Sport mode vs normal mode, wich one is more efficient?

[Droning on and on...]

Also, my 2S travels faster than Normal max and slower than Sport during RTH. Try it for yourself.

This I'm highly skeptical of. I have a 2S, I'll go give it a thorough test and post the logs.

 

[mobilehomer]

Oh I have. Many times with different drones. As I mentioned above, my testing experience when doing range tests determined the most efficient speed for maximizing flight distance was between max N and S speeds. RTH returns at less than max N.

So my efforts, somewhat formal, conflict with yours. Didn't see you present any logic really, just some presumptions.

Don't miss my original post - with more than 50% battery left. The less capacity left, the slower the drone goes.

 

[Meta4]

Don't miss my original post - with more than 50% battery left. The less capacity left, the slower the drone goes.

Perhaps this is something new?
It's not what I've seen in the flight data from lots of incidents.
If it wasn't rainy here I'd go and test.
Do you have any flight data that shows this?

 

[sar104]

Yes.

However it is not a parameter in the control loop of the FC. It is simply a configured limit the FC won't exceed, like max height.

And, the vast majority of the time it doesn't come into play at all – it never ends up limiting the FC commanded pitch angle because most people don't fly when it's that windy.

It's as much of a control loop limit as maximum ground speed, and I can assure you that it is a limit that is often reached. It doesn't take much wind to peg the tilt angle on an upwind leg.

 

[Meta4]

Just take a look at the RTH speed using a battery with more than 50% left. The drone will use the most efficient speed.

The algorithm used must calculate the most efficient use of remaining energy to travel the necessary distance safely. Also, my 2S travels faster than Normal max and slower than Sport during RTH. Try it for yourself.

I tested RTH ten times with a Mavic 3 from a range of directions in light winds.
Battery was 100% going down to 60%.
It went close to full speed for Normal Mode each time, unless the distance was <250 metres.
If distance was <250 metres, the speed doesn't get as high because RTH decelerates when the drone is around 100 metres from home.
RTH speed was never more than max speed in Normal Mode.

 

[E.151]

Logic and experience. The algorithm used must calculate the most efficient use of remaining energy to travel the necessary distance safely. Also, my 2S travels faster than Normal max and slower than Sport during RTH. Try it for yourself.

I also note the RTH speed of each type and use that for transiting / repositioning if conserving battery.

This may assist some who are interested to understand more of the detail raised generally in this posting;
a rotary wing experiences the effect of: Translational Lift and Effective Translational Lift (ETL) Out of Ground Effect (OGE).

From <Translational lift - Wikipedia>


This diagram is from a helicopter basic aerodynamics handbook (therefore numbers are different), however, it demonstrates lift vs drag/power effect alongside ETL and supports points some have presented in this post;


Max endurance in this case would be 63-64 Knots, and max range slightly faster and dependant on wind component.

 

[Droning on and on...]

It's as much of a control loop limit as maximum ground speed, and I can assure you that it is a limit that is often reached. It doesn't take much wind to peg the tilt angle on an upwind leg.

I've tested it. Would a flight log help?

Could you approximate a number for "it doesn't take much"? I'd hate to get into a rhetorical argument when we mean the same thing quantitatively.

On the Mini3P I found a significant margin configured to handle wind above the still-air spec'd groundspeed.

 

[sar104]

There have been numerous threads on this subject over the years, and one of the conclusions was that drag dominates aerodynamic lift for small quadcopter. I posted the following derivation and results back in 2018. If you skip the derivation and look at the results, it does show the expected minimum in airspeed/power, which corresponds to maximum range in still air.

The motor thrust (force) vector F, which aligns approximately with the aircraft z-axis, decomposed into vertical and horizontal components at a pitch θ, solves for equilibrium in constant-velocity flight. Ignoring body aerodynamic lift, which is not large for a quadcopter:

F cosθ = Mg [1]

F sinθ = -D = -k₁u² [2]

where M is the mass of the aircraft and D is the horizontal drag, which goes roughly with the square of the airspeed, u.

Eliminating θ ( since cos²θ + sin²θ = 1):

F = √(M²g² + k₁²u⁴) [3]
Power, P, is related to thrust by P² = F³/k₂, which allows us to express power as a function of airspeed:

P = (M²g² + k₁²u⁴)^(3/4)/√k₂ [4]

and the ratio of airspeed / power, which is equal to energy per unit distance, as

u/P = √k₂u/(M²g² + k₁²u⁴)^(3/4) [5]

We don't need to know k₂ to calculate a normalized u/P, but we do need k₁. That can be obtained from the published specifications on pitch angle vs. speed and combining equations [1] and [3].

Mg/cosθ = √(M²g² + k₁²u⁴) [6]
Giving k₁ = 0.033 for the P4P and 0.016 for the MP.

That gives the following relationship between the airspeed/power ratio and airspeed:



These calculations suggest that range for the Mavic Pro is maximum at an airspeed of around 40 mph, with the P4P a little under 40 mph. That's well into sport mode for both those models. I haven't run the calculation for more recent models, but it is fairly trivial to do so.

 

[sar104]

I've tested it. Would a flight log help?

