POOR JUDGEMENT OF THE NON-RATED PILOT, DUE TO IMPAIRMENT FROM CONSUMPTION OF ALCOHOL, HIS LACK OF TRAINING/QUALIFICATION, HIS IMPROPER USE OF THE ENGINE CONTROLS WHICH RESULTED IN LOSS OF ENGINE POWER FROM PROBABLE CARBURETOR ICE, AND HIS FAILURE TO MAINTAIN SUFFICIENT AIRSPEED WHICH RESULTED IN AN INADVERTENT STALL AND SUBSEQUENT COLLISION WITH THE TERRAIN.