Be honest, do you set the fail safe?

[Tony Smith 7]

Posted by Myron Beaumont on 28/01/2013 21:13:57:

Failsafe

Hmmm No such thing in my opinion -nothing is !.I think I have it on my gear ,but I also trust myself not to rely on a "failsafe device" when I'm capable of flying within my battery capacity limitations whether they are are electric or ic powered A/C . I do use a multimeter as one of my best accident preventative tools and has worked for me since day one .I suppose soon we.ll have a gizzmo to tell you whether the failsafe mechanism is working or not -Ad Infinitum!

I think your argument would have some merit if we were talking about some additional piece of kit.

In most cases I'm sure people are referring to a capability already in their equipment. For example on the Frsky that I use you just press the F/S button on the receiver and it memorises the current positions as the fail-safe. In fact the factory default if you don't do that is to leave servos in position and switch the ESC off which is already pretty fail-safe for electric.

Your comments about timers suggest you think people are recommending using a fail-safe instead of checking their battery life and capacity. I can't see where you're getting that from.

Using a piece of safety equipment doesn't mean you should fly less safely. For example I always flew with a parachute, but never once took a risk that I wouldn't have if I didn't have the chute.

[Geoff S]

Posted by Bob H on 09/03/2013 20:18:26:

No need when flying electric. What happens if you lose your plane for a while in the ground ? ( with the failsafe set) Your motor will keep running until the battery is flat and you would probably require a new motor after . The prop will just keep on turning digging a hole.

If any model needs a failsafe function that cuts the throttle, it's an electric one ... and that's for the sake of the operator as much as innocent bystanders. After all, I've never seen a model with an ic engine burst into life without warning (all too often they won't burst into life when you want them to) but an electric model can. A 12x6 prop powered by an electric motor is more dangerous than an ic powered one because an electric motor continues delivering torque, even when stopped, right up to the point the smoke escapes.

After all it may be your arm rather than the ground it's digging into. I always set the failsafe and, in addition, I've programmed a throttle hold switch on my Mux 3030 so that inadvertent operation of the throttle control won't start the prop spinning. I regard any electric model as potentially dangerous if there's a battery fitted.

Geoff

[Bob H]

I think you have missed the point. With Electric with your TX switched off the Prop does not turn at all WITH THE FAIL SAFE OFF. and withe the Lipo in the plane connected. Safe ??

[Chuck Plains]

Bob, you must have an unusual ESC on your model/

[Peter Beeney]

Bob, - Just as a point of interest, and I believe that different receivers have different fail-safe facilities, but if your receiver is so enabled please may I ask how do you actually inhibit this? In other words, how do you switch it off? I only wondered…

PB

[Tony Smith 7]

Posted by Bob H on 10/03/2013 14:23:34:

I think you have missed the point. With Electric with your TX switched off the Prop does not turn at all WITH THE FAIL SAFE OFF. and withe the Lipo in the plane connected. Safe ??

That depends on the receiver. Some default to sending servo centred signal, which would be 50% power on a plane. If your receiver sends nothing then with most ESCs you'd be correct, the motor would stop.

The thing is, by the time you'd checked all that out it would have been quicker to just set the fail-safe then you know where you are.

[Bob H]

Ah......... Thank you for all your replies. I have a Futaba set up. 6Ex and rx is R607FS. I thought Rx's on failsafe worked the same. Anyhow on my Futaba TX one can set the failsafe to any level/speed or switch it off altogether. Which I was advised to do when flying electric, off that is.

I am fairly new to electric, but flre I/C for over 20 years and always used Fails.afe when it was available. This I think clears it all up now. Cheers, Bob

[Erfolg]

I guess we all recognise that it is advisable to set the failsafe.

You can argue the merits of how the failsafe should ideally be set until the cows come home. Yet irrespective of the directive that the failsafe should be set when available, in itself it seems sensible to set it.

With respect some Orange (Frsky) Fasst Rx's, it advises that the Tx failsafe should be switched of, such as the 6ex. The reason is that the Tx failsafe causes a issue with that particular Rx. The instructions then go on to describe how to set the Rx failsafe.

