Basically what the title says, I have a mini pro 3 and have been looking into what speed is most efficient etc, and I noticed that according to the specs, the drone can hover for 30 minutes, but fly at 21 kph for 34. This doesn’t fit at all with my understanding of aerodynamics or air resistance, surely flying at speed must use more energy than just hovering on one spot not moving at all? Anyone know what could be the reason? At least the specs seem to suggest that the most efficient speed for covering distance is 43 km/h which is the number I was actually looking for, I just got confused by the other specs.
With any rotary wing machine there is a concept called translational lift. https://en.wikipedia.org/wiki/Translational_lift The article talks about helicopters but the concept applies to drones as well. While it may not be talked about, but relating to hovering flight time: If you hovered a drone a few inches off the ground and measured battery life and then hovered it 5 feet up, you would find you have longer battery life with it hovering close to the ground. It’s called IGE vs. OGE hovering. In Ground Effect vs Out of Ground Effect. Source: Former heli pilot (R-22’s)
@Ariya
Thanks, there are so many good answers here
@Ariya
No more answers needed. Above transition speed the rotors are flying; you aren’t just using thrust to stay up. It takes more power to hover than to fly.
@Ariya
Was going to come talk about ground effect but nope, not needed. Out of curiosity (since I’ve started my rotary license). What makes you a ‘former’ pilot? Is it simply no longer your profession, or??
@Ariya
At first read, I thought you were saying translational lift and ground effect were the same thing. Translational lift is definitely an explanation for the OP. Ground effect is another interesting aerodynamic effect but not really related. And as you mentioned, for a craft the size of a drone, you would need to be sooo close to the ground to see ground effect.
When moving, the rotating blades and the body can provide a bit of lift, extending the flight time. Hovering takes the most power as the bird sits in the air without the benefit of moving air beneath it. Flying at high speeds kills any benefits, however, as drag overcomes any advantage from the bit of lift provided otherwise.
@Haru
This seems like a plausible answer; thanks a lot
Also, it gets hotter while hovering. Learned this the hard way by almost crashing to the sea because my mini 3 pro overheated and went for an emergency landing after waiting for sunrise for about 12 minutes (recording 4k60p).
@Mica
That also sounds like a factor that makes sense, especially with li-ion batteries that are used here. I’ve noticed heat affecting the range a lot.
Paris said:
@Mica
That also sounds like a factor that makes sense, especially with li-ion batteries that are used here. I’ve noticed heat affecting the range a lot.
It’s LiPo batteries - they’re lighter and have a slightly higher voltage; also, they get worse until they hit about 40-45°C; after that, it gets slowly dangerous. Also, hovering takes a lot more energy for the flight controller, since it needs to check altitude, GPS, and gyro more frequently for very stable and precise hovering.
Because it’s harder to maintain a constant position than to move from one to the other
Hollis said:
Because it’s harder to maintain a constant position than to move from one to the other
That’s not how Newton’s laws work? Another person gave the correct answer, so it doesn’t matter anyway. Also, according to Newton’s laws, it should take force to move something, and no force for it to stay stationary. That’s the opposite of what you said.
@Paris
Yes, it’s because it’s not staying still like it’s on the ground; it’s being acted on. Just because you liked another good answer doesn’t make mine wrong because I explained less. I said the same thing they did but simpler and without additional explanation.
@Hollis
What is it being acted upon by? DJI quotes all these numbers as being measured at sea level with no wind. There should be no force except gravity acting on it, which is constant no matter the lateral speed. But then again you do seem to be the average redditor, so I will not bother discussing why your answer is too simplistic and doesn’t answer anything; I feel like you just wanted to say something that sounded vaguely logical.
@Paris
Literally any wind, the motion of the propellers.
Hollis said:
@Paris
Literally any wind, the motion of the propellers.
I’m gonna ignore the fact (like you did) that the figures are quoted for a zero wind environment). Wouldn’t that wind or motion of the propellers also act upon the drone when it’s moving? Wouldn’t that neutralize any effect that has? Obviously, I’m joking; someone else has given the correct answer and explained how lift works with autorotation, translational lift, and so on (surely that’s what you meant). I don’t know why you keep trying to make your drastically oversimplified answer work, but you do you.
@Paris
Drastically oversimplified doesn’t make it wrong, lol.
Hollis said:
@Paris
Drastically oversimplified doesn’t make it wrong, lol.
So 1. of all, none of your subsequent answers have made any more sense or explained it better than the first one. 2. Your answer was useless because it doesn’t explain anything; it literally just states what my question was. I asked ‘why does the DJI drone use more battery to stay still than to fly around?’ and your answer is ‘because it uses more energy to stay still than to fly around.’