LAX98LA139 · Bell 206B
Papillon Airways Bell 206B · Accident: partial loss of engine power (mechanical failure) during landing
From Grand Canyon National Park Airport (GCN) to an unrecorded destination
Event
- NTSB case
- LAX98LA139
- 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
Bell 206B
- Aircraft type
- Bell 206
- 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
- N8533F
- Operator
- Papillon Airways
- Onboard fatalities
- Unknown
- Route
- From Grand Canyon National Park Airport (GCN), AZTo 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 91: General Aviation
- 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
- Landing · flare/touchdown
- 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
- Partial loss of engine power (mechanical failure)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Turboshaft engine, free turbine governor › Erratic
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The instructor pilot and new company pilot were practicing autorotations, which were terminating in a power-recovery. The flight instructor demonstrated a straight-in autorotation and said that the governor lagged behind but stayed in the green range. The instructor stated that this was typical of this particular helicopter and that he didn't consider the governor lag unusual. The instructor then had the dual student set up for a 180-degree autorotation. During the maneuver he told the student that he was ready to roll on the throttle at 200 feet agl. He stated that at 50 feet and 50 to 55 knots, the pilot flared the helicopter and at 15 feet he had the pilot pull in more collective. At this point, the instructor pulled in some collective himself. He stated that the torque gauge did not move and that it sounded like the engine sound was dragging down and the rpm's in the dual tach decayed. The flight instructor proceeded to take the controls and level the aircraft. The aircraft landed hard and came to a complete stop. After the aircraft was shut down, the tail boom was found still attached but hanging to the ground. A Bell Operations Safety Notice advises that tail boom failure can occur in autorotations where touchdown occurs at 70 percent main rotor speed due to a resonance response of the structure to the main rotor. A postaccident test of the governor function was performed. Power checks were done to duplicate an autorotation and the tests revealed that the engine was slow to accelerate and the governor surged with continual fluctuation of Ng readings.
Probable cause
The malfunction and erratic speed control of the engine's governor, and the flight instructor's delayed remedial action.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record LAX98LA139
- Event ID
- 20001211X09892
- Case number
- LAX98LA139
- 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: 505ded58d357207f4d726b7ba235ae4e4861e5987236613d5a904f118a4c1b4b; retrieved 2026-09-22T17:52:08.397Z.