Fail safe question

[srchadwi]

Hi

I have a question regarding failsafe which I'm sure have been covered before but I can't locate them.

If the bird goes out of range failsafe will kick in and it will start returning home. If it loses satellite link on the way home will it begin to land at its current position? If it does, and it begins to land, but then picks up satellites again will it start returning home again?

thanks

 

[flyNfrank]

It all depends on if you are in naza mode, phantom mode, select failsafe option to land at switch command, select failsafe option to return home. Explain what settings you use and you get a better answer.

 

[Nathan Carter]

It all depends on if you are in naza mode, phantom mode, select failsafe option to land at switch command, select failsafe option to return home. Explain what settings you use and you get a better answer.

Does it really matter? He is asking a very good question actually, one that would be hard to answer because it is a big question if anyone experienced that kind of scenario here. Too bad DJI engineers are not participating in the forum.

Anyway let me try to explain his scenario again:

The phantom got in failsafe mode and is returning to home position. Halfway through, GPS intereference happens and satellite count goes below 6(which will induce switching to ATTI mode), since the phantom now does not know exactly where it is with regards to home point and therefore does not know how to return to it, it will probably just start descending at the very spot it currently is. Now the second part of the question is, if during descent the phantom again acquires more then 6 satellites will it stop descending and resume returning to home point as it initially did.

 

[Miguel]

we understand the question from first post already
makes no sense to repeat a question

 

[Nathan Carter]

we understand the question from first post already
makes no sense to repeat a question

Well I was responding to flyNfrank. He started asking about which flying mode was he in and stating that knowing that would be crucial for providing the answer. Isn't it then only logical to conclude that flyNfrank did not understand the question?

I'm sorry if I'm wrong or if I offended anyone. Not my intention.

 

[singapore_phantom]

Geert, I reckon toggling to ATTI works even if no sat lock is re-established during RTH. Agreed?

 

[N017RW]

Here's a flowchart which covers this as well as some other scenarios:

http://wiki.dji.com/en/index.php/Phanto ... _Flowchart

 

[BlackTracer]

According to that flowchart, there is no path back to "failsafe return to the home point" from "failsafe keep leveling & landing". There is also no path from "failsafe keep leveling & landing" from "failsafe return to the home point".

But we know the craft will "failsafe keep leveling & landing" from "failsafe return to the home point" if satellites drop to < 6.

So the flowchart is incomplete and doesn't answer the question in my opinion.

 

[robinbuzios]

Hi

If it does, and it begins to land, but then picks up satellites again will it start returning home again?

Once it started to land, it will land. However, if the Phantom picks up >6 satellites during the descend then you can easily regain control by toggling the S1 switch. The Phantom will abort the descending and get into a hoover.

Geert./.

Geert, are you absolutely sure of this? I'm going to check on this further, but for some reason I thought that if if regained 6+ sats while in failsafe mode it will resume RTH rather than land straight down. I know you can toggle ATTI to resume, but what about this scenario: you do not have LOS on your bird, AND you have no video/telemetry. Wouldn't you want it to automatically resume its RTH mission if it regains 6+ sats?

 

[robinbuzios]

Here's the excerpt from the "DJI Phantom Vision Summary Guide" which is way more readable than this flowchart. See "2 - Regain Control" ... pretty much explains it all.
BTW Geert is correct.

D- Failsafe (RTH)
You are flying and suddenly you get the “Control Signal Lost” warning followed by “Coming Home” (Meaning
you’ve lost the “First Channel - 5.8Ghz” connection). You’ve entered the Failsafe mode. Phantom tail lights turned
rapid Yellow flashing. Be sure to also check out the “Failsafe” section later in this guide, where you’ll find more
detailed information on what’s really happening during a Failsafe.
When will Failsafe activate?
1-
The Remote Control is Powered off (maybe because of dead batteries) or you have flipped the S1 to the bottom position by mistake or intentionally.
2-
The Phantom has flown out of effective Remote Control range (CE mode ~400 / FCC mode ~800m).
3-
The signal between the Remote Control and the Phantom has been blocked.
4-
There is interference causing a signal problem with the Remote Control.
Need to know: if you flip S1 to Failsafe by mistake, you have less than 3 sec to cancel it by flipping it back up
otherwise Failsafe is activated.
When it activates, you have 2 choices:
1- Let the Phantom do is thing and land by itself:
How it will land depends on GPS Status.
- If GPS is still Active: The Phantom will either stay at current elevation OR raise up 20m/66ft above your
pre-established (auto or manual) home point, whichever is highest, and then make a
straight-line course back to your "Home Point” (Return to home (RTH)), pausing for about
15 sec before descending, land and power itself off.
Need to know: If there are obstacles, buildings or trees in the way when flying at that
elevation on Return to Home, the aircraft WILL hit them on its way back...!
You cannot adjust the Return to Home elevation height, unless you reset your Home
Point. See the “IOC section” to learn how to manually reset the Home Point and why you
would want to do that. The main reason being to effectively avoid crashing into obstacle
higher than 20m/66ft in case failsafe is activated.
- If GPS signal is Lost or not Active: Phantoms simply land straight down. It may be drifting during the descent
and landing process (ATTI mode). I hope you’ve bought some spare props…
Need to Know: The Phantom cannot avoid obstacles during Failsafe. So it might be a good idea to try Regaining
Control as soon as you can.
Need to Know: In FAILSAFE mode, the aircraft speed is really slow and if you are low on battery it may
be an issue! Page 15
2- Regain Control:
This will depend on the position of the S1 switch (GPS or ATTI) when the Failsafe was triggered.
S1 was on ATTI: You will get back control as soon as signal is recovered.
S1 was on GPS: You WILL need to toggle the S1 switch to ATTI once to regain control. If the signal is
recovered, you will get back control; switch S1 back to GPS.
If you do not toggle the S1 switch, you won’t be able to control anything. Why? Because it’s the
“Phantom’s Flight Control System” that controls your aircraft now and land it automatically (it
will not exit the Failsafe mode by itself even if the signal is restored). So remember to switch
S1 from GPS (top) to ATTI (center) then back to top position after you regain control.
(The GPS > ATTI > GPS Flipping Sequences).
Need to know: What will happen if you have manually reset the Home Point way up in the air and Failsafe
activates; will it kill the motor when it reaches the Home Point and crash down?
Not to worry! The Phantom will just slowly descend until it cannot descend anymore. Once it feels
that the altitude is no longer changing for about 3-5 secs, it will turn off the motors.

 

[BlackTracer]

Here's the excerpt from the "DJI Phantom Vision Summary Guide" which is way more readable than this flowchart. See "2 - Regain Control" ... pretty much explains it all.
BTW Geert is correct.

D- Failsafe (RTH)
You are flying and suddenly you get the “Control Signal Lost” warning followed by “Coming Home” (Meaning
you’ve lost the “First Channel - 5.8Ghz” connection). You’ve entered the Failsafe mode. Phantom tail lights turned
rapid Yellow flashing. Be sure to also check out the “Failsafe” section later in this guide, where you’ll find more
detailed information on what’s really happening during a Failsafe.
When will Failsafe activate?
1-
The Remote Control is Powered off (maybe because of dead batteries) or you have flipped the S1 to the bottom position by mistake or intentionally.
2-
The Phantom has flown out of effective Remote Control range (CE mode ~400 / FCC mode ~800m).
3-
The signal between the Remote Control and the Phantom has been blocked.
4-
There is interference causing a signal problem with the Remote Control.
Need to know: if you flip S1 to Failsafe by mistake, you have less than 3 sec to cancel it by flipping it back up
otherwise Failsafe is activated.
When it activates, you have 2 choices:
1- Let the Phantom do is thing and land by itself:
How it will land depends on GPS Status.
- If GPS is still Active: The Phantom will either stay at current elevation OR raise up 20m/66ft above your
pre-established (auto or manual) home point, whichever is highest, and then make a
straight-line course back to your "Home Point” (Return to home (RTH)), pausing for about
15 sec before descending, land and power itself off.
Need to know: If there are obstacles, buildings or trees in the way when flying at that
elevation on Return to Home, the aircraft WILL hit them on its way back...!
You cannot adjust the Return to Home elevation height, unless you reset your Home
Point. See the “IOC section” to learn how to manually reset the Home Point and why you
would want to do that. The main reason being to effectively avoid crashing into obstacle
higher than 20m/66ft in case failsafe is activated.
- If GPS signal is Lost or not Active: Phantoms simply land straight down. It may be drifting during the descent
and landing process (ATTI mode). I hope you’ve bought some spare props…
Need to Know: The Phantom cannot avoid obstacles during Failsafe. So it might be a good idea to try Regaining
Control as soon as you can.
Need to Know: In FAILSAFE mode, the aircraft speed is really slow and if you are low on battery it may
be an issue! Page 15
2- Regain Control:
This will depend on the position of the S1 switch (GPS or ATTI) when the Failsafe was triggered.
S1 was on ATTI: You will get back control as soon as signal is recovered.
S1 was on GPS: You WILL need to toggle the S1 switch to ATTI once to regain control. If the signal is
recovered, you will get back control; switch S1 back to GPS.
If you do not toggle the S1 switch, you won’t be able to control anything. Why? Because it’s the
“Phantom’s Flight Control System” that controls your aircraft now and land it automatically (it
will not exit the Failsafe mode by itself even if the signal is restored). So remember to switch
S1 from GPS (top) to ATTI (center) then back to top position after you regain control.
(The GPS > ATTI > GPS Flipping Sequences).
Need to know: What will happen if you have manually reset the Home Point way up in the air and Failsafe
activates; will it kill the motor when it reaches the Home Point and crash down?
Not to worry! The Phantom will just slowly descend until it cannot descend anymore. Once it feels
that the altitude is no longer changing for about 3-5 secs, it will turn off the motors.

