Document ID: FAA-2006-24145-0012
Agency: faa
Document Type: Rule
Title: Airworthiness Directives; General Electric Company CF6-45 and CF6-50 Series Turbofan Engines
Posted Date: 2008-01-02T05:00Z

[Federal Register: January 2, 2008 (Volume 73, Number 1)]
[Proposed Rules]               
[Page 77-80]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr02ja08-18]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2006-24145; Directorate Identifier 2006-NE-06-AD]
RIN 2120-AA64

 
Airworthiness Directives; General Electric Company CF6-45 and 
CF6-50 Series Turbofan Engines

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Supplemental notice of proposed rulemaking (NPRM); reopening of 
comment period.

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SUMMARY: This supplemental NPRM revises an earlier proposed 
airworthiness directive (AD), applicable to certain General Electric 
Company (GE) CF6-45 and CF6-50 series turbofan engines. That proposed 
AD would have required inspecting and reworking certain forward and aft 
centerbodies of the long fixed core exhaust nozzle (LFCEN) assembly. 
That proposed AD resulted from reports of separation of the forward and 
aft centerbodies of the LFCEN assembly due to high-imbalance engine 
conditions. This supplemental NPRM revises the proposed AD to add one 
engine model, and by replacing the LFCEN instead of repairing the 
centerbodies. This proposed AD results from the engine manufacturer 
issuing new service information. We are proposing this AD to prevent 
the forward and aft centerbody of the LFCEN assembly from separating, 
leading to additional damage to the airplane.

DATES: We must receive any comments on this proposed AD by February 19, 
2008.

ADDRESSES: Use one of the following addresses to comment on this 
proposed AD.
     Federal eRulemaking Portal: Go to http://www.regulations.gov
 and follow the instructions for sending your 

comments electronically.
     Mail: Docket Management Facility, U.S. Department of 
Transportation, 1200 New Jersey Avenue, SE., West Building Ground 
Floor, Room W12-140, Washington, DC 20590-0001.
     Hand Delivery: Deliver to Mail address above between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
     Fax: (202) 493-2251.
    You can get the service information identified in this proposed AD 
from General Electric Company via GE-Aviation, Attn: Distributions, 111 
Merchant St., Room 230, Cincinnati, Ohio 45246, telephone (513) 552-
3272; fax (513) 552-3329.

FOR FURTHER INFORMATION CONTACT: Robert Green, Aerospace Engineer, 
Engine Certification Office, FAA, Engine & Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803; e-mail: 
robert.green@faa.gov; telephone (781) 238-7754; fax (781) 238-7199.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to send us any written relevant data, views, or 
arguments regarding this proposal. Send your comments to an address 
listed under ADDRESSES. Include ``Docket No. FAA-2006-24145; 
Directorate Identifier 2006-NE-06-AD'' in the subject line of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of the proposed AD. We will 
consider all comments received by the closing date and may amend the 
proposed AD in light of those comments.
    We will post all comments we receive, without change, to http://www.regulations.gov
, including any personal information you provide. We 

will also post a report summarizing each substantive verbal contact 
with FAA personnel concerning this proposed AD. Using the search 
function of the Web site, anyone can find and read the comments in any 
of our dockets,

[[Page 78]]

including, if provided, the name of the individual who sent the comment 
(or signed the comment on behalf of an association, business, labor 
union, etc.). You may review the DOT's complete Privacy Act Statement 
in the Federal Register published on April 11, 2000 (65 FR 19477-78).

Examining the AD Docket

    You may examine the AD docket on the Internet at http://www.regulations.gov
; or in person at the Docket Operations office 

between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The AD docket contains this proposed AD, the regulatory 
evaluation, any comments received, and other information. The street 
address for the Docket Operations office (telephone (800) 647-5527) is 
the same as the Mail address provided in the ADDRESSES section. 
Comments will be available in the AD docket shortly after receipt.

