| 摘要 |
An aircraft navigation system and method of navigating an aircraft are proposed. The system (1) comprises a civil-certified GPS-receiver (3) for determining first position information based on C/A-GPS-signals and a military-type GPS-receiver (5) for determining a second position information based on P(Y)-GPS-signals. The system (1) is adapted to issue aircraft navigation signals based on the first position information when the aircraft is flying under normal navigation conditions in civil airspace. A monitoring unit (7) detects a first abnormal navigation condition upon occurrence of jamming conditions within the C/A-GPS-signals. Furthermore, it compares the first position information with the second position information and detects a second abnormal navigation condition upon occurrence of a difference between these position information being larger than a threshold value for more than a threshold duration. Upon detection of an abnormal navigation condition, an alert procedure such as transmitting a warning signal to a pilot is initiated. In a particular application in remotely piloted aircraft, Command & Control link-loss is additionally monitored and in case of link-loss, a transponder code is automatically set to issuing a signal indicating communication failure. Furthermore, when in such situation an abnormal navigation condition is additionally detected, a transponder code is set for issuing a signal indicating airborne emergency and, subsequently, the aircraft navigation system (1) is switched to navigating based on position information from the military-type GPS-receiver (5). |
