00-5460. Airworthiness Directives; Honeywell International Inc. TFE731-2, -3, -4, and -5 Series Turbofan Engines

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Supplemental notice of proposed rulemaking; reopening of comment period.

SUMMARY:

This notice revises an earlier proposed airworthiness directive (AD), applicable to Honeywell International, Inc.(formerly AlliedSignal Inc. and Garret Turbine Engine Company) high pressure compressor (HPC) impellers installed on TFE731-2, -3, -4, and -5 series turbofan engines. That proposal would have required replacing the HPC impeller with a serviceable impeller that has been eddy-current inspected or with a serviceable impeller of certain part numbers as a terminating action. That proposal was prompted by an incident of an uncontained impeller failure due to cracking in the seal relief area of the HPC impeller. This action revises the proposed rule by eliminating the terminating action and adding those impeller PN's to the suspect impeller population. This action would also clarify certain portions of the proposed AD based on comments that were received from the public. The actions specified by this proposed AD are intended to prevent HPC impeller failure due to fatigue cracking.

DATES:

Comments must be received by May 8, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 99-ANE-10-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may also be sent via the Internet using the following address: “[e-mail].” Comments sent via the Internet must contain the docket number in the subject line. 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 Honeywell Engines and Systems (formerly AlliedSignal) Technical Publications and Distribution, M/S 2101-201, P.O. Box 52170, Phoenix, AZ 85072-2170; telephone

[phone] (General Aviation), [phone] (Commercial), fax [phone] (General Aviation), [phone] (Commercial). This information may be examined at the FAA, New England Region, Office of the Regional 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 [phone], fax [phone].

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 99-ANE-10-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRM's

Any person may obtain a copy of this NPRM by submitting a request to the FAA, New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 99-ANE-10-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to add an airworthiness directive (AD), applicable to Honeywell International Inc. (formerly AlliedSignal Inc. and Garrett Turbine Engine Company) high pressure compressor (HPC) impellers installed on TFE731-2, -3, -4, and -5 series turbofan engines, was published as a notice of proposed rulemaking (NPRM) in the Federal Register on July 28, 1999 (64 FR 40789). That NPRM would have required replacing the HPC impeller with a serviceable impeller, which has been eddy-current inspected, at the next core zone inspection (CZI) or at the next access to the HPC module, and repetitive inspections at each subsequent CZI or each subsequent access to the HPC impeller for cause if the impeller has more than 1,000 cycles since the last eddy current inspection (ECI). That NPRM was prompted by a Federal Aviation Administration (FAA) determination that on May 10, 1998, a high pressure compressor (HPC) impeller, part number (P/N) 3073394-1, separated and exited from a TFE731-3R-1D turbofan engine. This impeller had accumulated 9,080 engine cycles since new (CSN) and 5,829 engine cycles since rework of the seal relief area in November, 1982, performed in accordance with Garrett Turbine Engine Company Service Bulletin (SB) TFE731-72-3239 RWK. Fracture analysis revealed a subsurface primary origin in the area of the seal relief and that the crack propagated through the bore for about 1.0 inch. No melt or forging related discrepancies were found at the fatigue origin; however, localized alpha grain colonies with an unfavorable fracture plane orientation were present. Recent low-temperature fatigue testing with a sustained peak hold time (dwell) at higher than engine-operating stresses indicate that normal cyclic fatigue lives may be influenced by dwell times and an unfavorable titanium macrostructure. The FAA has determined that low-cycle fatigue (LCF) cracking in high stressed areas of the HPC impeller may lead to an uncontained impeller separation. That condition, if not corrected, could result in an HPC impeller failure due to fatigue cracking.

Changes to This NPRM

Since that NPRM was published in the Federal Register, the FAA has received a number of comments that change the requirements of the original NPRM and the population of applicable HPC impellers was increased. The nature and extent of those changes were such that FAA has determined that a supplemental NPRM (SNPRM) should be issued.

