[Federal Register Volume 63, Number 8 (Tuesday, January 13, 1998)]
[Rules and Regulations]
[Pages 1901-1903]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-71]


=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-ANE-41-AD; Amendment 39-10231; AD 97-25-07]
RIN 2120-AA64


Airworthiness Directives; GE Aircraft Engines CT7 Series 
Turboprop Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

-----------------------------------------------------------------------

SUMMARY: This amendment supersedes an existing airworthiness directive 
(AD), applicable to GE Aircraft Engines (GE) CT7 series turboprop 
engines, that currently requires eddy current inspection (ECI) of disk 
holes of stage 1 and 2 gas generator turbine (GGT) disks for cracks, 
and, if necessary, replacement with serviceable parts. This amendment 
increases the initial cyclic compliance threshold while decreasing the 
calendar time for performing the ECI. This amendment is prompted by 
corrections to the applicable alert service bulletin (ASB) serial 
number (S/N) tables. The ASB contained S/Ns which appeared in more than 
one table creating confusion over which cyclic limit applied to each S/
N. The actions specified by 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 January 28, 1998.
    The incorporation by reference of GE (CT7-TP Series) Service 
Bulletin 72-390, Revision 1, dated December 11, 1996, was previously 
approved by the Director of the Federal Register as of April 15, 1997 
(62 FR 15094, March 31, 1997).
    The incorporation by reference of GE (CT7-TP Series) Alert Service 
Bulletin A72-393, Revision 1, dated February 13, 1997, is approved by 
the Director of the Federal Register as of January 28, 1998.
    Comments for inclusion in the Rules Docket must be received on or 
before March 16, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 97-ANE-41-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: ``9-ad-
[email protected]''. Comments sent via the Internet must contain 
the docket number in the subject line.
    The service information referenced in this AD may be obtained from 
GE Aircraft Engines, 1000 Western Ave., Lynn, MA 01910; telephone (781) 
594-3140, fax (781) 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: 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: On February 24, 1997, the Federal Aviation 
Administration (FAA) issued airworthiness directive (AD) 97-05-12, 
Amendment 39-9956 (62 FR 15094, March 31, 1997), applicable to General 
Electric Aircraft Engines (GE) CT7 series turboprop engines, to require 
a one-time eddy current inspection (ECI) for cracks of disk holes of 
stage 1 and 2 gas generator turbine (GGT) disks, and, if necessary, 
replacement with serviceable parts. That action was prompted by a 
report of a GE CT7 series turboprop engine, installed on a SAAB-SCANIA 
SF340 aircraft, that experienced an uncontained stage 2 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. That 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.
    This amendment is prompted by a revision to the applicable alert 
service bulletin (ASB) that provides corrections to the serial number 
(S/N) tables. The ASB contained S/Ns which appeared in more than one 
table creating confusion over which cyclic limit applied to each S/N. 
This amendment supersedes the existing AD and increases the initial 
cyclic compliance threshold while decreasing the calendar time for 
performing the ECI. The compliance times have been adjusted to ensure 
that no part exceeds the cyclic limits nor the compliance end date as 
calculated by GE's risk analysis.
    The FAA has reviewed and approved the technical contents of GE 
(CT7-TP Series) ASB A72-393, Revision 1, dated February 13, 1997, that 
lists by S/N affected stage 1 and 2 GGT disks, and GE (CT7-TP Series) 
Service Bulletin 72-390, Revision 1, dated December 11, 1996, that 
describes procedures for ECI of disk holes for cracks.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other engines of this same type design, this AD 
supersedes AD 97-05-12 to increase the initial cyclic compliance 
threshold while decreasing the calendar time for performing the ECI. 
The actions are required to be accomplished in accordance with the 
service documents described previously.
    Since a situation exists that requires the immediate adoption of 
this

[[Page 1902]]

regulation, it is found that notice and opportunity for prior public 
comment hereon are impracticable, and that good 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 97-ANE-41-AD.'' 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 removing Amendment 39-9956, (62 FR 
15094, March 31, 1997), and by adding a new airworthiness directive, 
Amendment 39-10231, to read as follows:

97-25-07 GE Aircraft Engines: Amendment 39-10231. Docket 97-ANE-41-
AD. Supersedes AD 97-05-12, Amendment 39-9956.

    Applicability: GE 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) Alert Service Bulletin 
(ASB) A72-393, Revision 1, dated February 13, 1997, that have 
accumulated 8,500 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) Service Bulletin (SB) 72-390, Revision 1, dated 
December 11, 1996, at the next GGT module removal, or not to exceed 
3 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) ASB A72-393, Revision 1, dated 
February 13, 1997, that have accumulated less than 8,500 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) ASB A72-393, Revision 1, dated 
February 13, 1997, that have accumulated 11,500 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 3 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) ASB A72-393, Revision 1, dated 
February 13, 1997, that have accumulated less than 11,500 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) ASB A72-393, Revision 1, dated 
February 13, 1997, that have accumulated 8,500 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 3 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) ASB A72-393, Revision 1, dated 
February 13, 1997, that have accumulated less than 8,500 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

[[Page 1903]]

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) ASB A72-393, Revision 1, dated 
February 13, 1997, that have accumulated 11,500 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 3 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) ASB A72-393, Revision 1, dated 
February 13, 1997, that have accumulated less than 11,500 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) ASB A72-393, Revision 1, dated February 13, 1997, 
that have accumulated 8,500 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 3 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) ASB A72-393, Revision 1, dated February 13, 1997, 
that have accumulated less than 8,500 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. 
Operators shall submit their requests 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) service documents:

------------------------------------------------------------------------
         Document No.            Pages   Revision           Date        
------------------------------------------------------------------------
ASB A72-393..................   1-16            1  Feb. 13, 1997.       
    Total pages: 16.                                                    
SB 72-390....................    1-6            1  Dec. 11, 1996.       
    Total pages: 6.                                                     
------------------------------------------------------------------------

    (o) The incorporation by reference of GE (CT7-TP Series) SB 72-
390, dated December 11, 1996, was previously approved by the 
Director of the Federal Register in accordance with 5 U.S.C. 552(a) 
and 1 CFR part 51 as of April 15, 1997 (62 FR 15094, March 31, 
1997).

    (p) The incorporation by reference of GE (CT7-TP Series ) ASB 
A72-393, Revision 1, dated February 13, 1997, is approved by the 
Director of the Federal Register in accordance with 5 U.S.C. 552(a) 
and 1 CFR part 51 as of January 28, 1998.
    (q) Copies of the service documents may be obtained from GE 
Aircraft Engines, 1000 Western Ave., Lynn, MA 01910; telephone (781) 
594-3140, fax (781) 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.
    (r) This amendment becomes effective on January 28, 1998.

    Issued in Burlington, Massachusetts, on December 23, 1997.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 98-71 Filed 1-12-98; 8:45 am]
BILLING CODE 4910-13-U