What causes ATTI mode?

[OOO]

It's not just the drift that catches people out - it's that unlike in GPS mode, when you center the sticks, it just coasts rather than stopping. You have to apply reverse stick to stop it.

Very true! I often fly in ATTI mode and have to apply reverse stick to keep the drone stable. No problem when I fly fast, but whenever I go slow it is almost impossible to keep it stable without applying reverse stick!

 

[solentlife]

No. The aircraft does no active positioning in ATTI, and thus cannot navigate to a location.

Not strictly true actually.

P-ATTI - where the AC drops into ATTI mode due to loss of GPS / positional hovering data - then RTH is basically unworkable due to no GPS data to ascertain direction / distance to RTH.

A-mode (ATTI mode selected by pilot) can still use limited GPS data to RTH ...

Page 11 manual.

Nigel

 

[sar104]

Not strictly true actually.

P-ATTI - where the AC drops into ATTI mode due to loss of GPS / positional hovering data - then RTH is basically unworkable due to no GPS data to ascertain direction / distance to RTH.

A-mode (ATTI mode selected by pilot) can still use limited GPS data to RTH ...

Page 11 manual.

Nigel

Good distinction - if the pilot switches to ATTI mode and then the aircraft loses connection it will return to GPS mode and go home. But if the switch to ATTI mode was made by the FC due to loss of GPS or compass errors then it is unable to navigate.

 

[Andy9]

Did you try this personally? If it is true the explanation might be: manually switch ATTI means that the AC has GPS but ignores it, while in the other case it loses GPS so can't be restored.
Logical explanation but don't know if it's true.

 

[sar104]

Did you try this personally? If it is true the explanation might be: manually switch ATTI means that the AC has GPS but ignores it, while in the other case it loses GPS so can't be restored.
Logical explanation but don't know if it's true.

Almost correct. Obviously if it loses GPS lock then it has no GPS to navigate with. However, the most common cause of the FC switching to ATTI is a compass error that it cannot resolve. In that case it generally has perfectly good GPS data and knows exactly where it is, but does not know which direction it is facing, and so does not know how to move in order to hold or change location.

 

[Erised]

Yes if you switch to atti the AC will not use GPS for positioning but will use it to RTH (I tried this)
If the AC switches to atti because of GPS loss the craft does not know where it is and RTH is a no go, you have to fly the AC home.

 

[Erised]

When you switch to atti the craft doe's not ignore GPS it only doe's not use it for position. It will still place your craft on the map and be able to RTH.

 

[kevinp3s]

So if in P-Atti mode and it loses 5.8ghz signal.....what happens..??

 

[sar104]

So if in P-Atti mode and it loses 5.8ghz signal.....what happens..??

It switches back to P-GPS and returns home, if that is the RTH setting.

 

[Meta4]

So if in P-Atti mode and it loses 5.8ghz signal.....what happens..??

If you lose signal, the aircraft will do whatever it is programmed to do on loss of signal.
The default setting is RTH but there are other options (land and hover).

 

[Andy9]

And another option - AC switches to the other signal frequency and maybe regain connection. Depends on what your pre sets are.

 

[Gtarman52]

ATTI mode kicks in when I first turn on my quad until it finds enough sats, then it goes to gps mode. I don't know if thats normal or not.

 

[sar104]

ATTI mode kicks in when I first turn on my quad until it finds enough sats, then it goes to gps mode. I don't know if thats normal or not.

That's completely normal. It can't use GPS mode until it has a satisfactory GPS lock.

 

[Meta4]

ATTI mode kicks in when I first turn on my quad until it finds enough sats, then it goes to gps mode. I don't know if thats normal or not.

Atti mode isn't just something you can switch to.
Atti mode is what you have when the Phantom has no GPS data whether that's because you flicked a switch or because your Phantom hasn't been able to detect enough GPS satellites.

 

[sar104]

Atti mode isn't just something you can switch to.
Atti mode is what you have when the Phantom has no GPS data whether that's because you flicked a switch or because your Phantom hasn't been able to detect enough GPS satellites.

Actually it's rather more complicated than that. Disregarding the situation where the pilot manually switches to ATTI, the most common cause of the FC switching is nothing to do with a lack of GPS position data - it's caused by a disagreement between the yaw computed from the rate gyros and the yaw indicated by the compass. If that cannot be resolved then the FC assumes that it cannot trust its yaw (heading) and therefore cannot navigate or hold position.

That said, a lack of GPS data, such as indoors or in locations with very poor sky view, will also trigger ATTI mode - it's just less common.

 

[solentlife]

When you switch to atti the craft doe's not ignore GPS it only doe's not use it for position. It will still place your craft on the map and be able to RTH.

Exactly ....

Nigel

 

[Shakiercheese]

Maybe this is a good indication that some need to learn more about flying in atti mode just for this reason. Imo I would practice flying in atti mode to understand what the bird does and how it reacts to input. It could save a lot of money in the long run. Some of us just cant crash one and go out and buy another on the fly.