B757 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 160; Flight Crew Total 207; Flight Crew Type 181
Communication Breakdown
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown
Human Factors
During pushback; I was starting the left engine and the airplane came to a stop. The ramp personnel said something inaudible; but it didn't sound like 'Set brakes.' I was focused on the rising EGT and leaned over to see if the parking brake was set (the EICAS message is inhibited during engine start); but in the dark cockpit I couldn't tell; and I was simultaneously watching the engine EGT approach it's highest point in the start just before cutout. The ramper shouted; 'You're rolling!' and the captain hit the brakes. We stopped instantly and the captain set the brake. I asked the captain if I should standby starting the second engine and he said yes. The captain asked the ramper if everyone was ok. The ramp personnel said everyone was fine; so we continued normally. In retrospect; I should have inquired verbally if the parking brake was set; rather than trying to confirm on my own. The captain later stated that the improper phraseology from the ground personnel in ZZZ contributed to the parking brake not being set.
B757 First Officer reported starting the left engine without verifying the brakes were set which caused an uncommanded aircraft movement.