[Federal Register Volume 61, Number 57 (Friday, March 22, 1996)]
[Proposed Rules]
[Pages 11790-11792]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-6972]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 95-ANE-55]
Airworthiness Directives; AlliedSignal Inc. TFE731 Series
Turbofan Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This document proposes the adoption of a new airworthiness
[[Page 11791]]
directive (AD) that is applicable to AlliedSignal Inc. (formerly
Garrett Engine Division) TFE731 series turbofan engines. This proposal
would require removing certain fan rotor disks from service in
accordance with a drawdown schedule, and would establish new fan rotor
disk life limits. This proposal is prompted after additional analyses
revealed that stress levels in the fan rotor disk dovetail slots for
the applicable engine models are higher than initially calculated. The
actions specified by the proposed AD are intended to prevent
uncontained failure of the fan rotor disk due to fatigue cracking in
the dovetail slots, which can result in inflight engine shutdowns,
severe secondary damage, and fan rotor assembly separation from the
engine.
DATES: Comments must be received by May 21, 1996.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), New England Region, Office of the Assistant Chief
Counsel, Attention: Rules Docket No. 95-ANE-55, 12 New England
Executive Park, Burlington, MA 01803-5299. Comments may be inspected at
this location between 8:00 a.m. and 4:30 p.m., Monday through Friday,
except Federal holidays.
The service information referenced in the proposed rule may be
obtained from AlliedSignal Aerospace, Attn: Data Distribution, M/S 64-
3/2101-201, P.O. Box 29003, Phoenix, AZ 85038-9003; telephone (602)
365-2493, fax (602) 365-5577. This information may be examined at the
FAA, New England Region, Office of the Assistant Chief Counsel, 12 New
England Executive Park, Burlington, MA.
FOR FURTHER INFORMATION CONTACT: Joseph Costa, Aerospace Engineer, Los
Angeles Aircraft Certification Office, FAA, Transport Airplane
Directorate, 3960 Paramount Blvd., Lakewood, CA 90712-4137; telephone
(310) 627-5246; fax (310) 627-5210.
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 notice 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 notice must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 95-ANE-55.'' The postcard will be date stamped and
returned to the commenter.
Availability of NPRMs
Any person may obtain a copy of this NPRM by submitting a request
to the FAA, New England Region, Office of the Assistant Chief Counsel,
Attention: Rules Docket No. 95-ANE-55, 12 New England Executive Park,
Burlington, MA 01803-5299.
Discussion
The Federal Aviation Administration (FAA) has received reports of
three fan rotor disk separations on AlliedSignal Inc. (formerly Garrett
Engine Division) TFE731 series turbofan engines. The FAA has determined
from subsequent analyses that stress levels in the disk dovetail slots
installed are higher than initially calculated. Also, recent review of
fan rotor disk dovetail slot eddy-current inspection data from TFE731-2
and -3 series engines has indicated that crack detectability is between
80-90 percent, not as high as previously evaluated. To date, eddy-
current inspections have detected fatigue cracks in the dovetail slot
in approximately 176 (or 4%) of TFE731-2, -2A, -3, and -3R disks and in
8 (or 1%) of TFE731-3A, -3A, -3B, -3B, 3C, -3CR, and -4R disks and have
been removed from service. The FAA concluded that a reduction in the
fan rotor disk service life limit is necessary to maintain an
acceptable level of safety. This condition, if not corrected, could
result in an uncontained failure of the fan rotor disk due to fatigue
cracking in the dovetail slots, which can result in inflight engine
shutdowns, severe secondary damage, and fan rotor assembly separation
from the engine.
The FAA has reviewed and approved the technical contents of
AlliedSignal Engines Alert Service Bulletin (ASB) No. TFE731-A72-3569,
dated May 31, 1995, and ASB No. TFE731-A72-3570, dated May 31, 1995,
that describe removing certain fan rotor disks from service in
accordance with a drawdown schedule. These new life limits will be
included subsequently in AlliedSignal Engines Service Bulletin (SB) No.
TFE731-72-3001 and SB No. TFE731-72-3501.
Since an unsafe condition has been identified that is likely to
exist or develop on other products of this same type design, the
proposed AD would require removing certain fan rotor disks from service
in accordance with a drawdown schedule and would establish new fan
rotor disk life limits. The actions would be required to be
accomplished in accordance with the ASB's described previously.
