AD 99-20-04

This amendment adopts a new airworthiness directive (AD), applicable to Pratt & Whitney JT9D-7R4 series turbofan engines, that requires an initial and repetitive inspections of certain High Pressure Turbine (HPT) stage 1 and stage 2 disks utilizing an improved ultrasonic inspection method performed at an approved facility when the disks are exposed during a shop visit, and if a crack indicating a subsurface anomaly is found, removal from service and replacement with a serviceable part. This amendment is prompted by the results of a stage 1 HPT disk fracture investigation which has identified a population of HPT stage 1 and 2 disks that may have subsurface anomalies formed during the forging process. The actions specified by this AD are intended to prevent an HPC disk fracture, which could result in an uncontained engine failure, damage to the airplane, and an in-flight engine shutdown.
The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of October 29, 1999.

Final rule.

99-20-04 PRATT & WHITNEY: Amendment 39-11334; Docket 99-NE-06 AD. Issued September 16, 1999.
Applicability: Pratt & Whitney JT9D-7R4 series turbofan engines, installed on but not limited to Boeing 747, Airbus A300 and Airbus A310 series 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 (d) 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 a high pressure compressor (HPC) disk failure, which could result in an uncontained engine failure, damage to the airplane, and an in-flight engine shutdown, accomplish the following:
(a) For engines with a HPT stage 1 or stage 2 disk installed that has a serial number listed in the Accomplishment Instructions section of PW Service Bulletin (SB) JT9D-7R4-72-553, Revision 1, dated February 17, 1999, perform initial and repetitive ultrasonic inspections in accordance with PW SB JT9D-7R4-72-553, Revision 1, dated February 17, 1999 at each separation of the HPT disk piece part accessibility after the effective date of this AD. The disk must be sent to an approved facility listed in the Vendor Services or Special Components/Materials section of PW SB JT9D-7R4-72-553, dated February 17, 1999, for ultrasonic inspection.
(b) Remove from service those HPT disks found with a crack indicating a subsurface anomaly and replace with a serviceable part.
(c) For engines that do not have a HPT stage 1 or Stage 2 disk installed that has a serial number listed in the Accomplishment Instructions section of PW SB JT9D-7R4-72-553, Revision 1, dated February 17, 1999, no inspections are required.
Alternate Method Of Compliance
(d) 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 requests 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. Special Flight Permits
(e) Special flight permits may be issued in accordance with 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.
Incorporation by Reference
(f) The inspection shall be done in accordance with of PW SB JT9D-7R4-72-553, Revision 1, dated February 17, 1999. 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 Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone (860) 565-8770, fax (860) 565-4503. Copies may be inspected at the FAA, New England Region, Office of the Regional 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.
(g) This amendment becomes effective on October 29, 1999.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to Pratt & Whitney (PW) JT9D-7R4 series turbofan engines was published in the Federal Register on June 4, 1999 (64 FR 29965). That action proposed to require initial and repetitive inspections of certain stage 1 and stage 2 high pressure turbine (HPT) disks using an improved ultrasonic method whenever the disk is exposed during a shop visit. The inspection must be performed at an approved facility listed in PW Service Bulletin (SB) JT9D-7R4-72-553, Revision 1, dated February 17, 1999. If a crack indicating a subsurface anomaly is found, the disk must be removed from service and replaced with a serviceable part.
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comment received. Request to Shorten the Inspection IntervalsOne commenter requests that the initial and repetitive inspection intervals be shortened to six to nine months. The commenter maintains that the proposed interval for inspections (exposure during a shop visit) could permit flawed disks to remain on an airplane for a year or more before detection. The FAA does not agree. The compliance interval selected yields an extremely low risk level. The corrected risk is extremely low and a small fraction of the risk allowed by FAA guidelines. Shortening the compliance interval to the recommended level will place an unnecessary burden on the airline industry with little impact on fleet safety. The FAA feels that the current compliance plan is sufficient to maintain flight safety.
The AD was edited to clarify the shipping requirements discussed in the financial assessment in the compliance section. Due to the complexity of the ultrasonic inspection, the compliance plan requires that the disks be inspected at an approved facility to ensure that the inspections meet the intent. As the inspection requires using a complex process and unique equipment, the AD requires that only approved facilities perform the inspection. This is not a change from the original proposed rule, but paragraph (a) of the compliance section has been edited to make this requirement more clear.
In addition, to simplify the AD, the definition of HPT disk piece part accessibility of paragraph (c) was deleted and incorporated into paragraph (a). Conclusion
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. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. Cost Impact
There are approximately 131 Pratt & Whitney JT9D-7R4 series turbofan engines of the affected design in the worldwide fleet. The FAA estimates that 25 engines installed on airplanes of U.S. registry will be affected by this AD. The FAA estimates that the shipping cost per disk to the facility which will inspect the disk and its return will be approximately $250 per disk, that no engines will require an unplanned HPT module disassembly/assembly, that the inspection would take approximately 8 work hours per disk to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Some disks will require multiple inspections during their service life. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $88,000. The manufacturer has advised the FAA that the all costs relative to the inspection may be reimbursed to the operator. Regulatory Impact
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 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: