# Allison 250-C20F

- Type: Engine model (FAA registry)
- Registry code: 03087
- Manufacturer (registry): ALLISON
- Model: 250-C20F
- Engine type: Turbo-shaft
- Power: 420 hp
- Data sheet: [TCDS E4CE](https://openairdocs.org/tcds/E4CE) (OpenAirDocs)
- Holder: Rolls-Royce Corporation
- Installed in: 1 registered aircraft
- Page: https://openairdocs.org/engine/allison-250-c20f

Model codes come from the FAA registry's reference file.

## 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 2022-10-06](https://openairdocs.org/ad/2022-10-06): Turbine Section · Rolls-Royce 250-C20, 250-C20B, 250-C20C (T63-A-720) and 9 more. Effective Jun 28, 2022
- [AD 2018-13-01](https://openairdocs.org/ad/2018-13-01): Turbine Governor · Rolls-Royce 250-C10 (T63-A-5), 250-C18, 250-C18A and 24 more. Effective Aug 16, 2018
- [AD 2006-16-04](https://openairdocs.org/ad/2006-16-04): Inspection of the fuel nozzle screen · Rolls-Royce 250-B15A, 250-B15E, 250-B15G and 43 more. Effective Sep 7, 2006
- [AD 2006-13-06](https://openairdocs.org/ad/2006-13-06): Gas producer rotor assembly tie bolts · Rolls-Royce 250-B17, 250-B17B, 250-B17C and 16 more. Effective Jul 26, 2006
- [AD 2005-10-13](https://openairdocs.org/ad/2005-10-13): Turbine energy absorbing ring · Rolls-Royce 250-B17B, 250-B17C, 250-B17D and 7 more. Effective Jun 22, 2005
- [AD 2004-26-09](https://openairdocs.org/ad/2004-26-09): Compressor Adaptor Couplings · Rolls-Royce 250-B17, 250-B17B, 250-B17C and 8 more. Effective Feb 8, 2005
- [AD 2001-24-12](https://openairdocs.org/ad/2001-24-12): Helical Torquemeter Gearshaft Assembly · Rolls-Royce 250-B17, 250-B17C, 250-B17D and 13 more. Effective Dec 19, 2001
- [AD 98-24-28](https://openairdocs.org/ad/98-24-28): Main Fuel Control Bellows · Rolls-Royce 250-B15A, 250-B15E, 250-B15G and 36 more. Effective Jan 7, 1999
- [AD 96-19-01](https://openairdocs.org/ad/96-19-01): Superior Air Parts Manufacture Approval (PMA) Bearings · Rolls-Royce 250-B15G, 250-B17F, 250-B17F/1 and 17 more. Effective Sep 26, 1996
- [AD 88-17-01](https://openairdocs.org/ad/88-17-01): Fuel Controls · Rolls-Royce 250-B17, 250-B17B, 250-B17C and 26 more. Effective Mar 1, 1989
- [AD 83-03-02 R1](https://openairdocs.org/ad/83-03-02-R1): Slotted Third Stage Turbine Wheels · Rolls-Royce 250-B17, 250-B17B, 250-B17C and 5 more. Effective Feb 28, 1984
- [AD 82-24-05](https://openairdocs.org/ad/82-24-05): Control Assembly and Power Turbine Governor Assembly · Rolls-Royce 250-B15A, 250-B15E, 250-B15G and 43 more. Effective Nov 26, 1982
- [AD 77-15-12](https://openairdocs.org/ad/77-15-12): Power Turbine Coupling Nut · Rolls-Royce 250-B15A, 250-B15E, 250-B15G and 23 more. Effective Sep 23, 1977

Historical (superseded or no longer in force):

- [AD 2017-18-14](https://openairdocs.org/ad/2017-18-14) (historical): Turbine Section · Rolls-Royce 250-C20, 250-C20B, 250-C20F and 8 more. Effective Oct 13, 2017
- [AD 2015-02-22](https://openairdocs.org/ad/2015-02-22) (historical): Repetitive visual inspections · Rolls-Royce 250-B17, 250-B17B, 250-B17C and 15 more. Effective Mar 9, 2015
- [AD 2004-24-09](https://openairdocs.org/ad/2004-24-09) (historical): Fuel nozzle · Rolls-Royce 250-B15A, 250-B15E, 250-B15G and 40 more. Effective Jan 5, 2005
- [AD 2001-20-51](https://openairdocs.org/ad/2001-20-51) (historical): Helical Torquemeter Gearshaft Assembly · 250-B17, 250-B17C, 250-B17D and 12 more

