[Federal Register Volume 60, Number 1 (Tuesday, January 3, 1995)]
[Proposed Rules]
[Pages 66-69]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-32264]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-208-AD]
Airworthiness Directives; Boeing Model 747 Series Airplanes
Equipped With General Electric Model CF6-45 or -50 Series Engines, or
Pratt & Whitney Model JT9D-70 Series Engines
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 modification of the nacelle
strut and wing structure, inspections and checks to detect
discrepancies, and correction of discrepancies. This proposal is
prompted by the development of a modification of the strut and wing
structure that improves the fail-safe capability and durability of the
strut-to-wing attachments, and reduces reliance on inspections of those
attachments. The actions specified by the proposed AD are intended to
prevent failure of the strut and subsequent loss of the engine.
DATES: Comments must be received by February 28, 1995.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 94-NM-208-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-208-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-208-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056. [[Page 67]]
Discussion
The FAA has received numerous reports of fatigue cracking and/or
corrosion in the strut-to-wing attachments on Boeing Model 747 series
airplanes. In two cases, cracking resulted in the failure of a strut
load path and the subsequent loss of the number 3 engine and strut. In
both cases, catastrophic accidents occurred when the number 3 engine
and strut separated from the wing of the airplane and struck the number
4 engine, causing it to separate from the airplane. Investigation into
the cause of these accidents and other reported incidents has revealed
that fatigue cracks and corrosion in the strut-to-wing attachments, if
not detected and corrected in a timely manner, can result in failure of
the strut and subsequent separation of the engine from the airplane.
Investigation also has revealed that the structural fail-safe
capability of the strut-to-wing attachment is inadequate on these
airplanes.
The FAA has previously issued 13 AD's that address various problems
associated with the strut attachment assembly on Boeing Model 747
series airplanes that are equipped with General Electric Model CF6-45
or -50 series engines or Pratt & Whitney Model JT9D-70 series engines.
These AD's have required, among other things, inspections of the strut,
strut-to-wing attachment structure, and wing backup structure.
Explanation of Service Information
Boeing recently has developed a modification of the strut-to-wing
attachment structure installed on Model 747 series airplanes equipped
with General Electric Model CF6-45 or -50 series engines or Pratt &
Whitney Model JT9D-70 series engines. This modification significantly
improves the load-carrying capability and durability of the strut-to-
wing attachments. Such improvement also will substantially reduce the
possibility of fatigue cracking and corrosion developing in the
attachment assembly.
The FAA has reviewed and approved Boeing Alert Service Bulletin
747-54A2158, dated November 30, 1994, which describes procedures for
modification of the nacelle strut and wing structure. This modification
entails the following:
1. Changing the strut by adding a new titanium dual side load
fitting to the strut aft bulkhead, replacing the aft end of the midspar
web with a new 15-5 stainless steel web, installing new 15-5 stainless
steel midspar fittings on the inboard struts, and replacing the aft
bulkhead assembly and overhauling the spring beams on the outboard
struts;
2. Changing the wing structure by installing a new dual side load
underwing fitting and new support fitting, and replacing the end
fitting and installing a new stiffener at the wing midspar for the
outboard strut location [for certain airplanes, installing new inboard
backup fittings, installing new titanium outboard underwing fittings at
all strut positions, and replacing the tee fitting common to the rib at
wing station (WS) 1140; for certain other airplanes, replacing the tee
fitting bolts common to the rib at WS 1140];
3. Changing the electrical wiring and hydraulics by rerouting the
wire bundles around the new dual side load fitting, splicing additional
wire to the wire bundles, and installing new hydraulic tubes; and
4. Installing the strut with a new upper link, a new diagonal
brace, and new side links.
This alert service bulletin specifies that the modification of the
nacelle strut and wing structure is to be accomplished prior to, or
concurrently with, the terminating actions described in the service
bulletins listed in paragraph I.C., Table 2, ``Prior or Concurrent
Service Bulletins,'' on page 7 of this alert service bulletin. These
terminating actions include the following:
1. Replacement of the diagonal brace, midspar and upper link fuse
pins with new third generation 15-5 corrosion resistant steel fuse
pins;
2. Replacement of the strut-to-diagonal brace aluminum attach
fitting on the inboard engine with a steel fitting;
3. Installation of a large skin doubler and frame stiffener in the
area of the precooler exhaust vent;
4. A zero-time overhaul of the springbeams and rework of certain
fastener holes of the springbeam support fittings of the outboard
strut;
5. Inspection and torque check of certain fasteners of the strut-
to-wing attachment fittings; and
6. Modification of the rib at wing station 669.5.
Explanation of the Provisions of the Proposed AD
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 modification of the nacelle strut and wing
structure, inspections and checks to detect discrepancies in the
adjacent structure, and correction of discrepancies. The actions would
be required to be accomplished in accordance with the alert service
bulletin described previously.
