Below glide slope advisory warning system for aircraft

• US 3,947,809 A
• Filed: 01/22/1975
• Issued: 03/30/1976
• Est. Priority Date: 01/13/1975
• Status: Expired due to Term

• Current Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Sundstrand Data Control, Inc.
• Inventors: Bateman, Charles Donald
• Primary Examiner(s): Blix, Trygve M.
• Assistant Examiner(s): Kunin, Stephen G.
• Application Number:
  US05/540,476
• Time in Patent Office: 433 Days
• Field of Search: 73/178 R, 73/178 T, 73/179, 179/15 A, 235/150.2, 235/150.22, 244/77 A, 244/77 D, 340/16 R, 340/16 M, 340/16 C, 340/27 AU, 340/29, 340/52 H, 340/56, 340/62, 340/66, 340/74, 340/258, 343/5 LS, 343/7 R, 343/7 TA, 343/7 ED, 343/7 PF, 343/7.7, 343/8, 343/9, 343/12 R, 343/12 A, 343/108 R, 343/112 A, 343/112 CA, 343/112 S
• US Class Current: 340/970
• CPC Class Codes: G01C 5/005 altimeters for aircraft G01C5/02, G01C5/06 take precedence
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 takes precedence

Abstract

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.

Claims

1. In a glide slope warning system for use by aircraft at airports having a glide slope radio beam, having means for generating a signal representing the deviation of the aircraft from the glide slope, and means for generating a signal representing the altitude of the aircraft above ground, improved means for generating a warning signal when the glide slope deviation exceeds predetermined limits, said improved warning signal generating means comprising:

means for generating a first warning signal, in response to the deviation signal; and

means for generating a second warning signal, in response to the deviation signal, when the aircraft is below at least one predefined altitude.

2. The warning system of claim 1 wherein said first warning signal means includes:

means responsive to the deviation signal for generating a signal indicative of aircraft descent below a first predetermined distance below the glide slope; and

means for inhibiting said first warning signal above a first altitude.

3. The warnings system of claim 2 wherein said first warning signal means includes means for inhibiting said first warning signal in accordance with a predefined aircraft flight configuration.

4. The warning system of claim 2 wherein said second warning signal means includes:

means responsive to the deviation signal for generating a signal indicative of aircraft descent below a second predetermined distance below the glide slope; and

means for inhibiting said second warning signal above said predefined altitude.

5. The warning system of claim 4 wherein said warning improved signal means additionally includes:

means for inhibiting both said first and said second warning signals below a minimum altitude; and

means for inhibiting said first and said second warning signals in accordance with a predefined aircraft flight configuration.

6. The warning system of claim 5 additionally including means responsive to the altitude signal for incresaing the deviation required from the glide slope to trigger said first and said second warning signals with decreasing altitude.

7. An aircraft instrument for warning of excessive descent below a radio glide slope beam, comprising:

a glide slope beam receiver for generating a deviation signal indicative of the angular displacement of the aircraft below the glide slope;

a radio altimeter for generating a radio altitude signal;

means for combining the signal indicating the displacement of the aircraft below the glide slope with the radio altitude signal to provide an altitude biased deviation signal;

a first detector connected with said combining means for generating a first excessive deviation signal when said biased deviation signal exceeds a first value;

a second detector connected with said combining means for generating a second excessive deviation signal when said biased deviation signal exceeds a second value;

first warning means, responsive to said first excessive deviation signal for generating an advisory warning below a first predefined altitude; and

second warning means, responsive to said second excessive deviation signal, for generating a command warning below a second predefined altitude.

8. The aircraft instrument of claim 7 additionally including:

filter means for determining the validity of the glide slope beam received by said glide slope receiver;

means responsive to said radio altitude signal for inhibiting said warning signals below a minimum altitude;

means responsive to said filter means for inhibiting said warning signals when an invalid glide slope beam is being received;

and

means for inhibiting said warning signals when said aircraft is in a predetermined flight configuration.

9. A glide slope deviation warning system for use in aircraft having a glide slope deviation signal means and a radio altitude signal means, comprising:

a first summing means for combining the altitude signal with a bias signal representing a minimum altitude;

a scaling amplifier for converting said biased altitude signal into a signal scaled to represent a predefined ratio of units of glide slope deviation to units of altitude;

second summing means for combining the glide slope deviation signal with said scaled altitude signal;

third summing means for combining the glide slope deviation signal with said scaled altitude signal;

a first signal detector circuit operatively connected to said second summing means for generating an advisory warning signal when the output of said second summing means exceeds a first predetermined value;

a first gate circuit operatively connected to said first detector for inhibiting said advisory signal above a predetermined maximum altitude and below a predetermined minimum altitude;

a second signal detector circuit operatively connected to said third summing means for generating a command warning signal when the output of said third summing means exceeds a second predetermined value;

a second gate means operatively connected to said second detector circuit for inhibiting said command warning signal above a predetermined altitude.

10. The warning system of claim 9 additionally including a limiter circuit operatively connected between said first summing means and said scaling amplifier to limit said biased altitude signal.

11. The warning system of claim 10 wherein the output of said first gate is operatively connected to said second gate to inhibit said command warning signal whenever said advisory warning signal is inhibited.

12. The warning system of claim 11 wherein said first gate is operatively connected to a signal source representing the aircraft'"'"'s flight configuration for inhibiting said advisory warning when the aircraft is in a predetermined flight configuration.

13. An aircraft warning instrument for alerting the pilot of an aircraft of excessive descent below a radio glide slope beam during a landing approach, comprising:

a source of signal representing the altitude of the aircraft above the ground;

a source of bias signal representing a selected altitude;

a first summing circuit for adding the altitude signal to the bias signal;

a limiter connected to the output of said summing circuit for limiting the sum signal to a zero value for an altitude signal greater than said bias signal;

means for scaling connected to said limiter for scaling the limited altitude sum signal with predetermined ratio of glide slope deviation units to altitude units for altitudes below said selected altitude;

a source of signal representing the glide slope deviation signal;

a second summing circuit for adding the scaled altitude signal to the glide slope deviation signal;

a first detector circuit operatively connected to the output of said second summing circuit effective to generate an advisory warning logic signal when the output signal from the second summing circuit exceeds a predetermined value representing an excessive aircraft descent below the radio glide slope beam for a given altitude;

an indicator for providing an advisory warning;

a source of signal representing the minimum advisory altitude signal;

a first logic gate having one input operatively connected with the said first detector circuit, another input connected with the source of minimum advisory altitude signal and an output connected with the advisory warning indicator, said first logic gate acting to inhibit an output to the advisory warning indicator in the presence of an advisory logic signal when the aircraft is below the minimum advisory altitude;

a third summing circuit for adding the scaled altitude signal to the glide slope deviation signal;

a second detector circuit connected to the output of said third summing circuit effective to generate a command logic signal when the output signal of the third summing circuit exceeds another predetermined value, greater than said predetermined value of the first detector, representing an excessive descent of the aircraft below the radio glide slope beam for a given altitude;

an indicator for providing a command warning;

a source of signal representing the maximum command altitude;

a second logic gate having one input operatively connected to said second detector, another input connected to said source of maximum command altitude and an output connected with the command warning indicator, said second logic gate acting to inhibit an output to the command warning indicator in the presence of a command logic signal when the aircraft is above the maximum command altitude;

a source of signal representing an upper limiting altitude;

means for inhibiting both said advisory and command logic signals above said upper limiting altitude; and

means for inhibiting said command logic signal unless the advisory logic signal is being generated.

14. The aircraft warning instrument as defined in claim 13, wherein the scaling means includes a first scaling amplifier providing said second summing circuit with a first predefined ratio of scaled altitude signal and a second scaling amplifier providing said third summing circuit with a second predefined ratio of scaled altitude signal.

15. The aircraft warning instrument of claim 13 further including:

means actuated by an operator in the aircraft and operative only below said upper limiting altitude and without a command logic signal being generated, to inhibit both said advisory and command logic signals when the operator intends to maneuver the aircraft below the glide slope sufficient to produce an advisory or command warning by the warning instrument; and

means for terminating the operator actuated advisory and command warning inhibit above said upper limiting altitude.

