Narrative:

Leaving the gate at bna we were expecting runway 20R for departure. Once we got to spot 4 we were assigned a quick release time and to expect runway 20C; a shorter taxi. There were about 4-5 aircraft that had pushed or were in the process of pushing; all departing runway 20C. We taxied via T4; crossing 31; and held short of S7 for a passing aircraft. The first officer had started entering in the new runway and sent for new takeoff data. I requested for him to start engine number 2; but seeing that he was busy entering in the new data; I told him I would get the engine started. Ground control inquired if we would be ready to go in sequence (number 3 or 4 for departure) and I told the first officer to let them know that we would. While starting the engine we began to get a printout to add an alternate since the weather in ZZZ now required it. Admittedly; I turned my attention to the printout to see what it was and once I looked back to the gauges I noticed the number 2 was not starting. I attempted to start the engine again. Once again; with the distraction of the runway change; new alternate; short release time; and multiple aircraft waiting to depart; the number 2 failed to start and I had failed to notice. Once holding short of 20C we ran the taxi checklist at which time the first officer pressed the T/O configuration button and we were given the okay. However; neither of us had verified the number 2 engine had started and as we rolled onto the runway I was checking that we had speeds set; roll/to displayed; etc.; but never turned my attention to the engine gauges. It was the first officer's leg; and once cleared for takeoff he pushed the throttles forward. It was then that we both noticed that the second engine was not started. We aborted the takeoff roll and taxied off. Once on taxiway we started the second engine; got back in sequence; and departed with no issues.this was clearly a mistake on my part to not get a new departure time and slow down to make sure we were not task saturated. Better situational awareness to slow down and not let the situation dictate my readiness. Also; a better cross scan of all gauges and parameters. For what it's worth; a takeoff configuration button that doesn't recognize an inoperative engine and gives the okay regardless; seems odd. I understand this doesn't relieve the crew of all responsibility; but it does provide a false sense of security and readiness.

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Original NASA ASRS Text

Title: EMB-175 flight crew reported becoming task saturated on taxi and forgot to start second engine when cleared for takeoff.

Narrative: Leaving the gate at BNA we were expecting Runway 20R for departure. Once we got to Spot 4 we were assigned a quick release time and to expect Runway 20C; a shorter taxi. There were about 4-5 aircraft that had pushed or were in the process of pushing; all departing Runway 20C. We taxied via T4; crossing 31; and held short of S7 for a passing aircraft. The First Officer had started entering in the new runway and sent for new takeoff data. I requested for him to start engine number 2; but seeing that he was busy entering in the new data; I told him I would get the engine started. Ground Control inquired if we would be ready to go in sequence (number 3 or 4 for departure) and I told the First Officer to let them know that we would. While starting the engine we began to get a printout to add an alternate since the weather in ZZZ now required it. Admittedly; I turned my attention to the printout to see what it was and once I looked back to the gauges I noticed the number 2 was not starting. I attempted to start the engine again. Once again; with the distraction of the runway change; new alternate; short release time; and multiple aircraft waiting to depart; the number 2 failed to start and I had failed to notice. Once holding short of 20C we ran the taxi checklist at which time the First Officer pressed the T/O CONFIG button and we were given the okay. However; neither of us had verified the number 2 engine had started and as we rolled onto the runway I was checking that we had speeds set; ROLL/TO displayed; etc.; but never turned my attention to the engine gauges. It was the First Officer's leg; and once cleared for takeoff he pushed the throttles forward. It was then that we both noticed that the second engine was not started. We aborted the takeoff roll and taxied off. Once on taxiway we started the second engine; got back in sequence; and departed with no issues.This was clearly a mistake on my part to not get a new departure time and slow down to make sure we were not task saturated. Better situational awareness to slow down and not let the situation dictate my readiness. Also; a better cross scan of all gauges and parameters. For what it's worth; a takeoff configuration button that doesn't recognize an inoperative engine and gives the okay regardless; seems odd. I understand this doesn't relieve the crew of all responsibility; but it does provide a false sense of security and readiness.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.