Fail safe settings for full-house glider

[Tim Crow]

I fly thermal and generally push upwind until I get RSSI warnings. I want to set a fail-safe for gentle flat 360s in case I lose range, and then the breeze will bring it back closer. Any slight rudder causes it to wind into tighter turns so I wondered if anyone had any suggestions? A smidge of aileron would probably work, but up or down? I wonder if down would be better as any speed increase would cause extra drag and maybe help flatten the turn.

[Paul De Tourtoulon]

What radio and rx are you using, I get miles away and none of those problems for me,,,?

[Frank Skilbeck]

Problem with putting any control input in is that the control will continue, so you'd probably need to tune it for a flat turn, i.e. rudder and some opposite aileron, but that only works if it keeps flat, any thermal activity raising a wing would need to be compensated for! and if it does hit a thermal then away it will go. a club mate built a small free flight chuck glider, it caught a thermal and last we saw of it was two fields away still going up.

 

But if you get so far away that you lose radio contact then either you have hawkeyes or there is something wrong with the radio installation, I've seen guys flying 6m scale gliders to the limit of their eyesite with no radio link issues.

 

BTW the law is that failsafe settings should be to cause the model to descend, so by law it should deploy any airbrakes or put the model in a spin https://bmfa.org/Info/Why-join-the-BMFA/Failsafes

 

 

[Tim Crow]

Interesting replies, thanks. I'm flying a new Heron and haven't got to the limit of radio range yet - Radiomaster TX12 and FrSky GRX8 receiver. When it was in my Easyglider it was a bit more cramped so the rx aerials were not ideally positioned, but the Heron has more room and that has obviously made a difference as RSSI seems better. It hasn't really been the weather to fly it to the limit but spring isn't far away.

[Cuban8]

Not too sure that putting a glider into a spin via failsafe settings is a good idea. As it's being left to the model with no correcting input from the pilot, the chance of the model going into a high speed spiral and then suffering a break-up and potentially becoming an even greater hazard is a possibility.

Yes, the law wants fail safes to bring a model down and not fly away up to altitude where a risk to full size aviation might occur. I'd be inclined to set gliders to airbrakes out and trim other controls to a slow turning descent to keep the model within the area. If the model's up wind then radio contact might be regained as the model drifts back and descends towards the transmitter.

I think it's usually accepted that models will be under solid control at a range of around a mile when in the air - that's a long way away and getting towards the limit or even exceeding normal vision in good conditions. Down to the pilot to determine what is safe and lawful.

Edited January 23, 2022 by Cuban8

[Stuart Z]

Hi

Only just getting in to gliders - would a gentle stall work.  (Small up elevator?) I can’t see a turn working out that well.  From full size flying they seem to need balancing out all the time to stop tightening up.  Stall would also be a risk but is this not the point where 3rd party safety overrides?

 

 

[Gary Binnie]

From the BMFA handbook:

 

14.16  Large Gliders – Slope and Thermal

 

(a)  Considering that the purpose of the fail-safe device fitted is to avoid a flyaway, it is recommended that it should be set with that in mind. Activation of spoilers, crow brakes or even the elevator to full up and the rudder to full left (or right) would be appropriate.

 

I have used this setting for over 15 years for F3J/F5J gliders. Full up elevator ensures that a high speed spiral dive can't happen. I use half crow brake with the trailing edge of the flaps inline with the bottom of the fuselage so that if the model does descend in a flat spin all the way to the ground the flap and servo damage would be less than full brake.

 

F5J gliders have been lost upwards to monster thermals, activating the failsafe by switching the transmitter off might get your model back but if it doesn't it should be in a safer descent mode (thinking of where it might land), it's possible that a lost glider would still have a good radio link.

 

Carbon structure can cause reception problems and it is very important that the receiver aerials are placed correctly (usually outside the fuselage) and thoroughly tested during initial flights. I used to use a mixture of JR/Spektrum DSM 2 which used the flight log box to record frame losses and holds, there is a procedure for ground range checking with it. I use Jeti Duplex now which has dual path live signal strength displayed and announced on selecting a momentary switch, the first sign of signal loss is the loss of telemetry packets which gives time to fly back closer then land and rearrange the aerials, I've only had this happen once.

