Before trying your drone for the first time or if you have terrible results and you don’t know why your drone is not flyable you have to read this:
1, check if data reading in the GUI is right, put your drone on a flat surface, calibrate the sensors, do you get 0 on pitch angle and 0 on roll angle ?
2, check the data reading of your transmitter in GUI, does every channel has a value near to 1500 in the middle, lower than 1095 and higher than 1905 on extreme sides ?
3, make sure you are using LEVEL mode (for MultiWii 1.9, 2.0, 2.1) or ANGLE mode (MultiWii 2.2), the check box is on green. Do not activate GPS position hold or GPS return to home before taking off.
4, arm all the motors, confirm every motor’s rotation with this picture. If the motors run in an opposite direction you will need to do #define YAW_DIRECTION -1
5, check motor controlling, arm all the motors, rotate your drone, look if the ESC values change with your movement. For example, make your drone left side up, right side down, do the 2 motors on the right side run faster ?
6, sort your propellers, clockwise and counter clockwise, mount the right one on the right motor.
7, calibrate the ACC and GYRO after changing the battery.