NTSB Identification: DEN87IA145B
Incident occurred Tuesday, June 02, 1987 in CASPER, WY
Probable Cause Approval Date: 10/17/1988
Aircraft: Boeing EC-135, registration: USAF
Injuries: 72 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.

BOEING 727 (NORTHWEST FLT 354) & USAF EC-135 (SLUM 51) WERE INVOLVED IN A NR COLLISION AT FL 330. THE MISHAP OCCURRED ASFLT 354 WAS ENE BND ON J-158 & SLUM 51 WAS FLYING ON A RADIAL-DISTANCE (R/D) FLT PLN, FLYING BTN R/D PTS SOUTH OF J-158.AS SLUM 51 APCHD ITS MOST WESTERN PT, THE CREW REQD A RGT TURN TO A R/D PT THAT WAS NOT THE NEXT LISTED PT ON THEIR FLT PLN. THE TRAINEE CTLR (T/C) DIDN'T REALIZE SLUM 51 WAS REQG A ROUTE CHG, BUT THOUGHT THE FLT WANTED TO TURN BACK EAST TOTHE NEXT FILED R/D PT WITH A RGT TURN (INSTEAD OF A L TURN AS PREVIOUSLY DONE). THE T/C REPLIED, 'UNABLE RGT TURN, MAKE A LEFT TURN.' THE INSTRUCTOR HEARD THE REQ, BUT THOUGHT THE T/C'S REPLY WAS DISAPPROVAL OF A ROUTE CHG. AS THE CTLRS TURNED THEIR ATTN TO OTR (HVY/COMPLEX) TRAFFIC, SLUM 51 CONTD A 270 DEG L TURN (TO NORTH) & CONVERGED WITH FLT 354. THE 9020 (PRIMARY) COMPUTER WAS INOP; THE DARC (BACKUP) COMPUTER HAD NO CAPABILITY OF DISPLAYING PROJECTED ROUTES OR PROVID-ING CONFLICT ALERT. NO FLOW CTL RESTRICTIONS WERE IN EFFECT TO RDC THE AMOUNT OF TRAFFIC.

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

RADIO COMMUNICATIONS..NOT UNDERSTOOD..ATC PERSONNEL(ARTCC)

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

ATC CLEARANCE..INACCURATE..ATC PERSONNEL(ARTCC)

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

IFR SEPARATION STANDARDS..NOT MAINTAINED


Contributing Factors

RADAR,EN ROUTE..FAILURE,PARTIAL



Contributing Factors

EXCESSIVE WORKLOAD (TASK OVERLOAD)..ATC PERSONNEL(ARTCC)


Contributing Factors

IMPROPER DECISION..FAA(OTHER/ORGANIZATION)



Contributing Factors

RADAR,CONFLICT ALERT..INOPERATIVE

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