However :
Can you can provide a full log file for that flight that demonstrates that speed as the horizontal speed?
0.03 may be a suitable drag coefficient for a streamlined aircraft in forward flight but it would be much higher for any kind of drone in freefall. If you hold a dinner plate level and drop it, the drag coefficient will be greater than 1.0 before it tilts sideways as it falls. I’d guesstimate a coefficient of 1.0 as a first approximation for any non-streamlined object.
I was surprised that the drone accelerometer recorded such a speed, and even more that the terminal velocity calculator seems to clarify this, I agree too, that the drag coefficients is a variable that we would struggle to work out for my drone. Using the aircraft figure was just a guess but when you see that the drone has no real surface, area other than the bottom plate which is very small then I would say the drag would be very low. In the app a plate has a value of 0.001 which would be it falling edge first. I was interested to see what sort of speed it would reach and was very happy to keep it under control and land it safely. To be honest we will never know the true speed and I don’t think I will try it again! as it was a twitching time!!
Sorry i can not provide any log files as the drone is a bespoke home build with a self built flight controller, the only data i have is from the Telametry device i made, that records the speed from the accelerometer.
I looked at the original post and there no mension of horizontal speed, i was just trying something new to test my drone, and take part in the competition.
As for the drone that fell from the sky!! this was because of a ESC failure, Quadcopters have no redundency, so if one motor goes dowm then so does the quad. The return to home may have triggered but the quad was in free fall and smashed into the ground!
With mine i reduced the throttle to idle and kept flying, keeping it under control and landing safely.
Aircraft fly in all directions so speed can be recorded in any plane.
Anyway i have had my say and recorded my speed, i enjoy flying and am totally new to all this drone stuff! Building my own and not even knowing how to fly it has been a great experiance and i still am amazed that it even fly’s, i want to learn more and this group has been a perfect source of information that i need.
Thanks and stay safe
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The surface area isn’t relevant to the drag factor (or at least not for this purpose, we don’t need to discuss Reynold’s Number here, thanks very much). At the scale and speeds relevant here, the drag factor is primarily a function of the degree of streamlining relative to the direction of airflow.
As previously stated - that data is on Airdata. Airdata ONLY shows horizontal speed. As has been proven.
This is now an end of it.
Thankyou.
dji mini 2 starting point
36.71 mph
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Top job!
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It’s good that it’s got a bit more oomph in it 
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Thank you very much 
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Congrats @Mind_the_gap how did you manage to get yours to that speed? I’ve been trying and trying but just can’t do it 
lol 
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Thanks @SirGunner. I have to admit I have been trying myself to do the same thing. I guess it must of been the high wind during the 2nd of this month. To be honest, I’m not sure I would chance it on that wind. Against it, it did struggled a lot to move and even on standing, it got dragged off. Finally lowered the altitude and managed to do the trick.
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Brave man in those winds! Well done mate. Mine tops out at exactly 43MPH. I think your new record will really take some beating
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To be honest, I didn’t realise that it managed to get that fast until yesterday. I would say, that I would not be trying to beat it myself in a rush.
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I was impressed with 16m/s ( 35.8 mph ) from my Mini 2. Show me what speed you have topped and why I am slow.
Clear, dry day with observer in radio contact the whole way.
Close but no cigar 