United Airlines Flight 731
Airbus A320 232 · Incident: electrical system malfunction/failure during initial climb
From Newark Liberty International Airport (EWR) to Denver International Airport (DEN)
Event
- NTSB case
- DCA08IA033
- 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
Airbus A320 232
- Aircraft type
- Airbus A320
- 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
- N462UA
- Operator
- United Airlines
- Onboard fatalities
- Unknown
- Route
- From Newark Liberty International Airport (EWR), Newark, NJTo Denver International Airport (DEN), Denver, CO
- Aircraft age
- About 8 years (built 2000)
- 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
- Initial climb
- Defining eventThe 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
- Electrical system malfunction/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
- Aircraft › Aircraft systems
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
This incident occurred when United Airlines flight 731 experienced a fault in the airplane's AC 1 electrical bus, one of the two primary electrical distribution systems for the airplane, which in turn caused a number of other electrical busses on the aircraft to lose power. The loss of this electrical power led to the loss of a number of aircraft displays and systems. During the flights return to the airport, multiple messages on the electronic centralized aircraft monitoring (ECAM) system, which provides information to the crew regarding failures that have occurred on the aircraft along with recommended corrective actions, were being displayed then removed by the ECAM system, making it difficult for the flight crew to interpret and address the error messages. There were no faults found in the airplane wiring and the testing and teardown found don faults in the #1 integrated drive generator (IDG), bus tie contactor (BTC), and generator control unit (GCU).
Probable cause
a fault in the airplane's AC 1 electrical bus that caused a number of other electrical busses on the aircraft to lose power.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record DCA08IA033
- Event ID
- 20080514X00667
- Case number
- DCA08IA033
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
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: fad22fc10242b75a5bc922cddfc99d526d2b35966368822f5231440a9fc8c091; retrieved 2026-09-15T09:39:00.231Z.