United Airlines Flight 20
Boeing 767-200 · Incident: airframe, component or system failure on approach
From San Francisco International Airport (SFO) to John F. Kennedy International Airport (JFK)
Event
- NTSB case
- NYC00IA036
- 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
Boeing 767-200
- Aircraft type
- Boeing 767
- 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
- N610UA
- Operator
- United Airlines
- Onboard fatalities
- Unknown
- Route
- From San Francisco International Airport (SFO), San Francisco, CATo John F. Kennedy International Airport (JFK), Jamaica, NY
- 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
- Approach
- 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
- Flt control syst, stabilator control › Failure, total
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
While on final, the first officer had trouble trimming the airplane. The captain attempted to trim the airplane via his yoke switch and the manual trim handle, with no success. A go-around was executed. The crew ran the checklist, but control of the stabilizer trim was not regained. The crew pulled circuit breakers H11 and H20, and then reset them. The stabilizer trim was still inoperative. The crew reset the trim cutout switches twice, and normal operation of the stabilizer trim was reestablished. The left stabilizer position transmitter, and the right stabilizer position transmitter were out of calibration. Also, the left stabilizer trim control module (STCM) was found to have a higher than normal leakage, and the connector for the corresponding shut-off valve was shorting across several of its pins due to skydrol incursion. No faults were identified for the right system except for the right-stabilizer-position transmitter. According to the operator, the system should have operated at half rate with the above discrepancy, but did not. There have been no reports of difficulties with the airplane's stabilizer trim system since the event.
Probable cause
Total failure of the stabilizer control system for undetermined reasons.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record NYC00IA036
- Event ID
- 20001212X20152
- Case number
- NYC00IA036
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (5)
- 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 1999-11-21.
- API snapshot SHA-256: 68342a3cdd3eef6093a98b1c40b1931c092ca3fea942747c047e538973676352; retrieved 2026-09-18T16:51:07.658Z.
- The NTSB's operator name is blank for N610UA; the operator shown is the name the NTSB's other records give its FAA operator code, UALA.