[Federal Register Volume 66, Number 85 (Wednesday, May 2, 2001)]
[Proposed Rules]
[Pages 21898-21899]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-10889]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NE-61-AD]
RIN 2120-AA64


Airworthiness Directives; GE Aircraft Engines CT7 Series 
Turboprop Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The Federal Aviation Administration (FAA) proposes to adopt a 
new airworthiness directive (AD) that is applicable to GE Aircraft 
Engines (GE) CT7 series turboprop engines. This proposal would require 
removal of stage 2 turbine aft cooling plates of a certain part number 
(P/N) and installation of cooling plates of a new design. This proposal 
is prompted by a report of a stage 2 turbine aft cooling plate 
cracking, resulting in an uncontained engine failure. The actions 
specified by the proposed AD are intended to prevent stage 2 turbine 
aft cooling plate cracking, which could result in uncontained engine 
failure, and damage to the airplane.

DATES: Comments must be received by July 2, 2001.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No. 2000-NE-61-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: [email protected]. 
Comments sent via the Internet must contain the docket number in the 
subject line. Comments may be inspected at this location between 8 a.m. 
and 4:30 p.m., Monday through Friday, except Federal holidays. This 
information may be examined at the FAA, New England Region, Office of 
the Regional Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT: Barbara Caufield, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone: (781) 
238-7146; fax: (781) 238-7199.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications should identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this action may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2000-NE-61-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRM's

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, New England Region, Office of the Regional Counsel, 
Attention: Rules Docket No. 2000-NE-61-AD, 12 New England Executive 
Park, Burlington, MA 01803-5299.

Discussion

    In July 1999, the FAA was made aware of an uncontained failure of a 
GE CT7-5 turboprop engine, caused by a cracked stage 2 turbine aft 
cooling plate. In February 2000, GE identified and reported the root 
cause of the cooling plate failure to the FAA. The failure was due to 
micro-cracking at the cooling air holes and a reduction in material 
properties, caused during manufacture by an excessive electro-discharge 
machining (EDM) recast layer in the air holes followed by inadequate 
abrasive flow. GE has identified those cooling plates manufactured by 
this method, as P/N 6064T07P02, having the serial number (SN) prefix of 
GFF. GE also has reported that a few unaffected stage 2 turbine aft 
cooling plates, P/N 6064T07P02 having a SN prefix other than GFF, are 
installed mainly on engines in foreign military service. This 
condition, if not corrected, could cause cracking of the stage 2 
turbine aft cooling plate, resulting in an uncontained engine failure, 
and damage to the airplane.

FAA's Determination of an Unsafe Condition and Proposed Actions

    Since an unsafe condition has been identified that is likely to 
exist or develop on other GE CT7 series turboprop engines of the same 
type design, the proposed AD would require replacing affected stage 2 
turbine aft cooling plates with new design aft cooling plates, P/N 
6064T07P05, having cooling holes made by conventional drilling methods.

[[Page 21899]]

Economic Impact

    There are approximately 564 engines of the affected design in the 
worldwide fleet. The FAA estimates that 180 engines installed on 
airplanes of U.S. registry would be affected by this proposed AD, that 
it would take approximately 0.5 work hour per engine to accomplish the 
proposed actions, and that the average labor rate is $60 per work hour. 
Required aft cooling plates would cost approximately $15,282 per 
engine. Based on these figures, the total cost impact of the proposed 
AD on U.S. operators is estimated to be $2,756,160. The manufacturer 
has stated that it may provide the new design aft cooling plate at no 
cost to operators, and that if the aft cooling plate is replaced at the 
next engine or hot section module overhaul shop visit, no additional 
labor costs will be incurred.

Regulatory Impact

    This proposed rule does not have federalism implications, as 
defined in Executive Order 13132, because it 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. 
Accordingly, the FAA has not consulted with state authorities prior to 
publication of this proposed rule.
    For the reasons discussed above, I certify that this 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) if promulgated, 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. A copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (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. Section 39.13 is amended by adding the following new 
airworthiness directive:

GE Aircraft Engines:  Docket No. 2000-NE-61-AD.

    Applicability: This airworthiness directive (AD) is applicable 
to GE Aircraft Engines (GE) CT7 Models CT7-5A2, -5A3, -7A, and -7A1 
turboprop engines, installed on but not limited to Construcciones 
Aeronauticas, SA CN-235 series and SAAB Aircraft AB SF340 series 
airplanes.

    Note 1: This AD applies to each engine identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For engines that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (c) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

Compliance

    Compliance is required at the next overall of the engine or hot 
section module, or within 8,000 cycles after the effective date of 
this AD, whichever occurs first, unless already done.
    To prevent stage 2 turbine aft cooling plate cracking, which 
could result in an uncontained engine failure and damage to the 
airplane, do the following:
    (a) Replace stage 2 aft cooling plate 
P/N 6064T07P02 with stage 2 aft cooling plate P/N 6064T07P05.
    (b) After the effective date of this AD, do not install any 
stage 2 aft cooling plate P/N 6064T07P02.

Alternative Methods of Compliance

    (c) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Engine Certification Office (ECO). 
Operators shall submit their request through an appropriate FAA 
Principal Maintenance Inspector, who may add comments and then send 
it to the Manager, ECO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from the ECO.

Special Flight Permits

    (d) Special flight permits may be issued in accordance 
Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 
21.197 and 21.199) to operate the airplane to a location where the 
requirements of this AD can be accomplished.

    Issued in Burlington, Massachusetts, on April 24, 2001.
Donald E. Plouffe,
 Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 01-10889 Filed 5-1-01; 8:45 am]
BILLING CODE 4910-13-U