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Thread: EVTOL... ultralight... I would like to discuss this with interested members

  1. #11
    lnuss's Avatar
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    An excellent observation, Ron. And look at the progress already made, both in aircraft and cars, and in the battery improvements (performance, safety, weight, space taken) in the last 10 years, 20 years, and more.

    Larry N.

  2. #12
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    Didn't Mercedes just test drive their new EV over 600 miles on a charge? I remember a coworker boasting he burned 0 gas driving his Nissan Leaf to work and home, a staggering distance of 36 miles. He could make it to work and back the next day, too. But he had better not forget to charge the car else he'd be walking to the bus stop on day 3. And that was maybe only 7 years ago.

  3. #13

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    Quote Originally Posted by rwanttaja View Post
    I keep seeing this claimed as a major disadvantage of electric aircraft, but just don't see it. A typical one hour flight in my Fly Baby means the plane is ~3% lighter at landing than takeoff. Big whoop. Design-wise, it's actually an advantage...one no longer has to store the "fuel" along the center of gravity, nor take off with a plane whose CG changes in flight.

    I keep imagining a newspaper editorial written in 1904..."The Wrights have invented a ridiculous form of transportation. Not only are the passengers exposed to the elements, they have to lie flat during the entire journey and not move, lest the machine become unbalanced. Though, admittedly, the journeys are short since the machine can only fly a few hundred feet. In comparison, a gentleman traveler may board a train in New York and arrive refreshed in Chicago a day later, enjoying a comfortable berth in a Pullman, dining luxuriously, smoking the odd cigar, a Wright aeroplanist and his ground caravan carrying gasoline, bamboo, linen, engines, and mechanics would be barely approaching the New York State borders."

    Give 'em time, folks. There's a LOT of research going on to improve battery energy density, and it'll trickle down to aviation.

    Ron Wanttaja
    Ron, I do NOT disagree with or question your statements regarding weight shift. I ain't no pilot ner nuthin' - lol The available 'energy per pound' of "fuel" however remains the current chief stumbling block for e-powered flight vs fossil fuel. I was just watching a nifty YouTube about that 9 passenger all electric aircraft in the works. The reviewer made it clear that 9 passengers was the limit because of the nasty battery weight thing. The added weight of more available power to carry more than 9 would actually just be used to carry the added battery weight. here is the vid I referenced -

    https://www.youtube.com/watch?v=b01nE83bmx8

    Again, I have no doubt that 'someday' that wide gap between liquid fuel and the battery WILL move much closer to each other and make many of the present e-dreams a reality. But I'm 73 and doubt it will happen in my lifetime.
    Last edited by CHICAGORANDY; 04-18-2022 at 06:44 AM.
    "Don't believe everything you see or read on the internet" - Abraham Lincoln

  4. #14
    rwanttaja's Avatar
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    Randy, I agree that the energy density in electric flight is the biggest problem right now. But your post was the second one I saw in a couple of days that claimed that "As fuel is consumed the conventional aircraft gets lighter, battery planes stay the same weight" is some sort of drawback, and am curious why folks think that's a problem.

    We're not there *now*, and may not be there next year, but I'm suspecting the energy density issue will be solved, eventually. It's too important to a number of other fields, not just aviation. The automotive arena is the primary one; electric cars used to have a ~25 mile range, but are now commercially available with 400-mile ranges on up. And the infrastructure is expanding, with "quick charge" systems being added to major highways that give a pretty good boost to the battery in the time it takes to eat a burger and visit the rest room.

    As to WHEN it's going to happen for airplanes? I don't see it as being much less than twenty years, which pretty much puts it out of the range where I'll be caring, too. Like many of us, I flew gas-powered U-control airplanes as a kid. A few years before I retired, a co-worker got me into small radio controlled aircraft using electric motors. These were stupendously easy to manage... no big old battery to heat up the glow plug, no hand propping, little noise, and easy throttle control. The little lithium packs were quick to swap out.

    All the homebuilt accident studies I've been running have pointed out how much engine reliability affects the accident rate. Consider what has to work to make a reciprocating engine run...camshafts, valves, spark plugs, carburetors, mixture controls, carburetor heat, piston rings, pushrods, pistons jamming back and forth, etc. The entire structure has to withstand fifty gasoline explosions happening internally every SECOND.

    You have to admire the engineers who can design something that'll handle that. But replacing it with a simple electric motor and controller is sounding like a better and better idea. Shoot, the airlines largely gave up on recips sixty years ago. Turbines are a lot better approach...but, sadly, require levels of precision that tend to eliminate them from consideration for small, light, inexpensive applications like most GA airplanes.

    Just between us boys and girls, I think electric flight is going to be THE SAVIOR OF GENERAL AVIATION.

    "Waaaiit a second there, Ron! Do you really think they're going to replace the engines in stuff like Cessna 172s????!!!"

    Nope. But consider...what's the biggest immediate threat to General Aviation?

