High wind and RTH

[sar104]

Is greater speed in S mode achieved only with greater tilt angle, or motors run faster also?
Considering that tilt angle is the same for C and P mode then different speed is probably achieved with different motors speed.

No - and that would be physically impossible. Motor speed and tilt angle are not independent variables in controlled flight. Motor speed determines total thrust, and the vertical component of that thrust must equal the weight of the aircraft for level flight. The horizontal component of the thrust then determines the airspeed.

So the tilt is changed to add horizontal thrust and then the motor speed is adjusted to make the vertical component balance the weight.

The maximum tilt and maximum speed are different limits. The 20° maximum tilt in C mode is to allow it to resist wind, not to achieve the same ground speed as in P mode.

 

[sar104]

Just too elaborate a bit out from the Mini specs that sar104 attached ... & in manual control

The priority here (kind of), between the tilt angle & max speed ... is speed.

If flying with a moderate wind in for instance P-mode the AC will keep a max ground speed of 8m/s ... and keep it there by significantly lowering the tilt angle. The AC will not, in this case, utilize the full tilt of the available 20 degrees ... which would lead to a higher speed then spec.

If instead letting the AC fight a headwind it will again try to reach the speed of 8m/s ... but depending on the headwind the AC will utilize a steeper tilt, once reaching max speed the AC will settle with that needed tilt angle ... which can be less than the maximum 20 degrees.

If the headwind increases, the AC will further increase the tilt angle ... if needed, all the way to max 20 degrees. If max speed then isn't reached, the AC will remain with max tilt of 20 degrees but the speed will be lower than those max 8m/s.

With a still increasing headwind, with the AC tilting to the max, the AC eventually stops full fighting & if wind is strong enough the AC will start to drift down wind with full 20 degree tilt.

If going with Sport mode exactly the same will happen but the speed & tilt specs will be different ...

When RTH is activated the same behavior will repeat as described above with specs equal to P-mode.


As a side note ... & for time being, only for the MA1 which I fly with.

The specs for the MA1 in
P-mode: max 8m/s, max 25 degree tilt
Sport mode: max 19m/s, max 35 degree tilt

With manual control you can think that it wouldn't tilt more then 25 degree in P-mode to achieve the 8m/s speed ... but it does. Even though in P-mode & not manage to achieve the prioritized max speed of 8m/s due to a headwind ... it starts to utilize tilt angles steeper than the specified 25 degrees in order to maintain the speed to P-mode spec.

This was unexpected & came as a surprise when I first saw it in the flight log ... but have since then seen it repeatedly, the MA1 utilize Sport mode tilt spec in P-mode but only up to reaching the specified max speed of 8m/s. Have not a clue if this behavior is used in RTH also ... or if this applies to other DJI models.

And it's also a lesson learned for me ... because if I'm in P-mode trying to fight a to strong headwind & can't make way, the tilt is probably already utilizing the Sport mode tilt of 35 degrees ... & by switching to Sport I doesn't gain anything, the only tool a have left then is to drop height!

That's either a programming error or incorrect specifications if it really is exceeding 25° in P mode.

 

[slup]

That's either a programming error or incorrect specifications if it really is exceeding 25° in P mode.

Yeah... but it's what my logs show, both the txt & the dat so it is no mismatch them between. Don't know if you remember but I sent you a PM with the log the first time I saw it. Usually the AC doesn't jump over to sport mode tilt angles immediately, it starts with a heading speed that not fully can reach 8m/s during a couple seconds, then it tilts down & the speed picks up and stays at 8m/s. Sometimes I have seen it in the live view as the props suddenly have been visible in the view. I'm on the latest firmware...

 

[sar104]

Yeah... but it's what my logs show, both the txt & the dat so it is no mismatch them between. Don't know if you remember but I sent you a PM with the log the first time I saw it. Usually the AC doesn't jump over to sport mode tilt angles immediately, it starts with a heading speed that not fully can reach 8m/s during a couple seconds, then it tilts down & the speed picks up and stays at 8m/s. Sometimes I have seen it in the live view as the props suddenly have been visible in the view. I'm on the latest firmware...

Of course I remember, now that you mention it...



That is certainly 35° tilt in P mode, although only 8 m/s speed which is the P mode maximum. My Mini doesn't exceed the specified 25° in P mode, so I wonder what is going on there.

 

[slup]

... just checked the specs for the MA1 and they state only 15deg max tilt in P mode. I, too, had it in my head it was more than that. DJI Mavic Air - Specs, Tutorials & Guides - DJI

It's wrong in the specs stated on the web ... in the complete downloadable manual they state the correct angles ... & I have of course confirmed them through the flight logs ?

 

[scro]

It's wrong in the specs stated on the web ... in the complete downloadable manual they state the correct angles ... & I have of course confirmed them through the flight logs ?

Aha, that explains it then. 15deg didn't seem like enough tilt for P mode.

 

[Deleted member 103366]

Ok, yesterday it was calm and I put the mini up to get some hard evidence of what I am seeing, the following are screen captures on my PC from the screen capture video.
01 to 03 are during the solely automated process. I pushed the right stick fully forward immediately after 03.
04 was the peak speed reached, I guess ther was a little wind as the speed dropped off to between 13.8m/s and 13.9m/s there after.
I began to ease off on the right stick just before 05
The screen recorder running time is visible in the orange blob.
What was quite surprising was the way the battery life indicator (top right) was up and down like a yo yo during the various phases of the flight.
These shots are not faked.
You may need to view them 'full screen' to see the speed and distance indicators

 

[scro]

I have recently played with the parameters on my MM and have now had the chance to properly test these effects. I increased the allowable tilt to 40deg, and in sports mode I saw 14.4m/s achieved, but with a tilt of just 17.3 deg. This is the first time I've seen anything more than 13m/s even when flying downwind in strong breeze, and even more interesting to note that it didn't require even close to 30deg. Even on initial acceleration it didn't quite reach 30deg tilt.

For reference, motor speeds were peaking at around 14500, and typically around 12800 when sustaining 14.4m/s for around 15sec. There was about 6m/s tailwind (from the wind estimate in the logs)

 

[Deleted member 103366]

CsvView plot from the above flight