AD Amdt-39-9956

[Federal Register Volume 62, Number 61 (Monday, March 31, 1997)]
[Rules and Regulations]
[Pages 15094-15096]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 97-7595]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-ANE-34; Amendment 39-9956; AD 97-05-12]
RIN 2120-AA64


Airworthiness Directives; General Electric Aircraft Engines CT7 
Series Turboprop Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to General Electric Aircraft Engines (GE) CT7 series 
turboprop engines. This action requires eddy current inspection of disk 
holes of stage 1 and 2 gas generator turbine (GGT) disks for cracks, 
and, if necessary, replacement with serviceable parts. This amendment 
is prompted by a report of a stage 2 GGT disk failure. The actions 
specified in this AD are intended to prevent a stage 1 or 2 GGT disk 
failure, which could result in an uncontained engine failure and damage 
to the aircraft.

DATES: Effective April 15, 1997.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of April 15, 1997.
    Comments for inclusion in the Rules Docket must be received on or 
before May 30, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 96-ANE-34, 12 New England 
Executive Park, Burlington, MA 01803-5299.
    The service information referenced in this AD may be obtained from 
GE Aircraft Engines, 1000 Western Ave., Lynn, MA 01910; telephone (617) 
594-3140, fax (617) 594-4805. This information may be examined at the 
FAA, New England Region, Office of the Assistant Chief Counsel, 12 New 
England Executive Park, Burlington, MA; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Dave Keenan, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (617) 
238-7139, fax (617) 238-7199.

SUPPLEMENTARY INFORMATION: The Federal Aviation Administration 
(FAA) has received a report of a General Electric Aircraft Engines 
(GE) CT7 series turboprop engine, installed on a SAAB-SCANIA SF340 
aircraft, that experienced an uncontained stage 2 gas generator 
turbine (GGT) failure during takeoff. The investigation revealed 
that the failure was caused by a crack in a disk cooling hole. The 
most likely cause of the cracking was machining damage to the disk 
cooling hole during manufacturing. This condition, if not 
corrected, could result in a stage 1 or 2 GGT disk failure, which 
could result in an uncontained engine failure and damage to the 
aircraft.

    The FAA has reviewed and approved the technical contents of GE 
(CT7-TP Series) Alert Service Bulletin (SB) A72-393, dated November 26, 
1996, that lists by serial number (S/N) affected stage 1 and 2 GGT 
disks, and (CT7-TP Series) SB 72-390, Revision 1, dated December 11, 
1996, that describes the procedures for eddy current inspection (ECI) 
of disk holes for cracks.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other engines of the same type design, this AD is 
being issued to prevent stage 1 or 2 GGT disk failure, which could 
result in an uncontained engine failure and damage to the aircraft. 
This AD requires a one-time ECI for cracks of disk holes of stage 1 and 
2 GGT disks, and, if necessary, replacement with serviceable parts. The 
inspection compliance time is at the next GGT module removal, or 9 
months after the effective date of this AD, whichever occurs first. The 
actions are required to be accomplished in accordance with the SBs 
described previously.
    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good

[[Page 15095]]

cause exists for making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 96-ANE-34.'' The postcard will be date stamped and 
returned to the commenter.
    The regulations adopted herein will not have substantial direct 
effects 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. Therefore, in 
accordance with Executive Order 12612, it is determined that this final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and is not a ``significant regulatory action'' 
under Executive Order 12866. It has been determined further that this 
action involves an emergency regulation under DOT Regulatory Policies 
and Procedures (44 FR 11034, February 26, 1979). If it is determined 
that this emergency regulation otherwise would be significant under DOT 
Regulatory Policies and Procedures, a final regulatory evaluation will 
be prepared and placed in the Rules Docket. A copy of it, if filed, may 
be obtained from the Rules Docket at the location provided under the 
caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 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:

97-05-12 General Electric Aircraft Engines: Amendment 39-9956. 
Docket 96-ANE-34.

    Applicability: General Electric Aircraft Engines (GE) Models 
CT7-5A2, -7A, -9B, -9C turboprop engines, installed on but not 
limited to Construcciones Aeronauticas, SA (CASA) CN-235 series and 
SAAB-SCANIA SF340 series aircraft.

