A Couple Questions

[LSDMT]

so I was out flying circuits (circles, ovals, figure 8s, primarily in P mode) to drain my batteries as part of my charge and discharge cycle and had a few goofy things happen:

• towards the end of a couple flights, the IMU Altitude started gradually going into negative numbers. i believe the largest was -7.2 feet. that seems like it could cause an issue eventually. is it just that flying fairly fast and banking a bunch confused the IMU and it eventually lost track of it’s proper altitude? is it something i should worry about?

• also got an error message a few times stating ‘Compass Redundancy Switch’. looking at my logs - i was green across the board on minor signal errors, 15-16 sats, nothing out of the ordinary:

 

[Deleted member 62848]

so I was out flying circuits (circles, ovals, figure 8s, primarily in P mode) to drain my batteries as part of my charge and discharge cycle and had a few goofy things happen:

• towards the end of a couple flights, the IMU Altitude started gradually going into negative numbers. i believe the largest was -7.2 feet. that seems like it could cause an issue eventually. is it just that flying fairly fast and banking a bunch confused the IMU and it eventually lost track of it’s proper altitude? is it something i should worry about?

• also got an error message a few times stating ‘Compass Redundancy Switch’. looking at my logs - i was green across the board on minor signal errors, 15-16 sats, nothing out of the ordinary:

Ive had a -7 kph on one of my first flights,while going foward,did the compass and imu and its been ok,thought it was just teething issue with new p4 ,no number troubles for a while now,,as for compass redundancy switch i have never ever heard of in my flying history,,wonder what this is and its purpose

 

[LSDMT]

...anyone?

 

[Meta4]

so I was out flying circuits (circles, ovals, figure 8s, primarily in P mode) to drain my batteries as part of my charge and discharge cycle and had a few goofy things happen:

• towards the end of a couple flights, the IMU Altitude started gradually going into negative numbers. i believe the largest was -7.2 feet. that seems like it could cause an issue eventually. is it just that flying fairly fast and banking a bunch confused the IMU and it eventually lost track of it’s proper altitude? is it something i should worry about?

1. There's no need to do any "charge and discharge cycle"
2. The IMU altiude reading comes from a barometer measuring air pressure.
Flying and turning fast wouldn't have much impact on air pressure.
You would see a negative reading if you are flying lower than the launch point.
If you are flying higher than launch point and seeing negative, it's not uncommon for there to be some altitude drift over time with changes in local air pressure or the Phantom heating up.
If it's more than a few feet, recalibrating the IMU may fix it.

 

[LSDMT]

1. There's no need to do any "charge and discharge cycle"
2. The IMU altiude reading comes from a barometer measuring air pressure.
Flying and turning fast wouldn't have much impact on air pressure.
You would see a negative reading if you are flying lower than the launch point.
If you are flying higher than launch point and seeing negative, it's not uncommon for there to be some altitude drift over time with changes in local air pressure or the Phantom heating up.
If it's more than a few feet, recalibrating the IMU may fix it.

I typically store it for days at a time with my batteries at full charge. I top them off here and there but every once in a while, I will discharge the batteries down to 15% and let them cool completely before recharging them. I guess it’s a practice I got into flying other copters back in the day. my auto–discharge is set to 10 days currently.

it was definitely flying higher than my launch point. I was flying in the late morning when it was cooler but it was starting to heat up outside by the time I was done. maybe that in conjunction with the phantom heating up caused the readings to be off?

I don’t really use RTH much but if I had to – I guess I would be worried that it would think the ground is )in this case) 7 feet higher than it actually is and try to turn itself off. Or would it actually use the sensors on the bottom to determine the ground and ignore the negative IMU Altitude readings?

any idea on the compass redundancy error? I mean – i’m glad it has a redundant compass to fall back on if it’s getting weird readings from the primary compass but – should I be worried about that?

 

[Meta4]

I will discharge the batteries down to 15% and let them cool completely before recharging them.

That's not necessary with the batteries in your Phantom.
They are a lot more sophisticated than the old tech batteries you used in the past.

it was definitely flying higher than my launch point. I was flying in the late morning when it was cooler but it was starting to heat up outside by the time I was done. maybe that in conjunction with the phantom heating up caused the readings to be off?
I don’t really use RTH much but if I had to – I guess I would be worried that it would think the ground is )in this case) 7 feet higher than it actually is and try to turn itself off. Or would it actually use the sensors on the bottom to determine the ground and ignore the negative IMU Altitude readings?

If it's just a few feet that shouldn't mater much.
You always want to leave a good safety margin anyway for RTH height.
Just keep an eye on it and see if it's trivial or significant and recalibrate the IMU if it's a problem.

 

[Dale Perry]

Someone please tell me how I get to the flight log info that tells me what my phantom 4 is doing every second. All I can see is the flight path. Respond to
[email protected]. I will be grateful for this info. I am in Florida USA

 

[iflyp3s]

Hi there. It is indeed rare to see a 'compass redundancy switch' error/warning, but simply means that the drone has decided that the main compass has experienced interference so that it will not be able to produce accurate data for the onboard computer, so it will use a fallback compass in hope of resolving the issue and maintaining normal flight.

I don't think it's much of a problem if it happened once or occurs every now and then, but if it's all the time then you'll need to chase that up with DJI support. I assume it's just something with the environment that is causing it.

Speed and altitude will have nothing to do with it, although the compass is located on the leg of the aircraft, and you may not have realised but might've just struck the leg a tad while flying afar (by the looks of your map) on an object (not enough to break the leg, just having your hand covering it is enough to make it go out of whack momentarily).

If you're ever in flight and any warning of IMU or compass pops up, the reliability of control you'll have over the aircraft is severely reduced. If it's far away, use extreme caution to return it home, prepared for it to make a sudden, unexpected move as the Phantom is clearly confused about its whereabouts. If confident, use ATTI mode (it should do this automatically) to bring it home so the confused data doesn't take matters into its own hands. If it persists, again call DJI support.

Sorry to hear about this problem, but good luck for your future flights. [emoji3]

 

[LSDMT]

Hi there. It is indeed rare to see a 'compass redundancy switch' error/warning, but simply means that the drone has decided that the main compass has experienced interference so that it will not be able to produce accurate data for the onboard computer, so it will use a fallback compass in hope of resolving the issue and maintaining normal flight.

I don't think it's much of a problem if it happened once or occurs every now and then, but if it's all the time then you'll need to chase that up with DJI support. I assume it's just something with the environment that is causing it.

Speed and altitude will have nothing to do with it, although the compass is located on the leg of the aircraft, and you may not have realised but might've just struck the leg a tad while flying afar (by the looks of your map) on an object (not enough to break the leg, just having your hand covering it is enough to make it go out of whack momentarily).

If you're ever in flight and any warning of IMU or compass pops up, the reliability of control you'll have over the aircraft is severely reduced. If it's far away, use extreme caution to return it home, prepared for it to make a sudden, unexpected move as the Phantom is clearly confused about its whereabouts. If confident, use ATTI mode (it should do this automatically) to bring it home so the confused data doesn't take matters into its own hands. If it persists, again call DJI support.

Sorry to hear about this problem, but good luck for your future flights. [emoji3]

thank you for that clear and concise response.