Failsafe- Throttle down but what about the control surfaces?

[Simon Wright]

I have had a couple of momentary lock outs on 35Mhz PCM but have never experienced (or at least noticed) any break in control on 2.4 and would like to get opinions from other people with experience.

I know that the minimum requirement for a failsafe is to have the throttle go to idle or even stop the motor but what is considered the right thing to do with the control surfaces.

So the first question, taking failsafe of throttle down or cut as a given is, do you set fail fix(last command) or go to presets? My JR has Smartsafe on throttle, Pre-set or Last command hold.

Following a basic bind process I have been flying with ‘Hold last command’ with throttle down which may or may not be a good thing depending on the position and orientation of the model when it goes into fail safe.

Remembering that the prime requirement is to protect people and property (not preserve the model), should the aircraft be set the to come down at minimum speed within the minimum distance.

If you go to presets what do you do?
A quick end to the flight would be Engine off, full up elevator, full rudder, full opposite aileron, flaps down, gear down, etc to create maximum drag and a low speed spin? Even this could be hazardous in certain conditions.

The alternative Preset is controls to neutral which would give an unknown, maybe recoverable outcome with no idea when or where the model will come down.

Obviously failsafe settings are only of use if the rc system is working so a battery disconnect or similar failure leaves the model as a free flighter. My petrol models use an electronic ignition kill switch that cuts the engine on loss of rc signal. So at least they turn into unpowered gliders.

Not even sure how much of a problem momentary breaks are but would appreciate reasoned opinions

[Alan Cantwell 1131]

hmm, this is deffo a grab comfy chair, grab popcorn, and watch the fur fly,

but, its an old old question, and there are many sides to the argument (for arguments there have truly been) for me, i choose to set everything to nuetral, and have the prop barely windmilling, for that is a better brake than a stopped prop, on electric, its desirable to have the prop stopped, for electric is a far better finger chopper than IC could ever be,

what worried me about 2.4, is the fail safe thing has never bothered any of the under 7kg flyers, before, yet now along comes a system, that has at least a throttle failsafe built into its recievers( i am talking spectrum here, for that is what i use, DX9, AR700 recievers) and just how many are not setting the failsafe? watch down your club fields, see just how many dont even check, isnt it a rule set in stone that any model with a failsafe fitted must be set?

[Bob Thompson1894]

Yes it is. And we do check at our club, as all should do. Also, I agree, throttle to idle, other surfaces to neutral.

[Simon Wright]

So thats two at preset to neutral??

If you use Spekky /JR do you actively set the Preset condition by programming propper or just bind with throttle down which is smartsafe and hold last command?

[Alan Cantwell 1131]

i set it all at neutral, throttle shut, and use smartsafe, this on the AR900s i dont think the AR 700 has more than a failsafe on throttle--must check next time out

[Simon Wright]

Alan, I think that unless you do the routine to put the RX into program mode it goes to smartsafe and last command on surfaces. May be worth a read up of the RX instructions though.

[Alan Cantwell 1131]

good advice, i will do this, and report back, i dont like the idea of the aircraft going on a wild ride with surfaces locked over, if the throttle is closed, it aint going anywhere but down, why set to destroy the model, when control can be regained, and the model landed safely, if a control surface is set to go hard over, and flick the model into the deck, then its hard luck if its anything other that perfectly upright,

[Bob Thompson1894]

Then why have the throttle to shut? A slow idle means you can regain control if it comes back in, otherwise you have a dead stick to contend with, as well as the model possibly being in an unfortunate position! An idling prop will also slow the model more than a dead one.

[Simon Wright]

I suppose the most important question is, do 2.4 ghz systems suffer lock outs in flight and if so are they momentary or sustained.

I fly JR Spectrum and tend to fit extra remotes where possible to ensure a strong link at all times. Can't say that I have ever gone into failsafe, certainly never noticed it.

Since the models speed, position and attitude can not be known when any failure occurs it is not possible to trim out the model for anything other than an uncontrolled crash. The throttle to idle or even stop is accepted as fact but I still wonder about what to do with control surfaces and ancillary functions.

The controls to neutral idea is great if you do get control back but could lead to disaster if control is not regained.

The dump it / Spin it in option is never going to be popular with pilots-owners and could be hazardous in itself, it could overstress an airframe due to a momentary glitch or if control is recovered give the pilot more workload wrestling to recover at an already stressfull time. If control was not regained it would almost certainly put the model down quickly, and with the least speed/ energy.

Like I said at the beginning, does anyone have experience of lock outs, momentary or sustined on 2.4?

[stuart cotgrove]

I suppose the most important question is, do 2.4 ghz systems suffer lock outs in flight and if so are they momentary or sustained.


Like I said at the beginning, does anyone have experience of lock outs, momentary or sustined on 2.4?

yes, on several occassions with, couple on an Ar500 receiver which locked out at a certain angle (flying towards me as though the engine/tank had masked the single aerial) and a couple on an AR6200 (again at a certain angle) Could reproduce it on every circuit in both situations.

The lockouts were more "holds" than lock outs and each lasted for around 2 seconds at a time..... Almost as thogh the plane flew through the angle of bad reception and then started to "listen" again.

Would benevr use AR500s again, and now make sure the satelites are distacnced from any mass of metal

[Simon Wright]

Thanks Stuart.
Momentary loss on AR500 and AR6200. Any more?

Bet it was a long 2 seconds when the plane was coming at you with no control .... got to ask. Did your throttle go to failsafe?

