[Federal Register: January 23, 2008 (Volume 73, Number 15)]
[Rules and Regulations]
[Page 3863-3867]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr23ja08-2]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2006-25609; Directorate Identifier 2005-NM-263-AD;
Amendment 39-15335; AD 2008-02-05]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 777-200 and -300 Series
Airplanes Equipped With Rolls-Royce RB211-TRENT 800 Series Engines
AGENCY: Federal Aviation Administration (FAA), Department of
Transportation (DOT).
ACTION: Final rule.
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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain Boeing Model 777-200 and -300 series airplanes. This AD
requires revising the airplane flight manual to provide the
[[Page 3864]]
flightcrew with new ground procedures for shedding core ice during long
taxi periods in freezing fog with visibility of 300 meters or less. For
airplanes unable to perform the shedding procedure after prolonged
taxiing in freezing fog with visibility of 300 meters or less, this AD
requires certain investigative and corrective actions. This AD results
from reports of engine surges and internal engine damage due to ice
accumulation during extended idle thrust operation in ground fog icing
conditions. We are issuing this AD to prevent internal engine damage
due to ice accumulation and shedding, which could cause a shutdown of
both engines, and result in a forced landing of the airplane.
DATES: This AD becomes effective February 27, 2008.
ADDRESSES: For service information identified in this AD, contact
Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-
2207.
Examining the AD Docket
You may examine the AD docket on the Internet at http://www.regulations.gov
; or in person at the Docket Management Facility
between 9 a.m. and 5 p.m., Monday through Friday, except Federal
holidays. The AD docket contains this AD, the regulatory evaluation,
any comments received, and other information. The address for the
Docket Office (telephone 800-647-5527) is the Document Management
Facility, U.S. Department of Transportation, Docket Operations, M-30,
West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE.,
Washington, DC 20590.
FOR FURTHER INFORMATION CONTACT: Margaret Langsted, Aerospace Engineer,
Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification
Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone
(425) 917-6500; fax (425) 917-6590.
SUPPLEMENTARY INFORMATION:
Discussion
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 to include an AD that would apply to certain Boeing Model
777-200 and -300 series airplanes. That NPRM was published in the
Federal Register on August 18, 2006 (71 FR 47754). That NPRM proposed
to require revising the airplane flight manual to provide the
flightcrew with new ground procedures for shedding core ice during long
taxi periods in freezing fog. For airplanes unable to perform the
shedding procedure after prolonged taxiing in freezing fog, that NPRM
proposed to require certain investigative and corrective actions.
Comments
We provided the public the opportunity to participate in the
development of this AD. We have considered the comments received.
Requests To Reduce Visibility Requirements
Boeing, Rolls-Royce, the European Aviation Safety Agency (EASA),
and Air Transport Association (ATA), on behalf of American Airlines,
all request that we reduce the visibility requirements during a ground
fog icing encounter. The commenters request that the current 1,000-
meter or less visibility requirements be reduced to 300-meters or less
visibility. Rolls-Royce has performed an analysis based on atmospheric
data and service experience that demonstrates that freezing fog
presents a threat to the engine only when the visibility drops below
300 meters; EASA has accepted this analysis. Boeing states that this
change will minimize the need for the run-up to only those freezing fog
conditions that are severe enough to pose a risk.
We agree with the commenters. Sufficient data have been presented
to the FAA to justify a reduction from the 1,000-meter visibility
requirement to a 300-meter visibility requirement. We have revised the
statement in the Summary section, and paragraphs (f), (h) and (i) of
the final rule to state ``in freezing fog with visibility of 300 meters
or less.''
Requests To Remove Specific Airplane Maintenance Manual (AMM) Task
References, and To Refer to Current Procedures
Boeing, Rolls-Royce, and ATA, on behalf of its members Delta
Airlines and American Airlines, request that we refer to the Boeing 777
AMM for the de-icing procedures, rather than specific changes in the
AMM. Rolls-Royce points out that the specified tasks are only examples
of an acceptable inspection method; referring to a specific task/issue
of the AMM in an AD will lead to many requests for alternative methods
of compliance (AMOCs) from operators after AMM revisions. ATA states
that the specific tasks do not exist in the AMM available to one of its
members.
