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Failsafe for planes

#1
Sorry if this is in the wrong place, please move if necessary.

I've been flying quadcopters for a couple of years now and I am just now looking into flying some fixed wing aircraft. With the quadcopters, you would setup a failsafe on the FC so in event of a radio problem it would either RTH or hover. I was wondering with planes is there a failsafe? I am guessing that it's an additional unit that would need to be bought and wired in? If so what are some ones to look at?

Thanks,

Toshiro.
 

Fluburtur

Cardboard Boy
#2
You could use a flight controller with GPS so the plane comes back or just set the receiver so all the channels go to neutral and hope.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#3
Depends on the receiver, but most these days have a failsafe. The simplest return to neutral (and if you don't setup the more complicated ones, that's what they'll do) but the better ones let you set the control state.

If you can set the control state, generally you want to set the plane to turn with motor off, trimming it to glide in circles to the ground. The plane will still drift with the wind as it sinks, but not much more than that. Deploying flaps/spoilers/crow in this case is a good idea.

As for can and how, that will depend on the radio gear you have. Each brand is slightly different. Some you set through the radio, some through the bind process, but if you can't find it in the radio's documentation, let us know what you have and someone here can step you through the process.
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#4
There is a "failsafe" mode in most modern radio systems and you set it up so that the channels default to a particular setting or position upon signal loss. Additionally if not set the ESCs normally cut power to the motor if there is a loss of signal for more than 2 seconds.

As for a return to Home function and a possible landing there are quite a few issues of safety to overcome. Firstly Quads land vertically and aircraft generally do not. Most quads are relatively lightweight compared to the aircraft we fly. Most quads travel at lower speeds than the models we fly are capable of.

In short in a model aircraft the idea of a large plane doing a landing approach, unannounced, and possibly through obstacles like trees, houses, traffic, spectators, and members of the general populace brings great fear to most of us.

My failsafe is set to cut the throttle, deploy the flaps, (for drag only), and if using stabilisation a gentle rudder only turn.

On my to do list is a ballistic parachute to be controlled by a servo which is activated upon loss of valid radio signal but then, whilst I have a design, time and funds have pushed it down the list for now!

Have fun!
 
#5
I tried and tried to get the fail safe on an FrSky X6R (I think that is the correct model) to work. I was not able to get channels other than 1 to return to a default. At least I got the throttle to cut on loss of transmitter signal. I could never get the servos to return to a neutral position.

Mike
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#6
Odd. Never played with a X6R myself, but I've run both X4R's and X8R's (and a small host of D-series RX's) and gotten them setup fine through the radio. Heck, if they weren't set, my radio was pretty persistent in complaining about it.

Hard to say offhand whether it's a bad firmware or method. FRSKY has been known to let a few bugs slip through on their RX's from time to time, but this is the first report I've heard of an uncooperative failsafe. Are you using a Taranis or external XJT module?
 
#7
I tried and tried to get the fail safe on an FrSky X6R (I think that is the correct model) to work. I was not able to get channels other than 1 to return to a default. At least I got the throttle to cut on loss of transmitter signal. I could never get the servos to return to a neutral position.

Mike

If you followed the instructions you might have a faulty unit. Failsafe works fine on my X6R.
 
#8
What ever failsafe setting you choose make sure the throttle goes to minimum/off.

Failsafe is more than what to do if during flight the Rx looses Tx signal.
- On the bench
- In the pits
- After a landing and putting things away (this is where I have most often seen a Tx turned off before disconnection of the flight battery)

I've seen more non flight situations of a Rx loosing the Tx signal than in flight.
 
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#9
I tried and tried to get the fail safe on an FrSky X6R (I think that is the correct model) to work. I was not able to get channels other than 1 to return to a default. At least I got the throttle to cut on loss of transmitter signal. I could never get the servos to return to a neutral position.

Mike
Which method of failsafe did you use?
- pressing the F/S button (in which case what the the Tx setting? receiver?)
- on the Tx, Hold, custom, No pulses
 
#10
Which method of failsafe did you use?
- pressing the F/S button (in which case what the the Tx setting? receiver?)
- on the Tx, Hold, custom, No pulses
Transmitter is a Taranis running 2.1-ish OpenTX.

