99-20-04: High Pressure Turbine Disks

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.