ACFT EQUIP PROBLEM FMS HSI. HOLDING PATTERN DISAPPEARED; POSSIBLE HOLDING PATTERN VIOLATION.

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ACR X ARRIVING AT GATWICK ON THE WLO1A ARR AFTER AN UNEVENTFUL N ATLANTIC NIGHT XING. APCHING SOUTHAMPTON; OUR WDB WAS GIVEN DELAYING VECTORS WHICH PLACED US S OF THE STAR BTWN R1 AND GOODWOOD VOR. WE ANTICIPATED POSSIBLE HOLDING AT WILLO BASED ON TFC AHEAD OF US. I WAS FLYING THE AIRPLANE AS FO. THE APCH CTLR CLRED US DIRECT TO WILLO -- NOTHING FURTHER WAS SAID. ANTICIPATING HOLDING; I ASKED THE CAPT TO REQUEST DIRECT HOLLY IF HOLDING WAS EXPECTED; MAKING A MUCH SIMPLER HOLDING ENTRY. HE DECLINED TO QUESTION THE APCH CTLR; SO I ENTERED 'DIRECT WILLO' VIA THE FMC. WHEN 'DIRECT WILLO' WAS EXECUTED VIA THE FMC; THE HOLDING PATTERN PREVIOUSLY DEPICTED ON OUR HSI'S PARTIALLY DISAPPEARED; AND DURING THE MAD RUSH TO TYPE IN THE HOLDING PATTERN ON THE 'HOLD' PAGE; I HAND FLEW THE HOLDING ENTRY USING HDG SELECT. WE EXCEEDED -- POSSIBLY; THE LIMITS OF HOLDING AIRSPACE TO THE E DURING THE INITIAL ENTRY; PROMPTING A REQUEST FOR THE CAPT TO TELEPHONE THE ATC WATCH SUPVR UPON LNDG. CONTINUED APCH AND LNDG UNEVENTFUL. THE ATC WATCH SUPVR QUESTIONED OUR UNDERSTANDING OF THE 'DIRECT WILLO' CLRNC; AND; IN FACT; CONFIRMED THAT THE CTLR ON DUTY HAD MEANT FOR US TO FLY DIRECT HOLLY; BUT HAD TOLD US THE INCORRECT FIX. WHEN IN DOUBT -- ASK -- AND ALWAYS BE READY TO TREAT THESE AUTOMATED COCKPITS LIKE AN OLD GENERATION AIRPLANE.