Commercial Fixed Wing
Maintenance Airframe; Maintenance Powerplant
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Human Factors; Procedure
I was working line maintenance and the aircraft was just in the early stages of right engine change. Mechanics were putting the new engine under wing when I informed them that we needed to check the run on torque of the barrel nuts first. We found one bad and had to change it; then I was not needed until they were close to full up with the engine. So mechanics torqued aft engine mount bolts and then moved to forward mount. I stood out by the C-duct since two mechanics were under the C-ducts to accomplish the torques.Just got complacent; normally the new bolts are always used and checked for the run on torques. Then they have the anti-seize applied along with washer; sitting there ready.The aft mount bolts were put on first and they had the washers; but two mechanics did the aft and two other mechanics did the front. Again; just got complacent after aft mount bolts installed correctly and didn't double check for washers on the front mount installation.
A Maintenance Inspector reported that the front engine mounts did not have washers installed.