Excessive descent rate warning system for aircraft

A warning system utilizing aircraft altitude signals and rate of change in aircraft altitude signals for warning of excessive descent rates, comprising:

• first signal means responsive to the altitude and the altitude rate signals for generating a warning signal in conformity to a first predetermined relationship between descent rate and altitude;
• a limit means for restricting the operation of said first signal means to a predetermined range of aircraft altitude rate signals;
• and
• second signal means responsive to the altitude and altitude rate signals for generating the warning signal in conformity with a second predetermined relationship between descent rate and altitude for a second range of altitude rate signals.

A warning system for use in aircraft for generating a warning when the descent of the aircraft exceeds a predetermined rate for a given altitude, comprising:

• an electronic circuit for generating an altitude signal from a radio altimeter representing the aircraft altitude above ground;
• a rate circuit for generating a signal representing the aircraft rate of descent from a barometric altimeter;
• a first computational circuit for combining said barometric rate signal with said altitude signal to generate a warning signal as a first function of descent rate versus altitude;
• and
• a second computational circuit connected to said first computational circuit and operative only at descent rates exceeding a selected descent rate, for altering said function of descent rate versus altitude of the warning signal to a fixed time to ground impact.

An electronic circuit, having radio altimeter and rate of change in barometric altitude signal inputs, for generating a logic signal to activate an excessive descent rate alarm, comprising:

• a first summing circuit for adding the altitude rate signal to a first bias signal;
• a limiter operatively connected to said first summing circuit;
• a first scaling amplifier operatively connected to said limiter;
• a second summing circuit for adding the altitude rate signal to a second bias signal;
• a rectifier operatively connected to said second summing circuit effective to limit said second biased rate signals to a predetermined polarity;
• a second scaling amplifier operatively connected to said rectifier;
• a third summing circuit operatively connected to both said first and second scaling amplifiers for summing the outputs of said amplifiers;
• a fourth summing circuit operatively connected to said third summing circuit and to the radio altimeter to combine the output of said third summing circuit with the radar altitude signal;
• and
• a detector circuit operatively connected to said fourth summing circuit to generate the logic signal for a predetermined signal output of said fourth summing circuit.

A warning instrument for alerting the pilot of an aircraft to a condition of undesired excessive descent rate in proximity to the ground, comprising:

• a source of signal representing the rate of descent of the aircraft;
• a source of signal representing the altitude of the aircraft above the ground;
• means operative below a selected descent rate to scale the descent rate signal by a first factor;
• means operative above said selected descent rate to scale the descent rate signal by a second factor;
• means for comparing the scaled descent rate signal with the signal representing the altitude of the aircraft above the ground;
• and
• means responsive to the comparator to actuate a pilot warning when the scaled descent rate signal exceeds the altitude signal.

A warning system for generating a warning indicating an excessive aircraft descent rate with respect to the ground that utilizes a signal representing the aircraft barometric descent rate and a signal representing the aircraft altitude above the ground, comprising:

• means responsive to the altitude signal and the descent rate signal for generating, at an altitude above ground of approximately 50 feet or greater, a warning signal as a first substantially linear function of descent rate versus altitude wherein said warning signal is generated for descent rates of approximately 1300 fpm and greater at an altitude of 50 feet, and at descent rates of approximately 2357 fpm and greater, at an altitude of 1178 feet above ground;
• means responsive to the altitude signal and the descent rate signal for generating said warning signal at altitudes above approximately 1178 feet above ground as a second substantially linear function of descent rate versus altitude wherein said warning signal is generated at descent rates greater than 2357 fpm at an altitude of approximately 1200 feet above ground, and at descent rates of approximately 4900 fpm and greater at an altitude of 2450 feet above ground;
• and
• means for inhibiting said warning signal at altitudes of above approximately 2450 feet above the ground.