[Tony Collins 1073]

When I first built my Precedent Stampe { which I still have ] in 1979, I decided that too much effort had gone into it to risk losing it from interference which was more prevalent in those days then it is now.
I decided to build a failsafe for all channels just in case { this was before PCM radio and I used my home built RCM&E radio gear] I had RAF Weathersfield to fly on with my club in those days and it was just magic.
When the failsafe was complete I took the Stampe to the airfield one fine sunday afternoon and took off. After gaining reasonable height I said to our club chairman standing beside me, " I'm going to switch my transmitter off now and see if it can fly on its own. I thought that he was going to have a fit but I switched off all the same. It continued in a gentle turn with the engine on fast tickover just losing height slowly. after about 30 seconds I switched back on and resumed normal flight. No one else knew that I had switched the transmitter off.
To this day I use the same settings for failsafe and do feel that an aircraft which stays on it its last inputs can be positively dangerous in certain circumstances.
My settings are throttle fast idle, Ailerons neutral, Elevator with some up in and rudder with a reasonable amount of left [or right] . This gives most aircraft a chance to fly through any interference.
We wont even talk about wiring, battery or switch problems as these should never occur on any properly built and maintained model under any circumstances. The other interference problem which may come from RF energy feeding back to the receiver via the servo signal wire should also be a none starter for any LMA member who is serious about safety as there are some well known counter measures for this.
I personally use the schmidtt digital inverter method which not only isolates the receiver but also boosts the
servo signal level.
I am not saying that this a panacea for all aircraft. but it will give even aerobatic types a chance to stabilize and give more time to see what it is going to do.

There, I will now stand back and wait for response. Be gentle with me as I'm getting on a bit.

Tony.

[stuart cotgrove]

Thanks Stuart.
Momentary loss on AR500 and AR6200. Any more?

Bet it was a long 2 seconds when the plane was coming at you with no control .... got to ask. Did your throttle go to failsafe?

No, not in any case has that happened.... The throttle just stayed constant....

[Alan Cantwell 1131]

BOB THOMPSON, sorry pal, i said throttle closed, for me, that is tickover, sorry for the confusion,

[Simon Wright]

Is there someone in the LMA that could be considered expert in the field of rf links and fail safes? I would like to discuss a few items and would prefer not to do it on a public forum.

[Tony Collins 1073]

Simon,
I would have thought that discussion about an important subject such as this should be on an open forum as ours is so that everyone may benefit from whatever the outcome may be. Why the secrecy?

[Simon Wright]

Tony,

I have already asked questions and so far the open forum has not answered them.

Can I respectfully ask where your contribution is?

[Alan Cantwell 1131]

WELL, i have looked at your questions, and i have seen answers to all of them, there is no set in concrete way of setting the failsafe, its up to the individual, but its totally aggreed across the board, that the throttle MUST be closed, this alone will stop the model, so where do we go from here? i could bullet post your questions, and put the answers here, but i dont see the point???

what exactly are you looking for????

[Tony Collins 1073]

Tony,

I have already asked questions and so far the open forum has not answered them.

Can I respectfully ask where your contribution is?

How much in the way of an answer are you expecting Simon? Didn't you find anything of value in my reply?

Have another look and tell me again that none of your points have been covered.

When I first built my Precedent Stampe { which I still have ] in 1979, I decided that too much effort had gone into it to risk losing it from interference which was more prevalent in those days then it is now.
I decided to build a failsafe for all channels just in case { this was before PCM radio and I used my home built RCM&E radio gear] I had RAF Weathersfield to fly on with my club in those days and it was just magic.
When the failsafe was complete I took the Stampe to the airfield one fine sunday afternoon and took off. After gaining reasonable height I said to our club chairman standing beside me, " I'm going to switch my transmitter off now and see if it can fly on its own. I thought that he was going to have a fit but I switched off all the same. It continued in a gentle turn with the engine on fast tickover just losing height slowly. after about 30 seconds I switched back on and resumed normal flight. No one else knew that I had switched the transmitter off.
To this day I use the same settings for failsafe and do feel that an aircraft which stays on it its last inputs can be positively dangerous in certain circumstances.
My settings are throttle fast idle, Ailerons neutral, Elevator with some up in and rudder with a reasonable amount of left [or right] . This gives most aircraft a chance to fly through any interference.
We wont even talk about wiring, battery or switch problems as these should never occur on any properly built and maintained model under any circumstances. The other interference problem which may come from RF energy feeding back to the receiver via the servo signal wire should also be a none starter for any LMA member who is serious about safety as there are some well known counter measures for this.
I personally use the schmidtt digital inverter method which not only isolates the receiver but also boosts the
servo signal level.
I am not saying that this a panacea for all aircraft. but it will give even aerobatic types a chance to stabilize and give more time to see what it is going to do.

There, I will now stand back and wait for response. Be gentle with me as I'm getting on a bit.

Tony.

[Simon Wright]

Sorry Tony, a too prompt response. I will say though that the failure mode of 2.4 has not been discussed at all. I for one would like to know if it is normal to expect momentary loss of the radiolink with immediate reconnect in which case fail to nidle and neutral surfaces may be acceptable. I cannot see how anyone can consider a total loss of radio with failsafe to neutral to be safe. Even with dual receivers. The JMA recognises that in part with two stage failsafe- reduce to engine then kill the engine if failsafe lasts over 3 seconds. The only way to slow the model is to lose any forward velocity--- spin it in.

Dons hard hat.