In addition, Boeing, Rolls-Royce, and American Airlines state that
the AMM procedures for doing the engine core de-icing (referred to in
paragraph (h) of the NPRM) are outdated. The commenters explain that
Rolls-Royce and Boeing did testing to determine the best way to conduct
the procedure, and that the best solution is included in the latest AMM
procedure. The commenters state that this is another example of why we
should not refer to specific AMM tasks in the AD.
For the stated reasons, we agree with the commenters that we should
refer to the Boeing 777 AMM, rather than specific tasks. Therefore, we
have changed paragraphs (h) and (h)(2) of the AD to specify that
Chapter 12-33-03 of the Boeing 777 AMM, rather than the specific tasks,
provides acceptable methods of compliance. We also added a statement to
paragraph (h)(2) of this AD indicating that the temperature of the air
supplied cannot exceed 176 degrees Fahrenheit at any time during the
manual de-ice process. Air that exceeds 176 degrees Fahrenheit can
damage the engine.
Requests To Clarify Borescope Inspection Requirements
Boeing and Rolls-Royce request that we clarify and revise the
requirements for the borescope inspection, and that we specify
inspecting the intermediate pressure compressor (IPC) blades unless
damage indicates that material has been released. The commenters state
that inspection of other compressor stages would be necessary if the
material has been released. Rolls-Royce explains that if no material
has been released from the IPC stage 1 blades then there will be no
secondary damage to the high pressure compressor (HPC), so inspection
is not required. If material is missing from the IPC stage 1, the
engine must have a full borescope inspection of both the IPC and the
HPC. Damage to the IPC stage 1 blades without material release would be
treated under the current AMM acceptance limits. Boeing and Rolls-Royce
state that the borescope procedure to look for damage is conducted
routinely by the airlines, and that it is not necessary to mandate the
current borescoping method in the AMM.
We agree with the requests to clarify the borescope inspection
procedures. The risk of engine failure is a direct result of HPC
damage; if there is no material released from the IPC stage 1 blades,
then there will be no resulting damage to the HPC. We have revised
paragraph (i) of the AD to clarify the borescope procedures and to
specify that Chapter 72-00-00 of the Boeing 777 AMM is one approved
method for complying with the requirements of that paragraph. We
acknowledge that the borescope procedure is conducted routinely by the
airlines; however, an AD must specify a method of compliance for all
required actions and, in cases where there is no relevant
[[Page 3865]]
service bulletin as with this AD, we generally point to the AMM as an
acceptable method of compliance.
Request To Place Core Ice Shedding Procedures in Operations Manual
Vincent Crow, a private citizen, would like to have the core ice
shedding procedures (described in paragraph (f) of the NPRM) as a part
of Operations Manual Volume 1 (OMV1) as a supplementary procedure in
the adverse weather section. Paragraph (f) of the NPRM specifies
publishing these procedures in the Airplane Flight Manual (AFM) as a
certification limitation.
We disagree with the request to publish the procedures in OMV1.
OMV1 is not approved or mandated by the FAA. The AFM limitations are
approved and mandated by the FAA. In addition, all limitations in the
AFM are required to be incorporated into the operations manual. We have
not changed the AD in this regard.
Requests To Withdraw NPRM
Boeing, and ATA, on behalf of its member American Airlines, state
that the NPRM is unnecessary because the freezing fog procedure
(paragraph (f) of the NPRM) is already included in the FAA-approved AFM
Limitations section.
We infer that the commenters would like us to withdraw the NPRM. We
do not agree. Although the AFM has been revised to reflect the proposed
requirements in the NPRM, the operators are not required to adopt the
latest revision of the AFM. Therefore, the procedures in paragraph (f)
of the NPRM would not be required unless we take AD action. We have not
changed the AD in this regard.
Request To Address Risk of Sliding When Power Is Advanced
The National Transportation Safety Board (NTSB) is concerned that
the environmental conditions that cause the engine core icing could
also cause the taxiway surface to become icy and slippery, thereby
increasing the risk of the airplane sliding off the taxiway or into
another airplane when the crew advances the power to shed the core ice.
