Discussion
We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 90-26-01, Amendment 39-6810 (55 FR 49611, November 30, 1990), (``AD 90-26-01''), and AD 91-20-02, Amendment 39- 8036 (56 FR 55231, October 25, 1991), (``AD 91-20-02''), and AD 2009- 05-02, Amendment 39-15826 (74 FR 8161, February 24, 2009), (``AD 2009- 05-02''). AD 90-26-01 and AD 91-20-02 applied to all GE CF6-80C2 series turbofan engines. AD 2009-05-02 applied to all GE CF6-80C2 and CF6-80E1 series turbofan engines. The NPRM published in the Federal Register on January 17, 2014 (79 FR 3139). The NPRM was prompted by a report of an under-cowl fire caused by a manifold high-pressure fuel leak and several additional reports of fuel leaks. The NPRM proposed to retain the requirements of the superseded ADs: AD 90-26-01 and AD 91-20-02 required removal of certain fuel manifold P/Ns; AD 2009-05-02 required inspection of certain fuel manifold P/Ns and replacement of certain consumable components. The NPRM also proposed to require removal of additional fuel manifold P/Ns, performance of additional initial and repetitive inspections, replacement as required of certain fuel manifold P/Ns and tube (block) clamps, and replacement of loop clamps at each fuel manifold inspection opportunity. We are issuing this AD to prevent failure of the fuel manifold, which could lead to uncontrolled engine fire, engine damage, and damage to the airplane.
Comments
We gave the public the opportunity to participate in developing this AD. The following presents the comments received on the NPRM (79 FR 3139, January 17, 2014) and the FAA's response to each comment.
Request To Replace Two Incorrect Part Numbers
Several commenters requested that we replace two incorrect fuel manifold P/Ns with the correct P/Ns.
We agree. We corrected the P/Ns in paragraph (c) of this AD from P/ Ns 1308M31G12 and 1308M32G12 to P/Ns 1303M31G12 and 1303M32G12.
Request To Change and Clarify Compliance Information
Several commenters requested that we make changes to Table 1 to paragraph (e) in the NPRM (79 FR 3139, January 17, 2014). Three commenters requested that we remove the compliance time of six months because this requirement is unjustified. Two commenters requested that we remove one row of information due to redundancy. One commenter requested that we reorder the rows to make the table easier to follow.
We partially agree. We agree that the table is problematic. A six- month compliance time was meant to be a ``grace period'' for products that might have already exceeded the threshold. But, including a ``grace period'' is unnecessary, since AD 2009-05-02, which we are superseding with this AD, mandates the same requirement. We removed the six-month compliance time period.
We disagree with making the other changes as suggested, but did reword paragraph (e) to this AD to eliminate the tables and clarify the AD.
Request To Change Definition of Shop Visit
Several commenters requested that we change the definition of shop visit to exclude certain maintenance visits because the current definition forces the replacement of the fuel manifold at the majority of shop visits.
We agree. We changed the definition of shop visit for the purposes of this AD to exclude shop visits for specified types of maintenance.
Request To Allow Reinstallation of Certain P/N Fuel Manifolds During On-Wing Maintenance
Virgin Atlantic Airways, Delta Air Lines, AIRDO, and GE requested that we allow reinstallation of fuel manifolds, P/Ns 1303M31G12, 1303M32G12, 2420M70G01, and 2420M71G01, during on-wing maintenance, and only mandate removal of these P/Ns during shop visits. The commenters state that modification of the fuel manifold configuration during on- wing maintenance is not practicable due to complexity, potential for maintenance error, and cost compared to replacement during shop visit.
We agree. The intent of this AD is to require removal of fuel manifolds, P/Ns 1303M31G12, 1303M32G12, 2420M70G01, and 2420M71G01, during shop visit, not during on-wing maintenance. We removed the installation prohibition statement that included these P/Ns.
Request To Exclude Certain Engine Models From Applicability
Lufthansa Cargo requested that we exclude from the applicability of this AD certain CF6-80C2 engine models.
We disagree. All CF6-80C2 engine models are affected by the same unsafe condition. We did not change this AD.
