# NTSB WPR09LA028: Hiller UH-12E, N61436, Powder River, WY, October 30, 2008 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: October 30, 2008, 08:40 local (14:40 UTC) - Place: Powder River, WY - Coordinates: 43.035556, -107.081108 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=43.0356&lon=-107.0811&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) - Highest injury: Minor injuries - Injuries: 1 minor, 1 uninjured - Status: Completed, report September 30, 2009 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 69377 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR09LA028 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/69377/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=69377 - Page: https://openairdocs.org/ntsb/WPR09LA028 ## Probable cause A flight control system malfunction while the helicopter was maneuvering at low altitude due to the failure/separation of the rotor blade control tube. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Rotorcraft flight control: main rotor control](https://openairdocs.org/ntsb-findings/01046710): Aircraft › Aircraft propeller/rotor · Failure (probable cause); cases with it: [Hiller UH-12E, 1 case](https://openairdocs.org/ntsb-findings/01046710/cases.md?model=4360122), [All aircraft, 28 cases](https://openairdocs.org/ntsb-findings/01046710/cases.md) - [Terrain: mountainous/hilly terrain](https://openairdocs.org/ntsb-findings/03021010): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Hiller UH-12E, 2 cases](https://openairdocs.org/ntsb-findings/03021010/cases.md?model=4360122), [All aircraft, 329 cases](https://openairdocs.org/ntsb-findings/03021010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-low-alt flying: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [Hiller UH-12E, 3 cases](https://openairdocs.org/ntsb-events/333/sequence.md?model=4360122), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md) - [Landing-flare/touchdown: Hard landing](https://openairdocs.org/ntsb-events/092); cases with it: [Hiller UH-12E, 4 cases](https://openairdocs.org/ntsb-events/092/sequence.md?model=4360122), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) ## Analysis While maneuvering about 50 feet above ground level during an aerial observation flight, one blade associated with the control rotor assembly separated from the helicopter, and a violent vibration started. Unable to maintain control, the pilot made a forced landing on the underlying sloping terrain, and the helicopter rolled over. During the subsequent inspection of the rotor system, one of the two control rotor blade assemblies was found separated from the rotor head. A rotor blade control tube had cracked and broken off outboard of the two attachment bolts. The component had been operated 21 hours since receiving its last inspection. The reason for the cracking and separation of the control tube could not be determined. ## Factual narrative October 30, 2008, about 0840 mountain daylight time, a Hiller UH-12E, N61436, experienced a flight control system malfunction while maneuvering about 5 miles west-southwest of Powder River, Wyoming. Unable to maintain control of the helicopter, the pilot made a hard forced landing on the slope of a hillside. Upon touchdown, the helicopter rolled over and was substantially damaged. The commercial certificated pilot received a minor injury, and the passenger was not injured. The helicopter was owned and operated by Wyoming Air Corporation, Casper, Wyoming. Visual meteorological conditions prevailed at the time of the aerial observation (predator control) flight, and no flight plan was filed. The flight was performed under the provisions of 14 Code of Federal Regulations Part 91, and it originated from a refueling vehicle near Powder River, about 0830. The pilot reported to the National Transportation Safety Board investigator that the accident occurred while he was maneuvering about 50 feet above ground level and looking for coyotes. Suddenly, one blade associated with the control rotor assembly separated from the helicopter and a violent vibration started. The pilot reported that the vibration precluded him from being able to read the airspeed indicator, and he only had "minimal control" of the helicopter. During the subsequent examination of the helicopter, one of the two control rotor blade assemblies (Hiller part number 36209-3) was found separated from the rotor head. The rotor control blade assembly tube was observed cracked and broken off outboard of the two bolts attaching it to the cuff assembly. The helicopter had been operated about 21 hours since receiving its last annual inspection. ## Aircraft - Registration: [N61436](https://openairdocs.org/deregistered/N61436-2018-01-25), registration cancelled 2018-01-25, S/N 5017, built 1977 (OpenAirDocs) - Reported make and model: HILLER UH-12E - Registry model: [Hiller UH-12E](https://openairdocs.org/model/hiller-uh-12e) (registry code 4360122) (OpenAirDocs) - Registry engine: [Lycoming VO-540 series](https://openairdocs.org/engine/lycoming-vo-540-series) (registry code 41582, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 5017 - Airframe hours: 4115 - Engines: LYCOMING VO-540 SER 305 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial observation, Part 91 - Operator: Wyoming Air Corp - Registered owner: Wyoming Air Corp - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, September 20, 2008, 21 hours before - Departed: Powder River, WY - Destination: Powder River, WY ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 33; injuries: minor; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review August 23, 2007; seat: left; flight hours: 1,908 total, 448 in this make and model, 1,778 as pilot in command, 39 in the last 90 days, 33 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 200° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 61 °F ## 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 20081030851229A](https://openairdocs.org/incident/20081030851229A), Oct 30, 2008: Hiller UH12E, Power River, WY, Destroyed. (-23) Control rotor blade assy shaft broke at outer attach bolt hole. ## Docket (1 files) The files NTSB released with the investigation on August 10, 2009, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=69377. 750 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 750 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40304291&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-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.