Nasty incident

[GrahamC]

Posted by Martin Phillips on 19/07/2013 10:29:27:

Posted by Peter Beeney on 18/07/2013 22:49:13:

In my view safety is to some extent self discipline, and so adopting a procedure that appears to be be safe and then adhering to it I would think is sensible idea, it’s what I do. It soon becomes easy, like wearing the seat belt, or taking the handbrake off. I know that these can be missed, too, but not very often; and hopefully when that other ‘situation’ is not lurking close by to cause a major mishap, either. If you consider that an electric model can start without warning and treat it accordingly then you shouldn’t go far wrong. Probably 99% of models are never going to start under these circumstances, but just the 1% could be a personal disaster.

I will repeat again, if you fit a safety plug correctly wired in to electric models then the model simply cannot start without warning even with a battery connected. I take my plane onto the flying field, switch on the transmitter, stand astride the model behind the wings, insert the safety plug with the transmitter on the ground, stand back and then go through the pre-flight checks.

On landing, I remove the safety plug in the same manner and carry the model, now completely safe off the flying field.

All my models have a safety plug, and once that is inserted, it sends a clear mental message that the plane is armed.

Absolutely agree that this makes things a lot safer... but it doesn't resolve all the issues of having an incorrectly set failsafe. If your TX fails while the model is in flight and the failafe is incorrectly set the best outcome is that the model swiftly connects with terra firma and nothing else!

[Erfolg]

It does seem that many of the incidents seem to involve mixed discipline users/clubs. I am now starting to wonder if in some way this lies behind the apparently numerous incidents. As I can say hand on heart, that at the all electric club, I cannot remember one incident at all, of the types described.

What incidents there has been, have been at odds in the consequences, that many describe will happen.

At our club, there is one fundamental rule that does not seem prevalent with mixed usage, that is the model is not armed until its immediate use. If there is a delay, the model is powered down again. On landing, the model is immediately powered down.

This approach appears to be at odds with typical and appropriate to IC thinking. Where the model is powered up, then a whole sequence of events take place from, connecting glo starters arranging the field box to use a starter in some instances. Quite lengthy process, where little risk and hazard occur until the engine starts, when a step change in danger happens. With electric, unmanaged delays, are a recipe to straying minds, with the model live.

I do think that there are sufficient differences between electric and IC model flight preparation, that some consideration and operating procedures should be considered. Rather than using IC procedures as the start, and then changing IC to electric.

Another factor which may benefit from consideration, is that typical operation of electric models on the same site, covers a massive range in size and type of models. From indoor, to 3m gliders, with other extremes of high powered scale and the more frequent sub 200w hand launched model. One of my club manages this by operating two flying areas, and a managed take of and landing to control interactions near to the ground. Yet it is in appearance Laissez Faire. Certainly our chairman keeps things light.

[Martin Harris - Moderator]

We have a simple rule at our club which means that any electric model with its flight battery connected should be regarded in exactly the same way as an i.c. engined model with its engine being started or running.

[Roy Mundy]

I always treat electric models like a loaded gun, Unlike IC which you know are on. I have had 2 frightening experiences with electric planes my first one was 2 years ago at Christmas when the parkzone spitfire Mk IX was launched and I was really pleased and excited to get it out of the box and running. Luckily My little boy was in bed and nowhere near it, as I had fitted the battery and was attempting to bind it with my Trusty Futaba FF8 (with Frsky module) and an Frsky RX ....................not knowing about the throttle needing to be reversed the plane without its wings which was across my lap leaped into action almost cutting me to shreads. Luckily I escaped without any marks and Thankfully my Children were not around. My 2nd incodence was when I was showing my neighbour my hanger with all my lovely planes in and I put in a battery to the spitfire and showed him the electric retracts working ................................Then hanging back up the model from the ceiling I forgot to disconnect the battery leaving it live! I then changed model memory to an IC plane and the spitfire burst into life whilst hanging from its bungee chords. I quicly managed to put it into full throttle therefore shutting the throttle off just intime as it almost came crashing down. Again this scared the life out of me, and after that I bought a spektrum DX6i for my electric models due to the model match and throttle reversing. I keep the futaba for IC only and I treat my growing fleet of electric models with the utter most respect and have been ok since.

