GravAccel (for Gravitational Acceleration) Lets you scale the height of the airborne periods. The greater this value, the greater the height. If the biped appears to be going too high, reduce this value; if the biped goes too low, increase it. Each biped has its own Gravitational Acceleration value. Default=Based on the height of the biped.
If feet are the active 3D Studio MAX units and the biped is about 5 feet 10 inches tall, then Gravitational Acceleration equals about 32, for 32 ft. per second per second. For other biped heights, Biped scales this value to naturalistically fit the scene; the Gravitational Acceleration value also changes to agree with other unit systems, such as metric.