In the manual it says to always turn the Controller on before the Mavic. However, to download data from the SD card, the Mavic has to be connected to a computer and turned on.
Is it OK to only turn the Mavic on when downloading from the SD card or does the Controller also have to be turned on as well.

I wouldn't bother, if it's handy you could turn controller on without app.
I find it too slow and you also need remove gimbal clamp - much better to pop the card out and use a card reader.

For ultimate 'safety' with phantoms you were supposed to never turn it n when doing anything like this unles props were off.
It was assumed there's a slight risk it might suddenly decide to RTH - to last loction outdoors if controller is not connected.
Seems unlikley but still better to pop the card out and leave it tuned off anyway.
Sitting on a dek getting hot can't be a good thing even if fan is o.

It doesn't matter, you can only turn on the Mavic. It's better to uninstall the propellers when you connect the Mavic to computer.

DJI Mindy Posted at 2016-12-19 13:56
It doesn't matter, you can only turn on the Mavic. It's better to uninstall the propellers when you connect the Mavic to computer.

OK so it sounds like it may be safer to just remove the SD card but I thought I saw somewhere that the flight logs are stored in the Mavic, not on the SD card. If that is the case then I would need to connect the Mavic to the computer to see the flight logs. Is this correct?

Jenee 2 Posted at 2016-12-19 14:00
OK so it sounds like it may be safer to just remove the SD card but I thought I saw somewhere that the flight logs are stored in the Mavic, not on the SD card. If that is the case then I would need to connect the Mavic to the computer to see the flight logs. Is this correct?

The flight data are stored in the Mavic.
You need to connect the Mavic to DJI Assistant.