THE HELICOPTER EXPERIENCED A MAIN ROTOR DRIVE SYSTEM DISCONNECT, AN UNCONTROLLED DESCENT & SUBSEQUENT INFLIGHT COLLISION WITH TERRAIN IN A HILLY DESERT AREA. THIS WAS THE THIRD & LAST IN A PLANNED SERIES OF MARKETING DEMO FLTS CONDUCTED FOR THREE USMC OFFICERS. DURING THE POST CRASH EXAMINATION OF OVER-RUNNING CLUTCH COMPONENTS REVEALED THAT THE CAGES & SPRAGS WERE BOUND UP IN THEIR NORMAL ENGAGED POSITIONS. TWO OF THE THREE DRAG STRIPS WERE OBSERVED TO HAVE ABRASION SIGNATURES ACROSS THEIR ENTIRE WIDTH OF .07 INCHES; THE ABRASION AREAS GENERALLY MATCHED THE GEOMETRY OF THE ADJACENT BALL BEARING RACE. EXAMINATION OF ENGINEERING DRAWINGS FOR THE CLUTCH REVEALED THAT FOR THE DRAG STRIP TO CONTACT THE ADJACENT BEARING RACE, THE CLUTCH WOULD HAVE TO PROTRUDE OUT OF ITS NORMAL RELATIVE POSITION BY ABOUT .20 INCHES. HEAVY OXIDATION OBSCURED THE POTENTIAL RELATIVE RUNNING POSITION MARKINGS BETWEEN THE INNER & OUTER RACES.