[Federal Register Volume 59, Number 208 (Friday, October 28, 1994)]
[Unknown Section]
[Page ]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-26716]


[Federal Register: October 28, 1994]


                                                   VOL. 59, NO. 208

                                           Friday, October 28, 1994

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-120-AD]


Airworthiness Directives; Boeing Model 747SP 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 747SP 
series airplanes, that currently requires repetitive inspections for 
cracks in the web of the wing front spar over engine numbers 2 and 3, 
and repair, if necessary. This action would require additional 
inspections in an area beyond that specified in the existing AD. This 
action also would provide for a new, optional terminating modification, 
which, if accomplished, would constitute terminating action for the 
repetitive inspections. This proposal is prompted by a report of 
cracking in the web in an area outside the inspection zone specified in 
the existing AD. A crack in the web that is not detected before it 
extends outside the chord footprints can allow fuel leakage. The 
actions specified by the proposed AD are intended to prevent fuel 
leakage onto an engine and a resultant fire due to cracking in the web 
of the wing front spar.

DATES: Comments must be received by December 24, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 94-NM-120-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: Tim Backman, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2776; fax (206) 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 94-NM-120-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-103, Attention: Rules 
Docket No.94-NM-120-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On August 6, 1990, the FAA issued AD 90-17-18, amendment 39-6702(55 
FR 33279, August 15, 1990), applicable to certain Boeing Model 747SP 
series airplanes, to require inspections for cracks in the web of the 
wing front spar between front spar station (FSS) 636 and FSS 675 over 
engine numbers 2 and 3, and repair, if necessary. That AD also provides 
for an optional modification, which, if accomplished, constitutes 
terminating action for the required inspections. That action was 
prompted by a report of a 26-inch crack on the front spar web. The 
requirements of that AD are intended to prevent fuel leakage onto an 
engine and a resultant fire.
    Since the issuance of that AD, the FAA received a report of 
cracking in the web of the wing front spar in an area outside the 
inspection zone specified in AD 90-17-18 on a Model 747SP series 
airplane that had been inspected previously in accordance with that AD. 
The report involved a 31-inch fatigue crack between front spar station 
(FSS) 628 and FSS 659. The crack was initiated by sonic fatigue. In 
addition, fuel was leaking adjacent to the number 3 engine. The FAA 
also received a report of a 24-inch fatigue crack between FSS 646 and 
FSS 670 on another Model 747SP series airplane. A crack in the web that 
is not detected before it extends outside the chord footprints can 
allow fuel leakage. Fatigue cracking on the web of the wing front spar, 
if not detected and corrected in a timely manner, can result in fuel 
leakage onto an engine and a resultant fire.
    Based on these findings, the FAA has determined that additional 
actions are necessary on airplanes that were inspected or modified in 
accordance with AD 90-17-18. The FAA finds that an ultrasonic 
inspection must be performed in an area that extends beyond that 
specified in the existing AD. In addition, a high frequency eddy 
current inspection of an area of the web one inch below the upper chord 
and one inch above the lower chord footprints between FSS 628 and FSS 
675 must be performed. Additionally, the FAA finds that these 
inspections must be performed on airplanes on which the ``terminating 
modification,'' which was provided in AD 90-17-18, was previously 
installed.
    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-57A2259, Revision 2, dated June 9, 1994, which describes procedures 
for additional inspections of an expanded inspection zone. This revised 
alert service bulletin describes the following repetitive inspections 
to detect cracks in the web between FSS 628 and FSS 675:
    1. Ultrasonic inspections of the web under the upper and lower 
chord footprints;
    2. High frequency eddy current inspections of the web in an area 
one inch below the upper chord and one inch above the lower chord 
footprints; and
    3. Detailed visual inspections of the forward face of the web of 
the wing front spar at fastener locations in the web-to-stiffeners and 
web-to-rib posts.
    The alert service bulletin also describes procedures for 
accomplishment of an optional terminating modification. That 
modification involves removing a section of the web of the wing front 
spar between FSS 623 and FSS 670 inboard of the inboard engine, 
splicing in a new thicker web section, and adding a new stiffener 
outboard of the web splice. If this modification is accomplished, the 
repetitive inspections of the web, as described in the alert service 
bulletin, are no longer necessary.
    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 90-17-18 to require various repetitive 
inspections to detect cracks in the web of the wing front spar in an 
area beyond that specified in the existing AD, and modification, if 
cracking is found. Installation of the modification would constitute 
terminating action for the repetitive inspections. The actions would be 
required to be accomplished in accordance with the alert service 
bulletin described previously.
    Operators should note that this NPRM would supersede the existing 
AD with new, additional inspections and a new terminating modification. 
Airplanes on which the previous ``terminating'' modification provided 
for in AD 90-17-18 had been installed would be required to be inspected 
in accordance with the new inspections proposed in this notice. 
Installation of the new terminating modification, specified in 
paragraph (e) of this notice, would constitute terminating action for 
the requirements of the AD.
    The manufacturer has advised that it is currently developing a 
modification program for the engine struts on these airplanes that will 
positively address the fatigue cracking condition and other items 
associated with the engine struts. Once this modification program is 
developed and approved, the FAA may consider additional rulemaking.
    There are approximately 35 Model 747SP series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 11 
airplanes of U.S. registry would be affected by this proposed AD.
    The FAA estimates that it would take approximately 22 work hours 
per airplane to accomplish the proposed inspections (between FSS 628 
and FSS 675) specified in this AD, and that the average labor rate is 
$55 per work hour. Based on these figures, the total cost impact of the 
proposed AD on U.S. operators is estimated to be $13,310, or $1,210 per 
airplane.
    The total 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 terminating modification 
that would be provided by this AD action, it would take approximately 
644 work hours to accomplish it, at an average labor rate of $55 per 
work hour. The cost of required parts would be $21,800. Based on these 
figures, the total cost impact of the terminating modification would be 
$57,220 per airplane.
    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. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing amendment 39-6702 (55 FR 
33279, August 15, 1990), and by adding a new airworthiness directive 
(AD), to read as follows:

Boeing: Docket 94-NM-120-AD. Supersedes AD 90-17-18, Amendment 39-
6702.

    Applicability: Model 747SP series airplanes; variable numbers 
RG001 through RG142 inclusive, and RG171 through RG222 inclusive; 
certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent fuel leakage onto an engine and a resultant fire, 
accomplish the following:
    (a) For airplanes on which the ``terminating modification'' 
[between front spar station (FSS) 640 and FSS 670] specified in 
Boeing Alert Service Bulletin 747-57A2259, dated February 15, 1990; 
or Revision 1, dated September 6, 1990; has not been accomplished: 
Within the next six months after September 21, 1990 (the effective 
date of AD 90-17-18, amendment 39-6702), perform a visual and an 
ultrasonic inspection of the front spar web between front spar 
station (FSS) 636 and FSS 675 in accordance with Boeing Alert 
Service Bulletin 747-57A2259, dated February 15, 1990, or Revision 
1, dated September 6, 1990. If no crack is found, repeat these 
inspections at intervals not to exceed 1,000 landings until the 
inspections required by paragraph (b) of this AD are accomplished.
    (b) For airplanes on which the ``terminating modification'' 
[between front spar station (FSS) 640 and FSS 670] specified in 
Boeing Alert Service Bulletin 747-57A2259, dated February 15, 1990; 
or Revision 1, dated September 6, 1990; has not been accomplished: 
Prior to the accumulation of 4,000 total landings on the airplane, 
or within 1,000 landings after the effective date of this AD, 
whichever occurs later, perform the inspections specified in 
paragraphs (b)(1), (b)(2), and (b)(3) of this AD to detect cracks in 
the web between FSS 628 and FSS 675, in accordance with Boeing Alert 
Service Bulletin 747-57A2259, Revision 2, dated June 9, 1994. 
Accomplishment of these inspections terminates the repetitive 
inspection requirement of paragraph (a) of this AD. If no crack is 
found, repeat these inspections thereafter at intervals not to 
exceed 1,000 landings.
    (1) Perform an ultrasonic inspection in the web under the upper 
and lower chord footprints; and
    (2) Perform a high frequency eddy current inspection in the web 
in an area one inch below the upper chord and one inch above the 
lower chord footprints; and
    (3) Perform a detailed visual inspection in the forward face of 
the web of the wing front spar at fastener locations in the web-to-
stiffeners and web-to-rib posts.
    (c) For airplanes on which the ``terminating modification'' 
specified in Boeing Alert Service Bulletin 747-57A2259, dated 
February 15, 1990; or Revision 1, dated September 6, 1990; has been 
accomplished: Prior to the accumulation of 4,000 total landings on 
the airplane, or within 6 months after the effective date of this 
AD, whichever occurs later, perform the inspections specified in 
paragraphs (c)(1), (c)(2), and (c)(3) of this AD to detect cracks in 
the web between FSS 628 and FSS 636, in accordance with Boeing Alert 
Service Bulletin 747-57A2259, Revision 2, dated June 9, 1994. If no 
crack is found, repeat these inspections thereafter at intervals not 
to exceed 1,000 landings.
    (1) Perform an ultrasonic inspection of the web under the upper 
and lower chord footprints; and
    (2) Perform a high frequency eddy current inspection of the web 
in an area one inch below the upper chord and one inch above the 
lower chord footprints; and
    (3) Perform a detailed visual inspection of the forward face of 
the web of the wing front spar at fastener locations in the web-to-
stiffeners and web-to-rib posts.
    (d) If any crack is found during any inspection required by this 
AD, prior to further flight, accomplish a terminating modification 
(between FSS 623 and FSS 670) in accordance with Boeing Alert 
Service Bulletin 747-57A2259, Revision 2, dated June 9, 1994; or in 
accordance with a method approved by the Manager, Seattle Aircraft 
Certification Office (ACO), FAA, Transport Airplane Directorate.
    (e) Installation of a terminating modification (between FSS 623 
and FSS 670) in accordance with Boeing Alert Service Bulletin 747-
57A2259, Revision 2, dated June 9, 1994; or in accordance with a 
method approved by the Manager, Seattle ACO; constitutes terminating 
action for the requirements of this AD.
    (f) 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: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (g) 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 October 24, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-26716 Filed 10-27-94; 8:45 am]
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