[Federal Register Volume 63, Number 226 (Tuesday, November 24, 1998)]
[Proposed Rules]
[Pages 64915-64918]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-31326]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 98-NM-76-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747 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 747 series
airplanes, that currently requires a one-time inspection to detect
cracking and corrosion of various areas at all four nacelle struts; and
repair, if necessary. This action would require new repetitive
inspections to detect fatigue cracking or loose or missing fasteners of
the aft torque bulkheads of the outboard nacelle struts; and repair, if
necessary. In addition, this action would expand the applicability of
the existing AD to include additional airplanes. This proposal is
prompted by the availability of new service instructions for detecting
fatigue cracking that would not have been detected by the required
actions of the existing AD. The actions specified by the proposed AD
are intended to detect and correct such fatigue cracking
[[Page 64916]]
and loose or missing fasteners, which could result in failure of an
outboard nacelle strut, and consequent separation of the nacelle from
the wing.
DATES: Comments must be received by January 8, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 98-NM-76-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 98-NM-76-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. 98-NM-76-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
On December 31, 1996, the FAA issued AD 96-26-51, amendment 39-9876
(62 FR 1038, January 8, 1997), applicable to certain Boeing 747 series
airplanes, to require a one-time detailed visual inspection to detect
cracking and corrosion of various areas at all four nacelle struts; and
repair, if necessary. That action was prompted by reports of cracking
of the aft torque bulkhead at the inboard and outboard nacelle struts.
That action was applicable only to Model 747 series airplanes that were
equipped with Rolls-Royce-type engines. The requirements of that AD
were intended to detect and correct cracking of an inboard or outboard
nacelle strut, which could result in failure of the nacelle strut and
consequent separation of the nacelle from the wing.
Actions Since Issuance of Previous Rule
Since the issuance of that AD, the FAA has learned that the
original report of fatigue cracking on the inboard strut was made in
error. In fact, what was at first thought to be a fatigue crack on the
inboard strut was later determined to be merely a surface scratch in
the finish of the structure. Furthermore, the FAA has determined from
the service history of the Model 747 airplane that only the outboard
strut has proved to be susceptible to fatigue cracking of the aft
torque bulkhead. Investigation has revealed that this is because the
applied loading spectrum and design configuration of the outboard strut
are significantly different from those of the inboard strut.
In addition, since the issuance of AD 96-26-51, the FAA has
received an additional report of fatigue cracking found on another
Model 747 airplane, which also was equipped with Rolls-Royce-type
engines. The affected airplane had accumulated 18,663 total flight
cycles. That airplane was found to have cracking on both the inboard
and outboard vertical chords of the aft torque bulkhead on the number 4
nacelle strut. Specifically, two cracks of 0.53 inch and 0.34 inch in
length were found on the inboard vertical chord of the aft torque
bulkhead; and a single 0.12-inch crack was found on the outboard
vertical chord of the aft torque bulkhead.
In addition, whereas the strut design configurations and applied
loading spectra are significantly different for the inboard and
outboard struts, analysis shows that this is not the case for many of
the different engine types that can be installed on the outboard strut.
Therefore, outboard struts equipped with Rolls-Royce Model RB211,
General Electric Model CF6-45/50, or Pratt & Whitney Model JT9D-70
series engines also may be susceptible to fatigue cracking.
Also, the FAA has received reports of nine other nacelle struts
that were found to have loose fasteners at the attachment between the
vertical flange of the lower spar fitting and the aft torque bulkhead;
there have been no reports of missing fasteners at this location. The
cause of the fasteners becoming loose is not yet known.
These conditions (namely, fatigue cracking of the outboard nacelle
strut aft torque bulkhead web, vertical chords, and side skin; or loose
fasteners where the lower spar fitting attaches to the aft torque
bulkhead), if not corrected, could result in failure of an outboard
nacelle strut, and consequent separation of the nacelle from the wing.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletin
747-54A2184, dated July 3, 1997. The alert service bulletin describes
procedures for repetitive detailed visual inspections to detect fatigue
cracking of the web, vertical chords, and nacelle strut side skin of
the aft torque bulkheads of the number 1 and 4 nacelle struts; and
repair, if necessary. The repetitive inspections will also detect loose
or missing fasteners on the lower spar fitting of the aft torque
bulkhead. In addition, the alert service bulletin describes procedures
for various repetitive non-destructive test (NDT) inspections to detect
fatigue cracking of the aft torque bulkhead of the numbers 1 and 4
nacelle struts; and repair, if necessary. The NDT inspections consist
of ultrasonic inspections, surface eddy current inspections, and open-
hole eddy current inspections. The type of NDT inspection to be done
depends upon the type of nacelle strut on the affected airplane.
