Airworthiness directives: Pratt & Whitney,

[Federal Register: August 31, 1998 (Volume 63, Number 168)]

[Proposed Rules]

[Page 46200-46202]

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

[DOCID:fr31au98-19]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-28-AD]

RIN 2120-AA64

Airworthiness Directives; Pratt & Whitney JT9D Series 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 certain Pratt & Whitney (PW) JT9D series turbofan engines. This proposal would require a fluorescent penetrant inspection (FPI) of the rear skirt of the diffuser case for cracks, and, if necessary, blending down to minimum wall thickness to remove cracks and subsequent FPI to determine if cracks have been removed, polishing, and shotpeening. If the cracks are shown by subsequent FPI not to have been removed, this proposed AD would require removing the diffuser case from service and replace with a serviceable part. This proposal is prompted by a report of a diffuser case rupture during takeoff roll that resulted in damage to the aircraft. The actions specified by the proposed AD are intended to prevent diffuser case rupture due to cracks, which can result in an uncontained engine failure and damage to the aircraft.

DATES: Comments must be received by October 30, 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-28-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.

The service information referenced in the proposed rule may be obtained from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone (860) 565-6600, fax (860) 565-4503. 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: Tara Goodman, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (781) 238-7130, fax (781) 238-7199.

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-28-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-28-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

The Federal Aviation Administration (FAA) received a report of a diffuser case rupture on a Pratt & Whitney (PW)

[[Page 46201]]

Model JT9D-7Q turbofan engine. The diffuser case rupture occurred when the engine was at takeoff power at the beginning of takeoff roll. As a result of the diffuser case rupture both engine side cowl doors, a precooler, and other hardware were ejected from the engine. The escaping gas and engine debris blew out the engine pylon access panels, and created holes, cracks, and other damage to the wing's leading edge, aileron, and flaps. The investigation revealed the diffuser case fracture was due to a crack that most likely developed in a toolmark in the case outer pressure wall in the rear skirt area, adjacent to the dog bone-shaped embossment at the 11 o'clock circumferential location. Extensive investigation could not determine the source of the excitation that caused the crack to progress in a high cycle fatigue mode. This condition, if not corrected, could result in diffuser case rupture due to cracks, which can result in an uncontained engine failure and damage to the aircraft.

The FAA has reviewed and approved the technical contents of PW Service Bulletin (SB) No. JT9D-6329, dated May 20, 1998, that describes inspection and rework procedures for cracks.

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 a fluorescent penetrant inspection (FPI) of the rear skirt of the diffuser case for cracks, and, if necessary, blending down to minimum wall thickness, to remove cracks, subsequent FPI to determine if cracks have been removed, and polishing and shotpeening. If the cracks are shown by subsequent FPI not to have been removed, this proposed AD would require removing the diffuser case from service for possible weld repair or replacement with serviceable parts. The actions would be required to be accomplished in accordance with the SB described previously.

There are approximately 566 engines of the affected design in the worldwide fleet. The FAA estimates that 157 engines installed on aircraft of U.S. registry would be affected by this proposed AD, that it would take approximately 68 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 $640,560.

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:

   Pratt & Whitney: Docket No. 98-ANE-28-AD.

   Applicability: Pratt & Whitney (PW) Model JT9D-7Q, -7Q3, -59A, and -70A turbofan engines, with diffuser cases, part numbers (P/Ns) 772173, 772173-001, 772173-002, 782222, 782222-001, and 782222-002, installed. These engines are installed on but not limited to Boeing 747 series, McDonnell Douglas DC-10 series, and Airbus A300 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 diffuser case rupture due to cracks, which can result in an uncontained engine failure and damage to the aircraft, accomplish the following:

   (a) At the next piece-part exposure of the diffuser case after the effective date of this AD, accomplish the following in accordance with PW Service Bulletin (SB) No. JT9D-6329, dated May 20, 1998:

   (1) Perform a fluorescent penetrant inspection (FPI) in accordance with the procedures and criteria stated in the SB of the areas around the dog bone-shaped bosses in the diffuser case rear skirt identified in the SB for cracks.

   (2) If no indications of cracks are found in accordance with the procedures and criteria stated in the SB, no further action is required.

   (3) If indications of cracks are found in accordance with the procedures and criteria stated in the SB, remove the diffuser case from service, replace with a serviceable part, or blend the cracks as needed down to the minimum wall thickness to remove cracks in accordance with the procedures and criteria stated in the SB.

   (4) After blending down in accordance with the procedures and criteria stated in the SB, perform a subsequent etch and FPI for cracks, as follows:

   (i) If no indications of cracks are found in accordance with the procedures and criteria stated in the SB, polish and shot-peen the area around each dog bone boss in accordance with the procedures and criteria stated in the SB.

   (ii) If indications of cracks are found in accordance with the procedures and criteria stated in the SB, remove the diffuser case from service and replace with a serviceable part.

   (b) For the purpose of this AD, piece-part exposure is defined as when the part is considered completely disassembled when done in accordance with the disassembly instructions in the engine manufacturer's maintenance manual, to give access to the dog bone- shaped bosses in the diffuser case rear skirt.

   (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, Engine 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, Engine Certification Office.

   Note 2: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office.

   (d) Special flight permits may be issued in accordance with sections 21.197 and 21.199

   [[Page 46202]]

   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 August 25, 1998. Jay J. Pardee, Manager, Engine and Propeller Directorate, Aircraft Certification Service.

   [FR Doc. 98-23360Filed8-28-98; 8:45 am]

   BILLING CODE 4910-13-U