AT ABOUT 1650 PDT, THE PLTS OF 2 RYAN ST3KR ACFT DEPD COALINGA ON A FLT TO LOS BANOS, CA. AT ABOUT 1709 PDT, THE PLT OF N48777 MADE A HAND SIGNAL TO THE OTHER PLT, POINTED TOWARD THE GROUND & ENTERED 'A NORMAL GLIDE.' SUBSEQUENTLY, THE PLT OF N48777 MANEUVERED THE ACFT TO LAND IN A COTTON FLD. HOWEVER, A WITNESS SAID THAT BEFORE LANDING, THE ACFT'S NOSE PITCHED UP, THEN THE ACFT ENTERED A STEEP DSCNT & CRASHED. IMPACT OCCURRED IN AN ESTD 20 DEG LEFT WING DOWN, 30 DEG NOSELOW ATTITUDE. THE ACFT CAME TO REST INVERTED. THERE WAS EVIDENCE THAT APRX 1/3 GAL OF FUEL HAD DRAINED FM THE FUEL TANK.THE CARBURETOR HAD BROKEN DRG IMPACT; NO FUEL WAS FND IN THE LINE TO THE CARBURETOR. THE FUEL SELECTOR WAS FND IN THE OFF PSN (SMALL POINTER PSND TOWARD 'BOTH OFF' & THE HANDLE POINTING TOWARD 'MAIN ON'). THE FUEL SYS HAD A STANDPIPE TO PROVIDE 3 GAL OF RESERVE FUEL, BUT THE PLT'S MANAGEMENT OF THE FUEL WASN'T DETERMINED. ANOTHER ST3KR PLT ESTD N48777 HADABOUT 10 GAL OF FUEL BEFORE THE FLT. A CHECK OF THE PLT'S BLOOD SHOWED AN ALCOHOL LVL OF 0.04%.