Hi everyone,

I have an open question which I hope will generate some answers that I can take back to the Australian - New South Wales "Control Line Aircraft Society"  (C.L.A.S) which deals with Control Line related issues within the State of NSW and reports back to the Australian body - the MAAA.

Just to fill you in, I've been flying C/L Aerobatics for approximately 40 years and for the past 18 months been totally 'Electric'.  Since last September I've also been the President of C.L.A.S and as with most Control Line Clubs we deal with many issues including rule changes, competitions, registrations and other related topics.

At a meeting held last night a member present brought up the issue of 'Electric' Control Line models and their safety - particularly that of F2B - Aerobatics.  This member (who said he had experience in Electrical engineering and models) said he feared what would happen if an Electric model was 'out of control' and risking injury to the pilot or bystanders.  He feared that the motor would not stop rotating until the battery became disconnected or some other catastrophic failure occurred causing the motor to stop.  He cited the example of a model in the process of taking off and 'coming in' toward the pilot and the electric motor continuing to rotate after striking 'something' unlike an IC engine which will normally 'stop' if it has a 'hard' strike on some object/person.

I explained to this member that I use an Phoenix ICE 50 ESC and that my understanding of the system was that if the prop struck something hard that the Amperage would increase over the set limit on the ESC which would then automatically stop the motor. The member told the meeting that he has seen instances of prop strikes occurring where the motor has continued to run and the ESC has not done its job in stopping it from running.

This member wanted the meeting to discuss safety and due to his concerns his suggestion (particularly for F2B models) was that each EL model be fitted with a R/C receiver which would be activated by a 'Safety Officer' outside the circle during a competition if a dangerous situation arose.  Let me say right here that I don't agree with this person or the suggestion to use R/C as a safety cut-out mechanism.

I'd like to know - and will take back responses to the next C.L.A.S meeting - of any person who has had experience with 'prop-strikes', collisions etc, and of what has happened to the aircraft/motor etc after the incident. (whether it kept rotating etc) - If you could include your individual EL set-ups in your replies this would be much appreciated also.

Many Thanks,

Bruce Hoffmann

I don't know of any magic that turns off a runaway wet engine airplane. In fact an electric prop is more likely to do a comeapart on a hard strike rendering it harmless.  Don't like the thought of a safety officer to kill the engine but if you must dabble in such insanity it should apply to wet engines as well as electric.

I've got a response for you to take to this guy. Tell him he's freaking nuts! You can tell him I said so...

Bob Hunt

Yep IC engines don't stop even after prop, spinner and prop nuts have departed the lane while still on the ground.   Happened to me on a practice flight at VSC this year.  Could have stopped the engine sooner, but helper wouldn't turn loose of the plane and for once didn't have a rag in my pocket.

Bruce,
It sounds like this flier doesn't want to see electrics take over and is looking for a way to make it difficult to use them to the point that people just give up. This is a typical political control technique to outlaw something by not naming it specifically. As was pointed out you should remind them that IC engines don't stop either with a prop strike, as a matter of fact the idea that our electrics do stop was something another electric hater tried to say was why they weren't as good as IC in the grass. It can also be pointed out that during starting process we electric fliers don't have to get our fingers and hands close to the spinning prop to hold the plane or to make engine adjustments.

I have had personal experience with electrics that have hit a stationary object that re-kitted the plane and the motor stopped running just like an IC motor would. For minor prop strikes on takeoff (i.e. the tail gets blown up by strong wind) it again acts just like an IC engine does it all depends on how much force the tail is lifted with, a little buzz won't do it but hard one will. If you come out of a maneuver low it is the same thing. For a minor buzz that shortens the diameter our electrics still run the same RPM unlike an IC that would increase RPM and add stress to the prop. Even if we lose the whole prop we still only turn the same RPM unlike an IC engine on a shaft run. In deep grass or bumpy grass takeoff strip with small wheels we are sometimes at a disadvantage because the grass can cause drag on the prop blade that doesn't damage the prop but does cause high current that will shut the motor off. In this instance the IC motor can sometimes keep going and be pulled off the ground, but this does not present a safety problem.

Bottom line is if the incident will stop a IC engine it will stop an electric.

Best,        DennisT

covering what others have said - I have had prop strike and the ESC shut down the motor pretty quick smart.

I have also thrown a blade - which also shut down the motor (thank goodness)

I have also hit the ground (handle failure) motor stopped on impact........


seems pretty safe to me.