Manufacturer's Service Information

The FAA has reviewed and approved the technical contents of AlliedSignal Inc. Alert Service Bulletin (ASB) TFE731-A72-3641, dated November 24, 1998, that describes procedures for removing, inspecting, and, if necessary, replacing HPC impellers, P/N's 3073393-1, 3073394-1, 3073433-1, 3073434-1 with serviceable impellers. The FAA has subsequently reviewed and approved ASB TFE731-A72-3641, Revision 1, dated October 20, 1999, that adds P/N's 3073398-All (where All denotes all dash numbers), 3073435-All, and 3075171-All.

Proposed Requirements of This AD

Since an unsafe condition has been identified that is likely to exist or develop on other engines of the same type design, this AD is being issued to prevent failure of the HPC impeller due to fatigue cracks. This AD requires removing and inspecting the HPC impeller, and if necessary, replacing the HPC impeller with a serviceable impeller. The removal and inspection will be conducted at the next CZI or at the next access to the HPC module, and repetitive inspections at each subsequent CZI or each subsequent access to the HPC module if the impeller has more than 1,000 cycles since the last ECI. These removals, inspections, and replacements must be done in accordance with the ASB described previously.

Comments About the Original NPRM

Since the issuance of that NPRM, the FAA has received the following four comments:

Request To Eliminate the Terminating Action Paragraph

The manufacturer comments that paragraph (d) of the proposal should be deleted and recommends adding those HPC impellers identified as constituting terminating action to the applicability of the AD. During further investigation, all HPC impeller designs were found to be at risk of fatigue cracking from the same cause, and, therefore, warrant the proposed ECI. The FAA agrees. Paragraph (d) has been deleted from this supplemental NPRM (SNPRM) and HPC impellers P/N's 3073398-All, 3073435-All, and 3075171-All have been added to the applicability of the AD. At present, therefore, the proposal does not offer any terminating action to the required inspections. The FAA may undertake further rulemaking to terminate the ECI requirement.

Replace vs. Inspect

The manufacturer also requests that proposed paragraphs (a) and (b) be reworded to state that operators must inspect the HPC impellers rather than replace the HPC impellers. The manufacturer believes that the use of the word replace may imply that operators must replace the HPC impeller with a new impeller at each time an inspection is required. The FAA agrees in part. As stated in the NPRM, only Honeywell International or persons trained by Honeywell International are properly equipped and qualified to perform this specialized ECI. The Service Bulletin directs operators to remove the HPC impeller and ship the impeller to a facility that can perform the inspection.

Using the words remove and inspect more accurately describe the actions the FAA is requiring of operators. The FAA has added a provision to both paragraphs (a) and (b), however, that operators must remove and inspect, and if necessary replace, applicable HPC impellers with “serviceable” impellers, and added a new paragraph (d) that defines “serviceable” as an impeller which complies with all applicable visual, dimensional, and fluorescent penetrant inspections requirements for the level of maintenance being accomplished, as contained in the Heavy Maintenance Manual and is either an impeller with fewer than 1000 engine operation cycles since new or an impeller with less than 1000 engine operation cycles since last ECI.

Request To Change Note 2 of the NPRM

The manufacturer suggests that the words “Introduction of” should be deleted from proposed Note 2 following proposed paragraph (d). The FAA has already deleted paragraph (d) in response to the manufacturer's earlier comment, and therefore Note 2 has also been deleted in its entirety.

Request To Change the Unsafe Condition Statement

The manufacturer believes that the unsafe condition statements in the preamble and text of the NPRM that describes the intent of the AD should be changed. The commenter states that the AD does not prevent fatigue cracking of the HPC impeller, but rather is intended to detect fatigue cracking of the impeller. The FAA agrees in part. The unsafe condition identified as the underlying justification for this AD is failure of the HPC impeller due to fatigue cracking. The actions required by the AD are not intended to prevent the HPC from cracking, but to prevent the HPC impeller from failing, which could result in an uncontained engine failure, and damage to the airplane. Therefore, the preamble and text of this SNPRM has been changed to read that the AD is issued to prevent HPC impeller failure due to fatigue cracking.

