# N642: 1968 Mckinnon G-21C - Status: Valid registration - Airframe: [Mckinnon G-21C](https://openairdocs.org/model/mckinnon-g-21c) (registry code 5550104, 9 seats) - Engine: [Pratt & Whitney PT6A series](https://openairdocs.org/engine/pratt-whitney-pt6a-series) (registry code 52032) - Data sheets: [TCDS 4A24](https://openairdocs.org/tcds/4A24) (Atlantic Coast Seaplanes LLC) (OpenAirDocs) - Serial number: 1204 - Year built: 1968 - Type: Fixed wing multi engine - Engine type: Turbo-prop - Airworthiness: Standard, normal - Airworthiness date: January 8, 1993 - Certificate issued: May 7, 2025 - Expires: May 31, 2032 - Mode S code: A86CA8 - Registered owner: [Snow Goose Aviation LLC](https://openairdocs.org/faa-owner/SNOW%20GOOSE%20AVIATION%20LLC) - Location: [Anchorage, AK](https://openairdocs.org/faa-place/AK/Anchorage) - Owner type: LLC - Owner's area on the map: 61.1151° N, 149.6159° W: Placed by OpenAirDocs at the center of ZIP code 99507, within about 4 miles (OpenAirDocs). The owner's mailing address, not where the aircraft is based - FAA registry: https://registry.faa.gov/AircraftInquiry/Search/NNumberResult?nNumberTxt=642 - Page: https://openairdocs.org/aircraft/N642 From the FAA registry file of October 24, 2026. ADs below are matched by the registry's airframe and engine model codes. They may apply; each AD's applicability can narrow it by serial number, part number or installed equipment. This is not a compliance determination. The registry lists only the engine series, so ADs for every Pratt & Whitney PT6A model are included. ## ADs that may apply (OpenAirDocs): 27 in force ### Matched by airframe (Mckinnon G-21C) - [AD 73-07-05](https://openairdocs.org/ad/73-07-05): Elevator or Rudder Torque Tube Assys · Atlantic Coast Seaplanes G-21C, G-21D, G-21E and 1 more ### Matched by engine (Pratt & Whitney PT6A series) - [AD 2024-04-51](https://openairdocs.org/ad/2024-04-51): Turbine Section · Pratt & Whitney Canada PT6A-64, PT6A-66, PT6A-66A and 17 more. Effective Mar 28, 2024 - [AD 2022-08-13](https://openairdocs.org/ad/2022-08-13): Turbine Section · Pratt & Whitney Canada PT6A-34, PT6A-34B, PT6A-34AG and 2 more. Effective May 27, 2022 - [AD 2016-05-13](https://openairdocs.org/ad/2016-05-13): Corrosion and perforation of the two-ply Cu-Be bellows in Woodward FCUs. · Pratt & Whitney Canada PT6A-60AG, PT6A-65AG, PT6A-67AF and 1 more. Effective Apr 22, 2016 - [AD 2014-17-08 R1](https://openairdocs.org/ad/2014-17-08-R1): Compressor turbine (CT) blades · Pratt & Whitney Canada PT6A-114 and PT6A-114A. Effective Jun 5, 2015 - [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 2012-09-10](https://openairdocs.org/ad/2012-09-10): First stage sun gears · Pratt & Whitney Canada PT6A-110, PT6A-112, PT6A-114 and 12 more. Effective May 23, 2012 - [AD 2011-25-12](https://openairdocs.org/ad/2011-25-12): Sun gear · Pratt & Whitney Canada PT6A-15AG, PT6A-27, PT6A-28 and 4 more. Effective Dec 28, 2011 - [AD 2011-20-51](https://openairdocs.org/ad/2011-20-51): Gears · Pratt & Whitney Canada PT6A-15AG, PT6A-27, PT6A-28 and 4 more. Effective Nov 1, 2011 - [AD 2004-25-18](https://openairdocs.org/ad/2004-25-18): Propeller governor assemblies · Pratt & Whitney Canada PT6A-60A and PT6A-65B. Effective Jan 18, 2005 - [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 2001-20-01](https://openairdocs.org/ad/2001-20-01): Compressor Bleed Valve Assembly · Pratt & Whitney Canada PT6A-114A and PT6A-25C. Effective Nov 5, 2001 - [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 95-13-08](https://openairdocs.org/ad/95-13-08): Compressor Turbine Disk · Pratt & Whitney Canada PT6A-67D. Effective Jul 