RWY EXCURSION AFTER A BE23 SUNDOWNER PLT LOSES CTL OF HIS ACFT ON THE ROLLOUT AFTER LNDG WITH A XWIND CONDITION; RWY 12 AT 00R; TX.

Narrative

UPON LNDG; WHICH I CONSIDERED TO BE A FIRM; BUT NORMAL LNDG; THE ACFT TOUCHED DOWN ON THE 2 MAIN GEAR. THE PWR WAS AT IDLE AND THE ACFT APPEARED TO BE ALIGNED WITH THE CTRLINE OF THE RWY. SUBSEQUENTLY; THE R WING APPEARED TO RISE; AND I FELT A FORCE TOWARDS THE L SIDE OF THE AIRPLANE. AT THAT MOMENT THE FLAP LEVER SLAMMED TO THE DOWN POS (FLAP UP POS). THE PLT TRIED TO CORRECT TO THE R BY APPLYING MORE R RUDDER AND R AILERON. THE ACFT WAS NON RESPONSIVE; AND THE PLT COULD NOT MAINTAIN DIRECTIONAL CTL. THE ACFT KEPT DRIFTING TO THE L AND CAME TO REST APPROX 50 FT N OF THE RWY IN THE GRASS. THE RWY USED WAS RWY 12 AND THE WIND WAS APPROX 160 DEGS AT 12-15 KTS. APPROX 5 MINS AFTER MYSELF AND THE PLT EXITED THE ACFT; AN ONLOOKER ARRIVED AT THE SCENE WITH PART OF THE MAIN GEAR THAT HE RETRIEVED FROM THE RWY. CONTRIBUTING FACTORS COULD BE FROM MECHANICAL WINDSHEAR/TURB; CAUSED BY HANGARS AND TREES IN CLOSE PROX TO RWY. LATER; I GATHERED INFO FROM THE LCL PLTS CONCERNING THIS PHENOMENA. APPARENTLY; THE POINT AT WHERE WE TOUCHED DOWN ON THE RWY IS KNOWN TO HAVE WINDSHEAR AND TURB -- SO MUCH; THAT THE LCL PLTS ALL KNOW TO LAND BEFORE OR AFTER THAT POINT. I BELIEVE THERE SHOULD BE A PUBLISHED NOTAM REGARDING THAT WINDSHEAR AREA; OR A WINDSOCK SHOULD BE PLACED THERE. IT IS ALSO POSSIBLE THAT THE LNDG GEAR MECHANICALLY FAILED.