The dangers of a motor bursting into life spontaneously are very low under most circumstances. Certainly when arming the ESC, the risk would require a malfunction of the the ESC, in all the ESC's I have purchased in the last 5 years.

However, I recently came to see that not setting the Failsafe to throttle to of, could indeed be source of a real danger. If for what ever reason the signal is lost, such as turning of the Tx, the motor could revert to the default setting, which in many cases appears to be either, last command or neutral stick positions. If not set to of, the motor will start or continue to run. In either instance, this does not seem advisable.

I have inadvertently very recently had occasion to deal with stalled motors. In one case where the owner of the model stood frozen to the spot, when the propeller was trying to thrash itself to pieces. The other instances, was my own model, which had a control issue, again, the motors stalled (twin). In neither case was the ground thrashed into a big hole, nor is the stalled torque, life threatening. Now these were lowish powered motors, less than 250w. Rather than a killing machine, the action in itself is pathetic, putting the ESC, wiring and Lipo integrity at risk. With no revs, the torque is pathetically low, without revs.

Now I am not saying that electric models and motors do not have issues with respect to safety. Yet I have seen far more real injuries, some very serious, from IC propellers than electric motors. It could be the nature of how IC motors are started, and tuned compared to electric, or maybe the relative recent arrival of brushless motors, that is the issue. It is propellers free to turn that are the danger.

[Bob H]

Well........ after reading all this....one makes one's mind up. I know what I shall be doing. Bi Bob

[Olly P]

Posted by Bob H on 09/03/2013 20:18:26:

No need when flying electric. What happens if you lose your plane for a while in the ground ? ( with the failsafe set) Your motor will keep running until the battery is flat and you would probably require a new motor after . The prop will just keep on turning digging a hole.

Great - apart from for the person who it hit on the way down, and the LEGAL REQUIREMENT to set them.

If you set the failsafe to turn the motor off this does 3 things - 1) if you loose connection you know about it and understand why the aircraft is not doing as it is told, 2) the throttle is shut, so the aircraft doesn't just keep going until the battery is dead, 3) it doesn't come in spinning and damage anyone!

Olly

[Erfolg]

Olly

The CAP 658 actually says this

• A serviceable 'fail-safe' mechanism should be incorporated to operate on loss
of signal or detection of an interfering signal.

We including the BMFA need to stop turning strong advisory note into a compulsion. This practise undermines the position of modellers. There may be circumstances where it is possible to argue that not setting the failsafe has some merit. For the life of me I do not know how, yet we should not cut the ground from under modellers.

I strongly recommend the use of a failsafe, non the less.

There is a similar situation with respect to Rx's, with respect the BMFA. There is no legal requirement at present that a Tx must have a CE marking. It is not illegal to use one without the mark. It is however illegal to use either a Tx or Rx that is not compliant with regulations, marked or not marked. Yet i have seen communications purporting to come from the BMFA which states the CE mark is a legal requirement for use.

Authority tends to take a position that is cautionary from their perspective. For use modellers, to be advocating even more proscriptive interpretation, will naturally be greeted by authority with pleasure and be welcomed.

I repeat that I do advocate the use of failsafe with models where available. With electric models, I believe it should be set to low throttle. As this provides in my opinion, the greatest level of safety. Both when being handled and in the air.

[Olly P]

Sorry, my mistake.

I think the remainder of the post still stands however....

[Peter Beeney]

Would it help to try and define a few of the issues here? This is how I would consider it; but it’s only my version of events, it might not be exactly how it works now.

For starters, I couldn’t really call it a ‘fail safe’ system, rather more a ‘servos to pre-set position’ system.

But under some conditions, in my opinion the electric system is safer than the i/c. Let us assume the fail safe is not going to prevent the model from crashing by simply closing the throttle, but it will prevent it from flying away. This would be in the event of a straightforward loss of signal. Also this is the detail the CAA might be interested in; I suspect they might think that a runaway model getting up in the air lanes amongst the full size might not be quite an ideal situation.

In the event of an i/c model losing signal, if the fail safe is operating correctly the throttle servo will close the throttle and the model will soon land one way or the other. If however, it is operating incorrectly, i.e. back to front, maybe, the throttle servo could well open the throttle wide, and then hold it open, the model could then fly to wherever it will. If the model is electric, very much the same thing will happen, except that’s it the full throttle signal now controlling the ESC, which in turn will then supply the full battery voltage to the motor.

