Narrative:

On feb/xx/98, I was assigned to change the left hand main landing gear shimmy damper. On removal of the damper, it was discovered that the lower torque link was frozen (would not move without excessive force). Some time was spent attempting to loosen the link by lubing, exercising, etc, to no avail. The rest of my shift was spent in removal of the lower torque link. Next two shifts were used by our machinists to replace both the upper and lower torque links, link bushings and link pins. When I returned to work on feb/xy/98, I was assigned with 2 other mechanics to finish the reassembly of the left hand main landing gear strut (install bracketry, hydraulic lines, wiring, brakes, wheels, torque link damper, etc). During reassembly, a co-worker accidentally broke the inboard air/ground proximity sensor while tightening the cannon plug attached to it. I ordered a new one and proceeded to replace it in accordance with our torque link removal/replacement job card and the maintenance manual. We finished the rest of the reassembly of the left hand main landing gear, the logbook was filled out and signed off and the aircraft was returned to service on feb/xz/98. On the first flight after returning to service, the pilots got messages on the MFDU about air sensing problems and were only able to retract the landing gear using the override function. They declared an emergency and returned to field for an uneventful landing and returned to the gate. The aircraft was removed from service, and during a bite check of the proximity sense system, the replaced sensor was found to be out of adjustment. Actually, the sensor is non adjustable, and the sensor target was out of rig. The target was adjusted and the problem corrected with no further discrepancies. The job card, nor the maintenance manual made reference to do a bite test, which would have discovered the problem before flight. I am submitting a 'request for publication change' to add a more thorough check and test for the adjustment of the sensors on the job card. Callback conversation with reporter revealed the following information: the reporter stated that nothing in the maintenance manual or the job cards for the torque link replacement and landing gear ground sensor proximity sensor replacement requires a landing gear retraction test. The reporter said a test would have avoided this incident. The reporter stated the FAA has made no contact.

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Original NASA ASRS Text

Title: A FOKKER 100 AFTER TKOF RETURNED TO THE FIELD DUE TO NUMEROUS AIR SENSING MULTIPLE FUNCTIONAL DISPLAY UNIT FAULTS AND THE NECESSITY TO USE OVERRIDE TO RAISE THE LNDG GEAR CAUSED BY AN INCORRECT ADJUSTMENT OF THE L MAIN GEAR GND SENSOR.

Narrative: ON FEB/XX/98, I WAS ASSIGNED TO CHANGE THE L HAND MAIN LNDG GEAR SHIMMY DAMPER. ON REMOVAL OF THE DAMPER, IT WAS DISCOVERED THAT THE LOWER TORQUE LINK WAS FROZEN (WOULD NOT MOVE WITHOUT EXCESSIVE FORCE). SOME TIME WAS SPENT ATTEMPTING TO LOOSEN THE LINK BY LUBING, EXERCISING, ETC, TO NO AVAIL. THE REST OF MY SHIFT WAS SPENT IN REMOVAL OF THE LOWER TORQUE LINK. NEXT TWO SHIFTS WERE USED BY OUR MACHINISTS TO REPLACE BOTH THE UPPER AND LOWER TORQUE LINKS, LINK BUSHINGS AND LINK PINS. WHEN I RETURNED TO WORK ON FEB/XY/98, I WAS ASSIGNED WITH 2 OTHER MECHS TO FINISH THE REASSEMBLY OF THE L HAND MAIN LNDG GEAR STRUT (INSTALL BRACKETRY, HYD LINES, WIRING, BRAKES, WHEELS, TORQUE LINK DAMPER, ETC). DURING REASSEMBLY, A CO-WORKER ACCIDENTALLY BROKE THE INBOARD AIR/GND PROX SENSOR WHILE TIGHTENING THE CANNON PLUG ATTACHED TO IT. I ORDERED A NEW ONE AND PROCEEDED TO REPLACE IT IN ACCORDANCE WITH OUR TORQUE LINK REMOVAL/REPLACEMENT JOB CARD AND THE MAINT MANUAL. WE FINISHED THE REST OF THE REASSEMBLY OF THE L HAND MAIN LNDG GEAR, THE LOGBOOK WAS FILLED OUT AND SIGNED OFF AND THE ACFT WAS RETURNED TO SVC ON FEB/XZ/98. ON THE FIRST FLT AFTER RETURNING TO SVC, THE PLTS GOT MESSAGES ON THE MFDU ABOUT AIR SENSING PROBS AND WERE ONLY ABLE TO RETRACT THE LNDG GEAR USING THE OVERRIDE FUNCTION. THEY DECLARED AN EMER AND RETURNED TO FIELD FOR AN UNEVENTFUL LNDG AND RETURNED TO THE GATE. THE ACFT WAS REMOVED FROM SVC, AND DURING A BITE CHK OF THE PROX SENSE SYS, THE REPLACED SENSOR WAS FOUND TO BE OUT OF ADJUSTMENT. ACTUALLY, THE SENSOR IS NON ADJUSTABLE, AND THE SENSOR TARGET WAS OUT OF RIG. THE TARGET WAS ADJUSTED AND THE PROB CORRECTED WITH NO FURTHER DISCREPANCIES. THE JOB CARD, NOR THE MAINT MANUAL MADE REF TO DO A BITE TEST, WHICH WOULD HAVE DISCOVERED THE PROB BEFORE FLT. I AM SUBMITTING A 'REQUEST FOR PUB CHANGE' TO ADD A MORE THOROUGH CHK AND TEST FOR THE ADJUSTMENT OF THE SENSORS ON THE JOB CARD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT NOTHING IN THE MAINT MANUAL OR THE JOB CARDS FOR THE TORQUE LINK REPLACEMENT AND LNDG GEAR GND SENSOR PROX SENSOR REPLACEMENT REQUIRES A LNDG GEAR RETRACTION TEST. THE RPTR SAID A TEST WOULD HAVE AVOIDED THIS INCIDENT. THE RPTR STATED THE FAA HAS MADE NO CONTACT.

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.