The FAA has determined that long term continued operational safety
will be better assured by design changes to remove the source of the
problem, rather than by repetitive inspections. Long term inspections
may not be providing the degree of safety assurance necessary for the
transport airplane fleet. This, coupled with a better understanding of
the human factors associated with numerous continual inspections, has
led the FAA to consider placing less emphasis on inspections and more
emphasis on design improvements. The proposed modification requirement
is in consonance with these considerations.
Accomplishment of the modification of the nacelle strut and wing
structure would terminate the inspections required by the following
AD's:
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Amendment Federal Register
AD No. No. citation- Date of Publication
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94-22-08........... 39-9057 59 FR 58761..... Nov. 15, 1994.
93-17-07........... 39-8678 58 FR 45827..... Aug. 31, 1993.
93-03-14........... 39-8518 58 FR 14513..... Mar. 18, 1993.
92-24-51........... 39-8439 57 FR 60118..... Dec. 18, 1992.
90-20-20........... 39-6725 55 FR 37859..... Sept. 14, 1990.
89-07-15........... 39-6167 54 FR 11693..... Mar. 22, 1989.
87-04-13 R1-....... 39-5836 53 FR 2005...... Jan. 26, 1988.
86-23-01........... 39-5450 51 FR 37712..... Oct. 24, 1986.
86-08-03........... 39-5289 51 FR 12836..... Apr. 16, 1986.
86-07-06........... 39-5270 51 FR 10821..... Mar. 31, 1986.
86-05-11 R1-....... 39-5334 51 FR 21900-.... June 17, 1986.
[[Page 68]]
80-08-02........... 39-3738 45 FR 24450..... Apr. 10, 1980.
79-17-07........... 39-3533 44 FR 50033..... Aug. 27, 1979.
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As a result of recent communications with the Air Transport
Association (ATA) of America, the FAA has learned that, in general,
some operators may misunderstand the legal effect of AD's on airplanes
that are identified in the applicability provision of the AD, but that
have been altered or repaired in the area addressed by the AD. The FAA
points out that all airplanes identified in the applicability provision
of an AD are legally subject to the AD. If an airplane has been altered
or repaired in the affected area in such a way as to affect compliance
with the AD, the owner or operator is required to obtain FAA approval
for an alternative method of compliance with the AD, in accordance with
the paragraph of each AD that provides for such approvals. A note has
been included in this notice to clarify this requirement.
Cost Estimate
There are approximately 145 Model 747 series airplanes of the
affected design, equipped with General Electric Model CF6-45 or -50
series engines or Pratt & Whitney Model JT9D-70 series engines in the
worldwide fleet. The FAA estimates that 12 airplanes of U.S. registry
would be affected by this proposed AD.
The proposed modification may take as many as 6,600 to 7,151 work
hours to accomplish, depending upon the configuration of the airplane.
The manufacturer would incur the cost of labor, on a pro-rated basis,
with 20 years being the expected life of these airplanes. The total
cost impact of the proposed AD on U.S. operators is based on the median
age for the fleet of Model 747 series airplanes equipped with General
Electric Model CF6-45 or -50 series engines or Pratt & Whitney Model
JT9D-70 series engines, which is estimated to be 15 years. The average
labor rate is estimated to be $60 per work hour. Required parts would
be supplied by the manufacturer at no cost to the operator. Based on
these figures, the cost impact of this proposal on U.S. operators is
estimated to be between $3,564,000 ($297,000 per airplane) and
$3,861,540 ($321,795 per airplane).
This cost impact figure does not reflect the cost of the
terminating actions described in the service bulletins listed in
paragraph I.C., Table 2, ``Prior or Concurrent Service Bulletins,'' on
page 7 of Boeing Alert Service Bulletin 747-54A2158, dated November 30,
1994, that are proposed to be accomplished prior to or concurrently
with the modification of the nacelle strut and wing structure. Since
some operators may have accomplished certain modifications on some or
all of the airplanes in its fleet, while other operators may not have
accomplished any of the modifications on any of the airplanes in its
fleet, the FAA is unable to provide a reasonable estimate of the cost
of accomplishing the terminating actions described in the service
bulletins listed in Table 2 of the Boeing alert service bulletin. As
indicated earlier in this preamble, the FAA invites comments
specifically on the overall economic aspects of this proposed rule. Any
data received via public comments to this notice will aid the FAA in
developing an accurate accounting of the cost impact of the rule.
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.
