Flight 689 · Fokker F-28-4000
Fokker F-28-4000 · Incident: airframe, component or system failure en route
From Pittsburgh International Airport (PIT) to an unrecorded destination
Event
- NTSB case
- CHI95IA045
- 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
- 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
- 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
Fokker F-28-4000
- Aircraft type
- Fokker F-28
- 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
- N479AU
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Pittsburgh International Airport (PIT), Pittsburgh, PATo 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 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 · descent
- 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
- Company maintenance personnel › Maintenance, service of aircraft/equipment, improper
- Fluid, hydraulic › Lack of
Approximate · Estimated position: the centre of Evansville, IN, the place the record names. Not the accident site.
NTSB narrative
THE FLIGHT CREW REPORTED THAT WHILE DESCENDING FROM CRUISE IN PREPARATION FOR LANDING, THEY NOTICED THAT THE HORIZONTAL STABILIZER WAS NOT RESPONDING TO TRIM INPUTS. THE AUTOPILOT WAS DISENGAGED, AND BOTH NORMAL AND ALTERNATE MODES OF STABILIZER TRIM WAS ATTEMPTED WITHOUT SUCCESS. THE CREW FOLLOWED THE JAMMED STABILIZER APPROACH CHECKLIST, AND WAS ABLE TO EFFECT PITCH CHANGES BY BOTH CREW MEMBERS EXERTING FORCE ON THEIR CONTROL YOKES. POSTINCIDENT INSPECTION OF THE STABILIZER DRIVE ACTUATOR DISCOVERED NO HYDRAULIC LEAKS. THE ACTUATOR'S GEAR BOX WAS DRAINED, AND FOUND TO CONTAIN APPROXIMATELY ONE OUNCE OF MURKY, SLUDGE-LIKE HYDRAULIC FLUID. THE GEAR BOX IS REQUIRED TO BE FILLED WITH SEVEN OUNCES OF HYDRAULIC FLUID. THE ACTUATORS ARE SHIPPED FROM THE MANUFACTURER ESSENTIALLY DEVOID OF HYDRAULIC FLUID, WITH INSTRUCTIONS THAT THEY MUST BE FILLED PRIOR TO SERVICE.
Probable cause
the failure of company maintenance personnel to adequately service (fill) the horizontal stabilizer drive actuator with hydraulic fluid.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI95IA045
- Event ID
- 20001206X02568
- Case number
- CHI95IA045
- 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, damage. 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: aa133bbf0889b2485e4597b8569444c6c59181255d3fd029a76f6227cb1e3e6c; retrieved 2026-09-18T18:05:55.907Z.