There are many common problems new quadcopter pilots tend to ask. In this article we will try to help troubleshoot some of the common issues, some can even be avoided from happening.
How to Avoid Multicopter Technical Issues
For anyone who has experience of building quadcopters, should be familiar with all the critical parts of the machine. If not please take a look at the quadcopter hardware overview guide.
Technical hardware failure is inevitable. In this post we will discuss some hardware failures that tend to happen in a quadcopter, and how we could troubleshoot or minimize the chance of disaster from happening.
- My Quadcopter won’t arm
- Common FC issues
- ESC problems
- radio transmitter/receiver issues
- VTX, VRX, FPV related issues
My Quad Won’t Arm
Flight Controller Failure
Mini Quad flight controllers have actually been one of the most reliable components for me personally. Common issues could be:
- Cold/dry solder joints – to RX this means failsafe kicks in without losing signal (no RSSI warning), to ESC this means the quad doesn’t response to TX stick for a brief moment or just drop out of sky. This is a good example of “how not to solder“
- FC shutdown – you quad drops out of sky unexpectedly. Usually this is caused by lost power to the FC: maybe a cold solder joint or loose cable, or maybe it’s the voltage spikes in the power. Bad voltage regulator could also be the cause
- Moisture or water gets into the FC and shorts the components, causing the quadcopter to fail – try to avoid flying in the rain/snow, or above water, wet grass etc. To prevent this issue you could also apply waterproof coating on your FC or any exposed PCB in your quadcopter
The most common ESC (Electronic Speed Controller) problem might be burn-out, or even catching fire.
There are many situations where the ESCs can be burnt out.
- Overloading, i.e. motor draws more current than what’s they are rated for over a long period of time and causes overheat
- Damaging burst current during a crash
- Physical damage, e.g. hitting a rock, or struck by a spinning propeller
To avoid these problem, always stay within safe limit when picking motors and propellers combo. It would be nice to have current sensor in your quadcopter and have the current draw displayed in OSD. Make sure your PID is properly tuned, bad PID can cause vibration and excess current draw. Also make sure the ESC’s are getting good airflow.
To protect ESC’s from physical damage, many people simply put a blade of a propeller on it and wrap it with tape or zip tie.
All soldering and wiring should be kept well insulated from each other, and proper heatshrink should be used for electrical protection. For carbon fibre frames, wires should be handled with extra care as carbon fibre is conductive. They should be insulated from each other.
Radio Transmitter/Receiver Signal
When it comes to radio problems, the first thing I can think of would be loss of radio signal. These might be the causes:
- RX lost power
- Your antenna got chopped off by propellers
- RX antenna is blocked by carbon fibre frame
Also make sure there is nothing blocking between you and your aircraft. The frequency used in our radio is 2.4Ghz, while it’s has moderate penetration ability, it can easily be blocked by concretes and hills. Make sure your transmitter antenna is aligned with your receiver antennas to get the best possible signal.
It’s good to have some sort of RSSI signal strength alarm or warning. Decent radio transmitters come with this feature such as the Taranis, it shouts at you when signal strength drops below certain level so you can make a turn in time. Also make sure failsafe is setup properly on your radio receiver and flight controller.
Lastly, range check your radio if you are flying in a unfamiliar environment, “knowing one’s limit” was the wisest lesson I ever learnt.
Mini Quad Motors are generally quite robust and they don’t break easily. But since they are very exposed to crash damages, ripped wires, bent shaft or loose magnets can happen. Some would attempt to fix them but due to the technical difficulty it’s easier to just buy a new one IMO.
Hot motors aren’t a good thing: it shortens motor life and eventually the motors can burn out.
Two things tend to make motors hotter than they should:
- “Over-prop” – using propellers that are too large to handle
- Vibrations and twitching in your quadcopter, rapid change of motor RPM will cause motors to overheat
To prolong the life of motors, it’s important to keep them as cool as possible in flights. This involves tuning your PID properly, clean your power system noise with capacitors. In extreme cases where nothing seems to help, you can also consider soft mounting your FC or even motors.
Another common issue with motors are long screws. If screws are too long they could touch and short the wildings in the motor. This could cause the motor to overheat, or even burn out the motor. Here is how to determine the correct length for motor screws.
Some motors are hotter than others?
If 1 side of the motors are warmer than the other side, this usually suggest there is a problem with center of gravity (COG). For example if the back is heavier than the front, then your back motors are going to work harder to keep the craft in the air and thus get warmer. A quick fix is to shift your battery or HD camera to keep COG in the centre.
Video Transmitter/Receiver Signal
If you fly FPV, the last thing you want is to have problem with FPV system. When losing video you have absolutely no idea where the quadcopter is flying into, and this is extremely dangerous to people around. When this happens the best thing you could do is probably cutting throttle immediately, let gravity take care of the rest and crash your quad in to the ground.
Most people fly 5.8Ghz these days, and penetration ability sucks, and this is the main cause of lost of signal. Don’t expect it to work if you are flying in the wood or over the other side of the building. Trees and walls are very effective at blocking 5.8Ghz signals.
Getting jumping lines in your video during flight? It could be noise in your power and adding some capacitors could help. Also make sure your FPV gear shares a common ground (ground are connected together).
And again, range-check your equipment before you fly in a new environment.
There are endless possibility when it comes to issues in a quadcopter, if you had an unusual problem that wasn’t mentioned please let us know in the comment section. It could save someone hours to find out the problem.
Before a flight session, remember to check all of your bolts and nuts are fastened, especially the motors. After a rough landing or crash, triple check your props and frame for damages as well, do not fly with propellers with crease lines.