Narrative:

The airplane arrived at the maintenance base/repair station around XA00 from scheduled cargo and on-demand passenger flight. PIC performed postflt walkaround inspection and noticed r-hand main landing gear inboard multiple-disc brakes appeared to be worn to limits. PIC wrote this on a company discrepancy sheet and turned it in to the chief inspector's desk. I work alone during the evening/late shift and I am tasked with performing maintenance on this and other aircraft so that they may be dispatched each morning for flight. I picked up this discrepancy sheet and consulted the fairchild SA227DC maintenance manual (on computer) for the svcable limits of the multiple disc brakes. I had previously received company training on inspection of this type of brake for wear svcability. I was incorrectly trained on the method for this inspection. I was shown that it is a diminishing dimension that is to be detected. The correct method is to inspect for an increasing dimension. I did consult the maintenance manual for this inspection and interpreted it in the same (incorrect) manner by which I was trained. I believe that I perceived the brake dimensional inspection from the maintenance manual to be a diminishing dimension because I had already been trained incorrectly to perform the inspection this way. I incorrectly inspected the r-hand inboard brake and made a false airworthiness determination. I released the aircraft for return to service with my signature and the repair station certificate number. My supervisors in maintenance department discovered that I made an incorrect airworthiness determination the next day after the airplane in question had been dispatched for flight. I received further (correct) training about the aircraft's braking system. The airplane in question arrived the evening after its dispatch to the company maintenance base. The brakes in question were replaced at this time.

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Original NASA ASRS Text

Title: AN SA227 WAS RELEASED FOR SVC WITH A R INBOARD BRAKE WORN TO LIMITS. INSPECTOR THAT CHKED BRAKE 'OK FOR SVC' USED WRONG LIMITS TO APPROVE BRAKE.

Narrative: THE AIRPLANE ARRIVED AT THE MAINT BASE/REPAIR STATION AROUND XA00 FROM SCHEDULED CARGO AND ON-DEMAND PAX FLT. PIC PERFORMED POSTFLT WALKAROUND INSPECTION AND NOTICED R-HAND MAIN LNDG GEAR INBOARD MULTIPLE-DISC BRAKES APPEARED TO BE WORN TO LIMITS. PIC WROTE THIS ON A COMPANY DISCREPANCY SHEET AND TURNED IT IN TO THE CHIEF INSPECTOR'S DESK. I WORK ALONE DURING THE EVENING/LATE SHIFT AND I AM TASKED WITH PERFORMING MAINT ON THIS AND OTHER ACFT SO THAT THEY MAY BE DISPATCHED EACH MORNING FOR FLT. I PICKED UP THIS DISCREPANCY SHEET AND CONSULTED THE FAIRCHILD SA227DC MAINT MANUAL (ON COMPUTER) FOR THE SVCABLE LIMITS OF THE MULTIPLE DISC BRAKES. I HAD PREVIOUSLY RECEIVED COMPANY TRAINING ON INSPECTION OF THIS TYPE OF BRAKE FOR WEAR SVCABILITY. I WAS INCORRECTLY TRAINED ON THE METHOD FOR THIS INSPECTION. I WAS SHOWN THAT IT IS A DIMINISHING DIMENSION THAT IS TO BE DETECTED. THE CORRECT METHOD IS TO INSPECT FOR AN INCREASING DIMENSION. I DID CONSULT THE MAINT MANUAL FOR THIS INSPECTION AND INTERPED IT IN THE SAME (INCORRECT) MANNER BY WHICH I WAS TRAINED. I BELIEVE THAT I PERCEIVED THE BRAKE DIMENSIONAL INSPECTION FROM THE MAINT MANUAL TO BE A DIMINISHING DIMENSION BECAUSE I HAD ALREADY BEEN TRAINED INCORRECTLY TO PERFORM THE INSPECTION THIS WAY. I INCORRECTLY INSPECTED THE R-HAND INBOARD BRAKE AND MADE A FALSE AIRWORTHINESS DETERMINATION. I RELEASED THE ACFT FOR RETURN TO SVC WITH MY SIGNATURE AND THE REPAIR STATION CERTIFICATE NUMBER. MY SUPVRS IN MAINT DEPT DISCOVERED THAT I MADE AN INCORRECT AIRWORTHINESS DETERMINATION THE NEXT DAY AFTER THE AIRPLANE IN QUESTION HAD BEEN DISPATCHED FOR FLT. I RECEIVED FURTHER (CORRECT) TRAINING ABOUT THE ACFT'S BRAKING SYS. THE AIRPLANE IN QUESTION ARRIVED THE EVENING AFTER ITS DISPATCH TO THE COMPANY MAINT BASE. THE BRAKES IN QUESTION WERE REPLACED AT THIS TIME.

Data retrieved from NASA's ASRS site as of January 2009 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.