B777-200
Maintenance Airframe; Maintenance Powerplant
Communication Breakdown
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Procedure; Human Factors
While performing the Remove/Replace (R/R) of APU Battery during P-45 Check in ZZZ; discovered at the P-49 Panel C/B A-4 RAT AUTO/MAN CTRL deactivated with a lock out tag device. The P-49 Access panel was secured closed and cargo tape had to be removed to permit access for the scheduled battery change.The information attached to the lock out tag was not relevant to the operation in ZZZ. Pictures were taken and sent to Management for review. The root cause to this event is outside of my area of responsibility. I cannot answer why it occurred as we were not the responsible party.[Notified] Management detailing the location and the event. We performed a verification for other lock out tags associated with the RAT System. There were no other tags discovered. There were no visual related EICAS Status Messages and a review of the Maintenance Access Terminal (MAT) confirmed no associated maintenance messages. The aircraft was returned to service after a successful operational check of the RAT Auto Deploy System.I believe there are checks and balances in place to prevent occurrences like this from happening as long as we have procedural compliance. One suggestion would be a RAT drop on the Test Flight Phase of C-Checks. Maintenance Manager. During Phase Check Maintenance. RAT AUTO DEPLOY System.
Reporter stated the RAT would not have deployed in an emergency due to the AUTO/MAN CTRL switch was electrically deactivated with the C/B pulled and locked out at the P-49 Panel in the Aft Cargo pit sidewall. The cargo tape was applied around the P-49 Panel access door as part of the Cargo Smoke containment requirements.  No other information at this time as to who; or what; contributed to the RAT C/B lock-out not being removed.
A Maintenance Manager reports finding Circuit Breaker (C/B) A-4 for the RAT AUTO/MAN CTRL deactivated at the P-49 Panel with a lock out tag device installed during a Remove/Replacement (R/R) of the APU battery in the Aft Cargo pit. The B777-200 aircraft was in for a Maintenance Phase Check.