Narrative:

Aircraft had identical problem of flaps not extending and was ferried to home maintenance base earlier in the day. This was first flight after corrective action and maintenance signoff. Maintenance should be sure that problem is corrected before releasing aircraft for service, especially since there is a current airworthiness directive for flap operation on this model aircraft. Callback conversation with reporter revealed the following information: the reporter stated the aircraft was flown on a maintenance ferry into the maintenance facility for a positive fix on the trailing edge flaps. The reporter said the aircraft was returned to service after maintenance and on the first revenue flight the trailing edge flaps failed to extend on landing. The reporter stated this flap system has an airworthiness directive requiring continuous inspection prior to and after flight due to hydraulic actuator bypassing. The reporter 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 position which twists or warps the flap shutting the system off. The reporter said there is no sensing or warning this condition is occurring until the flaps fail. The reporter stated the airworthiness directive requires an inspection before flight by extending the flaps to 23 units and checking the flaps visually for twisting, looking for a concave upper surface and checking the gap between the inboard and outboard flaps. The reporter said the flaps are extended to 20 units when parked on a gate during the day and left in this position until the aircraft is flown. The reporter stated the above visual check was made by the crew prior to flight and nothing unusual noted.

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Original NASA ASRS Text

Title: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.