[Federal Register Volume 64, Number 203 (Thursday, October 21, 1999)]
[Proposed Rules]
[Pages 56709-56712]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-27564]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-NM-186-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 767 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Supplemental notice of proposed rulemaking; reopening of
comment period.
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SUMMARY: This document revises an earlier proposed airworthiness
directive (AD), applicable to certain Boeing Model 767 series
airplanes, that would have required repetitive inspections to ensure
the proper condition of the engine thrust link components, and follow-
on corrective action, if necessary; and replacement of the end cap
assembly with an improved assembly. Such replacement, when
accomplished, would terminate the repetitive inspections. That proposal
was prompted by a report of fatigue cracking of end cap bolts caused by
improper installation. This new action revises the proposed rule by
adding a repair requirement and by clarifying the type of inspection
and terminology used in describing the parts to be inspected. The
actions specified by this new AD are intended to prevent failure of the
end cap assembly, which could lead to separation of the engine from the
airplane in the event of a primary thrust linkage failure.
DATES: Comments must be received by November 10, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 97-NM-186-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. This information may be examined at the FAA, Transport
Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.
FOR FURTHER INFORMATION CONTACT: James G. Rehrl, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (425) 227-2783; 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 97-NM-186-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. 97-NM-186-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
A proposal to amend part 39 of the Federal Aviation Regulations (14
CFR part 39) to add an airworthiness directive (AD), applicable to
certain Boeing Model 767 series airplanes, was published as a notice of
proposed rulemaking (NPRM) in the Federal Register on May 20, 1998 (63
FR 27696). That NPRM would have required repetitive inspections to
detect improper installation or fatigue damage of the end cap of the
forward engine mount, and replacement of the end cap assembly with an
improved assembly. Such replacement, when accomplished, would terminate
the repetitive inspections. That NPRM was prompted by a report of
fatigue cracking of end cap bolts caused by improper installation. That
condition, if not corrected, could result in failure of the end cap
assembly, which could lead to separation of the engine from the
airplane in the event of a primary thrust linkage failure.
Comments
Due consideration has been given to the comments received in
response to the NPRM:
One commenter states that it is not affected by the proposal
because its Model 767-200ER series airplanes are powered by General
Electric engines. Another commenter generally supports the proposal.
Request To Withdraw the Original NPRM
One commenter does not consider that issuance of the original NPRM
is necessary for the following reasons:
1. The commenter states that ``regulatory action mandating
incorporation of Boeing Alert Service Bulletin 767-71A0087 is
unwarranted for JT9D powered Model 767 aircraft'' for several reasons.
First, the original
[[Page 56710]]
NPRM was issued solely because the part numbers of the end caps and
bolts on Model 767 and Model 747-400 series airplanes are the same.
Second, the alert service bulletin was issued on the basis of one
report of broken end cap bolts by one operator of a Model 747-400
series airplane.
The FAA does not concur that the original NPRM should be withdrawn.
Issuance of the original NPRM was not based on the fact that both end
caps have the same part number, but on the fact that the configuration
of the end cap assembly is identical. The configuration of the end cap
assembly for Model 767 and 747 series airplanes is identical in all
relevant respects. Therefore, if an end cap assembly is installed
incorrectly in either of those airplane models, the same unsafe
condition is likely to occur. In addition, the unsafe condition is
likely to occur regardless of whether the airplane is powered by Pratt
& Whitney Model JT9D or Model PW4000 series engines, as the
installations of those airplane engines also are identical. In light of
this, the FAA has determined that an unsafe condition exists. No change
to the supplemental NPRM is necessary in this regard.
2. The commenter states that the cause of the bolt failure on a
Model 747-400 series airplane was attributed to a personnel error when
the end cap was installed backwards. The commenter adds that one
isolated incident involving a personnel error ``does not warrant
drastic repetitive inspections.''
The FAA does not concur that the original NPRM should be withdrawn.
While personnel error was involved in the mis-installation of the end
cap, it is the ease by which an end cap can be installed backwards that
makes it likely that this condition could exist on other airplanes. For
this reason, the FAA considers that an unsafe condition is likely to
develop on other airplane models of the same design, and that issuance
of this AD and the repetitive inspections required by this AD are
necessary to ensure continued operational safety. No change to the
supplemental NPRM is necessary in this regard.
