A B737-400 DURING A HORIZ STABILIZER CTR SECTION HINGE PIN INSPECTION; AN FAA SAFETY INSPECTOR QUESTIONED WHY THE STABILIZER TRIM WHEEL LOCKOUT WAS NOT INSTALLED.

Narrative

FIRST TIME COMPLETING TASK FROM START TO FINISH. ONE OTHER TIME DOING THIS TASK WAS THE INSTALLATION ONLY. MECHS INVOLVED WERE MYSELF AND MR X. I WAS IN CHARGE OF SETTING UP THE COCKPIT TO ACCOMPLISH THE TASK. DURING ACCOMPLISHING THE TASK FOR INSPECTING THE HORIZ STABILIZER CTR SECTION HINGE PINS; WHICH REQUIRED THE REMOVAL OF THE PIN; WE WERE APCHED BY THE FAA AND AS WHY THE STABILIZER TRIM LOCK WAS NOT INSTALLED. I INFORMED THE FAA INSPECTOR THAT BY FOLLOWING THE PROC IN THE MAINT MANUAL; THAT THE LOCK DID NOT FIT ON THE TRIM WHEEL. I HAD SET THE STABILIZER TO THE MAX LEADING EDGE DOWN POS; TO GAIN ACCESS TO THE PINS; USING THE ELECTRICAL TRIM SWITCHES ON THE PLT'S CTL COLUMN. THE TRIM LOCK WAS NEARBY THE TRIM WHEEL BUT NOT INSTALLED. I HAD PULLED AND 'DANGER' TAGGED THE CIRCUIT BREAKERS FOR ACTUATION OF THE STABILIZER TRIM MOTOR AND FELT THAT IT WAS SAFE TO CONTINUE WITH THE TASK. WE WERE THE ONLY ONES WORKING ON THE ACFT AT THE TIME AND FELT THAT NO ONE WOULD BE ACTUATING THE CTLS. THE TASK CARD DOES NOT ADDRESS NOT HAVING INSTALLING THE STABILIZER TRIM LOCK.