I'm seeing a lot of talk, a lot of it technical, about toilet bowl effect and what causes it. If it happens, what steps need to be taken to re-gain control of the quad?
TBE-what to do if it happens?
- Thread starter Golfnut
- Start date
GlenT
Well-Known Member
TBE is typically a result of a declination error with the GPS receiver, amongst others. With larger multirotors you need to align the GPS puck according to your declination (or longitudinal position on the planet) Also the measurements entered into the flight controller as to where exactly the IMU is on the craft need to be perfect. On the Mavic (I am yet to receive mine) I suspect it is more to do with compass and IMU calibration, as they are the only real calibrations I can think of that may have an effect on positioning and the crafts ability to "know" where it is supposed to be. I know that if my GPS puck (Wookong M flight control on a 810mm hexa) is not aligned perfectly according to my declination or the compass needs calibrated I get a dose of TBE. It is also apparent when you try to fly in a straight path. The craft will drift off to one side slightly as it travels.
TBE is just a bad compass calibration.
Put this into consideration. At lower altitudes, magnetic influence is strongest (more and closer to objects) and at higher it is lower (less and further from objects).
If you calibrate near metal structures, the mavic will create a bad compromised north. As you get higher and further away, the mavic will now start seeing the true north. This confusion creates this arc. If you notice, the arc is smaller at ground levels and gets bigger when you get higher. When the AC gets too much conflicts with gps data, it will switch to atti to prevent the flyaway.
Put this into consideration. At lower altitudes, magnetic influence is strongest (more and closer to objects) and at higher it is lower (less and further from objects).
If you calibrate near metal structures, the mavic will create a bad compromised north. As you get higher and further away, the mavic will now start seeing the true north. This confusion creates this arc. If you notice, the arc is smaller at ground levels and gets bigger when you get higher. When the AC gets too much conflicts with gps data, it will switch to atti to prevent the flyaway.
GerdS
Well-Known Member
I would suggest that every new Mavic owner should calibrate the compass before the first flight. The GO app only checks for sensor range errors and maybe anormalies between both compasses, but it is not aware about the fact that our Mavics have been calibrated latest at China and are now thousands of miles away at locations with very differing magnetic properties.
So to be on the safe side, calibrate your compass first!
And as long as the Atti mode is not available for us, I would not try to use RTH in case of a TBE. Either try flying manually back or to be absolutely on the safe side, just fly until there is the first location where it is safe to land and land there.
So to be on the safe side, calibrate your compass first!
And as long as the Atti mode is not available for us, I would not try to use RTH in case of a TBE. Either try flying manually back or to be absolutely on the safe side, just fly until there is the first location where it is safe to land and land there.
Glenn Goodlett
Well-Known Member
I use RTH every flight. 90 flights and counting. If your Mavic ever flies without control, either directly or indirectly via automated functions, it has a problem and should be sent back to DJI for repair.
Kilrah
Well-Known Member
The question is what to do as pilot inputs if you're in flight and have TBE, not what to do afterwards.
When you have TBE what you should do is switch to ATTI - but we can't. So there isn't much you can do but try to fight trying to find a control itput that could make it fly a straight line where it will hopefully go out of the problem zone and/or get a reliable course info that hopefully helps it find its bearings again.
Thank you Kilrah for recognizing the real question here. I will leave it to those much smarter than me to figure out why this is happening.
If it goes into TBE while RTH is engaged, do I cancel RTH and try to gain control manually...I think so. If it goes into TBE while not in RTH mode, do I engage RTH and hope it works. In short, do I negate all automated functions and try to gain control manually or engage automated controls and hope the quad fixes itself?
If it goes into TBE while RTH is engaged, do I cancel RTH and try to gain control manually...I think so. If it goes into TBE while not in RTH mode, do I engage RTH and hope it works. In short, do I negate all automated functions and try to gain control manually or engage automated controls and hope the quad fixes itself?
Kilrah
Well-Known Member
If you have a navigation issue you want as little automation as possible, unfortunately on the Mavic it's still quite a lot. Sport mode could help a tad, but even that relies on GPS/compass...
You've had 90 flights with no issues? If so, good to know that not every mavic is affected by this bug. It seems like for some people it 'might' be related to calibration (though it seems silly if that's all it is, because some people have calibrated carefully and still had the problem) - but just to see, can I ask how often you calibrate? I've seen people on the forum who say they didn't even calibrate out of the box and it worked, in fact the instructions don't even say you have to calibrate on first use. So I'm interested to know your take. I think it's odd that DJI says to calibrate if you change positions significantly, yet how is it that you don't necessarily need to calibrate on first use if it's shipped from China?
F6Rider
Well-Known Member
I ALWAYS calibrate the compass for the first flight in a new flying area, but you really need to be careful about where you calibrate, no concrete (rebar) no picnic tables, no beaches, underground pipes or wiring. No watch or keys in pocket, that compass is a sensitive little sucker. All of these can give you a bad calibration, , and thus problems once you clear that area. Some calibrate every time, but to me that is just asking for a bad one. If you get TBE all you can do on the Mavic is try to get it back as soon as you can and land it, some pilots have said that the pause button works to 'freeze' the quad in place letting you get control back, I don't know as I have never had it after 300 flights on my Phantoms, and I just got my Mavic.
joe_gomez
Member
With few exceptions, when I've experienced TBE, it correlated with a GPS warning, and automatic switching to ATTI mode. When it switches to ATTI, the circular flight path stops, and instead, the MP drifts rapidly away from whatever hover position I had chosen. While in ATTI mode, I apply inputs to bring the MP back to where I want it. So, once a TBE is occurring, you should still have adequate control input - it just won't respond with the precision and accuracy that you're expecting.
Further, all the TBEs have been on a horizontal plane. That is, the altitude has not be affected. Thus, if you find yourself circling, increase your altitude immediately if there are objects at your current altitude. Until you break the cycle (or the unit switches into ATTI mode) the circle will continue to get larger, and you will impact objects.
Until the MP jumps from GPS to ATTI mode, it is very difficult to fly a straight line. And every pause you make will restart the circle. It's quite scary if you're not expecting it. The key is to not panic. You haven't lost complete control. It's not flying away from you on its own. While in GPS mode, it's hunting to for the hover spot and will do so as the circle gets increasing larger. Once it switches to ATTI, it will appear to 'take off' on its own as it drifts (possibly rapidly) in whatever direction it was hurled at the end of the GPS cycle. Keep eyes on the bird (or get orientation through the video down link) quickly and provide input to bring her back to you.
The ATTI interval will switch back to GPS once whatever source of error has been overcome. When it does, you'll see the GPS signal return to normal, and any hover attempt will once again be rock solid.
As to the causes, I'm completely convinced those that are regularly experiencing this issue, despite proper compass calibrations, are suffering from a bug/defect that is NOT resolvable through repeated proper calibrations. If you're experiencing frequent TBEs, contact DJI support.
Further, all the TBEs have been on a horizontal plane. That is, the altitude has not be affected. Thus, if you find yourself circling, increase your altitude immediately if there are objects at your current altitude. Until you break the cycle (or the unit switches into ATTI mode) the circle will continue to get larger, and you will impact objects.
Until the MP jumps from GPS to ATTI mode, it is very difficult to fly a straight line. And every pause you make will restart the circle. It's quite scary if you're not expecting it. The key is to not panic. You haven't lost complete control. It's not flying away from you on its own. While in GPS mode, it's hunting to for the hover spot and will do so as the circle gets increasing larger. Once it switches to ATTI, it will appear to 'take off' on its own as it drifts (possibly rapidly) in whatever direction it was hurled at the end of the GPS cycle. Keep eyes on the bird (or get orientation through the video down link) quickly and provide input to bring her back to you.
The ATTI interval will switch back to GPS once whatever source of error has been overcome. When it does, you'll see the GPS signal return to normal, and any hover attempt will once again be rock solid.