Accomplishment of the actions specified in the alert service bulletin
is intended to adequately address the identified unsafe condition.
[[Page 64917]]
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 all requirements of AD 96-26-51. This
proposed AD would require repetitive detailed visual inspections and,
for certain engine types, NDT inspections, to detect fatigue cracking
or loose or missing fasteners of the aft torque bulkheads of the
outboard nacelle struts; and repair, if necessary. This proposed AD
also would revise the applicability of the existing AD to include
additional airplanes having engine types in addition to those specified
in the existing AD.
This proposed AD also provides for an optional terminating action
for the repetitive inspections proposed for airplanes equipped with
General Electric CF6-45/50 or Pratt & Whitney JT9D-70 nacelle struts.
[This same terminating action, although optional for this proposed AD,
is required by another AD, namely, AD 95-13-07, amendment 39-9287 (60
FR 33336, June 28, 1995), as discussed below]. The FAA notes that there
is, as yet, no terminating action for those airplanes equipped with
Rolls-Royce RB-211 nacelle struts.
The actions above would be required to be accomplished in
accordance with the alert service bulletin described previously, except
as discussed below.
Differences Between Proposed Rule and Alert Service Bulletin
Operators should note that, although the alert service bulletin
provides for certain repair actions and specifies that the manufacturer
may be contacted for disposition of other repair conditions, this
proposal would require the repair of all 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.
In addition, operators should note that there is a typographical
error on Sheet 3 of Figure 1 of the alert service bulletin. The logic
block that contains a reference to ``Group 1 airplanes'' should have
read ``Groups 1 and 2 airplanes.''
Other Relevant Rulemaking
The FAA has previously issued AD 95-13-07, which requires
modification of airplanes equipped with General Electric CF6-45/50 or
Pratt & Whitney JT9D-70 nacelle struts. Accomplishment of the
modification required by that AD constitutes terminating action for the
requirements of this proposed AD. However, this proposed AD would not
affect the current requirements of AD 95-13-07.
Cost Impact
There are approximately 273 airplanes of the affected design in the
worldwide fleet. The FAA estimates that 24 airplanes of U.S. registry
would be affected by this proposed AD.
The new inspections that are proposed in this AD action for
airplane Groups 3 and 4 would take approximately 24 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 U.S. operators of airplanes in Groups 3 and 4 is estimated
to be $34,560, or $1,440 per airplane, per inspection cycle.
The cost impact figure discussed above is 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.
There currently are no affected airplanes on the U.S. Register
identified as Group 1 or 2 in the referenced alert service bulletin.
The airplanes included in Groups 1 and 2 of the applicability of this
rule currently are operated by non-U.S. operators under foreign
registry; therefore, they are not directly affected by this AD action.
However, the FAA considers that this rule is necessary to ensure that
the unsafe condition is addressed in the event that any of these
subject airplanes are imported and placed on the U.S. Register in the
future.
Should an affected Group 1 or 2 airplane be imported and placed on
the U.S. Register in the future, it would require approximately 78 work
hours to accomplish the new inspections proposed in this AD, at an
average labor rate of $60 per work hour. Based on these figures, the
cost impact of this proposed AD on airplane Groups 1 and 2 would be
$4,680 per airplane, per inspection cycle.
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 39-9876 (62 FR
1038, January 8, 1997), and by adding a new airworthiness directive
(AD), to read as follows:
Boeing: Docket 98-NM-76-AD. Supersedes AD 96-26-51, Amendment 39-
9876.
Applicability: Model 747 series airplanes, as listed in Boeing
Alert Service Bulletin 747-54A2184, dated July 3, 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 (e) 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.
[[Page 64918]]
To detect and correct fatigue cracking and loose or missing
fasteners of the aft torque bulkheads of the outboard nacelle
struts, which could result in failure of an outboard nacelle strut,
and consequent separation of the nacelle from the wing, accomplish
the following:
(a) For airplanes identified as Groups 1 and 2 airplanes in
Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997: Prior
to the accumulation of 12,000 total flight cycles, or within 90 days
after the effective date of this AD, whichever occurs later, perform
a detailed visual inspection of the aft torque bulkheads of the
number 1 and number 4 nacelle struts to detect fatigue cracking and
loose or missing fasteners. The inspection shall be accomplished in
accordance with Part I of the Accomplishment Instructions of Boeing
Alert Service Bulletin 747-54A2184, dated July 3, 1997.
