75-06-01: Gearbox Deterioration

75-06-01 UNITED AIRCRAFT OF CANADA LIMITED and PRATT & WHITNEY AIRCRAFT: Amendment 39-2118 as amended by Amendment 39-2182, 39-2208 and 39-2574 is further amended by Amendment 39-2858. Applies to all PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, and -34 series turboprop engines. Compliance required as indicated unless previously accomplished. To ensure the early detection of reduction gearbox deterioration which could result in an engine failure and provide for improved blade containment accomplish the following: (a) Within the next 50 hours in service after effective date of this AD, unless previously accomplished, remove the main engine oil filter element and visually inspect the element for magnetic and non-magnetic metal particles. (1) If the inspection reveals less than 40 non-magnetic metal and no magnetic metal particles, clean oil filter and reinspect after every 50 hours in service. (2) (i) If the inspection reveals more than 40 non-magnetic metal particles, clean oil filter and reinspect after 10 hours in service. (ii) If the reinspection, in accordance with paragraph (a)(2) (i) reveals less than 40 non-magnetic metal particles, clean oil filter and reinspect after every 50 hours in service thereafter. (iii) If the reinspection, in accordance with paragraph (a)(2) (i) reveals more than 40 non-magnetic metal particles, clean oil filter and reinspect after 10 hours in service. (iv) If the reinspection, in accordance with paragraph (a)(2) (iii) reveals more than 40 non-magnetic metal particles, the engine must be removed from service for an overhaul inspection. (v) If the reinspection in accordance with paragraph (a)(2) (iii) reveals less than 40 non-magnetic metal particles, clean oil filter and reinspect after every 50 hours in service thereafter. (3) (i) If the inspection reveals less than 40 magnetic metal particles clean oil filter and reinspect after 10 hours in service. (ii)If the reinspection in accordance with paragraph (a)(3) (i) reveals the presence of similar quantity of magnetic metal particles, the engine must be removed from service for an overhaul inspection. (iii) If the reinspection in accordance with paragraph (a)(3) (i) reveals the presence of lesser quantity of magnetic metal particles clean oil filter and reinspect every 50 hours time in service thereafter. (4) (i) If the inspection reveals more than 40 magnetic metal particles, clean oil filter, drain and change oil, perform a ground run for one hour and reinspect oil filter. If the inspection after one hour ground run reveals more than 40 magnetic metal particles, the engine must be removed from service for an overhaul inspection. (ii) If the inspection after one hour ground run reveals less than 40 magnetic metal particles, clean oil filter and reinspect after 10 hours in service. (iii) If the reinspection after 10 hours in service reveals a similar quantityof magnetic metal particles, the engine must be removed from service for an overhaul inspection. (iv) If the reinspection after 10 hours in service reveals a lesser quantity of magnetic metal particles, clean oil filter and reinspect every 50 hours in service thereafter. (b) For the PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28 and 34 engines, within the next 8000 hours in service after the effective date of the AD, alter part number 3010548, power turbine shaft housing assembly in accordance with paragraph 2, accomplishment instructions in United Aircraft of Canada Limited Engine Service Bulletin No. 1138 or approved equivalent, or replace said assembly with any other power turbine shaft housing assembly listed as eligible in the engine parts catalog. (c) For the PT6A-6, -6A, -6B, -6/C20, -20, -20A and -20B engines within the next 2000 hours in service after the effective date of this AD alter all the power turbine blades in accordance with paragraph 2, accomplishment instructions in Pratt & Whitney Aircraft of Canada Limited Engine Service Bulletin No. 1233, or approved equivalent alteration. (d) For the PT6A-27, -28 and -34 engines, within the next 4000 hours in service after the effective date of this AD install the improved power turbine containment ring in accordance with paragraph 2, accomplishment instructions in Pratt & Whitney Aircraft of Canada Limited Engine Service Bulletin No. 1220 or approved equivalent alterations and modified combustion chamber liner and related parts in accordance with paragraph 2, accomplishment instructions in Pratt & Whitney Aircraft of Canada Limited Engine Service Bulletin No. 1216, or approved equivalent alterations. (e) For the PT6A-20, -20A, and -20B, -6/C20 engines within the next 4000 hours in service after the effective date of this AD install the improved power turbine containment ring in accordance with paragraph 2, accomplishment instructions in Pratt & Whitney Aircraft of Canada Limited Engine Service Bulletin No. 1246 or approved equivalent alterations and modified combustion chamber liner and related parts in accordance with paragraph 2, accomplishment instructions in Pratt & Whitney Aircraft of Canada Limited Engine Service Bulletin No. 1245 or approved equivalent alterations. The main oil screen inspection requirements of this AD are no longer required when the engines have been modified as required by paragraph (b), (c), (d), and (e) as applicable. Aircraft may be flown to a base for performance of maintenance required by this AD per FAR 21.197 or FAR 21.199. Upon submission of substantiating data through an FAA Maintenance Inspector, the Chief, Engineering and Manufacturing Branch, FAA Eastern Region, may adjust the repetitive inspection times specified in this Airworthiness Directive. All equivalent alterations must be approved by the Chief, Engineering and Manufacturing Branch of the Eastern Region of the FAA. Amendment 39-2118 was effective March 10, 1975. Amendment 39-2182 was effective April 28, 1975. Amendment 39-2208 was effective May 20, 1975. Amendment 39-2574 was effective April 14, 1976. This amendment 39-2858 is effective April 1, 1977.