Here is my experience so far.
I bought a second hand Phantom 4 (not a pro, rtk etc. - a regular P4) but well looked after:
- Refreshed firmware
- Removed gimbal (note - there are two cables -a flat cable and a JST-GH connector cable)
- calibrated compass with new payload
- Flew with payload (high due to large LiPo and a fan on the payload). Using it for some data gathering (terrain mapping for geography research project). Payload weighs 480 grammes. Had to get the CoG right. Can fly with a smaller battery which should reduce weight by around 100 grammes (next steps)
What I found:
- In order to get all telemetry down (i.e. battery level, speeds, heights etc), you need to have the gimbal cables attached at boot up. After these, those can be disconnected and you still receive telemetry. I saw a suggestion on the older P3s that you can confuse the system by attaching a gimbal plug there instead. It does not work for this model. If somebody knows a better workaround, let me know
- DJI GO 4 app allows you to turn off the downward VPS (that is mandatory in my case, as I have the payload obstructing the sensors). This action must be done with gimbal attached. Interestingly, I can still hear the clicking of the sonar even after turning it ogg. More interestingly, after exceeding 10-20m of height, I get the solid red LEDs (critical error). The error is:
"Downward sensor error phantom 4 aircraft unstable at low altitude"
Which is rather interesting ... as I have VPS switched off. I guess you cannot truly turn off that system.
Flying in strong / moderate winds with that payload and said error ( doing slow and controlled movements) yielded satisfactory results. I will slowly expand envelope.
Any tips / suggestions / experiences welcome.