[Federal Register Volume 59, Number 168 (Wednesday, August 31, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-20591]


[[Page Unknown]]

[Federal Register: August 31, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 94-ANE-07; Amendment 39-9011; AD 94-17-16]

 

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 supersedes an existing airworthiness directive 
(AD), applicable to General Electric Aircraft Engines (GEAE) CT7 series 
turboprop engines, that currently requires a one-time ultrasonic 
inspection of a suspect population of propeller shafts for 
metallurgical defects, and if necessary, replacement with a serviceable 
part. This amendment extends the compliance time for the required 
ultrasonic inspection on certain propeller shafts. This amendment is 
prompted by information indicating that the equipment necessary to 
perform the ultrasonic inspection is less available than originally 
assumed. The actions specified by this AD are intended to prevent 
failure of the propeller shaft, which can result in separation of the 
propeller from the propeller shaft and possible damage to the aircraft.

DATES: Effective September 15, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of September 15, 1994.
    Comments for inclusion in the Rules Docket must be received on or 
before October 31, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 94-ANE-07, 12 New England 
Executive Park, Burlington, MA 01803-5299.
    The service information referenced in this AD may be obtained from 
General Electric Aircraft Engines, 1000 Western Avenue, Lynn, MA 01910. 
This information may be examined at the FAA, New England Region, Office 
of the Assistant Chief Counsel, Burlington, MA; or at the Office of the 
Federal Register, 800 North Capitol Street, NW., suite 700, Washington, 
DC.

FOR FURTHER INFORMATION CONTACT: Daniel Kerman, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (617) 
238-7130, fax (617) 238-7199.

SUPPLEMENTARY INFORMATION: On July 8, 1994, the Federal Aviation 
Administration (FAA) issued airworthiness directive (AD) 94-15-01, 
Amendment 39-8972 (59 FR 36930, July 20, 1994), applicable to General 
Electric Aircraft Engines (GEAE) CT7 series turboprop engines, to 
require a one-time ultrasonic inspection of the propeller shaft flange 
outer diameter (OD) fillet radius and inner diameter (ID) bore on a 
suspect population of propeller shafts for subsurface metallurgical 
defects, and if necessary, replacement with a serviceable part. That 
action was prompted by the determination that certain propeller shafts 
may have a metallurgical defect that could cause separation of the 
propeller from the propeller shaft. The FAA's investigation has 
revealed this population of propeller shafts may contain a 
metallurgical defect known as a pipe inclusion, which developed during 
manufacture of the shaft. This defect typically forms during the 
process of melting the ingot used to form the shaft and positions 
itself at either end of the ingot. During this phase of the 
manufacturing process cropping both ends of the ingot normally ensures 
complete removal of such defects. The FAA has determined, however, that 
for five heat lots of material, pipe inclusions may not have been 
completely removed from the material used to form the propeller shaft. 
The FAA has determined that suspect material was used to manufacture 
approximately 326 propeller shafts.
    The FAA received a report of a propeller separating from a SAAB 
Aircraft S340 series aircraft inflight following severe vibration. The 
FAA's investigation revealed that the propeller shaft separated due to 
a pipe inclusion defect positioned in a high stress location of the 
propeller shaft. That defect initiated a crack which propagated to 
failure. This condition, if not corrected, could result in failure of 
the propeller shaft, which can result in separation of the propeller 
from the propeller shaft and possible damage to the aircraft.
    Since the issuance of that AD, the FAA has determined that 
ultrasonic inspection equipment was assumed to be more available than 
has proven to be, based on input received by the manufacturer. The 
manufacturer reported that there are many operators that would 
experience difficulty gaining access to the ultrasonic inspection 
equipment in a timely manner given the current AD's compliance 
requirements, which could result in unscheduled grounding of aircraft. 
Therefore, the FAA is extending the compliance time for ultrasonic 
inspection of those propeller shafts first identified by borescope 
inspection in paragraph (b) of this AD to be suspect. In the current 
AD, paragraph (b) requires operators to ultrasonically inspect suspect 
propeller shafts identified by borescope inspection prior to further 
flight. This supersedure will extend the compliance time for ultrasonic 
inspection to the next shop visit following the borescope inspection, 
or October 31, 1994, whichever occurs first. This compliance time is 
identical to the compliance time described in paragraph (a) of this AD, 
applicable to propeller shafts already suspected to have a 
metallurgical defect. By matching the compliance time of paragraph (b) 
of this AD to paragraph (a) of this AD, there is no reduction in the 
level of airworthiness of the inspection requirements of this AD.
    In addition, the FAA has revised the shop visit definition 
described in paragraph (c) of this AD to eliminate the separation of 
propeller criterion, which could lead to forced unscheduled ultrasonic 
inspections of the propeller shaft without ultrasonic inspection 
equipment available, and to specify the induction of the propeller 
gearbox into the overhaul shop rather than the engine, because it is 
not necessary to remove the engine to perform the inspections required 
by this AD.
    The FAA has reviewed and approved the technical contents of GEAE 
(CT7-TP Series) Service Bulletin (SB) No. A72-350, Revision 3, dated 
June 8, 1994, that describes procedures for a one-time ultrasonic 
inspection of the propeller shaft flange OD fillet radius and inner 
diameter ID bore for detection of subsurface defects. In addition, 
Table 3 of this SB lists by propeller gearbox serial number (S/N) a 
certain population of suspect propeller shafts to be identified by 
internal markings during a one-time borescope inspection. Those 
propeller shafts with markings identified as suspect in accordance with 
this SB must be ultrasonically inspected the next shop visit following 
the borescope inspection, or October 31, 1994, whichever occurs first. 
Since the inspection procedures have not changed in Revision 3 of GEAE 
(CT7-TP Series) SB No. A72-350, inspections performed in accordance 
with previous revisions of this SB constitute acceptable alternate 
methods of compliance to the inspections required by this AD.
    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 94-15-01 to require a one-time ultrasonic inspection of 
the propeller shaft flange OD fillet radius and ID bore on a suspect 
population of propeller shafts for subsurface metallurgical defects, 
and if necessary, replacement with a serviceable part. The actions are 
required to be accomplished in accordance with the service bulletin 
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 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 94-ANE-07.'' 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. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing Amendment 39-8972, (59 FR 
36930, July 20, 1994), and by adding a new airworthiness directive, 
Amendment 39-9011, to read as follows:

