On July 27, 1993, about 1930 hours Pacific daylight time, a Robinson R22-B helicopter, N23517, crashed while maneuvering along the beach at Venice, California. The helicopter was being operated as a visual flight rules (VFR) local area instructional flight when the accident occurred. The helicopter, operated by Complete Aviation Services Inc., Burbank, California, received substantial damage. The certificated commercial pilot/flight instructor and a student pilot were not injured. Visual meteorological conditions prevailed. The flight originated at Burbank at 1800 hours; however, it had departed the Los Angeles International Airport (LAX) area about 1920 hours. Numerous witnesses reported observing the helicopter flying northbound at low level along the shoreline of Dockweiler Beach at high speed. The helicopter was observed to begin a near vertical pull up, followed by a rapid descending 180 degree right turn to go southbound. As the helicopter was completing the turn and still descending, it struck the beach in a nose low attitude. The helicopter came to rest on its left side. The pilot reported that he was providing dual instruction to his student pilot and was enroute to Burbank after departing LAX. The pilot decided to initiate 360 degree tight turns to demonstrate collision avoidance maneuvers to his student. From an altitude of about 25 feet, the pilot climbed to 150 feet and started the turn. The pilot reported that the bank angle in the turn did not exceed 45 degrees. The main rotor RPM decayed and the pilot decided to abort the maneuver and attempted to regain rotor RPM. The pilot indicated that the RPM failed to increase and the helicopter entered an uncontrolled descent. The pilot selected a landing spot on the beach and attempted to level the helicopter. The landing gear skids dug into the sand and the helicopter rolled over. The pilot reported that he did not have any recollection of the power setting during the recovery attempt, and did not recall the airspeed during the turn. The FAA's Basic Helicopter Handbook publication, Chapter 3, Loads and Load Factors, states in part: ..."Any time a helicopter flies in a curved flight path, the load supported by the rotor blades is greater than the total weight of the helicopter. The tighter the curved flightpath, that is, the steeper the bank,...the greater the load factor. The load factor and, hence, apparent gross weight increase is relatively small in banks up to 30 degrees... Above 30 degrees of bank, the apparent increase in gross weight soars. At 30 degrees of bank, the apparent increase is only 16 percent, but at 60 degrees, it is 100 percent." In Chapter 11, Helicopter Flight Maneuvers, Turns, it states in part: ..."To enter a turn from straight-and-level flight, apply sideward pressure on the cyclic stick in the direction the turn is to be made... The more the cyclic stick is displaced, the steeper the angle of bank; therefore, adjust the cyclic stick to obtain and maintain the desired bank throughout the turn. Increase collective pitch and throttle as necessary to maintain altitude and RPM..."