AD 75-11-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Pratt & Whitney Canada Corp. | PT6A-20 | UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines |
| engine | Pratt & Whitney Canada Corp. | PT6A-20A | UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines |
| engine | Pratt & Whitney Canada Corp. | PT6A-20B | UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines |
| engine | Pratt & Whitney Canada Corp. | PT6A-27 | UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines |
| engine | Pratt & Whitney Canada Corp. | PT6A-28 | UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines |
| engine | Pratt & Whitney Canada Corp. | PT6A-34 | UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines |
| engine | Pratt & Whitney Canada Corp. | PT6A-6 | UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines |
| engine | Pratt & Whitney Canada Corp. | PT6A-6A | UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines |
| engine | Pratt & Whitney Canada Corp. | PT6A-6B | UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines |
| engine | Pratt & Whitney Canada Corp. | PT6A-6/C20 | UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines |
| engine | Pratt & Whitney Canada Corp. | PT6B-9 | UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines |
Unsafe Condition
Failure of the reduction gearbox in engines incorporating power turbine shaft housing assembly part number 3010548, which could lead to engine distress.
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Required Actions
Install magnetic chip detector part number 3014794 or 3019373 with new preformed packing, torque to 45 to 55 lb. in., and lockwire. Install cap or connector with electrical wiring leading to an accessible area. Check magnetic chip detector every 25 hours in service for electrical continuity using an ohmmeter; if resistance ≤100 ohms, clean detector and inspect main engine oil filter per AD 75-06-01.
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Compliance Time
For PT6A-20, -20A, -20B, -6/C20 engines: within 50 hours in service after May 20, 1975. For PT6A-6, -6A, -6B, -27, -28, -34 and PT6B-9 engines: at next engine overhaul shop visit, but no later than 3500 hours in service after May 20, 1975.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Pratt & Whitney Canada Corp. PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 series engines and PT6B-9 engines with power turbine shaft housing assembly part number 3010548.
AI-generated summary from the source AD text. Verify against the official source before acting.
Federal Register Abstract
Reduction Gearbox Engine Distress
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_75-11-04.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 75-11-04 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and P...Show more Subject: Reduction Gearbox Engine Distress Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 05/20/1975 Make: Pratt & Whitney Canada Corp. Model: PT6A-20 | PT6A-20A | PT6A-20B | PT6A-27 | PT6A-28 | PT6A-34 | PT6A-6 | PT6A-6A | PT6A-6B | PT6A-6/C2...Show more Product Type: Engine Product Subtype: Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: Updated RGL applicability to match AD applicability; CAR C-11-185 AIRWORTHINESS DIRECTIVES FINAL RULES: 75-11-04 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-2207 AD NUMBER: 75-11-04 SUBJECT HEADING: UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines ACTION: SUMMARY: DATES: Effective May 20, 1975. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 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. FOOTER:
Document Text
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AD Final Rules - DRS_75-11-04.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 75-11-04 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and P...Show more Subject: Reduction Gearbox Engine Distress Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 05/20/1975 Make: Pratt & Whitney Canada Corp. Model: PT6A-20 | PT6A-20A | PT6A-20B | PT6A-27 | PT6A-28 | PT6A-34 | PT6A-6 | PT6A-6A | PT6A-6B | PT6A-6/C2...Show more Product Type: Engine Product Subtype: Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: Updated RGL applicability to match AD applicability; CAR C-11-185 AIRWORTHINESS DIRECTIVES FINAL RULES: 75-11-04 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-2207 AD NUMBER: 75-11-04 SUBJECT HEADING: UNITED AIRCRAFT Model PT6A-6, -6A, -6B, -6/C20, -20, -20A, -20B, -27, -28, -34 Series Engines and PT6B-9 Engines ACTION: SUMMARY: DATES: Effective May 20, 1975. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 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. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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