# AD 75-11-04: Reduction Gearbox Engine Distress - Type: Airworthiness directive - Status: Current - Products: Pratt & Whitney Canada PT6A-20, PT6A-20A, PT6A-20B, PT6A-27, PT6A-28, PT6A-34, PT6A-6, PT6A-6A, PT6A-6B, PT6A-6/C20 and PT6B-9 - Effective: May 20, 1975 - Superseded by: Nothing supersedes this AD - Product type: Engine - Amendment: 39-2207 - Registered aircraft: 2,830 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/608E39A67B51CB848625682C00570CC7.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/75-11-04 ## The airworthiness directive 75-11-04 UNITED AIRCRAFT: Amendment 39-2207. Applies to all United Aircraft of Canada Limited PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 series turbo-prop engines and PT6B-9 turboshaft engines, incorporating an unmodified power turbine shaft housing assembly part number 3010548. Compliance required as indicated. To aid the early detection, and thereby prevention of PT6A or PT6B engine distress especially in the reduction gearbox of engines incorporating power turbine shaft housing assembly part number 3010548 yet unmodified, accomplish the following: For the PT6A-20, -20A, -20B, -6/C20 engines affected, compliance required within the next fifty hours in service after effective date of this AD. For the PT6A-6, -6A, -6B, -27, -28, -34 and PT6B-9 engines affected, compliance required at the next engine overhaul shop visit, but no later than 3500 hours in service after effective date of this AD. 1. Unless previously accomplished, remove the reduction gearbox oil drain plug part number MS9015-08 and discard the preformed packing part number MS9388-115. Install magnetic chip detector part number 3014794 or 3019373 with a new preformed packing part number MS9388-115 and torque to 45 to 55 lb. in. and lockwire. Install cap part number MS25043-12D or connector part number MS3106-R-12S-3S with connected electrical wiring suitably supported and leading out to a more accessible area within the engine nacelle enclosure. 2. Within the next twenty-five hours in service after installation of the magnetic chip detector and every twenty-five hours in service thereafter, check magnetic chip detector for electrical continuity using any utility ohmmeter. If a resistance of 100 ohms or less is indicated, remove and clean the magnetic chip detector, and inspect the main engine oil filter in accordance with AD 75-06-01. 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. This amendment is effective May 20, 1975. ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS E4EA](https://openairdocs.org/tcds/E4EA): Pratt & Whitney Canada Corp.; names 7 of 54 models: PT6A-20B, PT6A-6B, PT6A-6/C20, PT6A-6, PT6B-9, PT6A-6A, PT6A-20 ## Registered aircraft it may apply to (OpenAirDocs) Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment. - Aircraft: 2,830 (0 by airframe model, 2,830 by engine model) - Makers: Beech 586, Cessna 449, Air Tractor 411, Raytheon 280, Piper 240, Pilatus 168, Quest 138, Dehavilland 118, Socata 110, Kodiak 69 Models with the most aircraft: - [Pratt & Whitney PT6A series](https://openairdocs.org/engine/pratt-whitney-pt6a-series): 2,217 aircraft (engine model) - [Pratt & Whitney Canada PT6A-34 series](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-34-series): 230 aircraft (engine model) - [Pratt & Whitney Canada PT6A-6 series](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-6-series): 170 aircraft (engine model) - [Pratt & Whitney PT6 series](https://openairdocs.org/engine/pratt-whitney-pt6-series): 43 aircraft (engine model) - [Pratt & Whitney PT6A-34 series](https://openairdocs.org/engine/pratt-whitney-pt6a-34-series): 42 aircraft (engine model) - [Pratt & Whitney Canada PT6A-27 series](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-27-series): 30 aircraft (engine model) - [Pratt & Whitney PT6A-27 series](https://openairdocs.org/engine/pratt-whitney-pt6a-27-series): 28 aircraft (engine model) - [Pratt & Whitney PT6A-28 series](https://openairdocs.org/engine/pratt-whitney-pt6a-28-series): 25 aircraft (engine model) - [Pratt & Whitney Canada PT6A-20](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-20): 21 aircraft (engine model) - [Pratt & Whitney Canada PT6A-28 series](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-28-series): 12 aircraft (engine model) - [Pratt & Whitney PT6A-20A series](https://openairdocs.org/engine/pratt-whitney-pt6a-20a-series): 4 aircraft (engine model) - [Pratt & Whitney Canada PT6 series](https://openairdocs.org/engine/pratt-whitney-canada-pt6-series): 3 aircraft (engine model) - [Pratt & Whitney Canada PT6A-20A series](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-20a-series): 2 aircraft (engine model) - [U/A Canada PT6A-20](https://openairdocs.org/engine/u-a-canada-pt6a-20): 2 aircraft (engine model) - [U/A Canada PT6A-6](https://openairdocs.org/engine/u-a-canada-pt6a-6): 1 aircraft (engine model) All 16 models: https://openairdocs.org/ad/75-11-04/models.md Every aircraft: https://openairdocs.org/ad/75-11-04/aircraft.md Its text cites no advisory circulars or STCs. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.