# NTSB WPR14LA341: Mcdonnell Douglas Helicopter 500N, N18GH, Idaho Falls, ID, August 12, 2014 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 11, 2014, 20:00 local (Aug 12, 2014, 02:00 UTC) - Place: Idaho Falls, ID - Coordinates: 43.461666, -112.014999 - Nearby events: https://openairdocs.org/map.md?lat=43.4617&lon=-112.0150&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Defining event: [Takeoff: Loss of tail rotor effectiveness](https://openairdocs.org/ntsb-events/242) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed, report July 13, 2015 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration, MD Helicopter, Boeing Helicopters - NTSB case key (mKey): 89853 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR14LA341 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/89853/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=89853 - Page: https://openairdocs.org/ntsb/WPR14LA341 ## Probable cause The pilot’s loss of helicopter control for reasons that could not be determined because postaccident examination of the helicopter did not reveal any mechanical malfunctions or failures that would have precluded normal operation. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Mcdonnell Douglas Helicopter 500N, 1 case](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=3027374), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot; cases with it: [Mcdonnell Douglas Helicopter 500N, 1 case](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=3027374), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Performance/control parameters](https://openairdocs.org/ntsb-findings/01062000): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Mcdonnell Douglas Helicopter 500N, 1 case](https://openairdocs.org/ntsb-findings/01062000/cases.md?model=3027374), [All aircraft, 1,269 cases](https://openairdocs.org/ntsb-findings/01062000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Takeoff: Loss of tail rotor effectiveness](https://openairdocs.org/ntsb-events/242) (defining event); cases with it: [Mcdonnell Douglas Helicopter 500N, 2 cases](https://openairdocs.org/ntsb-events/242/sequence.md?model=3027374), [All aircraft, 100 cases](https://openairdocs.org/ntsb-events/242/sequence.md) - [Takeoff: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [Mcdonnell Douglas Helicopter 500N, 2 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=3027374), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Takeoff: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Mcdonnell Douglas Helicopter 500N, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=3027374), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot reported that he initiated a vertical climb in the helicopter to clear trees and a residential structure. When the helicopter was about 90 ft above ground level, it banked left and immediately began to rotate. The pilot made control inputs but was unable to regain control of the helicopter, so he initiated an autorotation. Subsequently, the helicopter impacted the ground and rolled over onto its right side. Postaccident examination of the airframe and flight control system revealed no evidence of any preexisting mechanical malfunction that would have precluded normal operation. Postaccident weight and balance and performance calculations revealed that, at the time of the accident, the helicopter was within weight and balance and performance limitations for an out-of-ground-effect hover. ## Factual narrative On August 11, 2014, about 2000 mountain daylight time, a McDonnell Douglas Helicopter 500N, N18GH, was substantially damaged when it impacted terrain during takeoff from a private residence near Idaho Falls, Idaho. The helicopter was registered to Kabrit LLC, Salt Lake City, Utah, and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. The private pilot and his two passengers were not injured. Visual meteorological conditions prevailed and no flight plan was filed for the local flight, which was originating at the time of the accident.In a written statement to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot reported that during takeoff from a private residence, he initiated a vertical climb in order to clear trees and a residential structure. As the helicopter was about 90 feet above ground level (agl), the helicopter banked to the left and immediately began to rotate. The pilot stated that despite his control inputs, he was unable to regain control of the helicopter and initiated an autorotation "to get the torque out of the rotor head." Subsequently, the helicopter impacted the ground and rolled over onto its right side, which resulted in damage to the main rotor blades, fuselage, and tailboom. The engine was shut down by the pilot after impact. Examination of the helicopter by representatives from Boeing Helicopters and MD Helicopters, under the supervision of the NTSB IIC was conducted on September 25, 2014, at the facilities of SP Aircraft, Boise, Idaho. The airframe exhibited damage to the sheet metal skin and the composite fuselage components. The front canopy frame and windscreen sections were broken and separated from the airframe. The upper pylon and NOTAR inlet was damaged with the composite structures crushed and fractured. Cyclic and collective control continuity was verified from the control sticks to the upper flight controls, which included the collective, lateral and longitudinal links, and collective/cyclic mixers, scissors assembly, pitch change links, rotating and stationary swashplates, which were in place, functional and sustained varying degrees of impact damage. The anti-torque flight control linkage was continuous from the left pedal set to the two-piece cable assembly and to the NOTAR fan pitch control mechanism. Continuity