Date: 201601
Local time of day: 1801-2400
Location: PHL.Airport, PA
Flight conditions: VMC
Light: Night
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower PHL
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Time Pressure; Situational Awareness
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Rejected Takeoff; Flight Crew Became Reoriented
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: During preflight planning my First Officer briefed a flaps 20 departure off of runway 8 in PHL. As we were taxiing to runway 8; after crossing runway 17; I called for the 'delayed start' checklist. After that checklist was completed we were given the instruction to 'line up and wait on runway 8' from ATC. When we were given this instruction I called for the 'flaps 20; before takeoff' checklist. At some point during this time; I told ATC that we needed 60 seconds on the runway. He approved the request and asked why. My response was we just needed more time. My first officer completed the checklist as we were taking runway 8; but during his flow; he selected flaps 8. When the checklist was run neither of us caught it and we both acknowledged that the flaps were at 8 degrees. We were then given a clearance to takeoff runway 8. My first officer was the pilot flying; and after he advanced the thrust levers and he was releasing the brakes; he noticed and said the flaps are out of position and 'flaps should be at 20.' I immediately called for an abort; and took control of the aircraft. The maximum speed that we reached was approximately 50 knots. We taxied off the runway and then contacted dispatch. We ultimately returned to the gate and the flight was later cancelled. This was a complicated event that had several factors leading up to it. First off; we did feel a bit of a rush from ATC. Neither one of us expected to be given a line up and wait clearance right away. That is why I called for the extra time. With that said; even though ATC approved our request; sometimes you can still feel the pressure of them wanting to move aircraft. Secondly; although I called for flaps 20 and my FO (First Officer) responded flaps 20; we were being hurried onto runway 8. Multiple times during this short period of time was the number 8 talked about with ATC. I do believe that it's very possible when I called for flaps 20; because of the cross chatter about runway 8; he SAID flaps 20; but was THINKING flaps 8 simply because this number was being said multiple times during this short time frame. Once the flaps were selected and we ran the checklist. He said 'flaps set 8 degrees' and I acknowledged 'flaps indicating 8 degrees' because that is what was set; and that is what I observed at that time on the flaps indicator.I do believe a possible way to mitigate this error is to redesign the checklist so that the flaps are set prior to taxi for the runway planned. This will allow for a shorter before takeoff checklist; and with the aircraft already configured; numbers will not be talked about or thought of that might cause interference between the aircraft configuration and the operation as a whole. I know there are some airlines that do this. I know there are other factors involved as to why we run our checklists the way we do; but this was the first thing that came to my mind initially.


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


Synopsis: CRJ-200 flight crew reported they began takeoff roll with flaps incorrectly set; but caught it early in the roll and rejected the takeoff.