February 21, 1995), and by adding a new airworthiness directive 
(AD), to read as follows:

Boeing: Docket 97-NM-82-AD. Supersedes AD 95-02-15, Amendment 39-
9134.

    Applicability: Model 747-100 series airplanes; as listed in 
Boeing Alert Service Bulletin 747-57A2266, Revision 5, dated August 
3, 1995; 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 prevent fuel leakage onto an engine and a resultant fire, 
accomplish the following:

Restatement of Requirements of AD 95-02-15, Amendment 39-9134:

    (a) For airplanes on which the terminating action (fastener 
replacement) specified in Boeing Service Bulletin 747-57A2266, dated 
June 6, 1991; Revision 1, dated May 21, 1992; or Revision 2, dated 
June 10, 1993; has not been accomplished: Prior to the accumulation 
of 13,000 total flight cycles, or within 9 months after March 23, 
1995 (the effective date of AD 95-02-15, amendment 39-9134), or 
within 2,000 flight cycles after the immediately preceding 
inspection accomplished in accordance with AD 92-07-11, amendment 
39-8207, whichever occurs latest, accomplish the inspections 
specified in paragraphs (a)(1), (a)(2), and (a)(3) of this AD in 
accordance with Boeing Service Bulletin 747-57A2266, Revision 3, 
dated March 31, 1994, or Revision 4, dated November 3, 1994. Repeat 
these inspections thereafter at intervals not to exceed 2,000 flight 
cycles until the inspections required by paragraph (c) or (d) of 
this AD, as applicable, are accomplished.
    (1) Perform a detailed visual inspection to detect cracking of 
the wing front spar chords, stiffeners, and rib posts between the 
fastener heads between FSS 570 and FSS 684; and
    (2) Perform an ultrasonic inspection of the web under the upper 
and lower chord footprints to detect cracking of the wing front spar 
web between FSS 570 and FSS 684; and
    (3) Perform an ultrasonic inspection of the fasteners in the 
web-to-chords, and of the fasteners in the top two and bottom two 
rows in the web-to-stiffeners and web-to-rib posts of the wing front 
spar to detect cracked or broken fasteners between FSS 570 and FSS 
684.
    (b) For airplanes on which the terminating action (fastener 
replacement) specified in Boeing Service Bulletin 747-57A2266, dated 
June 6, 1991; Revision 1, dated May 21, 1992; or Revision 2, dated 
June 10, 1993; has been accomplished: Within 18 months after 
accomplishing the terminating action specified in the original 
issue, Revision 1, or Revision 2 of the service bulletin, or within 
9 months after March 23, 1995, whichever occurs later, accomplish 
the inspections specified in paragraphs (b)(1), (b)(2), and (b)(3) 
of this AD in accordance with Boeing Service Bulletin 747-57A2266, 
Revision 3, dated March 31, 1994, or Revision 4, dated November 3, 
1994. Repeat these inspections thereafter at intervals not to exceed 
2,000 flight cycles until the inspections required by paragraph (c) 
or (d) of this AD, as applicable, are accomplished.
    (1) Perform a detailed visual inspection of the wing front spar 
chords, stiffeners, and rib posts between the fastener heads between 
FSS 570 and FSS 684; and
    (2) Perform an ultrasonic inspection of the web under the upper 
and lower chord footprints to detect cracking of the wing front spar 
web between FSS 570 and FSS 636 and between FSS 675 and FSS 684; and
    (3) Perform an ultrasonic inspection of the fasteners in the 
web-to-chords, and of the fasteners in the top two rows and bottom 
two rows in the web-to-stiffeners and web-to-rib posts of the wing 
front spar to detect cracked or broken fasteners between FSS 570 and 
FSS 636 and between FSS 675 and 684.

New Requirements of This AD:

    (c) For airplanes identified as Configuration A in Boeing Alert 
Service Bulletin 747-57A2266, Revision 5, dated August 3, 1995: 
Prior to the accumulation of 13,000 total flight cycles, or within 6 
months after the effective date of this AD, or within 2,000 flight 
cycles after the immediately preceding inspection accomplished in 
accordance with paragraph (a) or (b) of this AD, whichever occurs 
latest, accomplish the inspections specified in paragraphs (c)(1), 
(c)(2), (c)(3), and (c)(4) of this AD, in accordance with Figure 3 
of Boeing Alert Service Bulletin 747-57A2266, Revision 5, dated 
August 3, 1995 specified . Repeat these inspections thereafter at 
intervals not to exceed 2,000 flight cycles. Accomplishment of these 
inspections terminates the inspections required by paragraphs (a) 
and (b) of this AD.
    (1) Perform a detailed visual inspection to detect damage and 
fuel leaks in the general area of the web of the wing front spar 
between FSS 570 and FSS 684.
    (2) Perform an eddy current inspection to detect cracks along 
the web near the edges of the vertical flange of the upper and lower 
chords of the wing front spar between FSS 570 and FSS 684.
    (3) Perform an ultrasonic inspection to detect cracks in the web 
around the first two

