ACR LGT FLYING A BAY VISUAL INTO SEA OVERSHOT LOC AND DSNDED BELOW RECOMMENDED ALT TO STAY VISUAL.

Date: 1991-12 · Aircraft: A321 · Phase: takeoff

Synopsis

ACR LGT FLYING A BAY VISUAL INTO SEA OVERSHOT LOC AND DSNDED BELOW RECOMMENDED ALT TO STAY VISUAL.

Narrative

WHILE RECEIVING VECTORS FOR THE ILS 16R AT SEA; THE PNF (CAPT) ASKED FOR PERMISSION TO FLY THE BAY APCH TO 16R. PNF HAD NOT FLOWN INTO SEA IN 3+ YEARS AND WAS UNFAMILIAR WITH THE PROC. THE PNF WAS IN THE PROCESS OF COMPLETING THE APCH CHKLIST WHEN CLRNC FOR THE BAY APCH WAS GIVEN. THE CHKLIST WAS INTERRUPTED LEAVING AN INCORRECT INBOUND COURSE SET IN THE ILS FRONT COURSE WINDOW. ON THIS ACFT THIS WILL RESULT IN AN IMPROPER CAPTURE OF THE LOC WHICH OCCURRED IN THIS CASE. BOTH PLTS IMMEDIATELY DETECTED THE ACFT ROLLING OPPOSITE OF WHAT WAS REQUIRED FOR LOC TRACKING. PF INCORRECTLY ATTEMPTED TO REVERSE HDG TO ALIGN ACFT WITH LOC. ONCE LOC IS CAPTURED ON THIS TYPE ACFT; OTHER ROLL MODES ARE INHIBITED. PF NOW DISCONNECTED AUTOPLT AND MANUALLY FLEW ACFT BACK ONTO LOC. DUE TO 25 KT QUARTERING TAILWIND AT 2000 FT LOC WAS OVERSHOT APPROX 1 MI. CLOUD LAYER AT 17000 MSL FORCED ACFT TO REMAIN VFR FOR THIS PROC. THIS PUT ACFT BELOW GS UNTIL 800 AGL. CAUSAL TO THIS EPISODE WAS DUE TO PNF ACCEPTING VISUAL APCH PROC UNDER MARGINAL CONDITIONS; AND THE DESIGN OF THE AUTOPLT/FLT DIRECTOR APCH MODE. AT MIN THE SELECTION OF ANOTHER ROLL MODE SHOULD DECOUPLE THE ACFT FROM THE LOC (HDG SELECT OR HOLD) AND SELECTION OF ANOTHER PITCH MODE SHOULD ALLOW FOR DECOUPLING FROM THE GS. PNF WAS ON INITIAL OPERATING EXPERIENCE AND COMING OFF AN MLG WHERE THE ABOVE TECHNIQUE IS AVAILABLE TO EXIT THE APCH MODE. DISTR FROM APCH CHKLIST COMPLETION WAS ALSO A PRIMARY CAUSE IN THIS INCIDENT.

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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.