Ampaire Electric EEL Completes Cross-Country Test Flight


Electric aviation company Ampaire took its hybrid-electric Electric EEL prototype on a 341-statute-mile test flight this week. The trip, which the company is calling “the longest flight to date for any commercially relevant aircraft employing electric propulsion,” went from California’s Camarillo Airport (CMA) to Hayward Executive Airport (HWD). The flight lasted 2 hours and 32 minutes and averaged approximately 135 MPH during cruise.

“The mission was a quite normal cross-country flight that we could imagine electrified aircraft making every day just a few years from now,” said test pilot Justin Gillen. Gillen was accompanied by Ampaire flight test engineer Russell Newman for the flight.

Ampaire’s Electric EEL, a converted Cessna 337 Skymaster, is powered by tail-mounted 310-horsepower Continental IO-550 engine and a 200 kW—limited to 120 kW—electric motor in the nose. The company’s second Electric EEL prototype—the aircraft used for this week’s test flight—flew for the first time last month and has since logged over 30 hours in the air. Ampaire plans to conduct a series of Electric EEL flight trials in Hawaii later this year in partnership with Mokulele Airlines and climate change solutions company Elemental Excelerator.

Kate O'Connor
Kate O’Connor works as AVweb's Editor-in-Chief. She is a private pilot, certificated aircraft dispatcher, and graduate of Embry-Riddle Aeronautical University.

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  1. Keep up the good work! America is leading the pack of countries vying for alternative energy vehicles and aircraft. This crucial science will free our population from the yokes of oil cartels and speculators, tax hiking government officials and “Climate Change” whiners. (They’ll find something else to whine about, though…) It’s heartening to see these technologies coming to fruition.

    • I like the tech but ….
      Just because you moved your smoke to the power plant and the battery factory doesn’t mean you’ve saved the world.

      • No, charging a battery can be done with a wind turbine, solar panel, or nuclear power-plant. None of those thng will fill a tank with 100LL. So you are wrong about that one.

        • OK, substitute the total energy and pollution cost of your wind turbines, solar panels, or nuclear plants and there is still NO FREE LUNCH.
          Also, I’m wrong that electrification does not SAVE THE WORLD? Really?

          • Electrification does save the world. It is completely wrong to somehow think all sources of electricity are ultimately just as dirty to the environment as coal. I have to laugh every time I look in the comments section of this website. In a country that invented the airplane, defeated polio, overcame two fascist empires in WW2 and beat the Russians to the moon, we now have a bunch of anti-technology whiners that think every electric airplane project is a waste of time and that global warming can’t be defeated so just shrug and keep belching out CO2 and lead from our obsolete airplanes.

          • “Electrification does save the world”.
            Great to hear that, and a nice strawman argument on the rest.
            Neither of you addressed the battery pack though. Lithium mining, refining, and then the retirement cost and recycling of the old battery packs which don’t last forever. I said at the outset that I liked the tech.

        • Except on cloudy days, windless days, or except in states that have decommissioned radioactive power plants. How is the electric grid these days in California?

          • The grid could be better. Sometimes the allegedly free market interferes:


            “The root cause analysis also faults market mechanisms put in place by the Independent System Operator, a nonprofit corporation that oversees the power grid for most of the state. A program known as convergence bidding, in particular, is meant to help keep electricity prices steady but instead “masked tight supply conditions” during the August heat wave, the analysis concluded.

            Another way markets didn’t function as intended: Energy providers collectively under-scheduled the amount of electricity they expected to need. That allowed power plant operators to sell their juice to customers in other states, resulting in thousands of megawatts being exported even as the Independent System Operator warned that rolling blackouts were imminent.”

      • This tech is under development. The main focus should not be ‘smoke’, which is liberal parlance for Increasing Taxes (If you doubt that, look what Newsom did during California’s recent forest fires. To liberals, tax hikes will ‘save the world’..) This technology will wrest the Middle East from our necks, and free America from having to deal with oil cartels. Every time some Arab mucky muck stubs his toe, we’re informed that we’ll experience “Pain at the Pump”.

