Hover OEI vs Cat A
This thread has run a bit abeam, can I help straighten it out?
1) HOGE and OEI are vastly different performance points, plotted differently and tested differently. We all know this.
2) When we look at Cat A/PC-1/PC-2/PC-2e capability, the power needed to hover OGE and the power available at the Cat A weight are actually locked closely in the same performance equations, so that OGE OEI Hover capability is a good predictor of Cat A from a rig. This should be obvious to us all, the ability to stagger out of a low speed takeoff after an engine failure is roughly driven by the excess power you have in that situation, the excess power to make the climb and acceleration possible.
3) I have cross plotted the performance of several helicopters, and it appears that when the helo has a weight of about 120% of the weight where it can HOGE OEI, it can make a rig takeoff with dip down and then fly the full Cat A profile. In other words, if it has OEI power equal to the twin power needed to HOGE, it can then be loaded to 20% more weight and make a PC-1 takeoff.
4) I looked at the D Model Chinook manual (thanks!), it would seem to allow HOGE at SL 20 degrees at about 34000 lbs while OEI, thus it might allow a PC1 takeoff at somewhere around 40,000 lbs from a rig (my 120% rule). With an Army empty stripped weight of 25,000 lbs, and maybe 4000 lbs of seats, interior and other equipment added, it might weigh about 29,000 lbs empty. That would allow 11,000 lbs of useful load. It burns about 2300 lbs per hour at 130 knots, for about 18 lbs per NM.
At 150 nm, it would need 2700 lbs of gas each way, 5400 lbs round trip, plus about 1700 reserve (45min) for a total of 7125 lbs of gas. From 11,000 lbs, that yields about 4,000 lbs of people, or 16 pax at 240 lbs each.