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I'm not looking for a precise answer here, just a ballpark estimate of the optimal loiter speed for any model of eVTOL air taxi aircraft. In other words, if you just want to delay (kill time) in the air using the least amount of energy, what is a good airspeed range to fly? I'll take an answer for any eVTOL aircraft type that you know about. If you know the optimal cruise speed, I'd like to know that also. Thanks.

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    $\begingroup$ The answer is going to vary tremendously with the type of eVTOL. For something that is basically just an overgrown quadcopter, with small-diameter fans/rotors, and no wing, the answer is probably zero airspeed. Yet that would not be the case for an actual conventional helicopter (see spinningwing.com/the-helicopter/…), nor for any craft with a fixed wing. So-- I'd say that as asked, the question is so broad as to be basically unanswerable. $\endgroup$ Commented May 21 at 22:34
  • $\begingroup$ I would be very surprised if the optimal loiter speed for a quadcopter is zero. If it were zero for a quadcopter, why wouldn't it be zero for any rotorcraft, including helicopters? The link you provided for helicopters is interesting. As for my question being "unanswerable", why would that be? I said I'd take an answer for any eVTOL air taxi type that anyone here might know about. Just because you don't know the answer, that does not make it "unanswerable". $\endgroup$
    – user36086
    Commented May 21 at 22:59
  • $\begingroup$ The optimal speed to kill time is zero -- zero airspeed, at zero altitude, with zero RPM. Any scenario where "eVTOL air taxi aircraft" are flying around should have ample landing spaces where they can do that. Otherwise, "most efficient" still means discharging their battery at some fairly high rate, just not quite as high as it might be otherwise. $\endgroup$
    – Ralph J
    Commented May 21 at 23:22
  • $\begingroup$ @user36086 do you have a link or a paper about this beaming recharging technology? I've never heard about it and it sounds interesting. Thanks in advance $\endgroup$
    – sophit
    Commented May 22 at 6:27
  • $\begingroup$ ieeexplore.ieee.org/abstract/document/10311170 $\endgroup$
    – user36086
    Commented May 23 at 1:24

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What you are looking for is the speed for minimum power required.

The fundamental difference between types of eVTOL aircraft for this question is whether this particular eVTOL has wings or not.

If it has wings, you will want to be fully transitioned to 'on-wing' flight and have the lifting propulsors in cruise mode. You then want to fly at the minimum power required speed for the aircraft.

If it does not have wings (helicopter, quadcoper, etc). You still want to fly with some forward velocity -- as rotorcraft (even helicopters) fly forward more efficiently than they hover.

To put numbers to this, you will need to build a drag / power model for the aircraft. Search for power required.

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