[Federal Register Volume 63, Number 226 (Tuesday, November 24, 1998)]
[Proposed Rules]
[Pages 64913-64915]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-31327]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 98-NM-144-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 adoption of a new airworthiness
directive (AD) that is applicable to certain Boeing Model 747 series
airplanes. This proposal would require repetitive inspections of the
outboard nacelle struts to detect fatigue cracking of the strut skin
and spring beam support fittings, and to detect cracked or loose
fasteners of the support fittings; and corrective actions, if
necessary. This proposal also provides for optional terminating action
for the repetitive inspection requirements. This proposal is prompted
by reports indicating that several cracked or broken spring beam
support fittings were found on the outboard nacelle struts. The actions
specified by the proposed AD are intended to detect and correct such
fatigue cracking and loose fasteners, which could result in failure of
the outboard nacelle struts and consequent separation of the engine.
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-144-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, 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-144-AD.'' The postcard will be date stamped and
returned to the commenter.
Availability of NPRM's
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-144-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
The FAA has received reports from three operators indicating
findings of six cracked or broken spring beam support fittings on the
outboard struts of Model 747 series airplanes. Four of the cracked or
broken support fittings were found on strut number 1 (left outboard
strut), and two others were found on strut number 4 (right outboard
strut).
An operator of a Model 747-200 combi airplane that had accumulated
76,372 total flight hours and 14,501 total flight cycles reported
finding a 5-inch crack in the inboard skin panel during a preflight
check on the number 1 strut, and further investigation revealed a
fractured support fitting on the inboard side of that strut. An
operator of a Model 747-200F airplane equipped with General Electric
CF6-50 series engines, which had accumulated 71,609 total flight hours
and 14,808 total flight cycles, reported findings of a severed support
fitting on the number 1 strut.
Another operator of a Model 747-200F airplane equipped with Pratt &
Whitney JT9D-70 series engines reported findings of two broken support
fittings, one on the number 1 strut and one on the number 4 strut. A
report indicated that, during a heavy maintenance preliminary check, a
misaligned stripe on the outboard nacelle strut was found. Further
investigation revealed a broken spring beam on the outboard side of the
number 4 strut and a broken support fitting. This airplane had
accumulated 72,426 total flight hours and 18,142 total flight cycles.
An inspection of the remaining fleet of similar airplanes revealed
findings of two fractured support fittings on an airplane that had
accumulated 66,035 total flight hours and 16,709 total flight cycles.
All of these operators reported findings of cracked or severed
spring beam support fittings located on the inboard side of the strut
and attached to the strut skin. These conditions, if not corrected,
could cause fatigue cracking of the strut skin and spring beam support
fittings on the outboard nacelle struts, which could result in failure
of the outboard nacelle struts and consequent separation of the engine.
Other Relevant Rulemaking
The FAA has previously issued AD 95-13-07, amendment 39-9287 (60 FR
33336, June 28, 1995), which currently requires modification of the
nacelle strut and wing structure, inspections and checks to detect
discrepancies, and correction of discrepancies. The corrective action
specified by that AD included a modification to improve the damage
tolerance capability and durability of the strut-to-wing attachments,
reduce reliance on non-routine inspections of those attachments, and
prevent failure of the strut and consequent separation of the engine.
Although the accomplishment of the modification required by that AD
constitutes terminating action for the requirements of that AD, this
proposed AD specifies that same modification as an optional terminating
action.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletin
747-
[[Page 64914]]
54A2172, dated February 23, 1995, and Boeing Service Bulletin 747-
54A2172, Revision 1, dated January 4, 1996, which describe similar
procedures for detecting cracks of the strut skin and spring beam
support fittings, or detecting cracked or loose fasteners of the
support fittings; and corrective actions, if necessary.
The initial inspections differ from the repetitive inspections. The
initial inspections include a visual inspection of the four spring beam
support fittings, a detailed visual inspection of the support fitting
at the fasteners using a borescope, a visual inspection of the
fasteners, and a detailed visual inspection of the strut skin. The
repetitive inspections include an inspection of the support fitting at
fasteners through the horizontal flange, an inspection of the fasteners
through the vertical flange for loose collars, an external visual
inspection for loose fastener heads, and a detailed visual inspection
of the strut skin.
