Date: 201710
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZ
Aircraft component: Flap Control (Trailing & Leading Edge)
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; Time Pressure
Second reporter function: First Officer; Pilot Flying
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: The ATIS at the gate was reporting a Runway XX departure with winds approximately 200@10; a slight quarter tailwind. We loaded the data with these wind conditions and with our data we headed to the runway. Unfortunately during the after start checklist we were slightly thrown off and missed a flaps 4 setting. After the tug disconnect; the FO did not put the flaps down. In a rush to get them put down during the checklist he put them to flaps 2 and we both agreed they were at 2. I believe this rush made us just assume position 2 as we normally do. I assume with the slight tailwind we were required to use 4; but again we missed this setting. We were just about to takeoff and the Tower told a previous aircraft the winds had shifted to a quarter headwind of 240 @10. Luckily with the wind shift we did not suffer too bad of a performance hit; however on the takeoff roll I think we both slowly started to notice the clues that we were a bit off. The V1 speed seemed slow at 118 kts. I again just assumed this was a tailwind penalty. The aircraft did perform well and rotated at what I would consider an acceptable distance. Still; things seemed not that abnormal. Once in the air the First Officer slowly brought the nose up and at this point we definitely noticed the speed tape. We didn't get any severe indications of stall; but it was apparent something was off. After takeoff we made a few comments to each other about the speed tape. I pulled up the takeoff data and immediately saw the flaps 4 setting right there on the page. I can certainly say this is a first for me. I do not normally miss the flap setting. I do believe this was all caused by us fixating on the flaps not being down during the checklist and then quickly just selecting 2. I've always tried not to be complacent while saying these numbers but it failed me this time by just saying 'TWO.' This could have been prevented by simply not rushing through the After Takeoff checklist; and not fixating on the flaps not being down yet.


Second narrative: When we were doing the after start checklist; I guess out of habit at ZZZ its almost always a flaps 2 takeoff. We both were waiting for the flaps to get to 2 and did not catch it.


Synopsis: ERJ-175 flight crew reported mistakenly taking off with flaps set at two instead of the computed requirement of flaps four.