SEA99LA001 · Aerospatiale SA-315B
Aerospatiale SA-315B · Accident: in flight collision with object while maneuvering
From Bozeman Yellowstone International Airport (BZN) to an unrecorded destination
Event
- NTSB case
- SEA99LA001
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- 0
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Aerospatiale SA-315B
- Aircraft type
- Aerospatiale SA-315
- Category
- Helicopter
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N5803J
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Bozeman Yellowstone International Airport (BZN), Bozeman, MTTo not recorded
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 133: Rotorcraft Ext. Load
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Maneuvering
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- In flight collision with object
- Also codedOther events the NTSB coded in the sequence, such as a wire strike after a loss of power. Flight Findings uses them for its kinds of event. Glossary
- Tree(s)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Destroyed
Cause areas
- Ground personnel › Procedures/directives, not followed
- Rotor system, tail rotor › Separation
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The helicopter was engaged in logging operations associated with the clearing of a recreational ski lodge construction site. This was the first time the operator had worked with this particular ground crew (chokers). The chokers were briefed by the pilot-in-command (PIC) and were supposed to hook up only two marked logs at a time (marked with orange fluorescent paint). However, they hooked up three logs together, one of which was still rooted. During the lifting operation, the PIC encountered resistance and attempted to electrically release the long line several times without success. The failure of the long line to release was due to jamming because of the use of an oversize clevis attaching the hook. When the long line finally released after the use of the manual system, the helicopter rotated along its longitudinal axis at such an angle that the tail rotor contacted trees and separated from the aircraft. It then descended out of control until impacting the ground. Winds at the site were strong and gusty.
Probable cause
The failure of the ground handlers (chokers) to follow procedures, and separation of the tail rotor system. Contributing factors were incorrect long line hook (size), jamming of the hook release, trees and gusty wind conditions.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA99LA001
- Event ID
- 20001211X11347
- Case number
- SEA99LA001
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 118a62dc153e3743ee51e27ae1643f8ddea46cb0a6602c58ab2c8eb26fb143d6; retrieved 2026-09-21T20:40:44.975Z.