Not necessary - I have hundreds of logs. Here's a fairly recent example. This is a M2P flying into a 5 m/s (~12 mph) headwind, in P-mode. The tilt pegs at 25° with the speed around 13 m/s.

Could you approximate a number for "it doesn't take much"? I'd hate to get into a rhetorical argument when we mean the same thing quantitatively.

See the data above.

On the Mini3P I found a significant margin configured to handle wind above the still-air spec'd groundspeed.

Could you approximate a number for "significant margin"?

It is possible, of course, that the performance characteristics on the most recent model have changed. If you have logs showing ground speed pegged into a similar headwind at less than full tilt then I guess I would be interested in taking a look.

 

[Droning on and on...]

Fabulous treatise, @sar104!! Major props!!

One question: Where do i find this:

the published specifications on pitch angle vs. speed

I'd prefer the data for the current drones I have, but what you used for the MP and P4P would be fine. I have no idea where to find this data, and came up empty with Google.

Could you approximate a number for "significant margin"?

I should clarify that this is in reference to N mode flight. From the log data and my rough estimate of wind on the flight in question, it looks like the Mini3P can do about 40mph airspeed at max tilt, which gives about a ~15mph wind margin at max N ground speed of 22mph (15/22=68%, meets my definition of significant), in S mode about 5mph (5/35=14%, not so much).

See this post for some calcs from the log.

Estimated the wind using visual observation and the Beaufort Scale.

The log's attached. You've analyzed about a million more of these, so I'm quite open to understanding where my analysis/interpretation is faulty.

One thing that got my attention looking at the logs again was a max tilt of ~40° reached flying upwind... You said the M2P pegged at 25°... you go Mini3P

 

[sar104]

Fabulous treatise, @sar104!! Major props!!

One question: Where do i find this:


I'd prefer the data for the current drones I have, but what you used for the MP and P4P would be fine. I have no idea where to find this data, and came up empty with Google.


I should clarify that this is in reference to N mode flight. From the log data and my rough estimate of wind on the flight in question, it looks like the Mini3P can do about 40mph airspeed at max tilt, which gives about a ~15mph wind margin at max N ground speed of 22mph (15/22=68%, meets my definition of significant), in S mode about 5mph (5/35=14%, not so much).

See this post for some calcs from the log.

Estimated the wind using visual observation and the Beaufort Scale.

The log's attached. You've analyzed about a million more of these, so I'm quite open to understanding where my analysis/interpretation is faulty.

One thing that got my attention looking at the logs again was a max tilt of ~40° reached flying upwind... You said the M2P pegged at 25°... you go Mini3P

I'll take a look and see how that compares. Stand by.

 

[sar104]

Fabulous treatise, @sar104!! Major props!!

One question: Where do i find this:


I'd prefer the data for the current drones I have, but what you used for the MP and P4P would be fine. I have no idea where to find this data, and came up empty with Google.

I need to go hunting to figure out where I found those data.

 

[inim civam]

I'm with @slup & @mightypilot2000

Generally speaking drag increases with speed which lowers efficiency.

Saying that I expect there will be a crossover point where the power required to maintain altitude is wasted if going too slow because of the increased hover time. I would roughly estimate that to be less than 3m/s air speed (relative to the wind)

 

[BroomRider]

My discussions with a DJI rep. (Daniel Elson) in another forum, didn't include the variable of winds when considering the speeds to set for the maximum flight times & maximum flight distances for the Mini 3 Pro, & those figures are the same for the Mini 3, their being, from both the Mini 3 Pro & Mini 3 DJI Specs page on their website:

​

Max Flight Time​

Measured in a controlled test environment, windless conditions. Specific test conditions are as follows:

Flying (forward for the Mini 3; not sure if the same applies also to the Pro version, but I'm assuming it does) at a constant speed of 21.6 kph (= 6 m/s or ~13.4 mph). (For the Mini 3, they also stipulated being in photo mode but not taking any photos; not sure if that also applies to the Pro version).

​

Max Flight Distance​

Flying at 43.2 kph (= 12 m/s or ~26.8 mph)

As per Daniel Elson (a DJI FakeBook rep), the RTH speed is 10.5 m/s (= 37.5 kph or ~23.5 mph).

I think that since the maximum flight distance speed is 12 m/s, it seems that you'd get the most efficient speed, & thus distance, per power used when going into Sport mode, & taking manual control to fly back at 12 m/s.

Sensing System (for the Mini 3 Pro)​

• Forward​

• Effective Sensing Speed: Flight speed <10.5 m/s

Since the maximum OA sensor speed is <10.5 m/s, I think that is why the auto RTH speed is also limited to that.

I hope that all that adds some insight.

 

[Droning on and on...]

Thanks for that, @BroomRider!

The one that gets me scratching my head is the RTH speed. Greater than max N speed? That doesn't seem right. Gonna test it today

 

[BroomRider]

Thanks for that, @BroomRider!

The one that gets me scratching my head is the RTH speed. Greater than max N speed? That doesn't seem right. Gonna test it today

Yup, that's what I observed when flying, & watching the RTH specs, & also confirmed by that DJI rep on FakeBook.

I haven't cross-posted this to DJI Forum yet, & I'm heading out to do some fireworks photos & video, but after I return, I'll do that.

Enjoy your flights & CYA!