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98-12-07
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Compressor Disks Category
- Engine Applicability: Pratt & Whitney (PW) JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -15A, -17, -17A, -17R, and -17AR turbofan engines installed on but not limited to Boeing 737 and 727 series, and McDonnell Douglas DC-9 series aircraft. 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 (j) 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 fracture of the high pressure compressor (HPC) disks, which can result in uncontained release of engine fragments, inflight engine shutdown, and airframe damage, accomplish the following: (a) Within four months of the effective date of this AD, determine the fleet and sub-fleet average engine utilization rate for the 12 months of operations prior to August 17, 1994, the issue date of PW Alert Service Bulletin (ASB) No. 6038, Revision 5, in accordance with paragraph 2.A of PW ASB No. 6038, Revision 5, dated August 17, 1994. (1) For fleet or sub-fleet average utilization rates that are equal to or greater than 1,300 hours per year, and equal to or greater than 900 cycles per year, perform the following: (i) For engines or stage 7 through stage 12 HPC disks that were added to a fleet or subfleet after November 28,1994, and that were previously designated as low utilization disks in accordance with PW ASB No. 6038, Revision 5, dated August 17, 1994, comply with the requirements of paragraph (d) of this AD. (ii) Designate all other stage 7 through stage 12 HPC disks as high utilization disks and comply with the requirements of paragraph (b) of this AD. (2) For fleet or sub-fleet average utilization rates that are less than 1,300 hours per year or less than 900 cycles per year, within four months after the effective date of this AD, determine the utilization rate for each stage 7 through stage 12 HPC disk in accordance with paragraph 2.B.(1) of PW ASB No. 6038, Revision 5, dated August 17, 1994. (i) For each stage 7 through stage 12 HPC disk with an initial utilization rate equal to or greater than 1,300 hours per year, and equal to or greater than 900 cycles per year, designate this disk as a high utilization disk and inspect in accordance with paragraph (c) of this AD. (ii) For each stage 7 through stage 12 HPC disk with an initial utilization rate less than 1,300 hours per year or less than 900 cycles per year, designate this disk as a low utilization disk and inspect in accordance with paragraph (d) of this AD. (iii) For each stage 7 through stage 12 HPC disk with an unknown initial utilization rate, designate this disk as a low utilization disk and inspect in accordance with paragraph (d) of this AD. Note 2: Once a disk is designated as low utilization, then it must retain this designation for the life of the disk or until recoated. (iv) For recoated or new disks, designate these disks as high utilization disks and inspect in accordance with paragraph (c) of this AD. (b) For high average utilization fleets and sub-fleets, excluding those disks identified in paragraph (a)(1)(i) of this AD, perform the following for each stage 7 through stage 12 HPC disk in that fleet or sub-fleet: (1) Inspect, and recoat or replace if necessary, at the next part accessibility of the disk, in accordance with paragraph 2.D.(1)(b) and Chart A of PW ASB No. 6038, Revision 5, dated August 17, 1994. (2) Recalculate the fleet or sub-fleet average utilization rate at 12 month intervals after the previous date of utilization determination in accordance with paragraph 2.B of PW ASB No. 6038, Revision 5, dated August 17, 1994. (i) For fleet or sub-fleet average utilization rates that are equal to or greater than 1,300 hours per year, and equal to or greater than 900 cycles per year, continue to designate all stage 7 through stage 12 HPC disks as high utilization disks and comply with the requirements of paragraph (b) of this AD. (ii) For fleet or sub-fleet average utilization rates that are less than 1,300 hours per year or less than 900 cycles per year, within four months of compliance with paragraph (b)(2) of this AD, determine the utilization rate for each stage 7 through stage 12 HPC disk in accordance with paragraph 2.B.(1) of PW ASB No. 6038, Revision 5, dated August 17, 1994, as follows: (A) For each stage 7 through stage 12 HPC disk with a utilization rate equal to or greater than 1,300 hours per year, and equal to or greater than 900 cycles per year, designate this disk as a high utilization disk and inspect in accordance with paragraph (c) of this AD. (B) For each stage 7 through stage 12 HPC disk with a utilization rate less than 1,300 hours per year or less than 900 cycles per year, designate this disk as a low utilization disk and inspect in accordance with paragraph (d) of this AD. (C) For each stage 7 through stage 12 HPC disk with an unknown utilization rate, designate this disk as a low utilization disk and inspect in accordance with paragraph (d) of this AD. Note 3: Once a disk is designated as low utilization, then it must retain this designation for the life of the disk or until recoated. (c) For high utilization stage 7 through stage 12 HPC disks, perform the following: (1) Inspect, and recoat or replace if necessary, at the next part accessibility of the disk, in accordance with paragraph 2.D.(1)(b) and Chart A of PW ASB No. 6038, Revision 5, dated August 17, 1994. (2) Calculate the disk utilization rate at 12 month intervals after the previous date of utilization determination, or after installation of new or recoated disks, in accordance with paragraph 2.B.