System for automatic trim of aerodynamic forces is installed on the airplane to prevent mechanical overstressing of servo and flight control cables which are used by the autopilot to deflect airplane's primary flight control surfaces. The problem appears when the system for automatic trim of aerodynamic forces occasionally disconnects itself, particularly during two phases of flight, the initial climb and the final approach. As a consequence, higher forces are felt on the control column, and higher loads are acting on the whole construction of the flight controls system. We have taken a closer look at design of the flight controls system and the operation of autopilot on the CRJ 900 airplane. We have explained the connection between primary and secondary flight controls surfaces of the airplane. We have tried to figure out possible solutions on how to prevent this promblem from happening again. In the meantime we discovered the reason of this problem and it's negative impact on airplane's coordinated flight. We found three solutions, first two solutions are more simple and the third one is complex. Manual trimming of aerodynamic forces and reset of the flight controls computer are more practical and had been tested in real during a real operation of the airplane and both of them had solved a problem. The most expensive solution has not been tested, because the initiation of this solution would have to be started by the manufacturer.
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