There are approximately 5,000 engines of the affected design in the
worldwide fleet. The FAA estimates that 2,500 engines installed on
aircraft of U.S. registry would be affected by this proposed AD, that
it would take approximately 16 work hours per engine to accomplish the
proposed actions, and that the average labor rate is $60 per work hour.
Based on these figures, the total cost impact of the proposed AD on
U.S. operators is estimated to be $2,400,000.
The regulations proposed herein would 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
proposal would not have sufficient federalism implications to warrant
the preparation of a Federalism Assessment. 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.
[[Page 11792]]
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 USC 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
AlliedSignal Inc.: Docket No. 95-ANE-55.
Applicability: AlliedSignal Inc. (formerly Garrett Engine
Division) Models TFE731-2, -2A, -3, -3A, -3AR, -3B, -3BR, -3C, -3CR,
-3D, -3DR, -3R, and -4R turbofan engines, installed on, but not
limited to the following aircraft: Avions Marcel Dassault Falcon 10,
50, 100 series; Learjet 31, 35, 36, and 55 series; Lockheed-Georgia
1329-23 and -25 series; Israel Aircraft Industries 1124 series and
1125 Westwind series; Cessna Model 650, Citations III, VI, and VII;
Raytheon British Aerospace HS-125 series; and Sabreliner NA-265-65.
Note: 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 use the
authority provided in paragraph (d) to request approval from the
Federal Aviation Administration (FAA). This approval may address
either no action, if the current configuration eliminates the unsafe
condition, or different actions necessary to address the unsafe
condition described in this AD. Such a request should include an
assessment of the effect of the changed configuration on the unsafe
condition addressed by this AD. In no case does the presence of any
modification, alteration, or repair remove any engine from the
applicability of this AD.
Compliance: Required as indicated, unless accomplished
previously.
To prevent uncontained failure of the fan rotor disk due to
fatigue cracking in the dovetail slots, which can result in inflight
engine shutdowns, severe secondary damage, and fan rotor assembly
separation from the engine, accomplish the following:
(a) For engines equipped with fan rotor disks, part numbers (P/
N's) 3072162-5, 3073436-5, 3073539-(All), and 3074529-(All), where
(All) denotes any dash number, remove fan rotor disks from service
and install a serviceable disk in accordance with the Accomplishment
Instructions of AlliedSignal Engines Alert Service Bulletin (ASB)
No. TFE731-A72-3569, dated May 31, 1995, as required by the
following schedule:
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Fan rotor disk cycles since new (CSN) on the
effective date of this AD Required fan rotor disk retirement (remove from service)
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3,600 or less....................................... Not to exceed the new life limit of 4,100 CSN.
3,601 to 5, 500..................................... Within the next 500 cycles after the effective date of
this AD or prior to reaching 5,700 CSN, whichever occurs
first.
5,501 or greater.................................... Within the next 200 cycles after the effective date of
this AD, not to exceed 7,100 CSN.
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(b) For engines equipped with fan rotor disks, P/N 3072816-
(All), where (All) denotes any dash number, remove fan rotor disks
from service and install a serviceable disk in accordance with
Accomplishment Instructions of AlliedSignal Engines ASB No. TFE731-
A72-3570, dated May 31, 1995, as required by the following schedule
of CSN after the effective date of this AD.
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Fan rotor disk CSN on the effective date of this AD Required fan rotor disk retirement (remove from service)
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3,850 or less....................................... Not to exceed the new life limit of 4,600 CSN.
3,851 to 6,000...................................... Within the next 750 cycles or prior to reaching 6,500 CSN,
whichever occurs first.
6,001 or greater.................................... Within the next 500 cycles, not to exceed 10,000 CSN.
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(c) A serviceable part is one that has not exceeded the life
limits established by this AD.
(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, Los Angeles Aircraft 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, Los Angeles Aircraft Certification Office.
Note: Information concerning the existence of approved
alternative methods of compliance with this airworthiness directive,
if any, may be obtained from the Los Angeles Aircraft Certification
Office.
(e) 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.
Issued in Burlington, Massachusetts, on March 12, 1996.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification
Service.
[FR Doc. 96-6972 Filed 3-21-96; 8:45 am]
BILLING CODE 4910-13-U