[Federal Register Volume 89, Number 236 (Monday, December 9, 2024)]
[Rules and Regulations]
[Pages 97484-97492]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-28780]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2023-2403; Project Identifier AD-2023-00888-T;
Amendment 39-22893; AD 2024-24-03]
RIN 2120-AA64
Airworthiness Directives; The Boeing Company Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
-----------------------------------------------------------------------
SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain The Boeing Company Model MD-11 and MD-11F airplanes. This AD
was prompted by a report of a Model MD-11F airplane experiencing an
uncommanded deployment of a thrust reverser in flight at low altitude.
This AD requires initial and repetitive detailed inspections and
repetitive wire integrity tests of the engine pylon thrust reverser
control system wire harnesses, junction box assembly and junction box
cover, left-side and right-side thrust reverser electrical harnesses,
core (engine compartment) miscellaneous wire harness assembly, and 30-
degree bulkhead wire harness assembly; and applicable on-condition
actions. This AD also requires reporting inspection results. The FAA is
issuing this AD to address the unsafe condition on these products.
DATES: This AD is effective January 13, 2025.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of January 13,
2025
ADDRESSES:
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2023-2403; or in person at Docket Operations between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD
docket contains this final rule, any comments received, and other
information. The address for Docket Operations is U.S. Department of
Transportation, Docket Operations, M-30, West Building Ground Floor,
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
Material Incorporated by Reference:
For Boeing material identified in this AD, contact Boeing
Commercial Airplanes, Attention: Contractual & Data Services (C&DS),
2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600;
telephone 562-797-1717; website myboeingfleet.com.
[[Page 97485]]
You may view this material at the FAA, Airworthiness
Products Section, Operational Safety Branch, 2200 South 216th St., Des
Moines, WA. For information on the availability of this material at the
FAA, call 206-231-3195. It is also available at regulations.gov under
Docket No. FAA-2023-2403.
FOR FURTHER INFORMATION CONTACT: Tak Kobayashi, Aviation Safety
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; telephone
206-231-3553; email [email protected].
SUPPLEMENTARY INFORMATION:
Background
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to certain The Boeing
Company Model MD-11 and MD-11F airplanes equipped with General Electric
(GE) CF6-80C2D1F high-bypass turbofan engines. The NPRM published in
the Federal Register on December 29, 2023 (88 FR 90134). The NPRM was
prompted by a report of a Model MD-11F airplane equipped with three GE
CF6-80C2D1F high-bypass turbofan engines experiencing an uncommanded
deployment of a thrust reverser in flight at low altitude. In the NPRM,
the FAA proposed to require a one-time detailed inspection of the
engine pylon thrust reverser control system wire harnesses; repetitive
detailed inspections and wire integrity tests of the engine pylon
thrust reverser control system wire harnesses, junction box assembly
and junction box cover, left-side and right-side thrust reverser
electrical harnesses, core (engine compartment) miscellaneous wire
harness assembly, and 30-degree bulkhead wire harness assembly; and
applicable on-condition actions. The FAA also proposed to require
reporting inspection results. The FAA is issuing this AD to address
uncommanded deployment of a thrust reverser in flight at low altitude,
which could result in loss of flight control of the airplane and loss
of continued safe flight and landing.
Discussion of Final Airworthiness Directive
Comments
The FAA received a comment from the Air Line Pilots Association,
International (ALPA), who supported the NPRM without change.
The FAA received additional comments from five commenters,
including Boeing, FedEx Express (FedEx), United Parcel Service (UPS),
and two individuals. The following presents the comments received on
the NPRM and the FAA's response to each comment.
Request To Delete an Incorrect Location
Boeing requested that the FAA delete the text ``(in the pylon)'' in
the Summary and Material Incorporated by Reference under 1 CFR part 51
section of the NPRM. Boeing explained that the text ``(in the pylon)''
implies that the wire integrity tests shall be applied only to the
pylon wiring as part of the repetitive wire integrity tests. Boeing
stated that these tests also apply to the engine pylon thrust reverser
control system wiring from the nose of the airplane.
The FAA agrees with the request. While a detailed inspection is
performed on the wire harnesses in the pylon, the location for
performing the wire integrity tests of the engine pylon thrust reverser
control system wire harnesses is not limited to the pylon. The FAA has
deleted the text ``(in the pylon)'' in this final rule accordingly.
Concern for the Workability of the Service Bulletin
FedEx expressed their concern regarding the workability of Boeing
Alert Service Bulletin MD11-78A017, dated December 4, 2023. FedEx
stated that a prime example of complexity in Work Package 2 of Boeing
Alert Service Bulletin MD11-78A017, dated December 4, 2023, is Part 19,
which requires actions to be concurrently performed on the left and
right thrust reverser halves, instead of having two separate PARTs to
perform required actions on each thrust reverser half independently
from the other thrust reverser half. This results in the need to
evaluate four possible conditions of the wire harnesses on the left and
right thrust reverser halves. The commenter stated that due to
complexity of the service bulletin as well as the sheer scope of the
work being performed, a significant risk exists for introducing human
errors during the accomplishment of the required work.
The FAA recognizes that the work instructions provided in this
service bulletin are extensive and complex. Boeing Alert Service
Bulletin MD11-78A017, dated December 4, 2023, was revised to Revision
1, dated June 4, 2024, to correct errors and improve clarity. The FAA
reviewed Revision 1 of the service bulletin and determined it provides
adequate information. Although the work instructions provided in the
original and revised service bulletins are extensive and complex, the
actions specified in the service bulletin that is required by this AD
are necessary to address the unsafe condition. This AD mandates Boeing
Alert Service Bulletin MD11-78A017, Revision 1, dated June 4, 2024, and
provides credit for actions accomplished before the effective date of
this AD using Boeing Alert Service Bulletin MD11-78A017, dated December
4, 2023. In addition, the exception in paragraph (h)(2) of the proposed
AD was addressed and corrected in Revision 1 of the service bulletin;
therefore, paragraph (h)(2) of the proposed AD was removed from this
AD. The current instructions in Boeing Alert Service Bulletin MD11-
78A017, dated December 4, 2023, and Revision 1, dated June 4, 2024, can
be followed without any major issue that would prevent accomplishment
of the required actions. Further, additional actions in the revised
service bulletin are intended for best maintenance practice and not
necessary to address the unsafe condition. Those additional actions
include the detailed inspection of the junction box assembly for any
loose electrical connection in Step 1, Part 10, and application of
torque to any loose electrical connection in Step 2, Part 11 of the
revised service bulletin. Therefore, those parts in either the original
or Revision 1 of the service bulletin are acceptable for compliance
with the AD. For clarity, the FAA added a new exception to paragraph
(h) of this AD specifying the added steps in Revision 1 of the service
bulletin are not required for compliance with the AD.
Request To Remove Work Package 2
FedEx stated that Work Package 2 in Boeing Alert Service Bulletin
MD11-78A017, dated December 4, 2023, is too broad in scope, and not
supported or warranted by the results of the investigation. FedEx
stated that a third protection feature to prevent in-flight thrust
reverser deployment is not required for Model MD-11 airplanes since it
was predicted that the airplane will be controllable with the thrust
reverser deployed in air. FedEx stated that the outcome of the service
event has served to validate this prediction. FedEx further stated that
damaged wire bundles and grounds in the pylon discovered on the event
airplane could have allowed energization of the pressure regulator
shutoff valve (PRSOV) and directional pilot valve (DPV), which could
result in in-flight thrust reverser deployment. No other element that
could have contributed to the event was found by the investigation.
Finally, FedEx stated that the actions in Work Package 2 will disturb
the areas that are not routinely disturbed and therefore could
introduce unintended consequences. FedEx added
[[Page 97486]]
that to properly accomplish Work Package 2, it is necessary to expend
significant resources to deal with the complexity and extent of the
requirements, including training of personnel.
The FAA does not agree with the request. The FAA infers that FedEx
is requesting that Work Package 2 be removed from the requirements of
the AD. Although the event airplane was safely brought back to the
ground after in-flight uncommanded thrust reverser deployment, this
does not suggest that Model MD-11 airplanes will be controllable under
any anticipated operating condition with the thrust reverser deployed
in air. Model MD-11 airplanes have not been demonstrated for their
controllability when the deployment of single or dual thrust reverser
halves is encountered on any single engine at low altitudes under
anticipated operating conditions. The wiring damage discovered in the
pylon of the event airplane was for the PRSOV and DPV circuits, and the
manufacturer concluded that this damage was a contributing factor to
the event. However, it is unclear what conditions resulted in power-to-
power short--instead of power-to-ground \1\ (shield), which would not
result in uncommanded thrust reverser deployment. Based on available
data, it is likely that a combination of conditions needs to be
encountered to result in uncommanded thrust reverser deployment.
Considering the age of the affected fleet, undetected degradation in
wiring installation could have contributed to the event. Such a latent
wiring anomaly could make an airplane vulnerable to a single failure
that would impose a significant risk. Work Package 1 requires
inspections of wiring in the pylon to detect any damage, and this
action is intended to eliminate any similar condition discovered on the
event airplane in a quick and practical manner. Work Package 2 requires
wire integrity tests in addition to inspections of various wiring
harnesses, and those actions are necessary to prevent and detect a
potential latent anomalous condition of wiring installation. The FAA
agrees that those actions are extensive, and the areas affected by the
required actions are not routinely disturbed. However, in the FAA's
assessment, Work Package 2 (which specifies the same substantive
requirements in both the original issue and Revision 1 of Boeing Alert
Service Bulletin MD11-78A017) is appropriate and necessary to
understand and eliminate the root cause of the event, and the cost of
any additional ``significant resources'' necessary to accomplish those
actions would be outweighed by the safety benefits of the AD. This AD
has not been changed regarding this request.
---------------------------------------------------------------------------
\1\ The words ``ground'' and ``shield'' may be used
interchangeably in Boeing's documents.
---------------------------------------------------------------------------
Request To Remove the Inspection Requirement for the Junction Box
Assembly in Work Package 2
FedEx requested that the FAA remove the inspection requirement for
the junction box assembly included in Work Package 2 in Boeing Alert
Service Bulletin MD11-78A017, dated December 4, 2023. FedEx stated that
no chafed or burnt wires were found inside the junction box assembly of
the event airplane or on numerous units examined as part of
investigations. FedEx stated that removal of the junction box assembly
for inspection will increase the risk of damage to the junction box
assembly and surrounding wire harnesses.