## Registered aircraft (1)

- [N355ER](https://openairdocs.org/aircraft/N355ER): [Elite Rotorcraft LLC](https://openairdocs.org/faa-owner/ELITE%20ROTORCRAFT%20LLC), [Mt Juliet, TN](https://openairdocs.org/faa-place/TN/Mt%20Juliet), built 1990, S/N 5436

## NTSB investigations (1)

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 ERA12FA563](https://openairdocs.org/ntsb/ERA12FA563), Sep 15, 2012: Aerospatiale AS 355F1 (N58020), West Windsor, NJ, substantial damage, 1 fatal. Probable cause: Disconnection of the upper rod end from the fore/aft servo due to severely worn threads, which resulted in a loss of control and separation of a main rotor blade during cruise flight. Contributing to…

## 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.

- [Accident 20120915021309A](https://openairdocs.org/incident/20120915021309A), Sep 15, 2012: Aerospatiale AS 355F1 (N58020), West Windsor, NJ, Destroyed, 1 fatal. On September 15, 2012, about 1200 eastern daylight time, an Aerospatiale as 355F1, N58020, operated by analar corporation, was destroyed when it impacted…

## Service difficulty reports (87, newest 50)

As reported by operators and repair stations, by the model named in the report.

- [SDR TLLA205070200139](https://openairdocs.org/sdr/TLLA205070200139), Jun 26, 2025: ENGINE. MAKING METAL. #1 ENGINE CHIP LIGHT ILLUMINATED DURING FLIGHT. PILOT LANDED AT FIRST SAFEST SPOT AT SOUTHWEST WYOMING REGIONAL AIRPORT WITH NO INCIDENT. GROUNDED AC. SENT MECH
- [SDR CA190528012](https://openairdocs.org/sdr/CA190528012), May 24, 2019: GEARBOX. MAKING METAL. (CAN) MAIN GEARBOX BEVEL REDUCTION (MGB) CHIP LIGHT ON AIRCRAFT STARTUP, AIRCRAFT GROUNDED. DURING STARTUP PILOT NOTICED, MGB CHIP LIGHT ILLUMINATED. PILOT SHUT
- [SDR H0CR2018050101](https://openairdocs.org/sdr/H0CR2018050101), Apr 26, 2018: COMPRESSOR. DELAMINATED. NR 1 AND 2 ENGINE POWER CHECKS WERE TRENDING DOWN. DURING ROUTINE 300HR/12MONTH INSPECTION, FOUND EXCESSIVE DELAMINATION OF THE LINING OF THE COMPRESSOR CASE HA
- [SDR CA150603011](https://openairdocs.org/sdr/CA150603011), Jun 3, 2015: SERVO. FAILED. (CAN) RIGHT MAIN SERVO PN 31026-110 TSO 0.0 RETURNED FROM OVERHAULED. SERVO INSTALLED ON AIRCRAFT & FAILED ELECTRICAL SERVO FUNCTION TEST. SERVO PN 31026-110 RE
- [SDR CA150411001](https://openairdocs.org/sdr/CA150411001), Mar 11, 2015: CONTROL CABLE. FROZEN. (CAN) AIRCRAFT WAS PARKED OUTSIDE ON COLD MORNING. DURING START, PIC NOTED NOT BEING ABLE TO BRING ENGINES FROM IDLE TO FLIGHT RPM. SUBSEQUENT INSPECTION OF CON
- [SDR VMIA201506101671](https://openairdocs.org/sdr/VMIA201506101671), Jan 26, 2015: BEARING. FAILED. ENGINE FAILURE INFLIGHT DUE TO COMPRESSOR BEARING NR 2 FAILURE.
