Servers by jDrones

Single Copter - (almost) Maiden Flight


( .) #1

We are new to single rotor airframes. Recently we flew our first custom designed single copter. The airframe was 3d printed.

Link to picture:

Short spec:
5 inch propeller,
EMax 2206 2750KV,
4S battery,
3DR PixHawk Mini autopilot,
3,5 (stable) software.
The airframe selected in QGC as single copter.

Link to flight footage:
Link to .bin file:

As you can see from the video the copter heavily drifted and crashed eventually. It flew in AltHold mode. There was some light wind. It flew once before in the Stabilize mode. At that time it hoovered much longer but also went nose down at about 30 deg angle when we tried to make it fly sideways to stop drifting.
The PIDs were increased by 20% from original settings based on initial short trials inside a house.

We are looking for some guidance and help from more experienced members with interpretation of data-flash logs, and for proper PID and other settings.

Single-Copter - Loiter mode - crashed flight
( .) #2

Single Copter - crash flight in Loiter mode.

Since February 2018 we have had many succesful flights in loiter mode, similar to the one shown in this video:

But one time after changing the battery the vehicle was completely crashed:
No error messages observed via telemetry link on laptop prior to take off.

Link to crash .log file:

Again, we are looking for some guidance and help with analyze of the log file.

(Colorfuljune) #3

Is your copter oil or electrics ?
I think it crashed because of the servo power failure suddenly. Maybe vibration Large range

( .) #4

It is electric so far. Thanks for suggestions. What are you basing your diagnosis on. What parameters in the log file indicates it’s a servo.


(Andrew) #5

Hi Colorfuljune, check the videos - the links are working now.
You may be right about a servo failure, but what in the log file indicates it is a servo?

(Colorfuljune) #7

Do you have a log of succesful flights ? I’d like to be able to look at it and make an analysis of
the two logs.

(Colorfuljune) #8

It’s just a personal guess. Multiple parameters need to be analyzed in a comprehensive way。If there is a log of succesful flights as a reference , it will be better. May be can find the exact problem.

( .) #9

There is log of succesful flight as a reference,

(Colorfuljune) #10

POWER-VServo in the log file.

(Colorfuljune) #11

It was really a perfect flight. You can find POWER-VServo in the log file,this parameter indicates it’s a servo

(Andrew) #12

Jaco and I (we are working on this project) suspect that two servo actuated flaps could jam each other. In such case two servos should show failure. How to examine each of the 4 servos separately?
Looking at the POWER-VServo parameter we think we see all of the servos together.

Another thing is - what about this Mag Field anomaly message? Could this be also a cause? Nothing changed however. Same field, same place, almost same time for both flights.

(Colorfuljune) #13

If you want to examine each of the 4 servos separately, there are two methods as a refercence:
1、You can use Rudder tester to examine.
2、There is an option in Futaba radio control 。

I do not know what it is Mag Field, so I do not know what happened.

(Andrew) #14

Thanks a lot Colorfuljune. You’ve been of great help.
When I said that I’d like to examine each servo separately, I meant to examine them in the log file of the crash, not the physical servos themselves.

Would you happen to know how to interpret Line Numbers in graphs generated from log files (it’s the horizontal axis). Is Line Number time in seconds, milliseconds…? Or something else yet?

Thanks a lot

( .) #15

Thank you for your help. We have just learnt that the parameters we are lokking for are:
Q1, Q2, Q3, Q4 under AHR2.
That would mean it is possible to examine individual servos by looking at those paremeters in a log flight file.

(Hubert) #16


I quickly analyzed the VServo parameter and the voltage drop appears after the platform was on the ground (seems to me).
I personally would rather focus on MAG and GPS.

According to the servo checking in the .log. It is impossible to check it there. Servo does not report any feedback - it is one way communication. You can only see wether the command has been sent to the servo, you will not see if the servo moved.

Regards :slight_smile: