Air Canada Boeing 767-233 incident
Boeing 767-233 · Incident: airframe, component or system failure en route
From San Francisco International Airport (SFO) to Toronto Pearson International Airport (YYZ)
Event
- NTSB case
- CHI93IA152
- 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 767-233
- 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
- CGAUP
- Operator
- Air Canada
- Onboard fatalities
- Unknown
- Route
- From San Francisco International Airport (SFO), San Francisco, CATo Toronto Pearson International Airport (YYZ), Toronto
- 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 129: Foreign
- 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
- Flt control syst, aileron control bearing › Corroded
- Flt control syst, aileron control bearing › Frozen
- Flt control syst, aileron control bearing › Worn
- Maintenance, inspection › Inadequate
- Manufacturer › Procedure inadequate
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
THE FLIGHT CREW NOTED A LOSS OF AILERON CONTROL (FELT FROZEN), WHILE CRUISING AT FL 370. THEY WERE ABLE TO MAKE HEADING CHANGES BY USING THE RUDDER & ELECTED TO DIVERT TO KANSAS CITY (MCI). THE AIRPLANE HAD BEEN EXPOSED TO RAIN & STANDING WATER BEFORE THE FLIGHT. THE CREW FELT THE LOSS OF AILERON CONTROL MAY HAVE BEEN DUE TO FROZEN WATER IN THE CONTROL SYSTEM. DURING DESCENT TO MCI, ABOVE FREEZING AIR TEMPERATURES WERE ENCOUNTERED, & CONTROL OF THE AILERONS GRADUALLY RETURNED UNTIL FULL CONTROL WAS REGAINED. AN UNEVENTFUL LANDING WAS MADE AT MCI. INVESTIGATION REVEALED WORN AILERON CONTROL BEARINGS IN THE LATERAL CONTROL ACTUATOR SYSTEM. THE WORN BEARINGS WERE TESTED BY SOAKING IN WATER & FREEZING. WATER PENETRATED A BEARING HOUSING & FROZE INSIDE THE BEARING RACE, DISABLING THE BEARING. SUBSEQUENT DISASSEMBLY OF THE BEARING DISCLOSED CORRODED & WORN BALL BEARINGS. BOEING SERVICE LETTER (767-S-27-094) & SEVICE BULLETIN 767-27-0128 WERE ISSUED TO ADDRESS INSPECTION/REPLACEMENT CRITERIA OF THE BEARINGS.
Probable cause
A FROZEN AILERON CONTROL BEARING AFTER IT HAD BECOME WORN, CORRODED AND EXPOSED TO WATER, AND THE MANUFACTURER'S INADEQUATE MAINTENANCE/INSPECTION REQUIRMENT OF THE BEARING(S).
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI93IA152
- Event ID
- 20001211X12087
- Case number
- CHI93IA152
- 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: 2773091795e120c504f56a5f5c7a0b88fa6435034c4e0891842f1451ea7bc0aa; retrieved 2026-09-18T18:39:29.131Z.