# NTSB ANC08LA083: Bell UH-1B, N64RA, Iliamna, AK, June 30, 2008 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 29, 2008, 22:30 local (Jun 30, 2008, 06:30 UTC) - Place: Iliamna, AK - Coordinates: 61.270645, -149.789825 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.2706&lon=-149.7898&mi=10 - Phase of flight: [Emergency descent](https://openairdocs.org/ntsb-phases/600) (OpenAirDocs' grouping) - Defining event: [Autorotation: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report May 12, 2009 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: Federal Aviation Administration - NTSB case key (mKey): 68401 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC08LA083 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/68401/pdf - Page: https://openairdocs.org/ntsb/ANC08LA083 ## Probable cause The failure of company maintenance personnel to ensure the helicopter was properly maintained, resulting in a severe in-flight vibration due to collective bounce. Contributing to the accident was loose and worn bearings on the helicopter's stabilizer bar, swashplate, flight control tube assemblies, and the right and left hydraulic servos. ## 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 (probable cause); cases with it: [Richards Heavylift Helo UH-1B, 1 case](https://openairdocs.org/ntsb-findings/02062015/cases.md?model=118141G), [All aircraft, 99 cases](https://openairdocs.org/ntsb-findings/02062015/cases.md) - [Rotorcraft flight control](https://openairdocs.org/ntsb-findings/01046700): Aircraft › Aircraft propeller/rotor · Incorrect service/maintenance (probable cause); cases with it: [Richards Heavylift Helo UH-1B, 1 case](https://openairdocs.org/ntsb-findings/01046700/cases.md?model=118141G), [All aircraft, 9 cases](https://openairdocs.org/ntsb-findings/01046700/cases.md) - [Main rotor system](https://openairdocs.org/ntsb-findings/01046200): Aircraft › Aircraft propeller/rotor · Incorrect service/maintenance (probable cause); cases with it: [Richards Heavylift Helo UH-1B, 1 case](https://openairdocs.org/ntsb-findings/01046200/cases.md?model=118141G), [All aircraft, 25 cases](https://openairdocs.org/ntsb-findings/01046200/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Approach: Simulated/training event](https://openairdocs.org/ntsb-events/600); cases with it: [Richards Heavylift Helo UH-1B, 1 case](https://openairdocs.org/ntsb-events/600/sequence.md?model=118141G), [All aircraft, 173 cases](https://openairdocs.org/ntsb-events/600/sequence.md) - [Autorotation: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [Richards Heavylift Helo UH-1B, 1 case](https://openairdocs.org/ntsb-events/333/sequence.md?model=118141G), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md) - [Autorotation: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [Richards Heavylift Helo UH-1B, 1 case](https://openairdocs.org/ntsb-events/240/sequence.md?model=118141G), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Autorotation: Hard landing](https://openairdocs.org/ntsb-events/092); cases with it: [Richards Heavylift Helo UH-1B, 1 case](https://openairdocs.org/ntsb-events/092/sequence.md?model=118141G), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) ## Analysis The commercial pilot said that as the helicopter approached the destination airport during a Part 91 repositioning flight, he elected to make a practice autorotation to the runway. As he lowered the collective to enter the autorotation, the helicopter began to vibrate violently. He continued the autorotation to runway, and stated that during the landing flare the helicopter's tail boom contacted the runway, the helicopter rocked forward, and the landing gear skids struck the ground. The hard landing resulted in substantial damage to the fuselage, tail boom assembly, and main rotor transmission supports. A maintenance technician that did a postaccident inspection of the helicopter discovered loose and worn bearings on the helicopter's stabilizer bar, swashplate, flight control tube assemblies, and the right and left hydraulic servos. In a written report the maintenance technician reported that the mechanical discrepancies he discovered during his inspection were, in part: "noted as being the root cause of the vertical vibration..." ## Factual narrative On June 29, 2008, about 2230 Alaska daylight time, a restricted category Bell UH-1B helicopter, N64RA, sustained substantial damage during a hard landing at the Iliamna Airport, Iliamna, Alaska. The helicopter was being operated as a visual flight rules (VFR) positioning flight under the provisions of 14 Code of Federal Regulations Part 91, when the accident occurred. The commercial pilot, and the one pilot-rated passenger, were not injured. Visual meteorological conditions prevailed, and a VFR flight plan was filed. The flight originated from a remote site near Platinum, Alaska, about 2100. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on July 3, the pilot reported that the purpose of the flight was to reposition the helicopter to Iliamna, and provide the pilot-rated passenger with a familiarization flight in a Bell UH-1B helicopter. The pilot said that as the flight approached the Iliamna Airport, he instructed the passenger that he was going to demonstrate a practice autorotation to runway 07. The pilot reported that as he lowered the collective to enter the autorotation, the helicopter began to vibrate violently. He said that the vertical vibration, which he described as "collective bounce" was so severe that at one point he was unable to read the airspeed indicator and engine toque meter. The pilot said that he elected to continue the autorotation to runway 07. He said that during the landing flare the helicopter's tail boom contacted the runway, the helicopter rocked forward, and the landing gear skids struck the ground. The hard landing resulted in structural damage to the fuselage, tail boom assembly, and main rotor transmission supports. The Operator's Manual for the Bell UH-1B helicopter, states in part: "Collective bounce is a pilot induced vertical oscillation that may be encountered in any flight condition by a rapid buildup of vertical bounce at approximately three cycles per second. The severity of this oscillation is such that effective control of the aircraft may become difficult to maintain." According to the operator, a postaccident inspection of the helicopter was accomplished by a Bell Helicopter service center technician, which revealed loose and worn bearings on the helicopter's stabilizer bar, swashplate, flight control tube assemblies, and the right and left hydraulic servos. In a letter dated July 18, 2008, the maintenance technician reported that the mechanical discrepancies he discovered during his inspection were, in part: "noted as being the root cause of the vertical vibration..." A copy of the maintenance technician's letter is included in the public docket for this accident. ## Aircraft - Registration: [N64RA](https://openairdocs.org/deregistered/N64RA-2022-03-05), registration cancelled 2022-03-05, S/N 65-12854, built 1965 (OpenAirDocs) - Reported make and model: BELL UH-1B - Registry model: [Richards Heavylift Helo UH-1B](https://openairdocs.org/model/richards-heavylift-helo-uh-1b) (registry code 118141G) (OpenAirDocs) - Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs) - Category: Helicopter - Serial number: 65-12854 - Engines: LYCOMING T-53 SERIES 1150 horsepower - Damage: Substantial damage - Flight: Positioning, Part 91 - Operator: Pollux Avaition LTD - Registered owner: Pollux Aviation Ltd - Airworthiness certificate: Special, Restricted (Special) - Departed: PLATINUM, AK - Destination: ILI, ILIAMNA, AK - Flight plan: VFR - Airport: IlI, Iliamna, runway 07, 5,086 × 100 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 61; injuries: none; flight instructor, commercial; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane, helicopter; medical: class 2, with waivers/limitations; seat: right; flight hours: 30,000 total, 950 in this make and model, 29,500 as pilot in command, 180 in the last 90 days, 70 in the last 30 days, 6 in the last 24 hours - Other flight crew; age 30; injuries: none; commercial; medical: class 2, with waivers/limitations; last flight review June 22, 2008; seat: left; flight hours: 2,050 total, 3 in this make and model, 1,950 as pilot in command, 120 in the last 90 days, 20 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 110° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 52 °F, dew point 41 °F - Altimeter: 30.19 inHg - Observed at: ILI ## 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 20080629841569A](https://openairdocs.org/incident/20080629841569A), Jun 29, 2008: Bell UH1B, Iliamna, AK, Substantial damage. (-23) During a practice "autorotation" maneuver the collective was lowered to approximately 2/3 down when, the helicopter experienced a severe vertical 1:1… ## Other investigations on N64RA (1) 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. - [NTSB WPR19FA091](https://openairdocs.org/ntsb/WPR19FA091), Mar 8, 2019: Bell UH1B (N64RA), Forks, WA, destroyed, 1 fatal. Probable cause: A total loss of engine power due to the failure of the gas generator sealing disk as a result of the operator’s exceedance of the sealing disk life limits at too low an altitude for the pilot to… 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.