90-19-08 GENERAL ELECTRIC COMPANY: Amendment 39-6720. Docket No. 90-ANE-09-AD.
Applicability: General Electric Company (GE) CF6-6 turbofan engines installed on, but not limited to, McDonnell Douglas DC-10-10 aircraft.
Compliance: Required as indicated, unless already accomplished.
To prevent low cycle fatigue (LCF) failure of the low pressure turbine rotor (LPTR) stage one disk, LPTR stage two disk, and LPTR forward shaft, which could result in uncontained engine failure, accomplish the following:
(a) Remove from service, LPTR stage one disks, Part Numbers (P/N) 9690M76P02, 9690M76P03, 9690M76P08, and 9079M51P01, in accordance with the following schedule based upon disk cycles since new (CSN) on the effective date of this AD:
(1) Remove within 400 cycles in service (CIS) after the effective date of this AD, disks with greater than or equal to 19,600 CSN.
(2) Remove at the next LPTR overhaul after the effective date of this AD, but no later than 4,500 CIS afterthe effective date of this AD or prior to accumulating 20,000 CSN, whichever occurs first, disks with greater than or equal to 10,700 CSN, but less than 19,600 CSN.
(3) Remove within 4,500 CIS after the effective date of this AD, disks with greater than or equal to 6,200 CSN, but less than 10,700 CSN.
(4) Remove prior to exceeding 10,700 CSN, disks with less than 6,200 CSN.
(5) Thereafter, remove disks from service and replace with a serviceable disk prior to exceeding 10,700 CSN.
(b) Remove from service, LPTR forward shafts, P/N 9690M90P04, 9690M90P05, 9690M90P07, 9174M87P02 and 9174M87P04, in accordance with the following schedule based upon shaft CSN on the effective date of this AD:
(1) Remove within 400 CIS after the effective date of this AD, shafts with greater than or equal to 19,600 CSN.
(2) Remove at the next LPTR overhaul after the effective date of this AD, but no later than 4,500 CIS after the effective date of this AD or prior to accumulating 20,000CSN, whichever occurs first, shafts with greater than or equal to 15,000 CSN but less than 19,600 CSN.
(3) Remove within 4,500 CIS after the effective date of this AD, shafts with greater than or equal to 10,500 CSN, but less than 15,000 CSN.
(4) Remove prior to exceeding 15,000 CSN, shafts with less than 10,500 CSN.
(5) Thereafter, remove shafts from service and replace with a serviceable shaft prior to exceeding 15,000 CSN.
(c) Replace LPTR stage two disks, P/N 9690M77P03, 9690M77P04, 9690M77P09, 9690M77P11, 9249M40P01, 9249M40P02, 9249M40P03, 9249M40P04 and 9249M40P05, with LPTR stage two disk, P/N 9690M77P14, or later FAA-approved replacement stage two disk, at the next LPTR overhaul after the effective date of this AD, but no later than 4,500 CIS after the effective date of this AD or prior to exceeding the published LCF retirement life, whichever occurs first.
NOTES: (1) For the purpose of this AD, an LPTR overhaul is defined as the induction of the engine intoa shop where the subsequent maintenance entails LPTR disassembly.
(2) This action establishes the following new LCF retirement lives which are published in Chapter 5 of the CF6-6 Maintenance and Shop manuals:
(a) 10,700 cycles for LPTR stage one disks, P/N 9690M76P02, 9690M76P03, 9690M76P08 and 9079M51P01.
(b) 15,000 cycles for LPTR forward shafts, P/N 9690M90P04, 9690M90P05, 9690M90P07, 9174M87P02 and 9174M87P04.
(3) CF6-6 Series Service Bulletin (SB) 72-944 introduces a new LPTR stage one disk, P/N 9079M51P03, which has an FAA approved LCF retirement life of 20,000 CSN.
(4) CF6-6 Series SB 72-945 introduces an FAA approved rework procedure for the affected LPTR forward shafts to increase the FAA approved LCF retirement life to 20,000 CSN.
(d) Aircraft may be ferried in accordance with the provisions of FAR 21.197 and 21.199 to a base where the AD can be accomplished.
(e) Upon submission of substantiating data by an owner or operator through an FAA Airworthiness Inspector, an alternate method of compliance with the requirements of this AD or adjustments to the compliance (schedule) times specified in this AD may be approved by the Manager, Engine Certification Office, Engine and Propeller Directorate, Aircraft Certification Service, Federal Aviation Administration, 12 New England Executive Park, Burlington, Massachusetts 01803.
All persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to General Electric Aircraft Engines, CF6 Distribution Clerk, Room 132, 111 Merchant Street, Cincinnati, Ohio 45246. These documents may be examined at the Regional Rules Docket, Office of the Assistant Chief Counsel, New England Region, 12 New England Executive Park, Room 311, Burlington, Massachusetts 01803.
This amendment (39-6720, AD 90-19-08) becomes effective on October 15, 1990.