# NTSB WPR18LA004: Western International Avia UH 1H, N247PV, Arbuckle, CA, October 13, 2017 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: October 13, 2017, 10:15 local (17:15 UTC) - Place: Arbuckle, CA - Coordinates: 39.051944, -122.090553 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.0519&lon=-122.0906&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 96154 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR18LA004 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/96154/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=96154 - Page: https://openairdocs.org/ntsb/WPR18LA004 ## Probable cause A collective control malfunction for reasons that could not be determined. ## 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 · Malfunction (probable cause); cases with it: [Williams Helicopter UH-1H, 1 case](https://openairdocs.org/ntsb-findings/01046710/cases.md?model=9790870), [All aircraft, 28 cases](https://openairdocs.org/ntsb-findings/01046710/cases.md) - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Williams Helicopter UH-1H, 2 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=9790870), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [Williams Helicopter UH-1H, 1 case](https://openairdocs.org/ntsb-events/333/sequence.md?model=9790870), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md) - [Landing: Hard landing](https://openairdocs.org/ntsb-events/092); cases with it: [Williams Helicopter UH-1H, 2 cases](https://openairdocs.org/ntsb-events/092/sequence.md?model=9790870), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) - [Landing: Dynamic rollover](https://openairdocs.org/ntsb-events/231); cases with it: [Williams Helicopter UH-1H, 1 case](https://openairdocs.org/ntsb-events/231/sequence.md?model=9790870), [All aircraft, 161 cases](https://openairdocs.org/ntsb-events/231/sequence.md) ## Analysis The pilot and mechanic reported that, before the accident, the mechanic had adjusted the helicopter’s main rotor track and balance. After the mechanic made the final adjustments, the pilot hovered the helicopter to a wash rack for cleaning. Subsequently, while the pilot was repositioning the helicopter to a nearby landing cart and just as the front portions of the skids were over the cart, the collective began to oscillate, followed by the skids striking the cart. The pilot attempted to land the helicopter as it continued to oscillate, but the right skid slid off the cart. The helicopter then rolled onto its right side and impacted the ground. The mechanic reported that all components prior to the accident were in good working order and that the track and balance adjustments had resulted in satisfactory monitoring equipment readings prior to the accident. Examination of the helicopter did not reveal evidence of any preaccident malfunctions or failures that would have precluded normal operation. The reason for the oscillations could not be determined based on the available information. ## Factual narrative On October 13, 2017, about 1015 Pacific standard time, a Williams Helicopter Corporation UH-1H helicopter, N247PV, was substantially damaged when it was involved in an accident near Arbuckle, California. The pilot was not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 repositioning flight. The pilot and mechanic reported that, before the accident, the mechanic had adjusted the main rotor track and balance. After the mechanic made the final adjustments, the pilot hovered the helicopter to a wash rack for cleaning. Subsequently, while the pilot was repositioning the helicopter to a nearby landing cart, the collective began an uncommanded surge up and down just as the front portion of the landing skids were over the cart. The skids struck the cart causing damage to the front tips. The pilot attempted to land the helicopter on the cart as the collective continued to oscillate. The right skid slid off the cart and the helicopter rolled onto its right side and impacted the ground. The mechanic reported that all components prior to the accident were in good working order and that the track and balance adjustments had resulted in satisfactory monitoring equipment readings prior to the accident. Examination of the helicopter revealed that the airframe was substantially damaged, and that the main transmission, tail rotor, and right horizontal stabilizer had fracture separated. The pitch change links were all bent, and the main rotor blades were destroyed. Examination of the helicopter did not reveal evidence of any preaccident mechanical malfunctions or failures that would have precluded normal operation. The pilot did not submit a National Transportation Safety Board Pilot/Operator Aircraft Accident Report Form 6120.1. ## Aircraft - Registration: [N247PV](https://openairdocs.org/aircraft/N247PV), registered now, S/N 65-9649, built 1965 (OpenAirDocs) - Reported make and model: WESTERN INTERNATIONAL AVIA INC UH 1H - Registry model: [Williams Helicopter UH-1H](https://openairdocs.org/model/williams-helicopter-uh-1h) (registry code 9790870) (OpenAirDocs) - Registry engine: [Lycoming T53-L-13](https://openairdocs.org/engine/lycoming-t53-l-13) (registry code 41551, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 65-9649 - Year built: 1965 - Engines: Lycoming T53-L-13 1400 horsepower turbo shaft - Damage: Substantial damage - Flight: Positioning, Part 91 - Airworthiness certificate: Special, Restricted (Special) - Departed: N/A, Arbuckle, CA - Destination: N/A, Arbuckle, CA - Airport: N/A, Private Strip - Equipment: Unknown ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 69; injuries: none; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; seat: left; restraint: none; flight hours: 1 total, 1 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 300° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 61 °F, dew point 34 °F - Altimeter: 30.17 inHg - Observed at: KMVY, 15 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 20171013024369A](https://openairdocs.org/incident/20171013024369A), Oct 13, 2017: Williams Helicopter Corp UH-1H, Arbuckle, CA, Substantial damage. On October 13, 2017 at approximately 1000 hours, UH1 aircraft N247PV experienced a collective surge while attempting to re-position to a landing cart from the… ## Docket (2 files) The files NTSB released with the investigation on February 4, 2021, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=96154. 107 KB in all. - Record of memorandum - regarding NTSB 6120 form (item 1, PDF, 1 page, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=9959431&FileExtension=pdf&FileName=ROM%206120-Rel.pdf - Record of email - federal aviation administration (item 2, PDF, 1 page, 55 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=9959422&FileExtension=pdf&FileName=ROE%20FAA-Rel.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.