Hello Ardupilot experts.
I have a question regarding the crash of my first FPV plane equipped with Ardupilot, weighing less than 100g.
1.Issues encountered
Channel 1-4 was held and the plane was out of control at flymin 0:33, then the throttle suddenly went to zero, the plane stalled and could not recover, and it crashed.
I wanted to avoid crashing onto the highway, but it would have been dangerous to lose control. Fortunately, the plane veered left, which resulted in the plane crashing into the riverbank.
The FPV-DVR video is below.
What I want to know to prevent recurrence
Q1.Why does ch6 move even though it doesnât respond well, and ch1-4 hold and become uncontrollable?
Q2.Is there a problem with the receiver? Or is it a problem with the settings of the FC with Ardupilot?
Q3.What measures can be taken to address this issue?
3.Components that make up the RC system
ArduPlane V4.6.0-dev (075a5c3c)
Transmitter:Futaba T16IZ_Super
Receiver:Futaba R2000SBM
FC:MicoAir405Mini
4.The log confirmation screen for Mission Planner is shown below.
6.The causes and solutions I came up with are below.
Please let me know if there are any errors.
*On the day, in addition to multiple radio-controlled aircraft, there were two DJI drones flying that were transmitting images at the same 2.4G, so the 2.4G band was busy.
*The percentage of packets that could transmit information correctly was low.
*Is the SBUS to RCin conversion logic slightly different for ch1-4 and ch5-8?
*Next time the same situation occurs, I will manually set it to RTL, wait for it to get close to the runway, and then use DisAim to bring it down.
I would appreciate your assistance in identifying the cause and preventing recurrence.
Thank you for your reply.
If we assume that the cause is gimbals, that certainly explains why only ch1-4 doesnât work.
If your Ardupilot plane was in a similar situation, what action would you take?
Iâve only ever flown regular radio-controlled planes, and this was my first a plane with a flight controller, so I was at a loss when something went wrong.
I still donât understand the relationship between the transmitter/receiver failsafe and the behavior of Ardupilot. Even if I change the behavior of the transmitter/receiver failsafe, when I turn off the power to the transmitter, the roll, pitch, and rudder become neutral, the throttle becomes hold, and after a short time, it becomes RTL mode, so I thought that the transmitter/receiver failsafe setting would not have much effect.
SBUS usually can send a âno-pulsesâ signal. Ardupilot will recognize that as a radio failsafe and start whatever action. I donât know Futaba well enough to say how to set that up. The other option is to have the throttle channel drop below the THR_FS_VALUE and this will also trigger failsafe. You could do that by changing the throttle from âholdâ to -110% (or something like that, youâd need to verify the value)
If I got no or intermittent manual control I would go for RTL*. (I have my planes configured for automatic landing and tend to have a mission that includes automated landing configured).
* This would involve setting mode switch to RTL and commanding GCS operator to set mode to RTL as I typically fly in a two man team (I man the GCS).
Another possible source of loss of control may be incorrectly configured trainer mode on the radio though IMHO it should not enable trainer inputs without valid trainer signal which should not happen without actual connection.
My Futaba SBUS receiver sends as long as it donât get the first signals from the transmitter a zero on all channels and sets the failsafe flag. After first receive of good transmiiter signals it allways gives a non zero signal on all channels. In case of lost receiving signal it still gives non zero signal on all channels but sets the failsafe flag. In that case the output signals are as defined (fixed values or last value or what ever)
But ardupilot directly detects Radio Failsafe as it monitors the flag.
Thanks! With the OPâs radio setting all the channels to hold will that prevent the failsafe flag from being triggered or sent? I only ask because those flat lines on the RC data sure look like an old-school failsafe, especially with the radio set to Hold.
The throttle failsafe was checked. However, the trigger value was left at the default and even when I pushed the stick all the way down, it didnât go down to the threshold value, so it didnât seem to work.
I havenât been able to confirm how the failsafe flag is sent via SBUS.However, if you turn off the transmitter, it will switch to RTL mode,
so I think the failsafe information is transmitted from the receiver to the Ardupilot via SUBS.
The MAVlink on my Ardupilot airplane is only effective when the USB cable is connected on the ground and cannot be used during flight,
but if I could connect it via a wireless connection separate from the RC, it would be great to have a completely dual-system control.
When I fly a larger, full-fledged unmanned aerial vehicle in the future, Iâd definitely like to attach MAVlink wirelessly as well.
Certainly, the head tracking of my FPV aircraft is done by connecting the head tracking signal (PPM) output from the SKYZONE04X goggles
to the transmitter via a trainer cable. If there is a problem with this setting,
it is quite possible that only the head tracking will work and the other channels will freeze.
I now realize that this is also something I need to be very careful about in the future. Thank you.
When 1ch-4ch were on hold, it didnât occur to me to try turning off the trainer master switch.
This is the screen that appears when I start up the aircraft with the RC transmitter off, then I turn the transmitter on,
and then I turn it off again.
It appears to be working as explained above.
On my Futaba transmitterif you use it in trainer mode either the trainer or the trainees signal is send out not some channels from trainer and somee channels from the trainees port. So in that case how you control to use channels 1-4 from trainer transmitter together with channel 6 from trainees port.
If you completly switch to trainees port it is clear that you get flat signal on channels 1-4 but no failsafe flag.
Thank you very much for teaching me so much.
I would like to study Ardupilotâs many functions one by one so that I can use them well.
I think the fence function is effective in places like our RC airport, where there are highways, bridges, and power lines around where planes should not approach. If this function works properly, I think it will be possible to land the plane on the riverbank even if the pilot makes a mistake or the radio link is lost.
Yes, for my FPV plane, I can connect the PPM signal from the goggles to the trainer port and enable only channel 6 as the trainer port signal.
I keep the other channels off so that the signal from the transmitter itself always takes priority.
When itâs working properly, itâs fun to see the direction I like as shown below,
but I learned this time that if I make a mistake in the settings of this part, it can have scary results.
Yes, I think thatâs also an effective solution.
Currently, the takeoff weight of my FPV plane is 98.2g.
If this exceeds 100g, the procedure to obtain permission becomes very difficult under Japanese law. There is a limit of 1.8g for hardware upgrades.
