RTH altitude above max - nearly lost my quad.

[CrowsFeet]

and if the software should be altered to reduced the RTH height to below the floor of a restriction since the restriction is now being shown as the maximum height limit.

I believe this is what should be done.

 

[CrowsFeet]

But that's just it. It did NOT automatically fly into a restricted zone! It stopped at the boundary.

I may be missing something here. But the drone was ok when it when into RTH. It was below the restricted zone. Is that part right? I was at 60m. Outside of a restriction, but below a restricted zone.

It then rose, automatically, to 65m. Therefore, into a restricted zone. So it flew into a restricted zone. (This is my issue).

Yes. The max RTH was 65. But how did it allow 65m to be the RTH return altitude - when I started my flight in a 60m restricted site? This is the issue. I never set 65. Maybe I did in a previous flight (I don’t recall doing that). But surely when the drone sets the max height to 60 - it must set the RTH to 60 or below.

So 2 issues - I believe. It should not have allowed a 65m RTH Alt when it automatically set the max Alt to 60. AND - it flew me into a restricted zone due to this.

I was unable to fly in any direction. See sticks. I turned around to fly away. I moved in all directions. It felt like it was in the restricted zone. So all right stick movement was stopped.

 

[bkushner]

I've had this issue repeatedly. I fly where there is a bridge. I can't be about 140 or I won't make it under the bridge. My RTH is set to 115. Anytime I want to return home it rises to 140 or more before returning.Not good.

 

[scro]

As @Zbip57 pointed out, when RTH was initiated the drone had been flown far enough out to sea so as to be  outside the 60m height restriction zone youd taken off in, so the drone could legitimately rise up to 65m for RTH, as it was set to do.

However, as the drone started to return to you at 65m, it hit the edge of the 60m restriction zone and got stuck. The right thing to do was to lower altitude to 60m or less and then the RTH could continue.

Theres no bug to report here, but there is a valuable lesson to learn on the criticality of setting a good RTH height for each flight. Too low, and the drone might hit something. Too high and it could get blown away or get snagged on height restriction zones. I often fly at the edge of a 60m zone, so your experience here has been useful learning for me. Good you got your drone back just in time!

 

[Yorkshire_Pud]

No, you weren't. That's the whole problem. Zoom in on my image in post#11 above.

Thanks for the explanation @Zbip57, it clears up something I was uncertain about.

However I am left with the nagging question/concern relating to RTH height and the maximum height.

Since the drone took off under the restriction-zone and, since, according to the log, that temporarily reduced the drone's maximum height limit to the height of the floor of the restriction zone. Would it not be an 'good' idea for that reduction in the maximum height limit to be made 'permanent' or for it to simultaneously but 'permanently' reduce the set RTH height to match the temporary maximum height limit?
I think 'permanently' reducing the maximum height limit would be the safer of the two since any attempt to fly up high would draw the pilots attention to a change in settings.
The above would avoid the danger of the drone running into the wall of the restriction zone and getting 'stuck', unless the pilot made suitable changes after getting out from under the restriction zone.

Yes I can see that there could be problems with that approach too.
In another place and after getting out from under the restriction zone the planned flight might be up hill and that might require the pilot to manually reset the maximum height limit and or the RTH height once the drone was in unrestricted airspace.

 

[Yorkshire_Pud]

t then rose, automatically, to 65m. Therefore, into a restricted zone. So it flew into a restricted zone. (This is my issue).

As I understand Zbip57's post #20, the drone did not climb to RTH height through the floor of the restriction zone. It climbed to RTH height in unrestricted airspace and then flew horizontally in to the side wall of the restriction zone.
The log suggests that whilst in that unrestricted airspace the maximum height limit had been 'returned' to the height that you, at some point prior to the flight, had set to 65m.

Attached is an awful zoom of Zbip57's restriction zone map but I think it can be seen that the RTH climb occurred in unrestricted air space.
If you drag the Phantomhelp slider to timestamps 18:49.6 and 23:21.8, where the maximum height limit changes in the log, I think you will be able to make out that those points roughly correspond with the border of the restriction zone.

 

[TwoSticks]

As I understand Zbip57's post the drone did not climb to RTH height through the floor of the restriction zone. It climbed to RTH height in unrestricted airspace and then flew horizontally in to the side wall of the restriction zone.
The log suggests that whilst in that unrestricted airspace the maximum height limit had been returned to the height that you at some point prior to the flight had set to 65m.