continued from the cable assembly separation point on the tailboom to the rotating cone assembly. The rotating cone and bearings appeared functional. The NOTAR system experienced extensive damage during the accident sequence which included separation of the tailboom, damage to the pedal sets and deformation of the fan shroud assembly. There was no visible damage to the fan transmission, and the gearbox operation functioned when rotated by hand. The fan driveshaft from the main transmission to the fan gearbox and from the fan gearbox to the fan assembly was undamaged. The fan assembly was in place; however the fan bladeswere in contact with the deformed shroud and sustained substantial foreign object damage to the blades. The main rotor system sustained substantial impact damage. The hub assembly components (upper and lower shoe, pitch change housings, feather bearings, strap assemblies, dampers, pitch change links, droop stops, striker plates, etc.) exhibited varying degrees of visible damage consistent with sudden stoppage from impact with terrain. All main rotor blades sustained substantial damage. Severity of damage varied but included blade fractures, gouges, bent spars, chord-wise wrinkling, leading and trailing edge bending, separation and tip cap damage. There were indications that several blades made contact with the fuselage, cockpit and tailboom. Damage to the rotor blades was consistent with sudden stoppage and ground impact. The main transmission showed no exterior impact damage. The upper and lower transmission chip detectors were removed for inspection and were clean of debris. The transmission support structure was undamaged, with both the static mast and main transmission securely attached. The main transmission rotated when the engine to transmission driveshaft was actuated. The transmission anti-torque output pinion also rotated. The main rotor driveshaft had fractured approximately three inches above the splined fitting into the transmission, which precluded the transmission from rotating when the main rotor blades were moved. The fracture surface was smeared but appeared that it had fractured in overload. The engine to transmission shaft was undamaged. The over-running clutch appeared functional. Weight and balance calculations were performed by the manufacturer, with the helicopter found to be within limits. In addition, performance calculations were calculated for the weight of the helicopter and weather conditions at the time of the accident and it was verified that the helicopter was within the published operational limits for an out of ground effect hover. ## Aircraft - Registration: [N18GH](https://openairdocs.org/aircraft/N18GH), registered now, S/N LN014 (OpenAirDocs) - Reported make and model: MCDONNELL DOUGLAS HELICOPTER 500N (N) - Registry model: [Mcdonnell Douglas Helicopter 500N](https://openairdocs.org/model/mcdonnell-douglas-helicopter-500n) (registry code 3027374) (OpenAirDocs) - Registry engine: [Rolls-Royce 250-C20R](https://openairdocs.org/engine/rolls-royce-250-c20r) (registry code 54183, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: LN014 - Airframe hours: 1902.8 - Engines: Rolls Royce 250-C20R 450 horsepower turbo shaft - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: David Hansen - Registered owner: Kabrit LLC - Airworthiness certificate: Standard, Normal - Departed: Idaho Falls, ID - Destination: Idaho Falls, ID ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 43; injuries: none; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, without waivers/limitations; last flight review August 15, 2013; seat: left; restraint: 4-point; flight hours: 1,623 total, 544 in this make and model, 1,623 as pilot in command, 60 in the last 90 days, 24 in the last 30 days, 0.5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 80° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 43 °F - Altimeter: 30.14 inHg - Observed at: KIDA, 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 20140811015319A](https://openairdocs.org/incident/20140811015319A), Aug 11, 2014: Mcdonnell Douglas Helicopter 500N, Idaho Falls, ID, Substantial damage. Pilot reported that during takeoff from a private residence, the helicopter was about 40 to 50 feet above ground level (AGL) when he lost tail rotor control.… ## Docket (6 files) The files NTSB released with the investigation on June 11, 2015, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=89853. 1.7 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 938 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40427710&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Boeing Helicopter and MD Helicopter Field Notes (item 2, .PDF, 198 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40427712&FileExtension=.PDF&FileName=Boeing%20Helicopter%20and%20MD%20Helicopter%20Field%20Notes-Redacted.PDF - Aircraft Performance Worksheet (item 3, .PDF, 44 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40427713&FileExtension=.PDF&FileName=Aircraft%20Performance%20Worksheet-Master.PDF - Statement of Party Representatives to NTSB Investigation - Boeing Helicopter (item 4, .PDF, 189 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40427715&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation%20-%20Boeing%20Helicopter-Redacted.PDF - Statement of Party Representatives to NTSB Investigation - MD Helicopter (item 5, .PDF, 229 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40427716&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation%20-%20MD%20Helicopter-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 6, .PDF, 86 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40427717&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.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.