NTSB Identification: CHI90IA166.
The docket is stored on NTSB microfiche number 43527.
Scheduled 14 CFR MIDWAY AIRLINES, INC.
Incident occurred Friday, June 29, 1990 in CHICAGO, IL
Probable Cause Approval Date: 05/10/1993
Aircraft: MCDONNELL DOUGLAS DC-9-32, registration: N948ML
Injuries: 65 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

A PASSENGER TRANSPORT EXPERIENCED SEVERE TURBULENCE DURING AN EN ROUTE DESCENT TO DESTINATION. THE FLIGHT'S FORECAST INDICATED THUNDERSTORM DEVELOPMENT IN THE DESTINATION VICINITY. THE CREW HEARD DESTINATION ATIS ANNOUNCE SEVERE TURBULENCE ON APPROACH BUT RECALLED NO ATC ADVISORY STATING TURBULENCE WAS SEVERE. THE PILOT COMPLIED WITH ATC'S REQUEST TO SLOW FOR TRAFFIC SEPARATION, PLACING THE SPEED BELOW THAT RECOMMENDED FOR TURBULENCE PENETRATION. THE AIRPLANE WAS TURNING TO AVOID CLOUDS AND VIRGA, WITH SPEEDBRAKES EXTENDED AND AUTOPILOT ENGAGED WHEN IT ENTERED INCREASING TURBULENCE. THE AIRPLANE PITCHED UP 20 DEGREES AND ROLLED TO 45 DEGREES. THE PILOT RIGHTED THE AIRPLANE AND STOPPED THE DESCENT 500 FEET BELOW ASSIGNED ALTITUDE. SPEED BRAKE EXTENSION INCREASES ROLL RATE. AUTOPILOT USE IN SEVERE TURBULENCE IS RECOMMENDED ONLY IN THE PITCH-HOLD MODE.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

THE PILOT-IN-COMMAND'S INADEQUATE WEATHER EVALUATION. FACTORS IN THE INCIDENT WERE THE WEATHER AND ARTCC'S FAILURE TO ISSUE A WEATHER ADVISORY.

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