An improved glide slope receiver circuit prevents false acquisition of glide slope and insures that only a good and existing glide slope signal will arm the glide slope circuitry. A normally charged capacitor applies lock-out potential to the glide slope switching network. A reference square wave is applied to open a gate. Below glide slope signals are received out of phase with the reference and proceed through the gate to discharge the capacitor through a time constant network. Discharge of the capacitor releases the lock-out potential at the glide slope switching network, thus permitting the glide slope receiver to acquire the glide slope at a glide slope signal null.
A method for calibrating and correcting circuit errors induced in an aircraft ILS receiving system is disclosed herein. The spectral components of the input signal are processed through bandpass filters and then rectified and integrated in order to produce an output signal representative of the deviation from the desired centerline course. First and second test signals are generated corresponding to first and second known positions. These test signals are sequentially processed in the same manner as the operational input signals in order to develop first and second position errors which represent distortion and circuit induced errors within the processing system. A corrective function is then derived for a range of operational input signals by interpolating from the first and second position errors. All subsequently processed signals are adjusted by applying the corrective function. In this manner, the various distortions that are introduced through the processing system will be measured and then subtracted from the output signals in order to define a corrected representation of deviation from the desired centerline course. Sampling periods are utilized which contain an integer multiple of cycles of each of the major frequencies present in the operational input signal.
This invention provides an improvement in the present instrument approach procedure used at airports having an ILS localizer without an accompanying UHF glide-slope. The field strength of the localizer, as measured at the airplane, is used as a basis for producing a glide-slope deviation signal. The shape of the resulting path may be adjusted by changing the input/output characteristic of a localizer receiver.
For use in an aircraft warning system which measures the descent below a radio glideslope and compares it with the aircraft's altitude above ground to generate a warning when the descent below glideslope exceeds predefined limits for a particular altitude, circuitry is provided to generate an advisory warning above a predefined altitude and a hard warning, or command to take immediate action, below the predetermined altitude.
An aircraft instrument for warning the pilot that the aircraft is in an unsafe condition in proximity to the ground. The instrument has inputs representing aircraft configuration, flight condition with respect to the ground, and glide slope. Detector circuits process the inputs and give a warning of unsafe proximity to the ground. The boundary conditions for the warning are selected to avoid false warnings. A glide slope detector distinguishes between a valid glide slope signal and spurious signals, without need for pilot input.
