[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:

----------------------------------------------------------------------------------------------------------------
    Fan rotor disk cycles since new (CSN) on the                                                                
              effective date of this AD                Required fan rotor disk retirement (remove from service) 
----------------------------------------------------------------------------------------------------------------
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.                        
----------------------------------------------------------------------------------------------------------------

    (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.

----------------------------------------------------------------------------------------------------------------
 Fan rotor disk CSN on the effective date of this AD   Required fan rotor disk retirement (remove from service) 
----------------------------------------------------------------------------------------------------------------
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.     
----------------------------------------------------------------------------------------------------------------

    (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