- [SDR CA111125001](https://openairdocs.org/sdr/CA111125001), Nov 18, 2014: LINE. CRACKED. (CAN) FLARED END OF OIL PRESSURE DELIVERY TUBE CRACKED UNDER FERRULE, CAUSING OIL PRESSURE LOSS AND SUBSEQUENT IN-FLIGHT SHUTDOWN OF RT ENGINE. US REG NR N355AG
- [SDR 2014F00158](https://openairdocs.org/sdr/2014F00158), Sep 25, 2014: FIRE WARNING. ACTIVATED. LEFT ENGINE FIRE LIGHT ILLUMINATED IN FLIGHT.
- [SDR CA150108008](https://openairdocs.org/sdr/CA150108008), Jul 9, 2014: BEARING. FAILED. (CAN) ENGINE CHIP LIGHT ILLUMINATED. FOUND NR 5 BEARING BRINELLED.
- [SDR CA130603019](https://openairdocs.org/sdr/CA130603019), May 23, 2013: SHAFT. DAMAGED. (CAN) IN FLIGHT SURGE ON NR 1 ENGINE DURING MAINTENANCE OPERATIONS, THE FCU WAS REMOVED AND FOUND INPUT SHAFT DAMAGED.
- [SDR 2012FA0000808](https://openairdocs.org/sdr/2012FA0000808), Dec 10, 2012: SERVO CONTROL. WORN. DURING THE ACCIDENT INVESTIGATION, ABNORMALITIES IN THE FORE & AFT SERVO ACTUATOR WERE NOTED. THE SERVO ACTUATOR WAS SENT TO THE NTSB LAB FOR EXAMINATION IN WHI
- [SDR 2011F00023](https://openairdocs.org/sdr/2011F00023), Jan 31, 2011: FIRE DETECTOR. FALSE INDICATION. WHILE FLYING TO DESTINATION, THE LT ENGINE FIRE LIGHT ILLUMINATED. 1 PASSENGER WAS ABOARD. PILOTS MADE A PRECAUTIONARY DIVERSION TO OTHER AIRPORT WHICH WAS THE 
- [SDR E30A20090704001](https://openairdocs.org/sdr/E30A20090704001), Jul 4, 2009: ENGINE. MAKING METAL. NR 1 ENGINE CHIP LIGHT ILLUMINATED ON MASTER WARNING PANEL. CHIPS FOUND ON DETECTORS, ENGINE REMOVED FOR REPAIR.
- [SDR CA070912008](https://openairdocs.org/sdr/CA070912008), Sep 10, 2007: PUMP. DEFECTIVE. (CAN) ENGINE AUTO-REIGNITION ACTIVATED IN FLIGHT. REPORTS OF SOFT (BANG) PRECEEDING DECEL. INVESTIGATION REVEALED AIR IN FUEL SYSTEM, SUBSEQUENT TROUBLESHOOTING
- [SDR BAQA20070011](https://openairdocs.org/sdr/BAQA20070011), Apr 15, 2007: WIRE HARNESS. FATIGUED. DURING CRUISE FLIGHT THE RT (NR 2) ENGINE FIRE WARNING LIGHT ILLUMINATED WITH NO SECONDARY INDICATION OBSERVED. AIRCRAFT LANDED SAFELY AT A NEARBY EMS HELIPAD W
- [SDR BAQA200700005](https://openairdocs.org/sdr/BAQA200700005), Mar 1, 2007: COMPRESSOR. SEIZED. PILOT WENT TO START NR 1 ENGINE. ENGINE WOULD NOT TURN. FOUND ENGINE SEIZED. REMOVED AND REPLACED ENGINE ASSEMBLY. BROUGHT ENGINE TO ARC, DISASSEMBLED ENGINE AN
- [SDR MHI2005F00000](https://openairdocs.org/sdr/MHI2005F00000), Jul 21, 2005: SKIN. CRACKED. (REF NR: 104942) DURING INSPECTION, FOUND THE UPPER STABILIZER FIN, RT LWR DOUBLER AND NOSE SKIN CRACKED FROM THE 2ND FORWARD RIVET OF THE DOUBLER ACCROSS THE N
- [SDR HE89099847](https://openairdocs.org/sdr/HE89099847), Mar 17, 2005: STARTER GEN. UNSERVICEABLE. STARTER WOULDN'T START ENGINE
