Max power issue with propellar guard; going down unexpected

[Yokurt]

(Already posted on Max power issue resulting MM crash!, but as advised, new thread for new case)

I'm new to flying drones and I was flying with propeller guards on. I got several max power issues, but I still tried the selfie modes. It stopped and I got the 20% battery warning. I canceled RTH as I was next to the start point anyway and wanted to get it manually down. It was hovering in place and then went down without me doing anything. Luckily nothing seems to be broken, but I'm still worried.

Thanks for any analysis!

 

[slup]

Yeah ... we have seen this scenario before.

You flew with the prop guards on making the Mini much more prone to both drift out of position & become unstable ... this forces the AC to increase the thrust. In your flight you got several "notEnoughForce" warnings, this every time the engines became maxed out. The winds in your flight coming from Airdata.com says 6,5m/s with gusts up to 11,8m/s ... take away 30% of that due to that they use the Spark profile for the Mini & you end up on 4,6m/s with gusts on 8,3m/s. This is way over the top for flying with prop guards ...

In the end of the flight when you lost altitude without command the left back engine had been maxed out nearly the whole flight & the software probably tried another approach to keep the AC stationary by means of increasing the tilt inclination ... it slowed down both front props as it couldn't speed up the left back more. This resulted in a to low vertical thrust & the AC starting to lose altitude. A bit later you yawed a bit & that made thing's worse & the AC lost even more vertical thrust and it descended even faster.

 

[Yokurt]

Thanks for the fast analysis!

So there's nothing wrong with my MM, but in general the prop guards are more for indoor flying?
I thought they're also outdoors a good idea for a beginner. But the next days I'll try without them.

 

[slup]

Well ... this one is kind of part "suspected AC fault" due to that strange behavior to cut revs. on the front props which leads to to less vertical thrust ... AC going down. And part pilot error due to flying with the prop guards on in windy conditions ... they act as sails & put heavy strain on the propulsion system. Never use them outdoors ... the only exception I can think of is if you're in a very sheltered area going really low & close to things, which wasn't the case in your flight with all that open farm land.

We have seen this strange behavior regarding cutting front prop revs on a few occasions lately ... when the rear props can't rev up more to increase the tilt angle (lift the rear) it seems to cut it for the front instead. But nothing is proven yet about if this is a deliberate strategy to for instance decrease the many blow away's we've seen ... Either way you faced a blow away situation if the fronts didn't cut the revs or as I suspect in this case the lower revs made it to drop land.

 

[Yokurt]

The day before that I got a wind warning, it also was a bit windier than that day. When flying lower it disappeared. But at that day and flight, I only got the max power warnings.
So, at least with prop guards, max power issue is also kind of a wind warning...

 

[slup]

The day before that I got a wind warning, it also was a bit windier than that day. When flying lower it disappeared. But at that day and flight, I only got the max power warnings.
So, at least with prop guards, max power issue is also kind of a wind warning...

As far as I have seen lately, that warning have corresponded to engines being maxed out ... in that situation the AC no longer have headroom to adjust the tilt inclination sufficiently, leading to not enough air speed. The AC feels unresponsive to vertical directed stick inputs & face serious risk of being carried away by the wind.