      • Could you explain to the unwashed how the Great Lakes were created? He won’t, so I will: Those bodies of water formed after mile-thick glaciers melted when the earth’s climate warmed.

        (And not because Fred Flintstone didn’t get his car smogged.)

        Mankind’s entire cumulative effect upon the Earth’s Climate can be favorably compared to a Mouse Fart in a Shopping Mall. The climate changes, and there is absolutely nothing we can do about it.

  2. It has a tail-mounted 310-horsepower Continental IO-550 however just like ethanol in the fuel, the electric motor makes it kinda sustainable.

  3. A tail mounted 310 hp Continental should provide performance comparable to a 210 Cessna,which is a lot better than 135 mph cruise.

  4. It would be interesting to see what percentage of the power was provided by the Continental as opposed to the electric motor. As Tom W. says, 135 mph is quite slow for a 310 hp engine, especially when combined with electric power. While I believe that electric aviation has a future, it’s hard to believe that the motor up front contributed a huge amount to the flight. The 341-statute-mile “record” sounds more like an electric motor going along for the ride to me.

    • Yep … notice how the write-up conveniently leaves out if the electric motor was running alone or if the piston engine was running and working. It could be calculated how much electric energy would be required to fly the airplane 341 miles purely on electric power … it’d require more energy than the airplane could carry.

      Everyone is so “giddy” that this event occurred but what would the useful load be if this thing was running purely on batteries.

  5. TBO for an electric motor should be outstanding, saving the owner thousands, also the torque curve of an electric motor may allow a fixed pitch prop, saving even more in money and weight.

  6. Climate change has been real for billions of years. Adapt or die. That’s natural. The only reason (science says) we are here is because of successive catastrophic global events and extinctions. Same as it ever was…

  7. Two IO-360 CB’s at 210hp ea = 420hp for an optimistic 160kts cruise speed for a stock C337.
    With a rear mounted 310hp IO-550, the electric motor needs to generate only 110hp to equal stock C337 hp.

    I am not an electrical engineer, but assume a 120KW motor equals to somewhere around 110-120hp. 135mph cruise speed indicates to me they flew a stiff legged flight. I have not spend a lot of time researching YouTube videos on Ampaire. For me, all I have seen as far as promo pictures is this 337 with the gear always down. Hence the 135 cruise speed gear down assumption.

    I would like to see, as well as others have already commented, the time the electric motor actually ran, combined with its overall contribution to this very slow performing 337 from start to finish. Plus, what were the power settings of the IO-550?

    However, kudos for actually flying a prototype rather than the usual artist renderings in addition to virtual computer generated videos that show nothing but the talents of the computer graphics animator. Action speaks louder than words.

    Someone has to be first in any new endeavor. Even if it means this prototype is no faster and a lot less efficient than a 172.

  8. The only function I can see for a hybrid system is to use a fuel burning engine of sufficient size for cruise power as a pusher in the rear for noise isolation; and a small electric engine (better visualization) up front providing the extra power needed for takeoff and climb, which is feathered during cruise. This limits the weight of batteries and takes advantage of the much greater energy density of carbon based fuel and permits use of a lighter weight internal combustion engine running at the most efficient point on it’s power curve.

  9. As slow as this 337 is, Ampaire could have had nothing more than a free wheeling prop like a pinwheel being spun by the forward thrust of a firewalled IO-550. Not being accusatory but maybe some skepticism lurking in the background. Trust but verify.

    • You’re correct. The Mix Master was never that fast to begin with. The one advantage this plane provided was a Center-Line of Thrust, which eliminates the “Critical Engine”. I’ll suggest that was why they chose this design as a test bed; to evaluate their engine without concern for asymmetric thrust. I heard Cessna was going to offer a diesel powered Skylane, but it looks like they dropped that model.

  10. Hi Kate, Everyone’s asking for it; please update us on what was up with the rear engine on this flight and confirm/establish what portion of this flight was powered by the batteries rather than the fuel. Thank you!