This still doesn't answer part 2 of the OPs question. Very hard to test. Only the firmware knows for sure. It is too bad DJI engineers don't participate in these forums.

 

[robinbuzios]

It totally sorta kinda answers part 2 of the OP's question.

- If GPS signal is Lost or not Active: Phantoms simply land straight down. It may be drifting during the descent
and landing process (ATTI mode). I hope you’ve bought some spare props…
AND
2- Regain Control:
This will depend on the position of the S1 switch (GPS or ATTI) when the Failsafe was triggered.
S1 was on ATTI: You will get back control as soon as signal is recovered.
S1 was on GPS: You WILL need to toggle the S1 switch to ATTI once to regain control. If the signal is
recovered, you will get back control; switch S1 back to GPS.

I agree that it should resume the RTH automatically, but I don't think it does. Now I'm all confused again!

 

[BlackTracer]

Several months ago I was in this privileged situation. :lol:
RTH was triggered about 2.5 km from home point with 7 satellites locked on the Vision app.
Around 2.2 km from home point I tried to regain control by toggling the S1 switch but no response, Phantom was still heading to the home point.
Then I noticed that speed was almost zero and altitude was decreasing from 160 meters. First I was confused because I did not understand what was going on. Then I saw that my satellite reception dropped to only 5 satellites. About a minute later my satellite reception went back up to 7. I am 100% sure about that because my eyes were focused on the screen and I pointed my camera straight down to see where it was going to land. The Phantom did not interrupted the landing with 7 satellites.
At 40 meters altitude I tried again to regain control and it worked. So, yes, I can say that once the landing is started and satellite reception is back to >6 , the Phantom does not elevate again and fly to the home point.

This happened in March/April this year. Firmware version was then V2.0 or V3.0
I went through all the update releases from DJI to check it and I could NOT find any update that changed this.

Geert./.

Thank you for that Geert. And that does answer part 2 of the OPs question.

 

[BWJ]

do you need to be a rocket Scientist, or Engineer to fly that plastic thing. :lol:

 

[BlackTracer]

do you need to be a rocket Scientist, or Engineer to fly that plastic thing. :lol:

Part Rocket Scientist, part Engineer, and part Redneck.

 

[rrmccabe]

Was not aware of the 20 second no GPS autoland function. Good reason to make sure you have lots of satellites if possible as Autoland could be bad. Course better than ATTI with wind blowing

 

[srchadwi]

According to that flowchart, there is no path back to "failsafe return to the home point" from "failsafe keep leveling & landing". There is also no path from "failsafe keep leveling & landing" from "failsafe return to the home point".

But we know the craft will "failsafe keep leveling & landing" from "failsafe return to the home point" if satellites drop to < 6.

So the flowchart is incomplete and doesn't answer the question in my opinion.

Yes I agree - the flowchart is incomplete.

I realise that you can manually take control again if >6 satellites come back whilst the craft is "keep levelling and landing" but it would be nice if it automatically continued to return home in case you haven't noticed the satts have reappeared.

It would also be nice if we could set some warning beeps in the vision app. I live in an area which seems to quite often suffer from low numbers of satellites and it would be very useful if the app beeped when the number fell below 6. It would immediately tell me that I need to take complete of the bird myself.

Thanks

 

[robinbuzios]

Was not aware of the 20 second no GPS autoland function. Good reason to make sure you have lots of satellites if possible as Autoland could be bad. Course better than ATTI with wind blowing

But the "no GPS for 20 seconds" will not by itself will not trigger the auto-land function, right?