The FAA does not agree with the request. Although the event
airplane did not reveal any evidence directly linked to the PRSOV and
DPV system wiring inside the junction box assembly, damage to those
wires inside the junction box assembly could result in the same outcome
encountered on the event airplane. The junction box assembly is a high-
density area of wire routing, where wires with power are routed with
the thrust reverser control wires. The inspection of the junction box
assembly is intended to detect and eliminate any riding condition of
wires since such condition could damage the thrust reverser control
wires. The FAA does not have any data regarding the other units
investigated. These units are subject to the same unsafe condition
because of their similar design and installation. This AD has not been
changed regarding this request.
Request To Remove the Required Actions on Engine 2
FedEx requested that the required actions on engine 2 (tail-mounted
engine) be removed from the proposed AD. The commenter stated that in-
flight deployment of a thrust reverser of engine 2 will have
considerably less impact on controllability of the airplane than the
wing-mounted engine 1 and engine 3. The commenter stated that wiring
running through the wings and attaching structures are far more exposed
to vibration and variable loading than those in the more stable tail
structure. Because of the less harsh operating environment for engine
2, combined with the historical reliability and a lack of wire damage
findings in the tail thrust reverser, FedEx concluded that the required
actions on the engine are not justified.
The FAA does not agree with the request. As discussed earlier,
Model MD-11 airplanes have not been demonstrated for their
controllability when the deployment of single or dual thrust reverser
halves is encountered on any single engine at low altitudes under
anticipated operating conditions. Therefore, prevention of in-flight
thrust reverser deployment is as critical for the tail-mounted engines
as the wing-mounted engines. Also, routing of wire harnesses is not the
same for the tail-mounted engines and wing-mounted engines as the wire
routing is restricted by available space. Vibration is a factor that
could contribute to wire chafing damage, but that is not the only
factor. Available gaps between wire harnesses and surrounding structure
as well as the types of wire support could also contribute to wire
chafing damage. Therefore, an inspection of all engines, including
engine 2, is critical and necessary. This AD has not been changed
regarding this request.
Concern for Economic Impact
FedEx stated that the FAA considerably underestimated the economic
impact to operators. FedEx claimed that the estimated costs in the NPRM
completely ignored the expense of acquiring contingency material. Even
if the inspections do not identify any out-of-limit conditions,
operators must still be prepared for the eventuality of findings to
prevent the possibility of extended grounding of airplanes. Preliminary
attempts to acquire necessary spare materials have revealed little or
no global supply. Boeing has not provided firm timelines for making
spare materials available and pricing for this commitment. FedEx
concluded that, because pricing has not been provided, it has not been
correctly incorporated in the cost estimate of the NPRM.
The FAA acknowledges FedEx's concern but does not agree with the
request. As explained in the NPRM, the FAA did not receive definitive
data that would enable the FAA to provide a labor and parts cost
estimate for the on-condition repairs or replacements. With regards to
necessary parts, the manufacturer has been addressing this issue, and
the FAA has concluded that the necessary spare materials would be
available. To the extent spare parts may not exist to replace parts
that fail the inspection requirements of this AD, the FAA cannot base
its AD action on whether spare parts are available or can be produced.
While every effort is made
[[Page 97487]]
to avoid grounding aircraft, the FAA must address the unsafe condition.
However, if parts availability becomes a problem during compliance with
the AD requirements, operators may request approval of an extension of
the compliance time as an alternative method of compliance (AMOC) in
accordance with the procedures specified in paragraph (k) of this AD,
if the operator submits sufficient data to substantiate that an
acceptable level of safety would be provided with such an extension.
This AD has not been changed regarding this request.
Request for More Economical Solution
One individual requested that the FAA consider alternatives that
could reduce the operational/economic burden on operators.
The commenter did not propose any alternative approach to
addressing the unsafe condition. In developing the most appropriate
solution, the FAA considered the recommendations of the manufacturer,
the urgency associated with the unsafe condition, the availability of
required parts, and the practical aspect of accomplishing the required
actions within a period of time that corresponds to the normal
scheduled maintenance for most affected operators. The FAA has
determined that the cost to operators to comply with this AD, as
proposed, is outweighed by the safety benefits.
Requests To Change Parts Necessary for Each Airplane Section in Service
Bulletin
FedEx requested revision of the parts necessary for each airplane
section in Boeing Alert Service Bulletin MD11-78A017, dated December 4,
2023, to make it workable. The commenter stated that the information
provided in Boeing Alert Service Bulletin MD11-78A017, dated December
4, 2023, regarding parts necessary for each airplane is incomplete and
insufficient for operators to effectively plan for the execution of the
service bulletin requirements. The commenter stated that determining
part numbers necessary for accomplishing the required action by
researching Boeing documents should not fall under the operator's
responsibility. The service bulletin provides an option of repair, but
it will still require identification and availability of specific wire
and related electrical components. The commenter stated that all part
numbers of potentially affected assemblies and components would need to
be identified in the service bulletin, or the materials necessary for
repair would need to be available for procurement.
Similarly, UPS requested a comprehensive parts list in Boeing Alert
Service Bulletin MD11-78A017, dated December 4, 2023, as well as a
source of suitable available spares, prior to the implementation of the
AD. UPS added that the components such as wiring and connectors are out
of production, and available parts are limited. UPS requested that the
AD be delayed until a suitable parts list and spare source are
determined.
The FAA does not agree with the requests. Regarding the parts
information provided in the service bulletin, the manufacturer
anticipated that new replacement parts for full wire harnesses or
junction box assemblies would not be available from suppliers.
Therefore, a repair would be the only available option to address
damaged or failed parts, unless serviceable parts removed from an
airplane are installed as replacement parts for an affected airplane.
