Date: 201310
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Aircraft: Dash 8-400
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Takeoff / Launch
Airspace: Class E ZZZ
ATC / advisory: CTAF ZZZ; Center ZZZ
Second aircraft: Amateur/Home Built/Experimental
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Other Takeoff Roll
Result: Flight Crew Rejected Takeoff
Contributing factors: Airport; Human Factors
Primary problem: Human Factors

Narrative: We were [departing] an uncontrolled field. We had been listening on CTAF on COM2 since we had finished preparations to close up and depart. During this time; we had taxied out; made a call on CTAF to announce our intentions and received our clearance from Center on COM1. We taxied slowly to allow the cabin time to prepare for takeoff being the short taxi it was. We stopped at the end of Runway XX waiting and during this time we were listening on CTAF for any other traffic. We heard no one; we cleared the area and saw no one on final or departure; completed the checklist and proceeded to takeoff. At about 40-50 knots; as Pilot Flying; I noticed an airplane appear from above the green treeline background into the blue sky that had departed Runway XY. I informed the First Officer; rejected the takeoff and began to exit the runway. The small GA aircraft flew over us at what seemed like low altitude all the way down the runway. On exiting the runway we made a call and told the aircraft to identify themselves. On a scratchy and very weak radio; they replied they had heard us taxiing out and yet had made no notice of their presence. We told them we had been monitoring and heard no calls for their taxi or takeoff. We knew our radios were operational because we had received the airport ASOS and had good contact during our arrival. It appears the GA aircraft either had made no calls or had such a poor radio it had not transmitted. There is a small hump in the runway which certainly doesn't help seeing the end traffic; but giving the benefit of the doubt; it's possible the transmission was too poor to reach us. We did all the right things to make sure the area was clear with radio calls; visual scanning before proceeding onto the runway and using TCAS. This illustrates the danger we deal with every time we operate in an uncontrolled ATC environment. It appears the UNICOM person had not heard this person's transmission and the fact the only time we received communication from the GA plane was after he had departed and we had questioned him which leads us to believe he wasn't even aware of us. Factors that didn't help were the hump in the middle of the runway and the dark treeline at the far end of XX and a dark colored airplane. We taxied off; completed our flows and reassured the passengers. The remainder of the flight was uneventful. My First Officer did a great job of making our presence known in the CTAF environment and doing his duties. Our suggestion would be a system like that of another uncontrolled airport; ZZZ1; where the UNICOM operator informs the air carrier crews of any announced or known traffic coming or going. Of course that's only of use if the other traffic obeys the uncontrolled airport position reports.I think having a dedicated UNICOM operator help when scheduled air carrier traffic is operating; would help inform us of other traffic but this would only work if the other traffic announced their position. Otherwise it's just a risk associated with operating at uncontrolled fields.


Second narrative: We received our clearance and release from Center; and I made a call over CTAF advising we were taking Runway XX for departure. We visually cleared the final on both ends of the runway; as well as all visible parts of the runway environment. As we exited the runway; I asked if the departing aircraft was on CTAF frequency. The pilot of the other aircraft responded; although his radio was weak in signal. He indicated that he made position calls; and while I can't say whether he did or not; I am certain that they were not received by our radios. Unfortunately; I am not sure how we could have been more aware of the presence of the aircraft departing the opposite end of the runway. I will continue to exercise the highest levels of situational awareness; and follow all proper communications procedures at uncontrolled airports. Hopefully I will continue to be lucky; as that was a legitimate mitigating factor in this incident; as it is whenever operating out of an airport where radio communication is non-compulsory.


Synopsis: A Dash-8 flight crew; departing an uncontrolled airport rejected their takeoff prior to 80 knots when the PF spotted an opposite direction experimental aircraft just lifting off toward them.