Flying Caravan ??

It looks like commercial electric flight is fast becoming a reality..
https://robbreport.com/motors/aviation/worlds-largest-electric-airplane-takes-flight-2930460/
And
https://www.magnix.aero/

Wow that is applying technology where it is needed. Guess it is common sense like EV's are best in cities not the outer roads.

A local Sydney operator,..Sydney Seaplanes...have anounced they will have a fleet of these “eCaravans” operating from the Harbour by 2023
They fly scenic flights and local commuter flights between the harbour and river locations..

Hate to run out of battery power at 5000 feet, the plane must be designed for easy non-powered gliding.

markz said:

Hate to run out of battery power at 5000 feet

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Not much different than running out of fuel at 5000 feet.

Very different for running out of fuel at 5,000 ft. With aviation fuel, you load 50 gallons weighing 152 kg that gives you 1,700kWh of energy. With electric flight, you carry 152 kg of batteries that gives you 25kWh of energy. Which do you think will run out first?

This is just PR for Magnix. Commercial electric flight cannot happen unless we double the gravimetric energy density to 500 Wh/kg. Elon Musk says 400 kWh/kg. Right now li-ion (e.g. Tesla 2170 and 4680) is stuck at 250 kWh/kg. Has only improved 5% in the past decade.

Solarsail said:

Very different for running out of fuel at 5,000 ft.

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Exactly the same. You are then in a glider.

Actually you are a little better off in an electric vehicle. You can dive the aircraft to recover some energy through regen. Can't do that with a recip or turbine. Nice to still have the ability to stretch a glide if you need to.

JackFlorey said:

Exactly the same. You are then in a glider.

Actually you are a little better off in an electric vehicle. You can dive the aircraft to recover some energy through regen. Can't do that with a recip or turbine. Nice to still have the ability to stretch a glide if you need to.

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“Stretching a glide” and ... “dive to recover energy through regen”... would appear to be contrary concepts ?
How much regen energy could actually be recovered in a >5000ft dive ?? .... ( 1-2 munutes ??)
And all the time the electric aircraft has the same battery weight
..and in reality that battery is probably +_ 1000kg dead weight. !

Hillhater said:

“Stretching a glide” and ... “dive to recover energy through regen”... would appear to be contrary concepts ?

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Yes, they are.

Let's say you are far from an airport. You are then better off in an electric aircraft, since the freewheeling torque from an electric motor is far less than the torque from an IC engine - and it's easier to stop the prop if you want to reduce drag further.

Let's say you are right over an airport. Then you can dive the aircraft aggressively and recover power. That lets you go around perhaps once if you screw up the first approach.

How much regen energy could actually be recovered in a >5000ft dive ?? .... ( 1-2 munutes ??)

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Propeller efficiencies are around 80-90%. Let's say you get an additional 85% from the inverter/battery system and you lose another 20% to drag. That's (.85*.85*.80)^2 = 33% of the energy that you can recover and put back into useful thrust. So from 5000 feet you can attempt a landing, go around at 5 feet off the ground, and climb back to 1600 feet - better than pattern altitude.

..and in reality that battery is probably +_ 1000kg dead weight. !

Click to expand...

Which helps you on the way down and hurts on the way up.

JackFlorey said:

Hillhater said:

JackFlorey said:

Exactly the same. You are then in a glider.

Actually you are a little better off in an electric vehicle. You can dive the aircraft to recover some energy through regen. Can't do that with a recip or turbine. Nice to still have the ability to stretch a glide if you need to.

Click to expand...

“Stretching a glide” and ... “dive to recover energy through regen”... would appear to be contrary concepts ?
How much regen energy could actually be recovered in a >5000ft dive ?? .... ( 1-2 munutes ??)
And all the time the electric aircraft has the same battery weight
..and in reality that battery is probably +_ 1000kg dead weight. !

Click to expand...

Yes, they are.

Let's say you are far from an airport. You are then better off in an electric aircraft, since the freewheeling torque from an electric motor is far less than the torque from an IC engine - and it's easier to stop the prop if you want to reduce drag further.

Let's say you are right over an airport. Then you can dive the aircraft aggressively and recover power. That lets you go around perhaps once if you screw up the first approach.

How much regen energy could actually be recovered in a >5000ft dive ?? .... ( 1-2 munutes ??)

Click to expand...

Propeller efficiencies are around 80-90%. Let's say you get an additional 85% from the inverter/battery system and you lose another 20% to drag. That's (.85*.85*.80)^2 = 33% of the energy that you can recover and put back into useful thrust. So from 5000 feet you can attempt a landing, go around at 5 feet off the ground, and climb back to 1600 feet - better than pattern altitude.

..and in reality that battery is probably +_ 1000kg dead weight. !

Click to expand...

Which helps you on the way down and hurts on the way up.

Click to expand...

Sounds like a passenger seat pilot. Try that in X-Plane or Microsoft Flight Simulator.

I'm not sure what the dive is for. When you're landing you control your airspeed with the nose up or down, your descent rate by running up or down the engine.

Assuming the plane is 5,000ft. AGL (Above Ground Level) for the airstrip you wish to make your engine out landing at, you can assume you have at most 13 miles you can hope to travel to land at best glide speed of 95 knots. Or 11 nautical miles. So you have over 7 minutes. Or do you? Maybe my thinking is too rooted in the Skyhawk. I'm confused by what I'm reading in the emergency procedure, but I should think you're losing around 700 fpm if you're traveling over 9,000 fpm and have a 14:1 glide ratio. But I was reading someone talking about losing 1,500 fpm. ????

There will be no important energy recapture from the windmilling prop. Probably none period, I don't see why they would bother. On the TURBINE engine the prop runs on external pressure, I'm sure that's not part of the electric plane although they COULD use a compressor. That would mean the prop is not even connected to the electric motor and recapture would be impossible.

So the 335 gallons of fuel that is NOT going to be on the plane would be estimated at 2,010 pounds for planning purposes. The batteries can weight that. How much battery power is that? For a 750hp motor that's nearly 600kw. You know they'll expect that commercial flight to land by the time there's an hour of battery left.

I'd feel a bit safer with a small backup redundant battery for a safe emergency powered landing.

markz said:

I'd feel a bit safer with a small backup redundant battery for a safe emergency powered landing.

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As with ebikes, you are always better off making your main battery a little bigger, rather than adding another specialized battery. Having an "emergency" level of discharge is common for EV's already.