Quadcopter takesoff eventhough the transmitter is turned off

[Raja234]

helo rc india im using apm 2.8 flight controller with q450 glass fiber quadcopter 450mm frame and 2200kv brushless motor

i've just armed my quad and slowly gave throttle and disarmed it within 2min and turned off my transmitter (fsi6 flysky) bt suddenly my quad takeoff gradually without i'm giving trottle???!! i can't understand the problem

Note:my transmitter is new one and failsafe is turned on and at that time my quad was in stabilize mode

[Balakrishna Reddy]

Precautions to be taken while handling:
1. One should turn ON the receiver only after tx is turned ON.
2. One should turn OFF the receiver from battery and then turn OFF the tx. Keep these things in mind next time when you do things.

The above problem could be one of the catastrophe.
Check if the failsafe is turned ON in the APM and what it is doing during fail safe? Is it in RTL? I don't know if it goes to RTL after disarming. I only think it goes into RTL mode when failsafe is triggered when ARMED.