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If the NASA X-57 uses 12 motors for takeoff, does it need 12 controllers (like throttle levers), or just one?

The traditional way of engine throttle design was 1 throttle per engine, but what if you have 12 engines? Twelve levers would be unmanageable, pushing a quadrant of 12 levers forward on takeoff.

I suppose that on initial setup, you would need a small dial for each prop to sync rpms. More sophisticated electronics could have a feedback loop to do this automatically.

So... what about just 1 controller, and 2 or 3 backup controllers for redundancy as they are electronic and could easily be blown. I'm thinking of a 3 or 4 position selector switch to choose the active throttle, sort of like choosing between magneto 1 and magneto 2 in a typical GA aircraft.

Yes, you could wire the motors up in banks of 4 and have a quadrant of 3 levers, but my specific question is:

Would having just one active controllers for 12 motors be acceptable?

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  • $\begingroup$ Setting up a FADEC system controlling all of the engines would be simpler than adjusting twelve knobs every flight. After all, engines wear at different rates. Your performance will be slightly different for each flight. As far as redundancy, having one throttle per pilot where each controlled all twelve engines would create the desired redundancy. You could even have a primary and secondary FADEC system. Otherwise, a knob, a couple of buttons, or a GUI slider on your glass panel would suffice for backups and save space in the cockpit. $\endgroup$
    – Dean F.
    Apr 27 '20 at 16:25
  • $\begingroup$ From what I understand, the whole point of the "Leading Edge Asynchronous Propeller Technology" setup is that the motors are not synced and that instead each motor constantly adjusts its speed to shape the airflow over the wing into the desired pattern regardless of gusts and crosswinds. So, really, there would be no throttle at all, instead there is a "virtual throttle" where the pilot indicates the desired performance, and the computer figures out how many motors it needs at which power to most efficiently achieve that performance. $\endgroup$ Apr 29 '20 at 10:20
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The need for throttles is to provide a linkage to the carburetor/throttle body in the age when everything was mechanical. The throttle in older airplanes directly controlled the air-fuel mixture allowed into the intake manifolds. If electric motors were used, the throttles would have been attached to mechanical rheostats.

In the age of computer controlled engines/motors, this direct linkage is not necessary. You would essentially just tell the computer how fast you would like to go. The system will take care of the rest.

In most cases, the throttle is retained in the cockpit to provide the human pilot with a familiar interface with the computer. Honestly, in an airplane, where throttle settings and changes are more stable and predictable, a knob or a couple of buttons would suffice. FADEC controlled engines/motors are pretty standard now. The method of inputting your desired controls in a fly-by-wire system is arbitrary. It is just a matter of comfort level with the controls. We might even get to the point of a true GUI cockpit one day.

In the case of a multi-engine electric airplane, you would want at least two controls to account for differential thrust when desired. This is not something that you would absolutely need. But, it would be convenient.

Some very complicated aircraft like the V-22 Osprey rely on the pilot not having direct control over the engine-prop systems. It’s absolutely necessary for a computer system to coordinate the two engines during VTOL operation. The same problem would present itself in a quad-copter large enough to carry human passengers.

As an aside, I vividly remember the first throttle-by-wire car our family ever owned. It was a Hyundai Santa Fe. Though, not difficult to drive. The throttle response took some getting used to. Also, modern electric cars with multiple motors have only one throttle.

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    $\begingroup$ "We might even get to the point of a true GUI cockpit one day." and heaven help you when you're trying to change throttle settings on a touch screen or with a mouse when you're one engine out on short final in rough weather! The fine control necessary for using devices like that can be difficult enough on a stable desktop. Also, moving your hand back and forth between different physical controls in different places with tactile feedback of grabbing an object that feels like the right object is far different than touching the right place on an a completely flat screen. $\endgroup$
    – FreeMan
    Apr 27 '20 at 16:22
  • $\begingroup$ Several questions here about the likelihood of touch screens ever making it into cockpits (other than the iPad for EFB), so not going to get into a protracted discussion here. Just wanted to throw out the thought. $\endgroup$
    – FreeMan
    Apr 27 '20 at 16:23
  • $\begingroup$ @FreeMan - You are right about that. It can be difficult to make inputs into your touchscreen during turbulence in a GA aircraft as it stands today. Anchoring your thumb on the ledge of the screen does help. Having backup knobs and softkeys like the ones currently in use on Garmin, Dynon, and Avidyne units helps even more. Then, there is the full keyboard of a Cirrus Perspective unit. I honestly don’t think that a full GUI system is beyond the realm of possibilities. Is it probable in our lifetimes [shoulder-shrug]? Probably about as likely as the aforementioned quad-copter. $\endgroup$
    – Dean F.
    Apr 27 '20 at 16:34
  • $\begingroup$ @FreeMan - “ Maybe you just want to fly the plane yourself. Well good luck pressing Take Off, then Autopilot, then Land!” - Capt. Carol Burnett $\endgroup$
    – Dean F.
    Apr 27 '20 at 16:45
  • $\begingroup$ @FreeMan - PS. Check out Garmin’s TXi, and other touch screen displays. explore.garmin.com/en-US/txi $\endgroup$
    – Dean F.
    Apr 27 '20 at 18:10
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what about just 1 throttle, and 2 or 3 backup throttles for redundancy as they are electronic and could easily be blown

You wouldn't need separate levers for that: just have one lever driving two or more throttle position sensors.

You might want separate levers for the left-side and right-side engines, so you can use differential throttle control to steer the aircraft in an emergency.

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For a system with so many electric motors, there is an interface that converts what the pilot wants to what those motors need to accomplish to deliver it. Something similar is also seen in some cars' suspensions and aerodynamics (working in tandem to keep the car under control when an inexperienced driver pushes it beyond his or her skills), and even throttle control.

With that said, an issue with that is what I call the "Eclipse Problem" after the throttle issues caused by the FADEC in the Eclipse 500. Main issue is not the FADEC by itself but that the Eclipse has no backup throttle control as it was designed originally to be but a testing platform for the engines. And then someone bought the design and made a general aviation plane out of it.

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