Mavic Air fly-away with no luck to find it. SOLVED

[RobH2]

@Jameslavis
Thanks for your post too. It makes me feel better to know that I can be pretty confident that if my aircraft is reporting the correct orientation preflight that I can assume I won't have a fly away unless I have actual equipment failure. That's the one thing we can never control. If a component dies we'll all suffer a crash, loss or mishap.

 

[alexbutenkofi]

@Jameslavis
Thanks for your post too. It makes me feel better to know that I can be pretty confident that if my aircraft is reporting the correct orientation preflight that I can assume I won't have a fly away unless I have actual equipment failure. That's the one thing we can never control. If a component dies we'll all suffer a crash, loss or mishap.

Good point. I have learned my lesson.

 

[Tinmania]

Regardless of what happened the aircraft should have responded to the pause command. Is the pause shown in the log?

There was nothing to pause. Pausing stops automated flight, such as RTH and intelligent flight mode. But even if RTH was triggered pausing does not stop position hold, and hovering in place is impossible in this situation. While hovering it is still making corrections to counteract drift. In this incident's case it had no ability to hold position without snowballing small incorrect corrections into major AC movement.

What could save an AC in this type of situation is switching to ATTI mode (no position hold). The issue as I see it is that the FC is not switching to ATTI, at least not in time to prevent an incident like this. Presumably if GPS health is good it could be used to let the FC know, "Hey, we are nowhere near where we should be, your corrections are making things much worse, so engage ATTI, pronto!"

On another note, while I absolutely think we should all check that heading is correct before take-off, I don't think the lack of doing so, when it is not something DJI tells us to do, is really pilot error. By that I mean you have Go4 telling you "Ready to Go!" Then the FC fails to realize it's moving the AC far from where, barring an F5 tornado, it should be when it should stop and switch to ATTI. Yet it doesn't. This is exacerbated by no means to (officially) manually switch to ATTI.



Mike

 

[InvisibleName]

While I absolutely think we should all check that heading is correct before take-off, I don't think the lack of doing so, when it is not something DJI tells us to do, is really pilot error. By that I mean you have Go4 telling you "Ready to Go!" Then the FC fails to realize it's moving the AC far from where, barring an F5 tornado, it should be when it should stop and switch to ATTI. Yet it doesn't. This is exacerbated by no means to (officially) manually switch to ATTI.

Mike

So, you buy a new car and drive straight out of a road junction without looking left or right, because the car manufacturer didn't tell you to do so??? Come on, flying a drone is done with the full understanding that you alone are responsible for its safe operation, hence you are responsible for any pre-flight checks that will improve the likelihood of a safe & successful flight.

 

[Tinmania]

So, you buy a new car and drive straight out of a road junction without looking left or right, because the car manufacturer didn't tell you to do so??? Come on, flying a drone is done with the full understanding that you alone are responsible for its safe operation, hence you are responsible for any pre-flight checks that will improve the likelihood of a safe & successful flight.

Good lord, you have confirmed why internet car analogies always suck.



Mike

 

[InvisibleName]

Good lord, you have confirmed why internet car analogies always suck.



Mike

Ok, so putting aside maybe a poor analogy, you have to acknowledge that, just because DJI don’t specifically say do this check, you really should do it!

 

[Tinmania]

Ok, so putting aside maybe a poor analogy, you have to acknowledge that, just because DJI don’t specifically say do this check, you really should do it!

No, by all means lets stick with a car analogy, since you wanted to go down that road (no pun). This is more like buying a car that requires you to verify via its nav screen, that it is actually facing the way it shows it does on its map before driving off. If you fail to do so, have fun smashing into the car behind you when putting it into drive is actually reverse. Oh, and they never mentioned about this fun little, "gotcha!"



Mike

 

[sar104]

There was nothing to pause. Pausing stops automated flight, such as RTH and intelligent flight mode. But even if RTH was triggered pausing does not stop position hold, and hovering in place is impossible in this situation. While hovering it is still making corrections to counteract drift. In this incident's case it had no ability to hold position without snowballing small incorrect corrections into major AC movement.

What could save an AC in this type of situation is switching to ATTI mode (no position hold). The issue as I see it is that the FC is not switching to ATTI, at least not in time to prevent an incident like this. Presumably if GPS health is good it could be used to let the FC know, "Hey, we are nowhere near where we should be, your corrections are making things much worse, so engage ATTI, pronto!"

On another note, while I absolutely think we should all check that heading is correct before take-off, I don't think the lack of doing so, when it is not something DJI tells us to do, is really pilot error. By that I mean you have Go4 telling you "Ready to Go!" Then the FC fails to realize it's moving the AC far from where, barring an F5 tornado, it should be when it should stop and switch to ATTI. Yet it doesn't. This is exacerbated by no means to (officially) manually switch to ATTI.



Mike

ATTI is exactly the solution as you point out. But note that GPS health is not the accuracy of the GPS fix - it's a measure of the correlation between the various inputs to the IMU fusion scheme, and so the FC should switch to ATTI when it goes below 4. The Phantom range seems to do that just fine, but the more recent software on the Mavics appears to delay the switch to ATTI mode - i.e. the FC tries harder to reconcile the discrepancies. Personally I think it's a poor strategy.