In the event there is a total power failure, and this is something that can and does happen, the i/c model’s throttle servo simply stays where it is, and if this should be at three quarter or wide open throttle say, then the model can again fly wherever it will. This is one of the reasons why it’s it’s definitely not a fail safe system. Also it would be difficult for the CAA to place a statutory requirement on the use of a fail safe in the event of a signal loss, but nothing at all in the event of a power loss? And in my very lowly opinion, I think this is by far the greater risk anyway, although it might still be a low risk overall.

However, regarding an electric model, if there is a power failure, the BEC going down say, this is primarily a 5 volt supply to some components on the ESC and so the ESC will very quickly shut down and the motor will will definitely stop. If there is a separate UBEC or battery, if this also fails the receiver cannot function, and thus the ESC will not receive a throttle signal and the motor again will not run. So unlike an i/c powered model at least if the electric version suffers a power failure of any nature the motor will stop and it won’t fly away.

If it’s not possible to turn off the receiver’s fail safe facility, and and I’m not entirely convinced that it is on all receivers, but I could be wrong wrong about that, I’ve not studied this very much at all, then in the event of a signal loss condition the receiver is always going to send a signal of some sort to the ESC; or, at least, that’s how it used to work; and if it’s the wrong one the the motor might do exactly the opposite to what you want it to. Another good reason for it not being a genuine fail safe condition. A third good reason, and very important in my estimation, is that the operator should not be in a situation to be able to actually tinker with the settings at will in any case.

I’m of the opinion that if an electric motor inadvertently starts to run on the ground, unexpectedly, then it’s because the throttle has been accidentally or otherwise opened. It’s difficult to think otherwise. The ESC will only respond to a true throttle signal pulse from the microprocessor within the receiver, and the microprocessor can only send it if it receives if from the radio frequency section; and the microprocessor won’t sent any corrupt signals, it’s either a good signal or no signal. Like Geoff Sleath, I’ve always switched the throttle control on and off on my MPX, from years ago, I called mine Throttle Lock, and it’s always worked for me. In any case I wouldn’t normally be going anywhere near the prop with my hands unless I was specifically going to do something to it, and in which case the battery would definitely not be in the model.

[Peter Beeney]

PART TWO

So overall I’d certainly agree with Bob H, in as much that as for electric models if you switch the failsafe off the system is always going to automatically default to the situation where the motor will stop. Without any input from the operator. But if the failsafe is switched on, then in the event of a signal loss, if the failsafe is incorrectly programed then the receiver could continue to send the full throttle signal to the ESC. And from reading all the various words written about failsafes over the years I’d consider there might be a better than 50% chance that it is actually incorrectly programed. So this, in my book anyway, this is probably the most satisfactory state of affairs.

One caveat to consider is that the larger model approach is different, therefore this may perhaps need to be looked separately, and a second one is that I’ve personally not done any practical checks on any 2.4 failsafe mechanisms. But I happen to have some Spektrum receivers at the moment plus my 5e tx, so I shall have a dabble tomorrow and discovery precisely what occurs when the failsafe operates. I did notice once before when I was just experimenting with a Spektrum 2.4 system that it’s wise to check the operation regularly, if you inadvertently re-bind at some point it’s easy to get a cross over and so the throttle’s pre-set function is not then set correctly.

As always, just my personal point of view, and should not be taken to be any form of actual circumstances.

PB

[Jon Laughton]

yes always

[Bob H]

Thank you Peter. Bob H

[john stones 1 - Moderator]

I fly i.c. answer is always. throttle to tick over, it hopefully would bring my model down within field, no guarantees in life, but if you've got it, use it.

battery could fail etc is irrelevant. its simple to set up, use it

[Iain Hale]

Could some help me out on setting up the failsafe for my powered glider. Using a DX 9 Tx the config for powered sailplane puts the throttle onto a switch to allow progressive crow braking via the throttle stick.

On the Rx (AR7010) the left aileron is plugged into the throttle channel and the motor into Aux 2. With the motor running, and turning off the TX, the only that happens is the left aileron returns to neutral.

