We often see the same problem over and over, to save time repeating the same answer, here is a compilation of issues, with cause and solution. Please let me know if there is a common problem you see people ask all the time, so we can add it to the list.
#1 - Motor twitching when not armed
Caused: When your quad is not armed, your FC would still send a signal to the ESC's, i.e. Min_command. Even at 1000 (the default value), it might still trigger the motors to run at extremely low RPM. This signal isn't high enough though (at 1000), so the motors only twitch, but do no spin.
Solution: Lower Min_Command by step of 10 until the motor stop twitching, Min_Command is at 1000 by default, and you would probably end up somewhere around 990-950.
#2 - Why does one of my motors get really really hot?
Solution: Check if your motor screws are too long and touching motor winding.
#3 - My quadcopter is acting odd (vibration, twitch, rpm raising, etc.) when it's armed, but still sitting on a level surface without propellers
Cause: Arming the quad in any mode - rate, level, etc. will engage the PID controller. The PID controller will attempt to stabilize but without propellers the behavior will be unpredictable - exhibiting many of the reported symptoms, most likely twitching, jerking, apparent increasing of throttle.
Diagnose: Check motor direction and order first. Make sure your quad arms and disarms correctly. Test that failsafe is configured (best failsafe is a quick disarm). Put some propellers on the craft (again check orientation) and try hovering in an open and safe area. Chances are the craft will fly fine, if so tuning and fun are next.
Solution: If craft still jerks or twitches, check for obvious mechanical problems - bent shafts or bells, motor mounts, esc solders. Next most likely cause is the gyro - some are very sensitive to vibrations (MPU6500), in these case soft mounting might help, or a better FC altogether. Many retailers sell rubber mounting screws now that are almost direct replacement to the plastic FC mounts. (http://www.getfpv.com/m3-anti-vibration-...-of-6.html) Anything beyond that I would not consider a common problem and best is to provide detailed description and ask for expert help.
* Credit to Jordan Marinov
#4 - My quad flips on take off
Diagnose and Solution:
This can be due to the following reasons:
#6 - When I arm my quad, the motors run faster and faster on the bench without propellers. What is wrong?
This is a normal behavior. In this case, the PID controller attempts to control the aircraft, but because there is no propellers so the quad isn't moving, so the motors are trying harder and harder to try to move it. Just put the props on and test fly!
#7 - bars are not moving in the receiver tab? No RX activity.
In most cases, Clean / Beta / Raceflight is not configured correctly . For example, the "Serial RX" option must be selected for a FrSky XSR in the Ports tab, and "S-Bus" in the "Receiver" menu in the "Receiver" menu. The servo travel (visible in the "Receiver" tab) must also be set correctly.
#8 - Why does my cop drift when hovering?
1. TX sticks need trimming. Use the trim of your transmitter to make sure your sticks end points are 1000 and 2000, and centres at exactly 1500, if the value jumps around 1500, you can consider setting "deadband" for this axis.
2. If this is horizon or angle mode, your ACC might not have calibrated properly. Also it's possible to trim the ACC if that's necessary.
#1 - Motor twitching when not armed
Caused: When your quad is not armed, your FC would still send a signal to the ESC's, i.e. Min_command. Even at 1000 (the default value), it might still trigger the motors to run at extremely low RPM. This signal isn't high enough though (at 1000), so the motors only twitch, but do no spin.
Solution: Lower Min_Command by step of 10 until the motor stop twitching, Min_Command is at 1000 by default, and you would probably end up somewhere around 990-950.
#2 - Why does one of my motors get really really hot?
Solution: Check if your motor screws are too long and touching motor winding.
#3 - My quadcopter is acting odd (vibration, twitch, rpm raising, etc.) when it's armed, but still sitting on a level surface without propellers
Cause: Arming the quad in any mode - rate, level, etc. will engage the PID controller. The PID controller will attempt to stabilize but without propellers the behavior will be unpredictable - exhibiting many of the reported symptoms, most likely twitching, jerking, apparent increasing of throttle.
Diagnose: Check motor direction and order first. Make sure your quad arms and disarms correctly. Test that failsafe is configured (best failsafe is a quick disarm). Put some propellers on the craft (again check orientation) and try hovering in an open and safe area. Chances are the craft will fly fine, if so tuning and fun are next.
Solution: If craft still jerks or twitches, check for obvious mechanical problems - bent shafts or bells, motor mounts, esc solders. Next most likely cause is the gyro - some are very sensitive to vibrations (MPU6500), in these case soft mounting might help, or a better FC altogether. Many retailers sell rubber mounting screws now that are almost direct replacement to the plastic FC mounts. (http://www.getfpv.com/m3-anti-vibration-...-of-6.html) Anything beyond that I would not consider a common problem and best is to provide detailed description and ask for expert help.
* Credit to Jordan Marinov
#4 - My quad flips on take off
Diagnose and Solution:
- Check if your board is rotated around yaw axis, and if so please set the correct yaw offset in the software
- Check if the rotation of propellers are correctly
- Check if the ESC signal leads are connected in the correct motor pins on the flight controller, and you didn't connect them the wrong order
This can be due to the following reasons:
- Incompatible ESC protocol
- Cold soldering point
- A phase of the motor is broken
- Motor screws are too long and touch the motor windings
- Damaged motor
- Incorrect motor timing is set, usually the manufacturer gives a suitable timing. Desync by wrong "Demag" setting in BLHeli , test a higher value.
#6 - When I arm my quad, the motors run faster and faster on the bench without propellers. What is wrong?
This is a normal behavior. In this case, the PID controller attempts to control the aircraft, but because there is no propellers so the quad isn't moving, so the motors are trying harder and harder to try to move it. Just put the props on and test fly!
#7 - bars are not moving in the receiver tab? No RX activity.
- Receiver is connected incorrectly, eg soldered to the wrong pins, short circuit or provided wrong voltage
- Clean / Beta / Raceflight is configured incorrectly
In most cases, Clean / Beta / Raceflight is not configured correctly . For example, the "Serial RX" option must be selected for a FrSky XSR in the Ports tab, and "S-Bus" in the "Receiver" menu in the "Receiver" menu. The servo travel (visible in the "Receiver" tab) must also be set correctly.
#8 - Why does my cop drift when hovering?
1. TX sticks need trimming. Use the trim of your transmitter to make sure your sticks end points are 1000 and 2000, and centres at exactly 1500, if the value jumps around 1500, you can consider setting "deadband" for this axis.
2. If this is horizon or angle mode, your ACC might not have calibrated properly. Also it's possible to trim the ACC if that's necessary.