AD 88-24-02

88-24-02 PRATT & WHITNEY CANADA (PWC): Priority letter AD issued November 16, 1988. Applies to PT6A-50 turboprop engines installed on Dehavilland of Canada DHC-7 aircraft. This priority letter AD is effective immediately upon receipt. Compliance is required as indicated, unless already accomplished. To prevent uncontained PT blade failure resulting from a PT blade shed overspeed event due to a RG assembly failure, accomplish the following: (a) Within one calendar day after receipt of this priority letter AD, inspect the airframe chip detector flag system and reinspect each day of operation, in accordance with Dehavilland Canada Dash 7 Maintenance Manual, Section 71-05-00. 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 in service after receipt of this priority letter AD, accomplish the following, unless already accomplished: (1) Remove and visually inspectthe engine chip detector for metal debris, in accordance with PWC PT6A-50 Maintenance Manual, Section 79-35-02, and based on the inspection results, accomplish the applicable procedures specified in Section 79-35-02. (2) Remove from service chip detector Part Number (P/N) 3020019, if installed, and replace with chip detector P/N 3026609. (3) Inspect the circuit wiring of the installed or replacement chip detector, P/N 3026609 in accordance with PWC PT6A-50 Maintenance Manual, Section 79-35-02. Remove from service, prior to further flight, chip detectors found with an open circuit and replace with serviceable parts. (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 chip detector flag 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. (c) Reinspect the main oil filter, thereafter, at intervals not to exceed 100 hours in service since last inspection in accordance with the requirements of paragraph (b) (5) above. If visible metallic debris is evident, accomplish paragraph (b) (1) above prior to further flight. (d) Remove, inspect, and reinstall the chip detector of non-installed engines, in accordance with paragraphs (b) (1), (b) (2), and (b) (3) above, prior to entering service. (e) Aircraft may be ferried in accordance with the provisions of Federal Aviation Regulations 21.197 and 21.199 to a base where the priority letter AD can be accomplished. (f) Upon request, an equivalent means of compliance with the requirements of this priority letter 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. (g) Upon submission of substantiating data by an owner or operator through an FAA Airworthiness Inspector, the Manager, Engine Certification Office, Engine and Propeller Directorate, Aircraft Certification Service, may adjust the compliance times specified in this priority letter AD. The applicable engine manufacturer's alert SIL No. 4019 and Maintenance Manual, Sections 79-35-02 and 79-25-04, may be obtained from Pratt & Whitney Canada, 1000 Marie-Victorin, Longueuil, Quebec, Canada J4G 1A1. The applicable aircraft Maintenance Manual, Section 71-05-00, may be obtained from Boeing Canada, DeHavilland Division, Garrett Boulevard, Downsview, Ontario, Canada M3K 145. The documents referenced inthis priority letter AD also may be examined at the Office of the Assistant Chief Counsel, Federal Aviation Administration, New England Region, 12 New England Executive Park, Burlington, Massachusetts 01803, Room 311, Rules Docket No. 88-ANE-38, between the hours of 8:00 a.m. and 4:30 p.m. Monday through Friday except federal holidays. This priority letter AD 88-24-02 is effective immediately upon receipt.