12, 1995 - [AD 93-23-06](https://openairdocs.org/ad/93-23-06): Airframe Chip Detector Flag System · Pratt & Whitney Canada PT6A-50. Effective Jan 26, 1994 - [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 90-12-05](https://openairdocs.org/ad/90-12-05): Engine Overhaul · Pratt & Whitney Canada PT6A-15AG, PT6A-27, PT6A-28 and 3 more. Effective May 30, 1990 - [AD 86-10-05](https://openairdocs.org/ad/86-10-05): First Stage Compressor Hub · Pratt & Whitney Canada PT6A-42. Effective Jun 5, 1986 - [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 80-04-02](https://openairdocs.org/ad/80-04-02): Push-Pull Control Terminal · Pratt & Whitney Canada PT6A-20, PT6A-6A, PT6A-6B and 1 more. Effective Feb 8, 1980 - [AD 78-17-07](https://openairdocs.org/ad/78-17-07): Fuel Control Unit · Pratt & Whitney Canada PT6A-38, PT6A-41 and PT6A-45A. Effective Aug 31, 1978 - [AD 78-12-04](https://openairdocs.org/ad/78-12-04): No. 2 Bearing Pressure Oil Transfer Tube Assembly · Pratt & Whitney Canada PT6A-38, PT6A-41 and PT6A-45A. Effective Jun 19, 1978 - [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 - [AD 70-16-01](https://openairdocs.org/ad/70-16-01): Turbo Propeller Governors · Pratt & Whitney Canada PT6A-11, PT6A-11AG, PT6A-15AG and 5 more. Effective Aug 4, 1970 - [AD 69-23-06](https://openairdocs.org/ad/69-23-06): Fuel Pumps · Pratt & Whitney Canada PT6A-20, PT6A-27, PT6A-28 and 4 more. Effective Nov 15, 1969 - [AD 68-05-03](https://openairdocs.org/ad/68-05-03): Reverse Mode · Pratt & Whitney Canada PT6A-20 and PT6A-6B. Effective Feb 28, 1968 ### Historical (superseded or no longer in force) - [AD 2014-17-08](https://openairdocs.org/ad/2014-17-08) (historical): Compressor turbine (CT) blades · Pratt & Whitney Canada PT6A-114 and PT6A-114A. Effective Oct 8, 2014 - [AD 88-24-02](https://openairdocs.org/ad/88-24-02) (historical): Airframe Chip Detector Flag System · Pratt & Whitney Canada PT6A-50 ## Information bulletins (advisory) (5 in force) - [SAIB NE-15-21](https://openairdocs.org/saib/NE-15-21): Fuel Injector Nozzle. Issued Aug 19, 2015 - [SAIB NE-12-04](https://openairdocs.org/saib/NE-12-04): Turbine/ Turboprop Engine: Reduction Gearbox. Issued Nov 1, 2011 - [SAIB NE-10-47](https://openairdocs.org/saib/NE-10-47): Turbine Engine Compressor Section. Issued Aug 30, 2010 - [SAIB NE-06-34](https://openairdocs.org/saib/NE-06-34): . Issued Mar 21, 2006 - [SAIB CE-03-24](https://openairdocs.org/saib/CE-03-24): . Issued Feb 19, 2003 ## NTSB investigations None matched to N642. ## FAA accident and incident reports (1) 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. - [Incident 19940903036539I](https://openairdocs.org/incident/19940903036539I), Sep 3, 1994: Mckinn G21C (N642), Milwaukee, WI, Minor damage. Veered off runway landing and ground looped. Damaged floats. Blamed a brake locked. Taxi tested later ok. Departed. ## Service difficulty reports None filed for this aircraft. Matched to this aircraft by N-number and event date, checked against the reported serial number, make and model. ## Service difficulty reports on N642 not matched to an aircraft (2) They name N642, but no registry record covers the date, the aircraft registered then was built later, or the report describes another aircraft. - [SDR HNAA2019090300248](https://openairdocs.org/sdr/HNAA2019090300248), Sep 1, 2019: LIGHT. INOPERATIVE. NDIS 642 33-51 0007420 01SEP19 RIC CLOSE EMERGENCY FLOOR LIGHT @ ROW 1/GALLEY INOP. FACT 01SEP19 10:18 RIC R&R EMERGENCY FLOOR LIGHT AT ROW 1/GALLEY IN REF TO A - [SDR HNAA2019090300247](https://openairdocs.org/sdr/HNAA2019090300247), Sep 1, 2019: SIGN. INOPERATIVE. NDIS 642 33-31 