# Pratt & Whitney PT6A-20A series - Type: Engine model (FAA registry) - Registry code: 52139 - Manufacturer (registry): P & W - Model: PT6A-20A - Engine type: Turbo-prop - Power: 550 hp - Installed in: 4 registered aircraft - Page: https://openairdocs.org/engine/pratt-whitney-pt6a-20a-series The registry names only the engine series, so ADs for every model in the series are matched. ## ADs that may apply (OpenAirDocs) Matched to this engine model by model name and maker. Each AD's applicability may narrow it by serial number, part number or equipment. - [AD 2014-11-05](https://openairdocs.org/ad/2014-11-05): Reinforcement liner to the power turbine (PT) containment ring and, for certain PT containment rings, adding scallops · Pratt & Whitney Canada PT6A-11, PT6A-110, PT6A-112 and 18 more. Effective Aug 5, 2014 - [AD 2002-23-13](https://openairdocs.org/ad/2002-23-13): Turbine Exhaust Ducts · Pratt & Whitney Canada PT6A-11, PT6A-110, PT6A-112 and 20 more. Effective Dec 31, 2002 - [AD 97-04-12](https://openairdocs.org/ad/97-04-12): Compressor Bleed-off Valve · Pratt & Whitney Canada PT6A-11, PT6A-110, PT6A-112 and 52 more. Effective Mar 14, 1997 - [AD 92-15-11](https://openairdocs.org/ad/92-15-11): Compressor Delivery Air Line (P3) Filter Assembly · Pratt & Whitney Canada PT6A-20, PT6A-20A, PT6A-21 and 7 more. Effective Aug 17, 1992 - [AD 80-08-12](https://openairdocs.org/ad/80-08-12): Fuel Pump Drive Coupling Splines · Pratt & Whitney Canada PT6A-11, PT6A-112, PT6A-135 and 24 more. Effective Apr 18, 1980 - [AD 75-06-01](https://openairdocs.org/ad/75-06-01): Gearbox Deterioration · Pratt & Whitney Canada PT6A-20, PT6A-20A, PT6A-20B and 11 more. Effective Apr 1, 1977 - [AD 75-11-04](https://openairdocs.org/ad/75-11-04): Reduction Gearbox Engine Distress · Pratt & Whitney Canada PT6A-20, PT6A-20A, PT6A-20B and 8 more. Effective May 20, 1975 ## Information bulletins (advisory) (1) - [SAIB NE-12-04](https://openairdocs.org/saib/NE-12-04): Turbine/ Turboprop Engine: Reduction Gearbox. Issued Nov 1, 2011 ## Registered aircraft (4) - [N1013N](https://openairdocs.org/aircraft/N1013N): [Val Air 2 LLC](https://openairdocs.org/faa-owner/VAL%20AIR%202%20LLC), [White River, SD](https://openairdocs.org/faa-place/SD/White%20River), S/N 401-0722 - [N136PA](https://openairdocs.org/aircraft/N136PA): [X-Press Charter Service Inc](https://openairdocs.org/faa-owner/X-PRESS%20CHARTER%20SERVICE%20INC), [Longview, TX](https://openairdocs.org/faa-place/TX/Longview), built 1975, S/N LJ662 - [N628AA](https://openairdocs.org/aircraft/N628AA): [Edge Air LLC](https://openairdocs.org/faa-owner/EDGE%20AIR%20LLC), [Wilmington, DE](https://openairdocs.org/faa-place/DE/Wilmington), built 2022, S/N 4698222 - [N8004](https://openairdocs.org/aircraft/N8004): [Kingsburg, CA](https://openairdocs.org/faa-place/CA/Kingsburg), built 1983, S/N H-4, Registration pending ## NTSB investigations (3) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB CEN10CA262](https://openairdocs.org/ntsb/CEN10CA262), May 20, 2010: Air Tractor AT-301 (N3159D), D'Hanis, TX, substantial damage. Probable cause: The pilot's failure to properly set the airplane's flaps prior to takeoff. - [NTSB CHI04CA162](https://openairdocs.org/ntsb/CHI04CA162), Jun 23, 2004: Air Tractor AT-401 (N1013N), Britton, SD, substantial damage. Probable cause: The loss of engine power due to a stuck exhaust valve and the unsuitable terrain encountered during the forced landing. A factor to the accident was the soft terrain condition. - [NTSB MIA89LA127](https://openairdocs.org/ntsb/MIA89LA127), Apr 13, 1989: Air Tractor AT-301 (N3159D), Fort Pierce, FL, substantial damage. Probable cause: FAILURE OF THE NUMBER FIVE CYLINDER. FACTORS RELATED TO THE ACCIDENT WERE: THE PROXIMITY OF HOMES IN THE AREA, WHICH PRECLUDED JETTISONING OF THE CHEMICAL LOAD, AND HIGH VEGETATION IN THE EMERGENCY… ## FAA accident and incident reports (4) From the FAA Accident/Incident Data System. Reports are matched to registry aircraft by N-number and event date, checked against the reported make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [Accident 20100520035409A](https://openairdocs.org/incident/20100520035409A), May 20, 2010: Air Tractor AT-301 (N3159D), D'Hanis, TX, Substantial damage. Pilot attempted to takeoff without flaps and ran off the end of the runway. - [Incident 20070712825409I](https://openairdocs.org/incident/20070712825409I), Jul 12, 2007: Airtrc AT301 (N3159D), Penfield, IL, Minor damage. (-23) An ag-type aircraft had completed a pass and was maneuvering for another pass when the right wing suddenly dipped down in what the pilot considered wind… - [Accident 20040623012119A](https://openairdocs.org/incident/20040623012119A), Jun 23, 2004: Airtrc AT401 (N1013N), Britton, SD, Substantial damage. (-23) Pilot terry d. haven was spraying crops approximately seven miles NE of the Britton, SD airport (btn). He finished his last spray run and was heading… - [Accident 19890413007879A](https://openairdocs.org/incident/19890413007879A), Apr 13, 1989: Airtrc AT301 (N3159D), Fort Pierce, FL, Substantial damage. Engine lost power on takeoff. Unable to dump load crashed in trees between houses. Nr 5 cylinder assembly had cracked ## Service difficulty reports (7) As reported by operators and repair stations, by the model named in the report. - [SDR 5BMA20120418001](https://openairdocs.org/sdr/5BMA20120418001), Apr 6, 2012: TURBINE BLADES. FAILED. THE PILOT REPORTED THE FOLLOWING, DURING CLIMB AFTER TAKEOFF FROM KOMA AT APPROXIMATELY 11,000 MSL THE RIGHT ENGINE ABRUPTLY LOST POWER. TORQUE WENT TO ZERO, IT - [SDR 2009F00047](https://openairdocs.org/sdr/2009F00047), Jun 23, 2009: ENGINE. OVERTEMP. RT ENGINE HAD LOSS OF POWER AT CRUISE. ITT SPIKED AND STABILIZED AT 1100 C. ENGINE SHUTDOWN AND PROPELLER FEATHERED NORMALLY. NORMAL LANDING. - [SDR FSEA 09 0002](https://openairdocs.org/sdr/FSEA%2009%200002), Apr 28, 2009: TURBINE. DAMAGED. APPROX 45 MINUTES INTO FLIGHT AT FLT LEVEL 170 WHILE IN CRUISE FLIGHT CONDITIONS. RT ENGINE MADE AN UNUSUAL NOISE, FLAMES WERE SEEN FROM THE EXHAUST DUCTS. CREW - [SDR 2009FA0000278](https://openairdocs.org/sdr/2009FA0000278), Apr 2, 2009: ENGINE. FIRE. APPROX 30 MINUTES INTO FLIGHT, WHILE CRUISING AT 17,000 MSL, RT ENGINE MADE UNUSUAL NOISE, FLAMES WERE SEEN FROM EXHAUST DUCTS, ENGINE WAS SHUTDOWN. CREW DECLAR - [SDR JDWA118SF1](https://openairdocs.org/sdr/JDWA118SF1), Jan 26, 2009: PROPELLER. POWER LOSS. ON CLIMB OUT, LEFT PROPELLER RPM DROPPED FROM 2200 TO 1900 RPM. PILOT TOOK NOTE AND CALLED IN FOR RETURN. MAINTENANCE HAS NOT DETERMINED THE CAUSE AT THIS POINT - [SDR CA990301001](https://openairdocs.org/sdr/CA990301001), Feb 8, 1999: WHEEL. CRACKED. (CAN) WHEEL FOUND CRACKED. CRACK 20 CM LONG HAD OPENED ABOUT 6 MM. THE CRACK HAD PASSED THROUGH TWO FINS AND WAS PROGRESSING TOWARDS THE OUTSIDE OF THE RIM. TIR - [SDR CA970430003](https://openairdocs.org/sdr/CA970430003), Apr 10, 1997: WHEEL HALF. CRACKED. (CAN) HALF OF THE WHEEL ASSY OF THE LEFT HAND MAIN LANDING GEAR WHEEL BROKE DURING TAKEOFF. A TUBE IN THE TUBELESS TIRE PREVENTED AIR FROM ESCAPING THROUGH THE ## STCs that may be installed (OpenAirDocs) (9) Approved for this engine model: the STC's model list names it on its data sheet, or a series that includes it. In force first, then newest. The registry doesn't record which STCs an aircraft has. - [STC SE00003EN](https://openairdocs.org/stc/SE00003EN): Instructions for Continued Airworthiness for the PT6A-6/C20, -20, -20A and, -20B engine models that define specific maintenance tasks and their associated maintenance schedules, and that are used as a supplement to the applicable Pratt & Whitney Canada manuals. MORE Company Inc - [STC SE00014EN](https://openairdocs.org/stc/SE00014EN): Installation of the Pratt & Whitney Engine Services, Inc. CrossCheck Engine Monitor Kit P/N HUMS-K-071-1, Rev. A on the specified PT6A engine models and kit P/N HUMS-K-071-2 on the specified A250 engine models. Pratt & Whitney Engine Services Inc - [STC SE00020EN](https://openairdocs.org/stc/SE00020EN): Installation of the Pratt & Whitney Engine Services, Inc. TrendCheck/ TrendCheck Plus Engine Monitor Kit P/N TREND-K-010-1. Pratt & Whitney Engine Services Inc - [STC SE615GL](https://openairdocs.org/stc/SE615GL): Incorporation of a fuel flow transducer. Shadin Avionics - [STC SE09257SC](https://openairdocs.org/stc/SE09257SC): Convert P&W Engine Models PT6A-15AG, -27, and -28, into PT6A-34 configuration. Covington Aircraft Engines, Inc - [STC SE659NE](https://openairdocs.org/stc/SE659NE): Installation of oil tank filler neck check valve, P/N TSA-76A. Aviation Components Support - [STC SE1269EA](https://openairdocs.org/stc/SE1269EA): Stripping and recoating of compressor turbine blades, P/N 3023401, with Walbar Metals, Inc. Airwork Corporation - [STC SE1165EA](https://openairdocs.org/stc/SE1165EA): Assembly and installation of AW10262 wet spline starter gear seal. Airwork Corporation - [STC SE4607SW](https://openairdocs.org/stc/SE4607SW): Revise the starter-generator drive spline to provide lubrication with engine oil. Aviall of Texas, Inc ## PMA parts (OpenAirDocs) (586, first 50) Current parts manufacturer approvals (PMA): parts the FAA has approved companies to make as replacements or modifications. Each record lists its models as free text; OpenAirDocs matched them to this engine model on its data sheet, so check the FAA record before relying on it. Newest first. - [3005293CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID122934446820260909150736.0001): Insert, Fuel Control Drive Shaft. Core Parts LLC · PMA PQ05326NM · Replaces 3005293 · Aug 17, 2026 - [3005293CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID122934446820260909150736.0001): Insert, Fuel Control Drive Shaft. Core Parts LLC · PMA PQ05326NM · Replaces 3005293 · Aug 17, 2026 - [3019136CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID186981497620260728184309.0001): Ring, Plastic. Core Parts LLC · PMA PQ05326NM · Replaces 3019136 · Jul 10, 2026 - [3019136CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID186981497620260728184309.0001): Ring, Plastic. Core Parts LLC · PMA PQ05326NM · Replaces 3019136 · Jul 10, 2026 - [3012928CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID185594574320260728184309.0001): Spacer, Stepped. Core Parts LLC · PMA PQ05326NM · Replaces 3012928 · Jul 10, 2026 - [3012928CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID185594574320260728184309.0001): Spacer, Stepped. Core Parts LLC · PMA PQ05326NM · Replaces 3012928 · Jul 10, 2026 - [3045951-02AA](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID135029382220260722151307.0001): Detector, Chip, Magnetic. Aero Attitude, LLC · PMA PQ00001CB · Replaces 3045951-02 · May 27, 2026 - [3045951-02AA](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID135029382220260722151307.0001): Detector, Chip, Magnetic. Aero Attitude, LLC · PMA PQ00001CB · Replaces 3045951-02 · May 27, 2026 - [ST3277-01CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID199989902020260311145336.0001): Gasket, Starter Generator. Core Parts LLC · PMA PQ05326NM · Replaces ST3277-01 · Feb 26, 2026 - [ST3277-01CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID199989902020260311145336.0001): Gasket, Starter Generator. Core Parts LLC · PMA PQ05326NM · Replaces ST3277-01 · Feb 26, 2026 - [ST3276-01CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID101621452020260311145336.0001): Gasket, Four-Hole. Core Parts LLC · PMA PQ05326NM · Replaces ST3276-01 · Feb 26, 2026 - [ST3276-01CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID101621452020260311145336.0001): Gasket, Four-Hole. Core Parts LLC · PMA PQ05326NM · Replaces ST3276-01 · Feb 26, 2026 - [3007355CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID150958507420260217165221.0001): Spacer, Adjusting. Core Parts LLC · PMA PQ05326NM · Replaces 3007355 · Feb 11, 2026 - [3007355CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID150958507420260217165221.0001): Spacer, Adjusting. Core Parts LLC · PMA PQ05326NM · Replaces 3007355 · Feb 11, 2026 - [3010880CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID111084696520260108163216.0001): Gasket, Igniter. CORE PARTS LLC · PMA PQ05326NM · Replaces 3010880 · Oct 16, 2025 - [3010880CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID111084696520260108163216.0001): Gasket, Igniter. CORE PARTS LLC · PMA PQ05326NM · Replaces 3010880 · Oct 16, 2025 - [3034292WFC](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID166533215020250624152909.0001): Disposable Oil Filter Element. Donaldson Company Inc · PMA PQ2432CE · Replaces 3034292, 3034293, 3958257-01, 3028419… · Jun 2, 2025 - [3034292WFC](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID166533215020250624152909.0001): Disposable Oil Filter Element. Donaldson Company Inc · PMA PQ2432CE · Replaces 3034292, 3034293, 3958257-01, 3028419… · Jun 2, 2025 - [3034507WFC](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID141045710620250624152910.0001): Cleanable Oil Filter Element. Donaldson Company Inc · PMA PQ2432CE · Replaces 3017383, 3020967, 3022069, 3022070… · Jun 2, 2025 - [3034507WFC](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID141045710620250624152910.0001): Cleanable Oil Filter Element. Donaldson Company Inc · PMA PQ2432CE · Replaces 3017383, 3020967, 3022069, 3022070… · Jun 2, 2025 - [3034393WFC](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID100181403420250624152909.0001): Disposable Oil Filter Element. Donaldson Company Inc · PMA PQ2432CE · Replaces 3034393, 3033315, 3059257-01, 3028419… · Jun 2, 2025 - [3034393WFC](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID100181403420250624152909.0001): Disposable Oil Filter Element. Donaldson Company Inc · PMA PQ2432CE · Replaces 3034393, 3033315, 3059257-01, 3028419… · Jun 2, 2025 - [WF334552](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID147857861520250602133017.0001): Compressor Air Filter. Donaldson Company Inc · PMA PQ2432CE · Replaces 3029268, Alternate: 3028856, 3029267… · May 23, 2025 - [WF334552](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID147857861520250602133017.0001): Compressor Air Filter. Donaldson Company Inc · PMA PQ2432CE · Replaces 3029268, Alternate: 3028856, 3029267… · May 23, 2025 - [3115091-01CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID180857219920250923184724.0001): Ball, Plastic, 0.750. CORE PARTS LLC · PMA PQ05326NM · Replaces 3115091-01 · Feb 13, 2025 - [3115091-01CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID180857219920250923184724.0001): Ball, Plastic, 0.750. CORE PARTS LLC · PMA PQ05326NM · Replaces 3115091-01 · Feb 13, 2025 - [3058971-01CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID110906306720250923184724.0001): Valve Assy, Oil Filler Tube. CORE PARTS LLC · PMA PQ05326NM · Replaces 3058971-01 · Feb 13, 2025 - [3058971-01CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID110906306720250923184724.0001): Valve Assy, Oil Filler Tube. CORE PARTS LLC · PMA PQ05326NM · Replaces 3058971-01 · Feb 13, 2025 - [3049871-01CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID134847727520260108162918.0001): Washer, Key. CORE PARTS LLC · PMA PQ05326NM · Replaces 3049871-01 · Jan 17, 2025 - [3049871-01CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID134847727520260108162918.0001): Washer, Key. CORE PARTS LLC · PMA PQ05326NM · Replaces 3049871-01 · Jan 17, 2025 - [3012414AA](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID169774044220250106202801.0001): Nut, Self-Locking, 12 Point. Aero Attitude, LLC · PMA PQ00001CB · Replaces 3012411 · Dec 10, 2024 - [3012414AA](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID169774044220250106202801.0001): Nut, Self-Locking, 12 Point. Aero Attitude, LLC · PMA PQ00001CB · Replaces 3012411 · Dec 10, 2024 - [3012414AA](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID164469161820250106202800.0001): Nut, Self-Locking, 12 Point. Aero Attitude, LLC · PMA PQ00001CB · Replaces 3012413 · Dec 10, 2024 - [3012414AA](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID164469161820250106202800.0001): Nut, Self-Locking, 12 Point. Aero Attitude, LLC · PMA PQ00001CB · Replaces 3012413 · Dec 10, 2024 - [3012414AA](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID152753542620250106202759.0001): Nut, Self-Locking, 12 Point. Aero Attitude, LLC · PMA PQ00001CB · Replaces 3012414 · Dec 10, 2024 - [3012414AA](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID152753542620250106202759.0001): Nut, Self-Locking, 12 Point. Aero Attitude, LLC · PMA PQ00001CB · Replaces 3012414 · Dec 10, 2024 - [3012414AA](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID117377138920250106202801.0001): Nut, Self-Locking, 12 Point. Aero Attitude, LLC · PMA PQ00001CB · Replaces 3012412 · Dec 10, 2024 - [3012414AA](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID117377138920250106202801.0001): Nut, Self-Locking, 12 Point. Aero Attitude, LLC · PMA PQ00001CB · Replaces 3012412 · Dec 10, 2024 - [218794ACD](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID136891010120241022133827.0001): Washer, CRES. Aircraft Component Design LLC · PMA PQ2138NE · Replaces 218794 · Oct 3, 2024 - [218794ACD](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID136891010120241022133827.0001): Washer, CRES. Aircraft Component Design LLC · PMA PQ2138NE · Replaces 218794 · Oct 3, 2024 - [3010671CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID189963175420241202221129.0001): Washer, Flat. CORE PARTS LLC · PMA PQ05326NM · Replaces 3010671 · Aug 22, 2024 - [3010671CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID189963175420241202221129.0001): Washer, Flat. CORE PARTS LLC · PMA PQ05326NM · Replaces 3010671 · Aug 22, 2024 - [3012675AA](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID196954661720240919140845.0001): Nut, Self-Locking, Hex. Aero Attitude, LLC · PMA PQ00001CB · Replaces 3012675, 3005816, 3012674, 3028286… · Aug 7, 2024 - [3012675AA](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID196954661720240919140845.0001): Nut, Self-Locking, Hex. Aero Attitude, LLC · PMA PQ00001CB · Replaces 3012675, 3005816, 3012674, 3028286… · Aug 7, 2024 - [3006523CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID132375139220240509162259.0001): Bearing, Sleeve, Flanged. CORE PARTS LLC · PMA PQ05326NM · Replaces 3006523 · Mar 25, 2024 - [3006523CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID132375139220240509162259.0001): Bearing, Sleeve, Flanged. CORE PARTS LLC · PMA PQ05326NM · Replaces 3006523 · Mar 25, 2024 - [3008676CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID120421035120240509162301.0001): Bearing, Sleeve, Flanged. CORE PARTS LLC · PMA PQ05326NM · Replaces 3008676 · Mar 25, 2024 - [3008676CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID120421035120240509162301.0001): Bearing, Sleeve, Flanged. CORE PARTS LLC · PMA PQ05326NM · Replaces 3008676 · Mar 25, 2024 - [3003987CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID125662034220231204145325.0001): Pin, Lock. CORE PARTS LLC · PMA PQ05326NM · Replaces 3003987 · Aug 1, 2023 - [3003987CP](https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID125662034220231204145325.0001): Pin, Lock. CORE PARTS LLC · PMA PQ05326NM · Replaces 3003987 · Aug 1, 2023 All of them: https://openairdocs.org/engine/pratt-whitney-pt6a-20a-series/pma.md --- 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.