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RTH Speed ?
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hallmark007
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There has been much talk about RTH and the speed of craft and how it can manage wind.

The normal speed for RTH is 8m/s approx 18mph , so flying in winds close to or above this speed is going to be fraught with problems, particularly if you are flying out of line of sight and if you lose RC signal you may have trouble getting your drone back home .

Take Precautions.

1/In wind at or above 8m/s 18mph only fly within line of sight and I recommend no more then 300m or less

2/ Always check out area your flying in and find at least 2 locations that are safe to land in emergency

3/ Always have antennas aligned with your craft

4/ Fly at lower altitudes like 20/30m

5/ If you need to use RTH, Remember you can still increase your speed to equivalent of sport mode , you can decrease altitude and change your orientation, only restriction is you can't change direction, your forward speed will be the same as sport mode 13m/s or 30mph, also decent speed will match sport mode 3m/s so long as you are pulling down on throttle.

6/ try to halt craft going to Rth height if wind is going to be to strong at higher altitude, this can be done simply by moving left stick up or down, you can also lower your altitude by using throttle (left stick) in the normal way during Rth mode.

7/ if wind is still to strong, just try to land safely throttle down (left stick) from 30m you will be on the ground in 10/12 seconds .

8/ And most important try plan your flight so you are flying out up wind and back down wind .

Today I tested RTH while using controls test was done in windless conditions and was surprised that I could even get craft to go slightly faster than sport mode @ 14.2 m/s 32mph, I did test in sport only but could only achieve 12.9m/s 30mph.

"SO REMEMBER USE STICKS AS NORMAL IN RTH MODE IN STRONG WIND"

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1-22 09:46
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djiuser_Li0x9INlJfwY
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Could the increase in speed just be down to a tail wind coming home?
1-22 10:16
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hallmark007
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djiuser_Li0x9INlJfwY Posted at 1-22 10:16
Could the increase in speed just be down to a tail wind coming home?

No I don’t think so, I was waiting for a windless day and it came today, I tried from 3 different directions and every time Rth achieved higher speed.
But I believe I know why that is.
In Rth craft will not change direction in any wait stays dead straight for homepoint.
But in sport mode it’s up to you (controller) to make sure there is absolutely no movement in stick when pushed forward, so I think it’s basically down to human error .
1-22 10:27
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Bright Spark
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hallmark007 Posted at 1-22 10:27
No I don’t think so, I was waiting for a windless day and it came today, I tried from 3 different directions and every time Rth achieved higher speed.
But I believe I know why that is.
In Rth craft will not change direction in any wait stays dead straight for homepoint.

If the craft is at full speed in P mode , flying WITH a tail wind speed of 18 mph, , does it do 36 mph ?
Of course  not.
The speed is software governed, and if it shows say 20 mph in these conditions,  is actually flying at 2 mph.
1-22 11:40
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hallmark007
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Bright Spark Posted at 1-22 11:40
If the craft is at full speed in P mode , flying WITH a tail wind speed of 18 mph, , does it do 36 mph ?
Of course  not.
The speed is software governed, and if it shows say 20 mph in these conditions,  is actually flying at 2 mph.

Not sure what your point is, we know speed is governed.
1-22 11:43
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Bright Spark
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hallmark007 Posted at 1-22 11:43
Not sure what your point is, we know speed is governed.

My point is that within no doubt many algorithms, the craft will use it’s speed capabilities to match what speed is requested, so  any additional manual intervention is largely irrelevant.
It will describe a near perfect circle from a ground perspective in any wind within it’s design envelope.
Thus it will (must)  increase speed speed on the into wind section and correspondingly reduce it on the downwind leg. Else how could it perform its   trick shots?
So rth in p mode will result in the  best chance of return unless wind conditions are excessive for it, in which case you should have landed when the wind warnings appeared.
1-22 12:02
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deathsquad
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I watched a video of some guy doing a range test and he lost transmission to the drone due to distance, the drone went in RTH mode but he lost if because of the strong winds. I think the most interesting part of the RTH discussion is the fact you can actually change the mode from P to S while in RTH mode. Handy to know. That is of course if the drone still responds or connects with the controller to take the command.
1-22 12:08
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hallmark007
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Bright Spark Posted at 1-22 12:02
My point is that within no doubt many algorithms, the craft will use it’s speed capabilities to match what speed is requested, so  any additional manual intervention is largely irrelevant.
It will describe a near perfect circle from a ground perspective in any wind within it’s design envelope.
Thus it will (must)  increase speed speed on the into wind section and correspondingly reduce it on the downwind leg. Else how could it perform its   trick shots?

