AD 94-07-03

This amendment supersedes an existing priority letter airworthiness directive (AD), applicable to certain AlliedSignal, Inc. TFE731-2A and -3 series turbofan engines, that currently requires a revision to the Limitations Section of the Airplane Flight Manual (AFM) to provide procedures for monitoring engine performance in order to detect A5 seal cracking and opening before first stage low pressure (LP) turbine disk failure. Additionally, the revision to the AFM requires a procedure for verification of LP rotor (N1) rotation during engine start to detect rotor lockup due to first stage LP turbine rotor creep. This amendment maintains those requirements for engine and flight data monitoring, adds a more stringent procedure for verifying rotor lockup during engine start and for detection of rubbing noises, and requires replacement of A5 seals with a redesigned seal. Replacement of A5 seals with a redesigned seal constitutes terminating action to the monitoring requirements.This amendment is prompted by reports of an additional first stage LP turbine disk failure due to A5 seal cracking. The actions specified by this AD are intended to prevent uncontained failure of the first stage LP turbine disk.

94-07-03 ALLIEDSIGNAL, INC.: Amendment 39-8861. Docket 93-ANE-49. Supersedes priority letter AD 92-12-09.
Applicability: AlliedSignal, Inc. Model TFE731-2A, -3, -3A, -3R, -3AR, -3B, and -3BR turbofan engines that have first stage low pressure (LP) turbine nozzles, Part Number (P/N) 3072842-1 or P/N's 3072319-1 through -8, installed. These engines are installed on but not limited to Avions Marcel Dassault Falcon 50, AiResearch Aviation Company 731 Jetstar, Lockheed 1329-25 (Jetstar II), Israel Aircraft Industries Ltd. 1124 series (Westwind) and 1125 Westwind Astra, British Aerospace DH/HS/BH 125 series, Learjet 55 series, Cessna 650 Citation III series, and Sabreliner NA265-65 (Sabreliner 65 and 65 series) aircraft.
Compliance: Required as indicated, unless accomplished previously.
To prevent uncontained failure of the first stage LP turbine disk, accomplish the following:
(a) Prior to further flight revise the Limitations Section of the FAA-approved Airplane Flight Manual (AFM) to include the following paragraphs (1) through (4) relating to engine and flight data monitoring. This may be accomplished by inserting a copy of this AD in the AFM. "ENGINE AND FLIGHT DATA MONITORING
(1) If any engine has more than 500 hours time in service since new (TSN), record the flight data set forth in paragraph (2) once every two flights while meeting the following conditions:
a. matched low pressure rotor (N1) speed;
b. turn engine anti-ice off (consistent with safe operation); and
c. attain a stabilized cruise speed for five minutes or longer. NOTE: If flight operations do not permit all of these conditions to be met, the engine to engine comparison data may be unreliable.
(2) When the conditions specified in paragraph (1) are met, record the following flight data and retain this data for six months:
a. date of flight;
b. aircraft altitude or flight level;
c. outside static air temperature in degrees celsius ( C);
d. Mach number;
e. engine N1 speed for each engine;
f. engine high pressure rotor (N2) speed for each engine;
g. fuel flow for each engine; and
h. interstage turbine temperature (ITT) for each engine.
(3) Verify N1 rotation during engine start by allowing N2 to increase to approximately 12 to 15 percent and confirm N1 rotation prior to fuel initiation. If no N1 rotation is observed, discontinue further attempts at engine start.
(4) Check for rubbing noises and free rotation of the N1 spool following each engine shutdown. If any rubbing noises are detected, or if the N1 spool locks up, discontinue further flight."
(b) When engine and flight data monitoring is required by the AFM revision of paragraph (a) of this AD, accomplish the following:
(1) After each flight, calculate the difference (i.e., No. 1 minus No. 2, No. 1 minus No. 3, and No. 1 minus No. 4) between the engines' ITT, N2 speed, and fuel flow readings for each flight having recorded data. Compare these differences to the differences calculated from previous flights.
(2) Discontinue further flight if a change of 20?C or more occurs in the ITT difference between two engines, (on three and four engine airplanes compare No. 2, No. 3 and No. 4 engine parameters to the No. 1 engine) with the last ten flights having recorded data. Flight operation can be continued when the cause of the ITT temperature shift has been determined and appropriate corrective action has been accomplished. Engine and flight data monitoring must be continued upon return to flight operations. NOTE: A suspect engine may indicate an increase in ITT temperature and an increase in N2 speed greater than 1% and an increase in fuel flow to a lesser degree with respect to the other normal engine(s).
Additional guidance and information regarding flight data collection, trend monitoring, and corrective actions, may be obtained from Allied-Signal Aerospace Company, Garrett Engine Division, Operating Information Letter No. OI 731-13, Revision C, dated November 20, 1992.
(c) Discontinue further flight if no N1 rotation is observed during engine start, or if engine rubbing noises are detected or the N1 spool locks up after engine shutdown. Flight operation can be continued when the cause of the N1 rotor lockup or engine rubbing noises has been determined and appropriate corrective action has been accomplished. Engine and flight data monitoring must be continued upon return to flight operations.
(d) Replace the A5 seal assembled in affected first stage LP turbine nozzles and install a redesigned A5 seal in accordance with the Accomplishment Instructions of Allied-Signal Aerospace Company, Garrett Engine Division, Service Bulletin (SB) No. TFE731-72-3502, Revision 2, dated March 15, 1993, SB No. TFE731-72- 3502, Revision 1, dated December 21, 1992, or SB No. TFE731-72-3502, Original, dated November 25, 1992; or SB No. TFE731-72-3503, Revision 1, dated December 21, 1992; or AlliedSignal, Inc. SB No. TFE731-72-3509, dated January 4, 1994, as applicable, as follows:

Time in Service Since New (TSN) on the Effective
Date of this AD
Replacement Schedule
500 hours TSN or more
Within 150 hours time in service (TIS) after the effective date of this AD.
Less than 500 hours TSN
Prior to accumulating 650 hours TSN

Installation of the redesigned A5 seal constitutes terminating action to the engine and flight data monitoring and AFM revision required by this AD.
(e) 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 AD, if any, may be obtained from the Los Angeles Aircraft Certification Office.
(f) Special flight permits may be issued in accordance with 14 CFR 21.197 and 21.199 to operate the aircraft to a location where the requirements of this AD can be accomplished.
(g) The replacement of the A5 seal shall be done in accordance with the following service bulletins:

Document No.
Pages
Revision
Date
Allied-Signal
Aerospace Company,
Garrett Engine
Division SB No.
TFE731-72-3502
Total pages: 18.
1-18
2
March 15, 1993
Allied-Signal
Aerospace Company,
Garrett Engine
Division SB No.
TFE731-72-3502
Total pages: 16.
1-16
1
December 21, 1992
Allied-Signal
Aerospace Company,
Garrett Engine
TFE731-72-3502 Division SB No.
Total pages: 14.
1-14
Original
November 25, 1992
Allied-Signal
Aerospace Company,
Garrett Engine
Division SB No.
TFE731-72-3503
1
1
December 21, 1992

2-3
Original
December 9, 1992

4
1
December 21, 1992

5
Original
December 9, 1992

6
1
December 21, 1992

7-9
Original
December 9, 1992
Total pages: 16.
10-16
1
December 21, 1992
AlliedSignal, Inc.
SB No.
TFE731-72-3509
Total pages: 10.
1-10
Original
January 4, 1994

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 AlliedSignal Inc., Aviation Services Division, Data Distribution, Dept. 64-3/2102-1M, P.O. Box 29003, Phoenix, AZ 85038-9003. 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.
(h) This amendment supersedes priority letter AD 92-12-09, issued June 8, 1992.
(i) This amendment becomes effective on June 6, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations by superseding priority letter airworthiness directive (AD) 92-12-09, issued June 8, 1992, which is applicable to certain Allied-Signal Aerospace Company, Garrett Engine Division, TFE731-2A and -3 series turbofan engines, was published in the Federal Register on October 4, 1993 (58 FR 51587). That action proposed to continue the engine and flight data monitoring requirements of priority letter AD 92-12-09 by revising the Limitations Section of the Airplane Flight Manual (AFM) to provide for procedures to trend monitor engine performance in order to detect A5 seal cracking and opening before first stage low pressure (LP) turbine disk failure. In addition, that action proposed to require a more stringent procedure for verifying N1 rotation during engine start to detect rotor lockup and for detecting rubbing noises due to first stage LP turbine rotor creep. Also, that action proposed to add the Allied-Signal Aerospace Company, Garrett Engine Division, Model TFE731-2A engine to the AD applicability. Finally, that action proposed to require replacement of current A5 seals with a redesigned A5 seal within 150 hours time in service after the effective date of the proposed AD. Installation of the redesigned A5 seal would constitute terminating action to the engine and flight data monitoring requirements.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

One commenter states that paragraph (a)(1) in the proposed rule requires that the engine and flight data monitoring must be accomplished for any engine that has more than 500 hours time in service since new (TSN). The commenter further states that the greater than 500 hours TSN qualification should be added to the applicability paragraph, as this qualification is applicable to all succeeding paragraphs. TheFAA concurs in part. The FAA has added for clarity a compliance table in paragraph (d) that instructs operators on the replacement schedule for the A5 seal installed on engines with less or more than 500 hours TSN.

One commenter states that paragraph (a)(4) of the proposed rule requires checking for rubbing noises and free rotation of the N1 spool following each engine shutdown. Paragraphs (a)(4) and (c) go on to state that if any rubbing noises are detected, the operator must discontinue further flight. The commenter suggests requiring discontinuation of further flight if the N1 spool locks up, or engine rubbing noises are detected during this check. The FAA concurs and the final rule has been changed accordingly.

The Type Certification Data Sheet for the Allied-Signal Aerospace Company, Garrett Engine Division, TFE731-3 series turbofan engines was officially changed by the FAA during November 1993 to show the current corporate name of the manufacturer, AlliedSignal, Inc.All references to the corporate name have been changed accordingly in this final rule.

In addition, AlliedSignal, Inc. has issued service bulletin (SB) No. TFE731-72-3509, dated January 4, 1994, that describes installation of a redesigned A5 seal and air cooled HP turbine blades and associated parts for TFE731-3B and -3BR models. Installation of a redesigned A5 seal and air cooled HP turbine blades and associated parts in accordance with this SB constitutes an additional method of compliance to paragraph (d) of this AD.

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

There are approximately 3,300 engines of the affected design in the worldwide fleet. The FAA estimates that 2,000 engines installed on aircraft of U.S. registry are affected by this AD, that it will take approximately 55 work hours per engine to accomplish the proposed actions, and that the average labor rate is $55 per work hour. Required parts will cost approximately $7,500 per engine. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $21,050,000.

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.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it 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 14 CFR part 39 of the Federal Aviation Regulations 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.

39.13 - [AMENDED]
2. Section 39.13 is amended by adding the following new airworthiness directive: