AD 95-16-07 ACTIVE

This amendment supersedes an existing airworthiness directive (AD), applicable to Pratt & Whitney JT8D series turbofan engines, that currently requires initial and repetitive inspections of 9th through 12th stage high pressure compressor (HPC) disks at the tierod holes. This amendment eliminates an optional on-wing ultrasonic inspection of the 10th stage high pressure compressor (HPC) disk. This amendment is prompted by a report of an uncontained failure of a 10th stage HPC disk that was previously inspected using the on-wing ultrasonic inspection method. The actions specified by this AD are intended to prevent uncontained fractures of 9th through 12th stage HPC disks and engine failure.

95-16-07 PRATT & WHITNEY: Amendment 39-9327. Docket 81-ANE-03. Supersedes AD 81-08-02 R2, Amendment 39-4817.

Applicability: Pratt & Whitney (PW) JT8D-1, -1A, -7, -7A, -7B, -9, -9A, -11, -15, -15A, -17, -17A, -17R, and -17AR turbofan engines with 9th through 12th stage high pressure compressor (HPC) disks specified in Tables I through V and Table VIII of PW Alert Service Bulletin (ASB) No. 4723, Revision 12, dated March 8, 1990, installed. These engines are installed on but not limited to Boeing 727 series and 737 series, and McDonnell Douglas DC-9 series aircraft. 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 (e) 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 in accordance with PW ASB No. 4723, Revision 9, dated July 13, 1983; Revision 10, dated September 15, 1986; or Revision 11, dated October 30, 1987. All inspections subsequent to the effective date of this AD must be accomplished in accordance with the methods and intervals identified in PW ASB No. 4723, Revision 12, dated March 8, 1990, except as is specified in paragraph (d) of this AD.To prevent uncontained fractures of 9th through 12th stage HPC disks and engine failure, accomplish the following:

(a) Initially inspect 9th through 12th stage HPC disks at the tierod holes in accordance with Tables I through V and Table VIII of PW ASB No. 4273, Revision 12, dated March 8, 1990.

(b) Thereafter, inspect 9th through 12th stage HPC disks at the tierod holes in accordance with Tables I through V and Table VIII of PW ASB No. 4723, Revision 12, dated March 8, 1990. Disks initially inspected prior to the first inspection limit must be reinspected before reaching the specified reinspection interval, or before reaching the first inspection limit, whichever is later. In no case shall the established life limits of the disks be exceeded.

(c) Remove cracked disks from service prior to further flight, and replace with a serviceable part. Disks may be returned to service if repaired in accordance with Paragraph 7 of PW ASB No. 4723, Revision 12, dated March 8, 1990.(d) For 10th stage HPC disks that were last inspected in accordance with the on-wing ultrasonic inspection procedure specified in AD 81-08-02 R2 prior to the effective date of this AD, inspect as follows:

(1) Perform a magnetic particle inspection or eddy current inspection in accordance with the procedure defined in Paragraph 6 and Appendix B of PW ASB No. 4723, Revision 12, dated March 8, 1990, no later than 750 cycles in service (CIS) since the last on-wing inspection.

(2) Accomplish all subsequent inspections in accordance with the methods and intervals specified in PW ASB No. 4723, Revision 12, dated March 8, 1990.

(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, Engine 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, Engine Certification Office. NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Engine Certification Office.

(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.

(g) The actions required by this AD shall be done in accordance with the following ASB:

Document No.
Pages
Rev.
Date
PW ASB No. 4723
1
12
March 8, 1990

2-8
10
September 15, 1986

9-10
11
October 30, 1987

11-25
10
September 15, 1986
Appendix A
A-1
10
September 15, 1986

A-2

(blank)
Appendix B
B-1- B-9
7
February 16, 1981

B-10
8
July 9, 1982

B-11 - B-12
7
February 16, 1981
Total pages: 38.

This incorporation by reference was approved by the Director of the Federal Register in accordance with5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Pratt & Whitney, Technical Publications Department, M/S 132-30, 400 Main Street, East Hartford, CT 06108. 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 becomes effective on September 11, 1995.

On February 7, 1984, the Federal Aviation Administration (FAA) issued airworthiness directive (AD) 81-08-02 R2, Amendment No. 39-4817 (49 FR 7361; February 29, 1984), to require initial and repetitive inspections of 9th through 12th stage high pressure compressor (HPC) disks at the tierod holes in Pratt & Whitney (PW) JT8D series turbofan engines. That action was prompted by cracks in the tierod holes in HPC disks that resulted in engine failures. That condition, if not corrected, can result in uncontained fractures of 9th through 12th stage HPC disks and engine failure.

On August 30, 1984, the FAA issued a correction to AD 81-08-02 R2, Amendment 39-4817 (49 FR 35618; September 11, 1984), to include an engine model that had been inadvertently omitted from the AD.

Since issuance of AD 81-08-02 R2, the FAA received a report of an uncontained fracture of a 10th stage HPC disk. This disk had been subjected to three previous on-wing ultrasonic inspections prior to fracture. This method has since been determined as inadequate for detecting tierod hole cracking.

On May 8, 1989, the FAA issued a notice of proposed rulemaking (NPRM) that was published in the Federal Register (54 FR 22306; May 23, 1989), that would have amended the existing AD by eliminating the optional on-wing ultrasonic inspection of the 10th stage HPC disk, and by including an engine model inadvertently omitted.

Since the issuance of that NPRM, the FAA has determined that the reference to the inadvertently omitted engine model was unnecessary, as the FAA had remedied this discrepancy in the August 30, 1984, correction. Also, the FAA now utilizes a revised format that supersedes existing AD's by publishing a complete document rather than only amending applicable paragraphs of the compliance section. Since the FAA changed the format of the proposed rule, the FAA determined that it was desirable to reopen the comment period to provide additional opportunity for public comment.

A Supplementary NPRM was published in the Federal Register on December 19, 1994 (59 FR 65281). That action reprints the corrected AD compliance section text in its entirety for clarity.

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

The commenter states no objection to adoption of the proposed rule.

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 as proposed.

There are approximately 200 engines that are affected by this AD, and the FAA has determined that eliminating the optional on-wing ultrasonic inspection will have negligible economic impact, since most operators use uninstalled tenth stage disk inspections.

The regulations adopted herein will not have substantial direct effects on the States, onthe 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 in14 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 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), 40101, 40113, 44701.

39.13 - [AMENDED]
2. Section 39.13 is amended by removing Amendment 39-4817 (49 FR 35618, September 11, 1984) and by adding a new airworthiness directive, Amendment 39-9327, to read as follows:

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of September 11, 1995.

ADDRESSES: The service information referenced in this AD may be obtained from Pratt & Whitney, Technical Publications Department, M/S 132-30, 400 Main Street, East Hartford, CT 06108. This information may be examined at the Federal Aviation Administration (FAA), New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA 01803-52

Mark A. Rumizen, Aerospace Engineer Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (617) 238-7137; fax (617) 238-7199.