NTSB Identification: MIA88IA167A.
The docket is stored on NTSB microfiche number 37978.
Incident occurred Tuesday, May 10, 1988 in CHICAGO, IL
Probable Cause Approval Date: 07/18/1990
Aircraft: BEECH 200, registration: N981LL
Injuries: 95 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.
MIDWAY FLT 172 (MCDONNELL DOUGLAS DC-9, N1065T) WAS ON AN IFR DEPARTURE FROM CHICAGO MIDWAY ARPT AT THE SAME TIME THAT BEECH 200, N981LL, WAS ON AN IFR ARRIVAL FOR A VISUAL APCH TO MERRILL C MEIGS ARPT, ALTHOUGH BOTH WERE IN VMC. PREVIOUSLY, O'HARE TRACON HAD RESTRICTED EASTERLY DEPARTURES FROM MIDWAY TO NOT LESS THAN 20 MI IN-TRAIL. SUBSEQUENTLY, THE HANDOFF CONTROLLER (CTLR) AT TRACON INSTRUCTED THE CTLRS AT MIDWAY TOWER TO 'CANCEL THE RESTRICTION,' MEANING TO CANCEL THE IN-TRAIL RESTRICTION. HOWEVER, THE CTLRS AT MIDWAY THOUGHT THIS WAS IN REFERENCE TO A CLIMB RESTRICTION ON THE CANAL THREE SID WHICH FLT 172 WAS USING. SUBSEQUENTLY, FLT 172 & N981LL CONVERGED AS FLT 172 WAS CLIMBING TO 3000 FT & N981LL WAS DSCNDG TO 2000 FT. RADAR DATA SHOWED THE ACFT PASSED EACH OTHER WITH LESS THAN THE REQUIRED VERTICAL & HORIZONTAL SEPN.
The National Transportation Safety Board determines the probable cause(s) of this incident to be:COMMUNICATIONS..IMPROPER..ATC PERSONNEL(DEP/APCH)
The National Transportation Safety Board determines the probable cause(s) of this incident to be:INSTRUCTIONS,WRITTEN/VERBAL..NOT UNDERSTOOD..ATC PERSONNEL(LCL/GND/CLNC)
The National Transportation Safety Board determines the probable cause(s) of this incident to be:RADAR SEPARATION..INADEQUATE
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