[Federal Register Volume 63, Number 102 (Thursday, May 28, 1998)]
[Proposed Rules]
[Pages 29151-29153]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-14028]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-100-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747-100, 747-200, and 747-
SP Series Airplanes and Military Type E-4B 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, -
200, and 747-SP series airplanes and military type E-4B airplanes. This 
proposal would require repetitive inspections to detect cracking of the 
wing front spar web, and repair of cracked structure. This proposal 
also provides for optional terminating action for the repetitive 
inspection requirements. This proposal is prompted by reports 
indicating that fatigue cracks were found on the aft surface of the 
wing front spar web. The actions specified by the proposed AD are 
intended to detect and correct such fatigue cracking, which could 
result in a fuel leak, and consequent increased risk of a fire.

DATES: Comments must be received by July 13, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 97-NM-100-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

[[Page 29152]]

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-100-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-100-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports indicating that operators have found 
numerous fatigue cracks on the aft surface of the front spar web on 
Boeing Model 747 series airplanes. The cracks were found inside the 
wing fuel tank at Front Spar Station Inboard (FSSI) 688 where the 
inboard nacelle rib post and the 670 rib post attach to the web of the 
front spar. All of the cracks were found between these two rib posts 
inside the wing fuel tank. Metallurgical analyses indicate that the 
cracks were initiated by fatigue on the aft surface of the front spar 
web. The analyses also indicate that the various fatigue cracks 
initiated on the web itself, and not at the edges of the adjacent 
fastener holes. Such fatigue cracking, if not detected and corrected, 
could result in a fuel leak and consequent increased risk of a fire.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 747-
57A2303, Revision 1, dated September 25, 1997, which describes 
procedures for repetitive ultrasonic inspections to detect cracking of 
the wing front spar web at the fastener rows behind and between the 
upper link fittings for the number 2 and 3 engine struts; and repair, 
if necessary. The service bulletin also describes procedures for an 
optional terminating modification, which, if accomplished, would 
eliminate the need for the repetitive inspections. The optional 
terminating modification involves replacing the cracked spar web with a 
shot-peened spar web. Accomplishment of the actions specified in the 
service bulletin 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 bulletin described previously, except as discussed below.

Differences Between Proposed Rule and Service Bulletin

    Operators should note that, although the service bulletin specifies 
that the 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.

Optional Terminating Modification

    This proposed AD also would provide for an optional terminating 
modification of the wing front spar web . The FAA has determined that 
the repetitive inspections proposed by this AD can be 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 
before it represents a hazard to the airplane.

Cost Impact

    There are approximately 190 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, that it would take approximately 
64 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 $364,800, or $3,840 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 
modification, it would take approximately 518 work hours per airplane 
to accomplish the modification, at an average labor rate of $60 per 
work hour. Required parts would cost approximately $17,000 per 
airplane. Based on these figures, the cost impact of the optional 
terminating modification proposed by this AD is estimated to be $48,080 
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

[[Page 29153]]

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 97-NM-100-AD.

    Applicability: Model 747-100, 747-200, and 747-SP series 
airplanes and military type E-4B airplanes; as listed in Boeing 
Service Bulletin 747-57A2303, Revision 1, dated September 25, 1997; 
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 wing front spar 
web, which could result in a fuel leak, and consequent increased 
risk of a fire, accomplish the following:
    (a) Perform an ultrasonic inspection to detect cracking of the wing 
front spar web at the fastener rows behind and between the upper link 
fittings for the number 2 and 3 engine struts, in accordance with the 
Accomplishment Instructions of Boeing Service Bulletin 747-57A2303, 
Revision 1, dated September 25, 1997, at the time specified in 
paragraph (a)(1) or (a)(2) of this AD, as applicable.
    (1) For airplanes identified as Group 1, 2, 3, or 5 in the alert 
service bulletin: Inspect prior to the accumulation of 12,500 total 
flight cycles, or within 15 months after the effective date of this AD, 
whichever occurs later. Repeat the inspection thereafter at intervals 
not to exceed 2,200 flight cycles.
    (2) For airplanes identified as Group 4, 6, 7, 8, 9, or 10 in the 
alert service bulletin: Inspect prior to the accumulation of 18,000 
total flight cycles, or within 15 months after the effective date of 
this AD, whichever occurs later. Repeat the inspection thereafter at 
intervals not to exceed 3,000 flight cycles.
    (b) If any crack is found during any inspection required by 
paragraph (a) of this AD, prior to further flight, accomplish either 
paragraph (b)(1) or (b)(2) of this AD.
    (1) Accomplish the terminating action in accordance with the 
Accomplishment Instructions of Boeing Service Bulletin 747-57A2303, 
Revision 1, dated September 25, 1997. Accomplishment of this action 
constitutes terminating action for the repetitive inspection 
requirements of this AD; or
    (2) Repair in accordance with a method approved by the Manager, 
Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate.
    (c) Replacement of the affected wing front spar web with a new 
shot-peened wing front spar web in accordance with the Accomplishment 
Instructions of Boeing Service Bulletin 747-57A2303, Revision 1, dated 
September 25, 1997, constitutes terminating action for the repetitive 
inspection requirements of this AD.

    (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.

    (e) 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 May 20, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-14028 Filed 5-27-98; 8:45 am]
BILLING CODE 4910-13-U