# US 9,753,143 B2 · Aircraft navigation system and method of navigating an aircraft > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,753,143 B2 - Document ID: US9753143B2 - Status: Granted - Kind: B2 - Application number: 15/035,819 - Filed: 2014-11-10 - Published: 2016-10-13 - Granted: 2017-09-05 - Earliest claimed: 2013-11-11 - Assignees: Airbus Defence and Space GmbH - Applicants: Airbus Defence and Space GmbH - Inventors: Cristiano Bianchi; Winfried Lohmiller - Web page: https://patentgrep.com/patent/US9753143B2 ## CPC - G01S 19/32: Multimode operation in a single same satellite system, e.g. GPS L1/L2 - G01S 19/18: Military applications - G01S 19/21: Interference related issues {; Issues related to cross-correlation, spoofing or other methods of denial of service} - G05D 1/0022: {characterised by the communication link (data switching networks in general H04L12/00)} - G05D 1/0077: {using redundant signals or controls} - G08G 5/20: Arrangements for acquiring, generating, sharing or displaying traffic information (arrangements for monitoring traffic G08G5/72) - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES - G08G: TRAFFIC CONTROL SYSTEMS (guiding railway traffic, ensuring the safety of railway traffic B61L; arrangement of road signs or traffic signals E01F9/00; radar or analogous systems, sonar systems, lidar systems specially adapted for traffic control G01S13/91, G01S15/88, G01S17/88; {radar or analogous systems, sonar systems, lidar systems specially adapted for anti-collision purposes G01S13/93, G01S15/93, G01S17/93}) ## Abstract An aircraft navigation system and navigation method. The system comprises a civil-certified GPS-receiver for determining first position information based on C/A-GPS-signals, and a military-type GPS-receiver for determining a second position information based on P(Y)-GPS-signals. A monitoring unit detects a first abnormal condition during jamming conditions within the C/A-GPS-signals. The unit compares the first position information with the second position information and detects a second abnormal condition when a difference between these position information is larger than a threshold value for more than a threshold duration. Upon detecting an abnormal condition, an alert procedure is initiated. In remotely piloted aircraft, Command & Control link-loss is also monitored and during link-loss, a transponder code automatically indicates communication failure. When in such situation an abnormal condition is additionally detected, a transponder code indicates airborne emergency and, subsequently, the aircraft navigation system is switched to navigating based on position information from the military-type GPS-receiver. ## Claims ### Claim 1 An aircraft navigation system for an unmanned aircraft comprising: a civil-certified GPS-receiver, a military-type GPS-receiver, and a control device provided by a computer, the control device including a monitoring unit and an alerting unit, wherein the civil-certified GPS-receiver is configured to determine a first position information based on civil course/acquisition code GPS signals (C/A-GPS-signals), wherein the military-type GPS-receiver is configured to determine a second position information based on military precision code or encrypted precision code GPS signals (P(Y)-GPS-signals), wherein the aircraft navigation system is configured to issue aircraft navigation signals based on the first position information when the aircraft is flying under civil-certified navigation control in civil airspace, wherein at least one of: the monitoring unit is configured to detect jamming of the C/A-GPS-signals, or the monitoring unit is further configured to compare the first position information with the second position information, and to detect an occurrence of a difference between the first position information and the second position information being larger than a threshold value for more than a threshold duration, and wherein the alerting unit is configured to initiate an alert procedure upon detection of at least one of the jamming of the C/A GPS signals and the occurrence of the difference between the first position information and the second position information being larger than a threshold value for more than a threshold duration. ### Claim 2 (depends on 1) The aircraft navigation system of claim 1, wherein the aircraft navigation system is specifically configured for application in a remotely piloted aircraft and wherein the monitoring unit is further configured to detect a Command & Control link-loss while flying in civil airspace and for, upon such detection, automatically setting a transponder code in the aircraft to issuing a signal indicating communication failure, and wherein the alerting unit is further configured to, upon detection of one of the jamming of the C/A GPS signals and the occurrence of the difference between the first position information and the second position information being larger than a threshold value for more than a threshold duration and simultaneous detection of Command & Control