The transmitter was on, sending what I wanted the default to be (throttle off, neutral control surfaces). I then pressed the F/S for less than one second. The green light on the Rx flashed twice. I then powered off everything (Tx, Rx, ESC, etc).

I then tested by turning on everything, setting the control surfaces to non-default using the transmitter and powering off the transmitter. Nothing happened - the control surfaces did not move to a neutral position with the loss of the Tx signal. I was not testing the throttle at this point.

I later tested the throttle and noted that it, at least, returned to 0 on transmitter power off. That is: the motor was spinning. After I turned off the Tx, the motor stopped within 2 seconds or so.

The Rx is in the new FT Cub. Since I plan to use it as a seaplane, the Rx is saturated with HD Corrosion-X (or something like that). Basically, I followed the F/T "how waterproof your electronics" exactly. Perhaps I damaged the F/T switch? But yet, the green LED does blink when I press it. I have not tried a re-bind. The receiver was already bound before I water-proofed it.

Thanks,

Mike
 
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Craftydan

Hostage Taker of Quads
Moderator
Mentor
#11
I had a suspicion this was what was messing you up.

Mike, if you look in the model setup page (first page after model select) menu on the radio, there's an option to setup the failsafe toward the bottom, right after the bind.

When you're using a taranis, it's better to set it up from there. If it's not pre-set to "receiver", a manual failsafe through the bind will be overwritten, with some versions going as far as overweighting it with "not setup".

Power on both TX and Rx, pick custom and set, and from there you can then set the response and position of each channel. From there, it should stick.
 
#12
Well, I kind of answered my own question. After poking around some more I discovered as many of you have mentioned that on RC aircraft the failsafe is in the receiver. I have a Spektrum DX6i with the AR610 6ch DSMX reciever. And according to the AR610 manual when failsafe kicks in it goes into a low throttle mode and all other channels recieve no input and are inactive. It would be nice if it would do the slow circle thing, but I guess this is better than nothing. At some point I will be switching to my FrSky Taranis x9d+, but the Spektrum is what I'm using for now. Is there a recommened FrSky reciever for planes? Or will an X4R work fine? And thank you to everybody who replied!
 
#13
The default is not set
screenshot_x7_17-08-11_03-34-02.png
Hold I would not recommend
screenshot_x7_17-08-11_03-34-10.png
Receiver is where pressing F/S on the Rx will work
screenshot_x7_17-08-11_03-34-21.png
No Pulses - try it, make sure it THR is on it goes off... if off stays off
screenshot_x7_17-08-11_03-34-28.png
Custom, after setting that select set, scroll down to the THR channels and set it to -100%
The broken line is the current channel out put
The solid line if the failsafe setting
A quick way to match the setting to current channel output is to
- select the ch
- press ENT
- press ENT again but keep it pressed
screenshot_x7_17-08-11_03-34-31.png screenshot_x7_17-08-11_03-34-52.png
 
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#14
Well, I kind of answered my own question. After poking around some more I discovered as many of you have mentioned that on RC aircraft the failsafe is in the receiver. I have a Spektrum DX6i with the AR610 6ch DSMX reciever. And according to the AR610 manual when failsafe kicks in it goes into a low throttle mode and all other channels recieve no input and are inactive. It would be nice if it would do the slow circle thing, but I guess this is better than nothing. At some point I will be switching to my FrSky Taranis x9d+, but the Spektrum is what I'm using for now. Is there a recommened FrSky reciever for planes? Or will an X4R work fine? And thank you to everybody who replied!
FrSKY gives you the choice of having the failsafe on the Rx or on the Tx.
They have many different Rx options. Stick to the X & S series.
Their new S series is the same as the X but with a gyro.
https://www.frsky-rc.com/product-category/receivers/
 
#15
I had a suspicion this was what was messing you up.

Mike, if you look in the model setup page (first page after model select) menu on the radio, there's an option to setup the failsafe toward the bottom, right after the bind.

When you're using a taranis, it's better to set it up from there. If it's not pre-set to "receiver", a manual failsafe through the bind will be overwritten, with some versions going as far as overweighting it with "not setup".

Power on both TX and Rx, pick custom and set, and from there you can then set the response and position of each channel. From there, it should stick.
Awesome! Missed that setting. Maybe I will even be able to dial in a little bit of rudder to cause a circular descent instead of a straight glide.

Thanks,

Mike