Narrative:

Event occurred under light and variable winds. The windsock lay perfectly limp and AWOS reporting a crosswind at 4 KTS. Following my broadcasting on the local unicom frequency (122.7) that I was taking the active runway 1 and departing to the north, I entered the runway and proceeded with a normal takeoff. Just after lifting off, I noted an aircraft on takeoff roll on the same runway, but opposite direction (ie, runway 19). (Later this aircraft was idented as aerostar by radio contact.) immediately began evasive action by a right turn, continuing to climb. The aerostar continued a straight ahead takeoff. I had been monitoring the unicom frequency and heard the transmission of the previous aircraft taking off (on runway 19), but heard no transmission from the aerostar. The primary contributing factor to this event is that the terrain at jwn is such that aircraft in the run-up and initial sections of both runways (01-19) cannot see one another. Under conditions of light and variable winds, plus light traffic, there can be ambiguity about the runway in use, leaving it to the pilots to communicate on unicom. In the event of a malfunction of transmission or two simultaneous xmissions by the aircraft about to take off, one is relying on see and be seen. This can only apply when one sees the full runway, which is not possible on the ground at jwn.

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Original NASA ASRS Text

Title: C182 PLT HAD AN NMAC WITH A PA60, WHEN THE PA60 PLT DID NOT COMMUNICATE OR LISTEN ON UNICOM. THE PA60 PLT STARTED TKOF ON RWY 19 AFTER C182 PLT WAS ALREADY ON TKOF ROLL ON RWY 1.

Narrative: EVENT OCCURRED UNDER LIGHT AND VARIABLE WINDS. THE WINDSOCK LAY PERFECTLY LIMP AND AWOS RPTING A XWIND AT 4 KTS. FOLLOWING MY BROADCASTING ON THE LCL UNICOM FREQ (122.7) THAT I WAS TAKING THE ACTIVE RWY 1 AND DEPARTING TO THE N, I ENTERED THE RWY AND PROCEEDED WITH A NORMAL TKOF. JUST AFTER LIFTING OFF, I NOTED AN ACFT ON TKOF ROLL ON THE SAME RWY, BUT OPPOSITE DIRECTION (IE, RWY 19). (LATER THIS ACFT WAS IDENTED AS AEROSTAR BY RADIO CONTACT.) IMMEDIATELY BEGAN EVASIVE ACTION BY A R TURN, CONTINUING TO CLB. THE AEROSTAR CONTINUED A STRAIGHT AHEAD TKOF. I HAD BEEN MONITORING THE UNICOM FREQ AND HEARD THE XMISSION OF THE PREVIOUS ACFT TAKING OFF (ON RWY 19), BUT HEARD NO XMISSION FROM THE AEROSTAR. THE PRIMARY CONTRIBUTING FACTOR TO THIS EVENT IS THAT THE TERRAIN AT JWN IS SUCH THAT ACFT IN THE RUN-UP AND INITIAL SECTIONS OF BOTH RWYS (01-19) CANNOT SEE ONE ANOTHER. UNDER CONDITIONS OF LIGHT AND VARIABLE WINDS, PLUS LIGHT TFC, THERE CAN BE AMBIGUITY ABOUT THE RWY IN USE, LEAVING IT TO THE PLTS TO COMMUNICATE ON UNICOM. IN THE EVENT OF A MALFUNCTION OF XMISSION OR TWO SIMULTANEOUS XMISSIONS BY THE ACFT ABOUT TO TAKE OFF, ONE IS RELYING ON SEE AND BE SEEN. THIS CAN ONLY APPLY WHEN ONE SEES THE FULL RWY, WHICH IS NOT POSSIBLE ON THE GND AT JWN.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.