As stated previously, if parts availability becomes a problem during
compliance with the AD requirements, an operator may request approval
of an extension of the compliance time as an AMOC in accordance with
the procedures specified in paragraph (k) of this AD, if the operator
submits sufficient data to substantiate that an acceptable level of
safety would be provided with such an extension. The intent of the
service bulletin was to provide sufficient information necessary to
accomplish required actions instead of providing full details of all
parts since providing such information for all wiring configurations
would require a substantial amount of time for this urgent issue and
may further complicate the service bulletin. Based on the information
provided in the service bulletin and available documents, such as
wiring diagrams, the illustrated parts catalog, and drawings, the
operators should be able to determine the necessary parts for repairs.
The manufacturer confirmed that they would support operators to confirm
the necessary parts for accomplishing the required actions. This AD has
not been changed regarding this request.
Request To Add an Instruction for a Condition With Multiple Options
FedEx requested that an instruction be added in the AD regarding
how a required condition should be handled when the condition provides
multiple options. The commenter stated that instructions identified as
required for compliance (RC) are also identified as an option that is
contingent on certain conditions being met and a choice being made by
the operator. The commenter expressed a concern that if this is not
directly addressed in the language of the AD, it is anticipated that
these RC options will be difficult to deal with when maintenance work
cards are generated, putting the technicians in the position of making
a choice to sign off an AD-required step as not applicable for the
option not taken.
The FAA does not agree with the comment. In addition to Section
1.E., Compliance, of Boeing Alert Service Bulletin MD11-78A017, dated
December 4, 2023, or Revision 1, dated June 4, 2024, Note 13 in Section
3.A. of the service bulletin provides the instruction on how to handle
a required condition when multiple options are provided under that
condition. This instruction provided by a general note has been used in
numerous service bulletins and is not unique to this specific service
bulletin. Therefore, it is unnecessary to repeat this instruction in
the AD. No further changes have been made to this AD regarding this
request.
Request To Provide Instructions for Insulation Resistance Test
FedEx stated that Boeing Alert Service Bulletin MD11-78A017, dated
December 4, 2023, does not provide sufficient detail to ensure that
wire harness insulation resistance checks in Parts 6 through 8 in the
service bulletin are performed properly. The commenter recommended
including a statement that each of the checks should be measured
against ground. The commenter also stated that unless precautionary or
explanatory statements are included to indicate application of 500V
between the pins and each of the other contacts on the same connector
may damage other components on the circuit, uncertainty around
validating the test may result.
The FAA does not agree with the request. The insulation resistance
check is a standard practice. The operators are expected to follow
applicable instructions in the standard wiring practice manual to
perform the test for the connectors specified in the service bulletin.
The test requirement is to measure between every pin and ground
(shielding) and between all two adjacent pins. This AD has not been
changed regarding this request.
Request for Additional Details in Part 19 in the Service Bulletin
FedEx stated that the instructions for Part 19 in Boeing Alert
Service Bulletin MD11-78A017, dated December 4, 2023, are too vague
since the specific connectors and pins are not identified. FedEx added
that Boeing does not have adequate data to specify the detail since the
harnesses to be tested are not
[[Page 97488]]
controlled by Boeing. This lack of detail places the burden onto the
operators to ensure that the tests are performed as intended. The
commenter does not believe the instructions in the service bulletin are
adequate to ensure successful compliance.
The FAA does not agree with the request. As the commenter stated,
the manufacturer does not have the details of the pins or connectors,
as the data for the wire harnesses is not controlled by Boeing.
Further, due to the urgency of the unsafe condition, the FAA cannot
delay issuance of this final rule further for Boeing to identify the
connectors or pins. This will place the burden on the operators, but
the operators should utilize available data and ensure that the tests
are performed adequately based on input provided by the manufacturer.
This AD has not been changed regarding this request.
Request To Revise the Work Instructions for Part 13 in the Service
Bulletin
FedEx requested revision of the work instructions in Part 13 of
Boeing Alert Service Bulletin MD11-78A017, dated December 4, 2023,
which requires an inspection of the internal surface of the junction
box cover per Figure 13 for burn marks, signs of arcing, and fretting.
The commenter stated that many inspected junction boxes' covers
exhibited smudges and discoloration that can be misinterpreted as soot
and burn residual, rather than the dust from the harness lacings
rubbing against the cover. The instructions as currently written may
result in many false findings. The commenter requested that a note be
added to the service bulletin to call attention to the possibility of
the benign discoloration and allow for the presence of such residue.
The FAA partially agrees with the request. The FAA agrees that the
work instructions in Part 13 of Boeing Alert Service Bulletin MD11-
78A017, dated December 4, 2023, may result in false findings. However,
this AD will require Revision 1 of the service bulletin. The work
instructions in Part 13 of Boeing Alert Service Bulletin MD11-78A017,
Revision 1, dated June 4, 2024, have been updated to eliminate the
potential misinterpretation of the conditions found on the junction box
cover during the inspection. No change to this AD has been made as a
result of this comment.
