nwt

Nah, pilots are already used to using propellers as speed brakes, so nothing changes much there. I think you might be missing the fact that during regeneration, you are going to need significant torque on the prop--it isn't going to be freewheeling. I'd expect the prop settings to be closer to that of a climb than anything else. To put it another way: intuitively, I'd expect the prop settings to be similar when you are trying to transfer the maximum amount of energy between the motor and the air, regardless of the direction of that transfer. Though we do care about efficiency, so maybe a cruise setting would be better... but anyway, this is a minor point as it doesn't affect feasibility--If we ever get to that point, we'll figure it out just fine either way. Agreed. There should be no changes that affect powered flight in any way and no additional systems apart from the electronics required for harvesting the energy. The energy loss here will be exactly equal to the amount of weight lost in proportion to the total weight--no more, no less. For example, if an otter is fully loaded at max gross weight (12,500 lbs) and drops 23 jumpers at 200 lbs each (4,600 lbs), you've lost 37% of your gravitational potential energy. That's pretty significant, and my gut says jump otters don't operate anywhere near max gross. I agree wholeheartedly with this sentiment, except for the reference to time. Stop thinking about time and instead think about gravitational potential energy. Time isn't relevant in the way you're thinking, as I've explained previously. Haha that's a really interesting point, but using a helicopter because it will recover energy better would be like cutting off your nose to spite your face. You are going to spend so much more energy to recover a couple more peanuts!

What's a PEP rig?

I think you are looking at this wrong. Wind turbine energy production scales in proportion to velocity cubed because the actual energy content of the wind scales that way. In our case, we have a fixed amount of energy available for recovery, in the form of gravitational potential. The more quickly we recover it, the more quickly it is depleted--you don't get more of it simply by burning through it faster. Overall efficiency is going to be a summation of multiple factors. Propeller efficiency vs. speed as you mention is an important one that I don't have a good intuition for. Another one will be minimizing losses through the energy cost of flight, which would seem to favor getting the flight over with as soon as possible. Another one will be the cost of drag, which scales with the square of wind speed... though maybe this point is not distinct from my previous one. I think the amount of energy we recover is going to be sufficiently small compared to the energy we've spent, that this will not be a factor even though we are recovering it in a shorter period of time than we are spending it. edit: One last point: As people have mentioned, harvesting this energy will necessarily increase drag because energy is never free and it has to come from somewhere. However, this may actually work to our advantage by allowing an even faster descent. As has been mentioned, the descent is limited by max airspeed. The consequence of that is the more drag you have, the steeper angle you can dive at to obtain that max speed, which results in a faster vertical rate. edit 2: Another realization: A good chunk of gravitational potential energy is going out the door on jump run.

I wouldn't argue against that. It doesn't say that. So unless you have some other reference such as an FAA interpretation or something, I don't see why we should believe it means that. For a typical skydiving flight, you're at the first intended point of landing for the entire flight. I could see that maybe being different for a sightseeing flight.

This hasn't been brought up in a long time, but I just wanted to add that IMO only 30 minutes total fuel is required if you are taking off and landing at the same airport--not 30 minutes in addition to the anticipated flight time. https://www.law.cornell.edu/cfr/text/14/91.151

I absolutely love my TFX. I tried to demo a G4 but couldn't make it work with my glasses.

I disagree. If the G3 performs poorly in the tests (and I expect it would), that could be pretty damaging to Cookie, even though they have something better now. I would say this even if the G3 were no longer being marketed, but guess what--they are still selling it! "Look how bad our last product was" could be seen as a poor marketing strategy.