[Federal Register Volume 60, Number 4 (Friday, January 6, 1995)]
[Proposed Rules]
[Pages 2033-2036]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-307]
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Proposed Rules
Federal Register
________________________________________________________________________
This section of the FEDERAL REGISTER contains notices to the public of
the proposed issuance of rules and regulations. The purpose of these
notices is to give interested persons an opportunity to participate in
the rule making prior to the adoption of the final rules.
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Federal Register / Vol. 60, No. 4 / Friday, January 6, 1995 /
Proposed Rules
[[Page 2033]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-224-AD]
Airworthiness Directives; Boeing Model 747 Series Airplanes
Equipped With General Electric Model CF6-80C2 Series Engines or Pratt &
Whitney Model PW4000 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 March 3, 1995.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 94-NM-224-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-121S, 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-224-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-224-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
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 3 airworthiness directives (AD's)
that address various problems associated with the strut attachment
assembly on Model 747 series airplanes equipped with General Electric
Model CF6-80C2 series engines or Pratt & Whitney Model PW4000 series
engines. These AD's have required, among other things, inspection of
the strut, midspar fittings, diagonal brace, and midspar fuse pins.
Explanation of Service Information
Boeing recently has developed a modification of the strut-to-wing
attachment structure installed on certain Model 747 series airplanes
equipped with General Electric Model CF6-80C2 series engines or Pratt &
Whitney Model PW4000 series engines that 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
747-54A2156, dated December 15, 1994, which describes procedures for
modification of the nacelle strut and wing structure. This modification
entails the following:
1. Providing a new fail-safe load path by installing a new dual
side load fitting to the strut and the underwing structure and the
associated wing back-up fitting, front spar post, and side links;
2. Installing a new titanium dual side load fitting to the strut
aft bulkhead and [[Page 2034]] new 15-5 stainless steel midspar
fittings;
3. Replacing the aft bulkhead assembly and overhaul of the spring
beam;
4. Improving the strut-to-wing attachments by replacing the upper
link and the diagonal brace;
5. Reworking the rib of wing station (WS)1140; and
6. Modifying the electrical wiring and hydraulics by rerouting
certain wire bundles around the new dual side load fitting and
installing new hydraulic tubes.
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. Inspection and replacement of the bearings on the lower spar
fitting of the outboard engine strut with new bearings;
3. Installation of improved bushings in the strut-to-wing attach
fittings; and
4. Inspection and rework of improperly torqued fasteners.
Paragraph III, NOTES 8, 9, 10, and 11 of the Accomplishment
Instructions on page 91 of the alert service bulletin also describe
procedures for inspections and checks to detect discrepancies of the
adjacent structure, and correction of any discrepancies.
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 currently required by the
following AD's:
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Amendment Federal Register Date of
AD No. No. citation publication
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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.
------------------------------------------------------------------------
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 257 Model 747 series airplanes equipped
with General Electric Model CF6-80C2 series engines or Pratt & Whitney
Model PW4000 series engines of the affected design in the worldwide
fleet. The FAA estimates that 36 airplanes of U.S. registry would be
affected by this proposed AD.
The proposed modification would take approximately 6,253 work hours
per airplane to accomplish, at an average labor cost of $60 per work
hour. The manufacturer would incur the cost of labor, on a prorated
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 CF6-80C2 series engines or Pratt & Whitney Model
PW4000 series engines, which is estimated to be 5 years. Required parts
would be supplied by the manufacturer at no cost to the operators.
Based on these figures, the total cost impact of the proposed AD on
U.S. operators is estimated to be $3,376,620, or $93,795 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 747-54A2156, dated December 15,
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 excessive. Because AD's
[[Page 2035]] 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:
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-224-AD.
Applicability: Model 747 series airplanes having line positions
679 through 1046 inclusive, equipped with General Electric Model
CF6-80C2 series engines or Pratt & Whitney Model PW4000 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) Within 80 months after the effective date of this AD,
accomplish the modification of the nacelle strut and wing structure
in accordance with Boeing Alert Service Bulletin 747-54A2156, dated
December 15, 1994. 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 747-54A2156, dated December 15, 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 91 of Boeing Alert Service Bulletin 747-54A2156, dated December
15, 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 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-
54A2156, dated December 15, 1994, constitutes terminating action for
the inspections required by the following AD's:
------------------------------------------------------------------------
Amendment Federal Register Date of
AD No. No. citation publication
------------------------------------------------------------------------
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.
------------------------------------------------------------------------
(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.
[[Page 2036]] Issued in Renton, Washington, on December 30,
1994.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 95-307 Filed 1-5-95; 8:45 am]
BILLING CODE 4910-13-U
