

[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
