RC Helicopter Electrostatic Discharges and Grounding

Introduction

The T-Rex 500, and many other similar helicopters use a tail pulley belt drive to power the rear rotors of the helicopter. This can act as a mini Van De-Graff generator though, with static building up in the tail boom. The problem of static discharge comes about due to the fact that the tail boom is not electrically grounded to the frame. It clamps in place with a plastic tail boom support. So the static can build up to high levels on one part of the RC helicopter, with no way of dissipating. When it gets to a certain level it will arc to the nearest conductive surface, interfering dangerously with the radio control electronics on the aircraft and other low voltage RC systems. This can and does cause "glitches" in the control system of the helicopter, either shutting down the receiver momentarily, or sending random control commands to the servos, (throttle, rudder, cyclic etc) resulting in a crash.

That is not to say everyone will experience this problem. It only affects a very small minority. Also, only certain receivers behave badly when receiving an electrostatic discharge, most problems have been reported with Spektrum receivers, but issues have also been seen in most other makes of receiver including Futaba and Airtronics. Luckily, it is a very easy problem to fix, and some easy preventative measures will save you an expensive repair bill at you local model shop.

Points to Consider

A few points to consider, this is only for RC helicopter tails with a belt drive system, torque tubes do not suffer from this. Carbon fiber is also conductive, so it will occur even with a carbon tail boom on your RC helicopter. This can affect any helicopter, and not just the T-Rex range, the same is true for the receiver, it can occur in any brand of receiver. I will also repeat the fact that it is not 100% certain that you will ever experience this issue, but it is better to be safe than sorry, and especially as it is very easy to fix indeed.

If you have a Spektrum receiver, namely the 6100, or 7000 series, make sure it has "Quick Connect", this was provided by the manufacturer after the first issues started showing there ugly heads. Before this it would take the receiver several seconds to restart after a interference/discharge event. With quick connect, this is reduced to a fraction of a second. It will also give a flashing light on the receiver if this has occurred during flight, as a warning to the problem. To test to see if you have it, remove the power to the radio receiver, and re-connect it. The orange receiver signal light should now be flashing. Congratulations, you have quick connect. This goes a long way to saving the helicopter if a problem occurs. If not, the receiver will take several seconds to start up again and regain a signal. If this is the case, contact Horizon Hobby UK, and they will replace it free of charge.

The Easy, and Very Effective Solution

So, on to the solutions. The quickest and cheapest is to lubricate the tail belt with silicon spray. Do this whilst running the belt manually to get a good coating over the entire length. Repeat every few weeks. This has been shown to solve most static discharge problems completely on helicopters that were showing signs of electrostatic discharges. As it prevents static from building up in the tail boom of the helicopter. A anti-static spray, such as a common furniture polish can also be used, but it is more ideal to use silicon spray. This will also help with the day to day running of the tail and performance. DO NOT use WD40, this has been shown to damage the tail belt over time.

It is also a good idea to place the receiver on the bottom shelf of the helicopter electronics tray, or underneath the tray. Essentially finding a good balance between distances from the helicopter tail mount, and ESC. As it is always recommended to keep high voltage helicopter equipment (Motor, ESC etc) away from low voltage (Receiver, gyro, telemetry systems) radio equipment, to prevent interference from these sources to. It is to be noted as well, some research, and burnt aerial tips, demonstrate that a arc can occur between the frame and the receiver antennas. Keep them from touching the frame to be safe.

The More In-Depth, and Complete Solution

The main solution that i demonstrate here, is to manually ground the helicopters tail to the frame. The same for the ESC, grounding it onto the frame to reduce the EMI noise. What you want to do is scrap away a little area of the coating on the tail boom, it is anodized on the metal, and glossy on the carbon tail booms. Once the inner surface is exposed, place the exposed ends of a insulated wire onto this scrapped spot, and secure it in place. Then run this, and pass it via one of the screws going into the plastic tail holder. This will now earth the tail to the frame, and for the majority of cases, this is more than sufficient to protect from static events in your helicopter.

To go a little further, and make sure the whole helicopter is at the same potential, continue this wire to the screw going into the motor mount, and then on to the negative battery lead. I show the wires on the outside of the frame for easy viewing, but they can be neatly tucked away, as to hide there view on the helicopters frame. But be careful, as now if a positive LiPo battery lead or cable touches the frame it will cause a short circuit over the helicopter. Some people don't like doing this, but it has been shown to help. Now any interference from the motor and ESC will be dispersed into the frame of the aircraft, and the same for any static build up in the tail. Any static problems at this stage should be well and truly gone, and you can get on with enjoying your RC helicopter without worries of interference problems.

Happy Flying

Lastly some people confuse brown-outs with static discharges. A brown out is where the receiver temporarily does not have enough power to all of the required systems, this can be fixed by making sure enough power is available, for the required electronics, and setting the BEC/ESC to the correct and sufficient output voltage. A static discharge will not cause this effect, it is where interference is produced inside the receiver by the extremely large voltage now passing over it, causing the internal circuits to send out incorrect signals to the control surfaces, or shutting it down completely, putting the RC helicopter in great risk of damage. This is also known as "Glitching".

I hope you have found this article useful, remember just a few minutes work can save your pride an joy from a potential crash. At the very least, spray your helicopters tail belt with silicon spray. However, for five more minutes work, you can make a permanent fix, and fly with a clean conscience!