What was found
LANDING GEAR NOT UP AND LOCKED MSG ON ECAM AFTER TAKEOFF. FOLLOWED ECAM PROCEDURE TO REMAIN BELOW 220 KTS LOWERED & RAISED MLG LEVER THEN RETRACTED NORMALLY. FIRST TIME IT SEEMED THE WHEELS WERE UP BUT DOORS WERE OPEN. DUE TO NLG PROX SENSOR (24GA) FAULT REPLACED SENSOR PER A319 AMM 32-31 WITH FWD CARGO PROX SENSOR (30WV) IAW AMM 52-71. LGCIU TESTS PASS. IAW AMM 32-31-73-400-005-A STEP 4.F. OK TO DEFER INPSECTION OF 24GA FOR 15 FLT CYCLES OR 36 FLT HOURS (THE ONE THAT OCCURS FIRST). ACFT OK FOR SVC. BITE CHECK FAULTED SENSOR 24GA AGAIN. FOUND HYD FLUID CONTAMINATION AT BACKSHELL TO C/P. CLEANED SAME. RESISTANCE AND INDUCTANCE CHECKS GOOD IAW AMM 32-31. SEE MD LOG 1879325. (LP: 7901750, AIRCRAFT WAS GROUNDED)