A320 CAPT REPORTS ANP VALUES HIGHER THAN APPROACH LIMITS DURING VOR DME 2 RWY 22 APPROACH AT MMPR.

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AIRBUS STANDARD RNP VALUE FOR NON-PRECISION APCH NAV APCHS IS 0.37. OUR PROCS REQUIRE US TO VERIFY THE 0.37 PRIOR TO XING THE FAF. OUR PROCS ALSO SPECIFY TO USE THE DEFAULT VALUE UNLESS THE CHART SPECIFICALLY TELLS US TO USE A DIFFERENT VALUE. HOWEVER; THE MANUAL ALSO SAYS THAT THE DEFAULT VALUE IS ONLY 0.37 WHEN THE FMGC HAS DME-DME UPDATING AVAILABLE. IF IT ONLY HAS VOR-DME UPDATING; THE DEFAULT VALUE IS 0.61. THIS IS OFTEN THE CASE IN PVR. IN FACT; I HAVE SEEN THE DEFAULT VALUE AS HIGH AS 0.78 ON THE FINAL APCH SEGMENT. IF WE ARE SUPPOSED TO BE USING 0.37 FOR THE APCH; THE CHART IN PVR NEEDS TO TELL US TO HARD-TUNE IT IN THE FMGC TO PREVENT AN AUTOMATIC INCREASE IN RNP VALUE. THE CURRENT SITUATION SETS THE CREW UP FOR A DOUBLING OF RNP INSIDE THE FAF WITH ABSOLUTELY NO NOTIFICATION WHATSOEVER; LEADING TO A XTRACK ERROR THAT IS POTENTIALLY DOUBLE BEFORE A NAV ACCURACY DOWNGRADE. THIS QUALIFIES AS VERY BAD WHEN CLOSE TO THE GND. AS AN ASIDE; THE RNP VALUE AUTOMATICALLY INCREASES AT PVR EVEN IN THE GPS-EQUIPPED AIRPLANES; WHICH SHOULDN'T HAPPEN. OBVIOUSLY; IF THE FMGC IS RECEIVING GPS UPDATES; THAT'S FAR MORE ACCURATE AND EITHER DME-DME OR VOR-DME UPDATING IS IRRELEVANT. PLEASE GIVE US SOME INSTRUCTIONS ON THE CHART TO HARD-TUNE AN RNP OF 0.37 FOR NON-PRECISION APCHS AT PVR. AS ANOTHER ASIDE; IN NON-GPS AIRPLANES THIS WILL ALSO CAUSE US TO ONLY DO CONSTANT DSCNT APCH PROCS BECAUSE WE'LL GET A NAV ACCURACY DOWNGRADE EVERY TIME.