A CANADAIR CL65 ON LNDG THE R ENG UPPER ACCESS COWLING DEPARTED THE ACFT.

Narrative

I WAS ASSISTING A CO-WORKER WITH A #2 ENG THROTTLE PROB. WHILE STANDING ON TOP OF THE ENG PYLON; I WAS SECURING CABLES ON THE THROTTLE GEARBOX. I STEPPED AWAY FOR A BRIEF MOMENT TO HELP MY CO-WORKER WITH THE UPPER ACCESS COWL. ONCE WE GOT THE UPPER ACCESS COWL BACK ONTO THE ENG I WENT BACK TO FINISH WORKING ON THE THROTTLE GEARBOX WHILE MY CO-WORKER SECURED AS MANY ACCESS COWL FASTENERS AS HE COULD REACH. AFTER I COMPLETED WORKING ON THE THROTTLE GEARBOX I STEPPED DOWN FROM THE ENG PYLON AND WAITED FOR THE RII INSPECTION OF THE THROTTLE GEARBOX TO BE COMPLETED. WE THEN CLOSED UP THE CORE COWL. I WAS IN SUCH A RUSH TO COMPLETE THE WORK THAT I DON'T RECALL WHETHER ALL OF THE FASTENERS ON THE UPPER ACCESS COWL WERE FASTENED. WHEN THE ACFT ARRIVED IN ZZZ THE UPPER ACCESS COWL DEPARTED THE ACFT ON THE RWY. NO DAMAGE WAS SUSTAINED TO THE ACFT; HOWEVER; THE ACCESS COWL DID NEED TO BE REPLACED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE COWLING FASTENERS WERE THE PUSH IN AND TURN TYPE AND BELIEVES THE FASTENERS WERE ALL LOCKED. THE RPTR SAID THE JOB WAS DONE AT THE TERMINAL WITH OPERATING ACFT ALL AROUND AND MGMNT WAS REALLY PUTTING ON THE PRESSURE TO FINISH. THE RPTR STATED THE FAA HAS SENT A LETTER OF INVESTIGATION.