Narrative:

I taxied from my hangar on the south end of gnoss field, novato, ca the runup area for a takeoff on runway 31. I was #2 behind an small aircraft Y facing west. The wind was from the west. 90 degrees off the runway heading of 310 degrees the aircraft Y completed a runup and departed on 31 saying he would remain the the traffic pattern for a turn on downwind for 31. I taxied up to the runway facing the east. An small aircraft ona 31 downwind was observed after he announced his position. No aircraft was on base leg and I asked my right seat pilot if he could see any aircraft on final approach. None was noted. I announced my departure on runway 31, and at this time noted the departure aircraft Y on the crosswind leg. As we gained airspeed to approximately 55 KTS, with the nose gear off the runway, we heard aircraft Z announce departure on runway 13. I retarded the throttle and moved over to the right, and about this time the aircraft Z was upon us. He managed to be above us and continued a takeoff against traffic, with a climbing turn to the east. I consulted with the gnoss field airport manager and he told me he was listening on the radio and also witness the takeoff of aircraft Z against the traffic. He also told me the aircraft Z was between 50-100' over us on takeoff. The airport manager indicated that aft Z appeared to be waiting for traffic on runway 31 and then taking off on 13 against traffic.

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Original NASA ASRS Text

Title: SMA PLT TAKES EVASIVE ACTION, ABORTS TKOF AS OTHER ACFT DEPARTS AGAINST TRAFFIC AT UNCONTROLLED FIELD.

Narrative: I TAXIED FROM MY HANGAR ON THE S END OF GNOSS FIELD, NOVATO, CA THE RUNUP AREA FOR A TKOF ON RWY 31. I WAS #2 BEHIND AN SMA Y FACING W. THE WIND WAS FROM THE W. 90 DEGS OFF THE RWY HDG OF 310 DEGS THE ACFT Y COMPLETED A RUNUP AND DEPARTED ON 31 SAYING HE WOULD REMAIN THE THE TFC PATTERN FOR A TURN ON DOWNWIND FOR 31. I TAXIED UP TO THE RWY FACING THE E. AN SMA ONA 31 DOWNWIND WAS OBSERVED AFTER HE ANNOUNCED HIS POS. NO ACFT WAS ON BASE LEG AND I ASKED MY RIGHT SEAT PLT IF HE COULD SEE ANY ACFT ON FINAL APCH. NONE WAS NOTED. I ANNOUNCED MY DEP ON RWY 31, AND AT THIS TIME NOTED THE DEP ACFT Y ON THE XWIND LEG. AS WE GAINED AIRSPD TO APPROX 55 KTS, WITH THE NOSE GEAR OFF THE RWY, WE HEARD ACFT Z ANNOUNCE DEP ON RWY 13. I RETARDED THE THROTTLE AND MOVED OVER TO THE RIGHT, AND ABOUT THIS TIME THE ACFT Z WAS UPON US. HE MANAGED TO BE ABOVE US AND CONTINUED A TKOF AGAINST TFC, WITH A CLBING TURN TO THE E. I CONSULTED WITH THE GNOSS FIELD ARPT MGR AND HE TOLD ME HE WAS LISTENING ON THE RADIO AND ALSO WITNESS THE TKOF OF ACFT Z AGAINST THE TFC. HE ALSO TOLD ME THE ACFT Z WAS BTWN 50-100' OVER US ON TKOF. THE ARPT MGR INDICATED THAT AFT Z APPEARED TO BE WAITING FOR TFC ON RWY 31 AND THEN TAKING OFF ON 13 AGAINST TFC.

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.