Discussion

    On March 27, 2006, we issued a proposal to amend part 39 of the 
Code of Federal Regulations (14 CFR part 39) to add an AD, applicable 
to GE CF6-45 and -50 series turbofan engines. The proposed AD published 
as an NPRM in the Federal Register on March 31, 2006 (71 FR 16246). 
That NPRM proposed to require reworking the forward and aft 
centerbodies to add doublers, larger nuts and bolts, and higher 
strength corrosion resistant nut plates. That rework would be required 
the next time the forward centerbody and aft centerbody are removed 
from the engine after the effective date of this proposed AD.
    Since we issued that NPRM, we determined that the referenced GE 
rework instructions in GE service bulletin (SB) No. CF6-50 S/B 78-0242 
were incompatible with the existing repair in the Engine Manual. GE 
subsequently superseded SB No. CF6-50 S/B 78-0242 with SB No. GE CF6-50 
S/B 78-0244, which corrected the error. We also found that we didn't 
specify the CF6-50A model engine in the Applicability of the proposed 
AD. We added the CF6-50A engine model to the Applicability of the 
proposed AD. Because we expanded the population of affected engines by 
adding the CF6-50A model, this supplemental NPRM reopens the comment 
period to include the CF6-50A engine model and references the new 
rework instructions.
    This condition, if not corrected, could result in the forward and 
aft centerbody of the LFCEN assembly separating, leading to additional 
damage to the airplane.

Comments

    We provided the public the opportunity to participate in the 
development of this proposed AD. We have considered the comments 
received.

Request for Continued Operational Serviceability Limits

    One commenter asks us to provide continued-operation serviceability 
limits in terms of flight cycles or flight hours and a maximum 
allowable crack length to allow operators to schedule removing and 
installing the LFCEN if a crack is found during an in-service, line 
station inspection. The commenter states that specifying continued-
operation serviceability limits will preclude unscheduled maintenance 
and costly downtime. We don't agree that we should provide continued-
operation serviceability limits in this proposed AD. An operator's 
approved maintenance plan should define the continued-operation 
serviceability criteria. We didn't change the proposed NPRM.

Request To Remove Requirement To Modify LFCEN to SB CF6-50 S/B 78-0242

    Atlas Air asks us to remove the requirement to use GE SB No. CF6-50 
S/B 78-0242 to modify the LFCEN. Atlas Air believes that they can 
maintain an equivalent level of safety by modifying the forward and aft 
centerbody as specified in GE SB No. CF6-50 S/B 78-0216, Revision 1, 
dated October 23, 1987, and adhering to the torque requirements for the 
aft centerbody bolts as specified in GE SB No. CF6-50 S/B 78-0241, 
dated January 7, 2003. Atlas Air notes that after the OEM introduced SB 
No. CF6-50 S/B 78-0216 Revision 1, which instituted the Sixteen-bolt 
Forward and Aft Centerbody Configuration, 22 events were recorded. But, 
the OEM has not provided data as to how many of the 22 events occurred 
on centerbodies modified using only SB No. CF6-50 S/B 78-0216, Revision 
1. Atlas Air also notes that no events of separations of the forward 
and aft centerbody have occurred since the OEM introduced the increased 
torque requirements for the forward-to-aft centerbody joint bolts.
    We don't agree. Analysis and component tests following release of 
GE SB No. CF6-50 S/B 78-0216 and SB No. CF6-50 S/B 78-0241 identified 
several other design shortcomings at fan blade-out imbalance loads. 
Improvements released through GE SB No. CF6-50 S/B 78-0242 (and 
subsequently GE SB No. CF6-50 S/B 78-0244) addressed those design 
concerns. GE SB No. CF6-50 S/B 78-0216 and SB No. CF6-50 S/B 78-0241 
don't address fully the identified LFCEN forward-to-aft centerbody 
separation issues. Incorporating the modifications defined in GE SB No. 
CF6-50 S/B 78-0244 would preclude the need to require repetitive on-
wing inspections. We didn't change the proposed NPRM.

