[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]
BILLING CODE 4910-13-U
