# NTSB LAX97FA149: Aerospatiale AS350D, N317LT, Los Angeles, CA, April 7, 1997 - Type: NTSB accident investigation - Classification: Accident · No injuries · Field investigation · Final report - Date: April 7, 1997, 12:09 local (19:09 UTC) - Place: Los Angeles, CA - Coordinates: 34.029628, -118.260627 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.0296&lon=-118.2606&mi=10 - Phase of flight: [Standing](https://openairdocs.org/ntsb-phases/150) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report December 31, 1998 - Report: Approved by Office Director - NTSB case key (mKey): 29614 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX97FA149 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29614/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=29614 - Page: https://openairdocs.org/ntsb/LAX97FA149 ## Probable cause the pilot's failure to ensure that the collective lock was properly seated before deplaning. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Miscellaneous/other, standing - engine(s) operating - aircraft unattended/engine(s) running - intentional, pilot in command - control friction - not set, pilot in command (cause) - ground resonance (cause) ## Analysis The pilot exited the helicopter to escort a deplaning passenger. The student pilot rated passenger was left sitting in the helicopter with instructions not to touch the controls. While the pilot was standing nearby, the helicopter began bouncing up and down in a resonant mode. The pilot ran back to the helicopter and pulled the fuel flow control lever into the cut-off position. The helicopter yawed to the right and settled back on the deck. Investigation revealed the full down position of the collective was spring loaded to keep tension against the control lock. An inspection of the helicopter revealed that the collective was not down and locked, nor were the frictions tightly applied. The manufacturer reported instances in which the collective lock was not seated properly, and consequently, the collective became released while the engine was running. If the lock slips off collective, the spring's tension could force the control to move upward. No malfunction or failure was found with the engine or rotor systems. ## Factual narrative HISTORY OF FLIGHT On April 7, 1997, at 1209 hours Pacific daylight time, an Aerospatiale AS350D, N317LT, experienced a resonant series of uncommanded takeoffs and landings after landing at the Transamerica heliport in downtown Los Angeles, California. The aircraft sustained substantial damage; however, neither the pilot nor his student pilot rated passenger were injured. There were no ground injuries or damage. The aircraft, operated by Bravo Helicopters of Torrance, California, was awaiting a repositioning flight under 14 CFR Part 91 when the accident occurred. The helicopter had just completed an on-demand air taxi flight under 14 CFR Part 135 and deplaned a non-revenue passenger. The flight originated at the University of California, San Diego, California, at 1100 on the morning of the accident. Visual meteorological conditions prevailed at the time and a company flight plan was filed. After approaching at the Transamerica building on a 250-degree heading, the pilot made a left pedal turn to 180 degrees, set the aircraft down on the deck, and applied the collective lock and control frictions. He then exited the aircraft, opened the right cabin door, and escorted his passenger to the heliport stairway, where they were met by a building security guard. His student pilot rated passenger remained sitting in the left front seat, with instructions not to touch the aircraft controls. The pilot, who was standing with his back toward the aircraft at the time, was just saying goodbye to his passenger, when the security guard exclaimed "Holy Cow!" The security guard stated that, while he was looking, the aircraft began bouncing up and down in a resonant mode until reaching a height of nearly 2 to 3 feet with a frequency that he equated with someone dribbling a basketball. He said he also recalled hearing the engine accelerate about the same time the bouncing began. The pilot, who had glanced back over his shoulder, now also saw what was happening. He ran around the nose of the aircraft and climbed back in the cockpit. The pilot said that after he climbed back into his seat, he immediately pulled the fuel flow control (FFC) lever into the cut off position, effectively shutting down the engine. After bouncing several times with increasing amplitude, the aircraft suddenly yawed to the right, turning about 40 degrees. The aircraft came to rest on a heading of 220 degrees with its stinger resting against the railing on the east side of the heliport. After he shut down the aircraft, both he and his student pilot passenger were able to exit the aircraft without difficulty. The student pilot confirmed that he saw the pilot apply the control frictions and the collective lock. He reported that the aircraft began rocking and yawed to the right after the pilot re-entered the cockpit. He said that when the aircraft movement occurred, his first reaction was to grab his seat in order to brace himself. He denied touching the controls at any time. PERSONNEL INFORMATION The pilot is the owner and chief pilot of Bravo Helicopters, the operator of the aircraft. AIRCRAFT INFORMATION A manufacturer's representative reported that they are aware of instances in the past in which the collective lock was not seated properly and consequently released the collective while the engine was running. The fully down position of the collective is spring loaded to keep tension against the control lock. WRECKAGE AND IMPACT INFORMATION During a postaccident inspection of the aircraft, the Safety Board noticed that the collective was not down and locked. A further inspection of the controls revealed that the frictions were not tightly applied. The No. 2 red Starflex Star arm was separated and that the tailboom was buckled aft of its attachment point to the fuselage. TESTS AND RESEARCH The engine and fractured Starflex Star arm were removed