Troubleshooting

Getting a multicopter to fly can be tricky, especially for those who are new to the world of RC and micro controllers. There are hundreds of variables that could stop your machine from flying. Successful troubleshooting depends on a systematic approach, eliminating each potential source of trouble until the problem is resolved.

The information here has been compiled from over two hundred different "my multicopter won't fly" situations, and is presented with the most common causes at the top.

General Troubleshooting - Applies to all multicopters

Does Not ARM

This is commonly due to the Stick values not exceeding MINCHECK and MAXCHECK. The defaults are 1100 and 1900. The Radio TX setup (see the User's Manual for the Radio you are using) is used to adjust the stick End Point values, typically called stick Gain. The recommended values are to have the sticks go from 1000 to 2000usec but not further. These values are displayed in the MultiWiiconf.exe or WinGui.exe. Also ensure the stick values increase when moving the sticks to the right and up. If they do not then reverse the stick in the radio setup.

Motors

Are your motors spinning in the correct direction? If a motor is spinning in the wrong direction, all you need to do is reverse any two of the 3 ESC -> Motor wires. This will reverse its direction.

Are the ESCs plugged into the correct pins on the MWC board. Re-check the motor direction and signal name diagram for the type of multirotor and the MWC you have.

Props

Do you have a clockwise prop on each clockwise motor, and a counter clockwise prop on each counter clockwise motor? Multicopters use two different types of props, clockwise (also known as Right hand, or Right, or R), and counter clockwise (also known as Left hand, or Left, or L).

A motor rotating clockwise needs a clockwise prop, and one rotating counter clockwise needs a counter clockwise prop.

Additionally, the props must be installed the correct way up. That means the printed/embossed numbers need to be facing up, not down.

ESCs

There are a number of common ESC related problems. ESC calibration is the most common. In order for a multicopter to achieve stable flight, the ESC throttle ranges need to be calibrated so that they are all the same. The procedure for calibrating ESCs is usually included in the ESC manual, but it is essentially the same for all common ESCs, and can be found here: ESC Calibration.

Some ESCs are programmable. For those ESCs, it is important to set the timing to Medium. The default setting (often Low) does not achieve good results with most motors.

It is important to remember that each ESC must be connected to the correct output pin on the multiwii, otherwise the machine won't fly.

Vibration

Vibration is a very common source of problems for beginners. If there is too much vibration being transmitted to the gyro, the signal to noise ratio on the gyro signal is too great for the multiwii to be able to make use of the signal.

The key to reducing vibration is to have a very stiff frame, and to couple the multiwii controller to it just the right amount. Frames made of aluminium, fibreglass and carbon fibre are generally much less prone to vibration than those made of injection moulded plastic or Lexan.

Coupling the multiwii to the frame is very important. The coupling needs to be sufficient for the gyro to be able to sense small movements of the frame, but not so strong that all of the vibrations created by the motors are transmitted to the gyro. Double sided foam tape is a very good way of achieving this, as are soft silicone grommets.

Too little coupling, such as when using rubber bands or springs, can result in the controller oscillating too much, and does not generally work well.

Another important way of reducing vibration is to reduce the amount of vibration generated at the motors. This is done by balancing the props, and ensuring the motor shaft is straight.

Motor Balancing

Possible balancing material:

• Tape
• Zip ties
• Nail Polish

• spin up only that motor with no prop/adapter/collets etc to 50% throttle.
• spin down and add tape any where on the motor bell.
• spin up again and see if it is better or worse.
• move it in 1/8in increments and find the perfect spot.
• add more tape to that spot if moving it around doesn't help any more and it still sounds bad.

Also, you could use an phone app that senses vibrations or the MWC GUI acceleration graph to see if the motor vibrations are better or worse.

Propeller Balancing

Possible tools:

• a real prop balancer
• your motors

The prop balancer should come with directions, but, here is how it goes basically:

• Put the balancing shaft into the prop and tighten it down.
• Insert the prop/shaft into the balancer
• Spin the prop with your hand and then wait for it to stop. mark this side with a barker. Do it again and see if it lands on the same side. To be extra sure, put the marked side oft he prop pointing up and see if it falls.
• Add some tape so that it bends around the leading edge(so it wont come off when spinning) of the other prop blade (the one not marked).
• spin the prop on the balancer again to see where it stops. if the marked side is down, add more tape to the other side. if the non marked side is down, remove tape form that side.
• Repeat above till it is pretty balanced.

Do a similar method if you use your motors to do this. Put the props on and listen for the least vibrations or use your phone or the MWC GUI for the accelerometer graphs.

Power System

In order for the machine to fly, it needs to be able to deliver enough power to the motors, and the motors need to be able to use this power to move a sufficiently large volume of air.

The electrical connections between battery, ESC and motors are very important. These need to be well soldered, and to use sufficiently large wire. This is especially important for larger multis, weighing over 1kg.

The motors need to be well matched to the machine's weight. Around 500W of maximum motor output per kg of total machine weight is a good starting point.

The motor speed needs to be well matched to the props used. Larger props need larger, slower motors.

A mismatch between the power components can easily result in a machine that will not fly. Ecalc is an excellent resource for getting a rough idea of whether your machine can fly.

Drifts in Yaw, Roll or Pitch

Ensure the stick center values are exactly 1500. This is adjusted in the Radio TX's setup and commonly called 'sub-trim'.

Failsafe

For proper detection of failsafe condition, the endpoints of the first 4 channels must be set to be within the 1000, 2000 range on the TX. Not following this will likely lead to false failsafe alarms.