GIII FLC ASSUME ZOA DIRECTIVE CLRNC TO ARPT IS ALSO AUTH FOR VISUAL APCH; DUE TO PROX TO ARPT.

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POSSIBLE ALTDEV OF 800 FT; AT 14000 FT MSL ON ARR TO TVL FROM THE SE. ON ARR; WE WERE NWBOUND AT 14000 FT WHEN WE CALLED THE ARPT IN SIGHT. THE CTLR ADVISED THAT IFR TFC WAS DEPARTING TOWARDS SQUAW VALLEY VOR. WE WERE TOLD TO GO DIRECT TO SQUAW VALLEY VOR. APPROX 10 MI NW OF TVL; WE WERE TOLD TO GO DIRECT TO THE ARPT; AND INTERPED THIS AS A VISUAL DUE TO THE LARGE AMOUNT OF ALT WE NEEDED TO LOSE (ABOUT 8000 FT). WHILE TURNING TOWARDS THE ARPT AT AN ALT OF 13200 FT; ZOA ASKED OUR ALT. WE TOLD THEM AND THEY TOLD US WE NEEDED TO MAINTAIN 14000 FT. WE CLBED BACK UP AND TOLD THEM WE NEEDED A TURN TOWARDS THE N TO PLAN THE DSCNT. THEY GAVE US A VECTOR AND CLRED US FOR THE VISUAL AND TOLD US TO CONTACT TVL TWR. APCH AND LNDG WAS UNEVENTFUL. COM ERRORS AND INTERP WERE KEY FACTORS ON BOTH SIDES. ZOA'S INSTRUCTIONS WERE NOT CLR; AND WE SHOULD HAVE ASKED FOR CLARIFICATION. AS THE CREW; WE INTERPED THE TURN TOWARDS THE ARPT AS 'CLRED FOR THE VISUAL' DUE TO HAVING ALREADY CALLED IT IN SIGHT; PROCEEDING DIRECT AND NEEDING TO LOSE 8000 FT OF ALT IN A RELATIVELY SHORT DISTANCE; AND TFC NOT BEING A FACTOR (NOTHING ON TCASII). ATC NEEDS TO GIVE PRACTICAL AND REALISTIC INSTRUCTIONS AND AS THE PLTS WE NEED TO QUESTION AND CLARIFY WHEN INSTRUCTIONS ARE VAGUE. THE UNUSUAL ARPT ENVIRONMENT OF TVL ALSO IS A CONTRIBUTING FACTOR.