We infer that the NTSB would like us to add procedures to the AD to
require actions that do not involve advancing engine power. We disagree
that the procedures will result in the airplane sliding. The procedures
mandated by the AD were developed with a reduced thrust setting to
minimize the potential for sliding. Based on discussions with
operators, we understand that the pilot will locate the airplane in a
safe place to do the run-ups. We have addressed the possibility of the
pilot not being able to perform the engine run-up by allowing operators
to manually de-ice before takeoff, or to take off with the subsequent
requirement of a borescope inspection. We have not changed the AD in
this regard.
Request To Redesign the Engine
The NTSB suggests that, in the long term, the FAA require that
engines be modified so that the airfoil surfaces where ice is building
up are heated to prevent the buildup. The NTSB notes that early-
generation gas turbine engines had inlet guide vanes that were
pneumatically heated to prevent the formation of ice. The NTSB goes on
to say that several safety recommendations have been issued concerning
ice buildup on the stationary parts of the engine, causing engine core
damage when shed.
We disagree with the suggestion to require modification to the
engines to prevent ice buildup during extended exposure to ground fog
icing. The Trent 800 series engine would require extensive testing and
redesign to add additional anti-ice capability. History has shown that
the frequency of ground icing encounters are rare and it would not be
cost effective to redesign the engine given that there are operational
procedures that adequately address the unsafe condition. The NTSB
refers to safety recommendations that were issued as a result of dual
engine high-altitude flameouts from ice buildup on the engine core.
While extended exposure to ground fog icing does cause ice buildup in
the engine core, the requirement of periodic engine speed run-ups is
consistent with other ground-based icing operational procedures. We
have not changed the AD in this regard.
Request To Include Costs of Run-Up, Manual De-Ice, and Borescope
Boeing requests that we include the cost of disruption to the
airline when a run-up, manual de-ice, or borescope inspection is
needed. Boeing points out that the AD mandates the procedure, and if
the operator conducts the procedure it will require delay, and possibly
maintenance action.
We disagree with the request to include these costs in the Costs of
Compliance section. We recognize that this AD may impose certain
additional operational costs. However, we cannot calculate those costs
because we do not know how often the conditions occur and what
additional time is necessary. Continued operational safety necessitates
the imposition of these costs because of the severity of the unsafe
condition. In addition, the cost analysis in AD actions typically does
not include incidental costs such as the time required to gain access
and close up, time necessary for planning, or time necessitated by
other administrative actions. Those incidental costs, which might vary
significantly among operators, are almost impossible to calculate. We
have not changed the AD in this regard.
Requests To Provide Terminating Action
Boeing and Rolls-Royce request that we provide a clear terminating
action for the actions proposed in the NPRM. Boeing states that the AD
should be considered complied with and closed once the procedure to
perform the engine run-up is inserted in the AFM. Boeing points out
that the engine procedures for inspecting for ice and manually de-icing
should be part of the airlines' approved de-ice/anti-ice procedures,
and like the wing de-ice procedures, the methods to accomplish them are
not mandated by AD. Boeing and Rolls-Royce both suggest adding
information to paragraph (g) of the NPRM that would specify that, once
the procedures are incorporated into the operator's approved ground de-
icing/anti-icing program, the AD should be considered complied with.
We disagree with the need to add terminating action to paragraph
(g) of the AD. The Limitations section in the AFM includes maintenance
actions that are not performed by the flightcrew and cannot be required
without an AD. As discussed above, Boeing and Rolls-Royce do not plan
to make an engine or airplane configuration change that would eliminate
the need for the AFM and maintenance procedures mandated by this AD,
and thus provide terminating action. We have not changed the AD in this
regard.
Requests To Specify Lack of Events With Trent 800
Boeing and Rolls-Royce ask that we clarify the summary and
paragraph (d) of the NPRM to specify that Trent 800 series engines (the
subject of the proposed AD) have not experienced engine surges and
internal engine damage due to ice accumulation during extended idle
thrust operation in ground fog icing conditions.
