Airspeed reducing below stall speed even at 70% throttle

ArduPlane Plane 4.4
1

@MagicRuB @tridge
My plane was cruising at 45 kmph to 52kmph smoothly, then suddenly airspeed started dropping and without pitch controls given, plane went into spin & pitched down & increase airspeed and recovered.
Then I activated RTL and then after a moment of time airspeed dropped & plane went into spin and could not recover.
I have crashed 7 planes with the same problem. I dont have an airspeed sensor on it.
I am attaching .bin file link please check it and give a solution.

My plane is a semi-glider type with 2.4m wingspan, 1.3m fuselage length with solid midwing and boom rod with standard tail and weight of approx 4.2 kg

2

The link is locked. Remove the password on the file so we can download it and look.

Also, tell us more about the plane. Size, configuration, model, etc.

3

I have updeted the link, do check it out. Qnd i have updated the plane config as well

4

It looks like your motor quits responding to throttle demand. The following plot correlates commanded throttle with measured power draw from the battery. Maybe a problem with your ESC or motor overheating.

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1 Like
5

Also there is Airspeed difference between DCM estimate and GPS airspeed, qt one point, DCM AS was 8.2m/s qnd GPS was 4m/s

6

I have T motor 55A UBEC esc qnd my max current during autotakeoff is 49-52A for 45sec approx then max current during flight is only 18A and average is 7A
I dont k ow why this issue with Esc is coming.

8

Were your 7 crashes all with the same ESC/motor?

10

Is the ESC getting enough cooling?

11

Yes,I have been using AT3520 moror with 15inch foldable prop and according to the datasheet, it gives 4.2 kg thrust at 100%

12

I dont think so, the ESC is inside the midwing section of plane which is fully covered. No vents for airflow is there. I am trying with 60A flame series esc, it has a big heat sink outside the packaging of circuit, so it might help in better discipation of heat.
I qm trying some parametes as well like:
TECS_SPDWEIGHT : 2
STALL_PREVENTION : disable (This was enabled earlier)
But since i dont have a dedicated airspeed sensor, so I recently read online that i should disable it in this condition)
And I am doing Autotune for pitch and roll axes at 3 level of aggresiveness and increasing the aggeesivness slowly.

13

You are missing the point of what you’ve been told. This is not a parameter issue, it’s a hardware issue. @kd0aij 's graph clearly shows the FC demanding more throttle but based on the power output, nothing is happening. That’s not fixed in parameters. Install the heatsink and try to find a way to get some air flowing over it. There is also a chance if you’ve over heated this ESC too many times it may already be damaged.

I don’t recommend turning off stall prevention.

14

I’d suspect that the ESC is overheating and limiting motor current, resulting in loss of altitude.
Then the autopilot commands more throttle (which has no effect) and progressively adds up elevator until stall occurs.

15

I will get some things done for the ESC heating issue and after this implementation I’ll update you.
Thanks for the help guys.