What was found
THE PIC WAS PILOT FLYING, ON APPROACH INTO 21L IN DTW AT ABOUT 165 KNOTS, CALLED FOR FLAPS 30, IMMEDIATELY RECEIVED A FLAPS FAIL CAUTION MESSAGE, FUEL WAS AT 2400 LBS, DECIDED IT WAS MORE SAFE AND PRUDENT TO LAND RIGHT AWAY AND NOT GO-AROUND. ADVISED F/O TO SET VREF SPEED FOR FLAPS 30 LANDING AND CHECK LANDING DISTANCE REQUIRED, LONG RUNWAY IN DTW AND LANDED.