Vertical Required Navigation Performance Containment with Radio Altitude

• US 20110035080A1
• Filed: 08/05/2009
• Published: 02/10/2011
• Est. Priority Date: 08/05/2009
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Murphy, Timothy Allen
• Granted Patent: US 8,494,693 B2
• Time in Patent Office: Days
• US Class Current: 701/9
• CPC Class Codes: B64D 45/04 Landing aids; Safety measures to prevent collision with earth's surface
• CPC Class Codes: G01C 23/00 Combined instruments indicating more than one navigational value, e.g. for aircraft; Combined measuring devices for measuring two or more variables of movement, e.g. distance, speed or acceleration
• CPC Class Codes: G01S 13/882 for altimeters measuring height using barometric means G01C5/06
• CPC Class Codes: G01S 19/32 Multimode operation in a single same satellite system, e.g. GPS L1/L2
• CPC Class Codes: G01S 7/003 Transmission of data between radar, sonar or lidar systems and remote stations
• CPC Class Codes: G05D 1/0676 specially adapted for landing
• CPC Class Codes: G08G 5/0021 located in the aircraft
• CPC Class Codes: G08G 5/025 Navigation or guidance aids radar or analogous systems specially adapted for landing purposes G01S13/913

Abstract

A monitor on-board an aircraft which uses radio altitude measurements as the basic observable altitude during runway approach. The basic concept utilizes the aircraft'"'"'s navigation system, which includes means to store and retrieve radio altitude thresholds as a function of the distance along the desired path from the runway thresholds. These threshold functions are determined in advance based on a radio altitude reference which is defined as the expected radio altimeter measurement that would be made if the airplane were exactly on the desired reference path. Vertical containment monitoring is achieved by comparing the radio altitude measurement to computed thresholds for both too high and too low. During the approach, an annunciation message can be generated if the radio altitude measurement is above or below the threshold limits. Using this monitor ensures that the total system error for the aircraft is contained within a bound called the Vertical Containment Level of the desired reference path in space with a probability that is specified.

Claims

1. A method for detecting deviation of true airplane vertical position from a desired reference path, comprising the following steps:

storing high and low radio altitude thresholds which vary as a function of horizontal distance from a runway threshold;

acquiring radio altitude measurements as the aircraft approaches the runway threshold; and

comparing each radio altitude measurement to a respective pair of said high and low radio altitude thresholds.

2. The method as recited in claim 1, further comprising the step of generating an indicator that indicates a radio altitude measurement has exceeded a high or low radio altitude threshold.

3. The method as recited in claim 1, further comprising the step of computing said high and low radio altitude thresholds as a function of reference radio altitudes representing expected radio altitude measurements were the aircraft to travel along a desired reference path, said computing step being performed prior to said storing step.

4. The method as recited in claim 1, wherein said reference radio altitudes are determined as a function of GPS and radio altitude measurements of aircraft position recorded over the course of multiple prior approaches.

5. The method as recited in claim 1, wherein said reference radio altitudes are determined as a function of raw GPS measurements made on an aircraft and ground-based measurements of aircraft position recorded over the course of multiple prior approaches.

6. The method as recited in claim 1, wherein said high and low radio altitude thresholds are set to ensure an acceptable probability of false alarms.

7. The method as recited in claim 1, wherein said high and low radio altitude thresholds are not derived from a terrain database.

8. The method as recited in claim 1, wherein the aircraft is flying a barometric vertical navigation path.

9. A system for detecting deviation of true airplane vertical position from a desired reference path, comprising:

a database storing high and low radio altitude thresholds which vary as a function of horizontal distance from a runway threshold;

a radio altimeter for acquiring radio altitude measurements as the aircraft approaches the runway threshold; and

a processor for comparing each radio altitude measurement to a respective pair of said high and low radio altitude thresholds.

10. The system as recited in claim 9, further comprising an indicator that indicates a radio altitude measurement has exceeded a high or low radio altitude threshold in response to an output from said processor.

11. The system as recited in claim 10, wherein said indicator is a cockpit display.

12. The system as recited in claim 9, wherein said high and low radio altitude thresholds are set to ensure an acceptable probability of false alarms.

13. The system as recited in claim 9, wherein said high and low radio altitude thresholds are not derived from a terrain database.

14. A system comprising:

a GPS receiver;

an air data inertial reference unit;

a radio altimeter;

a data logging memory for logging data received from said GPS receiver, from said air data inertial reference unit and from said radio altimeter;

a programmable command processor programmed to manage the logging of data in said data logging memory; and

a data transceiver for transmitting data from said data logging memory to a central processing facility on the ground and for receiving programming for said command processor from the central processing facility.

15. The system as recited in claim 14, further comprising:

a database storing high and low radio altitude thresholds which vary as a function of horizontal distance from a runway threshold; and

a multi-mode receiver that communicates with said database, with said radio altimeter and with said data transceiver, said multi-mode receiver having a processor for comparing each radio altitude measurement received from said radio altimeter to a respective pair of said high and low radio altitude thresholds read from said database.

16. The system as recited in claim 15, wherein said multi-mode receiver receives updated high and low radio altitude thresholds from said data transceiver for storage in said database.

17. The system as recited in claim 15, further comprising an indicator that indicates a radio altitude measurement has exceeded a high or low radio altitude threshold in response to a command from said multi-mode receiver.

18. The system as recited in claim 17, wherein said indicator is a cockpit display.

19. The system as recited in claim 15, wherein said high and low radio altitude thresholds are set to ensure an acceptable probability of false alarms.

20. The system as recited in claim 15, wherein said high and low radio altitude thresholds are not derived from a terrain database.

21. An aircraft comprising:

a database storing high and low radio altitude thresholds which vary as a function of horizontal distance from a runway threshold;

a radio altimeter for acquiring radio altitude measurements as the aircraft approaches the runway threshold; and

a processor for comparing each radio altitude measurement to a respective pair of said high and low radio altitude thresholds.

22. The aircraft as recited in claim 21, further comprising an indicator that indicates a radio altitude measurement has exceeded a high or low radio altitude threshold in response to an output from said processor.

23. The aircraft as recited in claim 21, further comprising:

a GPS receiver;

an air data inertial reference unit;

a data logging memory for logging data received from said GPS receiver, from said air data inertial reference unit and from said radio altimeter;

a programmable command processor programmed to manage the logging of data in said data logging memory; and

a data transceiver for transmitting data from said data logging memory to a central processing facility on the ground and for receiving programming for said command processor from the central processing facility.