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by clueless123 2203 days ago
Fantastic Skydiving vehicle.. If you can get 9 people (+ gear) 12'000ft on a 30 minutes flight, then you can glide all the way down for the next load. at $6 worth of fuel it would be a game changer.
7 comments

Wondering if they could do regenerative braking with the props on the way down.
In theory yes. In practice the amount of regained energy would probably be negligible and not worth the loss of positive flight control it would entail.
Seriously, $6 for 30 min at ~100mph is pretty amazing. There are lots of cars that are less fuel efficient.
How much would that cost with conventional fuel?
A lot. Perhaps 75 gallons/hr. Jet fuel is currently a about $1/gallon.

Even a much smaller plane like a 172 can easily burn $50/hr just in fuel. Much lower flow rate, but it’s leaded a gas at about $4.50/gal

Way more than that these days. There’s only one supplier of 100LL, and even they don’t want to be in the business anymore.
Its not just the fuel cost, maintenance of electric motors is substantially cheaper. Plus, there's no need to transport and store specialty Avgas.
The article isn't totally clear on this point, but I wonder if the $6 included the costs for taxiing and taking off, or just the 30 minutes in the air?
You’d have to swap batteries to keep the flight cadence i think.
From the article:

“In airline service, operators would need to recharge the batteries between flights, with charging times correlating closely to flight times, says Ganzarski. That means the batteries would need about 30-40min of charging following a 30min flight. The weight of the batteries makes swapping spent cells for fresh cells unfeasible between flights, he says.”

Yeah i wasnt very clear. Drop zones keep those planes moving all day long. It could be done but the substantially increased amount of time spent ’refueling’ means you’d either need more planes or just accept fewer customers.
What I suspect would kill this for sky diving is recharge time. Even if fuel expenses go to zero, it's not going to be viable if it has to recharge for several hours after every hop.
What makes you think it's 7 hours? Any off the shelf EV can charge to 80% in under an hour. Some can do it in under 30 minutes.
Did you read the article? It states 30-40 min recharging after a 30 min flight.
Which means you now need two airplanes to do what one did previously.

Realistically a skydiving flight would be more, as your climbing at full power much more than a short hop commuter flight normally would.

Battery swaps. In the air is next. Especially for city surveillance drones....
For surveillance drones it's going to be wireless power. Either microwave or laser.
Or solar, if the threat profile is low.

Could even combo the two approachs...have a large high altitude solar "mothership", that beams directed power at the drones.

PV is good enough for drones if wing area is large, the aerodynamics are super-efficient, and it's daytime.
Or 5G ;)
A lot of the expenses in flying arise out of regulatory requirements. Want to carry passengers? Pilot needs a license that take several hundred hours minimum to obtain. Want to use a part in an airplane? Getting it through the FAA certificating process will inflate its cost by several multiples. Want to operate an aircraft? You need to get it inspected every $fixnum number of hours of operation by a mechanic who in turn has to do everything the 'certified' way and is himself certified by the FAA.

It's these costs, not fuel costs, that account for a big percentage of the cost of flying. There's no meaningful way to reduce the cost of flying without reducing them. Perhaps electrics will incur much lower costs in maintenance, reducing costs somehow.

Well, don't discount fuel.

I had the oppurtunity to spend an hour in a T-6 trainer a number of years ago. This was the primary trainer used by Air Force in WW2. Big radial engine. At full throttle (which we were mostly at, as we were doing acrobatics), that eats through fuel at about 40 gallons/hr. That's $200/hr just in gas, for a plane that carriers 2 people and isn't really all that powerful.

Fuel typically accounts for 20-30% of airline operating expenses. For 2019, it accounted for 23.7% [1].

1: https://www.iata.org/contentassets/ebdba50e57194019930d72722...

Gas is a huge deal in large passenger planes where instead of miles per gallon, they actually measure efficiency in gallons per mile.

The 747 for example eats about 1 gallon per second (~3600 gallons per hour) according to this source: https://science.howstuffworks.com/transport/flight/modern/qu...

We measure fuel efficiency for cars in "liters per 10 km" in my country.
This is absolutely true, hence why the Cessna is so cheap to operate. Once the engine and power system are certified everything else is good to go.
The tax free/subsidized fuel era is likely to end fairly soon (unless we're going to fail badly at climate change mitigation measures).