- [SDR CA040909005](https://openairdocs.org/sdr/CA040909005), Sep 5, 2004: PITCH LINK. BROKEN. (CAN) DURING CRUISE FLIGHT PILOT FELT SUDDEN VIBRATION IN THE M/R FLIGHT CONTROLS SYSTEM. A/C LANDED AT FIRST SUITABLE SITE. UPON INSPECTION, AME DISCOVERED THA
- [SDR CA040811008](https://openairdocs.org/sdr/CA040811008), Aug 5, 2004: BLOWER. DAMAGED. (CAN) DURING OPERATION A NOISE WAS HEARD FROM THE BACK OF THE AIRCRAFT, AIRCRAFT WAS LANDED AND DURING INSPECTION TO DETERMINE THE ORIGIN OF THE SOUND IT WAS NO
- [SDR CA040324003](https://openairdocs.org/sdr/CA040324003), Mar 7, 2004: BELLCRANK. DAMAGED. (CAN) TAIL ROTOR BELLCRANK FOUND WITH WEAR DAMAGE ON INSIDE YOKE AREA AT THE ATTACHMENT BOLT WITH THE TAIL ROTOR PITCH CHANGE SPIDER. THE WEAR CORRESPONDS TO TH
- [SDR CA040324004](https://openairdocs.org/sdr/CA040324004), Mar 7, 2004: RING. WORN. (CAN) ALL 3 DROOP RING YOKES WERE FOUND WITH WEAR DAMAGE ON OUTSIDE DIAMETER. THIS WEAR CORRESPONDS WITH WEAR FOUND ON THE DROOP RING CONTACT FITTINGS P/N 350A3
- [SDR BAQA089603](https://openairdocs.org/sdr/BAQA089603), Nov 5, 2003: FUEL CONTROL. MALFUNCTIONED. FUEL CONTROL PRODUCING HUNG STARTS, OCCURING BETWEEN 50 PERCENT AND 60 PERCENT. REPLACED WITH SERVICEABLE UNIT. 11/10/03
- [SDR CA031114007](https://openairdocs.org/sdr/CA031114007), Oct 16, 2003: CONNECTOR. BURNED. (CAN) WHILE THE AIRCRAFT WAS IN CRUISE FLIGHT, A BURNING ODOR WAS NOTICED IN THE CABIN. THE PILOT LANDED THE AIRCRAFT UNEVENTFULLY. THE BURNING ODOR WAS TRACED 
- [SDR BAQA089111](https://openairdocs.org/sdr/BAQA089111), Sep 12, 2003: PUMP. LEAKING. LEAKING FUEL FROM DRIVESHAFT. REPLACED WITH SERVICEABLE UNIT.
- [SDR AUS20030944](https://openairdocs.org/sdr/AUS20030944), Sep 11, 2003: SKIN. CRACKED. (AUS) TAILBOOM SKIN CRACKED IN AREA LOCATED AFT OF THE TAIL ROTOR GEARBOX. CRACK ORIGINATED FROM RIVET HOLE IN TAIL ROTOR GEARBOX COWL BRACKET. CRACKED HAD EXTE
- [SDR CA040806008](https://openairdocs.org/sdr/CA040806008), Aug 30, 2003: PLANETARY GEAR. SPALLED. (CAN) EPI CYCLIC WAS MAKING METAL. SOURCE WAS THE PLANET GEAR INNER RACE WAS SPALLING AND MAKING METAL.
- [SDR BAQA088838](https://openairdocs.org/sdr/BAQA088838), Aug 25, 2003: TRANSMITTER. INOPERATIVE. TORQUE TRANSMITTER IS INOPERATIVE. REPLACED WITH SERVICEABLE UNIT.
- [SDR CA030617002](https://openairdocs.org/sdr/CA030617002), May 20, 2003: RIB. CRACKED. (CAN) DURING ROUTINE INSPECTION OF THE UPPER VERTICAL FIN ATTACHMENT FRAME, AME DISCOVERED RIB TO BE CRACKED. RIB REPLACED AS PER REPAIR MANUAL AND A/C RETURNED
- [SDR BAQA086321](https://openairdocs.org/sdr/BAQA086321), May 2, 2003: ADJUSTER. LOOSE. ENGINE N1 IDLE ADJUSTMENT SCREW HAS FREE MOVEMENT EITHER RIGHT HAND OR LEFT HAND. REPLACED WITH SERVICEABLE UNIT.
