What was found
CREW REPORTED ON APPROACH IN YOW (ON FLIGHT 4089) THEY SELECETED FLAPS FROM 0 - 20 GEDRESS AND RECEIVED HALF SPEED. CREW THEN SELECTED FLAPS FROM 20-30 DEGREES AND RECEIVED A FLAPS FAIL MESSAGE WITH FLAPS STOPPING AT 20 DEGRESS. THE CREW RAN THE QRH AND LANDED THE AIRCRAFT. PERFORMED RESET PROCEDURES AND MEL'D 27-50-00. PERFORMED RESET PROCEDURES AND MEL'D 27-50-00. PERFORMED TROUBLESHOOTING PER BOMBARDIER FIM REV 43 IAW AD 2009-06-12 PARAGRAPH H6I, AMOC DATED APRIL 19 2012 AND PA AD 27-052H. REPLACED LT NR 1 ACT, NR 5 FLEX SHAFT, RT NR 1 & 3 ACT.