Request To Revise Figures 14 and 15 in the Service Bulletin
FedEx requested that Figures 14 and 15 of Boeing Alert Service
Bulletin MD11-78A017, dated December 4, 2023, be revised to remove the
minimum clearance requirement between the wire harnesses and the
junction box cover or to add a clarification stating that contact
between the junction box cover and lacing material is acceptable. In
the alternative, FedEx asked that the language of the proposed AD be
revised to add an exemption to the minimum clearance requirement in
paragraph (h) of the proposed AD. The commenter noted that Parts 14 and
15 of the service bulletin require a minimum clearance of 0.20 inch
between the junction box cover and the wire bundles inside the junction
box assembly. However, there is no instruction to confirm that this
minimum clearance is maintained when the junction box cover is closed.
The commenter stated that the wire harnesses inside the junction box
assembly are very stiff and rigid and generally cannot be appreciably
compacted. Although this condition may result in minor interference of
the lacings with the cover, the commenter has not found any evidence of
wire damage resulting from this contact.
The FAA partially agrees with the request. The FAA agrees that the
instructions to achieve the required minimum clearance were unclear in
Boeing Alert Service Bulletin MD11-78A017, dated December 4, 2023. The
work instructions have been revised in Boeing Alert Service Bulletin
MD11-78A017, Revision 1, dated June 4, 2024, for clarification.
However, Boeing Alert Service Bulletin MD11-78A017, dated December 4,
2023, or Revision 1, dated June 4, 2024, does not allow contact between
the junction box cover and lacing material since such a condition may
eventually result in wire damage. No change has been made to this AD as
a result of this comment.
Request To Correct Typographical Errors
FedEx noted multiple errors and typographical errors in Boeing
Alert Service Bulletin MD11-78A017, dated December 4, 2023, and
requested revision of the service bulletin to correct these errors and
typographical errors.
The errors and typographical errors identified by the commenter
have been corrected in Boeing Alert Service Bulletin MD11-78A017,
Revision 1, dated June 4, 2024, which is the primary source of service
information in this AD. No change has been made to this AD as a result
of this comment.
Request To Revise the Compliance Time of the Reporting Requirement
FedEx requested revision of the compliance time of the reporting
requirement in paragraph (i) of the proposed AD. The commenter stated
that the proposed compliance time of 30 days is inadequate to prepare
the data package and submit the reports. The commenter stated they do
not understand the urgency of the reporting requirement considering the
overall compliance span of the AD.
The FAA agrees that the proposed compliance time of 30 days for the
reporting requirement is unnecessarily short considering the burden on
the operators and the intent that those reports will be used for root
cause assessment while managing the potential risk by the inspections.
The FAA has revised the compliance time of paragraph (i) of this AD to
90 days accordingly.
Request To Change Reporting Requirements
FedEx requested that the FAA eliminate the reporting requirement of
paragraph (i) of the proposed AD or revise the requirements to clarify
what must be reported to meet the compliance criteria. The commenter
was concerned that the reporting criteria in the service bulletin are
open-ended and could be misinterpreted as to what qualifies as
reportable and what level of detail is required. The commenter stated
that because of the breadth of the reporting criteria involved, it
would be extremely hard to definitively comply with the reporting
requirement. Also, the commenter stated that the relationship between
Boeing and the operators should be sufficient to ensure that findings
will be provided to Boeing without a mandatory reporting requirement.
The FAA partially agrees with the request.
The FAA agrees to revise the reporting criteria for clarification
so that the results of the inspections or tests are reported in a
consistent manner. The reporting form in Appendix C of the original
service bulletin was updated in Boeing Alert Service Bulletin MD11-
78A017, Revision 1, dated June 4, 2024. The updated reporting forms in
Appendixes C through E of Boeing Alert Service Bulletin MD11-78A017,
Revision 1, dated June 4, 2024, provide clear instructions to address
the concern expressed by the commenter.
The FAA disagrees, however, with the request to remove the
reporting requirement in paragraph (i) of this AD. The findings
provided by the reports will be used for the root cause assessment and
the development of a final corrective action. Therefore, the reporting
requirement is a critical piece of this interim action AD.
[[Page 97489]]
Request To Use Boeing Service Bulletin as an Optional Inspection
UPS requested that the actions specified in Boeing Alert Service
Bulletin MD11-78A017, dated December 4, 2023, remain as an optional
inspection until the root cause can be determined.
The FAA does not agree with the request. As discussed in the
preamble of the NPRM, wiring damage was found in the engine pylon of
the event airplane. The root cause of uncommanded thrust reverser
deployment has not been determined yet, but the manufacturer concluded
that wiring damage was a contributing factor of the event based on the
assessment of on-wing data and laboratory inspection. The FAA considers
this AD to be an interim action. The FAA issues an interim action AD
when, for example, an unsafe condition that requires a mitigating
action relatively quickly is identified on airplanes, but the root
cause leading to the unsafe condition is still undetermined due to
limited available data. In this case, the interim mitigating action is
needed to address the overall risk of the unsafe condition. Based on
the FAA's assessment, the actions required by this AD would mitigate
the unsafe condition in the interim period while additional inspection
data would allow the manufacturer to determine the root cause and
develop an adequate corrective action. This AD has not been changed
regarding this request.
Request To Delay Issuance of Final Rule
UPS requested that the effective date of the AD be extended until
Boeing Alert Service Bulletin MD11-78A017 is revised. UPS stated that
Boeing Alert Service Bulletin MD11-78A017, dated December 4, 2023,
identified in the NPRM is unworkable due to discrepancies and
disagreements between the configurations specified in the instructions
and the actual installation.
