Throttle cut button - why the bad press?

[The Wright Stuff]

Just musing about this while reading the thread on safety plugs, but i though I would start a separate conversation to avoid diverting that one.

I fly both electric and I.C.

If I start my I.C. models, then all I have to do to chop off fingers is to accidentally catch them in the arc of the propeller. One step from disaster.

If I arm my electric model, then I have to accidentally do two things to cut off fingers. First, I must accidentally knock the throttle to open, THEN I have to accidentally put my fingers in the arc of the propeller. Two steps from disaster.

So I use the throttle cut switch on my transmitter, to prevent the throttle from operating the motor. Now I have to accidentally do three things to cut off fingers. First, I must accidentally cancel the throttle cut (or accept it might fail), THEN I must accidentally knock the throttle to open, THEN I have to accidentally put my fingers in the arc of the propeller. Three steps from disaster.

My actual practice is to set up the throttle EPA such that the ESC won't even arm until the throttle cut is set (i.e. the throttle lever won't go back far enough). Now I have to accidentally do four things to cut off fingers. First, I must accidentally operate the throttle cut (or accept it might fail), THEN (having not heard the ESC beeps) I must accidentally unset it again, THEN I must accidentally knock the throttle to open, THEN I have to accidentally put my fingers in the arc of the propeller. Four steps from disaster.

So on that basis, for heaven's sake, how is operating an I.C. model even legal anymore!

I'm being flippant, of course, and I totally accept arguments that say that Tx operated safety features are prone to human error, throttle reversed, wrong model, etc, but for a set-up, tried and tested model, what is wrong with using the throttle cut function to take the model from the arming area of the pits, to the flight line? Yes, I could forget to set it correctly, but I could forget to remove the safety plug, too.

Why is the throttle cut function treated with such distain? Has it ever failed?

[Martin Harris - Moderator]

I have absolutely no argument that you're adding layers of safety and always recommend setting a throttle cut (I would call it disarming) switch. I have one (with a physically locking switch which is checked on power up and will not allow the transmitter to activate unless in the safe position) on every electric powered model I own.

However, the first and most reliable method of avoiding injury is to NEVER get any part of your anatomy in the prop arc - or its potential location - when a battery is connected or being connected. In fact, if you were really serious, you could even extend that to when the battery wasn't even near the model as in the case of never pointing a gun at anyone, loaded or not. This has to be the message we need to get across to modellers new (and often with much more difficulty) old.

The human being has an almost unlimited potential to cause itself harm through carelessness, thoughtlessness, reckless behaviour and sheer bad luck - whether or not a throttle cut has ever failed to protect a modeller is immaterial! However, on the balance of probability, it's almost certain that disarming switches will have saved many of us from injury or a nasty moment.

Edited By Martin Harris on 02/05/2018 13:23:34

[Jon H]

I am not exactly sure i understand the question. Are we talking ic or electric?

also are we mixing up throttle hold and throttle cut? In the case of ic throttle cut does just that and stops the engine. you cant cut it if it was never running so i dont think it applies to leccy. with either throttle hold renders the throttle stick inactive.

From a safety point of view its probably better to have a throttle hold active when carrying a model and we recommend this at my club irrespective of powerplant. Certainly i used to do this with my electric heli's. Electric models remain powered down completely and ic models are held at idle so they dont rev up if you bash the throttle as you bend down to put it back on the floor.

Edited By Jon - Laser Engines on 02/05/2018 13:41:06

[Mark Agate]

Once your system is armed, it's important that you can throttle down to minimum then throttle back up without having to re-arm, and expect the motor to restart. If it latched into the off state during flight you could have an unintended deadstick situation.
So now you've landed: you walk over to the plane and bend over to pick it up. As you do so, your throttle stick gets knocked, kicking the motor back into life just as your hand goes through the propeller arc. We are not as many steps away from an accident as we would like to be!
It's important to re-engage the throttle cut switch before retrieving the model. Unfortunately this is another conscious step required to ensure safety. An alternative solution which I have tried is to make the motor spin at idle speed as soon as the throttle cut is disengaged, so it acts more like an IC engine (I think I'm much less likely to stick my hand into the arc of a prop if it's already spinning). There is a slightly increased risk of accident if the switch has been left in the wrong state when the system is energised, though I think almost all ESCs won't start immediately in this situation.

