The primary problem resulting from this tumbling and spinning is the increased likelihood of severe parachute entanglement during main chute deployment. These problems too, however, have all but been eliminated except for a few old systems that are still in use. The vertical velocity at which the canopy lowers the aircrew member is essentially a function of parachute design configuration, fabric porosity, canopy size, and integrity. Generally, the larger the canopy diameter, the lower the landing velocity. Parachute opening accelerations vary as a function of canopy diameter, but not in the way one would normally assume.
Smaller canopies impart a greater G-loading during opening than do larger ones.
The canopy, upon deployment, streams behind the aircrew member, creating a loss of momentum, and this affects the period of time to inflation. The smaller canopy reduces momentum to a lesser degree and inflates more rapidly than does a larger canopy of the same basic design. The differences in momentum reduction and filling time account for the greater acceleration of the smaller canopy. The aircrew member performing an emergency parachute landing does not have the luxury of selecting the landing site, weather conditions, and the like. The landing may be in mountainous terrain where higher rates of descent and harder landings might be experienced, along with updrafts and downdrafts.