- [SDR CA030305003](https://openairdocs.org/sdr/CA030305003), Feb 28, 2003: NUT. LOOSE. (CAN) FLT CREW REPORTED THAT THE ROTOR BRAKE HAD NO EFFECT WHEN APPLIED. THE ROTOR BRAKE PACK WAS BEING INSPECTED AND TO HAVE SHIMS ADJUSTED WHEN THE OUT PUT FL
- [SDR BAQA082689](https://openairdocs.org/sdr/BAQA082689), Dec 27, 2002: GOVERNOR. MALFUNCTIONED. NR 2 ENGINE SN 841010 WOULD NOT TRIM. REPLACED WITH SERVICEABLE UNIT.
- [SDR BAQA081639](https://openairdocs.org/sdr/BAQA081639), Dec 12, 2002: ENGINE. MALFUNCTIONED. ENGINE FAILING POWER CHECK. REPLACED WITH SERVICEABLE UNIT.
- [SDR BAQA081640](https://openairdocs.org/sdr/BAQA081640), Dec 12, 2002: ENGINE. MALFUNCTIONED. ENGINE FAILING POWER CHECK. REPLACED WITH SERVICEABLE UNIT.
- [SDR CA021119003](https://openairdocs.org/sdr/CA021119003), Oct 8, 2002: HUB. CRACKED. (CAN) IT WAS NOTED THAT ON THE LAST SHUTDOWN A NOISE WAS BEING GENERATED FROM THE T/R BLADE ASSY REGION. IT WAS MENTIONED TO AN ENGINEER AND THEY CARRIED OUT A 
- [SDR CA021031003](https://openairdocs.org/sdr/CA021031003), Sep 24, 2002: BEARING. WORN. (CAN) AIRCRAFT IN CRUISE FLIGHT. PILOT NOTICED NG FLUCTUATION BETWEEN ENGINES, FOLLOWED BY ENGINE AT NR 2 CHIP LIGHT AND AN UNUSUAL NOISE & HOWL. PILOT SHUTDOWN
- [SDR CA020911002](https://openairdocs.org/sdr/CA020911002), Sep 3, 2002: BUSHING. DEBONDED. (CAN) ON A DAILY INSPECTION ONE BUSHING WAS FOUND TO BE DEBONDED. THE RETAINING BOLT WAS COMPLETELY PULED OUT OF THE STARFLEX. PILOT REPORTED NO ABNORMAL VIBRAT
- [SDR CA020828005](https://openairdocs.org/sdr/CA020828005), Aug 9, 2002: BEARING. ELONGATED. (CAN) NOISE WAS HEARD FROM OIL COOLER FAN AREA ON SHUTDOWN. INSPECTION REVEALED NR 6 T/R DRIVESHAFT SUPPORT BEARING BOLT HOLES HAD ELONGATED AND ALLOWED THE T/R
- [SDR 2002FA0000809](https://openairdocs.org/sdr/2002FA0000809), Jul 2, 2002: SPLINE ADAPTER. FRETTED. NEW COMPRESSOR SPLINE ADAPTER WAS PURCHASED FROM MANUFACTURER. SERVICE BULLETIN T-069 WAS PACKAGED WITH THE SPLINE ADAPTER, PROVIDING INSTRUCTIONS TO MODIFY THE
- [SDR CA020521008](https://openairdocs.org/sdr/CA020521008), May 14, 2002: BALL JOINT. WORN. (CAN) AFTER LAST FLIGHT INSPECTION THE LOWER ROD END WAS FOUND TO BE LOOSE. THE STAKED AREA AROUND THE BALL WAS WORN ENOUGH TO ALLOW IT TO COME OUT OF THE ROD E
- [SDR 2002FA0000789](https://openairdocs.org/sdr/2002FA0000789), Apr 5, 2002: SEAL. LEAKING. MECHANIC NOTICED DRIPPING OF FLUID WHILE AIRCRAFT TOOK OFF, RADIOED PILOT AND REQUESTED AIRCRAFT TO RETURN TO BASE. INSPECTION FOUND FUEL COMING FROM (SEAL DRAI
- [SDR AUS20020106](https://openairdocs.org/sdr/AUS20020106), Feb 14, 2002: HOOK. FAULTY. (AUS) SAFETY HARNESS USED BY CAMERAMAN FAULTY. SNAP HOOK ON HARNESS MAY UNDER SOME CIRCUMSTANCES HAVE THE SPRING LOADED SAFETY CATCH FORCED OPEN ALLOWING THE SN
