AN MD88 RETURNED TO THE FIELD IMMEDIATELY AFTER TKOF DUE TO UNABLE TO PRESSURIZE THE ACFT CAUSED BY A NOSEWHEEL WELL PANEL NOT INSTALLED AFTER MAINT.

Narrative

ON THE NIGHT OF JAN/XA/99; I WAS WORKING AN OPEN LOGSHEET ITEM ON AN MD88 ATTITUDE AND HDG REF SYS UNIT. (AHRS). A MECH HAD PREVIOUSLY SIGNED FOR THE INSTALLATION OF THE AHRS UNIT AND NOTED THAT AN OP CHK NEEDED TO BE PERFORMED. I COPIED THE APPROPRIATE MAINT MANUAL REF FOR THE ADJUSTMENT/TEST OF THE AHRS UNIT AND PERFORMED THE STEPS NECESSARY TO ENSURE THAT THE UNIT WAS OPERATIONAL AND FIT FOR SVC. THE TEST PASSED AND ALL CIRCUIT BREAKERS WERE RETURNED TO THEIR NORMAL CONFIGN. THE ACFT WAS RETURNED TO SVC AND SCHEDULED FOR A FLT THE FOLLOWING MORNING. THE ACFT PERFORMED A NORMAL TKOF; HOWEVER; THE ACFT FAILED TO PRESSURIZE AND THE PLT PERFORMED AN AIR TURN-BACK. MAINT PERSONNEL DISCOVERED THE ACCESS PANEL FOR THE AHRS UNIT IN THE NOSEWHEEL WELL OF THE ACFT HAD NOT BEEN INSTALLED. THE ACCESS PANEL WAS INSTALLED AND THE ACFT AGAIN PLACED INTO SVC WITH NO FURTHER INTERRUPTIONS NOTED DUE TO THIS PROB. IT WAS MY PERCEPTION THAT THE MECH THAT SIGNED FOR THE INSTALLATION OF THE AHRS UNIT HAD ALSO INSTALLED THE ACCESS PANEL THAT HAD BEEN REMOVED TO GAIN ACCESS. THE INSTALLING MECH NOTED IN THE LOG THAT AN OP CHK NEEDED TO BE PERFORMED AND WROTE NOTHING OF THE NEED TO INSTALL THE ACCESS PANEL.