Drone Crash on Min Speed Testing

I am testing minimum speed of our drone to check its Min and Max speed survivability. Soon it reaches its minimum speed, drone loses all controls and even it doesn’t take any command on manual takeover. It doesn’t give any fail-safe warning and crashes rolling nose down. This has happened twice.

Can you please check from the log and guide.

Drone Type: Fixed Wing Twin Motor Propulsion
Autopilot: Cube

Log File Download Link: https://www.dropbox.com/s/ntsyujletjw2ayc/2019-06-30%2011-38-58.bin?dl=0

2019-06-30 16:39:01 PX4: 1e7ed30b NuttX: 1472b16c
2019-06-30 16:39:01 PX4v3 00280027 33375110 37353832
2019-06-30 16:39:01 New mission
2019-06-30 16:39:01 GPS 1: detected as u-blox at 115200 baud
2019-06-30 16:39:01 u-blox 1 HW: 00080000 SW: EXT CORE 3.01 (107900)
2019-06-30 16:48:42 Throttle failsafe on
2019-06-30 16:48:42 Failsafe. Short event on: type=1/reason=3
2019-06-30 16:48:42 Flight mode = 1
2019-06-30 16:48:44 Throttle failsafe off
2019-06-30 16:48:44 Failsafe. Short event off: reason=3
2019-06-30 16:48:54 Throttle failsafe on
2019-06-30 16:48:54 Failsafe. Short event on: type=1/reason=3
2019-06-30 16:48:54 Flight mode = 1
2019-06-30 16:48:55 Failsafe. Long event on: type=3/reason=5
2019-06-30 16:48:55 Flight mode = 11
2019-06-30 16:48:55 Throttle failsafe off
2019-06-30 16:48:56 Failsafe. Long event off: reason=5
2019-06-30 16:49:16 Failsafe. Long event on: type=3/reason=5
2019-06-30 16:49:16 Flight mode = 11
2019-06-30 16:49:35 Throttle failsafe on
2019-06-30 16:49:48 Throttle failsafe off
2019-06-30 16:49:53 Throttle failsafe on
2019-06-30 16:49:53 Throttle failsafe off
2019-06-30 16:50:23 Throttle failsafe on
2019-06-30 16:50:23 Throttle failsafe off
2019-06-30 16:50:41 Throttle failsafe on
2019-06-30 16:50:44 Throttle failsafe off
2019-06-30 16:50:53 Throttle failsafe on
2019-06-30 16:50:53 Throttle failsafe off
2019-06-30 16:50:58 Throttle failsafe on
2019-06-30 16:51:11 Throttle failsafe off
2019-06-30 16:51:12 Throttle failsafe on
2019-06-30 16:51:14 Throttle failsafe off
2019-06-30 16:51:16 Throttle failsafe on
2019-06-30 16:51:27 Throttle failsafe off
2019-06-30 16:51:29 Throttle failsafe on
2019-06-30 16:51:45 Throttle failsafe off
2019-06-30 16:51:52 Throttle failsafe on
2019-06-30 16:51:59 Throttle failsafe off
2019-06-30 16:52:02 Failsafe. Long event off: reason=5
2019-06-30 16:52:04 Throttle failsafe on
2019-06-30 16:52:04 Failsafe. Short event on: type=1/reason=3
2019-06-30 16:52:04 Flight mode = 11

It’s looking like you simply lost RC to the vehicle.

Suggest doing a range check on your RC.

Peter

Dear Peter,

All these errors are coming after the crash.

OK, so stop looking for the easy answer, Peter :slight_smile:

That shows that the aircraft was desperately trying to fix the problem, but seemed to not have an control authority. Graphing the same for roll seems to show the same thing.

Around the same time, the servo voltage drops:

How are your servos powered? Would they continue to work at 5.5V (I’m guessing they’re high-voltage servos)? Any idea why that voltage may have dropped?

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