Electric Flight Safety

[John F]

I think a lot of this though is perceived risk rather than actual. You don't trust; a 2.4Ghz receiver (saying it might be faulty) or an electronic switch (which might fail). There are a lot of ifs there but a solution could be very easy.

A physical switch isolating a wire to the motor would, indeed, be safer as would a strap to restrain the throttle lever.

[DH 82A]

It's simple, an electric model is not " safe " until the battery is disconnected. In the same way as any mains electric appliance is not safe until the plug is removed from the wall socket.

[PatMc]

Re the OP ; it seems as if the club is putting itself into a "nanny state" situation. All that's required is the general advice that electric models should be treated as live with a potential for the prop to spin from the moment the battery is connected in the pits area with a reference to the advice headed "Electroflight" in the safety section of the BMFA handbook (P.41).
The application of personal safety measures is best left to the responsibility of the individual.

I completely disagree that electric power is inherently less safe than ic power - they both carry potential risks that should be respected and guarded against.

Edited By PatMc on 20/10/2013 12:49:26

[Simon Chaddock]

The original OP quotes the possibility of the throttle stick getting caught in clothing and opening the throttle,

In this specific case is there really a difference in the risk of it happening between an IC engine or electric motor and at full power would the degree of injury really be that different?

It of course possible that IC pilots are inherently more careful as the already rotating prop acts as a warning but in terms of risk of injury a human is far more likely (a 1000 times?) to put their hand in a prop than the chances of an electrical system failing 'on'.

One is current danger that the human brain can assess, the other is a very low risk event but unfortunately its level of danger tends to get assessed in the same way.

.

[brfc7]

Speaking as someone who has experienced a prop strike from an electric model I recommend to everyone to use a mix on the transmitter so you can disable the throttle stick.

My accident was with a hand launch electric glider (JP Pretty) which I had connected its battery so was live and I had a hold of it under the canopy behind the motor in my left hand with the model pointing across my body like I have done loads of times before. The difference this time was I have a neck strap and instead of unclipping it completely from the transmitter as I normally always would, for some strange reason I had unclipped it by the big plastic clip halfway down that can be unfastened to leave the strap around your neck and leave the hard to fasten hook on the transmitter. I bent over to pick up transmitter which swung the plastic clip around hitting the throttle to max which obviously resulted in the motor starting. I was very luck that I had a good grip of the model so it only got me about 5 times with small cuts on the forearm before the prop smashed and I managed to move model further away and close the throttle.

But I don't think this should be a club rule and should just be up to each persons own decision. Their is enough rules to be going with already.

baz

[Martin Harris - Moderator]

I consider that a club rule to protect others is a good thing, hence we don't allow "live" models of any kind behind a certain point.

What a club could and should do is to encourage its members to be aware of any risks and adopt practices to minimise any personal risks. For example, I won't allow a student to reach over a spinning prop to remove their glow connection, or carry a model with the propeller pointing in someone's direction - including electric models, which hopefully ingrains these behaviours into them when they are operating without supervision.

Thinking about when to arm an electric model and how to restrain/handle it is something to be done from the start and I find the least receptive to be older experienced pilots who were brought up in the predominantly IC days when electric power was a bit of a contradiction in terms!

[Greybeard]

Posted by Martin Harris on 20/10/2013 18:37:56:

I consider that a club rule to protect others is a good thing, hence we don't allow "live" models of any kind behind a certain point.

What a club could and should do is to encourage its members to be aware of any risks and adopt practices to minimise any personal risks. For example, I won't allow a student to reach over a spinning prop to remove their glow connection, or carry a model with the propeller pointing in someone's direction - including electric models, which hopefully ingrains these behaviours into them when they are operating without supervision.

Thinking about when to arm an electric model and how to restrain/handle it is something to be done from the start and I find the least receptive to be older experienced pilots who were brought up in the predominantly IC days when electric power was a bit of a contradiction in terms!

Thank you Martin, that is what we are working towards but have to establish "best practice" first; hence this thread.

[Greybeard]

One of the reassuring points to come out of this discussion is that no one has come forward to say that they have experienced uncontrolled restarts from shutdown speed controllers or receivers in failsafe, which gives me a little more confidence in them. So whilst it seems prudent to ask for an arming plug to be fitted to break the battery supply where possible we can also rely on the other means of preventing an unintentional restart as outlined in my opening post with a high degree of certainty that they will work as intended.

Thank you all for your responses.

[Erfolg]

The proposal has to come from an IC modeller.

As has been pointed out by a few relies, the dangers suggested are the same with a IC motor.

Typically anyone carrying a electric model, should be treating the model as if the propeller is turning. If the motor were then to start, the surprise and danger would be no greater than an IC motor going to full throttle.

For some models, an arming plug can be useful, although it is not a universal solution to all problems.

Arming procedures which have the modeller save by position must be a standard way of operation.

The F3a and similar models at my club deploy a variety of means of arming, dependant on access to the model. Some use arming plugs, particularly with plug on noses.

The fallacy that an electric motor will keep turning is not an absolute truth. Many will stall and draw a very high current. This seems a device used by IC fliers to draw a picture of a modeller being constantly assaulted by a spinning propeller until all that is left is a pile of flesh and blood. Just like an IC motor, which can keep on turning if the resistance is low and the power is high, it mainly does not happen. More likely the equipment will fail or there is a fire, if left.

As many others, I have seen far more serious and not so serious accidents with IC than I have seen over a similar period with electric models. I do not consider that IC models to be inherently dangerous either.

As has been suggested keep it simple. All models in the pit must be disconnected, unless immediately going to the flight line. Or have a arming compound as suggested, which models go into in transit to the flight line.

If there is not a problem, do not try and fix it, is my view.

[Shaunie]

I think the "one type of propulsion is more dangerous than the other" argument is a bit pointless.

In some respects they are the same i.e. the propeller is always dangerous if the model is in a flyable state.

In others they are different i.e with I/C the prop is always turning so accidental contact will always cause injury, but with electric the apparently benign prop which can be treated with disdain as a result can turn into a dangerous device with just about no warning.

They are both dangerous just with slightly different characteristics, to use the shotgun analogy previously mentioned, over-and under or pump-action, either way you can get shot by one.

Trying to establish best working practice on things like this can take a lot of heated discussion .

Luckily I've never seen a serious prop injury but many years ago I did see .61 glow at almost full throttle assault a gallon of glow fuel, the spray was spectacular and the can looked like it had been in a blender! Pilots comment "and it was a new bottle too!" Caused by picking up the Tx by the neckstrap and it caught the throttle stick, no model restraint as this was about 20 years ago!

Shaunie.

[Chris Jones 7]

My multirotors all have an arming sequence that needs doing before the rotors will turn. This is usually on the flight control board but I wonder how long it will be before these are built in to ESCs or even electric specific RXs.

Personally I use a throttle cut on the TX, I started when I was flying helis and seeing as how no one could give me a good reason not to, all my models are set up this way. Be conscientious when initially setting up the model and checking operation and it's no more confusing or dangerous than getting the ailerons reversed (not that any of us have done that of course)

chris