Because this AD has been changed to mandate Boeing Alert Service
Bulletin MD11-78A017, Revision 1, dated June 4, 2024, which clarifies
these instructions, no further change is necessary to this AD as a
result of this comment. The manufacturer also worked with the operators
to ensure that the work instructions in Revision 1 can be accomplished.
This AD has not been changed regarding this request.
Request To Extend the Compliance Time for Work Package 1 and Increase
Labor Hours
UPS requested that the FAA revise paragraph (h) of the proposed AD
to extend the compliance time of Work Package 1 of Boeing Alert Service
Bulletin MD11-78A017, dated December 4, 2023, to 27 months from the
current proposal of 12 months. UPS stated that the labor estimate
provided in the service bulletin underestimates the tasks involved in
Work Package 1. UPS estimated that about 700 work-hours would be
involved, while Boeing Alert Service Bulletin MD11-78A017, dated
December 4, 2023, estimated 134.25 hours. Considering extensive work-
hours and limited parts availability, UPS stated that the proposed
compliance time of 12 months does not provide sufficient time to
accomplish the required actions for the affected fleet.
The FAA does not agree with the request. The FAA infers that the
labor estimates provided by UPS include the labor necessary for
repairs. The labor estimates provided in the service bulletin do not
include the labor necessary for repairs since a repair is an on-
condition action that would be affected by the extent of the damage
discovered on the affected parts. The FAA recognizes that a gap would
exist between the estimates provided in the service bulletin and the
actual labor needed for each airplane because of those on-condition
actions. The FAA established the compliance time so that operators can
accomplish this interim mitigation action in a quick and practical
manner, considering the potential effect of the unsafe condition. The
FAA also assessed parts availability and necessary labor and determined
that the compliance time of 12 months would be appropriate for Work
Package 1. Operators can request approval of an extension of the
compliance time in accordance with paragraph (k) of this AD if
operators can provide the evidence that would make the required
compliance time impractical and justification for maintaining an
acceptable level safety with such an extension. This AD has not been
changed regarding these requests.
Request To Include Spare Engines and Thrust Reversers in Applicability
UPS requested that paragraph (c) of the proposed AD be revised to
include spare engines and thrust reversers in the AD applicability.
Although Boeing Alert Service Bulletin MD11-78A017, dated December 4,
2023, requires inspections and repair of the components for the engines
and thrust reversers, an engine or thrust reverser on which the actions
of Boeing Alert Service Bulletin MD11-78A017, dated December 4, 2023,
were accomplished may be replaced with an engine or thrust reverser on
which the actions specified in Boeing Alert Service Bulletin MD11-
78A017, dated December 4, 2023, have not been accomplished.
The FAA disagrees with the request. The FAA understands the concern
of an AD-compliant engine or thrust reverser being inadvertently
replaced with a non-AD-compliant engine or thrust reverser. However,
the AD is issued to address the unsafe condition identified at the
airplane level. The affected airplanes must be maintained in the AD-
compliant configuration once each airplane is demonstrated to be
compliant with the AD. Installing an engine or thrust reverser that has
not been inspected or tested as required by this AD on an airplane that
was demonstrated to be compliant with the AD is not allowed since such
an action will bring the airplane back to a non-AD-compliant
configuration, unless the engine or thrust reverser is inspected or
tested as required by the AD prior to returning the airplane back to
service. It is the operator's responsibility to maintain each airplane
in the AD-compliant configuration. This AD has not been changed
regarding this request.
Request for a Specific Interval Inspection
An individual commenter recommended that the FAA analyze the
frequency of the occurrence of uncommanded thrust reverser deployment
in air and determine a specific interval for this inspection.
Although the FAA agrees with the intent behind this request, it is
not necessary to change the AD based on this request. The FAA already
assessed the aspect the commenter raised. The FAA has assessed the risk
of in-flight thrust reverser deployment, considering the frequency of
occurrence based on available data, and determined that the compliance
times for the initial and repetitive inspections are adequate. As
discussed in the preamble of the NPRM, the actions required by this AD
are considered an interim action. Additional data to be provided by the
operators through the reporting requirement of this AD will enable the
manufacturer to obtain better insight into the potential conditions
that led to the event. Based on the information provided by those
reports, the FAA may consider further rulemaking.
Conclusion
The FAA reviewed the relevant data, considered any comments
received, and determined that air safety requires adopting this AD as
proposed. Accordingly, the FAA is issuing this AD to address the unsafe
condition on these
[[Page 97490]]
products. Except for minor editorial changes, and any other changes
described previously, this AD is adopted as proposed in the NPRM. None
of the changes will increase the economic burden on any operator.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed Boeing Alert Service Bulletin MD11-78A017,
Revision 1, dated June 4, 2024. This material specifies Work Package 1
inspection procedures to do an initial detailed inspection of the
engine 1, engine 2, and engine 3 pylon thrust reverser control system
wire harnesses. The material also specifies Work Package 2 procedures
to do repetitive detailed inspections and wire integrity tests at the
following locations: engine 1, engine 2, and engine 3 thrust reverser
control system wire harnesses; junction box assembly and junction box
cover (only detailed inspection); left side and right side thrust
reverser electrical harnesses; core (engine compartment) miscellaneous
wire harness assembly; and 30-degree bulkhead wire harness assembly.
The material also specifies applicable on-condition actions (including
repairs, replacements, installations, post-replacement inspections and
tests, and return to service tests). The material also specifies that
accomplishing the initial inspections and tests by doing Action 1
through Action 3 in Work Package 2 terminates the need to do the
inspection in accordance with Part 2 as required in Work Package 1.