The FAA recognizes that the obligation to maintain aircraft in an
airworthy condition is vital, but sometimes expensive. Because AD's
require specific actions to address specific unsafe conditions, they
appear to impose costs that would not otherwise be borne by operators.
However, because of the general obligation of operators to maintain
aircraft in an airworthy condition, this appearance is deceptive.
Attributing those costs solely to the issuance of this AD is
unrealistic because, in the interest of maintaining safe aircraft,
prudent operators would accomplish the required actions even if they
were not required to do so by the AD.
A full cost-benefit analysis has not been accomplished for this
proposed AD. As a matter of law, in order to be airworthy, an aircraft
must conform to its type design and be in a condition for safe
operation. The type design is approved only after the FAA makes a
determination that it complies with all applicable airworthiness
requirements. In adopting and maintaining those requirements, the FAA
has already made the determination that they establish a level of
safety that is cost-beneficial. When the FAA, as in this proposed AD,
makes a finding of an unsafe condition, this means that the original
cost-beneficial level of safety is no longer being achieved and that
the proposed actions are necessary to restore that level of safety.
Because this level of safety has already been determined to be cost-
beneficial, a full cost-benefit analysis for this proposed AD would be
redundant and unnecessary.
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:
[[Page 69]] 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 adding the following new
airworthiness directive:
BOEING: Docket 94-NM-208-AD.
Applicability: Model 747 series airplanes, equipped with General
Electric Model CF6-45 or -50 series engines, or Pratt & Whitney
Model JT9D-70 series engines; 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 use the authority
provided in paragraph (d) to request approval from the FAA. This
approval may address either no action, if the current configuration
eliminates the unsafe condition; or different actions necessary to
address the unsafe condition described in this AD. Such a request
should include an assessment of the effect of the changed
configuration on the unsafe condition addressed by this AD. In no
case does the presence of any modification, alteration, or repair
remove any airplane from the applicability of this AD.
Compliance: Required as indicated, unless accomplished
previously.
To prevent failure of the strut and subsequent loss of the
engine, accomplish the following:
(a) Accomplish the modification of the nacelle strut and wing
structure in accordance with Boeing Alert Service Bulletin 747-
54A2158, dated November 30, 1994, within 56 months after the
effective date of this AD. All of the terminating actions described
in the service bulletins listed in paragraph I.C., Table 2, ``Prior
or Concurrent Service Bulletins,'' on page 7 of Boeing Alert Service
Bulletin 747-54A2158, dated November 30, 1994, must be accomplished
in accordance with those service bulletins prior to, or concurrently
with, the accomplishment of the modification of the nacelle strut
and wing structure required by this paragraph.
(b) Perform the inspections and checks specified in paragraph
III, NOTES 8, 9, 10, and 11 of the Accomplishment Instructions on
page 129 of Boeing Alert Service Bulletin 747-54A2158, dated
November 30, 1994, concurrently with the modification of the nacelle
strut and wing structure required by paragraph (a) of this AD. Prior
to further flight, correct any discrepancies found in accordance
with the alert service bulletin.
(c) Accomplishment of the modification of the nacelle strut and
wing structure in accordance with Boeing Alert Service Bulletin 747-
54A2158, dated November 30, 1994, constitutes terminating action for
the inspections required by the following AD's:
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Amendment Federal Register
AD No. No. citation- Date of Publication
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94-22-08........... 39-9057 59 FR 58761..... Nov. 15, 1994.
93-17-07........... 39-8678 58 FR 45827..... Aug. 31, 1993.
93-03-14........... 39-8518 58 FR 14513..... Mar. 18, 1993.
92-24-51........... 39-8439 57 FR 60118..... Dec. 18, 1992.
90-20-20........... 39-6725 55 FR 37859..... Sept. 14, 1990.
89-07-15........... 39-6167 54 FR 11693..... Mar. 22, 1989.
87-04-13 R1........ 39-5836 53 FR 2005...... Jan. 26, 1988.
86-23-01........... 39-5450 51 FR 37712..... Oct. 24, 1986.
86-08-03........... 39-5289 51 FR 12836..... Apr. 16, 1986.
86-07-06........... 39-5270 51 FR 10821..... Mar. 31, 1986.
86-05-11 R1-....... 39-5334 51 FR 21900-.... Jun. 17, 1986.
80-08-02........... 39-3738 45 FR 24450..... Apr. 10, 1980.
79-17-07........... 39-3533 44 FR 50033..... Aug. 27, 1979.
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(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 Aircraft Certification
Office (ACO), FAA, Transport Airplane Directorate. 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 December 27, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-32264 Filed 12-30-94; 8:45 am]
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