The pitch and roll angles of the quadcopter attitude are controlled by torque arising from the difference in thrust of different rotors. Rotational dynamics of the quadcopter as a rigid body is considered. The pitch and roll angles that form the quadcopter tilt angle have similar dynamics for the case of symmetric quadcopter frame, so the pitch angle is studied separately in the paper. The finite frequency identification approach is used to find the transfer function from the experimental flight data. The approach needs data, when sine wave test signals are fed to the system input. In the case of the unstable loop of the quadcopter tilt angle, the closed loop identification procedure is used where the test signal is added to the setpoint of the operating controller. As a result, a more complex model is identified than is commonly used. Moreover, the nonlinear model of the quadcopter pitch angle is considered, taking into account the translation velocity. Parameters of this model are estimated from the same experimental data using the nonlinear grey-box model parameters identification procedure. The transfer function founded from this model confirms the structure of the transfer function obtained via the finite frequency identification procedure.