A CANADAIR REGIONAL JET ON APCH AT 3000 FT WAS UNABLE TO EXTEND THE TRAILING EDGE FLAPS FOR LNDG. THIS WAS THE SECOND FLAP FAILURE ON THIS ACFT IN ONE DAY.

Narrative

ACFT HAD IDENTICAL PROB OF FLAPS NOT EXTENDING AND WAS FERRIED TO HOME MAINT BASE EARLIER IN THE DAY. THIS WAS FIRST FLT AFTER CORRECTIVE ACTION AND MAINT SIGNOFF. MAINT SHOULD BE SURE THAT PROB IS CORRECTED BEFORE RELEASING ACFT FOR SVC; ESPECIALLY SINCE THERE IS A CURRENT AIRWORTHINESS DIRECTIVE FOR FLAP OP ON THIS MODEL ACFT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS FLOWN ON A MAINT FERRY INTO THE MAINT FACILITY FOR A POSITIVE FIX ON THE TRAILING EDGE FLAPS. THE RPTR SAID THE ACFT WAS RETURNED TO SVC AFTER MAINT AND ON THE FIRST REVENUE FLT THE TRAILING EDGE FLAPS FAILED TO EXTEND ON LNDG. THE RPTR STATED THIS FLAP SYS HAS AN AIRWORTHINESS DIRECTIVE REQUIRING CONTINUOUS INSPECTION PRIOR TO AND AFTER FLT DUE TO HYD ACTUATOR BYPASSING. THE RPTR SAID THE BYPASSING ACTUATOR ALLOWS ONE ACTUATOR TO ATTEMPT TO DRIVE THE FLAP SEGMENT TO EXTEND WHILE THE OTHER BYPASSED ACTUATOR IS LOCKED IN THE RETRACT POS WHICH TWISTS OR WARPS THE FLAP SHUTTING THE SYS OFF. THE RPTR SAID THERE IS NO SENSING OR WARNING THIS CONDITION IS OCCURRING UNTIL THE FLAPS FAIL. THE RPTR STATED THE AIRWORTHINESS DIRECTIVE REQUIRES AN INSPECTION BEFORE FLT BY EXTENDING THE FLAPS TO 23 UNITS AND CHKING THE FLAPS VISUALLY FOR TWISTING; LOOKING FOR A CONCAVE UPPER SURFACE AND CHKING THE GAP BTWN THE INBOARD AND OUTBOARD FLAPS. THE RPTR SAID THE FLAPS ARE EXTENDED TO 20 UNITS WHEN PARKED ON A GATE DURING THE DAY AND LEFT IN THIS POS UNTIL THE ACFT IS FLOWN. THE RPTR STATED THE ABOVE VISUAL CHK WAS MADE BY THE CREW PRIOR TO FLT AND NOTHING UNUSUAL NOTED.