M20R MOONEY PLT ACCEPTS AN RNAV GPS 4L APCH INTO BTR WITH THE VASI INOP. THE APCH PLATE INDICATES THE APCH IS NOT AUTH WITH THE VGSI OTS.

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DSNDING INTO BATON ROUGE; I WAS TOLD TO EXPECT THE RNAV/GPS 4 APCH INTO BATON ROUGE. I PULLED OUT THE APCH PLATE AND BRIEFED THE APCH. THE BRIEFING PROCESS WAS A LITTLE CHALLENGING SINCE I HADN'T REVIEWED A PLATE OF AN APCH THAT HAD VNAV SO I HAD TO SEARCH FOR MY MINIMUMS SINCE I DIDN'T HAVE VNAV. WHEN I GOT TO THE CHART NOTES; I NOTICED THAT THE APCH SAID 'N/A AT NIGHT WITH VGSI OTS.' I ASSUME THAT THE VGSI REFERS TO THE VASI WHICH WAS INDEED OTS; BUT AT THE TIME; I ASSUMED THAT ATC WOULDN'T BE CLRING ME FOR AN APCH IF THE REQUIRED COMPONENTS WERE OTS. SO; I WAS CLRED FOR THE APCH AND ACCEPTED IT. I FLEW THE APCH WITHOUT EVENT. BUT AS I WAS DSNDING WITH VISUAL CONTACT; I HEARD THE NEXT ACFT; AN RJ CHK ON THE FREQ. HE QUESTIONED THE TWR ABOUT THE NOTE. THE TWR CTLR DIDN'T SEEM TO BE AWARE OF IT; BUT WHEN HE PULLED OUT HIS PLATE; HE SAW THE NOTE AS WELL AND SAID HE DIDN'T KNOW WHAT IT MEANT; BUT IT DID SEEM TO PROHIBIT THE APCH AT NIGHT WITH THE VGSI OTS. THE RJ SPENT SOME TIME HOLDING WHILE THE TWR CTLR AND THE RJ PLT TRIED TO FIGURE OUT WHAT TO DO.