Airworthiness directives: Williams International,

[Federal Register: September 9, 1998 (Volume 63, Number 174)]

[Proposed Rules]

[Page 48140-48141]

From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[DOCID:fr09se98-13]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-36-AD]

RIN 2120-AA64

Airworthiness Directives; Williams International FJ44-1A Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to Williams International FJ44-1A turbofan engines. This proposal would require removing the high pressure turbine (HPT) disk from service prior to accumulating a reduced cyclic life limit of 1,900 cycles since new (CSN) and replacing with a serviceable disk. As an option, the HPT nozzle can be modified thereby increasing the HPT disk cyclic life limit from the new reduced cyclic life limit. This proposal is prompted by a revised life analysis conducted by the manufacturer after the failure of a similarly designed HPT disk. The actions specified by the proposed AD are intended to prevent HPT disk rim failure, which could result in an uncontained engine failure and damage to the aircraft.

DATES: Comments must be received by November 9, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 98-ANE-36-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may also be sent via the Internet using the following address: ``9-ad- engineprop@faa.dot.gov''. 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.

FOR FURTHER INFORMATION CONTACT: Patricia Bonnen, Aerospace Engineer, Chicago Aircraft Certification Office, FAA, Small Airplane Directorate, 2300 East Devon Avenue, Des Plaines, IL 60018; telephone (847) 294- 7134, fax (847) 294-7834.

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 filedin 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 98-ANE-36-AD.'' 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 Regional Counsel, Attention: Rules Docket No. 98-ANE-36-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

Williams International, manufacturer of FJ44-1A turbofan engines, recently conducted a revised life limit analysis of high pressure turbine (HPT) disks, part number (P/N) 55291. This revised analysis was prompted by the failure of a similarly designed HPT disk. The revised analysis revealed that the calculated low cycle fatigue lives are significantly lower than the current published maximum approved service lives. To this date no failures of HPT disk, P/N 55291, have been reported. This condition, if not corrected, could result in HPT disk rim failure, which could result in an uncontained engine failure and damage to the aircraft.

Williams International has also published service information which authorizes certain modifications to the

[[Page 48141]]

HPT nozzle assembly and subsequent reidentification of the HPT disk and assembly. Incorporation of these modifications increases the approved service life limit from the new reduced service life.

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 the HPT disk from service prior to accumulating a reduced cyclic life limit of 1,900 cycles since new (CSN) and replacing with a serviceable disk.

There are approximately 223 engines of the affected design in the worldwide fleet. The FAA estimates that 165 engines installed on aircraft of U.S. registry would be affected by this proposed AD. The cost of removing a disk earlier than the original life-limit rather than reworking the disk is $12,546 per engine. The costs of reworking the HPT nozzle assembly to obtain increased HPT life are substantially less than the costs of replacement of the HPT disk. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $2,070,090 assuming all disks are replaced. The actual total cost to U.S. operators, however, will be less depending on how many operators exercise the rework option. In addition, the manufacturer may reimburse operators for the costs of removing disks earlier than the original life limit reducing even further the total cost impact for U.S. operators.

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.

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.

   Sec. 39.13 [Amended]

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

   Williams International: Docket No. 98-ANE-36-AD.

   Applicability: Williams International FJ44-1A turbofan engines, installed on but not limited to Cessna 525 series aircraft.

   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 (c) 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 high pressure turbine (HPT) disk rim failure, which could result in an uncontained engine failure and damage to the aircraft, accomplish the following:

   (a) Prior to accumulating 1,900 cycles since new (CSN), remove from service HPT disk, part number (P/N) 55291, and replace with a serviceable part.

   (b) As an option to paragraph (a), modify the HPT nozzle assembly and remark the HPT disk and assembly with new part numbers in accordance with Williams International Service Bulletin FJ44-72- 36, dated October 21, 1997.

   Note 2: The low cycle fatigue retirement lives for the HPT disks remarked with new part numbers in accordance with paragraph (b) of this AD may be found in Williams SB FJ44-A-72-38, dated October 21, 1997.

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

   Note 3: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Chicago Aircraft Certification Office.

   (d) Thereafter, except as provided in paragraph (c) of this AD, no alternative replacement times or life limits may be approved for HPT disk, P/N 55291.

   (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 September 2, 1998. Donald E. Plouffe, Acting Manager, Engine and Propeller Directorate, Aircraft Certification Service.

   [FR Doc. 98-24185Filed9-8-98; 8:45 am]

   BILLING CODE 4910-13-U