Request To Change the Compliance Time

    Atlas Air proposes that we change the compliance time for modifying 
the forward and aft centerbody as specified in GE SB No. CF6-50 S/B 78-
0242 from ``the next time the forward and aft centerbody is removed 
from the engine'' to ``each time the forward or aft centerbody is 
removed and routed for repair.'' Atlas Air states that the requirement 
to modify the forward and aft centerbody each time they remove an 
engine will increase the number of spare centerbodies needed. Atlas Air 
calculates the need for an additional five forward and aft centerbodies 
at an additional cost of $696,960.
    We don't agree. Incorporating the GE SB No. CF6-50 S/B 78-0244 
modifications when the centerbodies are repaired for unserviceable 
conditions would extend the compliance period unreasonably. The intent 
of the original compliance recommendation was to align and execute the 
modifications with engine refurbishments. The intent of the hard-time 
compliance period recommendation in this superseding NPRM is to 
complete the modifications within the same time period as the original 
engine removal recommendations. We didn't change the proposed NPRM.

Request To Change the Costs of Compliance

    Atlas Air also believes that we underestimated the cost impact of 
the proposed rule. Atlas Air uses third party labor and does not agree 
that the $80 per hour rate is the true industry average. Atlas Air also 
observes that we do include the cost of spare centerbodies that would 
be required to support the compliance requirements of this rule. Atlas 
Air used a figure of $100 per hour in their subsequent cost calculation 
and included required spare parts in their projected compliance costs.
    We don't agree. We use the average labor rate established by the 
Office of Aviation Policy, Plans, and Management Analysis (APO) for 
estimating the projected cost impact of ADs. We don't project 
additional costs associated with spare parts, because ADs address an 
unsafe condition in a product (in this case an engine) and the unsafe

[[Page 79]]

condition doesn't exist until the spare parts are on the engine and the 
engine is in service.
    However, GE made corrections to SB No. CF6-50 S/B 78-0244, dated 
July 30, 2007, that included a revision of the projected labor work-
hours to complete the modification. GE SB No. CF6-50 S/B 78-0242, dated 
September 26, 2005, cited 22 work-hours to complete the modification. 
That was for one centerbody half. The total labor work-hours to modify 
both centerbodies are 44 work-hours, which is cited in GE SB No. CF6-50 
S/B 78-0244, dated July 30, 2007. We changed the Costs of Compliance 
section in the AD to reflect 44 work-hours per product.

Request To Change the Compliance Times

    One commenter, FedEx, suggests a hard-time limit of 30 months after 
the effective date of the proposed AD to modify all LFCEN assemblies in 
accordance with GE SB No. CF6-50 S/B 78-0242 (subsequently superseded 
by GE SB No. CF6-50 S/B 78-0244) instead of when the centerbodies are 
removed when an engine is taken off wing. FedEx believes that the 
requirement to perform the modification at the next engine change will 
create an undue burden on line maintenance operations and prolong 
completing the modifications. Spare engines ship without the LFCEN 
assembly which is typically transferred to the new engine from the old 
engine at engine replacement. FedEx states that, under the requirements 
in the current NPRM, operators will have to pre-position spare LFCEN 
assemblies with spare engines to remote outstations. This requirement 
and additional logistics will unduly increase operator spare cost and 
cost of out of service aircraft. FedEx contends that a hard-time 
compliance limit will relieve operations from the increased logistics 
and spare costs and accelerate completion of the modification. With the 
current requirement to complete the modification when the LFCEN is 
removed from the engine, accomplishment could take more than 4 years. A 
fixed time of 30 months, versus at next engine removal, would allow 
operators to control the modifications at heavy maintenance checks and 
expedite completion of the modifications directed by this proposed AD.
    We partially agree. We agree that a hard-time completion 
recommendation works better than an engine removal basis for the 
centerbody rework. We don't agree that 30 months is the appropriated 
compliance period. We revised the proposed NPRM accordingly, citing a 
42 month compliance period. The 42 month limit is based on the CF6-50 
average time-on-wing performance and annual utilization.