As to the causes, I'm completely convinced those that are regularly experiencing this issue, despite proper compass calibrations, are suffering from a bug/defect that is NOT resolvable through repeated proper calibrations. If you're experiencing frequent TBEs, contact DJI support.
Today My Mavic took off in GPS mode with 18 satellites the same spot that i always fly in and i was up about 30 feet and it switched to "vision"and then ATTI and the Mavic drifted and started circle. I felt a panic coming on i gained control and landed. i still saw 18 satellites but is was in a red color.
I restarted everything and then i had a perfect flight.
I called DJI and they said some interference could be the issue .
my concern is what if this happens when i am a mile out can i still take control ? And i was also under the impression with the new updates that if the GPS signal is lost the Mavic will RTH on its own in ATTI mode ?
Also what is the "Vision in yellow" in replace of GPS on the top at times ?
Thank you
Are you on the latest firmware? What you've described is what happens when the flight controller gets bad data from one of the compasses. When it sees a discrepancy between the compass and the GPS data, it would begin to disregard the GPS data (and indicate poor GPS signal), switch to ATTI mode, and begin to drift.
In my case, during the time the GPS and compass didn't agree, but before the mode switched to ATTI, I'd get the increasing spiral flight pattern. Once it switched to ATTI, it would shoot off in whatever direction it was in on the circular pattern - like a kid coming off a spinning marry-go-round. At no point did I lose control, but without the self-stabilizing/hovering, it gives the feel of loss of control.
I would recommend you download the DAT file from your MP as soon as possible (they eventually get overwritten by successive flights) and get it to @BudWalker.
I suppose there may other issues that can cause your symptoms, but everything you spelled out looks exactly what I (and others) have experienced - and what resulted in a firmware upgrade to counteract the interference the MP sees on the rear compass when RPMs are high on the motors.
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From your description your incident could be similar to the gpsHealth incidents that others have experienced. If you can retrieve the .DAT file we could take a closer look. To see how to do that go here. It'll be large so you'll have to Dropbox it and provide the link.
its 1.5 gigs i will upload to dropbox its the first flight with todays date and you can see the other flights after the restart where flawless. should i share the flight logs in drop box here ?
and I thank you both for your help
Jimmy
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Dropbox - DJI_ASSISTANT_EXPORT_FILE_2016-12-20_19-27-25.DAT
Its the first short flight of today. After that the flights were perfect and the footage i got today was excellent. p
thank you again for looking at the files
Also i have a Mac is there a easy way i can view the logs ? I might have no idea what I am looking at but. LOL
Jimmy
I looked at the first flight. The cause of the incident was a drop in gpsHealth which is not the same as numSats. GpsHealth has a range from 0 (worst) to 5 (best) and is a measure of both vertical and horizontal dilution of precision. With the P3 if gpsHealth drops below 4 the P3 will switch to ATTI mode because the GPS is unreliable.
In this flight the gpsHealth dropped abruptly from 5 to 1 which caused a brief switch to ATTI.
The was another flight about 3 weeks ago where the same abrupt drop in gpsHealth occurred. Spooky Action at a Distance I've not seen anything like this in the over 100 P3 flights I've looked at. With the P3 a drop in gpsHealth was gradual and always associated with a reduction in the numSats. IMHO these two Mavic incidents.are caused either by hardware or firmware.
@jamgabbi you mentioned that you thought the response to lost GPS would be an RTH under ATTI. I hope not. With the P3 a switch to ATTI would cause the P3 to hover, or at least drift away with the wind. I.e., it wouldn't try to RTH. Several fly-aways were caused by RTH being initiated while in ATTI mode. I would think the Mavic would do the same and not try and navigate while in ATTI mode. But, I did see a flight recently where it appears to have done exactly that that. Mavic First Flight Uncontrolled - Magnetic Interference
@jamgabbi you also mentioned having a Mac and wanting to view the logs. DatCon will run under MacOS with a little help. See the release notes. That will produce a .csv that can be plotted using Excel. The next release of CsvView (used to produce the plot above) will also be runnable under MacOS.
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