AD 93-23-06

93-23-06 PRATT & WHITNEY CANADA: Amendment 39-8740. Docket No. 91-ANE-49. Supersedes priority letter AD 88-24-02. Applicability: Pratt & Whitney Canada (PWC) PT6A-50 series turboprop engines installed on but not limited to DeHavilland DHC-7 turboprop aircraft. Compliance: Required as indicated, unless accomplished previously. To prevent aircraft damage from engine failure debris, accomplish the following: (a) Within one calendar day after the effective date of this AD, inspect the airframe chip detector flag system, and thereafter reinspect each day of operation, in accordance with DeHavilland Canada (DHC) Dash 7 Maintenance Manual, Section 71-05-00, dated July 15, 1977. If the chip detector flag is actuated, accomplish paragraphs (b)(1), (b)(2), and (b)(4) of this AD, prior to further flight. (b) Within the next 50 hours time in service (TIS) after the effective date of this AD, accomplish the following: (1) Remove and visually inspect the engine chip detector for metal debris, in accordance with PWC PT6A-50 Maintenance Manual, Section 79-35-02, dated January 15, 1991, and based on the inspection results, accomplish the applicable procedures specified in Section 79-35-02, dated January 15, 1991. (2) Remove from service engine chip detector Part Number (P/N) 3040019, if installed, and replace with engine chip detector P/N 3026609. (3) Inspect the circuit wiring of the installed or replacement engine chip detector, P/N 3026609, in accordance with PWC PT6A-50 Maintenance Manual, Section 79-35-02, dated January 15, 1991. Remove from service, prior to further flight, engine chip detectors found with an open circuit and replace with serviceable engine chip detectors. (4) Perform a one-time inspection check of the airframe chip detector flag system by grounding the wiring pins in the connector to the chip detector, in accordance with PWC Alert Service Information Letter (SIL) No. 4019, dated October 20, 1988. If the chip detectorflag is not actuated in the nacelle, correct defects and repeat this inspection check until the chip detector flag actuation is confirmed (reference DeHavilland Canada Dash 7 Maintenance Manual, Section 71-05-00, dated July 15, 1977). (5) Inspect the main oil filter for contamination, and based on the inspection results, accomplish the applicable procedures specified in PWC PT6A-50 Maintenance Manual, Section 79-25-04, dated January 15, 1991. (c) Thereafter, inspect the main oil filter at intervals not to exceed 100 hours TIS since the last inspection in accordance with the requirements of paragraph (b)(5) of this AD. If visible metallic debris is evident, accomplish paragraph (b)(1) of this AD prior to further flight. (d) Remove, inspect, and reinstall the engine chip detector of non-installed engines, in accordance with paragraphs (b)(1), (b)(2), and (b)(3) above, prior to entering service. NOTE: Paragraphs (a) through (d) of this AD repeat the compliance requirementsof paragraphs (a) through (d) of priority letter AD 88-24-02. (e) Remove from service power turbine (PT) shroud, Part Number (P/N) 3023797, and replace with PT shroud, P/N 3112919-01, in accordance with PWC Service Bulletin (SB) No. 4143R2, dated December 6, 1991, on or before December 31, 1994. PWC SB 4143, dated May 31, 1989, and PWC SB 4143, Revision 1, dated February 12, 1990, are acceptable alternate means of compliance to this AD. Installation of PT shroud, P/N 3112919-01, constitutes terminating action to the inspection requirements of this AD. (f) 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. The request should be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office. NOTE: Information concerning the existence of approved alternative methodsof compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office. (g) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the aircraft to a location where the requirements of this AD can be accomplished. (h) The modification shall be done in accordance with the following documents:

Document No. Page No. Issue Date DHC-7 Maintenance Manual, Section 71-05-00 1-3 Original Jul 15, 1977 Total pages: 3

PWC PT6A-50 1 Original Apr 5, 1976 Maintenance Manual, 2 Original Mar 1, 1977 Section 79-35-02 201 Original Jan 26, 1983

202 Original Apr 5, 1976

203 Original Jan 15, 1991

204 Original Jan 26, 1983 Total pages: 6

PWC Alert SIL No. 4019 1-2 Original Oct 20, 1988 Total pages: 2

PWC PT6A-50 202 A&B Original Jan 26, 1983 Maintenance Manual, 204, &

Section 79-25-04 209

203 Original Apr 5, 1976

205-6 Original Jan 15, 1991

207-8, Original Apr 2, 1987

& 210

Total pages: 10

PWC (SB) No. 4143R2 1-2 Revision 2 Dec 6, 1991 Total pages: 2

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 Canada, Technical Publications Department, 1000 Marie Victorin, Longueuil, Quebec J4G 1A1. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief 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. (i) This amendment becomes effective on January 26, 1994.