Note 2: There is a typographical error on Sheet 3 of Figure 1 of
the alert service bulletin. The words ``Group 1 airplanes'' should
read ``Groups 1 and 2 airplanes.''
(1) If no cracking, and if no loose or missing fastener is
found, repeat the inspection thereafter at the intervals specified
in Figure 1 of the alert service bulletin.
(2) If any cracking, or if any loose or missing fastener is
found, prior to further flight, repair in accordance with Part III
of the alert service bulletin. Repeat the inspection thereafter at
the intervals specified in Figure 1 of the alert service bulletin.
Where the service bulletin specifies that the manufacturer may be
contacted for disposition of certain repair conditions, repair in
accordance with a method approved by the Manager, Seattle Aircraft
Certification Office (ACO), FAA, Transport Airplane Directorate; or
in accordance with data meeting the type certification basis of the
airplane approved by a Boeing Company designated engineering
representative (DER) who has been authorized by the Manager, Seattle
ACO, to make such findings.
(b) For airplanes identified as Groups 1 and 2 airplanes in
Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997: Prior
to the accumulation of 12,000 total flight cycles, or within 90 days
after the effective date of this AD, whichever occurs later, perform
a non-destructive test (NDT) inspection of the aft torque bulkheads
of the number 1 and number 4 nacelle struts to detect fatigue
cracking. The NDT inspection shall be accomplished in accordance
with Part II of the Accomplishment Instructions of Boeing Alert
Service Bulletin 747-54A2184, dated July 3, 1997.
Note 3: The alert service bulletin refers to a variety of NDT
inspections, consisting of ultrasonic inspections, surface eddy
current inspections, and open-hole eddy current inspections. The
logic diagram in Figure 1 of the alert service bulletin states the
conditions under which each of these inspections is to be performed.
(1) If no cracking is found, repeat the inspection thereafter at
the intervals specified in Figure 1 of the alert service bulletin.
(2) If any cracking is found, prior to further flight, repair in
accordance with Part III of the alert service bulletin. Repeat the
inspection thereafter at the intervals specified in Figure 1 of the
alert service bulletin. Where the service bulletin specifies that
the manufacturer may be contacted for disposition of certain repair
conditions, repair in accordance with a method approved by the
Manager, Seattle ACO; or in accordance with data meeting the type
certification basis of the airplane approved by a Boeing Company DER
who has been authorized by the Manager, Seattle ACO, to make such
findings.
(c) For airplanes identified as Groups 3 and 4 airplanes in
Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997: Prior
to the accumulation of 12,000 total flight cycles, or within 90 days
after the effective date of this AD, whichever occurs later, perform
a detailed visual inspection of the aft torque bulkheads of the
number 1 and number 4 nacelle struts to detect fatigue cracking and
loose or missing fasteners. The inspection shall be accomplished in
accordance with Part I of the Accomplishment Instructions of Boeing
Alert Service Bulletin 747-54A2184, dated July 3, 1997.
(1) If no cracking, and if no loose or missing fastener is
found, repeat the inspection thereafter at the intervals specified
in Figure 1 of the alert service bulletin, until the applicable
requirements of paragraph (d) are accomplished.
(2) If any cracking, or if any loose or missing fastener is
found, prior to further flight, repair in accordance with Part III
of the alert service bulletin. Where the alert service bulletin
specifies that the manufacturer may be contacted for disposition of
certain repair conditions, repair in accordance with a method
approved by the Manager, Seattle ACO; or in accordance with data
meeting the type certification basis of the airplane approved by a
Boeing Company DER who has been authorized by the Manager, Seattle
ACO, to make such findings.
(d) For airplanes identified as Groups 3 and 4 airplanes in
Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997:
Accomplishment of the nacelle strut modifications required in AD 95-
13-07, amendment 39-9287 (applicable to airplanes equipped with
either General Electric CF6-45/50 or Pratt & Whitney JT9D-70 nacelle
struts), constitutes terminating action for the requirements of this
AD.
(e) 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 4: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(f) 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 November 18, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 98-31326 Filed 11-23-98; 8:45 am]
BILLING CODE 4910-13-U