[Peter Beeney]

Yes indeed, Martin, I quite agree; this is exactly what I’m saying, adopt your procedure that appears to be safe. In the same way, I’m fairly convinced that my model won’t start and run if the battery is not connected in the first instance, too. I’m quite sure that you would operate the safety plug procedure every time, and would never have a mishap, but another mortal might not be quite so thorough, and it only takes one one slight digression, a moment’s distraction, say, and there could be a deviation from the normal. Perhaps only just that ‘once-in-a-lifetime' occurrence, even. Now it’s possible there is an armed model lounging around and no one knows it! It may well go unnoticed but if someone did move a throttle stick for whatever reason the result could be unexpected, to say the least!

So in short what I’m actually trying to say is I’d consider that something like the safety plug plug system is perfect for 99.9% of the time. On the 0.1% occasion that the plug is accidentally left connected or disconnected as the case maybe, and when it shouldn’t be, then that is truly an accident waiting to happen. I’d be happy that my model would be in the restraint, and whilst that’s perhaps not an absolute guarantee that no one is not going to get hurt, at least the model won’t be zooming around the place out of control. I’m sure that’s what ‘proper’ failsafe is all about really, making sure the system is safe during any malfunction. I have to say, although I’ve seen a couple of models start unexpectedly and not in a restraint, although no harm done, fortunately, I’ve never seen one start unexpectedly in a restraint… These little ‘accidents‘ probably don’t happen very often, but it’s difficult to tell…

I did a little experiment once. Without checking anything, I ran a few electric models and then switched the tx off, just to see what happened. Without exception, all the motors stopped. So then I persuaded a few fellow modellers to do the same thing; under controlled conditions, of course; I got the same result. I was just beginning to believe the system was reasonably foolproof, but after PB’s and my own experiences recently I’m almost beginning to change my mind. I definitely think there is a good case for investigating this, and if I can replicate it I’m sure it might be possible to discover the reason for it happening. In my case, I remain yet to be convinced it was some sort of failsafe setting reversal, that the failsafe was set with an open throttle.

Safe Flying!

PB

[Andy48]

Peter, I'm pretty sure I've had the same problem when setting up too, though I cannot remember how. My Spektrum has the throttle set the right way round for the ESC, but there is a fairly complicated sequence for setting up, and I ended up with the failsafe set on full motor. However, as there was no prop on and I was actually checking to see if the failsafe was set correctly, it was easily corrected.

I do notice how few flyers really understand electric, and certainly never set up their ESC correctly for the model. Most clubs seem to have a wealth of experience about ic gained by many years of usage. However, in depth knowledge or understanding of electric is far less. In Erfolg's all electric club, I suspect things are different, with a far better general understanding of electric.

A few months ago there was a storm of protest when I said that electric could be made safer (note the "could be" than ic, though obviously as you point out it can never be totally safe. One irate respondant, a long term instructor said he found electric less than satisfactory, and had a bad experience of a trainer cutting out completely in the air. I asked him if the ESC had been set correctly.The response was all to typical. He did not know about programming the ESC, and had not checked that the learner has set anything up. I bet that same instructor would have gone over an ic installation with a fine-tooth comb before flying the model.

There's a fairly comprehensive sequence for setting up an electric plane in July's RCME, which covers setting up and checking the failsafe.

[Peter Christy]

PB: Assuming you bound the Tx with the throttle shut (as you pretty much have to) AND had the fail-safe set (not familiar with your tranny), did you subsequently reverse the throttle?

This might well of had the effect of making the "fail-safe" position full throttle instead of idle!

On 2.4 sets, its always worth rebinding (or re-setting the failsafe) once the initial set-up of the model is complete!

--

Pete

[PB]

"I do notice how few flyers really understand electric, and certainly never set up their ESC correctly for the model. Most clubs seem to have a wealth of experience about ic gained by many years of usage. However, in depth knowledge or understanding of electric is far less."

How true Martin. The advent of Lithium batteries has brought a whole new tranche of people into RC model flying, including me. I have had a lingering interest in model flying for many years and did a bit of control line 40 or so years ago, but I was never enthusiastic about IC. Now, in my late 60s, I find I can come into the hobby on terms that I understand because I'm a retired electronics engineer familiar with the building blocks of EP model flight. Indeed it was back in the early 1970s that I first struggled with the torque and slip mathematics of electroncially commutated motors as they were called back then. So the power train of an EP model is no stranger to me either in theory or practice.

