UPS Boeing 747-123 incident
Boeing 747-123 · Incident: airframe, component or system failure en route
From Bowman Field (LOU) to Ted Stevens Anchorage International Airport (ANC)
Event
- NTSB case
- CHI98IA164
- 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
- Unknown
Boeing 747-123
- Aircraft type
- Boeing 747
- 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
- N675UP
- Operator
- UPS
- Onboard fatalities
- Unknown
- Route
- From Bowman Field (LOU), Louisville, KYTo Ted Stevens Anchorage International Airport (ANC), Anchorage, AK
- 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
- Electrical system, electric wiring › Other
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
While troubleshooting a fire warning indication with company maintenance control using the #2 VHF transceiver, the crew experienced several uncommanded 'kicks' of the yaw damper. The crew turned off the upper yaw damper, but not the lower. They continued to experience 'kicks' although not as severe. The flight departed to Minneapolis where it landed uneventfully. Inspection of the airplane after the incident revealed an open shield at the #2 VHF coax connector which is located near the yaw damper control box. The connector was replaced and the airplane was returned to service.
Probable cause
the open shielding on the #2 VHF transceiver coax connector which resulted in electromagnetic interference with the yaw damper system.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI98IA164
- Event ID
- 20001211X09999
- Case number
- CHI98IA164
- 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: 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: 0919ef51de353c79b784b87efc8741aaf523f37c836b52171534028303ed20f6; retrieved 2026-09-18T17:09:12.844Z.
- The NTSB's operator name is blank for N675UP; the operator shown is the name the NTSB records it doing business as.