[john stones 1 - Moderator]

Posted by Martin Harris on 02/05/2018 13:15:54:

I have absolutely no argument that you're adding layers of safety and always recommend setting a throttle cut (I would call it disarming) switch. I have one (with a physically locking switch which is checked on power up and will not allow the transmitter to activate unless in the safe position) on every electric powered model I own.

However, the first and most reliable method of avoiding injury is to NEVER get any part of your anatomy in the prop arc - or its potential location - when a battery is connected or being connected. In fact, if you were really serious, you could even extend that to when the battery wasn't even near the model as in the case of never pointing a gun at anyone, loaded or not. This has to be the message we need to get across to modellers new (and often with much more difficulty) old.

The human being has an almost unlimited potential to cause itself harm through carelessness, thoughtlessness, reckless behaviour and sheer bad luck - whether or not a throttle cut has ever failed to protect a modeller is immaterial! However, on the balance of probability, it's almost certain that disarming switches will have saved many of us from injury or a nasty moment.

Edited By Martin Harris on 02/05/2018 13:23:34

Tis a great advert for said human being to be allowed to fly his/her toys Martin.

My thoughts..anything and everything gets anaylised to death.

[The Wright Stuff]

Posted by Jon - Laser Engines on 02/05/2018 13:40:36:

I am not exactly sure i understand the question. Are we talking ic or electric?

also are we mixing up throttle hold and throttle cut? In the case of ic throttle cut does just that and stops the engine. you cant cut it if it was never running so i dont think it applies to leccy. with either throttle hold renders the throttle stick inactive.

From a safety point of view its probably better to have a throttle hold active when carrying a model and we recommend this at my club irrespective of powerplant. Certainly i used to do this with my electric heli's. Electric models remain powered down completely and ic models are held at idle so they dont rev up if you bash the throttle as you bend down to put it back on the floor.

Edited By Jon - Laser Engines on 02/05/2018 13:41:06

Hi Jon, yes, by 'throttle cut' I mean throttle hold. The name probably varies from manufacturer to manufacturer, but on mine (Futaba) the button is called 'throttle cut' whether in ESC mode or IC mode...

The question is really: "Why is the throttle-hold facility largely not credited as a safety feature?" as in the attitude: "models have to be treated as live even if the throttle-hold is activated".

Now, I'm not having disregard for safety. I'm all for belt and braces, but it seems to me that when you've got four belts and three sets of braces, then sewed your shirt to your trousers, you can probably be satisfied that you've sufficiently mitigated the risk!

Edited By The Wright Stuff on 02/05/2018 13:57:12

[Biggles' Elder Brother - Moderator]

In my view, I think you have seen your answer here TWS. So many clubs make unnecessary regulations and state that a Throttle disarm is not enough, no matter how many interlocks are on it,.....because their committees are dominated by those who don't understand what you are talking about or the programming techniques you may employ to create extra layers of safety.

Twas ever thus sadly.

Just my view, based on my experience.

BEB

Edited By Biggles' Elder Brother - Moderator on 02/05/2018 14:03:02

[The Wright Stuff]

Posted by Mark Agate on 02/05/2018 13:41:10:

So now you've landed: you walk over to the plane and bend over to pick it up. As you do so, your throttle stick gets knocked, kicking the motor back into life just as your hand goes through the propeller arc. We are not as many steps away from an accident as we would like to be!
It's important to re-engage the throttle cut switch before retrieving the model. Unfortunately this is another conscious step required to ensure safety. 

Interesting, Mark. I am now in the habit of engaging throttle-hold as soon as the model has stopped, after landing. In fact, it's so engrained that it's subconscious. On occasion, I have even tried to taxi back to the pits, and found the motor not to be working, then realised I had engaged throttle-hold without even realising I'd done it!

Edited By The Wright Stuff on 02/05/2018 14:12:14

[Martin Harris - Moderator]

I've found the same thing, but therein lies the rub...when I'm flying my own models, they are intrinsically safe within the limitations of switch reliability and microprocessor glitches. However, I know that I'm not infallible, something might distract me or I could have a "blonde" moment (even though my dark brown hair has turned almost entirely white) - and then over reliance on a switched safety mode puts me in more danger than if I didn't have any at all!