The terminating action in both service bulletins specifies an open-
hole high frequency eddy current (HFEC) inspection and, if no cracks
are found, rework of the fastener holes and installation of new
fasteners. For airplanes on which any cracks are found during the HFEC
inspection, Part III of the Accomplishment Instructions of the Boeing
alert service bulletin specifies contacting the manufacturer for repair
instructions. However, for those same airplanes, Revision 1 of the
Boeing service bulletin adds a new section to the Accomplishment
Instructions (``Part IV. Replacement''), which specifies procedures for
replacing any cracked spring beam support fitting with a new support
fitting. Accomplishment of this replacement action would eliminate the
need for the repetitive inspections of that new support fitting.
Explanation of Requirements of Proposed Rule
Since an unsafe condition has been identified that is likely to
exist or develop on other Boeing Model 747 series airplanes of this
same type design, the proposed AD would require accomplishment of the
actions specified by the service bulletins described previously, except
as discussed below. The proposed AD also provides for several optional
terminating actions. If no cracks are found, rework of the fastener
holes and installation of new fasteners would constitute terminating
action for the repetitive inspection requirements of this AD. If cracks
are found during an open-hole HFEC inspection, replacement of the
spring beam support fittings with new fittings constitutes optional
terminating action for the repetitive inspection requirements of this
AD.
Differences Between Proposed Rule and Service Information
Operators should note the following differences between the
proposed rule and the service information:
Boeing Alert Service Bulletin 747-54A2172, dated February 23, 1995,
and Boeing Service Bulletin 747-54A2172, Revision 1, dated January 4,
1996, provide procedures for terminating actions for the repetitive
inspections. However, this proposed AD specifies those actions as
optional terminating actions since the FAA has previously issued AD 95-
13-07, which requires a terminating modification that is considered
acceptable for compliance with the optional terminating action
specified by this AD.
Although the Boeing alert service bulletin specifies that the
manufacturer may be contacted for the disposition of certain repair
conditions, this proposal would require that the repair of those
conditions be accomplished in accordance with a method approved by the
FAA.
Cost Impact
There are approximately 145 airplanes of the affected design in the
worldwide fleet. The FAA estimates that 9 airplanes of U.S. registry
would be affected by this proposed AD, that it would take approximately
16 work hours per airplane to accomplish the proposed inspection, and
that the average labor rate is $60 per work hour. Based on these
figures, the cost impact of the proposed AD on U.S. operators is
estimated to be $8,640, or $960 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 fastener hole inspection
and modification, it would take approximately 20 work hours (excluding
removal of the strut and spring beam) to accomplish it, at an average
labor rate of $60 per hour. Based on these figures, the cost impact of
this optional terminating action is estimated to be $1,200 per strut.
Should an operator elect to accomplish the replacement of the
spring beam support fittings with new support fittings, it would take
approximately 108 work hours (excluding removal of the strut and spring
beam) to accomplish it, at an average labor rate of $60 per hour. Based
on these figures, the cost impact of this optional terminating action
is estimated to be $6,480 per support fitting.
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 adding the following new
airworthiness directive:
BOEING: Docket 98-NM-144-AD.
Applicability: Model 747 series airplanes, line numbers 202
through 886 inclusive, equipped with General Electric Model CF6-45/
50 and Pratt & Whitney Model JT9D-70 series engines; on which the
strut/wing modification has not been accomplished in accordance with
AD 95-13-07, amendment 39-9287; certificated in any category.
[[Page 64915]]
Note 1: This AD applies to each airplane identified in the
preceding applicability provision, regardless of whether it has been
otherwise 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 (h) 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 strut skin and
spring beam support fittings on the outboard nacelle struts, and
cracked or loose fasteners of the support fittings, which could
result in failure of the outboard nacelle struts and consequent
separation of the engine, accomplish the following:
(a) Prior to the accumulation of 13,000 total flight cycles, or
within 6 months after the effective date of this AD, whichever
occurs later, perform a detailed visual inspection of the outboard
nacelle struts, as specified by paragraphs (a)(1), (a)(2), (a)(3),
and (a)(4) of this AD, in accordance with Boeing Alert Service
Bulletin 747-54A2172, dated February 23, 1995, or Boeing Service
Bulletin 747-54A2172, Revision 1, dated January 4, 1996.