    Why, the loss of airports, of course, and the reduction in hangar/tiedown areas.

    Now, step into the Wayback machine to about twenty years ago, and the LAST big idea in personal transportation: The Segway. It was going to revolutionize transportation. No longer would you have to walk everywhere, you could hop on this little self-stabilized platform and zip down the sideways, driving directly into buildings and riding elevators to your destination.

    What happened? Cities were appalled at the idea of these things mixing with pedestrians. They quickly passed laws keeping them off sideways, leaving only the bike lanes, walking paths, and polo fields available (true, Segway polo is a "thing"), and building owners forced the devices to be kept outside. Little advantage over a much-less-expensive scooter.

    So...imagine what'll happen when the current set of personal air mobility devices hit the consumers. Will nextdoor neighbors tolerate the shrieking things leaving for the office at six in the morning? Will cities permit the multibladed devices to land willy-nilly on the streets or sidewalks?

    Not hardly.

    They're going to want to restrict the devices to specific operating areas, to isolate the noise, give room for operations, and provide storage/charging facilities for the devices kept there.

    Airports, in other words. Sure, they don't need 5,000 foot runways, but that's what existing facilities have, and to catch on, the devices have to have places *now* that they can operate from and be stored. Any new airfields implemented aren't likely to have long runways, but the existing ones will be a godsend to the new technology.

    So I'm hoping Black Fly, etc. help take off some of the pressure to close airports....

    Ron Wanttaja

  5. #15
    Eric Page's Avatar
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    Quote Originally Posted by rwanttaja View Post
    ..."As fuel is consumed the conventional aircraft gets lighter, battery planes stay the same weight" is some sort of drawback, and am curious why folks think that's a problem.
    The Holy Grail of electric propulsion research is a battery powered airliner. Let's do a thought experiment, using the Boeing 737-900ER, for which I happen to have performance data.

    We climb to 35,000 feet and arrive at a gross weight of 180,000 lbs. We select a cruise speed of 0.79 Mach and hold that speed until we've burned 30,000 lbs of fuel and our gross weight is 150,000 lbs. As we fly along losing weight the aircraft gets more efficient, which the flight computer uses to reduce fuel burn rate at our constant speed. At level-off, burn rate is 6,842pph but at the end of the experiment it's only 5,554pph (with a 6% total reduction in power setting). That's a change in burn rate of 1,288pph or nearly 21.5 pounds per minute.

    That advantage would not accrue to a hypothetical electric version of the same aircraft; over the course of our cruise segment example, weight remains the same so energy consumption rate cannot decline. To achieve identical payload, range and speed, the electric aircraft would have to have batteries with energy density better than that of jet fuel.

    Whether you call that a petroleum advantage or a battery problem is up to you!

    The next problem is an electric motor/fan no heavier than a CFM56-7B that's capable of ~27,000 lbs of thrust.
    Eric Page
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  6. #16
    rwanttaja's Avatar
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    Good stuff, Eric.

    However, I must gently point out that the subject line refers to ULTRALIGHT electric aviation. People are using the physics that hampers 180,000-pound airliners to justify why electric ultralights won't work.

    Ron Wanttaja

  7. #17

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    Electric ultralight WILL of course "work". Until battery technology makes big improvements, they just can't work for very long. Flight time = battery weight
    "Don't believe everything you see or read on the internet" - Abraham Lincoln

  8. #18
    rwanttaja's Avatar
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    Quote Originally Posted by CHICAGORANDY View Post
    Electric ultralight WILL of course "work". Until battery technology makes big improvements, they just can't work for very long. Flight time = battery weight
    Certainly. However....

    In the past 100 years, how much lighter is one gallon of gasoline?

    In the past 100 years, how much lighter is a battery producing 40 kwh? :-)

    Ron "Where's Moore when you need him" Wanttaja

  9. #19
    Eric Page's Avatar
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    Quote Originally Posted by rwanttaja View Post
    ...I must gently point out that the subject line refers to ULTRALIGHT electric aviation. People are using the physics that hampers 180,000-pound airliners to justify why electric ultralights won't work.
    Yeah, sorry Ron. These threads do tend to wander a bit. My 737 example was in response to the energy density question raised in the WSJ video in post 13, above, and responded to a specific sentence in your post. I typed, then deleted a paragraph about how my example had little application to smaller aircraft (Reader's Digest: same physics, imperceptible effect). I should have left it alone, but I was trying to pare down a long post...
    Eric Page
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  10. #20
    rwanttaja's Avatar
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    Quote Originally Posted by Eric Page View Post
    ....I should have left it alone, but I was trying to pare down a long post...
    Shoot, dude...when has fear of writing a long post ever stopped ME? :-)

    Your stuff is a pleasure to read, and I'm glad you bring your expertise here. It's a refreshing change from guys who say, "I'm agin' it 'cause Joe Smedlap on GoofyTheoryOfTheWeek.com says it'll curdle the milk and bring on global armageddon!!!"

    Ron Wanttaja

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