Medic Air

Rockwell Grand Commander 690

The pilot and flight nurse were en route to pick up a medical patient. The airplane experienced an in-flight breakup while flying by the leeward side of the sierra nevada mountains in the general area where standing lenticular clouds had been observed. No evidence was found that the pilot obtained a weather briefing from flight service or the duat vendors prior to departure. Pilots flying in the general area had reported airspeed variances from plus 60 to minus 40 knots. An in-flight weather advisory for occasional moderate turbulence was in effect. About one hour after the accident the weather service issued a sigmet for severe turbulence. Cause: an inadvertent encounter with severe turbulence which exceeded the design strength of the airplane's structure. Both occupants were killed.