That makes no sense, max speed Rth in P mode is 8m/s max speed in S mode is 8m/s , but applying throttle you can increase Rth speed to over 13m/s . And I believe there is a buffer that can be seen on downwind flight, for instance Mavic 2 is rated at 70kph and have often achieved over this speed in sport mode . You can see below 74kph
1-22 12:14
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hallmark007
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deathsquad Posted at 1-22 12:08
I watched a video of some guy doing a range test and he lost transmission to the drone due to distance, the drone went in RTH mode but he lost if because of the strong winds. I think the most interesting part of the RTH discussion is the fact you can actually change the mode from P to S while in RTH mode. Handy to know. That is of course if the drone still responds or connects with the controller to take the command.

Yes it depends on whether you have signal , and that’s why I recommend if flying in strong wind fly close, less chance of loosing signal and you can see what’s happening, there is no need to change to S mode speed will be there even if your in P mode
1-22 12:19
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hallmark007 Posted at 1-22 12:14
That makes no sense, max speed Rth in P mode is 8m/s max speed in S mode is 8m/s , but applying throttle you can increase Rth speed to over 13m/s . And I believe there is a buffer that can be seen on downwind flight, for instance Mavic 2 is rated at 70kph and have often achieved over this speed in sport mode . You can see below 74kph
[view_image]

It makes complete sense. If taken by the wind to  4 kph over its max of 70 that’s just  c 6 % increase since it has to monitor and correct velocity.
Simply put , it must continually vary speed to hover in anything but wind with zero fluctuation.
This will be  happening at speeds into or with the wind at any speed  from hover upwards.
You may know better, but I opine that DJI will program their drones to use all speed available to satisfy the requested speed, up until of course the design limits are exceeded.
1-22 13:20
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Bright Spark Posted at 1-22 13:20
It makes complete sense. If taken by the wind to  4 kph over its max of 70 that’s just  c 6 % increase since it has to monitor and correct velocity.
Simply put , it must continually vary speed to hover in anything but wind with zero fluctuation.
This will be  happening at speeds into or with the wind at any speed  from hover upwards.

Yeah I agree. If the drone senses it is unable to RTH due to wind speed, it should automatically adjust itself into sport mode or increase speed to RTH.

What actually happens if it is unable to RTH due to wind? Does it just land?
1-22 13:51
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deathsquad Posted at 1-22 13:51
What actually happens if it is unable to RTH due to wind? Does it just land?

It just gets blown away. It will land only when the battery runs out.
1-22 14:02
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hallmark007
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deathsquad Posted at 1-22 13:51
Yeah I agree. If the drone senses it is unable to RTH due to wind speed, it should automatically adjust itself into sport mode or increase speed to RTH.

What actually happens if it is unable to RTH due to wind? Does it just land?

The advice and point of the thread is to educate not to fly ridiculous distances in high winds, I think if you fly safe you have much more options than might think, parameters are already set out for mini and most people don’t seem to have any problems with it, and it’s exactly the same as all dji drones and all other consumer drones you see flying .
1-22 15:02
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Ice_2k Posted at 1-22 14:02
It just gets blown away. It will land only when the battery runs out.

So it will continually try to fight the wind until the battery runs out and force landing?
1-22 16:51
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hallmark007 Posted at 1-22 15:02
The advice and point of the thread is to educate not to fly ridiculous distances in high winds, I think if you fly safe you have much more options than might think, parameters are already set out for mini and most people don’t seem to have any problems with it, and it’s exactly the same as all dji drones and all other consumer drones you see flying .

