Atti Mode

[papopagan]

Why or When the Mavic switch to Atti Mode?

If i want to fly indoors how will the craft do it?

 

[Gray_seagull]

As far as I know there is no manual switching to atti mode
It’ll switch to atti mode if you lose gps signal

 

[papopagan]

As far as I know there is no manual switching to atti mode
It’ll switch to atti mode if you lose gps signal[/

Why would I lose GPS signal? Have many of these cases been given?

In which GPS potential should be normal and which should not fly to avoid the atti mode in a fairly distanced flight???

 

[MavicCF]

Why or When the Mavic switch to Atti Mode?

If i want to fly indoors how will the craft do it?

If I remember correctly the Mavic can also go into ATTI if the IMU decides that what it is calculating disagrees with what the GPS is saying, in this case, it disregards the GPS and goes into ATTI even if it has plenty of satellites available.

 

[sar104]

If I remember correctly the Mavic can also go into ATTI if the IMU decides that what it is calculating disagrees with what the GPS is saying, in this case, it disregards the GPS and goes into ATTI even if it has plenty of satellites available.

The most common cause is actually a disagreement between the compass and the IMU rate gyros. GPS is often not involved at all, and the problem is not that it doesn't have good GPS positional information, it's that it doesn't know which way it is facing. Without a reliable heading (yaw) value it cannot navigate and stops trying to hold position.

 

[MavicCF]

The most common cause is actually a disagreement between the compass and the IMU rate gyros. GPS is often not involved at all, and the problem is not that it doesn't have good GPS positional information, it's that it doesn't know which way it is facing. Without a reliable heading (yaw) value it cannot navigate and stops trying to hold position.

I thought the compass was involved somehow! So it's disagreement between the compass and the IMU gyros, not the IMU and GPS data. That makes sense, thanks for clearing it up for me.

 

[sar104]

I thought the compass was involved somehow! So it's disagreement between the compass and the IMU gyros, not the IMU and GPS data. That makes sense, thanks for clearing it up for me.

In theory I would expect that if the velocity and position estimated from the IMU accelerometers significantly disagreed with the GPS velocity and position data then a similar situation might arise, triggering ATTI mode for that reason. I've never seen it happen though - it's been a yaw error in every case that I've examined.

 

[Rocket Man]

I thought the compass was involved somehow! So it's disagreement between the compass and the IMU gyros, not the IMU and GPS data. That makes sense, thanks for clearing it up for me.

So for "Best Practices", and to minimize ATTI related issues, it would be beneficial to calibrate the IMU / compass prior to flight operations?? Any special operational settings that will minimize ATTI related issues, since it appears, once the bird goes into ATTI Mode, it will either hover / or return to home, depending on what settings have been put in place, until the compass and or IMU sort out their differences.

 

[sar104]

So for "Best Practices", and to minimize ATTI related issues, it would be beneficial to calibrate the IMU / compass prior to flight operations?? Any special operational settings that will minimize ATTI related issues, since it appears, once the bird goes into ATTI Mode, it will either hover / or return to home, depending on what settings have been put in place, until the compass and or IMU sort out their differences.

Not really - those problems are only very rarely related to calibration. It's almost always magnetic interference at the takeoff location, and calibrating is not going to help with that at all.

 

[53-63-6f-74-74]

So for "Best Practices", and to minimize ATTI related issues, it would be beneficial to calibrate the IMU / compass prior to flight operations?? Any special operational settings that will minimize ATTI related issues, since it appears, once the bird goes into ATTI Mode, it will either hover / or return to home, depending on what settings have been put in place, until the compass and or IMU sort out their differences.

No, when GPS is lost (atti mode activates) you will NOT get a stable hover OR a return to home. You will keep altitude, however. The aircraft will blow away with the wind until it's gone, unless you take control of it.

 

[Rocket Man]

Not really - those problems are only very rarely related to calibration. It's almost always magnetic interference at the takeoff location, and calibrating is not going to help with that at all.

With the most common cause being a disagreement between the compass and the IMU rate gyros, I'm thinking calibration verification might be a good item to put on the pre-flight checklist.

 

[Rocket Man]

No, when GPS is lost (atti mode activates) you will NOT get a stable hover OR a return to home. You will keep altitude, however. The aircraft will blow away with the wind until it's gone, unless you take control of it.

