APPARATUS FOR IMPROVING THE LONGITUDINAL OR PITCHING STABILITY OF AIRCRAFT

The control of the longitudinal or pitching stability of aircraft is imprd by providing a corrected control characteristic for the correction adjustment drive which is interposed between the pilot operated control stick and the main control drive, for example for the blade angle adjustment in a helicopter or for the elevator adjustment in fixed wing aircraft. A control linkage (2) is connected on one end to a main control drive (4) for the elevator or rotor blade adjustment and at its other end to the control stick (1). The correction adjustment drive (3) is interposed in the control linkage (2). A displacement pickup (5) measures the control displacement of the control linkage (2) and a flight speed pickup (6) measures the flight speed. To improve the control of the longitudinal or pitching stability without having the corrected control displacements of the control stick (1) become too large, a delay circuit (7) and first differentiating circuit (8) are serially connected downstream of the displacement pickup (5). A second differentiating circuit (9) and a linear amplifier (10) are serially connected downstream of the flight speed pickup (6). A first summing circuit (11) subtracts the output signal of the amplifier (10) from that of the first differentiating element (8). An integrator (13) connected with its output to the correction adjustment drive (3) is connected with its input through a switch (12) to the summing circuit (11). A logic circuit (14) controls a switch (12) so that the switch (12) is closed as soon as the gradient of the function D.sub.T (v), where D.sub.T is the output signal of the delay circuit (7) and v is the flight speed, falls below the amplification factor G of the amplifier (10).