I have been pretty surprised at the lack of knowledge of EP fligh amongst exclusively IC flyers in my own club, and the lack of knowledge of IC flight by exclusively EP flyers in the club. More alarming still are the misunderstandings, myths and misconceptions bandied about the flying field with regard to EP flight from both IC and EP flyers. I noted with interest recently that a club member who took his A test with an IC model was asked no safety questions about EP flight, and another club member who took his A test on an EP model was asked no safety questions on IC flight.

Is there a case growing for an EP A test and an IC A test which restricts the candidate to that type of flight only.... ......or is that another thread?

Edited By PB on 19/07/2013 17:23:51

[Pete B]

Posted by PB on 19/07/2013 17:23:12:

Is there a case growing for an EP A test and an IC A test which restricts the candidate to that type of flight only.... ......or is that another thread?

Definitely worthy of discussion in another thread, PB - I'll draw up a chair and grab a bag of popcorn.....

Pete

[WolstonFlyer]

I have wondered about that, there is the test for Silent Flight - electric, so why not a certificate just for EP flight with different questions....but then why not another certificate for EP- small models under 1kg.... where would it all end?

If somebody decides to start a thread I will happily look in on it

[Andy48]

Posted by Peter Christy on 19/07/2013 16:21:38:

PB: Assuming you bound the Tx with the throttle shut (as you pretty much have to) AND had the fail-safe set (not familiar with your tranny), did you subsequently reverse the throttle?

This might well of had the effect of making the "fail-safe" position full throttle instead of idle!

On 2.4 sets, its always worth rebinding (or re-setting the failsafe) once the initial set-up of the model is complete!

--

Pete

I have a DX8, and no I did not reverse the throttle. Yes I always check the failsafe as one of the final setting up checks.

[Andy48]

Posted by WolstonFlyer on 19/07/2013 17:58:06:
I have wondered about that, there is the test for Silent Flight - electric, so why not a certificate just for EP flight with different questions....but then why not another certificate for EP- small models under 1kg.... where would it all end?

If somebody decides to start a thread I will happily look in on it

... and another test for quadcopters.

[Erfolg]

One of my major beefs and frustrations, are comments run along the lines, we treat all electric models .......... as a IC etc.

Electric models are not IC models. The idea that the operation of an electric model should be forced into the operating mould of an IC, has to be in my mind fundamentally wrong. Just as motor bike is similar to car, but different is the same with IC and electric planes.

There is no need to arm a electric model and leave it lying about on the flightline, so why do it as part of the operating process. Both need operating processes and procedures which are appropriate to each type.

Just like PB I have tried various conditions to generate an issue and have been unsuccessful, which was a success, erm, whats, that then. The trouble is I have limited resources and access to the wide spectrum of products about. So in reality, my tests, checks, are very limited. Some claims I know to be untrue having witnessed many stalled motors etc. So separating fact from fiction can also be difficult. Though I do wonder how some things can possibly happen. It is this, which caused me to think, that something useful that the BMFA could do, is identify desirable criteria for equipment selection, and possibly setting, Having two Parkzone models, neither of which burst into life, if connected up/loss of signal, it seems that maybe some undesirable features have been designed out by the manufacturers.

Yet in my mind, electric power has differences from IC and should not be just made to conform to IC modellers of safe operation, nor the other way round. The procedures, need to be specific to power source etc.

Edited By Erfolg on 19/07/2013 18:57:23

[Rich too]

As others have said always test the failsafe first (prop removed!) Rich

[Erfolg]

Dickster

I do not think it is desirable for electric models to test an electric model with the propeller of from what has been written, when  full current is supplied without a load.

As with most tests, if you arrange the test area with both operation then safety in mind. The issue of the problem is no greater than standing on the fliteline, opening the throttle to take off.

In my case I consider what do I do if the motor does not shut down, when the Tx is switched off. I turn the Tx back on, to regain throttle control.  Shut down the model system/disarm and then investigate why, it did not do what I expected.