0007470 01SEP19 RIC CLOSE EMERGENCY EXIT SIGN ABOVE SERVICE DOOR INOP FACT 01SEP19 10:25 RIC R&R EMERGENCY EXIT SIGN ABOVE SERVICE DOOR IAW AMM 3 ## STCs that may be installed (OpenAirDocs) (81, first 50) Approved for this aircraft's airframe or engine model, in force first, then newest. The registry doesn't record which STCs an aircraft has; its records do. ### Approved for the airframe (Mckinnon G-21C) - [STC SA02571SE](https://openairdocs.org/stc/SA02571SE): Installation of Garmin G500/G600 TXi Integrated Avionics System (Primary Flight Display, Multi-Function Display, and Engine Indicating System Display). Garmin International Inc - [STC SA04837NY](https://openairdocs.org/stc/SA04837NY): Installation of AeroLED's Holdings, LLC., position lights, navigation lights, strobe lights and beacon lights. AeroLED's Holdings, LLC - [STC SA02019SE-D](https://openairdocs.org/stc/SA02019SE-D): Installation of Garmin Model GTN 625/635/650; 725/750 Navigation System. Garmin International Inc - [STC SA02679SE](https://openairdocs.org/stc/SA02679SE): Increase in gross weight to 12,500 pounds. Snow Goose Aviation LLC - [STC SA02658SE](https://openairdocs.org/stc/SA02658SE): Installation of Garmin GI 275 Multi-Function Display System. Garmin International Inc - [STC SA04776NY](https://openairdocs.org/stc/SA04776NY): The HIPEC Covering and Finishing System must be performed and maintained. HIPEC Aircraft Coatings Inc - [STC SA01714WI](https://openairdocs.org/stc/SA01714WI): Installation of a Garmin transponders: (a) GTX 330/330D/33/33D with ADS-B Out functionality; (b) GTX 335/335R/345/345R with ADS-B Out and In functionality; or (c) GTX 335R/345R with ADS-B Out functionality in select airplanes installed with G950/G1000 systems. Garmin International Inc - [STC SA00344BO PAGE 1](https://openairdocs.org/stc/SA00344BO%20PAGE%201): Installation of Parmetheus Plus LED PAR36 and PAR46 taxi and landing lights. Whelen Aerospace Technologies - [STC SA02153LA-D PAGE 1](https://openairdocs.org/stc/SA02153LA-D%20PAGE%201): Installation of Garmin G600 Primary Flight Display (PFD) and Multifunction Display (MFD) System. Garmin International Inc - [STC SA02212AK](https://openairdocs.org/stc/SA02212AK): Replacement of existing landing and/or taxi light reflector and bulbs with high intensity discharge (HID) lighting systems. Seaplanes North LLC - [STC SA00382BO](https://openairdocs.org/stc/SA00382BO): Installation of Globalstar Antenna and Cradle provisions to support a Globalstar GPS-1700 in non-composite airplanes. Avidyne Corporation - [STC SA00343BO](https://openairdocs.org/stc/SA00343BO): Installation of a single configuration or a dual configuration Avidyne Corporation Integrated Flight Display, Model IFD540 loaded with Release 10.0 software (or later FAA approved release). Avidyne Corporation - [STC SA00352BO PAGE 1](https://openairdocs.org/stc/SA00352BO%20PAGE%201): Installation of an Avidyne Corporation Mode A/C/S Transponder with ADS-B Out capability, Model AXP340 loaded with Version 3.13 software (or later FAA approved version),. Avidyne Corporation - [STC SA01734SE](https://openairdocs.org/stc/SA01734SE): Application of Stewart Systems synthetic fabric covering system to aircraft fuselage, wings, tail surfaces, control surfaces and related parts. Andrew D. Humphrey - [STC SA02119SE PAGE 1](https://openairdocs.org/stc/SA02119SE%20PAGE%201): Installation of Garmin GDL 88 ADS-B UAT Transceiver System. Garmin International Inc - [STC SA02121SE](https://openairdocs.org/stc/SA02121SE): Installation of Garmin GTS 825 (TAS) or GTS 855 (TCAS I) Traffic System. Garmin International Inc - [STC