Electric RC Plane Flies For Almost 11 Hours

Electric RC aircraft are not known for long flight times, with multirotors usually doing 20-45 minutes, while most fixed wings will struggle to get past two hours. [Matthew Heiskell] blew these numbers out of the water with a 10 hour 45 minute flight with an RC plane on battery power. Condensed video after the break.

Flight stats right before touchdown. Flight time in minutes on the left, and miles travelled second from the top on the right.

The secret? An efficient aircraft, a well tuned autopilot and a massive battery. [Matthew] built a custom 4S 50 Ah li-ion battery pack from LG 21700 cells, with a weight of 2.85 kg (6.3 lbs). The airframe is a Phoenix 2400 motor glider, with a 2.4 m wingspan, powered by a 600 Kv brushless motor turning a 12 x 12 propeller. The 30 A ESC’s low voltage cutoff was disabled to ensure every bit of juice from the battery was available.

To improve efficiency and eliminate the need to maintain manual control for the marathon flight, a GPS and Matek 405 Wing flight controller running ArduPilot was added. ArduPilot is far from plug and play, so [Matthew] would have had to spend a lot of timing tuning and testing parameters for maximum flight efficiency. We are really curious to see if it’s possible to push the flight time even further by improving aerodynamics around the protruding battery, adding a pitot tube sensor to hold the perfect airspeed speed on the lift-drag curve, and possibly making use of thermals with ArduPilot’s new soaring feature.

A few of you are probably thinking, “Solar panels!”, and so did Matthew. He has another set of wings covered in them that he used to do a seven-hour flight. While it should theoretically increase flight time, he found that there were a number of significant disadvantages. Besides the added weight, electrical complexity and weather dependence, the solar cells are difficult to integrate into the wings without reducing aerodynamic efficiency. Taking into account what we’ve already seen of [rcflightest]’s various experiments/struggles with solar planes, we are starting to wonder if it’s really worth the trouble.

44 thoughts on “Electric RC Plane Flies For Almost 11 Hours

  1. If you’re gonna do that to your LiPo’s, you might as well just use disposable batteries. Higher energy to weight and it’ll be cheaper than destroying expensive lithium cells every flight.

      1. Part of the trick here is the custom Li-Ion pack. LiIon packs more power per gram than LiPo, but it has (per cell) a lower max current delivery. Here, he’s gotten the planes efficiency high enough that it cruises on what the batteries can put out, which lets it run a long time.

        There’s some clever optimization going on here. And all that with a stock, if slippery, airframe. Pretty cool.

          1. I’ve been active in the electric RC revolution from the beginning. Lipos and brushless motors were huge gamechangers. I also used to think the same thing but recently changed my mind after obtaining some of the more recent lion cells. Yes, Lipos do have higher current capacity but there have been huge gains with the latest lion cells. Lipos are still used in most RC applications when high loads are needed but lions are being used more and more for moderate or endurance type apps.

            Check out the specs on this 21700 cell https://www.18650batterystore.com/collections/21700-batteries/products/molicel-p42a. These aren’t hyped ratings either.

          2. Chris: that’s about 12C rated cell, while modern LiPo batteries go up to 280C which is absolutely ridiculous – you could pull a thousand amps out of the battery.

    1. >powered by a 600 kV brushless motor turning a 12 x 12 propeller. The 30 A ESC’s low voltage cutoff was disabled

      yeah… 600.000V makes no sense at all. maybe 600W?
      The ESC’s are rated for 30A and a 4S accumulator has nominal voltage of 14V (? not sure).
      -> 30A*14V=420W

      1. kV is RPM per Volt of Back-EMF. ie, the voltage the motor will produce when freewheeling. 600kV will be a relatively slow motor, but very torquey, if I’m remembering right

    2. Admittedly when I came across that notation a few years back, I initially thought KV, as in kilovolts, needless to say, I was scratching my head for a few minutes before looking it up.
      Damn confusing, especially for those with a prior interest in high voltage equipment. Note, those motors don’t need many volts to spin quickly, but they can draw a lot of current.

    1. thx for the link – interesting read.
      but why don’t you, Eric, “they” (as in RC enthusiasts) type K_v instead of Kv? Isn’t the underscore a quasi standard for expressing subscribed letters in scientific formulas (in normal text without special formatting)?
      It would prevent a lot of potential confusion.

  2. Whats the big deal here? that this thing runs from battery instead of solar panels and solar power is soooo bad? You know you can get paint these days which acts like a solar panel and just paint it on the plane to harvest energy

      1. 20 % efficiency of a regular solar panel or 20% of the available solar energy which is about all a solar panel gives in the first place. The other 80% is reflected back and or converted to heat which reduces the output of a solar panel anyway. There are panels that have cells on both sides now to increase output but kind of hard to make that work in this app. for sure a lose of dynamics.

      2. You could always use the bare solar panels as a physical part of the wings and not just stick them on top. Add spars and braces above and below, then shrink wrap the whole thing in clear plastic. Even perhaps coat them in clear silicone sealant to make the aerofoil shape, although that may prove too high density.
        You can buy, “offcuts” and broken panels online pretty cheaply. Stick them to a thin rubber sheet and solder them together with some enameled copper wire, then you could wrap them around the curved shape of the wing, probably cheaper and more electrically efficient than buying the new “flexible” solar panels.

  3. I seem to recall from the very dim and distant past (early ’90s) that there’s a competition class for this? A work colleague was into it at a national level back then. Of course, battery tech has come a -long- way since then!

  4. If we are playing “what about”, then what about making a secondary recharge aircrafts that allow an unlimited range for it? Or even doing a battery swap mid air? I’m thinking magnetic terminals that allow easy connect/disconnect with poor alignment.

  5. Well done. Thanks for the inspiration. Interesting to note that as the battery voltage drops the current needed to fly goes up. I think that a lot of up draughts helped achieve that flight time but still a great achievement.

  6. I think this is going to be the next frontier, honestly, and maybe we’ll see it get started in the next 5 years. It’s very hard, though.

    Personal bet: more instrumentation / sensors on the plane will be key. Full-scale / human-carrying glider pilots have windspeed + altimeter that lets them figure out their total energy. They also have a telltale or “yaw string” that lets them know when they’re side-slipping in turns. Most model planes lack even these basics.

    Thermals are also a hell of a lot bigger and more stable up where full-scale gliders fly. The stuff under 100 m is significantly trickier: turbulent and transient. The models simply have to be that much smarter.

  7. Whoever wrote this arrival has never flown a hobby RC plane. 2 hours? Try 5 to 10 minutes… that the typical run duration of hobby grade electric model aircraft.

    Some people have achieved an hour+ in custom setups build for duration challenges but if you walk into your local shop and buy something from E-Flight or Horizon Hobby you are not getting anywhere near that.

  8. Why didn’t you use dilithium crystals, like on the enterprise? Oh pleeeeease. All these “you should have done it this way” comments are just pulled out of your left ear. Just appreciate what the man did at face value. Well done, dude!!

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