SEA01TA143 · Boeing Helicopters Div. H500D
Boeing Helicopters Div. H500D · Accident: loss of engine power en route
From Yakima Air Terminal McAllister Field (YKM) to an unrecorded destination
Event
- NTSB case
- SEA01TA143
- 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
- Unknown
- 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
- Government
- 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
Boeing Helicopters Div. H500D
- Aircraft type
- Boeing Helicopters Div H500
- 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
- N8964T
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Yakima Air Terminal McAllister Field (YKM), Yakima Air Term, WATo 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
- Public Aircraft
- 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
- En route · cruise
- 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
- Loss of engine power
- 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
- Reason for occurrence undetermined
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
While cruising at 1,000 feet above the ground, the helicopter encountered an area of strong updrafts and downdrafts. As it passed through one particularly strong downdraft, the aircraft experienced a complete loss of power. The pilot then initiated an autorotation to the only available landing area. Because the area was small and surrounded by trees, the pilot found it necessary to execute an abrupt flare in order to arrest the forward movement of the helicopter prior to colliding with the trees ahead. The abrupt flare resulted in a hard landing, and the main rotor blades flexed downward far enough to sever the tail boom. Post-accident inspections of the engine and aircraft systems did not reveal any malfunctions or anomalies that would have been expected to contribute to a loss of power. Although the flight manual warned of possible fuel starvation associated with large side slip angles of uncoordinated flight with less than 35 pounds of fuel remaining, approximately 115 pounds of fuel were drained from the helicopter's main fuel bladder.
Probable cause
The complete loss of engine power at cruise for undetermined reasons. Factors include a landing area that was restricted/confined due to adjacent trees, and an intentional abrupt flare resulting in a hard landing.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA01TA143
- Event ID
- 20010806X01611
- Case number
- SEA01TA143
- 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: 1d524921e8b49eb94a68db5d4c5efe6dd154e93897c98c78c900c20dee125887; retrieved 2026-09-18T21:20:14.143Z.