Do make sure that this clown never figures out that E-CL is quiet, or he will require noise makers so folks don't wander into the circle.

I want an ESC that makes my motor sound like an R-2800

I would stress that electric models ALREADY have a proven system for shutting down the power as discussed here.



The only item I would like to see everyone use is a visible/accessible arming plug or some other means to quickly disconnect the power - but I am not ready to mandate it yet either.

The only item I would like to see everyone use is a visible/accessible arming plug or some other means to quickly disconnect the power - but I am not ready to mandate it yet either.

Visible, accessible, grippable.

I don't like the current arming plug setups that I see, for entirely the wrong reason.  From practical considerations having a connector with a honking big loop of wire sticking out of the side of an otherwise beautiful electric stunt plane means that someone will be easily able to pull it in an emergency.

But oh my, it can look ugly.

My RC club recently adopted an informal rule about disconnects on "big" airplanes.  This happened about 30 seconds after a new member put a 60-sized 3D plane with a seven cell LiPo pack in it on the table, then took the wing off and started fishing with the wires to get the battery connected.

So I would like to Formally Challenge the electric CLPA community to come up with a disconnect scheme that's practical, reliable, inexpensive, and knock-your-socks-off good looking.  This is entirely motivated by a sense of altruism and love for the hobby, of course.  No self interest whatsoever.  Consider the deadline to be the day that I finally get the $$ lined up for an electric setup and start building .

The KR Governor/Timer gives closed loop speed control without the use of an expensive ESC. If the motor stops turning the governor shuts down the ESC. These are available in the US from RSM Distribution. I don't know how long the prop stoppage must be for thr Governor to shut the system down.

Pat

Keith's governor/timer unit sounds very safe although I am currently using Castle Creations Phoenix ESCs and Will Hubin timers.

To address the original post, I have been flying control line electric since 2006 and have probably crashed more C/L electrics than anyone else alive (see my signature below). My original electric S-1 Ringmaster has been rebuilt at least 13 times (I have sort of lost count). In two instances the motor continued to run following the crash. Both times the plane hit almost straight in into turf. The first case was the original S-1 with a cheap Chinese ESC and the second was my E Baby Ringmaster with a Phoenix 10 ESC (a friend was trying it and got dizzy). In both cases the prop shed both blades in the crash and in each case I simply trotted over and pushed the timer button to stop the motor. In all other crashes the motor stopped and all components survived except for two batteries that detached and hit the motor mounts (no smoke or fire).

John

Worse yet is those dag nab hand launch gliders. Why they could put out an eye.  Any one launching one of those there things should wear safety glasses and a helmet.

You miss the point.  That $1 ($5 if you use super-zoot contest wood) glider should be equipped with a $40 receiver and a firecracker, so that a range safety officer can destroy it if it threatens to put out the eye of an innocent bystander.

I would like to throw my two bucks worth into the hat, just for the record and for what it's worth.

I have had a couple of prop strikes now using electric and found that the Castle ESC stopped the engine each time when the current limiter was enabled.  There was one occasion early in the piece where I had the current limit turned off and the up line broke. After hitting the ground inverted, the motor spun the prop off the shaft (being a pusher) and the motor just sat there running doing no harm.  

I can only guess if the prop were a tractor, it possibly would have broken, being a thin electric and the end result would have been that the motor would have kept running with no blades on the prop. Anyway, at the time, there were people around and nobody got hurt.

I have seen IC engines do some pretty dangerous looking things, like:

- engine leaving the model and flying through the air at 100mph,
- model fly aways after lines were cut in combat,
- people's hands and arms severely cut resulting in a trip to hospital
- engine kept running after throwing prop and revved it's head off
etc.

I have seen none of these things happen with an electric model yet.

I guess if we had to apply a Workplace Task Risk Assessment to the idea of flying model aeroplanes for sport/entertainment, we probably wouldn't be allowed to fly them at all... i.e. no machine guarding, possibility of serious or fatal injury, damage to environment etc and the hazard controls would have us all using electric starters, wearing fireproof suits, full face helmets and breathing apparatus, as well as all the other controls, like MSDS (Material Safety Data Sheets) and an Ambulance and Fire Brigade standing by.  The same would apply to riding a motorcycle on the road!

I guess what I am trying to say is, what is the likelyhood of a problem occurring where serious our fatal injury would warrrant not flying?  In our sport, we cannot eliminate all the risks, so therefore we have to put some controls in to reduce the risks, but they cannot be entirely eliminated.  