Request for a Grace Period

    Two commenters, the Air Transport Association and Northwest 
Airlines, request a grace period of 12 months after the effective date 
of the proposed AD to acquire and modify spare forward and aft 
centerbodies. The commenters state that the available number of 
modified spare centerbody assemblies is extremely low and the grace 
period for provisioning would avoid extended aircraft-on-ground 
situations. We don't agree that a grace period is necessary, given our 
response to the previous comment. We didn't change the proposed NPRM.

Differences Between the Service Bulletin and the Component Maintenance 
Manual Repair Procedure

    Two commenters identified issues with incorporating GE SB No. CF6-
50 S/B 78-0242, dated September 26, 2005.
    One commenter, Air Nippon Airways, requests that the GE SB 
recommend the CMM 78-11-02 repair modification for the forward 
centerbodies and that they be reflected in the FAA AD. Air Nippon 
Airways notes that the fastener locations on the forward centerbody aft 
doubler and aft doubler splices defined by GE SB No. CF6-50 S/B 78-0242 
and GE Repair Document (RD) 250-206-S1 are different than those defined 
by the corresponding Component Maintenance Manual (CMM) repair. The aft 
doubler and aft doubler splices could not be installed on forward 
centerbodies that had been repaired in accordance with the CMM 78-11-02 
Repair 001. In addition, the band doubler specified by the GE SB was 
already required with the CMM repair. We agree. ANA is correct in their 
statement that the GE SB No. CF6-50 S/B 78-0242, dated September 26, 
2005, and CMM instructions were incompatible. GE subsequently 
superseded SB No. CF6-50 S/B 78-0242, dated September 26, 2005, with GE 
SB No. CF6-50 S/B 78-0244, dated July 30, 2007, which corrects the 
error by referencing the pre-existing repair for modifying the forward 
centerbody. We changed the proposed NPRM references to reflect the 
corrected service bulletin instructions.
    One commenter, Airbus, reports that since release of the NPRM, 
docket No. FAA-2007-24145 (Directorate identifier 2006-NE-06-AD), 
operators report having difficulties implementing GE SB No. CF6-50 S/B 
78-0242, dated September 26, 2005, due to a parallel spot-weld repair 
in Engine Manual Repair 78-11-02-300-001. That repair incorporates an 
aft joint doubler that interferes with the repair required by GE SB No. 
CF6-50 S/B 78-0242, dated September 26, 2005. Airbus notes that GE was 
revising SB No. CF6-50 S/B 78-0242, dated September 26, 2005, to define 
the proper doublers, update the repair, and contact the service 
bulletin. Airbus asks if we were informed of this situation and whether 
it is planned to postpone or review the current proposed rulemaking.
    We were aware of the identified issues with the original service 
bulletin recommendations and that GE was revising SB No. CF6-50 S/B 78-
0242, dated September 26, 2005. This proposed AD references the revised 
modifications released by GE SB No. CF6-50 S/B 78-0244, dated July 30, 
2007. This proposed AD addresses those accomplishment instruction 
changes, and address the compliance recommendations proposed by FedEx, 
the ATA, and Northwest Airlines. We didn't change the proposed NPRM.

Relevant Service Information

    We have reviewed and approved the technical contents of GE SB No. 
CF6-50 S/B 78-0244, dated July 30, 2007, that identifies disassembly, 
inspection, rework, and reassembly procedures for the forward and aft 
centerbodies.

Differences Between the Proposed AD and the Service Information

    GE SB No. CF6-50 S/B 78-0244, dated July 30, 2007 requires 
reworking the forward and aft centerbodies when the centerbodies are 
removed from the engine. This proposed NPRM requires replacing the 
centerbodies with centerbodies that were modified using the 
Accomplishment Instructions, Section 3, of GE SB No. CF6-50 S/B 78-
0244, dated July 30, 2007, within 42 months of the effective date of 
the proposed AD.