We acknowledge that Trent 800 series engines have not experienced
the stated events, as described in the ``Discussion'' and ``Similar
Engine Models'' sections of the NPRM. As stated in the preamble of the
NPRM, both the Trent 700 series engines and the Trent 800 series
engines have a similar compressor design, and
[[Page 3866]]
therefore may be subject to the same unsafe condition. We find that
this information need not be added to the AD Summary section, or to any
regulatory paragraphs of the AD.
Request To Clarify Paragraphs (f) and (h) of the NPRM
EASA requests that we clarify the wording of the AFM revision by
revising the phrase ``there is no run-up procedure'' in paragraph (f)
(sub-paragraph (c) of the AFM revision) of the NPRM to state, instead,
``do not carry out a run-up.'' In that same paragraph, EASA also
requests that we add after ``then manually de-ice the engines'' the
phrase ``or confirm ice is not present in the engine core before
further flight.'' EASA also requests that we add ``or 60 minutes since
the last run-up'' after the phrase ``if take-off is not accomplished in
freezing fog within 60 minutes total taxi time'' in paragraph (h) of
the NPRM.
We agree that clarification is necessary. However, we do not agree
that it is necessary to revise the phrase as specified. After 60
minutes, there is no run-up procedure that will shed the ice. As a
clarification, we have revised the AFM wording specified in paragraph
(f) of the AD to read ``Takeoff is not permitted if total taxi time in
freezing fog with visibility of 300 meters or less exceeds 60 minutes
without accomplishing the above core ice shed procedure. The engine
core must be manually de-iced'' instead of ``If takeoff is not
accomplished within 60 minutes total taxi time, then manually de-ice
the engines.''
Explanation of Revised Unsafe Condition
We have revised the unsafe condition to state that internal engine
damage could result in a forced landing rather than in loss of control
of the airplane. Upon further review of the regulations, we determined
that a power loss in this case does not leave the airplane
uncontrollable, but rather leads to a forced landing.
Explanation of Revised AMOC Paragraph
We have removed paragraph (j)(3) of the NPRM. That paragraph refers
to alternative repair methods, and this AD does not include a repair.
Conclusion
We have carefully reviewed the available data, including the
comments received, and determined that air safety and the public
interest require adopting the AD with the changes described previously.
We have determined that these changes will neither increase the
economic burden on any operator nor increase the scope of the AD.
Costs of Compliance
There are about 208 airplanes of the affected design in the
worldwide fleet. This AD affects about 53 airplanes of U.S. registry.
The actions take about 1 work hour per airplane, at an average labor
rate of $80 per work hour. Based on these figures, the estimated cost
of the AD for U.S. operators is $4,240, or $80 per airplane.
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.
We are 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
We have determined that this AD will not have federalism
implications under Executive Order 13132. This AD will not have a
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) Is not a ``significant rule'' under DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979); 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.
We prepared a regulatory evaluation of the estimated costs to
comply with this AD and placed it in the AD docket. See the ADDRESSES
section for a location to examine the regulatory evaluation.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
Adoption of the Amendment
0
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 Federal Aviation Administration (FAA) amends Sec. 39.13 by
adding the following new airworthiness directive (AD):
2008-02-05 Boeing: Amendment 39-15335. Docket No. FAA-2006-25609;
Directorate Identifier 2005-NM-263-AD.
Effective Date
(a) This AD becomes effective February 27, 2008.
Affected ADs
(b) None.
Applicability
(c) This AD applies to Boeing Model 777-200 and -300 series
airplanes, certificated in any category, equipped with Rolls-Royce
RB211 TRENT 800 engines.
Unsafe Condition
(d) This AD results from reports of engine surges and internal
engine damage due to ice accumulation during extended idle thrust
operation in ground fog icing conditions. We are issuing this AD to
prevent internal engine damage due to ice accumulation and shedding,
which could cause a shutdown of both engines, and result in a forced
landing of the airplane.
Compliance
(e) You are responsible for having the actions required by this
AD performed within the compliance times specified, unless the
actions have already been done.
Airplane Flight Manual (AFM) Revision
(f) Within 14 days after the effective date of this AD, revise
the Limitations Section of the Boeing 777 Airplane Flight Manual
(AFM) to include the following statements. This may be done by
inserting a copy of this AD in the AFM.
