[Federal Register: April 2, 2009 (Volume 74, Number 62)]
[Rules and Regulations]
[Page 14929-14931]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr02ap09-1]
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Rules and Regulations
Federal Register
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[[Page 14929]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2007-0419; Directorate Identifier 2007-NE-52-AD;
Amendment 39-15871; AD 2009-07-12]
RIN 2120-AA64
Airworthiness Directives; General Electric Company CF34-1A, -3A,
-3A1, -3A2, -3B, and -3B1 Turbofan Engines
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
-----------------------------------------------------------------------
SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
General Electric Company (GE) CF34-1A, -3A, -3A1, -3A2, -3B, and -3B1
turbofan engines with high-pressure (HP) rotor 4-step air balance
piston stationary seals (4-step seals), part numbers (P/Ns) 4923T54G01,
6019T90G03, 6037T99G01, 6037T99G02, and 6037T99G03, installed. This AD
requires removing the 4-step seals and incorporating an 8-step seal at
the next piece-part exposure. This AD results from the investigation of
an airplane accident. Both engines experienced high-altitude flameout.
Rotation of the HP rotors was not maintained during descent and the
engines could not be restarted. We are issuing this AD to prevent the
inability to restart both engines after flameout due to excessive
friction of the 4-step seal, which could result in subsequent forced
landing of the airplane.
DATES: This AD becomes effective May 7, 2009.
ADDRESSES: The Docket Operations office is located at Docket Management
Facility, U.S. Department of Transportation, 1200 New Jersey Avenue,
SE., West Building Ground Floor, Room W12-140, Washington, DC 20590-
0001.
FOR FURTHER INFORMATION CONTACT: Kenneth Steeves, Aerospace Engineer,
Engine Certification Office, Engine and Propeller Directorate, FAA, 12
New England Executive Park, Burlington, MA 01803; e-mail:
kenneth.steeves@faa.gov; telephone: (781) 238-7765; fax: (781) 238-
7199.
SUPPLEMENTARY INFORMATION: The FAA proposed to amend 14 CFR part 39
with a proposed AD. The proposed AD applies to GE CF34-1A, -3A, -3A1, -
3A2, -3B, and -3B1 turbofan engines with HP rotor 4-step air balance
piston stationary seals (4-step seals), P/Ns 4923T54G01, 6019T90G03,
6037T99G01, 6037T99G02, and 6037T99G03, installed. We published the
proposed AD in the Federal Register on July 23, 2008 (73 FR 42725).
That action proposed to require removing the 4-step seals and
incorporating an 8-step seal at the next piece-part exposure.
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 AD, the regulatory evaluation,
any comments received, and other information. The street address for
the Docket Operations office (telephone (800) 647-5527) is provided in
the ADDRESSES section. Comments will be available in the AD docket
shortly after receipt.
We provided the public the opportunity to participate in the
development of this AD. We have considered the comments received.
Request To Reword the Reason for Engine Modification
Air Wisconsin Airlines requests that the proposed AD be reworded to
indicate that the desired reason for the engine modification is to
enhance safety, and not as a result of the accident, as stated.
Otherwise, the implication is that the CF34 engine does not meet the
certification requirements, which, is inaccurate. The commenter also
states that they believe the justification stated in the NPRM is a
gross misrepresentation of the situation and events, which led up to
the referenced accident. The commenter states that the failure of the
engines to restart after the flameout event was a direct result of the
flight crew failing to properly follow in-flight engine restart
procedures. The commenter states that every engine is tested during the
aircraft certification test flight process to ensure it meets the
requirements of Federal Aviation Regulation 25.903.
We do not agree. The proposed AD does not state that the 4-step
seal was the cause of the accident, but that the proposed AD resulted
from the investigation of the accident. The investigation found that
under certain high-power, high-altitude engine shutdown events,
interference between the rotating and stationary portions of the 4-step
air balance piston seal can develop. We did not change the AD.
Request To Clarify ``Piece-Part Exposure'' Definition
Air Wisconsin Airlines states that if the desire is to ensure
engine modification at first exposure, then the requirement should
indicate to accomplish the GE seal modification service bulletin at
``piece-part-exposure''. Piece-part exposure should be defined as
``removal of the combustion liner'' but no later than the first life-
limited part shop visit, since this is when the HP turbine life-limited
parts (and typically the combustion liner) are removed. The commenter
also states that the proposed AD compliance requirements are not
entirely clear. The air balance piston seal is a non-serialized part,
which makes it difficult to track and manage the part. The commenter
states that they have observed a maintenance and overhaul shop that
overlooked a particular requirement to incorporate a modification,
because of an interpretation of what ``piece-part exposure'' was.
We partially agree. We agree that the 4-step seal should be removed
when the combustion liner is removed at piece-part exposure. We do not
agree removal must be tied to the life-limited parts. We changed the
piece-part exposure definition in the AD to state ``For the purposes of
this AD, piece-part exposure means when the 4-step seal is removed from
the engine or when the combustion liner is removed.''
