# NTSB ERA15LA343: Dehavilland DHC-6, N181CS, Louisburg, NC, September 6, 2015 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: September 6, 2015, 15:40 local (19:40 UTC) - Place: Louisburg, NC - Coordinates: 36.08472, -78.371948 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=36.0847&lon=-78.3719&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Defining event: [Approach-VFR pattern final: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: Serious injuries - Injuries: 1 serious, 1 minor, 1 uninjured - Status: Completed, report June 1, 2016 - Report: Approved by Office Director - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO - NTSB case key (mKey): 91932 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA15LA343 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/91932/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=91932 - Page: https://openairdocs.org/ntsb/ERA15LA343 ## Probable cause The propeller’s movement to the beta position during landing for reasons that could not be determined during postaccident examination and testing, which resulted in an attempted go-around and subsequent loss of airplane control. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Propeller system: propeller feather/reversing](https://openairdocs.org/ntsb-findings/01046123): Aircraft › Aircraft propeller/rotor · Malfunction (probable cause); cases with it: [Dehavilland DHC-6-200, 1 case](https://openairdocs.org/ntsb-findings/01046123/cases.md?model=2802620), [All aircraft, 26 cases](https://openairdocs.org/ntsb-findings/01046123/cases.md) - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Dehavilland DHC-6-200, 1 case](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=2802620), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) - [Performance/control parameters](https://openairdocs.org/ntsb-findings/01062000): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [Dehavilland DHC-6-200, 1 case](https://openairdocs.org/ntsb-findings/01062000/cases.md?model=2802620), [All aircraft, 1,269 cases](https://openairdocs.org/ntsb-findings/01062000/cases.md) - [Object/animal/substance: tree(s)](https://openairdocs.org/ntsb-findings/03022020): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Dehavilland DHC-6-200, 1 case](https://openairdocs.org/ntsb-findings/03022020/cases.md?model=2802620), [All aircraft, 933 cases](https://openairdocs.org/ntsb-findings/03022020/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Approach-VFR pattern final: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Dehavilland DHC-6-200, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=2802620), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Approach-VFR go-around: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [Dehavilland DHC-6-200, 1 case](https://openairdocs.org/ntsb-events/240/sequence.md?model=2802620), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Approach-VFR go-around: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Dehavilland DHC-6-200, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=2802620), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The airline transport pilot was conducting a cross-country aerial observation flight in the multiengine airplane. The pilot reported that the airplane was on the final leg of the traffic pattern when he reduced the power levers for landing and noticed that the right engine sounded like the propeller was moving toward the beta position. The pilot increased the engine power, and the sound stopped. As the airplane got closer to the runway, he decreased the engine power, and the sound returned. In addition, the airplane began to yaw right. The pilot applied left aileron and rudder inputs to remain above the runway centerline without success. While over the runway, the pilot reduced the engine power to idle, and the airplane continued to yaw right. The pilot applied full power in an attempt to perform a go-around; however, the airplane yawed about 30 degrees off the runway centerline, touched down in the grass, and impacted trees before coming to rest. The right wing, right engine, and right propeller assembly were impact-separated. The right engine propeller came to rest about 50 ft forward of the main wreckage, and it was found in the feathered position. A review of maintenance records revealed that the right propeller had been overhauled and reinstalled on the airplane 2 days before the accident and had operated 9 hours since that time. Subsequent testing of the right propeller governor revealed that it functioned without anomaly; however, the speed settings were improperly configured. Further, the testing revealed that the beta valve travel from the neutral position was out of tolerance. Although this could have let oil pressure port to one side of the spool or the other and, thus, changed the propeller blade angle, it could not be determined whether this occurred during the accident landing. Impact damage precluded examination of the right propeller governor control linkage; therefore, it could not be determined