3. The commenter states that the end cap and bolts are routinely
inspected for defects when they are removed from the assembly. In
addition, in the entire operating history of Model 767 series airplanes
powered by Pratt & Whitney Model JT9D series engines, there is no
documented event of any operator experiencing failure of an end cap or
bolt. Further, there is no evidence that the end caps were ever
installed backwards on any Model 767 series airplane.
The FAA does not concur that the original NPRM should be withdrawn.
Even though the operator may conduct a routine inspection of the end
cap and bolts for defects, additional inspections are required because
of the possibility of early fatigue failure. The FAA considers this AD
necessary in order to address two major concerns:
First, if an end cap were installed incorrectly, it would
automatically pick up thrust loads on every flight and result in an
early fatigue failure of the end cap assembly. Thus, if the primary
load path provided by the thrust links, evener bar, and engine lugs
were to then experience a failure, the engine would separate from the
airplane almost immediately.
Second, investigation has revealed that even a properly
installed end cap assembly has an inadequate fatigue life. Analysis and
testing indicate that if the primary load path fails, the end cap
assembly then would react all of the new loads and cause the end cap
assembly to fail within a relatively small number of flight cycles.
Such failure would occur even if the end cap assembly had been entirely
intact at the time the primary load path failed. For this reason, the
original NPRM specifies repetitive inspections of the primary load path
(i.e., the thrust link, evener bar, and engine lugs) until
accomplishment of the replacement action specified in Work Packages 3
or 4.
The FAA considers that the lack of defects found in the operator's
end caps implies merely that the original end caps were installed
correctly, as a properly installed end cap would not react any loads
during normal flight operations, thereby making it unlikely that any
fatigue damage would have occurred. However, because it has been
determined that the existing end cap assembly has an inadequate fatigue
life, the FAA considers that the requirements of this AD are necessary
to ensure the operational safety of the fleet. No change to the
supplemental NPRM is necessary in this regard.
4. The commenter states that the alert service bulletin mandates a
visual check and an ultrasonic on-wing [non-destructive test (NDT)]
inspection of the evener bar and thrust links for the engine mounts for
Pratt & Whitney Model JT9D series engines, but no on-wing ultrasonic
inspection is specified for Model PW4000 series engines. If repetitive
on-wing ultrasonic inspections are waived for the higher thrust Model
PW4000 series engines, there is no justification to require those
inspections for the lower thrust Model JT9D series engines. Further,
the operating history of airplanes powered by Model JT9D series engines
does not support any regulatory action regarding the forward lower
engine mount.
The FAA does not concur that the original NPRM should be withdrawn.
The FAA points out that the original NPRM makes it clear in the
``Differences'' paragraph that the two airplane groups for Model 767
series airplanes, Group 1 airplanes (with JT9D engines) and Group 2
airplanes (with PW4000 engines), are to be treated exactly the same.
According to the manufacturer's fleet utilization data base, there
should never be a case of any Group 2 airplane ever reaching the
threshold of 16,000 flight cycles before it reaches the 3-year
compliance time for the mandatory terminating action. Although the
logic diagram in Figure 1 of the alert service bulletin specifies that
operators of Group 2 airplanes (i.e., airplanes with Model PW4000
series engines) [with more than 16,000 flight cycles] should contact
the manufacturer, the FAA considers that this instruction was included
on the off-chance that an airplane might fall into this category.
However, this does not imply that any such airplanes would be waived
from the NDT inspection requirements. On the contrary, such airplanes
would be handled on a case-by-case basis, with every expectation that
NDT inspections would be required at shorter inspection intervals
because of the higher fatigue damage that could be caused by the higher
thrust Model PW4000 series engines. No change to the supplemental NPRM
is necessary.
Request To Clarify Inspection Requirements and Components To Be
Inspected
One commenter, the manufacturer, requests certain changes to the
``Explanation of Relevant Service Information'' paragraph in the
original NPRM. The commenter contends that the AD should refer to
inspections of the ``engine thrust link components'' rather than to
inspections of the ``end cap.''
The FAA concurs that the commenter's suggested changes add clarity
and technical accuracy to the supplemental NPRM. Additionally, Boeing
Alert Service Bulletin 767-71A0087, dated October 10, 1996, does not
specify inspections of the ``end cap,'' but only includes inspections
of the ``forward engine mount'' to ensure that the thrust links, evener
bar, associated engine lugs, and attaching hardware are firmly
attached. Although the ``Explanation of Relevant Service Information''
paragraph is not included
[[Page 56711]]
in this supplemental NPRM, the FAA has determined that certain changes
are necessary in this AD for several reasons.
The FAA considers that requiring operators ``to ensure the proper
condition of the engine thrust link components'' more accurately
describes the action required for the inspection rather than ``to
detect improper installation or fatigue damage of the end cap of the
forward engine mount.'' The FAA points out that ``fatigue damage of the
end cap of the forward engine mount,'' which involves the secondary
load path, could not be detected until the forward engine mount was
disassembled. In addition, the inspections specified by the alert
service bulletin are for ``engine thrust link components,'' not the
``end cap'' itself.
This supplemental NPRM correlates the corrective action to the
presence or absence of damage to the engine thrust link components. In
addition, the engine thrust link components, which involve the primary
load path, can be inspected with no disassembly of the forward engine
mount. In light of this information, the FAA has made the appropriate
changes to the ``Summary'' paragraph of this supplemental NPRM.
Request To Include Repair of Discrepancies
One commenter, the manufacturer, requests that paragraph (d) of the
original NPRM be revised to require that all discrepancies or damage
found be repaired in accordance with an approved FAA procedure.
The FAA concurs partially. The action required by paragraph (d) of
the original NPRM is now included in paragraphs (c), (c)(1), and (c)(2)
of the supplemental NPRM. The repair requirement is added in paragraph
(c)(1), and the action for accomplishment of Work Package 3 is included
in paragraph (c)(2). Because the repair procedures are not specified in
Work Package 3 of the alert service bulletin, it is necessary for this
supplemental NPRM to require that any repairs be accomplished in
accordance with a method approved by the Manager, Seattle Aircraft
Certification Office (ACO).
Explanation of Changes Made to the Supplemental NPRM
The FAA has clarified one of the inspection requirements contained
in the original NPRM. Whereas the original NPRM specified the
accomplishment of Work Package 1 (visual inspection of the forward
engine mount), the FAA has revised this supplemental NPRM to clarify
that its intent is to require a detailed visual inspection.
Additionally, a note has been added to the supplemental NPRM to define
that inspection.
The FAA has deleted the reference to paragraph (c) that was
included in paragraph (a) of the original NPRM, which stated that
``Where Boeing Alert Service Bulletin 767-71A0087, dated October 10,
1996, specifies that the actions required by this AD may be
accomplished in accordance with an operator's equivalent procedure,'
the actions must be accomplished in accordance with Chapter 71-00-00 of
the Boeing 767 Airplane Maintenance Manual (AMM), as specified in the
alert service bulletin.'' The FAA has determined that the required
inspections and replacement actions specified in paragraphs (a), (b),
and (c)(2) of the supplemental NPRM are adequately addressed in the
alert service bulletin. Therefore, reference to a specific chapter of
the AMM is not necessary.
Paragraphs (a)(1) and (a)(2) of this supplemental NPRM have been
revised to clarify the inspection requirements.
Explanation of Changes Made to This Final Rule
The FAA has clarified the inspection requirement contained in the
proposed AD. Whereas the proposal specified a visual inspection, the
FAA has revised this final rule to clarify that its intent is to
require a detailed visual inspection. Additionally, a note has been
added to the final rule to define that inspection.
Conclusion
Since these changes expand the scope of the originally proposed
rule, the FAA has determined that it is necessary to reopen the comment
period to provide additional opportunity for public comment.
Cost Impact
There are approximately 239 Model 767 series airplanes of the
affected design in the worldwide fleet. The FAA estimates that 96
airplanes of U.S. registry will be affected by this AD, that it will
take approximately 37 work hours per airplane (18.5 work hours per
engine) to accomplish the required inspections, and that the average
labor rate is $60 per work hour. Based on these figures, the cost
impact of the AD on U.S. operators is estimated to be $213,120, or
$2,220 per airplane, per inspection cycle.
