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| Date: | Friday 11 June 1999 |
| Time: | 21:18 LT |
| Type: |  Boeing 777-222 |
| Owner/operator: | United Air Lines |
| Registration: | N781UA |
| MSN: | 26945/40 |
| Year of manufacture: | 1996 |
| Total airframe hrs: | 11389 hours |
| Engine model: | P&W PW4077 |
| Fatalities: | Fatalities: 0 / Occupants: 296 |
| Aircraft damage: | None |
| Category: | Accident |
| Location: | Madison, WI -
 United States of America
|
| Phase: | Unknown |
| Nature: | Passenger - Scheduled |
| Departure airport: | Minneapolis, MN (MSP) |
| Chicago-O'Hare International Airport, IL (ORD/KORD) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
While en route from Minneapolis to Chicago the flight encountered turbulence at 19,680 feet msl while in a descent. Four passengers and four flight attendants received minor injuries. One passenger received a broken ankle. The flight had diverted to Minneapolis due to thunderstorm activity in the Chicago area. The captain reported the flight was smooth up until the unexpected turbulence was encountered. The seat belt sign was not on at the time of the encounter. The flight crew received a Weather Briefing Message (WBM) prior to departing Minneapolis, which contained convective sigmets for Wisconsin, Illinois, and Indiana. The accident took place ahead of a stationary front which extended northeast-southwest through central Wisconsin and Iowa which had been creating shower and thunderstorm activity throughout afternoon and evening on the day of the accident. A review of the data from the Quick Access Recorder revealed the flight experienced a change in G-loading from .0843 g's to 1.9375 g's over a 2-second time period while at an altitude of 19,680 feet msl.
Probable Cause: the pilot-in-command's inadequate evaluation of the weather conditions. Factors associated with the accident were the turbulence encountered and the seat belt sign was not illuminated.
Accident investigation:
 |
|
Sources:
NTSB CHI99LA184
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 09-Mar-2024 11:22 | ASN Update Bot | Added |
Corrections or additions? ... Edit this accident description
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