I also fly many other members' models and am aware that I would be at the mercy of other people's programming of switching requirements should I develop sloppy handling methods.

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.

John, I don't think it hurts to point out unsafe methods of handling our models where appropriate - it certainly does hurt if you get it wrong!

P.S.

Posted by The Wright Stuff on 02/05/2018 13:53:36:

Now, I'm not having disregard for safety. I'm all for belt and braces, but it seems to me that when you've got four belts and three sets of braces, then sewed your shirt to your trousers, you can probably be satisfied that you've sufficiently mitigated the risk!

Mitigated the risk?  Whatever you do don't have a dodgy curry the night before flying! 

 

Edited By Martin Harris on 02/05/2018 14:54:47

[john stones 1 - Moderator]

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.

[Martin Harris - Moderator]

I wasn't taking it personally John. Good rules are only an extension of common sense - I'd like to think those we do have in our club reflect this.

[Chris Walby]

I am not sure dictating layers and layers of procedural sequences improves safety, humans will either consciously or unconsciously skip or avoid them.

Martin's point of good practice is IMO the most pragmatic and successful strategy, keep it simple and treat it as if its live when the battery is connected.

Throttle hold/cut has its place, but I have two models that if the battery is connected with the TX hold switch deployed the ESC sets this an the end point. If you take the hold off the prop rotates slowly so the model must be armed with the throttle hold off.

It would be interesting to see the BMFA statistics involving prop accidents to see if they are electric or IC (not very meaningful if IC owners are a minority of operators!). Perhaps the ESC should be emitting a warning sound/message that it is powered up...and may start by operator error at any time.

How many clubs test throttle hold/cut as part of their pre maiden inspection on electric models?

Does anyone know if there has been an RX or ESC failure resulting in the motor starting/running?

PS I hope it stops raining soon

[Biggles' Elder Brother - Moderator]

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 happy you understand Martin, but many safety offcers - incuding two I am closely involved with - would see putting a Y-lead on the aileron output as the high of sophistication!

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

[The Wright Stuff]

Posted by Chris Walby on 02/05/2018 15:35:11:

Martin's point of good practice is IMO the most pragmatic and successful strategy, keep it simple and treat it as if its live when the battery is connected.

But this is entirely the point I'm making. My club insists that the battery is not connected until you are at the flight line, whilst being very happy for people to walk around the pits carrying I.C. models with the engines running. It's the disparity that concerns me.

If this means lying on the floor on the flight line fiddling with battery connectors, while surrounded by other pilots taking off and landing, then personally I think that puts me in MORE danger, not less.

[The Wright Stuff]

Posted by Chris Walby on 02/05/2018 15:35:11:

It would be interesting to see the BMFA statistics involving prop accidents to see if they are electric or IC (not very meaningful if IC owners are a minority of operators!). 

Maybe we could do a poll on this site:

• I fly mainly electric and I have never had a propeller related accident requiring hospital treatment resulting from an electric model.

 

• I fly mainly electric and I have had a propeller related accident requiring hospital treatment resulting from an electric model.

 

• I fly mainly I.C. and I have never had a propeller related accident requiring hospital treatment resulting from an I.C. model.

 

• I fly mainly I.C. and I have had a propeller related accident requiring hospital treatment resulting from an I.C. model.

Edited By The Wright Stuff on 02/05/2018 16:17:52

[john stones 1 - Moderator]

I've never had any sort of propeller related accident, been reduced to tears by the price of large carbon ones though.

[Peter Christy]

As a long-time heli flyer, I've always treated "throttle-cut" and "throttle hold" as completely different functions. With an IC helicopter, "throttle hold" is usually set to tickover, allowing auto-rotations to be practiced. Even electric helis will often set the "throttle hold" to a low RPM setting in order to avoid the slow spool up that some ESCs have to prevent shock-stripping the gears. A slow spool up can be embarrassing when bailing out of a dodgy auto-rotation....!

"Throttle cut" is usually reserved to completely kill the engine and stop the model doing the chicken dance following the aforementioned dodgy auto-rotation!

