GPS Rescue Weird Begaviour

[grim apex]

Hi. I've been using my GPS rescue for some time but still can't figure one thing.
In stage 1, the drone flies up for a second (5 meters), which is OK.
But when it kicks in the stage 2, the drone dives and loses around 10 meters - this is not cool, since I already crashed few times when activated too low.

I don't normally use it to land, but since I am going to Swiss Alps in a week, I want it to be absolutely perfect.
It cannot dive into a mountin when activated low.

What could be the problem? My hover throttle with all the things I normally fly is 24, therefore I set it for 1240 in the stage 2.
Here is a video: https://youtube.com/shorts/KlgntRpWhKI?feature=share
I have no blackbox for this, the chip was already full.

[eternal imp]

what are your rescue settings? this is what I use, but you really want to pay attention to the circled value here:

so on another drone of mine that value is 1400 because its heavy af

if you left this default of 1280, then that will be perhaps too low for many drones.

[grim apex]

As I said, I measured my throttle hover and it is 24, so I set it to 1250. I will experiment with that, but I think the "set the value accurately" is misleading if I should go higher than 1250 in my case

[eternal imp]

Have you noticed the altitude value doing weird things during this behavior? Wondering about the barometer data

[fossil widget]

Can I check that you are using 4.5?
Normally it will climb, then rotate, then pitch forward.
Ordinarily the quad overshoots the intended climb, and while rotating, the thrust from yawing minimises the drop after the overshoot.
Can you maybe look out for exactly when the drop occurs?
If it happens when pitching forward, and if the quad is heavy, and if the throttle maximum is not high enough to maintain altitude at the pitch angle, then you'll lose altitude when you pitch forward. You may need higher max throttle in this case.
The other possibility is that the throttle PIDs are not ideal for your quad. You can make a log using GPS rescue throttle debug and it should identify if the PIDs for throttle need messing with.

I think that in the video you are testing GPS Rescue within the minimum allowed distance. This causes the quad to not rotate, but immediately fly out to at least the minimum allowed distance in order to have a brief period of straight flight to orient the IMU. Because there is no yaw, it can drop a bit at this time.

From looking at the video, I think you are initiating the rescue very close, and I think the throttle PIDs are not quite ideal for this particular quad. At a guess both P and D need to be higher. Try about 25% higher and if it is better, then increase another 25% (ie go 25% up, then 50% up, on what you started with). When they are too high the quad will sort of go up and down during the return rather than staying level.

[grim apex]

@fossil widget Yes, I am on BF 4.5. I can record a log tomorrow. I screenshotted my BF settings. Max throttle of 1750 should be enough to fly away without any problems 😄 The distance I turned my GPS rescue ON was arounf 25-30 meters from takeoff. For the PID part, I tuned it using the basement method. It should all be correct from looking at the graphs in PID toolbox

[fossil widget]

The PIDs to look at are the gps rescue PIDs, not the flight PIDs. GPS rescue PIDs can be found in the cli. Type ‘get gps_rescue_thr’
Read the wiki about the rescue PIDs.

It definitely is not rotating. It flies away at speed as soon as height is attained. This suggests that it doesn’t know which way to go. This happens when the quad has not been flown nose-forward in a straight line for enough time to orient the IMU from the gps data. Or it can happen if initiated inside the minimum distance or if Mag is enabled but it is not configured properly.

Normally quad should climb, then yaw to rotate. In your video it climbs, then without rotation it flies away in a big arc. That’s not normal.

When the immediate flyaway is needed to re-orient the IMU, it is more aggressive than the standard slow pitch forward and there can be altitude loss. Yaw usually adds altitude and offsets the tendency to drop a bit after the climb.

With higher rescue throttle PIDs you’ll get a more aggressive response to altitude errors. This may not entirely solve the problem but it may help.

You perhaps could apply a greater climb value if you are initiating relatively close to ground. The climb should be enough to get you well above ground and trees or whatever.

[grim apex]

I will try it today. It is weird because the arrow was pointing in the right direction in my OSD and I was way beyond the minimum distance. I will try to go much further, try to increae meters to climb aswell.