if it was inadequately installed or rigged, which could have resulted in the propeller moving into the beta position. The investigation could not determine why the right propeller moved toward the beta position as engine power was reduced, as reported the pilot. ## Factual narrative On September 6, 2015, about 1540 eastern daylight time, a DeHavilland DHC-6-200, N181CS, operated by Rampart Aviation, LLC, sustained substantial damage during landing at North Raleigh Airport (00NC), Louisburg, North Carolina. The certificated airline transport pilot flying received minor injuries, the airline transport pilot not flying was seriously injured, and the passenger was not injured. Visual meteorological conditions prevailed and no flight plan was filed for the aerial observation flight that departed Washington County Airport (AFJ), Washington, Pennsylvania around 0915. The flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91.According to the pilot, the airplane was on the final leg of the traffic pattern when he reduced the power levers for landing, and noticed that the right engine sounded like "the [propeller] was heading towards beta." The pilot increased the engine power and the sound "went away." Closer to the runway, he decreased engine power and the noise returned, the airplane yawed to the right, and he applied left aileron and rudder inputs in order to remain aligned with the runway centerline. While over the runway, the pilot reduced the engine power to idle and the airplane "pushed hard to the right." Then, the pilot applied full power in an attempt to perform a go-around maneuver; however, the airplane yawed about 30 degrees off the runway centerline, touched down in the grass, and impacted trees prior to coming to rest. The airplane came to rest about 80 feet from the right side of the runway. The right wing, right engine, and right propeller assembly were impact separated. In addition, the right side of the cockpit exhibited crush damage. The right engine propeller came to rest approximately 50 feet forward of the main wreckage and was observed in the feather position. Examination of the bolt holes where the bolts secured the propeller to the right engine exhibited elongation and smearing. According to Federal Aviation Administration records, the airplane was manufactured in 1968. It was equipped with two Pratt and Whitney Canada PT6A-27, 620 horsepower engines that utilized 4-bladed McCauley controllable pitch propeller assemblies, which were installed per Supplemental Type Certificate (STC) SA1385GL. Postaccident examination of maintenance records indicated that the most recent continuous airworthiness inspection was performed on September 3, 2015. In addition, an overhauled propeller was installed on the right engine and a test flight was performed on September 4, 2015, which was 8.7 flight hours prior to the accident. The maintenance logbook entry for the right propeller stated: "Reinstalled propeller [in accordance with] McCauley Owner Operators Manual…[torqued] nuts to 57 ft lbs with [torque] wrench. No defects noted." At the time of the accident the airplane had accumulated 6,915.4 total hours. According to the McCauley Propeller Owner/Operator Manual, the propeller wasdesigned to operate in two modes of operation, the beta mode and the governor mode. The beta mode could be selected "for ground reversing or taxi operation by means of the aircraft engine mechanical linkage. The linkage repositions the propeller reversing lever and beta valve to provide access for high pressure oil to reach the propeller piston and move the blades toward reverse pitch." In addition, "Propellers are a single acting unit in which hydraulic pressure opposes the forces of springs and counterweights to obtain the correct pitch for engine load. Hydraulic pressure urges blades toward low pitch (increasing RPM), while springs and counterweights urge blades toward high pitch (decreasing RPM)." According to STC SA1385GL, the McCauley propeller installation on the accident airplane required the propeller retaining nuts to be torqued to 68 to 72 foot pounds. The right propeller governor was sent to the manufacturer for examination and testing. During the examination, the governor functioned without anomaly. Nicks and "chatter marks" were observed around the mounting hole of the base closest to the drain port. The speed setting lever was bent outward, the max stop screw had been adjusted out an "excess number" of threads, and the control lever return spring was not engaged to the speed setting lever. The maximum speed was set about 170 rpm below the factory specification, and the pneumatic control valve settings for overspeed and underspeed were reset to compensate for the incorrect maximum speed setting. In addition, the beta valve travel from null, or the neutral position, was out of tolerance; however, during testing, the governor operated without anomaly. [Additional information about the governor examination can be found in the public docket for this case.] The right propeller governor