Attached is an awful zoom of Zbip57's restriction zone map but I think it can be seen that the RTH climb occurred in unrestricted air space. If you drag the Phantomhelp slider to timestamps 18:49.6 and 23:21.8, where the maximum height limit changes in the log I think you will be able to make out that those points roughly correspond with the border of the restriction zone.

In post 3 that is what I mentioned and it's not a new issue. It has always been the case that you can run into a software height restriction with DJI that will cause what happened here. It will not automatically drop to the proper height to follow the shelf, it will simply stop because it ran into the restriction. In my previous post where you felt I misunderstood you maybe I did but my point was and still is, you need to set your max elevation and RTH at take off based on the lowest restriction for the area you're flying. It will avoid this issue. That said, I think it should be up to me and if I break the rule that too is on me as the one in charge but I get it. In order to stay in the good graces, DJI will do what they can to say they tried to prevent an issue. I agree with you it should be smarter and manage the RTH knowing there is an area restriction and fly under.

 

[Yorkshire_Pud]

I don't know about anyone else but I think this is a great thread, very educational.

 

[Zbip57]

I may be missing something here.

Evidently.

Here, I hope these clearer illustrations will better explain what's going on.

This is from DJI's Fly Safe Geo Zone map. The Blue circle is an Authorization Zone around the airport. You say you acknowledged that and self-authorized to cancel that GEO warning, so you were good to take off from the beach within that Blue zone. By clicking on that self-authorization you are acknowledging that you've been warned and that you take full responsibility for any subsequent consequences of your actions.

Part of your flight went north up the beach, outside of the Blue zone but you were allowed to return back again inside the Blue zone for the rest of the flight. I guess, once self-authorized, that restriction is unlocked for the remainder of the flight. No issues there.

Where you ran into trouble is with the Grey fan-shaped 60m Altitude Zone extending out from the airport's runway. Taking off from the beach, you're flight was under that 60m ceiling. No problem, as long as you remain under 60m whenever flying beneath that defined Altitude Zone.

I highlighted the Altitude Zone with red lines to make it easier to see the edges. Note the two landmarks in the yellow circles. The edge of the Altitude Zone crosses directly over the end of that pier.



Next, transferring those Red lines onto the PhantomHelp map showing the path of your flight, you can see that the portion of your flight circled in Yellow extended out past the edge of the Altitude Zone. Out there the Altitude Zone restriction is not applicable, and you are no longer restricted by the 60m ceiling.

When your low battery RTH was initiated, the drone climbed as normal to its configured 65m RTH height and then headed for Home. That's fine out there in the unrestricted airspace, but then it almost immediately encountered the outer edge of the Altitude Zone. You're not allowed to cross into that area at any height higher than 60m, so the drone was stopped by the GEO zone and prevented from entering the restricted space.



Had you configured your RTH height beforehand to anything less than 60m, the drone would have happily returned to home automatically crossing unrestricted below the 60m ceiling of the Altitude Zone. Or, as you eventually did on your own, manually lowering the drone to less than 60m allowed you to bring the drone back beneath the 60m Altitude Zone.

You're lucky that you figured that out before the drone depleted its battery and fell into the sea. Kudos to you. Other people have lost their drones in similar situations.

Yes, it would be nice if DJI drones were programmed to realize they could automatically descend to cross below the Altitude restriction. But other scenarios can be more complicated. People have flown their drones to circle around and beyond the far side of no fly zones, then lost control signal. The straight-line RTH path crossed the no fly zone and the drone was left stranded on the far boundary edge, unable to return.

If there are any GEO zones within potential range, the app will warn you when taking off to check the map and be aware of the potential consequences related to RTH.

- Aircraft in Altitude Zone (60 m). Fly with caution)
- Current RTH route close to GEO Zone(s). Pay attention to the aircraft's position on the map to avoid RTH failure).

Those GEO zones are clearly indicated on the Fly app map.

 

[Zbip57]

I suspect you saw the influence of the restriction zone on the maximum height limit and not the 'real' height limit as set by you at some previous time.
From 18:49 to 23:21 the log show the maximum height limit to be 65m 213ft, from there on it drops to 60m 197ft, both changes occur around 1300ft from the home point. From 23:21 onwards the maximum height limit is 60m 197ft.

I agree.