[[Page 14930]]
Request To Change Incident Description Statement
GE requests that we change the incident description statement of
``Both engines experienced high-altitude flameouts'' which appears in
the proposed AD Summary and Unsafe Condition, to ``As a result of a
high-altitude airplane stall and upset, both engines experienced high-
power flameouts.'' The commenter states that this change is a more
accurate representation of the event.
We do not agree. As we have said previously the proposed AD does
not state that the 4-step seal caused the accident. GE found during the
course of the investigation that under certain high-power, high-
altitude engine shutdown events, interference between the rotating and
stationary portions of the 4-step air balance piston seal can develop.
We did not change the AD.
Request To Change the FAA's Reason for the AD Action
GE requests that we change the FAA's reason statement for the AD
action, from ``We are proposing this AD to prevent the inability to
restart both engines after flameout due to excessive friction of the 4-
step seal, which could result in subsequent forced landing of the
airplane'' to ``We are proposing this AD to enhance the ability to
restart an engine after flameout by reducing the friction in the 4-step
seal, which could result in subsequent forced landing of the
airplane.'' The commenter states that this change would be a more
accurate representation and support the assessment that this is a very
rare occurrence and the recommended actions are not prevalent as proven
by the category level of the relevant service bulletins.
We do not agree. As already noted, the accident was not attributed
to the friction of the 4-step seal. We have found an unsafe condition
with the product. The proposed wording suggests the modification or
replacement may not be adequate to address the inability to restart due
to the friction. We did not change the AD.
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
We estimate that this AD will affect 2,722 CF34-1A, -3A, -3A1, -
3A2, -3B, and -3B1 turbofan engines installed on airplanes of U.S.
registry. We estimate that approximately 2,450 engines with 4-step
seals will incorporate the 8-step seal configuration at an overhaul
shop visit at no additional cost. We estimate that approximately 272
engines with 4-step seals will require additional work to modify the
seal insert to the 8-step seal configuration. We estimate that it will
take about 5 work-hours per engine to perform the seal modification,
and that the average labor rate is $80 per work-hour. Based on these
figures, we estimate the total cost of the AD to U.S. operators to be
$108,800.
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 summary of the costs to comply with this AD and
placed it in the AD Docket. You may get a copy of this summary at the
address listed under ADDRESSES.
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 Federal Aviation Administration 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:
2009-07-12 General Electric Company: Amendment 39-15871. Docket No.
FAA-2007-0419; Directorate Identifier 2007-NE-52-AD.
Effective Date
(a) This airworthiness directive (AD) becomes effective May 7,
2009.
Affected ADs
(b) None.
Applicability
(c) This AD applies to General Electric Company (GE) CF34-1A, -
3A, -3A1, -3A2, -3B, and -3B1 turbofan engines, with high-pressure
(HP) rotor 4-step air balance piston stationary seals (4-step
seals), part numbers (P/Ns) 4923T54G01, 6019T90G03, 6037T99G01,
6037T99G02, and 6037T99G03, installed. These engines are installed
on, but not limited to, Bombardier, Inc. airplane models CL-600-
2A12, -2B16, and -2B19.
Unsafe Condition
(d) This AD results from the investigation of an airplane
accident. Both engines experienced high-power flameout. Rotation of
the HP rotors was not maintained during descent and the engines
could not be restarted. We are issuing this AD to prevent the
inability to restart both engines after flameout due to excessive
friction of the 4-step seal, which could result in subsequent forced
landing of the airplane.
Compliance
(e) You are responsible for having the actions required by this
AD performed at the next piece-part exposure after the effective
date of this AD, unless the actions have already been done.
(f) Remove the 4-step seals, P/Ns 4923T54G01, 6019T90G03,
6037T99G01, 6037T99G02, and 6037T99G03.
(g) Incorporate an 8-step seal, either by modifying the existing
4-step seal to an 8-step seal, or by replacing it with an 8-step
seal.
[[Page 14931]]
(h) Information on modifying the seal and part number
configuration charts, can be found in GE Service Bulletin (SB) No.
CF34-AL S/B 72-0238, dated July 27, 2007 (CL-600-2B19), and SB No.
CF34-BJ S/B 72-0217, dated July 27, 2007 (CL-600-2A12 and CL-600-
2B16).
Definition
(i) For the purposes of this AD, piece-part exposure means when
the 4-step seal is removed from the engine or when the combustion
liner is removed.
Alternative Methods of Compliance
(j) 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
(k) Contact Kenneth Steeves, Aerospace Engineer, Engine
Certification Office, Engine and Propeller Directorate, FAA, 12 New
England Executive Park, Burlington, MA 01803; e-mail:
keneth.steeves@faa.gov; telephone: (781) 238-7765, fax: (781) 238-
7199, for more information about this AD.
Material Incorporated by Reference
(l) None.
Issued in Burlington, Massachusetts, on March 26, 2009.
Peter A. White,
Assistant Manager, Engine and Propeller Directorate, Aircraft
Certification Service.
[FR Doc. E9-7417 Filed 4-1-09; 8:45 am]
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