Electric Flight Safety

[Greybeard]

We had a discussion at my club on ways to improve the safety of electric flight systems in the pits and transit to and from the flight line, in particular methods to prevent inadvertent starting of the motor. We already follow the requirement that the models failsafe should be set to stop the motor on loss of a proper signal.

One idea is simply to delay the connection of the battery until the model is on the edge of the landing strip and to disconnect it there immediately on landing. This is fine if the connection plug and socket is readily accessible or if a suitable arming plug is fitted as has been discussed in other threads.

As an alternative we have a proposal to rely on a spare transmitter switch mixed through a spare channel so that it inhibits the throttle channel thereby preventing operation of the throttle. The idea is that the throttle can then only be brought into use by moving this switch to the “on” position so that the throttle channel becomes operative. This, it is felt, will allow the batter pack to be connected in the pits and the model to be safely carried to the flight line without any possibility of the motor starting even though the motor and ESC is live.

Yet another proposal suggests turning the transmitter off prior to delivering or collecting ones model from the strip so that its receiver goes into failsafe and thereby ensuring that the motor cannot start.

I will welcome others thoughts on these proposals in order to help me clarify my thought as at the moment I have some unease with the latter two ideas.

[malcolm woodcock 1]

I usually fly alone so I always have the tx off and failsafe activated except when ready to go. Thank God for 2.4 Ghz.

[ken anderson.]

hello GB ........whats the reason behind the proposal? .....we have at the moment 112 members and I think that it would be a hard rule/change to police.....could you not have an interim start/finish box..between the pits and runway for the arming and disarming of electric models? ....

ken Anderson ne..1. proposal dept...

[Greybeard]

We want to adopt the best safe practice so are investigating all proposals hence my request for input from those here.

[ken anderson.]

ok GB....I would have thought a half way box would be the way to go.....keep the models and pilots away from the runways when they are connecting/ disconnecting the batts.....as there is nothing worse than someone on or near the strip messing around with a model when other flyers are attempting to land / takeoff.....

ken Anderson.....ne...1 .......proposal dept..

[Greybeard]

Posted by ken anderson. on 19/10/2013 16:34:28:

ok GB....I would have thought a half way box would be the way to go.....keep the models and pilots away from the runways when they are connecting/ disconnecting the batts.....as there is nothing worse than someone on or near the strip messing around with a model when other flyers are attempting to land / takeoff.....

ken Anderson.....ne...1 .......proposal dept..

I agree but that does involve carrying a live model which is something we wish to avoid. Your input is appreciated.

[Tony Bennett]

sorry but you carry a live ic powered model with the prop turning round out to the flight line.

though an arming plug is a good idea.

[WolstonFlyer]

I have a throttle cut mix set up on all of the models in my Spektrum DX8, it has worked very well for me so far.

[Bearair]

I would rather rely on my sense of not getting near the prop or moving the throttle stick. Using an arming switch or similar just makes it more complicated in my opinion. From the moment the model has the battery connected I think big, sharp spining object and treat the model and tx accordingly. If some people really have an issue then make everyone walk with the model with the prop gently turning, they wont forget then!.

[Wingman]

Tony and Bearair have it right - if you're that scared of electric flight don't do it - also only include those who actually fly electric in any discussion about electric flight safety matters,

[John Privett]

Greybeard, what is the actual problem, or perceived problem, you are trying to regulate against? If everyone treats an electric model in the same way they'd treat an ic model with the engine running then is there actually any problem? I can't help wondering if you're trying to devise a solution without knowing whether or not there's even a problem, or what it is.

The ideas about fail-safes are ok up to a point, but won't work for the folks still using old 35MHz PPM gear. You also risk causing more accidents than you prevent when somebody activates their fail-safe because you say they have to and then discover it's been inappropriately set...

[Bill_B]

Posted by Wingman on 19/10/2013 17:41:06:

Tony and Bearair have it right - if you're that scared of electric flight don't do it - also only include those who actually fly electric in any discussion about electric flight safety matters,

Whole heartedly agree!

[Greybeard]

I’m not afraid of electric flight, neither is anyone else that I know of, but the medium has an inherently higher risk over i.c. engine insomuch that an apparently benign motor can become active unexpectedly by for example catching a throttle stick with a lose neck strap or simply because the operator forgot that the model was armed. I for one have seen enough of other people’s body parts together with associated blood and flesh flying around a pit area not to want to see a repeat performance.