You are tilting at windmills here, figuratively of course. Let it go.
1-22 20:00
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deathsquad Posted at 1-22 16:51
So it will continually try to fight the wind until the battery runs out and force landing?

Yes, it will.
1-22 20:01
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hallmark007
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GaryDoug Posted at 1-22 20:00
You are tilting at windmills here, figuratively of course. Let it go.

I’ve begun to realize you have very little to offer anyone here, maybe you just go away .
1-23 00:06
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Again that’s not fully correct, it will continue until it looses signal or battery to critical then land.
1-23 00:29
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deathsquad Posted at 1-22 16:51
So it will continually try to fight the wind until the battery runs out and force landing?

Once it enters RTH mode (assuming no further input from the pilot), it will just try to fly towards the home point at 17.9mph (air speed, not ground speed!). If not making any progress due to head wind bigger than 17.9mph, it will just keep doing what it's doing and drift away until the battery eventually runs out and then it will land.
1-23 00:34
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Good advise Hallmark.

I think caution is alway necessary in windy conditions but especially with small drones such as the Mini.



1-23 00:43
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Ice_2k Posted at 1-23 00:34
Once it enters RTH mode (assuming no further input from the pilot), it will just try to fly towards the home point at 17.9mph (air speed, not ground speed!). If not making any progress due to head wind bigger than 17.9mph, it will just keep doing what it's doing and drift away until the battery eventually runs out and then it will land.

Are you sure.?
If it’s hovering in p mode into a constant 18 mph wind, are you saying the application of full forward  cyclic will have no effect at all?
1-23 08:00
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hallmark007
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Bright Spark Posted at 1-23 08:00
Are you sure.?
If it’s hovering in p mode into a constant 18 mph wind, are you saying the application of full forward  cyclic will have no effect at all?

Max wind speed 8m/s Resistance (scale 4)
1-23 09:40
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hallmark007 Posted at 1-23 09:40
Max wind speed 8m/s Resistance (scale 4)

Yes but......
The mini as spark has the capability of 30 mph or so, but that is AIR speed.
P mode offers 18 mph GROUND speed, and could (I don’t say will)  use some or all of that 30 mph AIRSPEED to give this max of 18 mph  GROUND  speed, when into wind.
As I have said before, to describe a circle FROM the ground perspective, in anything other than flat calm, it must continually vary it’s air speed  to give  a constant ground  speed.
Because if not, that would mean , in p mode for example , flying into a 17 mph headwind, only 1mph  GROUND  speed would be left in the bag for progress with full forward applied , which I don’t think is the case.

1-23 10:26
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hallmark007
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Bright Spark Posted at 1-23 10:26
Yes but......
The mini as spark has the capability of 30 mph or so, but that is AIR speed.
P mode offers 18 mph GROUND speed, and could (I don’t say will)  use some or all of that 30 mph AIRSPEED to give this max of 18 mph  GROUND  speed, when into wind.

There is no full forward P mode in Rth whether in P,C OR S mode full stick forward in Rth mode gives maximum speed 30mph .
1-23 10:32
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Bright Spark
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hallmark007 Posted at 1-23 10:32
There is no full forward P mode in Rth whether in P,C OR S mode full stick forward in Rth mode gives maximum speed 30mph .

Yes which into a 18 mph headwind would result in a ground speed  of 12 mph.
And  in p mode for example, when it’s trying to provide g/s of only  18 mph  , it could dig into it’s full  a/s capability to do it.
Any way , I’ve obviously failed abysmally to explain the concept, so  time for a holiday.


1-23 10:43
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hallmark007
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Bright Spark Posted at 1-23 10:43
Yes which into a 18 mph headwind would result in a ground speed  of 12 mph.
And  in p mode for example, when it’s trying to provide g/s of only  18 mph  , it could dig into it’s full  a/s capability to do it.
Any way , I’ve obviously failed abysmally to explain the concept, so  time for a holiday.

No I’m understanding this, but you deserve a holiday, relax and enjoy hope it’s not too windy ;+)"?....
1-23 10:46
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Bright Spark Posted at 1-23 08:00
Are you sure.?
If it’s hovering in p mode into a constant 18 mph wind, are you saying the application of full forward  cyclic will have no effect at all?

