Date: 201702
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
Aircraft component: Throttle/Power Lever
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Training / Qualification
Second reporter function: Pilot Flying; First Officer
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Rejected Takeoff; Flight Crew Returned To Gate; General Maintenance Action
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: Tower cleared us for takeoff. I spooled up engine 2 to 40% N1 to make the left turn from E1 onto the runway. I transferred the controls to the First Officer (FO) after we completed the before takeoff checklist. He advanced the Thrust Levers (TL) evenly toward the TOGA detent. I noticed a split in the engine N1 indications immediately. I saw engine 1 N1 at about 40%; and engine 2 N1 at the blue carrot (takeoff setting). The FO immediately reduced the TL's and called reject; which initially confused me because I thought engine 1 just needed a second or 2 to spool up to catch engine 2. This caused me to verbally override the FO's reject decision. He advanced the TL's once more; resulting in 'TLA NOT TOGA' EICAS message and master caution. I realized my mistake and called reject. I took the controls and turned off the runway at E3 taxiway. I made an announcement to the passengers and returned to the gate where we swapped airplanes.One obvious lesson: Once the TL's are reduced and the takeoff reject call is made; do not change your mind. Turn off the runway and sort out the issue.Lesson 2: Trust the pilot flying's judgement. The FO had good reason to reject. What I didn't know at the time was how much yaw he felt immediately after advancing the TL's; because he compensated for it with the rudder. That prompted him to look at the N1 gauges; which revealed a large split. He has a lot of time in this airplane and that takeoff thrust felt very abnormal to him. Lesson 3: I'm in the habit of often transferring controls to the FO with one engine already spooled at 40% N1 and the other at idle (20% N1). In this case that added to the confusion. From now on I'll transfer controls with the engines at symmetrical thrust. That takes away the initial confusion regarding takeoff thrust settings.


Second narrative: Tower cleared us for takeoff. As we were lining up with the runway for a rolling takeoff the captain transferred the controls to me. I quickly looked down at the thrust levers and noticed engine #2 thrust lever was slightly more forward then the #1 thrust lever. I figured this was due to aligning the aircraft on the center-line. So when the controls were transferred to me; I re-centered the thrust levers and advanced them both towards TOGA. Almost immediately; I felt a hard yawing motion towards the left. At first I thought the nose was not centered and applied right rudder. At this time the airplane was still veering to the left despite my rudder inputs. This caused me to briefly glance down at the EICAS and I observed while engine #2 was achieving N1 takeoff power; engine #1 N1 was fixed at approx 40%. I immediately called for the abort and placed both thrust levers to idle. Being on this airplane for almost 3 years; I have never felt yaw that extreme during initial takeoff.(From the time I advanced the thrust levers to the time I called the first abort was rapid; maybe 3-5 seconds). The captain then stated something to the effect of 'thrust is stabilized' and called to continue (after debriefing with the captain; I later became aware that he didn't feel the same yawing motion and did not find anything abnormal with the takeoff to call an abort.)With the captain calling to continue; I placed the thrust levers back towards TOGA and observed both engines where now producing takeoff thrust. So I continued the takeoff and advanced the thrust levers. Due to the confusion of the abort; I failed to completely place the thrust levers back into TOGA and received a 'ENG TLA NOT TOGA' displayed and we aborted the takeoff for second time. I recall at the time of the second rejected takeoff; N1% on both engines were producing thrust near TOGA; I just hadn't properly set them into the de-tent. As I recall; this all occurred while at a slow speed (below 80kts) and we exited at E3 taxiway off [the runway]. After speaking with passengers and maintenance we returned to the gate with no other issues.Even as a FO; I should have been more assertive in my decision to abort; to the point of guarding the thrust levers at idle. Even after the captain stated 'continue'; we were at a very low groundspeed on a dry runway. It would've been better to discuss it off the runway with the parking brake set even if my reject call was unfounded.


Synopsis: EMB-170 First Officer detected a strong yawing moment as thrust was advanced for takeoff and called for the reject. The Captain; seeing nothing wrong called for the takeoff to continue. The First Officer advanced the thrust levers; but not to the TOGA detent causing an 'ENG TLA NOT TOGA' message to be displayed and the takeoff rejected.