[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]
BILLING CODE 4910-13-P