Yes, unfortunately I’m sure. It’s a pretty hotly debated topic recently as some members here believe it’s just fine the way it is right now because basically you deserve to lose your drone if you fly in winds that strong. I’m not one of those but it doesn’t matter either way... I guess we’ll see if DJI will decide to do something about this.
1-23 11:25
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hallmark007
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Ice_2k Posted at 1-23 11:25
Yes, unfortunately I’m sure. It’s a pretty hotly debated topic recently as some members here believe it’s just fine the way it is right now because basically you deserve to lose your drone if you fly in winds that strong. I’m not one of those but it doesn’t matter either way... I guess we’ll see if DJI will decide to do something about this.

I suppose when dji do nothing about it, just as they did nothing with spark , Mavic pro, phantom 4, you will then look like the tit you really are .Maybe quit talking out the side of your mouth and grow up .
1-23 11:57
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RTH is a failsafe, not idiotproofing, and you have to treat it accordingly. Failsafe as a concept means that if everything other fails, there's that last little thing designed to minimize harm.
If you have to use RTH something has already gone wrong and that's your last lifeline. As that it's fundamentally a compromise of some sort, not optimized to save the drone from extreme conditions.

My opinion is that the RTH is fine as it is, performing as intended and promised. If however DJI is going to do some alterations, maybe make pilot activated RTH brick the whole drone after landing and charge 50bucks to re-activate it?
Demanding RTH to get everything out of the drone isnthe equivalent of "Remove the redline from my car engine so it can go faster!" It's there for a reason you know...?
1-23 13:14
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Bright Spark Posted at 1-23 10:43
Yes which into a 18 mph headwind would result in a ground speed  of 12 mph.
And  in p mode for example, when it’s trying to provide g/s of only  18 mph  , it could dig into it’s full  a/s capability to do it.
Any way , I’ve obviously failed abysmally to explain the concept, so  time for a holiday.

All DJI models have a fixed RTH speed.  Most are set at 22 mph.  The Mini, being lighter & producing less thrust, is set for 17.9 mph (8 m/s).  No DJI bird automatically flies at maximum speed during RTH.  It's up to the pilot to determine if conditions, along with their skill level, are suitable for launch.
1-23 13:33
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Dirty Bird Posted at 1-23 13:33
All DJI models have a fixed RTH speed.  Most are set at 22 mph.  The Mini, being lighter & producing less thrust, is set for 17.9 mph (8 m/s).  No DJI bird automatically flies at maximum speed during RTH.  It's up to the pilot to determine if conditions, along with their skill level, are suitable for launch.

Please please explain whether the rth speed is set to airspeed or ground speed.The spark( and mini for all I know ) have no airspeed indicator.
1-23 13:52
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Bright Spark Posted at 1-23 13:52
Please please explain whether the rth speed is set to airspeed or ground speed.The spark( and mini for all I know ) have no airspeed indicator.

Our drones use GPS to determine & report speed.  They have no means of directly measuring airspeed.  They report their actual speed relative to ground.
1-23 14:04
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Bright Spark
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Dirty Bird Posted at 1-23 14:04
Our drones use GPS to determine & report speed.  They have no means of directly measuring airspeed.  They report their actual speed relative to ground.

So is it the case that, if you go with a tail wind of  say 20 mph flat out in sport mode, you will see 50  mph on the clock?
1-23 14:14
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Bright Spark Posted at 1-23 13:52
Please please explain whether the rth speed is set to airspeed or ground speed.The spark( and mini for all I know ) have no airspeed indicator.
Adding to this because of another post you made.

There are two settings in the drone firmware for controlling speed.

1 - Max Speed
2 - Max Tilt Angle

For the Mini in P-mode (or autonomously during RTH) the max speed is 8 m/s (17.9 mph).  The max tilt angle is 20°.  Hypothetically let's assume in calm air the Mini can achieve 8 m/s with 15° tilt.  This gives it a 5° buffer to combat a head wind while still maintaining 8 m/s.  Once the wind becomes strong enough, the max tilt prevents it from compensating further.  