My biggest concern is with respect, what would I do if the motor stayed at the set power setting after switching the Tx back on, and the Rx did not respond. Again I set the throttle to half power with the view, if the motor cannot be shut down, I will need to disconnect the Lipo, although I have thought about disconnecting the ESC to Rx, but never tried it. This scenario has never occurred though, I do not like the idea of disconnecting a Lipo on load.

Edited By Erfolg on 20/07/2013 17:50:11

Edited By Erfolg on 20/07/2013 17:52:59

[Biggles' Elder Brother - Moderator]

I am sad to say that what this thread most consistantly tells me is that far too many people seem to have very little idea of how to correctly set, and why you should set, a failsafe. Truely scary!

Many of the incidents described simply should never have happened - and would not have happened if the failsafe had been set correctly.I am left completely flabergasted at the revelation that one conributor's solution to his lack of understanding of his own transmitter's failsafe system is to buy another brand! But what if he doesn't understand that as well?!

I think this would be an appropriate topic for a couple of articles - one for Futaba and one for Specktrum. They might actually save some of our fellow modellers from loosing a few fingers! Any volunteers? While I could do the Futaba one I could not do the Speckky one

BEB

[Chris Bott - Moderator]

Erfolg first of all I can't see any problem with running a brushless motor with no prop. That is far safer than doing anything with the prop on. The motor will run up to an RPM equal to applied volts times Kv and that's all. Quite a small current will be drawn too.

As for pulling the LiPo connection as a means of disabling a runaway model that still has a prop on, I'd be doing that as soon as I possibly could.

[Chris Bott - Moderator]

Pete and I will do the Spektrum failsafe instructions BEB, unless anyone else wants to beat us to it?

[Erfolg]

Chris it is from recommendations which I have read, that you should not run your motor at full power without a load. Like most things of this type, I am not certain but suspect it was on a manufacturers site. Of course what I have read could easily be wrong.

[Chris Bott - Moderator]

I wonder if that applies to particularly high revving motors, maybe EDF ones? that need the load, to keep them below an rpm where they would rip themselves apart?

[Biggles' Elder Brother - Moderator]

Posted by Chris Bott - Moderator on 20/07/2013 18:07:18:

Pete and I will do the Spektrum failsafe instructions BEB, unless anyone else wants to beat us to it?

That's fine with me Chris. We'll knock them together over the next couple weeks - vacations allowing!

BEB

[Roy Mundy]

Good idea BEB, I have my failsafe set on all my electric models and do not regret having 2 TX for me it has made everything easier . The spektrum has model match and acts as a double failsafe. The Futaba ff8 I find a very complicated TX to set up and it's not very user friendly. And after speaking to many people they all say that you have to reverse the trottle with futaba on electric ( which I should have done) but I guess as you say it's lack of knowledge. There certainly isn't anything written on any manuals that I have read. That's why I use this forum to learn from you all. The incident of the plane in the hanger would still have happened, as I was off guard and not having model match on the Futaba, this wouldn't have happened on my speccy. So even with all fail safes set you still need to be vigilant and keep safe as a sharp wiggle on the stick could cost you your fingers if your not paying attention. I think the failsafe procedure is a great thing to post also there are many people who don't do this with ic, which again is madness.

[Erfolg]

I cannot find the motor manufacturers recommendation, although I can find a few references as to why not run a brushless motor with no load.

• No high performance motor should ever be free run for more than a few seconds at a time. The motor will draw a minimal amount of current once threshold voltage is reached. This power is not being dissipated through the shaft via mechanical work so it has to be dissipated in heat through the case of the motor. The net result is that the motor will become over heated in a short amount of time.Yes, Kv is the rpm/volt of the motor. It and Kt , the torque constant (in*oz/amp), are related through the constant 1355. If you know one you can determine the other mathematically. Kv*Kt=1355In a brushless motor, there is really no reasonable upper limit to rpm. The only things limiting it would be from the centrifugal force on the rotor wanting to throw it apart or the bearings. If the motor is well balanced and solidly constructed, it should be capable of very high rpm's.It is always best to setup an electric motor system so that most of the time the motor is at full throttle. This is due to the inefficiencies of the speed controls when opperated at part throttle loads. But, the motor also has a happy current it wants to run at. When setting up a new system, you should always endevor to keep the motor loading close to the maximum efficiency point on it's load line.Check the Aveox site for some good info. Also Astro Bob's motor handbook is a good source of info. Most of it is about brush motors, but the info is pretty universal.

