Horizon Airlines Bombardier DHC-8-401 incident
Bombardier DHC-8-401 · Incident: airframe, component or system failure en route
From Seattle–Tacoma International Airport (SEA) to Boise Air Terminal/Gowen Field (BOI)
Event
- NTSB case
- SEA02IA044
- 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
- Incident
- 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
- Airline
- 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
Bombardier DHC-8-401
- Aircraft type
- Bombardier DHC-8
- Category
- Airplane
- 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
- N410QX
- Operator
- Horizon Airlines
- Onboard fatalities
- Unknown
- Route
- From Seattle–Tacoma International Airport (SEA), Seattle, WATo Boise Air Terminal/Gowen Field (BOI), Boise, ID
- 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 121: Air Carrier
- 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
- None
Cause areas
- Fluid, hydraulic › Starvation
- Hydraulic system › Inoperative
- Hydraulic system, line › Failure, partial
Approximate · Estimated position: the centre of Boise, ID, the place the record names. Not the accident site.
NTSB narrative
During en route cruise, there was a failure of a number two system elevator hydraulic line. This resulted in a loss of hydraulic fluid and loss of pressurization in the number two system. The loss of this system resulted in the rudder being dependent upon the sole remaining activation system (hydraulic system number one) for its operation. After the landing gear was lowered manually, the aircraft landed without further incident, but because the loss of the number two system rendered the nose wheel steering inoperative, the aircraft had to be towed from the runway. The reason for the failure of the hydraulic line could not be positively determined.
Probable cause
The partial failure of one of the number two hydraulic system elevator hydraulic lines, leading to the loss of fluid and pressure in that system during cruise flight. This loss resulted in reliance upon the sole remaining activation system (number one hydraulic) to operate the rudder.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA02IA044
- Event ID
- 20020312X00331
- Case number
- SEA02IA044
- 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: local date, investigation status, damage. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 2002-03-02.
- API snapshot SHA-256: f8028618e738f3b5dc3518672e9130c712d5f956984e085287c64d27cc406085; retrieved 2026-09-18T16:05:16.568Z.