[Federal Register Volume 60, Number 25 (Tuesday, February 7, 1995)]
[Proposed Rules]
[Pages 7140-7143]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-2930]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-252-AD]
Airworthiness Directives; Boeing Model 747 Series Airplanes
Equipped with Rolls Royce Model RB211 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 6, 1995.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 94-NM-252-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
[[Page 7141]] 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-252-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-252-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 9 AD's that address various problems
associated with the strut attachment assembly on Boeing Model 747
series airplanes that are equipped with Rolls Royce Model RB211 series
engines. These AD's have required, among other things, inspections of
the strut, and strut-to-wing attachment 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 Rolls Royce Model RB211 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
747-54A2157, dated January 12, 1995, 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, 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 replacing the tee fitting bolts common to the rib at wing
station (WS) 1140 [and for certain airplanes, installing a new
stiffener at the wing midspar];
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 5 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. Installation of improved bushings in the strut-to-wing
attachment fittings;
3. Replacement of certain strut-to-wing attachment fitting
fasteners; and
4. Inspection and torque check of certain fasteners of the strut-
to-wing attachment fittings.
Paragraph III, NOTES 8, 9, and 13 of the Accomplishment
Instructions on pages 109 and 110 of the alert service bulletin also
describes 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 required by the following
AD's:
[[Page 7142]]
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Federal Register
AD No. Amendment No. citation Date of publication
----------------------------------------------------------------------------------------------------------------
93-17-07-................................ 39-8678- 58 FR 45827- August 31, 1993.
93-03-14-................................ 39-8518- 58 FR 14513- March 18, 1993.
92-24-51-................................ 39-8439- 57 FR 60118- December 18, 1992.
90-20-20-................................ 39-6725- 55 FR 37859- September 14, 1990.
89-07-15-................................ 39-6167- 54 FR 11693- March 22, 1989.
87-04-13 R1-............................. 39-5836- 53 FR 2005- January 26, 1988.
86-05-11 R1-............................. 39-5334- 51 FR 21900- June 17, 1986.
86-23-01-................................ 39-5450- 51 FR 37712- October 26, 1986.
79-17-07-................................ 39-3533- 44 FR 50033- August 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
Currently, there are no Model 747 series airplanes of the affected
design, equipped with Rolls Royce Model RB211 series engines, on the
U.S. Register. However, should an affected airplane be imported and
placed on the U.S. Register in the future, it would require
approximately 6,545 work hours to accomplish the required actions, at
an average labor charge of $60 per work hour. The manufacturer would
incur the cost of labor, on a pro-rated basis, with 20 years being the
expected life of these airplanes. The median age for the fleet of Model
747 series airplanes equipped with Rolls Royce Model RB211 series
engines is estimated to be 6 years. Required parts would be supplied by
the manufacturer at no cost to operators. Based on these figures, the
total cost impact of this AD would be $117,810 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 5 of Boeing Alert Service Bulletin 747-54A2157, dated January 12,
1995, 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
[[Page 7143]] 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-252-AD.
Applicability: Model 747 series airplanes having line positions
292 through 1033 inclusive, equipped with Rolls Royce Model RB211
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 (c) 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-
54A2157, dated January 12, 1995, at the time specified in paragraph
(a)(1) or (a)(2) of this AD, as applicable. All of the terminating
actions described in the service bulletins listed in paragraph I.C.,
Table 2, ``Prior or Concurrent Service Bulletins,'' on page 5 of
Boeing Alert Service Bulletin 747-54A2157, dated January 12, 1995,
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.
(1) For Model 747-400 series airplanes having line positions 705
through 1033 inclusive, equipped with Rolls Royce Model RB211-524G
and H engines: Within 80 months after the effective date of this AD.
(2) For all other Model 747 series airplanes equipped with Rolls
Royce Model RB211 series engines not subject to the requirements of
paragraph (a)(1) of this AD: Within 56 months after the effective
date of this AD.
(b) Perform the inspections and checks specified in paragraph
III, NOTES 8, 9, and 13 of the Accomplishment Instructions on pages
109 and 110 of Boeing Alert Service Bulletin 747-54A2157, dated
January 12, 1995, 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-
54A2157, dated January 12, 1995, constitutes terminating action for
the inspections required by the following AD's:
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Federal Register
AD No. Amendment No. citation Date of publication
----------------------------------------------------------------------------------------------------------------
93-17-07-................................ 39-8678- 58 FR 45827- August 31, 1993.
93-03-14-................................ 39-8518- 58 FR 14513- March 18, 1993.
92-24-51-................................ 39-8439- 57 FR 60118- December 18, 1992.
90-20-20-................................ 39-6725- 55 FR 37859- September 14, 1990.
89-07-15-................................ 39-6167- 54 FR 11693- March 22, 1989.
87-04-13 R1-............................. 39-5836- 53 FR 2005- January 26, 1988.
86-05-11 R1-............................. 39-5334- 51 FR 21900- June 17, 1986.
86-23-01-................................ 39-5450- 51 FR 37712- October 26, 1986.
79-17-07-................................ 39-3533- 44 FR 50033- August 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 February 1, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 95-2930 Filed 2-6-95; 8:45 am]
BILLING CODE 4910-13-U