and submitted to their respective manufacturer's facilities for examination. Allied Signal performed an engine inspection and functional test run in an instrumented test cell. During the inspection it was noted that the combustor drain gasket was damaged and a bolt was missing from the customer bleed pad. The engine was not repaired, but rather was installed in a test cell, started, and brought up to 70 percent Ng and then 100 percent Ng where it ran without surging. During the run it met all the points on the power curve specifications. The No. 2 red Starflex Star arm was inspected by Eurocopter. The manufacturer reported that the arm met its specifications regarding its material, curing, part health and dimensional and stiffness checks. They identified the fracture as a static rupture which occurred while the load was in the flap/drag mode. ADDITIONAL INFORMATION The aircraft was recovered by Aircraft Recovery Services and transported to Rotorcraft Support, Inc., in Van Nuys, California. The aircraft was released to a representative of the registered owner on May 5, 1997. ## Aircraft - Registration: [N317LT](https://openairdocs.org/deregistered/N317LT-2005-05-18), registration cancelled 2005-05-18, S/N 1403 (OpenAirDocs) - Reported make and model: Aerospatiale AS350D - Registry model: [S N I A S AS350D ASTAR](https://openairdocs.org/model/s-n-i-a-s-as350d-astar) (registry code 8680803) (OpenAirDocs) - Category: Helicopter - Serial number: 1403 - Airframe hours: 9051 - Engines: Lycoming LTS-101-600A 531 horsepower turbo shaft - Damage: Substantial damage - Flight: Positioning, Part 91 - Operator: Benbow Helicopters, doing business as Bravo Helicopters - Registered owner: Thomas D. Thomas - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, February 28, 1997, 18 hours before - Departed: UC SAN DIEGO, CA - Destination: 63L - Airport: 63L, Transamerica Bldg Helipad ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 34; airline transport, flight instructor; instrument ratings: helicopter; medical: class 1, valid medical--no waivers/lim.; seat: right; flight hours: 6,582 total, 300 in this make and model, 6,466 as pilot in command, 272 in the last 90 days, 95 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 210° at 6 knots - Visibility: 9 statute miles - Lowest ceiling: none - Temperature: 57 °F, dew point 54 °F - Altimeter: 30.00 inHg - Observed at: LAX, 12 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 19970407005459A](https://openairdocs.org/incident/19970407005459A), Apr 7, 1997: Snias AS350D, Los Angeles, CA, Substantial damage. The pilot exited the aircraft in order to escort a deplaning passenger. The student pilot rated passenger was left sitting in the aircraft, with instructions… ## Docket (15 files) The files NTSB released with the investigation on July 16, 1998, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=29614. 3.7 MB in all. - Supplement C - Wreckage Documentation (item 1, .PDF, 402 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087206&FileExtension=.PDF&FileName=Supplement%20C%20-%20Wreckage%20Documentation-Master.PDF - Supplement D - Cockpit Documentation (item 2, .PDF, 523 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087207&FileExtension=.PDF&FileName=Supplement%20D%20-%20Cockpit%20Documentation-Master.PDF - Supplement S - Aircraft Occupant and Injured Ground Personnel (item 3, .PDF, 73 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087208&FileExtension=.PDF&FileName=Supplement%20S%20-%20Aircraft%20Occupant%20and%20Injured%20Ground%20Personnel-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 4, .PDF, 545 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40469889&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Witness Statements (item 5, .PDF, 210 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40469890&FileExtension=.PDF&FileName=Witness%20Statements-Master.PDF - Wreckage Diagram (item 6, .PDF, 33 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087211&FileExtension=.PDF&FileName=Wreckage%20Diagram-Master.PDF - Report from FAA Airworthiness Inspector (item 7, .PDF, 94 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40469891&FileExtension=.PDF&FileName=Report%20from%20FAA%20Airworthiness%20Inspector-Master.PDF - Report from Eurocopter (item 8, .PDF, 510 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40469892&FileExtension=.PDF&FileName=Report%20from%20Eurocopter-Master.PDF - Report from Allied Signal (item 9, .PDF, 600 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40469896&FileExtension=.PDF&FileName=Report%20from%20Allied%20Signal-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 10, .PDF, 374 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40469897&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Master.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 11, .PDF, 143 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40469898&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Master.PDF - Photo 1. View of crumpled tail boom. (item 12, .PDF, 41 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087217&FileExtension=.PDF&FileName=Photo%201.%20%20View%20of%20crumpled%20tail%20boom.-Master.PDF - Photo 2. View of No. 2 Red Starflex Star Arm. (item 13, .PDF, 45 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087218&FileExtension=.PDF&FileName=Photo%202.%20%20View%20of%20No.%202%20Red%20Starflex%20Star%20Arm.-Master.PDF - Photo 3. Left to right view of the rotor brake fuel flow corerol fuel shutoff and collective with lock disconnected. (item 14, .PDF, 42 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087219&FileExtension=.PDF&FileName=Photo%203.%20%20Left%20to%20right%20view%20of%20the%20rotor%20brake%20fuel%20flow%20corerol%20fuel%20shutoff%20and%20collective%20with%20lock%20disconnected.-Master.PDF - Photo 4. View of stinger's contact on stair rail. (item 15, .PDF, 35 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087220&FileExtension=.PDF&FileName=Photo%204.%20%20View%20of%20stinger%27s%20contact%20on%20stair%20rail.-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.