The point of my question was not to find out who suffers from an electric flight phobia but rather to glean sensible ideas or experience of the points I raised in the opening post. I would like to know, for example, if it is possible for a powered but shut down ESC to fail to an active state such that the motor will run. In other words could the motor start with the receiver in failsafe mode?

[Johnny Kirkham]

I had a close one myself when i first bought my foamie wot 4 (my first electric model) by knocking the throttle stick whilst carrying it out to the flight line this prompted me to do a throttle to throttle mix assigned to one for my switches to kill the throttle stick. So far its worked ok for me.....and its easy to do too

Johnny

[Bearair]

Greybeard I do have lots of experience of electric flight, lots with models (6 and 10 cell) that will do you lots of harm to you if not treated with respect. I also have experienced how people set up models, even with something as simple as a rate switch I have seen people who set them up with different settings between models. IE on one model full rate is down on another full rate is up! That is why I think involving a separate switch is a no go. You can be sure someone will set up there inhibit switch as down for arm on one model and up for arm on another, then between flying sessions forget which is which.

My suggestion to set up models so the motor is never completely stopped would in my opinion be about the easiest and safest way to do it. As you have said it is the fact that the propeller is not going around that causes people to be stupid.

As for things like the escape failing and causing the motor to roar into life, yes it could happen in exactly the same way as a throttle servo could go wrong and open the throttle wide in fact I have seen this happen.

I still believe the only safe way is for people to get it in their head that once the battery is connected the prop is dangerous, maybe your club could come up with a S.M.A,R.T. like saying. Battery Armed Prop Spins type thing! And then grind it in to everyones brain!

Roger

Edited By Bearair on 19/10/2013 20:38:11

[Masher]

"I would like to know, for example, if it is possible for a powered but shut down ESC to fail to an active state such that the motor will run. In other words could the motor start with the receiver in failsafe mode?"

Although it is very unlikely, I'm afraid it is possible if a fault develops in the receiver/ESC circuitry. The only certain way to be safe is not connect the battery.

We have these discussions at our club and one bloke made a good analogy I think: If you think of a loaded shot gun being carried around "broken" so it can't go off - is there a way you could fall, close and shoot the gun? - unlikely but yes not impossible - the only safe gun is an unloaded one

[Martin Harris - Moderator]

Simple answer - make sound and smoke systems compulsory and active from battery connection...

Well it works for IC models!

But seriously, drum into people that a model with its flight battery connected must be regarded in exactly the same way as an IC model with its engine idling. We have a start/park line (and preparation benches) at the front of our pits. Whether IC or EP, you start or connect your model in front of that line and carry it to and from the flight line from there. At the end of the flight you disconnect the flight battery before taking the model past that line.

You are still free to have whatever additional safety device that you wish. I have an inbuilt throttle lock (defaults to a soft key) in my transmitter which I opt to put on a dedicated switch but I still regard the model as if it were live (which it's only ever a switch fault or error on my part away from). The only safety device that you should ever rely on is to never get complacent and always bear in mind the worst case scenario.

Edited By Martin Harris on 19/10/2013 21:17:05

[Joe Beavis]

I have a slightly different slant on the matter. I have drilled the casings of my DX6i and Futaba 6J transmitters so that I can fit an 'R' clip (made from a coat hanger) across the front of the throttle (mode 2). The rudder is still operable for checks, but the throttle cannot be moved. Apart from being easier for people like me who are better at drilling holes than doing clever electonic wheezes, it is plain to everyone around that the throttle is disabled. I leave the pin in until blast-off, and refit it before I pick the model up. Care is required to avoid drilling through the throttle trim switch! It might possibly be frowned upon by the manufacturer, though!

Joe Beavis

[Max50]

If you arm the model at the flight line; how do you restrain the model, while holding the transmitter and plugging in a safety connector. I wouldn't like to put my tranny down on wet grass while restraining the tailplane and plugging in a connector. If you had a restraint at the flight line then that would take one action away, but i would think a condition hold on your transmitter in the pits would be better, and be part of your SMART checks.

As an i/c flyer i was wondering what steps you electric guys take in arming, as an electric motor wants to still keep turning whatever is in the way.

What do the competition F3A people do with their mainly electric planes?

Quite interested to know?.

Also if you're taking your 'A' or 'B' test with an electric; what is the examiner looking at with this action of arming, and where the arming should be done?

[Greybeard]

Posted by Max50 on 20/10/2013 08:19:12:

If you arm the model at the flight line; how do you restrain the model, while holding the transmitter and plugging in a safety connector. I wouldn't like to put my tranny down on wet grass while restraining the tailplane and plugging in a connector. If you had a restraint at the flight line then that would take one action away, but i would think a condition hold on your transmitter in the pits would be better, and be part of your SMART checks.

As an i/c flyer i was wondering what steps you electric guys take in arming, as an electric motor wants to still keep turning whatever is in the way.

What do the competition F3A people do with their mainly electric planes?

Quite interested to know?.

Also if you're taking your 'A' or 'B' test with an electric; what is the examiner looking at with this action of arming, and where the arming should be done?

We have a model restraint stand near the flight line which has a transmitter stand incorporated.

[Greybeard]

My unease with the proposals in my O.P. stem partly from my distrust of electronic switches and the likelihood of them failing to the live state. No one seems able to give me a guarantee that this cannot happen therefore I must assume that it can and at some point will. I use the same philosophy when buying lotto tickets.

Secondly the use of an inhibiting switch invites both confusion and complacency so I have little confidence in that method either.

Turning the transmitter off and relying on the live receiver’s failsafe on 2.4 systems may be the best way forward but I am suspicious that interference or a receiver fault could still activate the system.

The more I think about the problem the more convinced I am that a mechanical isolation device in the battery circuit is the only safe way to proceed.

[John F]

I don't know Greybeard; the amount of hand injuries, and one nasty chest injury, I used to treat for years whilst on Duty Medic on weekends at RAF units, for IC engine related injuries tells me that the main danger is not really electric.

Folk carry spinning props to the flight line all the time and I am surprised that this discussion within your club is aimed at electric with proposals to try and make a perceived threat safer when the clear danger is a spinning prop right in front of you.

Accidental activation of an electric engine would not necessarily mean that body part would also be in contact or the vicinity of the prop; you would have to have a precise set of circumstances. A constantly spinning prop guarantees a mangling no matter at which point in time your digits stray into the spin area.

With electric you might have a "Oh, OK I'll knock down the throttle, that scared me" which might be fuelling these debates but, as a Medic, I can tell you that the injuries that come to the Med Centres at weekends or evenings where I have ever worked, is almost always down to IC.

You could fit a restraint to the throttle though as, Joe says, which then alleviates most risks but I can't help the feeling that the argument is fuelled by disapproving IC engine users. The snort of disgust that comes from the patient when I say that it wouldn't happen if you used electrickery confirms there's a large amount of bias when it comes to seeing risk.

Edited By John F on 20/10/2013 08:37:36

Edited By John F on 20/10/2013 08:38:04

[Old Geezer]

I think I will stick to my battery isolating plug between the LiPo and the ESC? Follows the KISS principle - carry to take-off point, put plug in and fly, land, walk out to plane, remove plug, retrieve now inert plane.

S I M P L E S

[Greybeard]

In my experience the six or so hand injuries I have witnessed from i.c. engine operation have come from two causes, one is reaching through the propeller arc from the front to adjust the needle valve, and the other is grabbing at an unrestrained model that has started to move and catching the propeller.

The point has been made that electric motors react to obstacles in a different way to i.c. engines insomuch that they increase power when meeting an obstruction, so carry on chopping for longer than an i.c. engine that tends to stall on overload.

Electric power should be safer to operate than i.c. we simply want to make sure that it is.

[ken anderson.]

hello again GB......I use a hitec A9......and the throttle is stopped functioning by pressing the screen.....and then working again by doing the same.......I would imagine other modern radio's have the facility in to do the same...using a mix.......but again...at a club level how do you introduce it and police it (impossible) ........ and over the years I've seen a fair few accidents with 2/4st models.....owners falling over/model owners sticking their carol singer's in to the prop arc etc......compared to the occasional accident with an electric model....

ken Anderson....ne....1.... carol singers dept...