The overall max speed/tilt for the Mini (Sport Mode) is 13 m/s (29 mph) & 30° tilt.  Note:  During RTH, applying full forward stick appears to slightly increase max speed to about 31 mph.

The speed is also governed so, even with a tail wind, the Mini attempts to limit itself to the max speed setting.  If you think about it, with an 8 m/s tailwind, the Mini would travel at 8 m/s at 0° tilt.

1-23 14:22
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Bright Spark Posted at 1-23 14:14
So is it the case that, if you go with a tail wind of  say 20 mph flat out in sport mode, you will see 50  mph on the clock?

No because the speed is also governed to remain within the limit.  Early P3 firmware lacked the speed governor, so you were able to achieve cumulative speeds with a tailwind.
1-23 14:27
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hallmark007 Posted at 1-23 00:29
Again that’s not fully correct, it will continue until it looses signal or battery to critical then land.

That is almost exactly what the member asked and then you confirmed it. Why are you being so difficult?
1-23 19:24
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Bright Spark
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GaryDoug Posted at 1-23 19:24
That is almost exactly what the member asked and then you confirmed it. Why are you being so difficult?

Thanks for your explanation.
But it remains odd from my point of view that, since we seem to agree that since the mini attempts to govern its speed to in p mode 18 mph,  30 in s and so on, by ground speed alone, and that it thus checks it when travelling down wind,  it does not attempt to maintain 18 in p mode or rth  by using some or all of its s mode capability.
This may override its p tilt limit, but why not  to aid wind penetration? Correct me if I'm on the wrong tack, but if the speed is still restricted to 18 mph, everything else remains as it should.
If it’s tilt angle is locked to 20 degrees in p, then it’s ability to hover accurately in wind and particularly gusts is also compromised, to no avail,  and you’d be better off staying in sport mode permanently in all respects and at all times, except perhaps in calm conditions for filming or training  purposes.
In short , the 20 degree tilt lock seems unnecessary and debilitating.
The idea should I feel be just to provide  the max requested ground speed.
1-23 23:15
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GaryDoug Posted at 1-23 19:24
That is almost exactly what the member asked and then you confirmed it. Why are you being so difficult?

I’m not being difficult, but I arrive here everyday to a smart quip by you, so don’t be dishing it out if you can’t take it .
1-24 02:24
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Bright Spark Posted at 1-23 23:15
Thanks for your explanation.
But it remains odd from my point of view that, since we seem to agree that since the mini attempts to govern its speed to in p mode 18 mph,  30 in s and so on, by ground speed alone, and that it thus checks it when travelling down wind,  it does not attempt to maintain 18 in p mode or rth  by using some or all of its s mode capability.
This may override its p tilt limit, but why not  to aid wind penetration? Correct me if I'm on the wrong tack, but if the speed is still restricted to 18 mph, everything else remains as it should.
The drone calculates speed via GPS.  The indicated speed is relative to ground or "speed over ground".  

Like all DJI drones, the Mini has recommended limits on the conditions in which it is designed to operate.  If you choose to fly in conditions beyond the stated limits, in particular moisture, temperature, or wind, then there is a risk of crash or loss of the aircraft.

An experienced pilot can employ his skill & knowledge to safely fly in conditions beyond the stated limits, but the drone may lack the capability to successfully maintain position or return home automatically.  In the hands of an inexperienced pilot the risk of loss is greatly increased.  We see this reflected in numerous posts.

Every DJI drone has a limited flight envelope.  None autonomously applies maximum thrust to compensate for inexperience or poor decisions made by the pilot.  The Mini is lighter & less powerful, so the flight envelope & margin for pilot error is smaller.
1-24 05:14
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Dirty Bird Posted at 1-24 05:14
The drone calculates speed via GPS.  The indicated speed is relative to ground or "speed over ground".  

Like all DJI drones, the Mini has recommended limits on the conditions in which it is designed to operate.  If you choose to fly in conditions beyond the stated limits, in particular moisture, temperature, or wind, then there is a risk of crash or loss of the aircraft.

Very fair comment.
1-24 07:43
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