Air carrier Technician reported during a rigging procedure on the B-787 spoiler power control unit; the leading-edge slats extended and impacted both engine inboard thrust reverser doors.

Narrative

I was involved in an incident on Aircraft X that caused damage to the airplane; due to a mistake I made during the rigging procedure of a spoiler power control unit. Myself and another Company technician were tasked with finishing the installation of the #1 spoiler power control unit for Aircraft X; a Company airlines B787. We picked up the remaining workload from the midnight shift which included doing leak checks on both engines so both engine fan cowls and thrust reverser doors were opened. During the rigging procedure for the power control unit; I was in the flight deck operating the display while my coworker was completing the steps required out at the spoiler. We were in communication with each other and we were completing the procedure which involved placing a rigging block in position between the flap and the spoiler and then removing it while stepping through the different pages that appeared on the display. The damage occurred when I pushed 'CONTINUE' on a page that directed me to ensure the thrust reverser doors were closed before proceeding. I pushed 'CONTINUE' because I thought the slats system was deactivated along with the thrust reversers. The next screen said to pressurize hydraulics and move the flap handle to position 30; at which point the leading edge slats deployed and impacted both engines inboard thrust reverser doors. I mistakenly believed that both thrust reversers and the leading edge slats were deactivated and that only the flaps would move when I pushed 'CONTINUE'. I was notified what had happened and I turned off the hydraulics and exited the test screens on the display; next meeting up with my coworkers and my Lead Mechanic to determine together how we should proceed from that point. The reason I thought only the flaps could move was I saw from the logbook entries that the thrust reversers were deactivated for the check; which I expected as the engines were opened. I knew that deactivating the slats system was part of that same procedure so I assumed that this system was also deactivated. I also saw that a considerable number of virtual circuit breakers were in the opened state. I'm not sure but I believe more than ten were opened total; but I did not verify one by one which breaker deactivated which system. I have not deactivated the thrust reversers or the slats on the B787 personally; so I was not familiar with the procedure or what individual steps were taken during the procedure. To add further context; I have worked for Company for almost 8 years; and over 7 years of that time I was in a work area where I mostly worked with other aircraft. I occasionally worked on various wide body aircraft; but this work was normally routine jobs such as service checks and navigational database updates; or similar work. On the B737; deactivating the slats system is part of the procedure for deactivating the thrust reversers; and this was why I expected both systems to be disabled and unable to move with hydraulic power. I am not experienced with replacing flight control components or doing jobs that require opening the fan cowls and thrust reverser doors on the B787; so I was not familiar with these procedures. I'm confident I would not have made this error if I was doing this job on a familiar aircraft; as I would have clearly seen the systems were not deactivated. I am new to the hangar work area and picking up aircraft that have been turned over from midnights; which at times includes finishing checks and correcting or completing work such as Aircraft Health Management or procedures. On this particular morning I was aware that most of Aircraft X's work was already completed; and that it had a flight scheduled for early afternoon; approximately XX or XX:30pm was what I understood at the time. Therefore my mindset was geared towards finishing the remaining work as efficiently and timely as possible; leading me to determine with the proper systems deactivated we could move the flaps and complete the spoiler power control unit rigging procedure. This was clearly not the case; so I believe that lack of knowledge and experience on the B787; combined with an attempt to complete too many job procedures simultaneously; led me to make an error during the spoiler power control unit rigging procedure that resulted in the damage sustained by Aircraft X.