A B757-200 ACFT REQUIRED AN AIR TURNBACK AFTER FLIGHT CREW NOTICED AN AIR/GROUND DISAGREE MESSAGE. IMPROPER TOOLING (RAZOR BLADES) WERE NOT REMOVED FROM THE LEFT/RIGHT MAIN LNDG GEAR AIR/GROUND PROXIMITY SENSORS.

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ON THE DAY IN QUESTION; MR Y; A QUALITY CTL INSPECTOR; AND MR X; A LEAD MECH; WERE PERFORMING AN ANTISKID/AUTOBRAKE SYS TEST ON A B757-200. THROUGHOUT THE TEST; MR X WAS UTILIZING RAZOR BLADES (COMPOSED FROM A FERROUS MATERIAL) TO ACTUATE THE L AND R MAIN LNDG GEAR AIR/GND SENSORS; THEREBY PROVIDING THE ACFT SYS WITH SIGNALS TO INDICATE THE ACFT WAS ON THE GND (IE; IN GND MODE). THE RAZOR BLADES HAD NO INDICATING MARKERS ON THEM (IE; REMOVE BEFORE FLT STREAMERS). IN REALITY THE ACFT WAS ON JACKS. THE INDIVIDUALS WERE PERFORMING THIS TEST BECAUSE IT WAS CALLED OUT FOR IN THE CUSTOMER TASK CARD AFTER A TRIPLE LNDG GEAR CHANGE. THE TASK CARD DID NOT STEP OUT THIS PROCESS; IT MERELY REFERRED THE TECHNICIAN TO A MAINT MANUAL REF. WITHIN THIS MAINT MANUAL REF THERE WAS NO SPECIFIC MANDATE AS TO WHETHER THE ACFT WAS TO BE POSITIONED ON THE GND OR WHETHER THE ACFT WAS TO BE SET UP FOR GND MODE. THROUGHOUT THE ANTISKID/AUTOBRAKE SYS TEST; BOTH THE TECHNICIAN (MR X) AND THE QUALITY CTL INSPECTOR (MR Y) RECEIVED ALL OF THE APPROPRIATE READINGS AND INDICATIONS CALLED OUT FOR IN THE MAINT MANUAL REF. HOWEVER; IN THE 'EQUIP' SECTION ON THE MANUAL; THERE IS A PROX SENSOR ACTUATOR/DE-ACTUATOR TOOLING SET CALLED OUT. AT THE TIME OF THE TEST; MR X VERIFIED THAT THE PROPER TOOLING SET WAS NOT AVAILABLE AT THE FACILITY AND UTILIZED RAZOR BLADES IN LIEU OF THE CALLED OUT TOOLING WITHOUT THE INSPECTOR'S KNOWLEDGE. IN ADDITION; MR X HAD NEVER SEEN THIS SET UTILIZED FOR THIS TEST AND WAS UNFAMILIAR WITH ITS COMPOSITION. MR X HAD PREVIOUSLY WITNESSED AND UTILIZED RAZOR BLADES FOR THIS TEST AND BELIEVED THEY WOULD PRODUCE THE SAME RESULTS AS THE CALLED OUT TOOLING. AFTER THE TEST WAS COMPLETE; THE APPROPRIATE PAPERWORK WAS SIGNED OFF AS BEING ACCOMPLISHED. THE NEXT DAY THE ACFT WAS DOWN-JACKED AND THE RAZOR BLADES WERE NOT REMOVED. SUPPLEMENTAL INFO FROM ACN 771685: THE ACFT DEPARTED THE MAINT FACILITY. AN AIR TURN-BACK OCCURRED SHORTLY AFTER DEP BECAUSE THE AIR CREW NOTICED AN AIR/GND DISAGREEMENT MESSAGE AND RETURNED TO THE MAINT FACILITY. AFTER ACFT RETURN; TROUBLESHOOTING THE PROB REVEALED THE CAUSE TO BE RAZOR BLADES ON THE L AND R MAIN LNDG GEAR AIR/GND PROX SENSORS. APPARENTLY THE RAZOR BLADES WERE PLACED ON THE L AND R MAIN LNDG GEAR AIR/GND PROX SENSORS IN LIEU OF THE PROX SENSOR ACTUATOR/DE-ACTUATOR TOOLING SET AS CALLED FOR IN THE MAINT MANUAL. I DID NOT WITNESS THE INSTALLATION OR REMOVAL OF THE ACTUATOR/DE-ACTUATOR SET USED DURING THE TESTING. IN ORDER TO VERIFY ALL STEPS ARE COMPLETE; THERE IS A CERTAIN AMOUNT OF TRUST REQUIRED BTWN THE INSPECTOR AND THE MECHS BECAUSE THE INSPECTOR CANNOT BE IN 4 PLACES AT ONCE. (COCKPIT; FORWARD CARGO BAY; AND EACH MAIN LNDG GEAR.) THEREFORE; I AUDIBLY VERIFIED INSTALLATION AND REMOVAL FROM THE MECHS PERFORMING THE STEPS BY USE OF THE 2-WAY RADIO. BECAUSE THE COM WAS OVER THE RADIO; I WAS UNAWARE OF THE USE OF RAZOR BLADES RATHER THAN REQUIRED TOOLING. I WAS IN THE FORWARD CARGO BAY WHERE THE AUTO SPD BRAKE CONTROLLER IS LOCATED IN ORDER TO VERIFY READINGS AND INDICATIONS MET THE VALUES CALLED OUT IN THE MAINT MANUAL. I PLACED MYSELF IN A CENTRAL LOCATION WHERE THE MOST READINGS COULD BE OBTAINED. FOLLOWING THIS INCIDENT; DETERMINATION OF ROOT CAUSE AND CORRECTIVE ACTION HAVE BEEN UNDERTAKEN. THE ROOT CAUSE IS THE USE OF INCORRECT TOOLING FOR THE JOB. THE CORRECTIVE ACTIONS BEING TAKEN INVOLVE A TECHNICAL PUB CHANGE REQUEST (TPCR) SUBMITTAL TO THE CUSTOMER TO IMPLEMENT THE FOLLOWING CHANGES: 1) UPDATE THE TASK CARD TO REFLECT A PROX SWITCH ACTUATOR/DE-ACTUATOR SET THAT IS AVAILABLE. 2) UPDATE THE METHODS CARDS FOR THE TASK CARD TO REFLECT A SWITCH ACTUATOR/DE-ACTUATOR SET WITHIN THE LIST OF REQUIRED TOOLING. 3) UPDATE THE TASK CARD SO THAT THE NUMBER OF SIGN-OFF STEPS CORRESPOND WITH THE ACCOMPLISHMENT STEPS. 4) UPDATE THE CUSTOMER GMM TO CLARIFY THE LEVEL OF INSPECTION REQUIRED FOR GND OPS CHKS FOLLOWING REPLACEMENT OF LNDG GEAR.