Since these changes expand the scope and cost of the originally proposed rule, the FAA has determined that it is necessary to reopen the comment period to provide additional opportunity for public comment.

There are approximately 7510 engines of the affected design in the worldwide fleet. The FAA estimates that 5482 engines installed on aircraft of U.S. registry would be affected by this proposed AD, that it would take approximately 3 work hours per engine to accomplish the proposed actions, and that the average labor rate is $60 per work hour. The FAA also estimates that some of the impellers will be replaced, and that the impeller will cost about $45,000. Based on these figures, the FAA estimates the total cost impact of the proposed AD on U.S. operators for the next four years to be $2,201,760.

Regulatory Impact

The regulations adopted herein will not have a substantial direct effect 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, it is determined that this final rule does not have federalism implications under Executive Order (EO) 13132.

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

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 U.S.C. 106(g), 40113, 44701.

§ 39.13

[Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

Honeywell International Inc. TFE731-2, -3, -4, and -5 Series Turbofan Engines: Docket No. 99-ANE-10-AD.

Applicability: Honeywell International Inc. (formerly AlliedSignal Inc. and Garrett Turbine Engine Company) TFE731-2, -3, -4, and -5 series turbofan engines with high pressure compressor (HPC) impeller part numbers (P/N's) 3073393-1, 3073394-1, 3073433-1, 3073434-1, 3073398-All (where All denotes all dash numbers), 3073435-All, and 3075171-All, installed on, but not limited to, Avions Marcel Dassault—Breguet Aviation (AMD/BA) Falcon 10, Dassault Aviation Mystere—Falcon 50, and 900 series airplanes; Dassault Aviation Mystere—Falcon 20 series airplanes, Learjet Inc. Models 31, 35, 36, and 55 series airplanes; Lockheed-Georgia Corporation 1329-23 and -25 series airplanes; Israel Aircraft Industries Ltd. 1124 series and 1125 Westwind series airplanes; Cessna Aircraft Co. Model 650 Citation III, VI, and VII series airplanes; Raytheon Aircraft Co. HS-125 series airplanes; and Sabreliner Corporation NA-265-65 airplanes.

Note 1:

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 request approval for an alternative method of compliance in accordance with paragraph (e) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of the high pressure compressor impeller due to fatigue cracking, accomplish the following:

(a) Remove and inspect the applicable HPC impeller in accordance with Section 2.A. of the Accomplishment Instructions of AlliedSignal Inc. Alert Service Bulletin (ASB) TFE731-A72-3641, Revision 1, dated October 20, 1999, or ASB TFE731-A72-3641 dated November 24, 1998, and if necessary, replace the impeller with a serviceable impeller, at the earlier of the following:

(1) At the next core zone inspection (CZI) after the effective date of this AD, or

(2) At the next access to the HPC module after the effective date of this AD.

(b) Thereafter, remove and inspect the applicable HPC impeller in accordance with Section 2.A. of the Accomplishment Instructions of ASB TFE731—A72-3641 dated November 24, 1998, or ASB TFE731-A72-3641, Revision 1, dated October 20, 1999, and if necessary, replace the impeller with a serviceable impeller, whenever either of the following conditions are met:

(1) At every CZI, or

(2) At access to the HPC module if the impeller has accumulated more than 1,000 cycles since the last Eddy Current Inspection (ECI).

(c) This AD defines access to the HPC module as whenever the low pressure compressor case is removed from the compressor interstage diffuser.

(d) For the purposes of this AD, a serviceable impeller is defined as an impeller which complies with all applicable visual, dimensional, and fluorescent penetrant inspections requirements for the level of maintenance being accomplished, as contained in the Heavy Maintenance Manual and is either an impeller with fewer than 1000 engine operation cycles since new or an impeller with less than 1000 engine operation cycles since last ECI.

(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 (LAACO). Operators shall submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, LAACO.

Note 2:

Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the LAACO.

(f) 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 1, 2000.

Diane S. Romanosky,

Acting Manager, Engine and Propeller Directorate, Aircraft Certification Service.