I've carried these over to my fixed-wing models too, for more or less the same reasons. "Throttle hold" to avoid accidentally knocking the throttle stick whilst carrying a model, and "throttle cut" to kill it after landing. I usually also set "Throttle cut" as a pre-requisite on powering up an electric model. This is because an electric motor develops maximum torque when stalled. An IC engine stalls when, er, stalled!

If you get your fingers in a *small* IC engine, you'll probably end up with some nasty cuts, but the engine will probably stop before doing any real damage. An electric motor will keep chopping all the harder, the more you try and stall it.

Either way, its a good idea to keep the extremes of your anatomy away from whirling machinery!

--

Pete

[Biggles' Elder Brother - Moderator]

Posted by The Wright Stuff on 02/05/2018 16:02:45:

Posted by Chris Walby on 02/05/2018 15:35:11:

Martin's point of good practice is IMO the most pragmatic and successful strategy, keep it simple and treat it as if its live when the battery is connected.

But this is entirely the point I'm making. My club insists that the battery is not connected until you are at the flight line, whilst being very happy for people to walk around the pits carrying I.C. models with the engines running. It's the disparity that concerns me.

If this means lying on the floor on the flight line fiddling with battery connectors, while surrounded by other pilots taking off and landing, then personally I think that puts me in MORE danger, not less.

Hear hear!

BEB

[Biggles' Elder Brother - Moderator]

Posted by Peter Christy on 02/05/2018 16:36:18:c model. This is because an electric motor develops

Either way, its a good idea to keep the extremes of your anatomy away from whirling machinery!

--

Pete

Now there's a wise man!

BEB

[john stones 1 - Moderator]

3 Prop incidents that where bad I've witnessed.

1. Gentleman started engine up, all restrained, all gizmos in order, he stood up and slipped over, hand in prop, hospital job.

2. Gentleman launching his grandsons i.c delta, rear engine, bad launch, hand in prop, end of finger gone.

3. 30cc petrol job, restrained, helper stood over model, starter pushed model back when applied, he let go, it came forwards, hand in prop, bad one.

[Denis Watkins]

Roll on the good weather this week, to get us all out in the fresh air, to clear our heads.

[Nigel R]

I think Peter C covers it rather succintly - never, ever, stick anything through the prop arc.

Our club has almost no safety rules specifically regarding electrics. Only one prop accident reported in the last few years, on a large glow whilst starting it. And, the only IC specific rule is, they have to be restrained while starting them.

The prop based injuries I've had, and all of those few being fortunately small, have all been from hand starting glow motors (except one - while tweaking the needle on that damn 0.49 - the needle was really very close to the prop - when I was younger, that has done made me very cautious about props ever since). They have all been an unexpected kick, right way or wrong way.

[Jon H]

Posted by The Wright Stuff on 02/05/2018 16:02:45:

But this is entirely the point I'm making. My club insists that the battery is not connected until you are at the flight line

This strikes me as a bit daft. As long as you have some sort of throttle hold (cut, whatever) that renders the throttle stick redundant while you walk then that is surely enough. My club dont allow power checks on our runway any more as people would dance around out there for a while and it was considered a bad idea. As our field allows it, we recommend people taxi off the far end of the runway and retrieve their model from a dead space we have between the strip and pits. we dont go mad about it though. We recommend throttle hold is used on all aircraft but its not written in stone. We do require all models to be restrained as a few leccy models have escaped for one reason or another.

As you guys can probably appreciate i deal with more rotating blades than most and so far have avoided significant injury. When i have clipped a knuckle or whatever the reason has almost always been complacency. Even with all the safeguards in the world there is no substitute for simply paying attention to what you are doing and keeping anything you dont wish to chop outside of the propeller arc.

[Toni Reynaud]

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.

[Bob Cotsford]

Worst I've had in a good many years occured last year. It was after starting an OS120 Surpass powered model while kneeling on the ground, as I stood up I wobbled and put out an arm to balance myself - pure reaction. A bad one as I caught my fingertips on the tips of the prop which was just ticking over. Apart from the shock of having two fingernails split lengthways and some loss of blood I got off quite lightly. I now use a model stand so that I start them up from a standing position. It also means no-one has to lift one of my models off the ground with the engine running (for some odd reason clubmates get nervous if I move running models myself )