# NTSB WPR24LA299: Williams Helicopter UH-1H, N710WD, Colusa, CA, August 30, 2024 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Class 4 · Limited · Final report - Date: August 30, 2024, 07:05 local (14:05 UTC) - Place: Colusa, CA - Coordinates: 39.247946, -121.99082 - Nearby events: https://openairdocs.org/map.md?lat=39.2479&lon=-121.9908&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-hover: Loss of control in flight](https://openairdocs.org/ntsb-events/240) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed - Report: Approved by Office Director - Investigation class: Class 4 - Basic report with no Prelim publish - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 195085 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR24LA299 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/195085/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=195085 - Page: https://openairdocs.org/ntsb/WPR24LA299 ## Probable cause The pilot’s failure to set collective friction which resulted in collective bounce and subsequent loss of control. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Use of equip/info: use of equip/system](https://openairdocs.org/ntsb-findings/02063015): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Williams Helicopter UH-1H, 1 case](https://openairdocs.org/ntsb-findings/02063015/cases.md?model=9790870), [All aircraft, 1,391 cases](https://openairdocs.org/ntsb-findings/02063015/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Williams Helicopter UH-1H, 2 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=9790870), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-hover: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Williams Helicopter UH-1H, 2 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=9790870), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) ## Analysis The pilot of the helicopter reported that while repositioning closer to the loading equipment, the helicopter experienced collective bounce. He attempted to maneuver the helicopter to avoid equipment and personnel; however, control was lost and the helicopter impacted terrain. The operator reported that there were no preaccident mechanical malfunctions or failures that would have precluded normal operations. The operators manual for the helicopter stated, in part, “Collective bounce is a pilot Induced vertical oscillation of the collective control system when an absolute friction (either pilot applied, or control rigged) is less than seven pounds. It may be encountered in any flight condition by a rapid buildup of vertical bounce at approximately three cycles per second. The seventy of the oscillation is such that effective control of the helicopter may become difficult to maintain. The pilot should apply and maintain adequate collective friction in all flight conditions.” ## Aircraft - Registration: [N710WD](https://openairdocs.org/aircraft/N710WD), registered now, S/N 65-09761 (OpenAirDocs) - Reported make and model: WILLIAMS HELICOPTER CORP UH-1H - Registry model: [Williams Helicopter UH-1H](https://openairdocs.org/model/williams-helicopter-uh-1h) (registry code 9790870) (OpenAirDocs) - Registry engine: [Lycoming T-53 series](https://openairdocs.org/engine/lycoming-t-53-series) (registry code 41552, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 65-09761 - Year built: 1965 - Engines: Ozark-Aeroworks T53-L-13B 1318 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: A&P Helicopters Inc - Registered owner: A&P Helicopters Inc - Airworthiness certificate: Special, Restricted (Special) - Departed: 07CL, Richvale, CA - Airport: none - Equipment: ADS-B, Satellite tracking device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 60; injuries: serious; commercial; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review October 11, 2023; seat: right; restraint: 4-point; flight hours: 13,000 total, 22 in this make and model, 13,000 as pilot in command, 125 in the last 90 days, 50 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 130° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 70 °F, dew point 54 °F - Altimeter: 30.01 inHg - Observed at: KOVE, 23 nm away - METAR: METAR KOVE 301453Z AUTO 13003KT 10SM CLR 21/12 A3001 RMK AO2 SLP162 T02060122 53013= ## Other investigations on N710WD (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 LAX06LA134](https://openairdocs.org/ntsb/LAX06LA134), Apr 1, 2006: Bell UH-1H (N710WD), Yuba City, CA, substantial damage. Probable cause: The pilot's in-flight loss of control of the helicopter for undetermined reasons. A factor was the trees. ## Docket (4 files) The files NTSB released with the investigation on April 22, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=195085. 4.8 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 3.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18182503&FileExtension=pdf&FileName=NTSB%20Form%206120_1_Redacted-Rel.pdf - Photos (item 2, PDF, 3 pages, 788 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18486000&FileExtension=pdf&FileName=Photos%20for%20WPR24LA299_Redacted-Rel.pdf - Memorandum of record - operator (item 3, PDF, 1 page, 62 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18534497&FileExtension=pdf&FileName=ROC_A_Compton-Rel.pdf - UH-1H/V operator's manual (tm 55-1520-210-10) excerpt (item 4, PDF, 1 page, 73 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18486841&FileExtension=pdf&FileName=TM%2055-1520-210-10%20Excerpt-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.