I think his Max Height limit (and RTH height) setting was always configured to 65m in the app. While the drone was flying below the designated 60m space of the Altitude Zone, the Max Height recorded in the log switched to 60m to prevent the drone ever climbing higher than allowed. But when the drone flew out beyond the designated zone, out from under that ceiling restriction, the Max Height reverted to the configured 65m setting.

Check column-DW in the CSV log file: "MC.atAirportAltitudeLimit"
When the drone is flying beneath the Altitude Zone space, this shows as TRUE.
At 18:49, when the drone emerges out from under the edge of the zone, it switches to FALSE.
At 23:21, as the drone slides under the zone again, it switches back to TRUE.

Apparently it knows when it is safely flying below the hard ceiling where an Altitude Zone starts.

But whenever it is flying outside of the Altitude Zone, nothing prevents it from climbing higher than the 60m restriction, which makes sense. If it then flies toward the edge of that restricted zone at any height greater than 60m, it treats it like any other GEO zone which stops the drone at the boundary and prevents it from entering the restricted space.

It's up to the pilot to take corrective action to navigate around any restricted space. But, you may be out of luck if you've lost control signal and are no longer able to steer the drone. That's why you need to be aware beforehand of the location of any GEO zones and consider how those might affect potential RTH paths.

 

[Suren]

Reading this thread I am curious as to why the Mavic 3 will if outside a height restriction zone and in RTH, drop its height automatically when it reaches the zone and continue its RTH with no stick input from the pilot but the Mini 3 Pro does not. I will give this a try like I did with my Mavic 3 and post back. Below are the flight logs from a test flight I did today to test this theory, I have flown this path many times and the drone behaviour is always the same, reach Height zone, I lower to 59 meters, out of height zone, I go back to 70 meters then I hit RTH, drone comes back at 70 meters till it reaches height zone, drops altitude on its own and comes home.

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

 

[Yorkshire_Pud]

Different programming perhaps.

 

[Suren]

Different programming perhaps.

Could be

 

[Yorkshire_Pud]

That's quite a steep descent, cool.

 

[Droning on and on...]

That's quite a steep descent, cool.

Really?

Every drone I've ever owned has been able to descend vertically. Unremarkable.

Not following you...

 

[Yorkshire_Pud]

Every drone I've ever owned has been able to descend vertically

Strangely so do mine.

Not following you...

I mean that, for an automated descent whilst moving horizontally it descended quite steeply.
It loses around 40ft of height in around 61 horizontal ft and around 8 seconds, that's a descent slope of around 33°, isnt it?
Personally I think that's quite steep.
The automated power saving descent slope of the Air 2s is 14°.

 

[Zbip57]

Interesting, did you MANUALLY change the maximum height limit during the flight?
You log shows a behaviour I have NOT seen before and, in my flying, has been IMPOSSIBLE.
If you down load and open the csv of the log you will be able to see what I am taking about.

Column EC shows what I believe to be the max height ceiling "HOME.heightLimit [ft]", at the start of the flight it was 196.9ft / 60m but at timestamp 18:49.6 it changes to 213.3ft / 65m BUT throughout the flight the RTH height, column EP "HOME.goHomeHeight [ft] is 213.3ft /65m.

This is interesting.

Both his RTH height and Max Height were configured to 65m. But his takeoff point on the beach was covered by the 60m Altitude Zone, and column-EC of the log shows the drone's max height was automatically reduced to 60m to avoid ever hitting that GEO ceiling.

But, as we've since figured out, when the Mini 3 Pro emerged out from under that Altitude Zone, beyond the edge of the defined zone, the max height setting automatically reverted to the originally configured 65m. When the low-battery RTH kicked in, the drone climbed to its configured 65m RTH height and then flew toward Home before bumping into the outer edge of that Altitude Zone. Because it was now higher than the allowed 60m Altitude Zone limit, that GEO zone stopped the drone at its boundary.

The Mini 3 Pro evidently isn't smart enough to automatically descend to safely return underneath the Altitude Zone. Why is that? Anywhere within or underneath the defined Geo zone, it is smart enough to automatically adjust its Max Height setting. But outside of the zone, or even when bumping up against the outer boundary of the zone, the Max Height setting remains at whatever the user has configured it to.

Reading this thread I am curious as to why the Mavic 3 will, if outside a height restriction zone and in RTH, drop its height automatically when it reaches the zone and continue its RTH with no stick input from the pilot but the Mini 3 Pro does not.

