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75-11-04: Reduction Gearbox Engine Distress

FAA order 75-11-04 is an airworthiness directive in force since May 20, 1975. The FAA's subject line: Reduction Gearbox Engine Distress. It names the Pratt & Whitney Canada PT6A-20, Pratt & Whitney Canada PT6A-20A, Pratt & Whitney Canada PT6A-27, Pratt & Whitney Canada PT6A-28, Pratt & Whitney Canada PT6A-34, Pratt & Whitney Canada PT6A-6, Pratt & Whitney Canada PT6A series, Pratt & Whitney Canada PT6B-37A engines: about 670 aircraft on the U.S. register today across them, though an order usually covers particular versions or serial numbers rather than every one. System: engine.

What it applies to as the FAA lists it

Kind of product
Engine
Makes
Pratt & Whitney Canada Corp.
Models
PT6A-20, PT6A-20A, PT6A-20B, PT6A-27, PT6A-28, PT6A-34, PT6A-6, PT6A-6A, PT6A-6B, PT6A-6/C20, PT6B-9
Engine series
Pratt & Whitney Canada PT6A-20 23 aircraft
Pratt & Whitney Canada PT6A-20A 2 aircraft
Pratt & Whitney Canada PT6A-27 31 aircraft
Pratt & Whitney Canada PT6A-28 13 aircraft
Pratt & Whitney Canada PT6A-34 232 aircraft
Pratt & Whitney Canada PT6A-6 1 aircraft
Pratt & Whitney Canada PT6A series 182 aircraft
Pratt & Whitney Canada PT6B-37A 186 aircraft

Dates and paperwork

In force since
May 20, 1975
Docket
Unknown
Status
Current
The FAA's document
Read the order on the FAA's site

The order itself the regulatory text, as published

Show the full text (2,252 characters)
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.

Source: FAA Dynamic Regulatory System, airworthiness directives. The FAA's document is the authority; the register counts are this site's, from the FAA register of October 5, 2026. Connections as data: /graph/directive/75-11-04.json · aircraft systems.