Then there is a long discourse of why there is no problem, when the suddenly the doubter becomes a convert after a lot of figures.

• Lets take a real world example I happen to have on hand - a Mega 22/45/3 is a largish motor.Io = .95 A
  Rm = .088At no load current levels its producing .95*.95*.088ohms = .079 watts of resistive copper heat losses. Close enough to zero. Most any largish motor will have almost zero resistive losses at no load currents.Iron losses are a lot more depending on voltage applied and Io.Lets be arbitrary and say we use a 3S pack full power at 12 volts so 12*.95 = 11.4 watts.11.4 watts will produce some real heat, but not enough to hurt that size of motor. Take a 6S pack and run it at full voltage and you have 23 watts or so. Now, with 23 watts you will have some real heat if you have no cooling air flow.A Hi Kv motor with a really hi Io could get pretty hot when run at full voltage on the bench even with no load.Kep the voltage down and you will be fine.So I guess it depends on the motors Io and how much voltage is applied and how big the motor is.I stand corrected I was mostly jumping on you about the brushless motors "running away" under no load thing and I got carried away
•  

Once spending some of youth testing electric motors and alternators, all done with load, where the items were either in a steel box or concrete pit. I tend to think the electrical engineers knew and know more than me.

On that basis I will still stand to be corrected, as I am relying on others knowledge not my own.

On the other hand it is just to easy to test with real conditions, as would happen in real life and any meaningful test at the field and do it safely. For some there is a mantra, take the propeller off, no real logic.

Sometimes safety is a problem, just as the reprot today in the newspaper, where paramedics stood by as a man drowned. A policeman came, went to the rescue immediately. The Coroner apparently was not best pleased, although the H&S people still maintain the right thing was done or not done.

Edited By Erfolg on 20/07/2013 20:23:51

Edited By Erfolg on 20/07/2013 20:25:17

[Erfolg]

The problem for me with electrics and the systems, is that my knowledge and experience is limited.

Yet when I read many posts I am often surprised, by the reported events. Why, is an obvious question, the answer with me, is that the equipment I have, does not do what is reported. Yet, that does not mean that other equipment does not behave differently.

I do not buy cutting edge stuff, not any more. I tend to buy state of the art stuff, sold at modest/budget prices.

I am assuming that the stuff I buy, is nearer an emerging convention, driven by manufactures feedback and user experience. In other words an emerging standardisation.

An example is the Futaba Tx and ESC logic. If the throttle is not reversed with Futaba Tx as far as the ESC is concerned, the throttle is at max and will not start, as the manufacturers have built in that logic. If however the Tx is reversed and the Tx throttle is at max, the ESC logic is, the throttle range is being set, do not start. These characteristics seem to becoming the norm, or are the norm, as all my ESC conform to the logic.

I can only assume that there is none mainstream stuff out there that is different enough that its logic is not as safety orientated.

Some of the motor experiences seem at odds with observations, where it is suggested that a motor that is not free to rotate destroys everything within a hundred yard radius. Having observed quite a few mishandled motors over the years, I can honestly say, I have seen them pulsing away, as the esc tries to set up the timing or lying there stalled rapidly overheating, particularly big motors.

Not long ago I retrieved a powerful motored M e109 that had crashed. It just lay there dormant, no big hole, just one burnt out motor.

It seems that more emphasis is required to buy standard operating equipment, and to be wary of anything that is old as it is potentially none mainstream.

As with most electric modellers, my major handicap, is my limited access to the wide range of propriety equipment, to be able to speak definitively. As the one exception makes you a fool or liar.

My mantra is greater standardisation of features and operating processes. No one would today buy a car wher the brakes were on the steering wheel, the clutch pedal on the right and the throttle was a slider on the steering wheel, or would they?

[Andy48]

Hmmm. Not sure about that. Drove a car not long ago where the steering wheel was at the passenger side, there was no clutch pedal, and the handbrake was operated with the left foot.