Well, that's cool! Evidently the Mavic 3 is smart enough to realize that it can automatically descend to safely pass underneath the Altitude Zone.

Maybe the Mavic 3 is better programmed to distinguish between other types of GEO zones which simply stop it at the boundary versus an Altitude Zone where it can safely pass underneath. It reads the correct height restriction, and [unlike the Mini 3 Pro] it can automatically change its Max Height setting even if it has not yet actually passed into or under the defined Geo Zone.

Then this line in the Mavic 3 user manual makes more sense. "If the max altitude is set below the current altitude..." How can the current altitude ever be greater than the set max altitude?

It would make more sense if it said, "If the max altitude is changed to below the current altitude...", because that's apparently what the Mavic 3 will automatically do when encountering an Altitude Zone during RTH. Here's what it says in the Mavic 3 user manual:

[...] the Mavic 3 will [...] drop its height automatically when it reaches the zone and continue its RTH with no stick input from the pilot but the Mini 3 Pro does not. I will give this a try like I did with my Mavic 3 and post back.

You have a Mini 3 Pro to try this with? Looking forward to hearing the results.

 

[Yorkshire_Pud]

the Max Height setting remains at whatever the user has configured it to.

outside the zone the drone's ceiling is still 65m, the reduced ceiling only comes into play inside or below the zone. There has to be a demarkation point somewhere and hitting the border is outside it.......... or that's my reasoning, which is why I like the behaviour of Suren's Mavic 3. It acts like gudes for boats around bridge pillars.

 

[Suren]

This is interesting.

Both his RTH height and Max Height were configured to 65m. But his takeoff point on the beach was covered by the 60m Altitude Zone, and column-EC of the log shows the drone's max height was automatically reduced to 60m to avoid ever hitting that GEO ceiling.

But, as we've since figured out, when the Mini 3 Pro emerged out from under that Altitude Zone, beyond the edge of the defined zone, the max height setting automatically reverted to the originally configured 65m. When the low-battery RTH kicked in, the drone climbed to its configured 65m RTH height and then flew toward Home before bumping into the outer edge of that Altitude Zone. Because it was now higher than the allowed 60m Altitude Zone limit, that GEO zone stopped the drone at its boundary.

The Mini 3 Pro evidently isn't smart enough to automatically descend to safely return underneath the Altitude Zone. Why is that? Anywhere within or underneath the defined Geo zone, it is smart enough to automatically adjust its Max Height setting. But outside of the zone, or even when bumping up against the outer boundary of the zone, the Max Height setting remains at whatever the user has configured it to.


Well, that's cool! Evidently the Mavic 3 is smart enough to realize that it can automatically descend to safely pass underneath the Altitude Zone.

Maybe the Mavic 3 is better programmed to distinguish between other types of GEO zones which simply stop it at the boundary versus an Altitude Zone where it can safely pass underneath. It reads the correct height restriction, and [unlike the Mini 3 Pro] it can automatically change its Max Height setting even if it has not yet actually passed into or under the defined Geo Zone.

Then this line in the Mavic 3 user manual makes more sense. "If the max altitude is set below the current altitude..." How can the current altitude ever be greater than the set max altitude?

It would make more sense if it said, "If the max altitude is changed to below the current altitude...", because that's apparently what the Mavic 3 will automatically do when encountering an Altitude Zone during RTH. Here's what it says in the Mavic 3 user manual:

View attachment 158895



You have a Mini 3 Pro to try this with? Looking forward to hearing the results.

Yes I do have the Mini 3 Pro as well, was too windy for the Mini so just tried the Mavic

 

[Droning on and on...]

Strangely so do mine.

I mean that, for an automated descent whilst moving horizontally it descended quite steeply.
It loses around 40ft of height in around 61 horizontal ft and around 8 seconds, that's a descent slope of around 33°, isnt it?
Personally I think that's quite steep.
The automated power saving descent slope of the Air 2s is 14°.

Okay. No criticism meant.

Just puzzled that you thought that was remarkable in some way.

My dog can jump vertically and get his snout up to around 7ft (Labrador). It's an intrinsic capability. So, when he jumps straight up of his own volition to snap at something blowing by, it doesn't strike me as anything notable. Just sayin'.

It's utterly irrelevant, though, as there's nothing wrong with you thinking that descent is cool. Just didn't get why.