(3) of PW ASB No. 6038, Revision 5, dated August 17, 1994. (i) For stage 7 through stage 12 HPC disks designated as high utilization in accordance with (c)(2), comply with the requirements of paragraph (c)(1) of this AD. (ii) For stage 7 through stage 12 HPC disks designated as low utilization in accordance with (c)(2), comply with the requirements of paragraph (d) of this AD. (d) For low utilization stage 7 through stage 12 HPC disks, perform the following: (1) For Nickel Cadmium coated disks listed by Part Number (P/N) in Chart B of PW ASB No. 6038, Revision 5, dated August 17, 1994, and Aluminide coated disks listed by P/N in Chart C of PW ASB 6038, Revision 5, dated August 17, 1994, strip protective coating, corrosion inspect, and recoat or remove from service in accordance with PW JT8D Engine Manual, P/N 481672, at the time intervals specified in Table A or Table B of this AD, whichever occurs later. Table A.--Years Since New, Recoated, or Corrosion Inspection (YRSNRC) Interval for Low Utilization Disks--NiCadCoated Disks From Chart B of PW ASB No. 6038, Revision 5, Dated August 17, 1994, and Aluminide Coated Disks From Chart C of PW ASB No. 6038, Revision 5, Dated August 17, 1994 -------------------------------------------------------------------------- Years since new, recoated or corrosion inspected (YRSNRC) Remove to inspect and recoat or replace -------------------------------------------------------------------------- Less than or equal to 5........................... By 7 YRSNRC. Greater than 5 but less than or equal to 6........ Within 24 months. Greater than 6 but less than or equal to 7........ Within 18 months. Greater than 7 but less than or equal to 8........ Within 15 months. Greater than 8 but less than or equal to 9........ Within 12 months. Greater than 9 but less than or equal to 10....... Before reaching 10 YRSNRC. Greater than 10................................... Before further flight. -------------------------------------------------------------------------- Table B.--Years Since Last Non-Corrosion Inspection (YRSLI) Interval for Low Utilization Disks--NiCad Coated Disks From Chart B of PW ASB No. 6038, Revision 5, Dated August 17, 1994, and Aluminide Coated Disks From Chart C of PW ASB No. 6038, Revision 5, Dated August 17, 1994 -------------------------------------------------------------------------- Years since last non-corrosion inspection prior to November 28, 1994 (YRSLI) Remove to inspect and recoat or replace -------------------------------------------------------------------------- Less than or equal to 3........................... By 5 YRSLI. Greater than 3 but less than or equal to 5........ Within 24 months. Greater than 5 but less than or equal to 6........ Within 18 months. Greater than 6 but less than or equal to 7........ Within 12 months. Greater than 7 but less than or equal to 8........ Before reaching 8 YRSLI. Greater than 8.................................... Before further flight. -------------------------------------------------------------------------- (2) For Nickel Cadmium coated disks listed by P/N in Chart C of PW ASB No. 6038, Revision 5, dated August 17, 1994, strip protective coating, corrosion inspect, and recoat or remove from service in accordance with PW JT8D Engine Manual, P/N 481672, at the time intervals specified in Table C or Table D of this AD, whichever occurs later. Table C.--YRSNRC Inspection Interval for Low Utilization Disks--NiCad Coated Disks From Chart C of PW ASB No. 6038, Revision 5, Dated August 17, 1994 -------------------------------------------------------------------------- Years since new, recoated or corrosion inspected (YRSNRC) Remove to inspect and recoat or replace -------------------------------------------------------------------------- Less than or equal to 5........................... By 7 YRSNRC. Greater than 5 but less than or equal to 6........ Within 24 months. Greater than 6 but less than or equal to 7........ Within 21 months. Greater than 7 but less than or equal to 8........ Within 18 months. Greater than 8 but less than or equal to 9........ Within 15 months. Greater than 9 but less than or equal to 10....... Within 12 months. Greater than 10 but less than or equal to 11...... Before reaching 11 YRSNRC. Greater than 11................................... Before further flight. -------------------------------------------------------------------------- Table D.--YRSLI Inspection Interval for Low Utilization Disks--NiCad Coated Disks From Chart C of PW ASB No. 6038, Revision 5, Dated August 17, 1994 -------------------------------------------------------------------------- Years since last non-corrosion inspection prior to November 28, 1994 (YRSLI) Remove to inspect and recoat or replace -------------------------------------------------------------------------- Less than or equal to 4........................... By 6 YRSLI. Greater than 4 but less than or equal to 6........ Within 24 months. Greater than 6 but less than or equal to 7........ Within 18 months. Greater than 7 but less than or equal to 8........ Within 12 months. Greater than 8 but less than or equal to 9........ Before reaching 9 YRSLI. Greater than 9.................................... Before further flight. -------------------------------------------------------------------------- (3) For Aluminide coated disks listed by P/N in Chart B of PW ASB No. 6038, Revision 5, dated August 17, 1994, strip protective coating, corrosion inspect, and recoat or remove from service in accordance with PW JT8D Engine Manual, P/N 481672, at the time intervals specified in Table E or Table F of this AD, whichever occurs later. Table E.