2000-25-06: Low Pressure Turbine (LPT) 4th Stage Air Seal

2000-25-06 Pratt & Whitney: Amendment 39-12040. Docket 2000-NE-43-AD. Applicability: This airworthiness directive is applicable to Pratt & Whitney (PW) PW4052, PW4056, PW4060, PW4060A, PW4062, PW4152, PW4156, PW4156A, PW4158, PW4164, PW4168, PW4168A, PW4460, and PW4462 turbofan engines, with low pressure turbine (LPT) 4th stage air seal, part number (P/N) 50N478 or P/N 50N478-001 installed. These engines are installed on but not limited to Boeing 747, 767, McDonnell Douglas MD-11, Airbus Industrie A300, A310, and A330 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: Compliance with this AD is required as indicated, unless already done. To reduce stresses that could lead to fatigue cracking of the LPT 4th stage air seal, resulting in seal fracture, uncontained engine failure, and damage to the airplane, do the following: (a) If the limits in Table 1 of this AD for 4th stage air seal P/N 50N478 or P/N 50N478-001 have been exceeded, replace with a serviceable part prior to further flight. (b) Replace 4th stage air seal, P/N 50N478 or 50N478-001, with a serviceable part, based on engine model, prior to exceeding the cycles-since-new (CSN) or cycles-in-service (CIS) time limits in Table 1 of this AD. Table1. 4th Stage Air Seal Time Limits. Engine Model 4th Stage Air Seal P/N Cycles-since-new (CSN) on Effective Date of This AD Limit (1) PW4052, PW4060, PW4060A, PW4156, and PW4158. 50N478. Fewer than or equal to 8,000 CSN. 8,000 CSN (2) PW4056, PW4152, PW4156A, and PW4460, that have incorporated service bulletin (SB) PW4ENG 72-657, Revision 1, dated July 19, 2000. 50N478. Fewer than or equal to 8,000 CSN. 8,000 CSN (3) PW4056, PW4152, PW4156A, and PW4460, that have not incorporated SB PW4ENG 72-657, Revision 1, dated July 19, 2000. 50N478. Fewer than or equal to 4,500 CSN. 4,500 CSN (4) PW4062 and PW4462. 50N478. Fewer than or equal to 7,000 CSN. 7,000 CSN (5) PW4164, PW4168, and PW4168A. (i) 50N478 or 50N478-001 Fewer than or equal to 3,000 CSN. 4,500 CSN (ii) 50N478 or 50N478-001 More than 3,000 CSN but fewer than or equal to 4,500 CSN 1,500 CIS after the effective date of this AD (iii) 50N478 or 50N478-001 More than 4,500 CSN but fewer than 6,000 CSN 6,000 CSN (c) For the purposes of this AD, a serviceable part is defined in Table 2 as follows: Table 2. Serviceable Parts. For Engine Models Serviceable P/N (1) PW4052, PW4056, PW4060, PW4060A, PW4062, PW4152, PW4156, PW4156A, PW4158, PW4460, and PW4462. 51N038 or 50N478-001. (2) PW4164, PW4168, and PW4168A. 51N038. Alternative Methods 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 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 inspection and rework requirements of this AD can be accomplished. Effective Date of This AD (f) This amendment becomes effective December 29, 2000.