However, this substitution of actions does not change the compliance
time of Work Package 1 as specified in Table 1 of paragraph 1.E.,
``Compliance,'' of Boeing Alert Service Bulletin MD11-78A017, Revision
1, dated June 4, 2024.
This material is reasonably available because the interested
parties have access to it through their normal course of business or by
the means identified in the ADDRESSES section.
Interim Action
The FAA considers this AD to be an interim action. The reports that
are required by this AD will enable the manufacturer to obtain better
insight into the nature, cause, and extent of the unsafe condition, and
eventually to develop final action to address the unsafe condition. If
final action is later identified, the FAA might consider further
rulemaking.
Costs of Compliance
The FAA estimates that this AD affects 79 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this AD:
Estimated Costs
----------------------------------------------------------------------------------------------------------------
Parts Cost on U.S.
Action Labor cost cost Cost per product operators
----------------------------------------------------------------------------------------------------------------
Inspections and Tests............. Up to 78 work-hours x $0 Up to $6,630 per Up to $523,770 per
$85 per hour = Up to inspection/test inspection/test
$6,630 per cycle. cycle.
inspection/test
cycle.
Reporting......................... 1 work-hour x $85 per 0 $85 per inspection/ $6,715 per
hour = $85 per test cycle. inspection/test
inspection/test cycle.
cycle.
----------------------------------------------------------------------------------------------------------------
The FAA estimates the following costs to do any on-condition
actions that would be required based on the results of the inspections
and tests. The agency has no way of determining the number of aircraft
that might need these repairs/replacements:
On-Condition Costs
----------------------------------------------------------------------------------------------------------------
Action Labor cost Parts cost Cost per product
----------------------------------------------------------------------------------------------------------------
Repairs/Replacements/Tests........... Up to 120 work-hours x * $0 Up to $10,200.
$85 per hour = Up to
$10,200.
----------------------------------------------------------------------------------------------------------------
* The FAA has received no definitive data that would enable the FAA to provide a parts cost estimate for the on-
condition repairs/replacements specified in this AD.
Paperwork Reduction Act
A federal agency may not conduct or sponsor, and a person is not
required to respond to, nor shall a person be subject to a penalty for
failure to comply with a collection of information subject to the
requirements of the Paperwork Reduction Act unless that collection of
information displays a currently valid OMB Control Number. The OMB
Control Number for this information collection is 2120-0056. Public
reporting for this collection of information is estimated to take
approximately 1 hour per response, including the time for reviewing
instructions, searching existing data sources, gathering and
maintaining the data needed, and completing and reviewing the
collection of information. All responses to this collection of
information are mandatory. Send comments regarding this burden estimate
or any other aspect of this collection of information, including
suggestions for reducing this burden to: Information Collection
Clearance Officer, Federal Aviation Administration, 10101 Hillwood
Parkway, Fort Worth, TX 76177-1524.
Authority for This Rulemaking
Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, section 106, describes the
authority of the FAA Administrator. Subtitle VII: Aviation Programs,
describes in more detail the scope of the Agency's authority.
The FAA is issuing this rulemaking under the authority described in
Subtitle VII, Part A, Subpart III, Section 44701: General requirements.
Under that section, Congress charges the FAA with promoting safe flight
of civil aircraft in air commerce by prescribing regulations for
practices, methods, and procedures the Administrator finds necessary
for safety in air commerce. This regulation is within the scope of that
authority because it addresses an unsafe condition that is likely to
exist or develop on products identified in this rulemaking action.
Regulatory Findings
This AD will not have federalism implications under Executive Order
13132. This AD will not have a
[[Page 97491]]
substantial direct effect 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.
For the reasons discussed above, I certify that this AD:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Will not affect intrastate aviation in Alaska, and
(3) 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.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.
The Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 14 CFR part 39 as follows:
PART 39--AIRWORTHINESS DIRECTIVES
0
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]
0
2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive:
2024-24-03 The Boeing Company:
Amendment 39-22893; Docket No. FAA-2023-2403; Project
Identifier AD-2023-00888-T.
(a) Effective Date
This airworthiness directive (AD) is effective January 13, 2025.
(b) Affected ADs
None.
(c) Applicability
This AD applies to The Boeing Company Model MD-11 and MD-11F
airplanes, certificated in any category, equipped with General
Electric (GE) CF6-80C2D1F high-bypass turbofan engines.
(d) Subject
Air Transport Association (ATA) of America Code 78, Engine
Exhaust.
(e) Unsafe Condition
This AD was prompted by a report of a Model MD-11F airplane
experiencing an uncommanded deployment of a thrust reverser at
approximately 500 feet above ground level. The FAA is issuing this
AD to address uncommanded deployment of a thrust reverser in-flight
at low altitude, which could result in loss of flight control of the
airplane and loss of continued safe flight and landing.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Required Actions
Except as specified in paragraph (h) of this AD: At the
applicable times specified in paragraph 1.E., ``Compliance,'' of
Boeing Alert Service Bulletin MD11-78A017, Revision 1, dated June 4,
2024, do all applicable actions identified as ``RC'' (required for
compliance) in, and in accordance with, the Accomplishment
Instructions of Boeing Alert Service Bulletin MD11-78A017, Revision
1, dated June 4, 2024.
