it doesnt. it may affect how fast it lifts off, but not how fast it drops. now, if you had said weight put inside the body of a helecopter, then it would have made a difference because of the relationship between surface area and mass. if you have alot of surface area and alittle mass, then you fall slowly, if you have alittle surface area and alot of mass, then you fall quickly. in the same way, if you have alot of surface area and alot of mass, then you would fall at the same speed as somethign with a little mass and a little surface area.