MIA99TA206 · Hughes OH-6A
Hughes OH-6A · Accident: airframe, component or system failure en route
From Rafael Hernández International Airport (BQN) to an unrecorded destination
Event
- NTSB case
- MIA99TA206
- 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
- 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
Hughes OH-6A
- Aircraft type
- Hughes OH-6
- 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
- N66377
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Rafael Hernández International Airport (BQN)To 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
- 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
- Airframe, component or system 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
- Lubricating system, oil cooler › Foreign object damage
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
While in cruise flight at 800 feet, the pilot heard a metal grinding noise followed by the engine failure warning. The pilot entered autorotation and during landing flare he was unable to arrest the descent, resulting in a hard landing and damage to the helicopter. Postcrash examination of the engine and engine systems showed no anomalies. Examination of the main transmission showed no damage which cause seizing of the transmission. Examination of the oil cooler blower assembly showed one impeller blade was fractured due to overload which opened a two inch gap in the impeller. The blower stopped spinning and sheared away from the adapter. The impeller shroud had abrasion damage and some minor areas of debris buildup. The oil cooler is driven by the main transmission.
Probable cause
An unidentified foreign object passing through the oil cooler blower assembly resulting in fracture and seizure of the oil cooler blower, and slowing of the main transmission and main rotor, which resulted in the pilot being unable to arrest the descent during an autorotative landing.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record MIA99TA206
- Event ID
- 20040218X00198
- Case number
- MIA99TA206
- 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: db57d390f25dee1e5c5723806d15a534b8e5c8a58e3f63d93f88c35a4e4e1210; retrieved 2026-09-22T14:22:26.228Z.