[[Page 18170]]

fastener holes in the stiffeners and rib posts between FSS 570 and 
FSS 684.
    (4) Perform an ultrasonic inspection to detect cracked or broken 
fasteners in the fasteners attaching only the web to the chords, in 
the top two and bottom two rows of the fasteners attaching the web 
to the stiffeners, and in the top two and bottom two rows of the 
fasteners attaching the web to the rib posts. This inspection area 
is located between FSS 570 and FSS 684.
    (d) For airplanes identified as Configuration B in Boeing Alert 
Service Bulletin 747-57A2266, Revision 5, dated August 3, 1995: 
Within 18 months following accomplishment of the terminating action 
(fastener replacement) specified in Boeing Service Bulletin 747-
57A2266, dated June 6, 1991, Revision 1, dated May 21, 1992, or 
Revision 2, dated June 10, 1993' or within 12 months after the 
effective date of this AD' or within 2,000 flight cycles after the 
immediately preceding inspection accomplished in accordance with 
paragraph (a) or (b) of this AD' whichever occurs latest; accomplish 
the inspections specified in paragraphs (d)(1), (d)(2), (d)(3), and 
(d)(4) of this AD in accordance with Figure 4 of Boeing Alert 
Service Bulletin 747-57A2266, Revision 5, dated August 3, 1995. 
Repeat these inspections thereafter at intervals not to exceed 2,000 
flight cycles. Accomplishment of these inspections terminates the 
inspections required by paragraphs (a) and (b) of this AD.
    (1) Perform a detailed visual inspection to detect damage and 
fuel leaks in the general area of the web of the wing front spar 
between FSS 570 and FSS 636 and between FSS 675 and FSS 684.
    (2) Perform an eddy current inspection to detect cracks along 
the web near the edges of the vertical flange of the upper and lower 
chords of the wing front spar between FSS 570 and FSS 636 and 
between FSS 675 and FSS 684.
    (3) Perform an ultrasonic inspection to detect cracks in the web 
around the first two fastener holes in the stiffeners and rib posts 
between FSS 570 and FSS 636 and between FSS 675 and FSS 684.
    (4) Perform an ultrasonic inspection to detect cracked or broken 
fasteners in the fasteners attaching only the web to the chords, in 
the top two and bottom two rows of the fasteners attaching the web 
to the stiffeners, and in the top two and bottom two rows of the 
fasteners attaching the web to the rib posts. This inspection area 
is located between FSS 570 and FSS 636 and between FSS 675 and FSS 
684.
    (e) If any discrepancy (i.e., cracking, fuel leakage, broken 
fasteners) is detected during any inspection required by this AD, 
prior to further flight, repair in accordance with paragraphs E. and 
H. (as applicable) of the Accomplishment Instructions of Boeing 
Service Bulletin 747-57A2266, Revision 3, dated March 31, 1994; 
Boeing Service Bulletin 747-57A2266, Revision 4, dated November 3, 
1994; or Boeing Alert Service Bulletin 747-57A2266, Revision 5, 
dated August 3, 1995. Thereafter, continue to inspect the remaining 
fasteners in accordance with paragraph (c) or (d) of this AD, as 
applicable, until the terminating action specified in paragraph (f) 
of this AD is accomplished. If any crack is found that cannot be 
removed by oversizing the fastener hole, prior to further flight, 
repair it in accordance with a method approved by the Manager, 
Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate.
    (f) Replacement of the fasteners in the web-to-chords and of the 
fasteners in the web-to-stiffeners and web-to-rib posts, as 
specified in Boeing Service Bulletin 747-57A2266, Revision 3, dated 
March 31, 1994; Revision 4, dated November 3, 1994, or Revision 5 
dated August 3, 1995; with oversized fasteners on each wing spar in 
accordance with the service bulletin constitutes terminating action 
for the repetitive inspections required by paragraphs (a), (b), (c), 
(d), and (e) of this AD.
    (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 Aircraft Certification 
Office (ACO), FAA, Transport Airplane Directorate. 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.

    (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.

    Issued in Renton, Washington, on April 7, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-9752 Filed 4-13-98; 8:45 am]
BILLING CODE 4910-13-U