Throttle Safety Switch - Throttle Cut - Why do I need it?
If you have ever seen someone struck by a prop, it’s not pretty.
If you do get struck by a prop you might be lucky and get away with a few stitches, a scar, and a medical bill. The other end of the spectrum is death or serious debilitating injuries. We all know that large models can do serious harm, however, we don’t tend to be as nervous about the bulk of electric-powered models. We see them as less dangerous than glow or gas-powered models however this is not correct. A glow or gas engine cannot start itself and so if you bump the throttle, very little happens. Bump the throttle on an electric aircraft with the battery connected and the propeller will start spinning. Propellers on gas engines tend to be thicker blades with a thicker leading edge however electric props tend to be quite thin. A thick prop is not easily broken allowing it to cut or tear deep into skin or flesh and even breaking bones along the way until the motor stops. Thin props are more like spinning knives, meaning the propeller can make a large number of lacerations until the motor stops or the prop breaks. Either scenario is something we never hope to witness or have happened to us, but there is something we can do about it.
Why do I need Throttle Cut?
Flying RC aircraft comes with some inherent risk. In actual fact, everything we do comes with some level of risk that we intentionally manage and mitigate. In a car, we make sure our brakes are functioning and our tires have tread. We take care not to speed or go too fast around a corner. Flying is similar in that it can be as safe or dangerous as you make it. A few little changes are all can take to remove a lot of unnecessary risks to you and those around you. No one plans to lose a hand, finger, or limb, but it happens. A safety switch is a bit like an insurance policy in that you’ll only ever appreciate having one when it saves you from a disaster. The whole idea of the throttle cut is that it’s effective and simple. Sometimes it the simplest of changes that are the most effective.
What can we do?
Many people choose to set up a throttle cut on their radio so that the motor cannot start even if the throttle is moved accidentally. There are of course other safety options such as ones that include arming switches that energize after plugging the battery into the ESC. The most popular is, of course, the throttle cut function enabled in the transmitter as it requires no additional hardware and can be set up and deployed across all of your models quickly. The only prerequisites for a transmitter based throttle cut are that the radio has an assignable 2 position switch and the radio have the functionality to allow it.
Safety is no accident
Never a truer word was spoken. Plenty of things in RC can go wrong and if you have your wits about you, you might not get bitten. If you let Murphy run things, then anything can go wrong. I’m going to show you want can go wrong and the seriousness of believing these are simply toys and no great concern is warranted. Wrong. They are capable of killing you instantly and indiscriminately and if you’re lucky enough to just receive a prop strike you may be happy with permanent disability or disfigurement. Below is a list of some of the scenarios that could and have happened and it reinforces why safety and precaution are essential.
- Young Girl Killed By RC Plane A young family was walking through a park when the young girl was struck on the head by a model aircraft. The aircraft was said to have a 5ft wingspan and by all reports lost control and struck the young girl causing severe injuries that should not recover from. Although medical treatment was received within minutes and despite the efforts of medics, she died from her injuries a few hours later. To read more on this story, click
- Toddler Loses Eyesight An 18-month-old boy lost an eye after being struck by a drone flown by a family friend. The toddler's eye was sliced in half by a propeller permanently damaging the eye, The toddler will need several operations before he can have a prosthetic eye fitted. Full story
Setup Example
I have a Taranis 9XD and so I’m going to take you through the setup procedure to enable not only a throttle cut but also ensure that the throttle cannot arm by mistake. Ideally, the throttle must only arm as a result of a deliberate act. The openTX firmware is incredibly powerful and almost anything imaginable could be programmed. Although the logic is a little tricky, if you copy the settings below as it appears then you will have a powerful throttle hold function. You may need to change the OverrideCH3 setting on the special functions page if your throttle is not on CH3. This throttle cut is the best approach because it required two separate sequences before it can arm. This means the arming is a deliberate act and less likely to be an accident. The throttle must be at the lowest position, -90 or lower, before moving the throttle arm switch into the armed position. Of course, you can physically move It, however, if the sequence is wrong it won’t arm. I’ve seen many throttle programming suggestions where the throttle can be armed simply by moving the arm switch into the armed position and cycling from 100 through -100 the throttle is now armed and outputting a signal.
