lets look at this in a different baseline comparison. 1 helicopter at max weight, and that same helicopter at a reduced weight.(say full tank + Pax) and (near empty + no Pax). also must assume that the collective pitch is adjust correctly by maintenance to give you proper autorotational rpm range throughout the expected gross weights. finally we must assume that both are flown at the same conditions(DA, Airspeed, etc...). with all that being said. Both helicopters will have the same ROD if the NR is at 100%. the difference will be... if both pilots put the collective all the way down, the heavier aircraft will see a large overspeed until "some" amount of collective is pulled to arrest the NR back at 100%. once both reach 100% NR the ROD should in theory return to the SAME charted value. but the heavier helicopter will have some collective pitch applied. for my aircraft, we expect 1% NR increase or decrease for each 100 pounds/ 1000 feet DA increase/decrease. if the weight or da goes up, so will autorotational NR with collective full down. if the DA or weight reduces, the full down NR will also decrease. any questions???