ST02540AT-D](https://openairdocs.org/stc/ST02540AT-D): Installation of replacement fuel tank sealant system. FFC Manufacturing - [STC SA593CH](https://openairdocs.org/stc/SA593CH): Install Champion SlickSTART magneto booster system. Champion Aerospace LLC - [STC SA1751WE](https://openairdocs.org/stc/SA1751WE): Increase in main fuel tank capacity to 336 gallons. Atlantic Coast Sea Planes LLC - [STC SA1320WE](https://openairdocs.org/stc/SA1320WE): G-21C: Installation of two United Aircraft of Canada Drawing List Model PT6A-20 engines. G-21D: installation of two United Aircraft of Canada Ltd Model PT6A-20 engines, Alvarez-Calderon wing flaps, and related changes. Atlantic Coast Sea Planes LLC - [STC SA02168AK](https://openairdocs.org/stc/SA02168AK): Installation of hourmeter airspeed switch. For unpressurized aircraft only. Pressurized aircraft must have pressurization system deactivated. Avalaska Inc - [STC SA3494SW-D](https://openairdocs.org/stc/SA3494SW-D): Installation of a century automatic flight system. Century Flight Systems Inc - [STC SA1351WE](https://openairdocs.org/stc/SA1351WE): Replace existing fabric on wings, fuselage, empennage, and/or control surfaces, with Ceconite101 material. (262A Series -12). Ceconite Inc - [STC SA02153LA-D](https://openairdocs.org/stc/SA02153LA-D) (historical): Installation of Garmin G600 Primary Flight Display (PFD) and Multifunction Display (MFD) System. Garmin International Inc ### Approved for the engine (Pratt & Whitney PT6A series) - [STC SE12225AC](https://openairdocs.org/stc/SE12225AC): This STC will incorporate P&W 1700 rpm propeller reduction gearbox on P&WC engines to allow 1700 rpm propeller installation. High Cotton Aircraft Conversions, LLC. Lists PT6A-41 - [STC SE00010EN](https://openairdocs.org/stc/SE00010EN): Instructions for Continued Airworthiness for the PT6A-25, and, -25A 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. Lists PT6A-25 - [STC SE000010EN](https://openairdocs.org/stc/SE000010EN): Instructions for Continued Airworthiness for the PT6A-25 and PT6A-25A 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. Lists PT6A-25 - [STC SE000011EN](https://openairdocs.org/stc/SE000011EN): Instructions for Continued Airworthiness for the PT6A-25C 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. Lists PT6A-25C - [STC SE00001EN](https://openairdocs.org/stc/SE00001EN): Engines will be maintained IAW 'Maintenance or Reliable Engines(MORE) Program,' Rev 2, 8/16/95. MORE Company Inc. Lists PT6A-38 - [STC SE00002EN](https://openairdocs.org/stc/SE00002EN): Instructions for Continued Airworthiness for the PT6A-34, -34AG, -34B, -36, -114, -114A, -116, -135, and -135A 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. Lists PT6A-114 - [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. Lists PT6A-20 - [STC SE00004EN](https://openairdocs.org/stc/SE00004EN): Instructions for Continued Airworthiness for the PT6A-11, -11AG, -15AG, -110 and-112 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. Lists PT6A-11 - [STC SE00006EN](https://openairdocs.org/stc/SE00006EN): Instructions for Continued Airworthiness for the PT6A-45A, -45B, and, -45R 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. Lists PT6A-45A - [STC SE00011EN](https://openairdocs.org/stc/SE00011EN): Instructions for Continued Airworthiness for the PT6A-25C engine model 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. Lists PT6A-25C - [STC SE000EN](https://openairdocs.org/stc/SE000EN): Engines will be maintained IAW 'Maintenance or Reliable Engines(MORE) Program,' Rev 4, dated 8/16/95. MORE Company Inc. Lists PT6A-21 - [STC SE10947SC](https://openairdocs.org/stc/SE10947SC): The