Maintenance Airframe; Maintenance Powerplant
Situational Awareness; Distraction; Workload; Communication Breakdown
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Incorrect / Not Installed / Unavailable Part; Human Factors; Aircraft
I was prepping the aircraft for a Borescope Inspection of the left engine. I pulled the Engine Start Circuit Breakers (C/B) as per the Aircraft Maintenance Manual (AMM) to make the aircraft safe prior to performing the maintenance task; but forgot to collar the Circuit Breakers. I went to the cockpit to check the temperature of the left engine from the EICAS. I pulled the Breakers (C/Bs) as required by the AMM for safetying the engine for maintenance; but then got involved in removing the cowlings; shifting equipment and cooling the engine to below required minimum temperatures to enable the borescope to occur. I did not return to the cockpit to attach maintenance 'Do Not Close' C/B collars as I should have. The only response is follow procedures as outlined in the AMM. The task in the AMM states to pull the required Circuit Breakers/install safety collars.
Mechanic was informed he failed to collar the Left Engine Start Circuit Breakers (C/B) he had previously pulled while prepping an EMB-145 aircraft for a Boroscope Inspection.