Despite re binding the RX with everything in neutral motor off if full crow braking is applied only the LH aileron would return to neutral on loss of signal and or if the motor was blipped at the wrong moment to extend the approach on landing, well I leave the rest to your imagination.

In summary: I thing the TX manufacturers could provide clear guidance for all types of configuration on fail safe settings I see very little useful information in the DX manuals. And I can't fly this model until this situation is resolved.

I need specific help on my topic if anyone out there can assist. And given the the legal requirements could there be some published guidance to help and inform all of us.

If we value the reputation of our hobby a crashed model causing mayhem would certainly make the papers for all the wrong reasons.

[Pete B]

Are you using the 'Pre-set Failsafe' option available on the AR7010, Iain? If you're using the basic 'Hold Last Command' failsafe, only the throttle channel will go to the low position.

From the AR7010 user manual:

Preset Failsafe
If the signal is lost, all channels are driven to their failsafe position set during
binding. Preset Failsafe is ideal for sailplanes, as spoliers can be deployed during
loss of signal, preventing a flyaway.
How To Program
1. Insert the bind plug and power on the receiver.
2. When the receiver LEDs blink, indicating bind mode, remove bind plug before
binding the transmitter to the receiver.
3. LED lights will continue to blink.
4. Move transmitter’s control sticks and switches to the desired Preset Failsafe
positions, then turn it on in bind mode.
5. The system should connect in less than 15 seconds.

That should set all channels to where you want them - often a 'Crow' setup on a sailplane.

Pete

[Iain Hale]

Pete

Very many thanks for this enlightening piece of information. Will get to this tomorrow morning. Perhaps a feature article in RCM&E would help the wider modelling community to better understand the intricacies of failsafe setting?

[gangster]

Yes I set it and also check it as part of my first flight of the day routine with the range check

However is that good behaviour with 2.4 ghz radio Is it bad practice to turn the tx on and off once bound.? I seem to get away with it on both my Futaba and Spektrum but maybe should not do it.

incidentally earlier in the week a fellow flyer was checking out his model prior to the maiden flight and was surprised to find his was going to full throttle on fail safe where he was sure it had been right at home. Much banter and leg pulling later I went over to my own model which was ready for the first flight in 15 yrs. Lo and behold mine was reversed and I swear it was right at home. So it's worth checking

totally different radio his was speky with Orange receiver and mine was JR with a Stone Age zpcm rxI

I think is so possible to touch and change something on the set up inadvertently when changing some other setting

advert for pre flight checks methinks.

[Dave Hopkin]

Posted by gangster on 15/05/2015 09:35:41:

However is that good behaviour with 2.4 ghz radio Is it bad practice to turn the tx on and off once bound.? I seem to get away with it on both my Futaba and Spektrum but maybe should not do it.

advert for pre flight checks methinks.

Is there a way to test failsafe without switching off the TX? I suppose you could do it in range test mode but I believe that Spekys (no knowledge of Futaba) retain the GUID of the RX once bound so it shouldnt make a differerence - as long as the model is restrained of course!!!!

Edited By Pete B - Moderator on 15/05/2015 11:08:24

[The Wright Stuff]

Posted by Dave Hopkin on 15/05/2015 10:04:23:

 

Is there a way to test failsafe without switching off the TX? I suppose you could do it in range test mode but I believe that Spekys (no knowledge of Futaba) retain the GUID of the RX once bound so it shouldnt make a differerence - as long as the model is restrained of course!!!!

Dave, all I can say is that I have done it repeatedly with Futaba (or at least with S-FHSS) and never encountered any problems.

I don't think you can thoroughly test failsafe properly in any other way. If you want to know what happens when you lose signal, you have to lose the signal!

Edited By Pete B - Moderator on 15/05/2015 11:08:51

[Pete B]

There you go, tidied up to minimise the and I quite agree, Dave - the GUID is retained once bound

Pete

[Dave Hopkin]

Posted by Pete B - Moderator on 15/05/2015 11:12:34:

There you go, tidied up to minimise the and I quite agree, Dave - the GUID is retained once bound

Pete

For once my blushes spared!!!!

Ta Muchly