Prism Helicopters Hughes 500D accident
Hughes 500D · Accident: partial loss of engine power (mechanical failure) during initial climb
From SUMMIT LAKE, AK to an unrecorded destination
Event
- NTSB case
- ANC95LA107
- 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
- Charter & commuter
- 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
Hughes 500D
- Aircraft type
- Hughes 500
- 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
- N8639F
- Operator
- Prism Helicopters
- Onboard fatalities
- Unknown
- Route
- From SUMMIT LAKE, AKTo 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 135: Air Taxi & Commuter
- 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
- Initial climb
- 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)
- 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
- Fuel starvation
- 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
- Fluid, fuel › Starvation
- Fuel system, fuel control › Contamination, other than water
- Terrain condition › None suitable
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
THE HELICOPTER PILOT WAS TRANSPORTING A GEOLOGIST IN A REMOTE AREA. AFTER DEPARTING FROM A PICKUP SITE THAT WAS AT AN ELEVATION OF ABOUT 5,000 FEET MEAN SEA LEVEL, THE PILOT NOTICED A DECREASE IN MAIN ROTOR RPM, AND THE NOSE OF THE HELICOPTER YAWED. THE PILOT DECREASED COLLECTIVE PITCH, BUT ENGINE POWER AND ROTOR RPM CONTINUED TO DECREASE. THE PILOT TURNED THE HELICOPTER TOWARD LOWER TERRAIN AND INTO THE WIND, THEN PERFORMED AN AUTOROTATION ON TUNDRA COVERED TERRAIN. DURING TOUCHDOWN, THE HELICOPTER HIT THE GROUND HARD, AND THE TAIL BOOM WAS SEVERED BY THE MAIN ROTOR BLADES. THE ENGINE WAS STILL RUNNING AFTER LANDING. AN INSPECTION OF THE ENGINE FUEL CONTROL ASSEMBLY REVEALED THE PRESENCE OF ACRYLAMIDE CONTAMINATION IN THE FUEL INLET FILTER.
Probable cause
FUEL STARVATION DUE TO ACRYLAMIDE CONTAMINATION IN THE FUEL CONTROL INLET FILTER. THE LACK OF SUITABLE TERRAIN FOR A FORCED LANDING WAS A RELATED FACTOR.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ANC95LA107
- Event ID
- 20001207X03839
- Case number
- ANC95LA107
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (5)
- 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: b6c45a6cd7f3a3f070179a5362ea987539f702601990a04c9b1b84288e661fd3; retrieved 2026-09-18T17:59:01.181Z.
- The NTSB's operator name is blank for N8639F; the operator shown is the name the NTSB's other records give its FAA operator code, EOOA.