--YRSNRC Inspection Interval for Low Utilization Disks Aluminide Coated Disks From Chart B of PW ASB No.6038, Revision 5, Dated August 17, 1994 -------------------------------------------------------------------------- Years since new, recoated or corrosion inspected (YRSNRC) Remove to inspect and recoat or replace -------------------------------------------------------------------------- Less than or equal to 5........................... By 7 YRSNRC. Greater than 5 but less than or equal to 6........ Within 24 months. Greater than 6 but less than or equal to 7........ Within 18 months. Greater than 7 but less than or equal to 8........ Within 12 months. Greater than 8 but less than or equal to 9........ Before reaching 9 YRSNRC. Greater than 9.................................... Before further flight. -------------------------------------------------------------------------- Table F.--YRSLI Inspection Interval for Low Utilization Disks Aluminide Coated Disks From Chart B of PW ASB No. 6038, Revision 5, Dated August 17, 1994 -------------------------------------------------------------------------- Years since last non-corrosion inspection prior to November 28, 1994 (YRSLI) Remove to inspect and recoat or replace -------------------------------------------------------------------------- Less than or equal to 2........................... By 4 YRSLI. Greater than 2 but less than or equal to 4........ Within 24 months. Greater than 4 but less than or equal to 5........ Within 18 months. Greater than 5 but less than or equal to 6........ Within 12 months. Greater than 6 but less than or equal to 7........ Before reaching 7 YRSLI. Greater than 7.................................... Before further flight. -------------------------------------------------------------------------- (4) For all other low utilization stage 7 through stage 12 HPC disks, strip protective coating, corrosion inspect, and recoat or remove from service in accordance with the PW JT8D Engine Manual, P/N 481672, prior to 7 years since new, recoated, or corrosion inspected (YRSNRC). (5) For disks that are categorized as high utilization and subsequently entered low utilization service, YRSNRC can be adjusted as follows and applied to Table A, Table C, and Table E of this AD: (i) Adjusted YRSNRC = (0.60) x (years utilized at a rate greater than or equal to 1,300 hours per year, and greater than or equal to 900 cycles per year) + (years classified as low utilization). (ii) Once a disk enters low utilization service it must remain in that category and an adjustment to YRSNRC cannot be made for any subsequent high utilization operation. (iii) Years Since Last Non-Corrosion Inspection prior to November 18, 1994 (YRSLI) is a one-time interval only and cannot be used as a repetitive interval. (e) For stage 7 through stage 12 HPC disks that have been recoated in accordance with paragraphs (b)(1), (c)(1), or (d)(1) of this AD, designate these disks as high utilization and perform the following: (1) For disks installed in an engine that is part of a high utilization fleet, comply with the requirements of paragraph (b) of this AD. (2) For disks installed in an engine that is part of a low utilization fleet, comply with the requirements of paragraph (c) of this AD. (f) For the purpose of this AD, recoat of an HPC disk is defined as removal and application of new plating or coating in accordance with Sections 72-36-41, Repair 02; 72-36-42, Repair 02; 72-36-43, Repair 03; 72-36-44, Repair 03; 72-36-45, Repair 03; or 72-36-46, Repair 03, as applicable, of PW JT8D Engine Manual P/N 481672. (g) For the purpose of this AD, a corrosion inspection is defined as performing an inspection in accordance with PW Engine Manual 481672, section 72-36-41, inspection 01 for stage 7 disks, section 72-36-42, inspection 02, for 8th stage disks, section 72-36-43, inspection 02 for 9th stage disks, section 72-36-44, inspection 02 for 10th stage disks, section 72-36-45, inspection 02 for 11th stage disks, section 72-36-46, inspection 02 for 12th stage disks. (h) For the purpose of this AD, part accessibility is defined as the removal of the disk from the engine and deblading of that disk. (i) For the purpose of this AD, a sub-fleet is defined as any individual aircraft or any portion of an operator's fleet that operates in a separate and unique route structure, characterized by different flight lengths, frequencies, or geographic location. (j) 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. Alternate methods of compliance approved for AD 94-20-01 are approved for this AD; adjustments to compliance times approved for AD 94-20-01 are not approved for this AD. Note 4: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office. (k) 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. (l) The actions required by this AD shall be done in accordance with the following PW ASB: Document No. Pages Revision Date -------------------------------------------------------------------------- PW
ASB No. 6038.............1 5................... August 17, 1994. ---------------------------------------------------------------------- (m) This amendment becomes effective on August 10, 1998. FOR FURTHER INFORMATION CONTACT: Christopher Spinney, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (781) 238-7175, fax (781) 238-7199.
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