FAA's Determination and Requirements of the Proposed AD

    We evaluated all pertinent information and identified an unsafe 
condition that is likely to exist or develop on other products of this 
same type design. We are proposing this AD, which will require 
replacing certain forward and aft centerbodies with new or modified 
forward and aft centerbodies. These replacements are required within 42 
months after the effective date of this proposed AD. The proposed AD 
would require you to use the service information described previously 
to modify the forward and aft centerbodies before assembling them to 
the engine.

[[Page 80]]

Costs of Compliance

    We estimate that this proposed AD would affect 379 GE CF6-45 and 
CF6-50 series turbofan engines installed on airplanes of U.S. registry. 
We also estimate that it would take about 44 work hours per engine to 
perform the proposed actions, and that the average labor rate is $80 
per work hour. Required parts would cost about $11,000 per engine. 
Based on these figures, we estimate the total cost of the proposed AD 
to U.S. operators to be $2,802,360.

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 proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD would 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 the proposed 
regulation:
    1. Is not a ``significant regulatory action'' under Executive Order 
12866;
    2. Is not a ``significant rule'' under the DOT Regulatory Policies 
and Procedures (44 FR 11034, February 26, 1979); and
    3. Would 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 proposed AD. 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.

The Proposed Amendment

    Under the authority delegated to me by the Administrator, the 
Federal Aviation Administration proposes to amend 14 CFR part 39 as 
follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.

Sec.  39.13  [Amended]

    2. The FAA amends Sec.  39.13 by adding the following new 
airworthiness directive:

General Electric Company: Docket No. FAA-2006-24145; Directorate 
Identifier 2006-NE-06-AD.

Comments Due Date

    (a) The Federal Aviation Administration (FAA) must receive 
comments on this airworthiness directive (AD) action by February 19, 
2008.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to General Electric Company (GE) CF6-45A, 
CF6-45A2, CF6-50A, CF6-50C, CF6-50CA, CF6-50C1, CF6-50C2, CF6-50C2B, 
CF6-50C2D, CF6-50E, CF6-50E1, CF6-50E2, and CF6-50E2B series 
turbofan engines with long fixed core exhaust nozzle (LFCEN) 
assembly forward centerbody, part number (P/N) 1313M55G01 or G02, P/
N 9076M28G09 or G10, and aft centerbody P/N 1313M56G01 or 
9076M46G05, installed. These engines are installed on, but not 
limited to, Airbus A300 series, Boeing 747 series, McDonnell Douglas 
DC-10 series, and DC-10-30F (KC-10A, KDC-10) airplanes.

Unsafe Condition

    (d) This AD results from reports of separation of LFCEN assembly 
forward and aft centerbodies, due to high imbalance engine 
conditions. We are issuing this AD to prevent the forward and aft 
centerbody of the LFCEN assembly from separating, leading to 
additional damage to the airplane.

Compliance

    (e) You are responsible for having the actions required by this 
AD performed within 42 months after the effective date of this AD, 
unless the actions have already been done.
    (f) Replace the forward centerbody, P/N 1313M55G01 or G02, P/N 
9076M28G09 or G10, and aft centerbody, P/N 1313M56G01 or 9076M46G05 
with a forward and aft centerbody that have been modified using with 
the Accomplishment Instructions, Section 3, of GE service bulletin 
No. CF6-50 S/B 78-0244, dated July 30, 2007.

Alternative Methods of Compliance

    (g) The Manager, Engine Certification Office, has the authority 
to approve alternative methods of compliance for this AD if 
requested using the procedures found in 14 CFR 39.19.

Related Information

    (h) Contact Robert Green, Aerospace Engineer, Engine 
Certification Office, FAA, Engine & Propeller Directorate, 12 New 
England Executive Park, Burlington, MA 01803; e-mail: 
robert.green@faa.gov; telephone (781) 238-7754; fax (781) 238-7199, 

for more information about this AD.

    Issued in Burlington, Massachusetts, on December 17, 2007.
Peter A. White,
Assistant Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. E7-25458 Filed 12-31-07; 8:45 am]

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