# NTSB LAX02TA299: Eurocopter AS350-B3, N352SA, Bishop, CA, September 29, 2002 - Type: NTSB accident investigation - Classification: Accident · No injuries · Final report - Date: September 29, 2002, 08:54 local (15:54 UTC) - Place: Bishop, CA - Coordinates: 37.372776, -118.363609 - Nearby events: https://openairdocs.org/map.md?lat=37.3728&lon=-118.3636&mi=10 - Phase of flight: [Standing](https://openairdocs.org/ntsb-phases/150) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 4 uninjured - Status: Completed, report June 8, 2005 - Report: Approved by Office Director - Parties: U.S. Forest Service, Federal Aviation Administration - NTSB case key (mKey): 55797 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX02TA299 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/55797/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=55797 - Page: https://openairdocs.org/ntsb/LAX02TA299 ## Probable cause the disengagement of the collective locking mechanism due to component wear. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, standing - engine(s) operating - rotorcraft flight control,collective control - worn (cause) - rotorcraft flight control,collective control - unlocked (cause) - hydraulic system - not available (cause) - Loss of control - on ground/water, standing - engine(s) operating - collective - inadvertent activation - On ground/water encounter with terrain/water, standing - engine(s) operating - terrain condition - ground ## Analysis The helicopter was performing a hydraulic actuator check for the first flight of the day. The collective had been placed in the down position, the collective lock was engaged, and the rotor powered up to 100 percent flight idle. After depressing the hydraulic test switch, the pilot moved the cyclic fore and aft to confirm there was pressure remaining in the accumulators for a few control movements. The collective rose uncommanded and the helicopter moved forward in a nose down attitude. The main rotor struck the ground and the helicopter made two revolutions before rolling over onto its side, destroying both the main and tail rotor systems. A small fire ensued in the exhaust area, but was quickly extinguished. Examination of the collective locking mechanism (P/N 350A-27 3455-20 and P/N 350A-27 3107-26) found that it failed to hold the collective in the full down position due to wear on the locking tab. During servo accumulator checks, movement of the cyclic control after accumulator depletion caused the collective to move due to feedback in the control system. The locking device disengaged and the collective increased causing the aircraft to move. ## Factual narrative On September 29, 2002, about 0854 Pacific daylight time, an Eurocopter AS350-B3, N352SA, collided with terrain during a premature liftoff while engaged in a pre-departure hydraulic flight control check at the Bishop, California, airport. The U.S. Forest Service was operating the helicopter as a public-use flight under the provisions of 14 CFR Part 91. The commercial pilot and three passengers were not injured; the helicopter sustained substantial damage. The cross-country flight was departing the Bishop airport for Bridgeport, California. Visual meteorological conditions prevailed, and an agency flight plan had been filed. Forest Service officials reported that the helicopter was performing a hydraulic actuator check for the first flight of the day. The collective had been placed in the down and locked position and the rotor powered up to 100 percent flight idle. After depressing the hydraulic test switch, the pilot moved the cyclic fore and aft (pumped) to confirm there was remaining pressure for a few control movements. The collective rose uncommanded and the helicopter moved forward in a nose down attitude. The main rotor struck the ground and the helicopter made two revolutions before rolling over onto its side, destroying both the main and tail rotor systems. A small fire ensued in the exhaust area, but was quickly extinguished. Examination of the collective locking mechanism was accomplished by Forest Service investigators. According to their report, the collective control lock mechanism (P/N 350A-27 3455-20 and P/N 350A-27 3107-26) failed to hold the collective in the full down position (due to wear) while performing before takeoff checks. During servo accumulator checks, movement of the cyclic control after accumulator depletion caused the collectiove to move (feedback). The locking device disengaged and the collective increased causing the aircraft to move. ## Aircraft - Registration: [N352SA](https://openairdocs.org/aircraft/N352SA), registered now, S/N 3348 (OpenAirDocs) - Reported make and model: Eurocopter AS350-B3 - Registry model: [Eurocopter AS 350 B3](https://openairdocs.org/model/eurocopter-as-350-b3) (registry code 8680954) (OpenAirDocs) - Category: Helicopter - Serial number: 3348 - Airframe hours: 736 - Engines: Turbomeca Arriel 1D1 420 horsepower turbo shaft - Damage: Substantial damage - Fire: On-Ground - Flight: Public aircraft, Public use - Operator: US Dept of Agriculture, US Forest Service - Registered owner: Sun Air Aviation, LLC - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, August 16, 2002, 86 hours before - Departed: BIH, Bishop, CA - Destination: O57, Bridgeport, CA - Flight plan: VFR - Airport: BIH, Bishop ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 27; injuries: minor; private, flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 2, with waivers/limitations; last flight review February 11, 2002; seat: right; flight hours: 3,000 total, 350 in this make and model, 2,900 as pilot in command, 210 in the last 90 days, 37 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 340° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 45 °F, dew point 30 °F - Altimeter: 29.93 inHg - Observed at: KBIH ## 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 20020929025099A](https://openairdocs.org/incident/20020929025099A), Sep 29, 2002: Snias AS350B3, Bishop, CA, Substantial damage. (-23) During pre-take off hydraulic check, with hydraulics off, aircraft became airborne and rolled. Aircraft ended up on right side. (.19) on September 29,… ## Docket (4 files) The files NTSB released with the investigation on March 21, 2005, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=55797. 683 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 273 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40446033&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - USFS Aviation Safety Alert (item 2, .PDF, 76 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40222283&FileExtension=.PDF&FileName=USFS%20Aviation%20Safety%20Alert-Master.PDF - Photo 1. Collective Lock Strip (item 3, .PDF, 179 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40170531&FileExtension=.PDF&FileName=Photo%201.%20%20Collective%20Lock%20Strip-Master.PDF - Photo 2. Worn Collective Stud (item 4, .PDF, 155 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40170532&FileExtension=.PDF&FileName=Photo%202.%20%20Worn%20Collective%20Stud-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.