# NTSB ANC11CA056: Hughes 500D, Ambler, AK, June 27, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Data collection · Final report - Date: June 27, 2011, 09:25 local (17:25 UTC) - Place: Ambler, AK - Coordinates: 67.099998, -157.850006 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=67.1000&lon=-157.8500&mi=10 - Phase of flight: [Standing](https://openairdocs.org/ntsb-phases/150) (OpenAirDocs' grouping) - Defining event: [Standing-engine(s) operating: Loss of control on ground](https://openairdocs.org/ntsb-events/230) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report October 4, 2011 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: Federal Aviation Administration (Operations) - NTSB case key (mKey): 80946 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC11CA056 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/80946/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=80946 - Page: https://openairdocs.org/ntsb/ANC11CA056 ## Probable cause The pilot's misalignment of the helicopter on the landing structure. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Runway/land/takeoff/taxi surface](https://openairdocs.org/ntsb-findings/03023000): Environmental issues › Physical environment · Contributed to outcome; cases with it: [All aircraft, 253 cases](https://openairdocs.org/ntsb-findings/03023000/cases.md) - [Personnel issues](https://openairdocs.org/ntsb-findings/02060000): Personnel issues › Task performance · Pilot (probable cause); cases with it: [All aircraft, 137 cases](https://openairdocs.org/ntsb-findings/02060000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Standing-engine(s) operating: Loss of control on ground](https://openairdocs.org/ntsb-events/230) (defining event); cases with it: [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) - [Standing-engine(s) operating: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The helicopter pilot landed a high skid, turbine-powered helicopter at a remote drilling site, and the three passengers disembarked. The remote landing site was constructed of 6-inch by 6-inch wooden beams, which required that the pilot land perpendicular to and on the beams with the helicopter's skids. The pilot reported that after landing he retarded the engine throttle to flight idle to begin the mandatory 2 minute engine cool down procedure. He then got out of the helicopter to check the placement of the helicopter's skids on the beams, and it subsequently tipped backwards, with the tail rotor striking terrain. A postaccident inspection revealed that while landing, the pilot inadvertently placed the helicopter's skids behind the aft wooden beam, and the helicopter tipped backwards once the pilot exited the helicopter. The pilot said there were no preimpact mechanical problems with the helicopter. The helicopter sustained substantial damage to the tail boom, tail rotor drive system, and tail rotor gearbox. ## Factual narrative The helicopter pilot landed a high skid, turbine-powered helicopter at a remote drilling site, and the three passengers disembarked. The remote landing site was constructed of 6-inch by 6-inch wooden beams, which required that the pilot land perpendicular to and on the beams with the helicopter's skids. The pilot reported that after landing he retarded the engine throttle to flight idle to begin the mandatory 2 minute engine cool down procedure. He then got out of the helicopter to check the placement of the helicopter's skids on the beams, and it subsequently tipped backwards, with the tail rotor striking terrain. In his written statement to the NTSB, the pilot wrote, in part: "While waiting, I stepped out of the helicopter to look under the helicopter to verify that my bear paws were both securely placed on the supporting timber. Within a moment of stepping out, I noticed movement and watched as the helicopter tipped backwards until it came to rest on the tail rotor and stinger." A postaccident inspection revealed that while landing, the pilot inadvertently placed the helicopter's skids behind the aft wooden beam, and the helicopter tipped backwards once the pilot exited the helicopter. The pilot said there were no preimpact mechanical problems with the helicopter. The helicopter sustained substantial damage to the tail boom, tail rotor drive system, and tail rotor gearbox. ## Aircraft - Registration: C-GLHQ (not matched to a registry record) - Reported make and model: HUGHES 500D - Category: Helicopter - Serial number: 200662D - Airframe hours: 18753 - Engines: Allison 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Part 135 - Operator: Prism Helicopters - Registered owner: Prism Helicopters - Airworthiness certificate: Standard, Normal - Departed: Ambler, AK - Destination: Ambler, AK - Flight plan: Unknown ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 36; injuries: none; commercial; instrument ratings: helicopter; medical: class 2, with waivers/limitations; last flight review May 2, 2011; seat: left; flight hours: 4,975 total, 87 in this make and model, 4,857 as pilot in command, 88 in the last 90 days, 78 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Visibility: 30 statute miles - Lowest ceiling: none ## Docket (2 files) The files NTSB released with the investigation on August 5, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=80946. 497 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 431 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40352012&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Helicopter Operator Information (item 2, .PDF, 66 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40352090&FileExtension=.PDF&FileName=Helicopter%20Operator%20Information-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.