link-loss, as part of the alert procedure automatically setting a transponder code in the aircraft to issuing a signal indicating airborne emergency and switching to issuing aircraft navigation signals based on the second position information. ### Claim 3 (depends on 1) The aircraft navigation system of claim 1, wherein the alert procedure comprises transmitting a specific warning signal to a pilot. ### Claim 4 (depends on 1) The aircraft navigation system of claim 1, wherein the civil-certified GPS-receiver is segregated with respect to the military-type GPS-receiver. ### Claim 5 (depends on 1) The aircraft navigation system of claim 1, wherein the civil-certified GPS-receiver and the military-type GPS-receiver are comprised in different line replaceable units. ### Claim 6 A method of navigating an unmanned aircraft, the aircraft comprising an aircraft navigation system with a civil-certified GPS-receiver, a military-type GPS-receiver, and a control device provided by a computer, wherein the civil-certified GPS-receiver is adapted for determining a first position information based on civil course/acquisition code GPS signals (C/A-GPS-signals), wherein the military-type GPS-receiver is adapted for determining a second position information based on military precision code or encrypted precision code GPS signals (P(Y)-GPS-signals), the method comprising: determining the first position information by the civil-certified GPS-receiver, determining the second position information by the military-type GPS-receiver, the aircraft navigation system navigating the aircraft according to aircraft navigation signals based on the first position information when the aircraft is flying under civil-certified navigation control in civil airspace, at least one of detecting jamming of the C/A-GPS-signals, or comparing the first position information with the second position information, and detecting an occurrence of a difference between the first position information and the second position information being larger than a threshold value for more than a threshold duration, and initiating an alert procedure upon detection of one of the jamming of the C/A GPS signals and the occurrence of the difference between the first position information and the second position information being larger than a threshold value for more than a threshold duration. ### Claim 7 (depends on 6) The method of claim 6, further comprising: detecting a Command & Control link-loss while flying in civil airspace and, upon such detection, automatically setting a transponder code in the aircraft to issuing a signal indicating communication failure, and upon detection of at least one of the jamming of the C/A GPS signals and the occurrence of the difference between the first position information and the second position information being larger than a threshold value for more than a threshold duration and simultaneous detection of Command & Control link-loss, as part of the alert procedure, automatically setting a transponder code in the aircraft to issuing a signal indicating airborne emergency and switching to issuing aircraft navigation signals based on the second position information. ### Claim 8 (depends on 6) The method of claim 6, wherein the alert procedure comprises transmitting a specific warning signal to a pilot. ### Claim 9 (depends on 6) A non-transitory computer readable medium comprising computer readable code stored thereon which, when executed by a computer, is configured to control the method according to claim 6. ### Claim 10 An aircraft navigation system comprising: a civil-certified GPS-receiver, a military-type GPS-receiver, and a control device provided by a computer, the control device including a monitoring unit and an alerting unit, wherein the civil-certified GPS-receiver is configured to determine a first position information based on civil course/acquisition code GPS signals (C/A-GPS-signals), wherein the military-type GPS-receiver is configured to determine a second position information based on military precision code or encrypted precision code GPS signals (P(Y)-GPS-signals), wherein the aircraft navigation system is configured to issue aircraft navigation signals based on the first position information when the aircraft is flying under civil-certified navigation control in civil airspace, wherein at least one of: the monitoring unit is configured to detect jamming of the C/A-GPS-signals, or the monitoring unit is further configured to compare the first position information with the second position information, and to detect an occurrence of a difference between the first position information and the second position information being larger than a threshold value for more than a threshold duration, and wherein the alerting unit is configured to initiate an alert procedure upon detection of at least one of the jamming of the C/A GPS signals and the occurrence of the difference between the first position information and the second position information being larger than a threshold value for more than a threshold duration.