(h) Exceptions to Service Bulletin Specifications
(1) Where the Compliance Time columns of the tables in the
``Compliance'' paragraph of Boeing Alert Service Bulletin MD11-
78A017, Revision 1, dated June 4, 2024, use the phrase ``the
original issue date of this service bulletin,'' this AD requires
using the effective date of this AD.
(2) Where Step 1, Part 10 of Boeing Alert Service Bulletin MD11-
78A017, Revision 1, dated June 4, 2024, specifies doing a detailed
inspection of the junction box assembly for any loose electrical
connection and Step 2, Part 11 of Boeing Alert Service Bulletin
MD11-78A017, Revision 1, dated June 4, 2024, specifies applying
applicable torque to any loose electrical connection, those actions
are not required for compliance with this AD.
(i) Reporting
At the applicable time specified in paragraph (i)(1) or (2) of
this AD, submit a report to The Boeing Company via the Boeing
Communication System (BCS) and include the information specified in
Appendixes C, D, and E of Boeing Alert Service Bulletin MD11-78A017,
Revision 1, dated June 4, 2024.
(1) If the inspection or test was done on or after the effective
date of this AD: Submit the report within 90 days after the
inspection or test.
(2) If the inspection or test was done before the effective date
of this AD: Submit the report within 90 days after the effective
date of this AD.
(j) Credit for Previous Actions
This paragraph provides credit for the actions specified in
paragraphs (g) and (i) of this AD, if those actions were performed
before the effective date of this AD using Boeing Alert Service
Bulletin MD11-78A017, dated December 4, 2023, except where step
6.c.(2)(a), ``CONDITON 14 OPTION 1 (ACTION 1),'' and step
6.c.(2)(b)4)d), ``CONDITION 14.4 OPTION 2 (ACTION 1),'' of the
Accomplishment Instructions of Boeing Service Bulletin MD11-78017,
dated December 4, 2023, specify to replace the junction box, that
replacement must be accomplished in accordance with ``PART 12:
JUNCTION BOX REPLACEMENT'' of the Accomplishment Instructions of
Boeing Service Bulletin MD11-78017, dated December 4, 2023.
(k) Alternative Methods of Compliance (AMOCs)
(1) The Manager, AIR-520, Continued Operational Safety Branch,
FAA, has the authority to approve AMOCs for this AD, if requested
using the procedures found in 14 CFR 39.19. In accordance with 14
CFR 39.19, send your request to your principal inspector or
responsible Flight Standards Office, as appropriate. If sending
information directly to the manager of AIR-520, Continued
Operational Safety Branch, send it to the attention of the person
identified in paragraph (l)(1) of this AD. Information may be
emailed to: [email protected].
(2) Before using any approved AMOC, notify your appropriate
principal inspector, or lacking a principal inspector, the manager
of the responsible Flight Standards Office.
(3) An AMOC that provides an acceptable level of safety may be
used for any repair, modification, or alteration required by this AD
if it is approved by The Boeing Company Organization Designation
Authorization (ODA) that has been authorized by the Manager, AIR-
520, Continued Operational Safety Branch, FAA, to make those
findings. To be approved, the repair method, modification deviation,
or alteration deviation must meet the certification basis of the
airplane, and the approval must specifically refer to this AD.
(4) Except as specified by paragraph (h)(2) of this AD: For
Boeing service bulletin that contains steps that are labeled as
Required for Compliance (RC), the provisions of paragraphs (k)(4)(i)
and (ii) of this AD apply.
(i) The steps labeled as RC, including substeps under an RC step
and any figures identified in an RC step, must be done to comply
with the AD. If a step or substep is labeled ``RC Exempt,'' then the
RC requirement is removed from that step or substep. An AMOC is
required for any deviations to RC steps, including substeps and
identified figures.
(ii) Steps not labeled as RC may be deviated from using accepted
methods in accordance with the operator's maintenance or inspection
program without obtaining approval of an AMOC, provided the RC
steps, including substeps and identified figures, can still be done
as specified, and the airplane can be put back in an airworthy
condition.
(l) Related Information
(1) For more information about this AD, contact Tak Kobayashi,
Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA
98198; telephone 206-231-3553; email [email protected].
(2) Material identified in this AD that is not incorporated by
reference is available at the address specified in paragraph (m)(3)
of this AD.
(m) Material Incorporated by Reference
(1) The Director of the Federal Register approved the
incorporation by reference of the material listed in this paragraph
under 5 U.S.C. 552(a) and 1 CFR part 51.
(2) You must use this material as applicable to do the actions
required by this AD, unless the AD specifies otherwise.
[[Page 97492]]
(i) Boeing Alert Service Bulletin MD11-78A017, Revision 1, dated
June 4, 2024.
(ii) [Reserved]
(3) For Boeing material identified in this AD, contact Boeing
Commercial Airplanes, Attention: Contractual & Data Services (C&DS),
2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600;
telephone 562-797-1717; website myboeingfleet.com.
(4) You may view this material at the FAA, Airworthiness
Products Section, Operational Safety Branch, 2200 South 216th St.,
Des Moines, WA. For information on the availability of this material
at the FAA, call 206-231-3195.
(5) You may view this material at the National Archives and
Records Administration (NARA). For information on the availability
of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected].
Issued on November 19, 2024.
Peter A. White,
Deputy Director, Integrated Certificate Management Division, Aircraft
Certification Service.
[FR Doc. 2024-28780 Filed 12-6-24; 8:45 am]
BILLING CODE 4910-13-P