Request To Change the Focus of This AD, and To Retain and Supersede Different ADs
KLM Royal Dutch Airlines (KLM) requested that we address pigtail cracking in this AD, instead of tube (block) clamp and loop clamp chafing, by retaining AD 2009-05-02, Amendment 39-15826 (74 FR 8161, February 24, 2009), AD 91-20-02, Amendment 39-8036 (56 FR 55231, October 25, 1991), and AD 90-26-01, Amendment 39-6810 (55 FR 49611, November 30, 1990), and by superseding AD 2007-11-20, Amendment 39- 15077 (72 FR 30956, June 5, 2007). KLM states that the recent under- cowl fire event was related to pigtail cracking, which the FAA has not addressed, and not to tube (block) and loop clamp chafing.
We disagree. Pigtail cracking, tube (block) clamp chafing, and loop clamp chafing can all be caused by resonant vibration within the engine operation range. This AD requires removal of fuel manifolds susceptible to resonant vibration, which addresses pigtail cracking, tube (block) clamp chafing, and loop clamp chafing leading to fuel manifold leaks. We did not change this AD.
Request To Remove From Paragraph (e)(2) Reference to ``Tube (Block) Clamp''
KLM requested that we delete reference to the ``Tube (Block) Clamp'' from paragraph (e)(2) of this AD because instructions regarding inspection and replacement of the tube (block) clamp are not addressed in that paragraph.
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We partially agree. The reference to the ``Tube(Block) Clamp'' in paragraph (e)(2) is inaccurate. We restructured the compliance paragraphs. Paragraphs (e)(2)(ii) and (e)(2)(iii) of this AD now reference ``Tube (Block) Clamp.''
Request To Provide More Information Regarding the Unsafe Condition
Lufthansa Technik AG and Deutsche Lufthansa AG requested that we provide additional details concerning the unsafe condition.
We partially agree. Although the AD Discussion section provides sufficient information regarding the fuel manifold leaks, we included a reference to additional information in the Related Information paragraph of this AD.
Request To Expand Compliance To Address Other Unsafe Conditions
One commenter requested that we expand the compliance requirements of this AD to address other possible unsafe conditions in the designs of the accessory gearbox, spray shield, and fuel nozzle, and made reference to National Transportation Safety Board (NTSB) safety recommendations (SRs) A-13-022 and A-12-047.
Wedisagree. Unsafe conditions in the engine caused by designs of the accessory gearbox and spray shield are not the subjects of this AD. Fire caused by fuel manifold leak is the subject of this AD. SRs A-13- 022 and A-12-047 do not address fire caused by fuel manifold leaks. We did not change this AD.
Request To Allow Use of Future Revisions of Referenced Service Bulletins (SBs)
Delta Air Lines requested that we allow use of future revisions of the SBs referenced in compliance paragraphs because this would eliminate the need to request an alternative method of compliance (AMOC) if the SBs are revised.
We disagree. We are authorized to mandate use of procedures in SBs that are published and which we have reviewed. Since future revisions of SBs are not yet published, we are not authorized to mandate their use in advance. We did not change this AD.
Request To Address Repetitive Inspections of Fuel Manifolds Repaired With PTFE-Coated Para-Aramid Tape
Japan Airlinesrequested that we allow repetitive inspections of fuel manifolds that have PTFE-coated para-aramid tape at the tube (block) clamp locations. The NPRM (79 FR 3139, January 17, 2014) addressed initial inspections, but did not address repetitive inspections of fuel manifolds repaired with PTFE-coated para-aramid tape.
We agree. We changed the references to SBs in this AD to more recent versions that allow repetitive inspections of fuel manifolds that have PTFE-coated para-aramid tape at the tube (block) clamp locations.
Request To Require the Use of GE Method To Replace Fuel Manifolds
Boeing Commercial Airplanes and another commenter requested that we require that manifolds be replaced using the method stated in the GE SBs. To substantiate the request, the second commenter referred to NTSB SR A-13-028.
We disagree. The regulations require that operators use acceptable methods, techniques, and practices to replace the fuel manifolds. The GE SBs contain one acceptable method to replace the fuel manifolds, but not the only acceptable method of doing so. We did not change this AD.
Request To Clarify Certain Preamble and Compliance Paragraphs
GE requested that we clarify, in the ``Proposed AD Requirements'' paragraph, the additional P/Ns of fuel manifolds to be inspected and replaced. GE also requested that we make clear, in the ``Summary'' paragraph, that on-wing replacement of tube (block) clamps and fuel manifolds is based on inspection results. GE also requested that we use alternative wording in paragraph (e) and Table 2 to paragraph (e) of this AD.
We partially agree. We agree that we needed to clarify the P/Ns to be removed before further flight, and those to be inspected until removed. We changed this AD to clearly identify both groups. We also agree that paragraph (e) of this AD required clarification. We reworded paragraph (e) of this AD to clearly identify the requirements to correct the unsafe condition.
Request To Allow Installation of Certain Prohibited P/Ns
Asiana Airlines, EVA Airways, Thai Airways, AIRDO, and Japan Airlines requested that for fuel manifold, P/Ns 1303M31G12, 1303M32G12, 2420M70G01, and 2420M71G01, we reduce the inspection interval or require non-destructive inspection at shop visits rather than require removal and prohibit installation. The operators state that their records do not indicate that these parts cause leaks or experience wear that would cause their replacement, and they expressed concerns that the reliability of the replacement fuel manifolds is lower than that of the prohibited fuel manifolds.
We disagree. A reduced inspection interval does not prevent pigtail cracking between shop visits. Our data does not justify a reduced inspection interval to prevent fuel leak events, or indicate that the new fuel manifold design has lower reliability. We did not change this AD.
Request To Allow Use of Certain P/Ns for Drained Engine Configurations
Lufthansa TechnikAG requested that we allow the use of fuel manifold, P/Ns 2420M70G01, 2420M71G01, 1303M31G12, and 1303M32G12, as replacement parts for drained (pre SB 73-0253) engine configurations. The commenter states that GE's service information allows use of fuel manifold, P/Ns 1303M31G12 and 1303M32G12, on engines with drain system installed, and this AD does not prohibit installation of fuel manifold, P/Ns 1303M31G10 and 1303M32G10.
We disagree. We have no data showing that drainless fuel manifolds installed in engines with a drain system are more reliable than when installed in engines with a drainless system. We did not change this AD.
Request To Remove Certain Fuel Manifolds From Applicability
Lufthansa Cargo requested that we remove from the applicability of this AD drainless fuel manifolds to which PTFE-coated para-aramid tape was applied and the loop and tube (block) clamps were inspected.
We disagree. We received several reports of fuel leaks and a report of under-cowlfire. The inspections alone required by this AD do not address pigtail cracking leading to fuel leaks, and therefore do not provide an acceptable level of safety. We did not change this AD.
Request To Remove the Word ``Uncontrolled'' From the Description of Fire
Boeing Commercial Airplanes requested that we remove from the preamble the word ``uncontrolled'' from the description of fire caused by a fuel manifold leak because an uncontrolled fire in this scenario could only occur with a significant failure of the engine nacelle fire protection system.
We disagree. The data upon which we relied, including the Continued Airworthiness Assessment Methodologies (CAAM) database for transport category airplanes, includes data showing flammable fluid leaks leading to uncontrolled fires. We did not change this AD.
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Conclusion
We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this AD with the changes described previously and editorial changes to improve clarity. We have determined that these changes:
Are consistent with the intent that was proposed in the NPRM (79 FR 3139, January 17, 2014) for correcting the unsafe condition; and
Do not add any additional burden upon the public than was already proposed in the NPRM (79 FR 3139, January 17, 2014).
We also determined that these changes will not increase the economic burden on any operator or increase the scope of this AD.
Costs of Compliance
We estimate that this AD would affect 1,126 engines installed on airplanes of U.S. registry. We also estimate that required parts cost about $34,894 per engine. We also estimate that it will take about 6 hours to accomplish the actions required by this AD. The average labor rate is $85 per hour. Based on these figures, we estimate the total cost of this AD to U.S. operators to be $39,864,904.
Authority for This Rulemaking
Title 49 ofthe 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),
(3) Will not affect intrastate aviation in Alaska to the extent that it justifies making a regulatory distinction, and
(4) 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.