- [SDR CA020213008](https://openairdocs.org/sdr/CA020213008), Feb 8, 2002: PUMP. MAKING METAL. (CAN) NR 1 ENGINE FUEL BOOST PUMP WAS MAKING TOO MUCH NOISE AND VIBRATING AS COMPARED TO NR 2 FUEL BOOST PUMP. INSPECTED THE NR 1 ENGINE DRIVEN FUEL PUMP FILTER
- [SDR AUS20020060](https://openairdocs.org/sdr/AUS20020060), Jan 25, 2002: GASKET. FAULTY. (AUS) MAIN ROTOR TRANSMISSION EPICYCLIC RING GEAR GASKET FAULTY. GASKET WAS EXTRUDING FROM BETWEEN THE UPPER AND LOWER CASES AND BREAKING INTO PIECES AND CAUSIN
- [SDR CA020128002](https://openairdocs.org/sdr/CA020128002), Jan 18, 2002: DOOR. SEPARATED. (CAN) IN CRUISE FLIGHT LT BAGGAGE DOOR DEPARTED THE AIRCRAFT, HITTING THE LT ENGINE COWL. THE AIRCRAFT WAS INSPECTED BY A QUALIFIED AME, BAGGAGE DOOR REPLACED, 
- [SDR 2001FA0000384](https://openairdocs.org/sdr/2001FA0000384), Oct 5, 2001: ADAPTER. CORRODED. COUPLING HAS EXCESSIVE FRETTING WEAR ON OD SURFACE. CONTINUED OPERATION MAY HAVE CAUSED FAILURE. SAME CONDITION NOTED ON OTHER COUPLINGS OF THE SAME PART NUMBER
- [SDR AUS20010846](https://openairdocs.org/sdr/AUS20010846), Jul 28, 2001: BEARING. DAMAGED. (AUS) NO2 ENGINE NO1 BEARING FAILED.
- [SDR 20010322CW015](https://openairdocs.org/sdr/20010322CW015), Feb 16, 2001: SPLINE ADAPTER. CRACKED. REMOVED ENGINE ASSEMBLY FOR OIL LEAKS. REMOVED COMPRESSOR AND TURBINE FROM GEAR BOX TO REPLACE SEALS AND ORINGS. INSPECTION OF SPLINE ADAPTOR FOUND CRACK RUNNIN
- [SDR 20001220SH008](https://openairdocs.org/sdr/20001220SH008), Dec 1, 2000: SPRING. BROKEN. DURING ROUTINE FLIGHT, PILOT EXPERIENCED A RAPID YAW TO THE RIGHT. NR 2 ENGINE, SN CAE-840415, SPOOLED DOWN TO FLIGHT IDLE AS THE RESULT OF THE NR 2 ENGINE GOVE
- [SDR AU001261](https://openairdocs.org/sdr/AU001261), Dec 1, 2000: CASE. CRACKED. (AUS) NR 2 ENGINE LOWER COMPRESSOR CASE HALF HAD DEBONDING OF THEPLASTIC BAND SECTION BETWEEN NR 3 AND NR 4 STAGES. EXCESSIVE SPOOL RUB EVIDENT ON THE PLASTIC S

All 87: https://openairdocs.org/engine/allison-250-c20f/reports.md

## STCs that may be installed (OpenAirDocs) (5)

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 SE5511NM](https://openairdocs.org/stc/SE5511NM): Installation of compressor discharge pressue (PC) valve. Bell Helicopter Textron 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 SE00027EN](https://openairdocs.org/stc/SE00027EN): Installation of Pratt & Whitney Engine Services Inc. Intellistart plus electronic control unit (ECU), P/N DPU-K-010 on the specified 250 engine models. Pratt & Whitney Engine Services Inc
- [STC ST00037AT](https://openairdocs.org/stc/ST00037AT): Unison igniter plugs, P/N 9044400-1. Unison Industries
- [STC SQ00338AT](https://openairdocs.org/stc/SQ00338AT): Unison igniter leads, P/N9048222-101, 102, 103, 104, 105, 106. Unison Industries

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