It will take approximately 135 work hours per airplane (67.5 work
hours per engine) to accomplish the required replacement of the forward
engine mount end cap and bolts, and the average labor rate is $60 per
work hour. Required parts would cost approximately $1,000 per airplane.
Based on these figures, the cost impact of the AD on U.S. operators is
estimated to be $873,600, or $9,100 per airplane.
The cost impact figures discussed above are based on assumptions
that no operator has yet accomplished any of the requirements of this
AD action, and that no operator would accomplish those actions in the
future if this AD were not adopted.
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 97-NM-186-AD.
[[Page 56712]]
Applicability: Model 767 series airplanes, powered by Pratt &
Whitney Model JT9D or Model PW4000 series engines, as listed in
Boeing Alert Service Bulletin 767-71A0087, dated October 10, 1996;
certificated in any category.
Note: 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.
To prevent possible separation of the engine from the airplane
in the event of a primary thrust linkage failure, accomplish the
following:
Initial and Repetitive Inspections
(a) For Groups 1 and 2 airplanes: Accomplish paragraphs (a)(1),
(a)(2), and (a)(3) of this AD, as applicable, in accordance with
Boeing Alert Service Bulletin 767-71A0087, dated October 10, 1996.
(1) Within 500 flight hours or 300 flight cycles after the
effective date of this AD, whichever occurs later: Accomplish Work
Package 1 (a detailed visual inspection of the forward engine mount
to ensure that the thrust link, evener bar, associated lugs, and
attaching hardware are firmly attached). Thereafter, repeat Work
Package 1 at the intervals specified in the alert service bulletin
until the requirements of either paragraph (a)(2) or (a)(3) of this
AD are accomplished.
Note 2: For the purposes of this AD, a detailed visual
inspection is defined as: ``An intensive visual examination of a
specific structural area, system, installation, or assembly to
detect damage, failure, or irregularity. Available lighting is
normally supplemented with a direct source of good lighting at an
intensity deemed appropriate by the inspector. Inspection aids such
as mirrors, magnifying lenses, etc. may be used. Surface cleaning
and elaborate access procedures may be required.''
(2) Prior to the accumulation of 16,000 total flight cycles on
any engine or within 500 flight hours or 300 flight cycles after the
effective date of this AD, whichever occurs latest: Accomplish Work
Package 2 (non-destructive test inspection of the forward engine
mount to ensure the proper condition of the engine thrust link
components). Thereafter, repeat Work Package 2 on that engine at the
intervals specified in the alert service bulletin until the
requirements of paragraph (a)(3) of this AD are accomplished.
Accomplishment of Work Package 2 constitutes terminating action for
the repetitive inspections required by paragraph (a)(1) of this AD
for that engine.
Replacement and Terminating Action
(3) Within 3 years after the effective date of this AD:
Accomplish Work Package 3 (end cap and bolt replacement of the
forward engine mount). Accomplishment of Work Package 3 constitutes
terminating action for the requirements of this AD for Groups 1 and
2 airplanes.
(b) For Group 3 airplanes: Within 3 years after the effective
date of this AD, accomplish Work Package 4 (bolt replacement) in
accordance with Boeing Alert Service Bulletin 767-71A0087, dated
October 10, 1996.
Repair and Replacement Action
(c) For all airplanes: If any discrepancy (including an
improperly installed or damaged engine thrust link component) is
found during any inspection required by this AD, prior to further
flight, accomplish the actions required by paragraphs (c)(1) and
(c)(2) of this AD.
(1) Repair any discrepancies in accordance with a method
approved by the Manager, Seattle Aircraft Certification Office
(ACO), FAA, Transport Airplane Directorate. For a repair method to
be approved by the Manager, Seattle ACO, as required by this
paragraph, the Manager's approval letter must specifically reference
this AD.
(2) Accomplish Work Package 3 in accordance with Boeing Alert
Service Bulletin 767-71A0087, dated October 10, 1996.
Spares
(d) As of the effective date of this AD, no person shall install
a forward engine mount end cap having part number 310T3026-1 on any
airplane.
Alternative Method of Compliance
(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, 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 3: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
Special Flight Permits
(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 October 15, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-27564 Filed 10-20-99; 8:45 am]
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