 

  Cheers

 

        Gary

[Cuban8]

When I dabbled with BARCS open glider comps back in the 80s, it wasn't unknown for a large thermal soarer to get away from its pilot either because of radio problems or flying the wrong model at altitude. Models did get wrecked, but on quite a few occasions, an errant  model would drop into sink and circle its way down to the ground and land with very little damage in the next field, or after being followed a mile or two and then recovered. Whether a model was totalled or not was down to a bit of luck of course, but a better chance was stood by a model that was well sorted and trimmed to circle on its own in lift, or in the case of a problem, eventually back to terra firma.

Something the freeflight boys know all about of course.

[MattyB]

17 hours ago, Tim Crow said:

Interesting replies, thanks. I'm flying a new Heron and haven't got to the limit of radio range yet - Radiomaster TX12 and FrSky GRX8 receiver. When it was in my Easyglider it was a bit more cramped so the rx aerials were not ideally positioned, but the Heron has more room and that has obviously made a difference as RSSI seems better. It hasn't really been the weather to fly it to the limit but spring isn't far away.

Be careful with the GRX8 - some had manufacturing issues where the wrong components were soldered on the board, they worked but had reduced range and lost telemetry at regular intervals. If yours is one affected and you bought it from T9 (or any reputable Frsky dealer) they should still replace it…

 

https://www.rcgroups.com/forums/showpost.php?p=44871377&postcount=3610

 

PS - The above aside, don’t waste your time searching for the perfect fail safe position, there is no such thing. Just set a tiny amount of rudder in so it changes direction; yes it could spiral, but at least that way you have a chance of the signal coming back as the angle changes. Ultimately you are far better investing your time into optimising the RX and aerial install for best range than you are trying to workout an optimised FH glider fail safe position.

Edited January 24, 2022 by MattyB

[Tim Crow]

13 hours ago, MattyB said:

Be careful with the GRX8 - some had manufacturing issues where the wrong components were soldered on the board, they worked but had reduced range and lost telemetry at regular intervals. If yours is one affected and you bought it from T9 (or any reputable Frsky dealer) they should still replace it…

 

https://www.rcgroups.com/forums/showpost.php?p=44871377&postcount=3610

 

PS - The above aside, don’t waste your time searching for the perfect fail safe position, there is no such thing. Just set a tiny amount of rudder in so it changes direction; yes it could spiral, but at least that way you have a chance of the signal coming back as the angle changes. Ultimately you are far better investing your time into optimising the RX and aerial install for best range than you are trying to workout an optimised FH glider fail safe position.

Thanks for that link. I haven't had any problems with telemetry and signal RSSI seems good in the Heron ATM with the rx aerials as situated. I'm loathe to dig out the rx again to check as it's tucked well away - maybe if I get bored. I'll see how many RSSI warnings I get once the thermals get better and I push further. 

[MattyB]

Just now, Tim Crow said:

Thanks for that link. I haven't had any problems with telemetry and signal RSSI seems good in the Heron ATM with the rx aerials as situated. I'm loathe to dig out the rx again to check as it's tucked well away - maybe if I get bored. I'll see how many RSSI warnings I get once the thermals get better and I push further. 

 

How old is the receiver? The two I had that were affected are probably ~3 years old, so if it's younger than~2 I think you should be ok. Certainly if you aren't getting telemetry alarms at pretty short range I think you should be ok (mine were going off at anything above ~100m, though the RF link itself never missed a beat).

[Engine Doctor]

Just a though but have you thought about setting rudder with opposite aileron for a flat turn then using a gyro to keep it  in a flat turn with gentle decent ? All settings including gyro obviously only switch/activate when in failsafe so should it wont affect your normal flying .

We have a member who regularly fits gyros or GPS systems so that should he loose control it returns to take off area and gently decends.