Throttle cut button - why the bad press?

[Mike Blandford]

I also use a throttle disable switch with electric, and have for many years. It is automatic for me to switch to the "safe" position before handling a model. Specifically, I use a "sticky" throttle disable, where, once disabled, it doesnt allow the throttle output to change from minimum unless the throttle stick is moved to minimum, so if the throttle stick gets knocked, and then the switch is changed to "enable", the motor still won't start.

I have this in ersky9x firmware as a simple "safety switch" selection, but it may also be implemented in openTx with some logical switches and special functions.

I'm curious regarding a club insisting that the battery is not connected until you are at the flight line, how do you deal with range checks when the radio needs the battery connected?

Mike

[Jon H]

Posted by Toni Reynaud on 02/05/2018 17:20:19:

Last week (after flying only electric for the last 12 years) I landed my plane, put the TX on the ground in the pilot's box and walked out to get the model (standard procedure). I picked it up and took it back to the pits, then went to the box to pick up the Tx. Walking back to the pits to disarm the plane I was accosted in conversation by another member. I then walked back to my plane, bent over to remove the battery hatch and somehow knocked the throttle towards full. The plane zipped across the pits and struck another member's plane, causing sufficient damage to give him a couple of weeks work repairing it. Fortunately there were no human injuries except to my pride at having created such a stupid incident. I have since been on the internet and found out how to program a mix on my Spektrum Dx7 to act as a throttle cut/hold/disarm (choose your own favourite word).

The moral of the story is that positively preventing the motor from turning by using a dedicated switch on the Tx is a good idea. All I have to do now is program that into every one of the model memories, and remember to use that switch every time I go to fly.

I know the bmfa recommend leaving the tx behind but its utter stupidity for this exact reason. the same would have happened if someone else accidentally booted it over while you were walking out. I always take my tx with me as its the only point of control for the model and if I'm not hanging on to it then the model is essentially out of control.

[john stones 1 - Moderator]

What ifs eh.

Not so sure the BMFA recommend leaving a 2.4 tx behind ? same could happen with a 35mhz set though, had all these conversations at club level many a time.

[Martin Harris - Moderator]

They most definitely don't - I had this conversation with Andy Symons a week or so ago and the anomolies in the documentation are in the process of being addressed.

[Cuban8]

Don't you just love 2.4 ? All that stuff with the old gear.........crystals, peg boards, arguing over 10 or 20 kHz spacing, adjacent channel checks, dirty and/or loose aerials, glitching electric models, getting shot down by rogue modellers in the next field or by a dopey club mate, even clubs and odd clubs, having gear tuned, CB in the old old days...............

[Rich too]

Posted by john stones 1 on 02/05/2018 14:51:47:

Not a dig Martin, I know you're a sensible fella, at times I wonder how we allow members to drive to the field without a risk assessment though, we do like to complicate and deeply think everything. Only my opinion though, feel free to disagree.

At least with IC you KNOW its live when its running! Perhaps thats the reason for arming electric at the flight line?

I only flew electric briefly, but the only near miss prop incident I've had was with electric when I forgot it was live.

[Martin Harris - Moderator]

Getting back to the main topic...

Posted by Biggles' Elder Brother - Moderator on 02/05/2018 15:43:47:

Posted by Martin Harris on 02/05/2018 14:45:49:

BEB, I'm currently safety officer for my club and I don't believe that I and at least 6 of the 7 members of our committee have any trouble understanding programming safety switches. I believe in them but do not rely totally on them so I will continue to encourage (and openly practice) safe handling procedures.

I'm also slightly conbcerned with your second sentence. I'm sure its not what you meant, but in actuallity it is a catagoric statement. It says basically you won't rely on electronic/software interlocks you will continue to promote safe mathods instead. Frankly that your methods offer any real advantage is your opinion, to which of course you are entitled, but it is not a fact. I went to some lengths in my post to point out I was only expressing my opinion - therefore I feel justified in pointing out when others state what is only their opinion as fact.

BEB

I can't see anything other than clearly stated personal opinion and facts relating to my own practice... Perhaps you've misinterpreted my last words as these refer to my actions within my club as a "senior" pilot, examiner and safety officer.

Regarding rules about arming electric models, we do have one which states that IC models may not be started and electric models may not be armed behind a clearly defined line at the front of the pits. Running IC engines are NOT waved about in the pits as suggested may happen at some clubs in a previous post!

We provide a starting bench and other benches for connecting batteries at the front of the pits as well as a line on the ground which can be used for the same purposes should people prefer. On busy days, models are moved from their parked position in the pits to the starting line before being readied for flight. It is a very simple rule, understood by our members and easy to comply with. In years gone by models have careered through the pits when procedures were more lax - I see it still happens at other clubs!

Range checks are done with models on the start line.

Regarding the title of this thread, do safety switches get a bad press?  The problem is the human factor involved in their operation. The bottom line in my philosophy is that safety switches are a good thing and to be recommended but for the best protection we simply need to handle our models in a safe manner. It is no different to a gun with a safety catch - you wouldn't rely on it to point it at someone, would you?

 

Edited By Martin Harris on 02/05/2018 19:27:24

[The Wright Stuff]

To pick up the (questionable) gun analogy, if the alternative was waiting until I was being shot at on the battlefield before putting the bullets in, then yes, I would absolutely use and depend upon the safety catch. That's exactly what it is designed for. It is proven to work.

Edited By The Wright Stuff on 02/05/2018 20:08:57

[Martin Harris - Moderator]

I'm not sure why it's questionable. How would you react if I pointed a shotgun at you? Would you be happy if I said, "Don't worry, it isn't loaded and it's got a safety catch?" In your army analogy, how do you think your Sergeant Major would react if you pointed that loaded gun with the safety catch on at him - or anyone that you didn't intend killing?

[PatMc]

I use the "sticky" throttle disable method on a Taranis as described in Mike Blandford's post. I've also added audible warnings to sound every 10 secs when either the enable switch is & the throttle is closed or the switch is off but the throttle open.
I'll be using the same system when I migrate models across to my new OpenTx Horus.

[The Wright Stuff]

Posted by Martin Harris on 02/05/2018 20:20:36:

I'm not sure why it's questionable. How would you react if I pointed a shotgun at you? Would you be happy if I said, "Don't worry, it isn't loaded and it's got a safety catch?" In your army analogy, how do you think your Sergeant Major would react if you pointed that loaded gun with the safety catch on at him - or anyone that you didn't intend killing?

Sorry, Martin, but this is not a useful analogy. Nobody is deliberately pointing anything at anyone. If a gun was accidentally pointed at me, I would much rather the safety catch was on than not on.

[Martin Harris - Moderator]

Of course they aren't and I fully support the use of safety switches/systems. But the principal adopted for firearms of exaggerated care must have relevance where we have machines with the capability of inflicting serious injuries and worse under our control.

[Biggles' Elder Brother - Moderator]

Posted by Martin Harris on 02/05/2018 19:22:00:.

Perhaps you've misinterpreted my last words as these refer to my actions within my club as a "senior" pilot, examiner and safety officer.

Ah a senior pilot eh? - I'm touching my foreloick already - honestly guv!

BEB

[Martin Harris - Moderator]

I did wonder if I should use that term and put it in quotes but it is a term used within my club for those who are expected to set a good example or make the odd decision about the runway of the day, do a bit of instruction etc.

Don't worry BEB, you may still address me by my first name...

[Steven S]

Posted by Toni Reynaud on 02/05/2018 17:20:19:

I have since been on the internet and found out how to program a mix on my Spektrum Dx7 to act as a throttle cut/hold/disarm (choose your own favourite word).

The moral of the story is that positively preventing the motor from turning by using a dedicated switch on the Tx is a good idea. All I have to do now is program that into every one of the model memories, and remember to use that switch every time I go to fly.

I also learned how to program a switch on my Tx and then put a piece of RED heat-shrink on it.  I also added a voice alert to the switch.

Edited By Steven Shaw on 02/05/2018 22:42:50

[The Wright Stuff]

Excellent, Steven. I've seen the heat shrink method of highlighting switches used increasingly over the last few years, and it's a great idea.

Having thought about this whole issue overnight, I suspect it is a bit chicken and egg. The human factor may be seen as a weak link and so the concept of an interlocked throttle cut/hold/disarm at the transmitter is dismissed as a tertiary safety device, and largely overlooked as optional, at least in my experience. But because it's not seen as a primary safety device, it's not taught and ingrained, so lots of people don't bother.

So if a club wants to have a rule whereby the model is not 'armed' until it's at the flight line, then fine. As far as I'm concerned, if the motor doesn't start when I accidentally knock the throttle stick up, such that multiple points of (human and/or electronic failure) would need to occur before the motor could start, then it's not yet armed.

Whether or not the battery is plugged in is almost as irrelevant as whether an I.C. model is fuelled up. That certainly didn't used to be the case with early radio sets, DC motors, and simple speed controllers, but with modern equipment, correctly set up, the concept of 'the electric motor can spring into life when you least expect it' is getting to be outdated.

Edited By The Wright Stuff on 03/05/2018 09:18:56

[Nigel R]

"the concept of 'the electric motor can spring into life when you least expect it'"

It's safety advice from the past, for sure. Back in the days of brushed motors, 35MHz, pre-PCM with failsafe, interference, and on/off switches, I can see that being the case. These days, 2.4GHz, brushless ESCs, failsafes, its about as likely as the chance of lightning strike or lottery win (and probably less).

Assuming you don't physically move the stick, you would have to experience an extraordinarily unlikely set of failures before an ESC decided to start spinning the motor without your say so.

The most likely cause of "unexpected motor action" is knocking the TX stick. Adding an interlock on the TX in the form of another switch reduces that possibility by a huge degree.

Programming a mix+switch to disable the throttle stick, is a brilliant idea.

Annoyingly, I can't do it on my older DX6i so I will have to swap the throttle cut button for a toggle switch!

[Martin Harris - Moderator]

Don't underestimate the human factor, TWS - it has an almost limitless ability to find a way to defeat the best of precautions. From your other postings, I'm know that you're very knowledgeable, intelligent and analytical but these qualities didn't prevent a clubmate (and he's not alone from what I've read) turning off his transmitter while attempting to re-trim his model in the air. This was on a transmitter that he'd owned and flown with regularly for several years. I doubt that any designer even vaguely suspected that people would find this so easy to do.

While I respect your confidence in the programming and operation of your safety precautions, abilities at my club run from advanced programming to those who have difficulty selecting a different model on their transmitters. Can I, as safety officer, really have the confidence to put other members at risk by relaxing a very simple procedure requiring pilots to connect the power source for what can be a very dangerous piece of equipment (e.g. anything up to a 7kW system driving a 20 inch knife edged carbon propeller in one case) in a location which puts the hazard safely away from others? At what point do I say that pilot A is allowed to use a switched safety system and pilot B is not considered capable?

Unfortunately, the more complex a safety system becomes, the more opportunities there are to make an error - sticky throttle systems are brilliant but rely on relatively complex programming - not everyone has the ability to program them or even follow a set of instructions. There is not a pilot at my club who is incapable of understanding that an electric motor is safe when the battery is not connected - although convincing them that reaching through a prop arc to connect that battery may not be the best idea is another story!

 

Edited By Martin Harris on 03/05/2018 10:53:30

[The Wright Stuff]

Martin, this is a good, intelligent, constructive, debate, and you raise some good points. But I still think that your implicit assumption that human error is more likely with electronic safeguards than with physical ones is rather over-stated.

For example, quite often I physically insert the battery into the model and do up the velcro straps in the pits, even if I don't connect the battery then and there. Fiddling with the velcro is the most time-consuming bit. Perhaps I get distracted at this point, and absent-mindedly connect the wires even though I don't intend to. One the cockpit/cowl is back on, I can't see at a glance whether the battery is connected or not. However, I CAN see the position of the safety switch on the Tx at all times. I GENUINELY believe that FOR ME, it is a safer approach, and LESS likely to lead to accidents, not more.

Human error is also the root cause of most I.C. related starting accidents. But the equivalent view would be to prohibit use of physical restraints when starting the model, because if you become dependent upon it, one day you might forget to put it on.

Posted by Martin Harris on 03/05/2018 10:50:27:

At what point do I say that pilot A is allowed to use a switched safety system and pilot B is not considered capable?

I do concede that this is a potentially awkward situation, but not one that can't be overcome. How about asking the pilot to restrain the model, connect the battery and then demonstrate the use of the lock? No more onerous than range checks or fail-safe checks, surely?

Edited By The Wright Stuff on 03/05/2018 11:15:01

[Mike Blandford]

Posted by Martin Harris on 03/05/2018 10:50:27:

. . .sticky throttle systems are brilliant but rely on relatively complex programming - not everyone has the ability to program them or even follow a set of instructions.

Which is why, on ersky9x firmware, I have a "Safety switch" menu where you just select the "Sticky" type and set the controlling switch and output value for the throttle channel, no complex programming.

Mike

[Martin Harris - Moderator]

You won't hear any argument from me about the benefits of a safety switch - I use them myself, strongly advocate their use and often program them for other members. In the case of your theoretical error then it's overlaid a very useful layer of safety to cover what I feel is the sort of mistake anyone can make.

I'm not sure that I've stated that electronic safeguards increase the likelihood of accidents overall but I do believe that reliance can introduce situations where accidents can happen because of a level of unintended complacency or assumptions. I simply consider it better to overlay that extra layer of safety onto a basic safe practice.

It's an interesting (and I feel constructive) debate because we are all arguing from a perspective of increasing safety but with some fundamental differences in the approach to providing it. I'm sure we could continue the debate ad nauseam but I think I've made all the points that I want to so (to John Stones' undoubted relief!) I'll bow out of this now...