SEA99FA037 · Hiller UH-12E
Hiller UH-12E · Accident: uncontrolled altitude deviation while taxiing
Event
- NTSB case
- SEA99FA037
- 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
Hiller UH-12E
- Aircraft type
- Hiller UH-12
- 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
- N2239
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From not recordedTo 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
- Taxi · aerial
- 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
- Uncontrolled altitude deviation
- 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
No findings designated as a cause are recorded in the NTSB data yet.
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The aircraft departed the airport for the second surveillance flight of the day. Shortly after departure, the pilot was contacted by a ground crew member and informed that a 55 gallon fuel barrel was knocked over during the helicopter's departure. The pilot elected to returned to the airport and inspect the helicopter for possible damage that may have occurred. The pilot made a normal approach to the airport and was established in a hover taxi, when the helicopter suddenly began to descend. The pilot stated that he increased up collective without a response. The pilot then pulled full up-collective, however the helicopter continued to descend. The helicopter impacted terrain in a slightly nose-low attitude. After contacting the ground, the pilot released the collective and the main rotor blades struck and severed the tail boom assembly. The helicopter canted to the left and partially rolled to one side. At the time of the accident, the helicopter was operating near gross weight at an elevation of 3,835 feet mean sea level (MSL).
Probable cause
Altitude deviation during aerial taxi for undetermined reasons.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA99FA037
- Event ID
- 20001205X00240
- Case number
- SEA99FA037
- 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: 6571aff04ec4cb741bf46be70fa60a5b5d5f47656734cab03afc2b370083a013; retrieved 2026-09-22T15:46:38.903Z.