According to the specifications, this quad-copter offers a 90-minute flight time on a 14S-14000mah Li-ion battery.

The propellers being used have a 22-inch diameter and have 8-inch blades and the Maximum Take-off Mass is 8.

Is it possible for such a quadrotor to have a such a high endurance? If so, could you please explain how?

  • 5
    $\begingroup$ Probably better on Drones SE but just look at it from an energy perspective. How much energy does it take to fly 8kg around for ninety minutes? $\endgroup$
    – Jim
    Commented Sep 14, 2022 at 5:15
  • $\begingroup$ It only boasts the 90 minutes at empty weight, or 45 minutes at 7.9kg. But I agree, this isn't an aviation question and is more suited for a drone SE or a battery SE. $\endgroup$
    – Max
    Commented Sep 14, 2022 at 5:22

1 Answer 1


As usual, the simple momentum theory is our friend in these cases:

$P=\sqrt{\frac{T^3}{2 \rho A}}$

Considering that in hover each rotor lifts ¼ of the total weight $W$ and that we have 4 rotors, the needed power becomes:

$P=4\sqrt{\frac{(¼W)^3}{2 \rho A}}$


  • $W=8\cdot9.81=78.5~\mathrm N$
  • $\rho=1.125~\mathrm{kg}/\mathrm m^3$
  • $A=\pi(22\cdot0.0254)^2=0.98~\mathrm m^2$

Substituting the values we get a total power of:

$P=234~\mathrm W$

According to the source, the electrical engines work at a voltage $V=50.4~\mathrm V$. The power of an electrical machine is $P= V\cdot I$, which translates into a current of:

$I=P/V=234/50.4=4.6~\mathrm A$

The battery has a capacity $C=14~\mathrm{Ah}$ and delivering that current it drains after a time of:

$C/I=14/4.6=3~\mathrm h$

This is obviously a maximum theoretical value that does not take into account many factors like:

  • electrical engines are not 100% efficient;
  • some electrical power is used by the onboard electronics;
  • batteries are normally not made deplete completely;
  • for manoeuvring, more thrust and therefore more power is needed than for hovering; but less power is needed in forward flight;
  • simple momentum theory underestimates the needed power of some 15% in hover; and at the typical Reynolds number of drones the efficiency is worse; I'd say that the underprediction might be some 25%.

Factoring in all these points, the given endurance might be plausible.


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