conversion of the Pratt & Whitney Canada, Model PT6A-21 to a PT6A-28 turboprop engine. Prime Turbines. Lists PT6A-21 - [STC SE00482SE](https://openairdocs.org/stc/SE00482SE): Incorporation of turbine engine into a twin power section turboprop assembly. Fifty-Ten-Yankee LLC. Lists PT6A-114A - [STC SE10552SC](https://openairdocs.org/stc/SE10552SC): Conversion of Pratt & Whitney Canada Corp. Model PT6A-27 or -28 to a Model PT6A-34 turboprop engine. Prime Turbines LLC. Lists PT6A-27 - [STC SE11139SC](https://openairdocs.org/stc/SE11139SC): The conversion of the Pratt & Whitney Canada, Model PT6A-135 to a PT6A-135A turboprop engine. Airforce Turbine Service. Lists PT6A-135 - [STC SE11141SC](https://openairdocs.org/stc/SE11141SC): The conversion of the Pratt & Whitney Canada, Model PT6A-15AG to a PT6A-34AG turboprop engine. RT Turbines Inc. Lists PT6A-15AG - [STC SE02170AT](https://openairdocs.org/stc/SE02170AT): Installation of Pc Safety Valve Kit. Bell Helicopter Textron Inc. Lists PT6A-27 - [STC SE11095SC](https://openairdocs.org/stc/SE11095SC): The conversion of the Pratt & Whitney Canada, Model PT6A-27 to a PT6A-34 turboprop engine. R.T. Turbines, Inc. Lists PT6A-27 - [STC SE01624WI](https://openairdocs.org/stc/SE01624WI): Conversion of Pratt & Whitney Canada, Model PT6A-60A to a North Star Aviation PT6A-60AG turboprop engine. Data required: 1. A copy of this certificate 2. North Star Aviation document, NSA No. 1200, Turboprop Engine Conversion of PT6A-60A Model to PT6A-60AG Configuration per FAA Approved STC , dated March 15, 2011, or later FAA approved revision 3. The ICA supplement for North Star Aviation PT6A-60AG models, Instructions for Continued Airworthiness, NSA No. 1200-ICA, Rev NC, dated March 9, 2011 or later applicable revision. North Star Aviation Inc. Lists PT6A-60A - [STC SE02837NY](https://openairdocs.org/stc/SE02837NY): The conversion of the Pratt & Whitney Canada PT6A-21 engine to operate as a PT6A-28 engine to be done. Rocky Mountain Aircraft. Lists PT6A-21 - [STC SE02688NY](https://openairdocs.org/stc/SE02688NY): This modification would incorporate improved compressor components into the Pratt & Whitney PT6A-28 engine from the PT6A-135A engine. Standard Aero Limited. Lists PT6A-28 - [STC SE02290NY](https://openairdocs.org/stc/SE02290NY): Conversion of a Pratt & Whitney Canada PT6A-21 engine to operate as a PT6A-27 or -28 engine. Vector Aerospace Engine Services Atlantic Inc. Lists PT6A-21 - [STC SE02501NY](https://openairdocs.org/stc/SE02501NY): Conversion of the PT6A-11 engine. Vector Aerospace Engine Services Atlantic Inc. Lists PT6A-11 - [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. Lists PT6A-11 - [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. Lists PT6A-11 - [STC SE8652SW](https://openairdocs.org/stc/SE8652SW): Installation of a flexible hose from the Propeller Primary Governor to the Fuel Control Unit. Air Tractor Inc. Lists PT6A-45R All 81: https://openairdocs.org/aircraft/N642/stcs.md ## Earlier aircraft with N642 The FAA can reassign an N-number once a registration is cancelled. These aircraft carried N642 before. - [Cancelled 1930-05-02](https://openairdocs.org/deregistered/N642-1930-05-02): Morse Thomas SCOUT, S/N 1192. Owner: [Byrd L S](https://openairdocs.org/faa-owner/BYRD%20L%20S), [Fort Worth, TX](https://openairdocs.org/faa-place/TX/Fort%20Worth) ## Related - Other Mckinnon G-21C aircraft: https://openairdocs.org/model/mckinnon-g-21c/aircraft.md - The Pratt & Whitney PT6A series engine: https://openairdocs.org/engine/pratt-whitney-pt6a-series.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.