Aircraft navigation system and method of navigating an aircraft

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.

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.