94-17-16  General Electric Aircraft Engines: Amendment 39-9011. 
Docket 94-ANE-07. Supersedes AD 94-15-01, Amendment 39-8972.

    Applicability: General Electric Aircraft Engines (GEAE) Models 
CT7-5A2, -5A3, -7A, -7A1, -9B, -9B1, -9B2, -9C, -9D turboprop 
engines, with propeller gearboxes listed by serial number in GEAE 
(CT7-TP Series) Service Bulletin (SB) No. A72-350, Revision 3, dated 
June 8, 1994. These engines are installed on but not limited to 
Construcciones Aeronauticas, SA (CASA) and Industri Pesawat Terbang 
Nusantara (IPTN) CN-235 series and SAAB Aircraft S340 series 
aircraft.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the propeller shaft, which can result in 
separation of the propeller from the propeller shaft and possible 
damage to the aircraft, accomplish the following:
    (a) Perform a one-time ultrasonic inspection of the propeller 
shaft flange outer diameter (OD) fillet radius and inner diameter 
(ID) bore for subsurface metallurgical defects, and replace 
defective propeller shafts with serviceable parts, at the next shop 
visit after the effective date of this AD, or prior to October 31, 
1994, whichever occurs first. Perform the ultrasonic inspection, and 
replace defective propeller shafts with serviceable parts, in 
accordance with GEAE (CT7-TP Series) SB No. A72-350, Revision 3, 
dated June 8, 1994, on propeller shafts listed by propeller gearbox 
serial number (S/N) in Table 2 of that SB.
    (b) At the next shop visit after the effective date of this AD, 
or prior to October 31, 1994, whichever occurs first, perform a one-
time borescope inspection to identify all markings on the propeller 
shaft, in accordance with GEAE (CT7-TP Series) SB No. A72-350, 
Revision 3, dated June 8, 1994, on propeller shafts listed by 
propeller gearbox S/N in Table 3 of that SB; and proceed as follows:
    (1) For those propeller shafts that are determined to be 
suspect, perform a one-time ultrasonic inspection, and replace 
defective propeller shafts with serviceable parts, at the next shop 
visit after the borescope inspection required by paragraph (b) of 
this AD, or October 31, 1994, whichever occurs first, in accordance 
with the Accomplishment Instructions of GEAE (CT7-TP Series) SB No. 
A72-350, Revision 3, dated June 8, 1994.
    (2) For those propeller shafts that are determined not to be 
suspect, no further action is required.
    (c) For the purpose of this AD, a shop visit is defined as the 
induction of the propeller gearbox into the overhaul shop for 
maintenance.
    (d) 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: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from the Engine Certification Office.

    (e) Special flight permits may be issued in accordance with 
Sec. Sec. 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.
    (f) The inspections, and replacement shall be done in accordance 
with the following service documents: 

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                    Document No.                            Pages             Revision              Date        
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GEAE (CT7-TP Series) SB No. A72-350.................               1-40                  3  June 8, 1994.       
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Total pages: 40.                                                                                                

    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 General Electric Aircraft 
Engines, 1000 Western Avenue, Lynn, MA 01910. 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.
    (g) This amendment becomes effective on September 15, 1994. 
Issued in Burlington, Massachusetts, on August 16, 1994.
Mark C. Fulmer,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 94-20591 Filed 8-30-94; 8:45 am]
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