User sar104 on the Mavics Pilot forum has done extensive testing with his Mini to better understand the relationship between deformed props and uncommanded descents. The full discussion is here: https://mavicpilots.com/threads/mavic-mini-uncommanded-descent-tests.86237/ Ice_2k originally referenced this information on another thread but it seemed to get little attention. Sar104's information and conclusions are based on relatively controlled testing and data versus the anecdotal information that is running rampant in this forum. Out of everything I’ve read, I lean towards sar104’s explanations because it is data based and there is logic to his analysis. For those of you that want a summary, here is my understanding. I apologize if I misstate his information. - He was able to flatten the rear props by improper storage in the Fly More case in just 12 hours. With the flattened props, he was able to produce an uncommanded descent (UD) while flying sports mode and pushing the drone to max RPMs. Previous to flattening the props, he was not able to produce a UD.
- He believes that at or near max RPM’s the props will experience additional deformation and will not be able to sustain the necessary thrust to achieve the required front pitch. The drone will reduce the front motor RPMs to try to maintain pitch because it cannot increase the rear RPMs at max. This reduction in the front RPM’s will cause the drone to descend. It looks like the FC prioritizes forward pitch over altitude and causes the drone to descend.
- He repeated the same test the next morning and felt that the rear props reduced some of the deformation but he was still able to reproduce the UD.
- He then runs the same test under firmware 1.00.05. He observes that the flight characteristics have slightly change but with the flattened rear props, he is still able to produce a UD. He concludes that 1.00.05 gives additional warnings but does not eliminate UD’s.
- A common misconception on this forum is that you can achieve forward pitch with all 4 motors running at roughly the same RPMs. This shows that many users do not understand the basic mechanics of quadcopter flight. The rear props always need to spin at a higher RPM than the front props to sustain forward pitch for horizontal velocity even when you have all good propellers. All of his data demonstrates this if you know how to interpret the data. In addition, he specially states this in his description of what is happening during the drone flight. If you do not believe this, then please show your RPM data with forward horizontal velocity to prove otherwise.
Finally, at the end of his discussion, I asked him what program he is using the chart his data. It is Wavemetrics Igor Pro and seems to be a great way to graph RPM’s vs Pitch vs Horizontal Velocity vs Vertical Veolcity.
Randy
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