I have been flying the Alta 8 for 5 years, with about 200h on the platform. I recently started flying the X and i have come across a potential safety issue that i wasn't aware of. It seems that in Atti and GPS mode the max climb rate of the aircraft is dramatically reduced when flying within 5m of the take off height. I discovered this when test flying an aircraft, doing a low pass toward some rising terrain and i had my heart stop for a moment when the aircraft did not seem to climb when a full throttle input was given. After doing some more testing it appears to reduce vertical speed to around 1.5m/s until it passes 5m and then it will start to climb as normal. I have tested this on two aircraft and they both respond the same. I have been in touch with freefly, they are aware of the issue and are working on a fix. I wanted to post here so that hopefully no one ends up flying into something when the throttle unexpectedly doesn't respond as it should. I tend to do a lot of fast low shots for car commercials and it doesn't take much imagination to see how this issue could potentially end in disaster. Obviously if you are aware of the issue you can work around it. So i'll be using manual for all low flying shots from now on. Cheers, Andrew
Hey Andrew, There is a setting in the advanced settings which gets rid of this when you are above your take-off height, but I haven't found a way of getting rid of this if your operating below your take-off height. Don't have my X booted up in front of me to see which setting it was, but something to do with near ground warning and there was one for 10m and then 5m
A few days ago I had a similar problem. we were in a shootout following a vehicle ... the take-off and landing zone was 1 km away. At the moment of wanting to land it seemed that the drone did not want to descend. the difference in height with respect to the take-off point was -40m. it seemed to go down slower than 0.5m/s or less with the throttle fully down. After a long time I managed to land. It only happened once.
I had same problem. Now only way to fly below takeoff attitude is to fly in manual mode. Other solution is to modify some parameters in Alta QGC but it seams not 100% safe. There is link to PX4 forum with explanation: https://discuss.px4.io/t/descent-and-climb-rate-limit-when-near-ground/20649 I hope there will be fast update to this issue. The best solution would be to separate the landing parameters when the drone is in RTL mode from those in position mode and attitude hold.