 

[Tinmania]

ATTI is exactly the solution as you point out. But note that GPS health is not the accuracy of the GPS fix - it's a measure of the correlation between the various inputs to the IMU fusion scheme, and so the FC should switch to ATTI when it goes below 4. The Phantom range seems to do that just fine, but the more recent software on the Mavics appears to delay the switch to ATTI mode - i.e. the FC tries harder to reconcile the discrepancies. Personally I think it's a poor strategy.

I agree, especially without the option to manually switch to ATTI, at least not officially.



Mike

 

[InvisibleName]

No, by all means lets stick with a car analogy, since you wanted to go down that road (no pun). This is more like buying a car that requires you to verify via its nav screen, that it is actually facing the way it shows it does on its map before driving off. If you fail to do so, have fun smashing into the car behind you when putting it into drive is actually reverse. Oh, and they never mentioned about this fun little, "gotcha!"

Mike

But the point is that the compass indicator is telling you there is a problem, but you’re suggesting that, because DJI don’t specifically tell you to check it, you can ignore it?

 

[Tinmania]

But the point is that the compass indicator is telling you there is a problem, but you’re suggesting that, because DJI don’t specifically tell you to check it, you can ignore it?

It is not "telling you" anything other than, "Ready to Go!" (in green!). Nowhere does DJI "tell" you to use your trusty Boy Scout compass before taking off to verify its "Ready to Go!" announcement.



Mike

 

[InvisibleName]

It is not "telling you" anything other than, "Ready to Go!" (in green!). Nowhere does DJI "tell" you to use your trusty Boy Scout compass before taking off to verify its "Ready to Go!" announcement.



Mike

I’m referring to the Compass display in the bottom left of the DJI Go app. Are you unaware of this?

 

[Tinmania]

I’m referring to the Compass display in the bottom left of the DJI Go app. Are you unaware of this?

Yea, never knew it existed. Thanks for pointing it out.

 

[BudWalker]

ATTI is exactly the solution as you point out. But note that GPS health is not the accuracy of the GPS fix - it's a measure of the correlation between the various inputs to the IMU fusion scheme, and so the FC should switch to ATTI when it goes below 4. The Phantom range seems to do that just fine, but the more recent software on the Mavics appears to delay the switch to ATTI mode - i.e. the FC tries harder to reconcile the discrepancies. Personally I think it's a poor strategy.

It seems that the more recent P3 firmwares have also adopted this strategy of trying to reconcile a Yaw/magYaw discrepancy and delaying the switch to ATTI. This happened to my flying buddy (who is a good source of incidents ) At launch there was 30° Yaw/magYaw discrepancy. It wan't until 30 secs that it decided that was a YAW_ERROR_LARGE and then fixed that Yaw/magYaw discrepancy by rotating the P3P. It never switched to ATTI.

 

[InvisibleName]

Yea, never knew it existed. Thanks for pointing it out.

So, ignoring the sarcasm, why do you refer to a “ Boy Scout compass”?

 

[sar104]

I’m referring to the Compass display in the bottom left of the DJI Go app. Are you unaware of this?

I think the issue is that although the orientation display is there and, if compared to actual heading (assuming that the pilot knows the actual heading), will indicate if there is a problem, it's clearly not an intuitive check for most people to make. The multiple discussions on these forums attest to that.

If the instruction manuals mentioned it as an important pre-flight check then perhaps more people (at least the minority who appear to read documentation) would be aware of it.

 

[BudWalker]

It's really unfortunate that doing the Yaw check before launch isn't mentioned in any DJI documentation. It's been mentioned in these forums and the DJI forum several times so, hopefully, most pilots are aware of this check.

I’m referring to the Compass display in the bottom left of the DJI Go app. Are you unaware of this?

I think the one you want to look at is the red triangle heading indicator on the map display.

 

[sar104]

It seems that the more recent P3 firmwares have also adopted this strategy of trying to reconcile a Yaw/magYaw discrepancy and delaying the switch to ATTI. This happened to my flying buddy (who is a good source of incidents ) At launch there was 30° Yaw/magYaw discrepancy. It wan't until 30 secs that it decided that was a YAW_ERROR_LARGE and then fixed that Yaw/magYaw discrepancy by rotating the P3P. It never switched to ATTI.
View attachment 39012

I guess it's not surprising that they would do this across the range. At least with the P3 there is always the option to switch to ATTI.

 

[InvisibleName]

I think the issue is that although the orientation display is there and, if compared to actual heading (assuming that the pilot knows the actual heading), will indicate if there is a problem, it's clearly not an intuitive check for most people to make. The multiple discussions on these forums attest to that.

If the instruction manuals mentioned it as an important pre-flight check then perhaps more people (at least the minority who appear to read documentation) would be aware of it.

Put this way, I agree that it would be a good idea for it to be documented (although, based on a lot of questions on here, I’m not sure how many would read it!).

Doesn’t get away from the point I was making that the indicator is right there in front of the pilot, choose to ignore it at their peril!

 

[sar104]

Put this way, I agree that it would be a good idea for it to be documented (although, based on a lot of questions on here, I’m not sure how many would read it!).

Doesn’t get away from the point I was making that the indicator is right there in front of the pilot, choose to ignore it at their peril!

I agree - once it's pointed out. But, prior to that, most pilots don't seem to be aware at all of its significance so it's harsh to criticize them for not paying much attention to it.