Wookong M GPS Mode - Fair Warning

[sochin33]

laurents, don't confuse the flight controller failsafe with a possible receiver failsafe, they are completely different. When the controller enters failsafe then it should simply follow DJI ' program for the type it is on. When a receiver goes into failsafe due for example loss of communication with the transmitter it typically will send a default set of instructions that the user enabled to the controller. Depending on your receiver it can be fairly easy to enable it without knowing you set it up and it will send a bunch of command that don't make any sense. For example on the DX9 - insert bind plug, place transmitter sticks and switches in default posistions, when receiver flashes orange remove bind plug and now turn on transmitter. Now consider what just happened. If you for example had your yaw and roll sticks off center, those are now your defaults on a loss of signal to your receiver. Your copter would spin and roll into a spiral.

Perhaps I am misunderstanding what you are saying pfarmer.
The procedure that you outlined (bind plug .. turn on transmitter is the DX9 procedure for FC failsafe is it not ? Although there is also a push of the trainer button.
If the FC/receiver failsafe is setup correctly, via the procedure you outlined, and loss of communication happens, then I thought that the FC(DJI based) completely took over control of pitch,roll,yaw and altitude, regardless of where these controls are set during the FS bind procedure.Is this contrary to your understanding ?
I have had a loss of communication FS event with my WKM/DX9 and it did exactly what it was supposed to do: increase elevation to 20m ,come home, and then land. I have had two NAZAs which did the same thing when I turned off the radio.

 

[pfarmer]

Sochin33 - I think you and I are on the same page, that is the failsafe for the DX9 procedure for the receiver. In my case it also sends a RTH command to the flight controller but you could omit that. The Naza and I believe the Wookong failsafe is based on not seeing a change in receiver output. Basically I test this by turning off my DX9 transmitter to simulate a simple lost of communication for any reason such as the copter's orientation placing the antennas in a rf shadow. After a few seconds the receiver will then send stick positions and switch positions to the flight controller and the landing gear. Basically this is all neutral sticks, the switch position that puts down the retracts, and the switch position for RTH which could be optional. You could eliminate RTH for example and maybe put a small amount of yaw with a small amount of pitch to see if transmission could be recovered by a change in position. If the Naza did not have its failsafe set for a frozen receiver the copter would simply circle maybe a slight climb or descend based on default throttle. Now if you had setup the flight controller failsafe after 10 or 20 seconds (have to look that up) the flight controller would see a frozen receiver (no change in output) and send the copter home. I can tell what gets initiated by timing. Before relocating my satellites, I saw this a few times with copter almost directly over head at 400 feet and pointing towards me. It would sit there and I could do nothing until the flight controller decided it was time to come home on lack of receiver output. By putting in the RTH in the receiver's failsafe the copter starts coming home immediately (which you can abort by swapping modes once communication is restored). Now keep in mind what could happen if sticks are not set to neutral and the Naza failsafe is not set. The flight controller would see the non neutral positions and respond possibly fatally.

 

[pfarmer]

Sochin33 - just be clear there is a 3 second window where the flight controller could respond to the loss of communication by going crazy if the sticks are not neutral as set during binding. After that it should enter into a hover for 15 seconds where you can stop the RTH. After the 15 seconds it will start home (a total of 18 seconds) and would need to be aborted by swapping modes.

 

[sochin33]

pfarmer-- Good explanation on RTH, etc. Also, thanks for your discussion of group effects, etc.

 

[pfarmer]

Sochin33 - I believe that many of the problems blamed on the flight controllers could actually be incorrect failsafe settings especially since few understand the failsafes that many receivers get set without the knowledge of the users. The DX9 has three the described one is the preset. For example Smartsafe is set by setting the default throttle position by powering on the transmitter and receiver in bind mode at about the same time. Loss of signal and throttle will return to the default position. The other is Hold Last Command. This causes the receiver to default to the last set of commands. If the flight controller doesn't have a failsafe set for loss of signal you very well could experience a fly away.

 

[sochin33]

Sochin33 - I believe that many of the problems blamed on the flight controllers could actually be incorrect failsafe settings especially since few understand the failsafes that many receivers get set without the knowledge of the users. The DX9 has three the described one is the preset. For example Smartsafe is set by setting the default throttle position by powering on the transmitter and receiver in bind mode at about the same time. Loss of signal and throttle will return to the default position. The other is Hold Last Command. This causes the receiver to default to the last set of commands. If the flight controller doesn't have a failsafe set for loss of signal you very well could experience a fly away.

Yes, I remember reading about those modes. I always check in WKM or NAZA assistant to make sure my preset FS is working. I could see how a Hold Last could cause a fly away !