# NTSB CEN20LA159: Pilatus PC12, N477SS, Mesquite, TX, April 23, 2020 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Class 3 · Limited · Final report - Date: April 23, 2020, 16:00 local (21:00 UTC) - Place: Mesquite, TX - Coordinates: 32.761665, -96.531944 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=32.7617&lon=-96.5319&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-climb to cruise: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: Swiss Transportation Safety Investigation Board, Transportation Safety Board, FAA FSDO, Pilatus Aircraft, Hartzell Propeller, Inc, P&W - NTSB case key (mKey): 101199 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN20LA159 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/101199/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=101199 - Page: https://openairdocs.org/ntsb/CEN20LA159 ## Probable cause The loss of engine power due to a mis-rigged beta control cable (propeller reversing cable), which resulted in a loss of thrust inflight. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Maintenance: repair](https://openairdocs.org/ntsb-findings/02062015): Personnel issues › Task performance · Maintenance personnel; cases with it: [Pilatus PC-12/47, 1 case](https://openairdocs.org/ntsb-findings/02062015/cases.md?model=7090552), [All aircraft, 99 cases](https://openairdocs.org/ntsb-findings/02062015/cases.md) - [Personnel issues](https://openairdocs.org/ntsb-findings/02040000): Personnel issues › Action/decision · Pilot; cases with it: [Pilatus PC-12/47, 1 case](https://openairdocs.org/ntsb-findings/02040000/cases.md?model=7090552), [All aircraft, 56 cases](https://openairdocs.org/ntsb-findings/02040000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-climb to cruise: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Pilatus PC-12/47, 1 case](https://openairdocs.org/ntsb-events/342/sequence.md?model=7090552), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Pilatus PC-12/47, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=7090552), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis Shortly after takeoff the pilot reported to the air traffic controller that he was losing engine power. The pilot then said he was going to divert to a nearby airport and accepted headings to the airport. The pilot then reported the loss of engine power had stabilized, so he wanted to return to his departure airfield. A few moments later the pilot reported that he was losing engine power again and he needed to go back to his diversion airport. The controller reported that another airport was at the pilot’s 11 o’clock position and about 3 miles. The pilot elected to divert to that airport. The airplane was at 4,500 ft and too close to the airport, so the pilot flew a 360° turn to set up for a left base. During the turn outbound, the engine lost all power, and the pilot was not able to reach the runway. The airplane impacted a field, short of the airport. The airplane’s wings separated in the accident and a small postcrash fire developed. A review of the airplane’s maintenance records revealed maintenance was performed on the day of the accident flight to correct reported difficulty moving the Power Control Lever (PCL) into reverse position. The control cables were inspected from the pilot’s control quadrant to the engine, engine controls, and propeller governor. A static rigging check of the PCL was performed with no anomalies noted. Severe binding was observed on the beta control cable (propeller reversing cable). The cable assembly was removed from the engine, cleaned, reinstalled, and rigged in accordance with manufacturer guidance. During a post-accident examination of the engine and propeller assembly, the beta control cable was found mis-rigged and the propeller blades were found in the feathered position. The beta valve plunger was extended beyond the chamfer face of the propeller governor, consistent with a position that would shut off oil flow from the governor oil pump to the constant speed unit (CSU). A wire could be inserted through both the forward and aft beta control cable clevis inspection holes that function as check points for proper thread engagement. The forward beta control cable clevis adjustment nut was rotated full aft. The swaging ball end on the forward end of the beta control cable was not properly secured between the clevis rod end and the push-pull control terminal and was free to rotate within the assembly. Before takeoff, the beta valve was in an operational position that allowed oil flow to the CSU, resulting in normal propeller control. Vibration due to engine operation and beta valve return spring force most likely caused the improperly secured swaging ball to rotate (i.e. “unthread”) forward on the beta control cable. The resulting lengthening of the reversing cable assembly allowed the beta valve to stroke forward and shut off oil flow to the propeller CSU. Without propeller servo oil flow to maintain propeller control, the propeller faded to the high pitch/feather position due to normal leakage in the transferbearing. The reported loss of power is consistent with a loss of thrust due to the beta control cable being mis-rigged during the most recent maintenance work. ## Factual narrative On April 23, 2020, about 1600 central daylight time, a Pilatus PC-12 airplane, N477SS, was substantially damaged when it was involved in an accident near Mesquite, Texas. The pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 positioning flight. Shortly after takeoff, the pilot reported to the air traffic controller that he was losing engine power. The pilot decided to divert to Rockwall Municipal Airport, and then accepted vectors to the airport. The pilot then reported the loss of engine power had stabilized, so he wanted to return to DFW (Dallas-Fort Worth International Airport). A few moments later the pilot reported that he was losing engine power again and he needed to go back to Rockwall. The controller reported that the Mesquite Airport (HQZ) was at the pilot’s 11 o’clock position and about 3 miles. The pilot then elected to divert to HQZ. The pilot reported that the airplane was at 4,500 ft and too close to the airport, so to lose altitude he planned a 360° turn to set up for a left base at HQZ. During the turn outbound, the engine lost power and the pilot was not able to reach the runway. The airplane impacted terrain in a muddy field, short of the airport. The airplane’s wings separated in the accident and a small post-crash fire ensued. A review of the airplane’s maintenance records revealed maintenance was performed on the day of the accident flight to correct reported difficulty moving the Power Control Lever (PCL) into reverse position. The control cables were inspected from the pilot’s control quadrant to the engine, engine controls, and propeller governor. A static rigging check of the PCL was performed with no anomalies noted. Severe binding was observed on the beta control cable (propeller reversing cable). The cable assembly was removed from the engine, cleaned, reinstalled, and rigged in accordance with the Pilatus Aircraft Maintenance Manual (AMM) and Pratt & Whitney Engine Maintenance Manual (EMM). In a post-accident interview, the pilot reported that several days before the accident, on previous flights, the PCL was difficult to move from the idle detent into reverse (beta mode). He brought the issue up to the mechanics and other pilots, who reported the discrepancy. The maintenance records reflected that there were no issues with the PCL cable, the binding was caused by binding inbeta control cable assembly. The pilot stated that the accident flight was the first flight since maintenance work on the PCL, and that before departure, he cycled the propeller 3-4 times during taxi and the PCL operated “smoothly”. The engine and propeller were separated from the airframe and shipped to a Pratt & Whitney Canada facility in Bridgeport, West Virginia, for a detailed examination. A 1st stage compressor blade had impact damage on the leading edge and four blades had minor leading-edge damage. A borescope was used to inspect the centrifugal impeller and a small amount dirt/debrisaccumulation was visible, but the impeller vanes were all in good condition and unremarkable. The power turbine (PT) module was separated from the engine. The trailing edge of all compressor turbine blades were in good condition. The combustion liner was intact and there was no evidence of burn through or fuel nozzle streaking. The leading edge of the 1st stage PT blades and trailing edge of the 2nd stage PT blades visible through the exhaust were unremarkable. The beta control cable was found mis-rigged and the propeller blades were found in the feathered position. The beta valve plunger was extended beyond the chamfer face of the propeller governor, consistent with a position that would shut off oil flow from the governor oil pump to the constant speed unit (CSU). A wire could be inserted through both the forward and aft beta control cable clevis inspection holes that function as check points for proper thread engagement. The forward beta control cable clevis adjustment nut was rotated full aft. The swaging ball end on the forward end of the beta control cable was not properly secured between the clevis rod end and the push-pull control terminal and was free to rotate within the assembly. ## Aircraft - Registration: [N477SS](https://openairdocs.org/deregistered/N477SS-2021-10-02), registration cancelled 2021-10-02, S/N 813, built 2007 (OpenAirDocs) - Reported make and model: Pilatus PC12 (47) - Registry model: [Pilatus PC-12/47](https://openairdocs.org/model/pilatus-pc-12-47) (registry code 7090552) (OpenAirDocs) - Registry engine: [Pratt & Whitney Canada PT6A-67B](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-67b) (registry code 52158, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 813 - Year built: 2007 - Airframe hours: 7018.7 - Engines: Pratt & Whitney Canada PT6A-67B 1200 horsepower turbo prop - Damage: Substantial damage - Fire: On-Ground - Flight: Positioning, Part 91 - Operator: Boutique Air - Registered owner: Tvpx Aircraft Solutions Inc Trustee - Airworthiness certificate: Standard, Normal - Last inspection: AAIP, March 21, 2020 - Departed: DFW, Dallas, TX - Destination: MSL, Muscle Shoals, AL - Flight plan: IFR - Airport: HQZ, Mesquite Metro, runway 18, 6,000 × 100 ft, concrete - Equipment: Electronic multifunction display, Electronic primary flight display, Stall warning system, ADS-B, Angle of attack indicator, Auto-pilot, Electronic flight bag or handheld device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 55; injuries: serious; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review January 8, 2020; seat: left; restraint: 4-point; flight hours: 2,283 total, 1,137 in this make and model, 2,081 as pilot in command, 87 in the last 90 days, 59 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 20° at 4 knots, gusting 12 - Visibility: 10 statute miles - Temperature: 81 °F, dew point 52 °F - Altimeter: 29.76 inHg - Observed at: KHQZ ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20200423012929A](https://openairdocs.org/incident/20200423012929A), Apr 23, 2020: Pilatus Aircraft Ltd PC-12/47, Mesquite, TX, Substantial damage. On 2020-04-23 at approx 1534 local time a Pilatus PC12-47 operated by ^boutique air llcv part 135 (2B5A), impacted terrain after engine failure. The aircraft… ## Docket (8 files) The files NTSB released with the investigation on April 27, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=101199. 8.6 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12751685&FileExtension=pdf&FileName=NTSB%206120%20Form_Redacted-Rel.pdf - Pilot statement (item 2, PDF, 1 page, 82 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12751281&FileExtension=pdf&FileName=Miguel%20Acosta%20statement-Rel.pdf - POH excerpts (item 3, PDF, 5 pages, 831 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12751291&FileExtension=pdf&FileName=POH-Rel.pdf - Statement of party representatives to NTSB investigation (item 4, PDF, 1 page, 60 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12758806&FileExtension=pdf&FileName=CEN20LA159%20Hartzell%20Party%20Form_Redacted-Rel.pdf - Engine record (excerpt) (item 5, PDF, 1 page, 58 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12760175&FileExtension=pdf&FileName=Engine%20log%20excerpt_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 6, PDF, 1 page, 447 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12760271&FileExtension=pdf&FileName=Wreckage%20Release_Redacted-Rel.pdf - Evidence management (item 7, PDF, 2 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12782234&FileExtension=pdf&FileName=data%20cards%20Evidence%20Management_Redacted-Rel.pdf - Powerplants group chairman's factual report (item 8, PDF, 17 pages, 3.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12817253&FileExtension=pdf&FileName=CEN20LA159-%20Powerplant%20Group%20Chairman%27s%20Factual%20Report%20(DOCKET)-Rel.pdf 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. --- 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.