    Note 1: This airworthiness directive (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 (l) 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: Required as indicated, unless accomplished 
previously.
    To prevent a stage 1 or 2 gas generator turbine (GGT) disk 
failure, which could result in an uncontained engine failure and 
damage to the aircraft, accomplish the following:
    (a) For all stage 1 GGT disks, Part Number (P/N) 6064T06P01, 
identified in Table 1 of GE (CT7-TP Series) SB A72-393, dated 
November 26, 1996, that have accumulated 7,000 or more cycles since 
new (CSN) on the effective date of this AD, perform a one time eddy 
current inspection (ECI) for cracks in accordance with the 
Accomplishment Instructions of GE (CT7-TP Series) SB 72-390, 
Revision 1, dated December 11, 1996, at the next GGT module removal, 
or not to exceed 9 months after the effective date of this AD, 
whichever occurs first.
    (b) For all stage 1 GGT disks, P/N 6064T06P01, identified in 
Table 1 of GE (CT7-TP Series) SB A72-393, dated November 26, 1996, 
that have accumulated less than 7,000 CSN on the effective date of 
this AD, perform a one time ECI for cracks in accordance with the 
Accomplishment Instructions of GE (CT7-TP Series) SB 72-390, 
Revision 1, dated December 11, 1996, at the next GGT module removal, 
but not to exceed 9,000 CSN.
    (c) For all stage 1 GGT disks, P/N 6064T06P01, identified in 
Table 2 of GE (CT7-TP Series) SB A72-393, dated November 26, 1996, 
that have accumulated 10,000 or more CSN on the effective date of 
this AD, perform a one time ECI for cracks in accordance with the 
Accomplishment Instructions of GE (CT7-TP Series) SB 72-390, 
Revision 1, dated December 11, 1996, at the next GGT module removal, 
or not to exceed 9 months after the effective date of this AD, 
whichever occurs first.
    (d) For all stage 1 GGT disks, P/N 6064T06P01, identified in 
Table 2 of GE (CT7-TP Series) SB A72-393, dated November 26, 1996, 
that have accumulated less than 10,000 CSN on the effective date of 
this AD, perform a one time ECI for cracks in accordance with the 
Accomplishment Instructions of GE (CT7-TP Series) SB 72-390, 
Revision 1, dated December 11, 1996, at the next GGT module removal, 
but not to exceed 12,000 CSN.
    (e) For all stage 2 GGT disks, P/N 6064T12P01, identified in 
Table 3 of GE (CT7-TP Series) SB A72-393, dated November 26, 1996, 
that have accumulated 7,000 or more CSN on the effective date of 
this AD, perform a one time ECI for cracks in accordance with the 
Accomplishment Instructions of GE (CT7-TP Series) SB 72-390, 
Revision 1, dated December 11, 1996, at the next GGT module removal, 
or not to exceed 9 months after the effective date of this AD, 
whichever occurs first.
    (f) For all stage 2 GGT disks, P/N 6064T12P01, identified in 
Table 3 of GE (CT7-TP Series) SB A72-393, dated November 26, 1996, 
that have accumulated less than 7,000 CSN on the effective date of 
this AD, perform a one time ECI for cracks in accordance with the 
Accomplishment Instructions of GE (CT7-TP Series) SB 72-390, 
Revision 1, dated December 11, 1996, at the next GGT module removal, 
but not to exceed 9,000 CSN.
    (g) For all stage 2 GGT disks, P/N 6064T12P01, identified in 
Table 4 of GE (CT7-TP Series) SB A72-393, dated November 26, 1996, 
that have accumulated 10,000 or more CSN on the effective date of 
this AD, perform a one time ECI for cracks in accordance with the 
Accomplishment Instructions of GE (CT7-TP Series) SB 72-

[[Page 15096]]

390, Revision 1, dated December 11, 1996, at the next GGT module 
removal, or not to exceed 9 months after the effective date of this 
AD, whichever occurs first.
    (h) For all stage 2 GGT disks, P/N 6064T12P01, identified in 
Table 4 of GE (CT7-TP Series) SB A72-393, dated November 26, 1996, 
that have accumulated less than 10,000 CSN on the effective date of 
this AD, perform a one time ECI for cracks in accordance with the 
Accomplishment Instructions of GE (CT7-TP Series) SB 72-390, 
Revision 1, dated December 11, 1996, at the next GGT module removal, 
but not to exceed 12,000 CSN.
    (i) For all stage 1 GGT disks, P/N 6064T06P01, and all stage 2 
GGT disks, P/N 6064T12P01, not identified in Tables 1 through 4 of 
GE (CT7-TP Series) SB A72-393, dated November 26, 1996, that have 
accumulated 7,000 or more CSN on the effective date of this AD, 
perform a one time ECI for cracks in accordance with the 
Accomplishment Instructions of GE (CT7-TP Series) SB 72-390, 
Revision 1, dated December 11, 1996, at the next GGT module removal, 
or not to exceed 9 months after the effective date of this AD, 
whichever occurs first.
    (j) For all stage 1 GGT disks, P/N 6064T06P01, and all stage 2 
GGT disks, P/N 6064T12P01, not identified in Tables 1 through 4 of 
GE (CT7-TP Series) SB A72-393, dated November 26, 1996, that have 
accumulated less than 7,000 CSN on the effective date of this AD, 
perform a one time ECI for cracks in accordance with the 
Accomplishment Instructions of GE (CT7-TP Series) SB 72-390, 
Revision 1, dated December 11, 1996, at the next GGT module removal, 
but not to exceed 9,000 CSN.
    (k) Prior to further flight, remove from service cracked disks, 
and replace with serviceable parts.
    (l) 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. The 
request should be forwarded through an appropriate FAA Principal 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Engine Certification Office.

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

    (m) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the aircraft to a location where 
the requirements of this AD can be accomplished.
    (n) The actions required by this AD shall be done in accordance 
with the following GE (CT7-TP Series) SBs:

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              Document No.                 Pages             Revision                         Date              
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A72-393.................................     1-16  Original...................  November 26, 1996.              
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    Total...............................       16                                                               
72-390..................................      1-6  1..........................  December 11, 1996.              
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    Total...............................        6                                                               
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    This incorporation by reference was approved by the Director of 
the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR 
part 51. Copies may be obtained from GE Aircraft Engines, 1000 
Western Ave., Lynn, MA 01910; telephone (617) 594-3140, fax (617) 
594-4805. Copies may be inspected at the FAA, New England Region, 
Office of the Assistant Chief Counsel, 12 New England Executive 
Park, Burlington, MA; or at the Office of the Federal Register, 800 
North Capitol Street, NW., suite 700, Washington, DC.
    (o) This amendment becomes effective on April 15, 1997.

    Issued in Burlington, Massachusetts, on February 24, 1997.
James C. Jones,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 97-7595 Filed 3-28-97; 8:45 am]
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