What was found
AFTER TAKEOFF BOTH DME'S VARIABLE +/- 20NM, EN ROUTE CONDITION WORSENED TO 100NM AT TIMES. PATCH WITH SAMC & C/B RESET DIDN'T RESOLVE CONDITION. CHECKED DME INTEROGATORS, BITE CHECK OK AND DME DISTANCE TO STATIONS ARE NORMAL. CHECKED AND RESET FMGC COMPUTERS, ALL TEST NORMAL. ACP PHC 1, 2 & 3 TEST. HAD CLASS 3 FAULTS FOR ALL PROBES, TAT, AOA ON BOTH PHC 1& 2. CYCLED PH C CB'S AND RETESTED, ALL OK NOW. LGCUI 1& 2 TESTED NORMAL. ILS TESTED OK. COULD NOT DUPLICATE ANY NAV FAULTS. A/C HAS NOT REPEATED SINCE THIS INCIDENT.