16. An aircraft warning instrument for alerting the pilot of excessive descent below a radio glide slope beam, comprising:

a source of signal representing the angular deviation of the aircraft position from the radio glide slope beam;

means operative above and below a selected altitude and responsive to said below glide slope deviation signal in excess of a first threshold value for generating an adivsory warning signal; and

means operative below said selected altitude and responsive to said below glide slope deviation signal representing a below glide slope condition in excess of a second threshold value for generating a command warning signal.

17. The aircraft warning instrument of claim 16 including:

a source of signal representing the altitude of the aircraft above the ground; and

means for effectively varying the below glide slope first and second threshold values as a function of said altitude signal.

18. The aircraft warning instrument of claim 17 wherein said threshold varying means includes:

a scaling amplifier for increasing the first and second threshold values of the advisory and command warning signals respectively as the altitude signal decreases below 150 feet; and

means for inhibiting said scaling amplifier above 150 feet for altitude.

19. The aircraft warning instrument of claim 16 in which said selected altitude is 300 feet above ground.

20. The aircraft warning instrument of claim 16 including means to inhibit said advisory warning signal above an upper altitude limit of 1,000 feet.

21. An aircraft warning instrument for alerting the pilot of excessive descent below a radio glide beam, comprising:

a source of signal representing the radio altitude of the aircraft above ground;

a source of signal representing the deviation of the aircraft position from the glide slope beam;

means operative below a selected altitude and above a minimum altitude and responsive to a signal representing a deviation of the aircraft below the glide slope beam in excess of a first threshold value to generate an advisory warning signal; and

means operative below a predetermined altitude within said selected and minimum altitude range of the advisory warning signal and responsive to a signal representing a deviation of the aircraft below the glide slope beam in excess of a second threshold value greater than said first threshold value to generate a command warning signal.

22. The aircraft warning instrument of claim 21 in which said minimum altitude is 50 feet, said predetermined altitude is 300 feet and said selected altitude is 1,000 feet, said warning instrument further including:

means for effectively varying the below glide slope first and second threshold values as a function of said radio altitude signal causing an increase in both threshold values as aircraft altitude decreases below 150 feet; and

means for maintaining the below glide slope first and second threshold values constant above 150 feet.

23. In a warning instrument for alerting the pilot of an aircraft to a condition of undesired proximity to the ground at an airport equipped with a glide slope radio beam transmitter, the warning instrument including a source of signal in the aircraft responsive to the glide slope radio beam, the signal representing the magnitude of the angular deviation of the aircraft position from the glide slope radio beam, a source of signal representing the aircraft altitude above the ground, and detector means responsive to a first angular deviation and altitude criteria to generate an advisory warning and to a second angular deviation and altitude criteria to generate a command warning, a glide slope warning inhibit circuit, comprising:

a source of inhibit signal;

means responsive to the inhibit signal for preventing generation of either said advisory warning or said command warning; and

means responsive to occurrence of said command warning to prevent operation of the inhibit signal responsive means.

24. The glide slope warning inhibit circuit of claim 23 in which said inhibit signal responsive means is inoperative above an upper altitude limit.

25. The glide slope warning inhibit circuit of claim 23 in which said warning instrument includes an advisory warning detector having an output, a command warning detector having an output, an advisory warning AND gate having as an input the output of the advisory warning detector, a command warning AND gate having as an input the output of the command warning detector and the output of the advisory warning AND gate, the inhibit signal responsive means including an inhibit AND gate having as an input the inhibit signal and an inversion of the command warning signal from the command warning AND gate, to prevent operation of the inhibit signal responsive means on occurrence of the command warning and an inversion of the output of the inhibit AND gate being an input to the advisory warning AND gate to prevent generation of either warning.

26. The glide slope warning inhibit circuit of claim 25 including a bistable inhibit flip-flop, the output of the inhibit AND gate being connected with the set input of the flip-flop and the output of the flip-flop being connected with an input of the advisory warning AND gate to prevent generation of the warnings, and means providing a signal representing the altitude of the air-craft above the glide slope warning zone, connected with the reset input of said flip-flop.