Like spectators at a car race, even if you move them back so far from the action that they would see better watching TV, there is still a chance a wheel or debris could fly and hit someone.  These are acceptable risks we take to enjoy entertainment. I think the spectators sign or accept these risks as part of the conditions of attendance.

From my experience and knowledge of flying electric, I see that less harm is "likely" to be caused than using IC engines, because:

a) you dont have to flick start the engine or even put you hand near the prop and risk getting a cut or bruise,
b) you dont have to mix or use dangerous chemicals like fuel! (ie ether, kero (jet fuel), methanol and nitro methane!),
c) you dont have to worry about a fuel fire caused by the fuel igniting.
d) there is less likelyhood  that the engine will come loose and jettison due to vibration

but on the down side,

a) there is a very slight chance that a motor might not stop if not set up correctly in a crash, and will continue to run until someone stops it or it burns out.  The consequences we can be unsure of because it hasn't injured anyone yet.
and b) the battery might catch fire it there is a short in the wiring or faulty component.

In my opinion, the more I think about it, electric control line is actually safer than IC engines the way we are using them now, so why would we bother turning our control line models into radio controlled models just to satisfy the fear of one person that something "might" happen.

I do think that a battery isolation plug is a good idea if the battery cannot be easily and quickly disconnected, but again, I have always seen the timer start/stop button work and not heard of one failing yet.

Regards
Warren

Tim!
We can make them play old Pink Floyd tunes ...
   Dean

Moment lapse of reason???

On the topic of 'Arming' switches - I recently found this one.  A friend was using it and so I've now started to as well.  The female section of the plug is mounted permanently in the model, when the battery is installed the + lead is connected to one side of this plug inside the model - from the other side of the plug the + lead goes to the ESC.  The 'neg' lead of the battery is connected directly onto the 'neg' lead of the ESC.  A plastic 'male' plug is used to plug into the female from the outside of the model thus completing the circuit.  Up until this happens the circuit is 'dead'.  The plug is easy to use - it clips in and makes good contact but you don't need to worry about pulling the side of your model off when you try to pull it out (like a 'deans' plug!) - it comes out again quite easily.  I keep a few of the male plugs 'spare' in my flying box just in case I lose one, however I have the one on the model attached with a short length of string so that it should always be there with the aeroplane.  Think it looks quite neat. Available from Draganfly innovations.. $10.95 + postage and is in the US so close and easy for you guys!!  :  http://www.rctoys.com/rc-products/MPI-ARMING-SWITCH.html

Bruce H

We've been using these too and had zero issues with them. It also eliminates the "sparkage" when plugging in the battery...

Overall, I think electric planes are safer for their operators than IC-engine planes.  They have different risks, though, and I fear that electric cheerleaders are not emphasizing them enough.  The biggest risk I see is of people walking through the circle while an electric plane is flying.  This is because:

1. The general public doesn't understand the risk, particularly of a quiet airplane.  An F2D model sounds as dangerous as it is.  An electric stunt plane is like a rattlesnake without a rattle.

2. People now fly electric airplanes in parks and schoolyards where they wouldn't fly engine-powered airplanes.  Those are the places where you'd find the general public who would walk through the circle.

Solution: Don't fly in public places.  Put safety cones around your circle.  It takes 40 for a circle big enough to fly with 70-foot lines.  Post a lookout.

Do fly in public places, and make sure that your lookout has some to give to interested passers by!  But do have that lookout.

Some folks were horrified to see Igor walk to his handle at the 2008 world championships while his airplane was unattended.  Their main concern was that he would become medically incapacitated on the way to the handle.  I would add to this the possibility that the timer would start the motor prematurely.  One should assume that a single-thread digital system can jump to any place in its program at any time.  Solution: Always have a human holding either the airplane or handle while the system is armed.  An alternative would be to anchor the handle any time it's not in the flyer's hand.  This could be done by sticking a screwdriver through the safety thong into the ground.  When flying alone, a stooge protects you before takeoff, but not after landing.  

For me, the concern is more that I'll trip over my shoelaces, or pick up the handle upside down and still be fumbling with it when the plane starts.  The chances of an inelegant moment are much higher than a heart attack or stroke.

I don't think the risk of timer or ESC jumping to "go full on" is very great given the extensive testing done by consumers the world over -- but it's better safe than sorry.  A stooge is easy to use, and if you're flying alone that screwdriver will hold down your handle while you walk the plane back to the stooge for the next flight.