control rigging was unable to be examined and tested due to the damage to the right wing that incurred during the accident sequence. However, according to manufacturer installation guidelines "make sure of proper rigging of engine controls. Refer to aircraft maintenance manual or STC maintenance manual supplement." In addition, it stated that "feather, reverse, and low blade angles are set during assembly or overhaul. These angles are NOT adjustable in the field." Also, the propeller manufacturer preflight checklist indicated, "the control system (governor) should be checked to determine whether the system is operating properly and is not leaking." ## Aircraft - Registration: [N181CS](https://openairdocs.org/deregistered/N181CS-2017-03-31), registration cancelled 2017-03-31, S/N 181, built 1968 (OpenAirDocs) - Reported make and model: DEHAVILLAND DHC-6 (200) - Registry model: [Dehavilland DHC-6-200](https://openairdocs.org/model/dehavilland-dhc-6-200) (registry code 2802620) (OpenAirDocs) - Registry engine: [Pratt & Whitney PT6A-27 series](https://openairdocs.org/engine/pratt-whitney-pt6a-27-series) (registry code 52141, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 181 - Year built: 1968 - Airframe hours: 26915.4 - Engines: Pratt & Whitney Canada PT6-27 620 horsepower turbo prop; Pratt & Whitney Canada PT6-27 620 horsepower turbo prop - Damage: Substantial damage - Flight: Aerial observation, Part 91 - Operator: Rampart Aviation - Registered owner: Fhc Group LLC - Airworthiness certificate: Standard, Normal - Last inspection: Continuous airworthiness, September 3, 2015, 9 hours before - Departed: AFJ, WASHINGTON, PA - Destination: 00NC, Louisburg, NC - Airport: 00NC, North Raleigh, runway 05, 2,650 × 36 ft, asphalt - Equipment: Stall warning system, Electronic flight bag or handheld device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 37; injuries: serious; airline transport, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review June 22, 2015; seat: left; restraint: 4-point; flight hours: 7,337 total, 1,058 in this make and model, 6,415 as pilot in command, 43 in the last 90 days, 23 in the last 30 days - Co-pilot; age 44; injuries: serious; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane, helicopter; medical: class 2, with waivers/limitations; last flight review June 30, 2015; seat: right; restraint: 4-point; flight hours: 3,187 total, 1,180 in this make and model, 2,980 as pilot in command, 132 in the last 90 days, 10 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 30° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 79 °F, dew point 70 °F - Altimeter: 30.15 inHg - Observed at: LHZ, 4 nm away ## 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 20150906023729A](https://openairdocs.org/incident/20150906023729A), Sep 6, 2015: Dehavilland DHC-6-200, Louisberg, NC, Destroyed. During landing, N181CS, a Dehavilland twin otter, DHC-6-200, s/n 181, departed the runway surface at approximately 30 degrees to the right of the runway… ## Docket (10 files) The files NTSB released with the investigation on March 24, 2016, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=91932. 4.8 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40438089&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Pilot Statement (item 2, .PDF, 341 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40438090&FileExtension=.PDF&FileName=Pilot%20Statement-Master.PDF - FAA Inspector Report (item 3, .PDF, 19 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40438091&FileExtension=.PDF&FileName=FAA%20Inspector%20Report-Master.PDF - Maintenance Records - Excerpts on Right Propeller (item 4, .PDF, 837 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40438092&FileExtension=.PDF&FileName=Maintenance%20Records%20-%20Excerpts%20on%20Right%20Propeller-Master.PDF - Post Maintenance Flight Logs (item 5, .PDF, 704 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40438093&FileExtension=.PDF&FileName=Post%20Maintenance%20Flight%20Logs-Master.PDF - Right Propeller Governor Examination Report - Woodward (item 6, .PDF, 24 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40438094&FileExtension=.PDF&FileName=Right%20Propeller%20Governor%20Examination%20Report%20-%20Woodward-Master.PDF - McCauley Propeller Owner/Operator's Manual Excerpts (item 7, .PDF, 151 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40438095&FileExtension=.PDF&FileName=McCauley%20Propeller%20Owner%2FOperator%27s%20Manual%20Excerpts-Master.PDF - Weather Reports and Records (item 8, .PDF, 132 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40438096&FileExtension=.PDF&FileName=Weather%20Reports%20and%20Records-Master.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 9, .PDF, 224 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40438097&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Master.PDF - Photo Array (item 10, .PDF, 662 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40438098&FileExtension=.PDF&FileName=Photo%20Array-Master.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.