In an ATTI mode activation situation, what control options will the aircraft respond to?

 

[sar104]

With the most common cause being a disagreement between the compass and the IMU rate gyros, I'm thinking calibration verification might be a good item to put on the pre-flight checklist.

OK - but why? The disagreement almost never has anything to do with either being out of calibration?

 

[Rocket Man]

OK - but why? The disagreement almost never has anything to do with either being out of calibration?

Rather be safe, than sorry. Better to rule out all possibilities by performing a re-calibration.

 

[sar104]

Rather be safe, than sorry. Better to rule out all possibilities by performing a re-calibration.

That's complete overkill in my opinion.

 

[Rocket Man]

That's complete overkill in my opinion.

Yea, I thought that might be your consensus. Though there are numerous horror stories in the forum where pilots had wished they'd performed a calibration prior to flying, as it might have prevented an compass and or IMU discrepancy. While I understand both the pros and cons associated with performing a calibration every time you launch the bird, I'd advocate a performing a calibration if when at boot up you receive an compass error, or are just launching from a new site that hasn't been flown in. Safety first, as Magnetic interference near the takeoff point or un-calibrated compasses are the usual suspects.

 

[sar104]

Yea, I thought that might be your consensus. Though there are numerous horror stories in the forum where pilots had wished they'd performed a calibration prior to flying, as it might have prevented an compass and or IMU discrepancy. While I understand both the pros and cons associated with performing a calibration every time you launch the bird, I'd advocate a performing a calibration if when at boot up you receive an compass error, or are just launching from a new site that hasn't been flown in. Safety first, as Magnetic interference near the takeoff point or un-calibrated compasses are the usual suspects.

I've seen similar comments, but they almost always arise from a misunderstanding of the event in question. Can you point to even a single example where a lack of calibration of either the compass or IMU caused a disagreement between them?

 

[Rocket Man]

I've seen similar comments, but they almost always arise from a misunderstanding of the event in question. Can you point to even a single example where a lack of calibration of either the compass or IMU caused a disagreement between them?

While there are pros and cons to performing an IMU/Compass calibration prior to flying, Mavic Pro pilots who experience flight periods where their aircraft switches to ATTI Mode, resulting in a near crash or fatal crash, have advocated performing a IMU/Compass calibration prior to flight as a means to rule out IMU/Compass related issues:

Costa Rica Guy Dec 18, 2017
Atti/ GPS switches

Mar 20 2018 – Mar 21, 2018
I had my first atti mode experience!!

Atti mode

Compass error almost every flight - ATTI mode usually for 10-120 sec, then OK

https://mavicpilots.com/threads/errors-compass-gps-imu.38346/https://mavicpilots.com/threads/yaw-

Yaw errors and Compass Error = ATTI mode but why? log file include

Mavic suddenly switched to ATTI mode mid flight

Mavic switched to ATTI mode and almost crashed

 

[sar104]

While there are pros and cons to performing an IMU/Compass calibration prior to flying, Mavic Pro pilots who experience flight periods where their aircraft switches to ATTI Mode, resulting in a near crash or fatal crash, have advocated performing a IMU/Compass calibration prior to flight as a means to rule out IMU/Compass related issues:

Costa Rica Guy Dec 18, 2017
Atti/ GPS switches

Mar 20 2018 – Mar 21, 2018
I had my first atti mode experience!!

Atti mode

Compass error almost every flight - ATTI mode usually for 10-120 sec, then OK

https://mavicpilots.com/threads/errors-compass-gps-imu.38346/https://mavicpilots.com/threads/yaw-

Yaw errors and Compass Error = ATTI mode but why? log file include

Mavic suddenly switched to ATTI mode mid flight

Mavic switched to ATTI mode and almost crashed

Right, but of those seven examples, only one (Mavic suddenly switched to ATTI mode mid flight) was indicative of a calibration problem, and it's one of only two that I have ever seen reported. And I have analyzed many tens of such events. As I said before, ATTI mode events are almost never due to calibration issues. So if you want to calibrate every flight that's fine, but I am going to continue to point out that the data do not support the need for that.

 

[Mossiback]

Go 4 will alert you if you need re-calibration. If you do it when it is not needed you risk replacing a good calibration with an untried one. I have not calibrated my MP going on two years now without problems (I do check Go 4 before flying for any notices).