Optimal speed for maximum flight distance efficiency?

[Xcel]

Greetings!

Considering the Mavic is more efficient flying forward compared to just hovering. Has anyone tested what the optimal speed for the Mavic would be if you need to get from point A to B and spending as little power as possible. This would be considering there would be little to no wind.
If you consider a headwind I guess going faster would be better since it would be less time battling against the wind and besides you can't really get anywhere in normal mode if you're up against a fast headwind.


No wind, would it be with:
1) OA on @ 35 km/h
2) OA off @ 50km/h
3) Sport mode @ 65km/h

Or maybe the difference is just negligible?

 

[AlanTheBeast]

Greetings!

Considering the Mavic is more efficient flying forward compared to just hovering. Has anyone tested what the optimal speed for the Mavic would be if you need to get from point A to B and spending as little power as possible. This would be considering there would be little to no wind.
If you consider a headwind I guess going faster would be better since it would be less time battling against the wind and besides you can't really get anywhere in normal mode if you're up against a fast headwind.


No wind, would it be with:
1) OA on @ 35 km/h
2) OA off @ 50km/h
3) Sport mode @ 65km/h

Or maybe the difference is just negligible?

I'm working on this at present. I have to collect some field data and I'll make a presentation on it.

That said, those who have made long distance runs well seemed to have been pinning it in P-mode in 0 wind. One fellow in Thailand used a very consistent 51 km/hr on his 7 km/out and back run.

The hard facts (w/o hard numbers (yet))
1) Maximum range speed is ALWAYS higher than endurance speed regardless of wind direction or speed. DJI give 27 minutes as max endurance at 25 km/hr (0 wind). We don't know if that is perfectly true but it "sounds" right.

(Maximum endurance will be at the speed with 0 wind with the least RPM while maintaining height).

2) 0 wind condition will ALWAYS yield maximum range for a load of fuel in an out and back mission. (The ideal condition)

3) You are right that a headwind always needs more speed to get max range for that wind, so that (in effect) the wind has less time to affect you.
(Put another way: in a 15 knot headwind, if your airspeed is 15 knots, you won't get anywhere!).

4) Likewise a tailwind requires less airspeed than the optimal no wind speed. However, you'll have less time to enjoy it on an out-and-back mission.

5) The caution there is that for a given wind condition, in a round trip, the tailwind benefit will never make up for the headwind deficit for the same wind[1].

6) The above speeds are always faster than the endurance speed regardless of wind speed.

This all comes from the "power curve" which I'll be presenting later this spring once I have the conditions to establish an accurate enough curve.

[1] You could play altitude games: the wind speed will usually be lower closer to the ground and faster higher up. So outbound/headwind/low; inbound/tailwind/high. But, esp. near the ground, wind direction also changes with height, usually veering towards the centre of a low pressure area nearer to the ground.

 

[Xcel]

Nice! Good points you have there. I look forward to your findings. Might I suggest using the same battery when you do your testing in order to rule out differences between batteries.
I'm not really looking into doing any distance records myself, this is more out of curiosity.

One thing to add though, smooth accelerations are probably good for the battery performance overall as well to avoid drawing peak amps and instead accelerating to the desired speed gradually. Anyway this is probably just overdoing and overthinking it

 

[AlanTheBeast]

Nice! Good points you have there. I look forward to your findings. Might I suggest using the same battery when you do your testing in order to rule out differences between batteries.
I'm not really looking into doing any distance records myself, this is more out of curiosity.

One thing to add though, smooth accelerations are probably good for the battery performance overall as well to avoid drawing peak amps and instead accelerating to the desired speed gradually. Anyway this is probably just overdoing and overthinking it

You might find this entirely bizarre but the data collection will only be done in absolute still air. From that the power curve will (with some help from Newton and Leibniz) give us everything we need to know about flight with wind components. The ugly truth is it will be hard, in flight, to determine the wind speed w/o resorting to a table or graph - I'm working on that now but will still need the actual data to fill in and model.

So the battery used for data collection is not relevant - but I'll only use batts from 100 downto 50% level.

You're quite right that smooth is good where battery performance is concerned and not only in the short term - it helps prolong the life of your batts.

 

[AlanTheBeast]

I'm working on this at present. I have to collect some field data and I'll make a presentation on it.

That said, those who have made long distance runs well seemed to have been pinning it in P-mode in 0 wind.

Correction: 51 km/hr for this guy including the climb phase.
(7km out and back).