(1) Inspect the spring beam support fittings to detect cracks of
the support fittings.
(2) Inspect the spring beam support fittings at the fasteners,
using a borescope to detect cracks of the support fittings.
(3) Inspect the fasteners of the outer spring beam support
fittings to detect cracked or loose fasteners.
(4) Inspect the strut skin to detect cracks.
(b) If no discrepancy is found during any inspection required by
paragraph (a) of this AD, perform detailed visual inspections of the
outboard nacelle struts to detect any discrepancies specified in
paragraphs (b)(1), (b)(2), (b)(3), and (b)(4) of this AD, in
accordance with Boeing Alert Service Bulletin 747-54A2172, dated
February 23, 1995; or Boeing Service Bulletin 747-54A2172, Revision
1, dated January 4, 1996. Perform the inspection at the times
specified in paragraph (c) or (d) of this AD, as applicable.
(1) Perform a detailed visual inspection, using a borescope, of
only the outer spring beam support fittings at the fasteners through
the horizontal flange to detect cracks of the support fittings.
(2) Perform a detailed visual inspection, using a borescope, of
the fasteners through the vertical flange of only the outer spring
beam support fittings to detect loose collars.
(3) Perform an external detailed visual inspection of only the
outer spring beam support fittings to detect cracked or loose
fastener heads.
(4) Perform a detailed visual inspection of the strut skin to
detect cracks.
(c) For Model 747-SR series airplanes equipped with General
Electric Model CF6-45 series engines, on which no discrepancy is
found during any inspection required by paragraph (a) of this AD:
Perform the inspection required by paragraph (b) of this AD within
1,600 flight cycles following the accomplishment of the inspection
required by paragraph (a) of this AD; and thereafter at intervals
not to exceed 1,600 flight cycles until accomplishment of the
optional terminating action specified in paragraph (g) of this AD.
(d) For Model 747 series airplanes other than those identified
in paragraph (c) of this AD, on which no discrepancy is found during
any inspection required by paragraph (a) of this AD: Perform the
inspection required by paragraph (b) of this AD within 1,000 flight
cycles following the accomplishment of the inspection required by
paragraph (a) of this AD; and thereafter at intervals not to exceed
1,000 flight cycles until accomplishment of the optional terminating
action specified in paragraph (g) of this AD.
(e) If any cracking is found in the spring beam support fittings
during any inspection required by this AD, prior to further flight,
replace the support fitting with a new support fitting, in
accordance with the Accomplishment Instructions in Part IV. of
Boeing Service Bulletin 747-54A2172, Revision 1, dated January 4,
1996. Accomplishment of this replacement constitutes terminating
action for the repetitive inspection requirements of this AD for
only the new support fitting. Continue the repetitive inspections
required by paragraph (b) of this AD for the other support fitting
locations until accomplishment of the terminating action specified
by paragraph (g)(1) or (g)(2) of this AD, as applicable.
(f) If any crack is found on the strut skin, or if any cracked
or loose fastener or collar is found during any inspection required
by this AD, prior to further flight, 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
who has been authorized by the Manager, Seattle ACO, to make such
findings.
(g) Accomplishment of an open-hole high frequency eddy current
(HFEC) inspection, in accordance with Boeing Alert Service Bulletin
747-54A2172, dated February 23, 1995, or Boeing Service Bulletin
747-54A2172, Revision 1, dated January 4, 1996; and either paragraph
(g)(1) or (g)(2) of this AD, as applicable; constitutes terminating
action for the requirements of this AD.
(1) If no discrepancy is found during the HFEC inspection, prior
to further flight, rework the fastener holes and install new
fasteners, in accordance with Figures 6 and 7 of Boeing Alert
Service Bulletin 747-54A2172, dated February 23, 1995, or Boeing
Service Bulletin 747-54A2172, Revision 1, dated January 4, 1996.
(2) If any cracking is found during the HFEC inspection, prior
to further flight, replace any cracked spring beam support fitting
with a new support fitting, in accordance with Part IV. of the
Accomplishment Instructions specified by Boeing Service Bulletin
747-54A2172, Revision 1, dated January 4, 1996.
(h) 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, FAA. 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.
(i) 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. 98-31327 Filed 11-23-98; 8:45 am]
BILLING CODE 4910-13-U
