Date: 201707
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: Marginal
Weather elements / visibility: Rain
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction
Second reporter function: Pilot Not Flying; Captain
Anomaly: Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: We had already ran the takeoff numbers before leaving the gate. I had entered 'wet' for the runway conduction because of the on and off raining to be on the conservative side. I informed the captain of my decision and he agreed. The captain entered the takeoff speeds and flex temp; before leaving the gate as well. We were pushing from gate. Originally assigned spot 5; then spot 4; then finally spot 3 was our final push clearance. We had noticed on the push pack that 2 more aircraft were ready to be pushed as well; it made sense to us that we would get spot 3 to give room for the other two aircraft at spot 4 and 5. During the push; once cleared to start the engines; I started the number 1 engine as instructed by the captain. Once the push was complete and we had the wave; I set flaps to 2. Then to prevent jet-blasting the aircraft behind us; just in case we were in a rut or divot on the ramp; the captain suggest we start the number 2 engine. I agreed and started number 2. While we were waiting for the engine to finish starting and stabilize; we heard over ground frequency that there was to be a medical emergency inbound to or around our ally-way. With this in mind we tried to hurry up and run through the after-start checklist. During the after-start checklist; I had read the proper runway; speeds and flex temp. Something along the lines of 'runway 1V; 120; 126; 148; 201; flex 31'(may not be exact numbers but it is as close as I could remember). The captain read it back just as I had stated it. Then I stated 'flaps; verify; 2;' without focusing on the MCDU as I should have. I do remember seeing flaps 2 set on the EICAS. On the taxi to runway 1 I thought to myself that the takeoff speeds seemed odd but thought it was due to the 'wet' runway setting. I did not decide to investigate further or ask the captain what he thought. We took off runway 1 with the speeds as is and the flap 2 configuration. As we got to V1 and rotate; the speed seemed low to me as for how heavy we were. After liftoff; the Pitch Limit Indicator showed in the color green for just about a second or so; I have seen this before and thought no different than I would any other time; just to respect it. It went away and then the captain said something like 'these speeds aren't right.' Then he said 'keep your speed up'; which I obliged as it was also gust aloft and wanted to keep the speed away from the low-speed awareness tape. We continued the departure as normal. A few minutes later the captain checked the Takeoff Data page and noticed that the data said we should have done a flaps 4 takeoff.Talking to the captain after the flight; we both agreed that what happened; should not have happened. We came to the conclusion that we both should have took extra diligence into confirming the information from the Takeoff Data page and ensure that the proper information was entered and the proper configuration was put into place. We also agreed that we should not have let the emergency aircraft situation rush us; contributing to the mistake of not setting the proper flap setting for this particular takeoff.


Second narrative: [Report narrative contained no additional information.]


Synopsis: ERJ-175 flight crew reported a takeoff with an incorrect flap setting and subsequent lift off at a low airspeed.