``GROUND OPERATIONS IN FREEZING FOG WITH VISIBILITY OF 300 METERS OR
LESS
When freezing fog with visibility of 300 meters or less is
reported and
(a) The OAT is 0 degrees C to -6 degrees C then run up the
engines to 50% N1 for 1 minute every 45 minutes taxi time, or
(b) The OAT is -7 degrees C to -13 degrees C then run up the
engines to 59% N1 for 1 minute for every 45 minutes taxi time, or
[[Page 3867]]
(c) The OAT is colder than -13 degrees C and taxi time exceeds
45 minutes, there is no run-up procedure; the engines must be
manually de-iced.
Regardless of temperature, if the core ice shedding procedure
described above is not accomplished within 45 minutes total taxi
time in freezing fog with visibility of 300 meters or less, but
takeoff can be achieved within 60 minutes total taxi time in
freezing fog with visibility of 300 meters or less, takeoff is
permitted. A borescope inspection is required within 10 flights.
Takeoff is not permitted if total taxi time in freezing fog with
visibility of 300 meters or less exceeds 60 minutes without
accomplishing the above core ice shed procedure. The engine core
must be manually de-iced.''
(g) When a statement identical to that in paragraph (f) of this
AD has been included in the general revisions of the AFM, the
general revisions may be inserted into the AFM, and the copy of this
AD may be removed from the AFM.
Inspection for Ice
(h) If takeoff is not accomplished in freezing fog, with
visibility of 300 meters or less, within 60 minutes total taxi time,
before further flight, perform an inspection for ice of the variable
inlet guide vanes (VIGVs), inspect the low pressure compressor (fan)
for ice, and ensure that all fan, spinner, air intake splitter
fairing, and VIGV surfaces are free of ice after engine operation in
freezing fog with visibility of 300 meters or less, in accordance
with a method approved by the Manager, Seattle Aircraft
Certification Office (ACO). One acceptable method of compliance is
Chapter 12-33-03 of the Boeing 777 Airplane Maintenance Manual
(AMM).
(1) If no ice is detected, the time already completed in
freezing conditions can be reset to zero for subsequent operation.
(2) If any ice is detected, before further flight, manually de-
ice the engine core inlet. Upon completion of the manual de-ice
process, the fan, spinner, air intake splitter fairing, and VIGV
surfaces must be free of ice and all residual water removed. Two
acceptable methods to manually de-ice the engine can be found in
Chapter 12-33-03 of the Boeing 777 AMM. At no time during the manual
de-ice process should the temperature of the air supplied exceed 176
degrees Fahrenheit.
Borescope Inspection for Damage
(i) For airplanes on which the core ice shedding procedure is
not accomplished within 45 minutes total taxi time, but that achieve
takeoff within 60 minutes total taxi time in freezing fog with
visibility of 300 meters or less, regardless of temperature during
ground operations in freezing fog with visibility of 300 meters or
less: Within 10 flight cycles after takeoff, perform a borescope
inspection to detect missing material of the intermediate pressure
compressor (IPC) stage 1 blades. If any material is found to be
missing, do a full borescope inspection of the IPC and high pressure
compressor (HPC) before further flight. Do the actions in accordance
with a method approved by the Manager, Seattle Aircraft
Certification Office (ACO), FAA. One acceptable method of compliance
is to perform all applicable borescope inspections in accordance
with Chapter 72-00-00 of the Boeing 777 AMM. If any damage is
detected, further action in accordance with the current AMM limits
must be taken before further flight.
Alternative Methods of Compliance (AMOCs)
(j)(1) The Manager, Seattle ACO, FAA, has the authority to
approve AMOCs for this AD, if requested in accordance with the
procedures found in 14 CFR 39.19.
(2) To request a different method of compliance or a different
compliance time for this AD, follow the procedures in 14 CFR 39.19.
Before using any approved AMOC on any airplane to which the AMOC
applies, notify your appropriate principal inspector (PI) in the FAA
Flight Standards District Office (FSDO), or lacking a PI, your local
FSDO.
Material Incorporated by Reference
(k) None.
Issued in Renton, Washington, on January 10, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. E8-843 Filed 1-22-08; 8:45 am]
BILLING CODE 4910-13-P