Final answer:
A full alignment of the ADIRS is performed to ensure accurate flight data. It involves setting the system to NAV mode, entering the aircraft's position, and allowing the inertial reference units to orient relative to the Earth's rotation. The whole process can take between 5 and 17 minutes and requires the aircraft to be stationary.
Step-by-step explanation:
The Air Data Inertial Reference System (ADIRS) is an essential component in modern aircraft, providing critical flight data such as airspeed, altitude, and aircraft attitude to both pilots and onboard systems. A full alignment of the ADIRS is crucial for ensuring the accuracy of this information. The ADIRS consists of multiple inertial reference units (IRUs) that use accelerometers and gyroscopes to determine the plane’s position and orientation without external references.
To accomplish a full alignment, the ADIRS must be switched to NAV mode, which starts the alignment process. This process requires accurate input of the aircraft’s current position, which is usually entered manually by the flight crew using the cockpit’s navigation controls. The aircraft should remain stationary during alignment as movement can interfere with the IRUs’ ability to accurately establish orientation.
Once the starting position is entered, the IRUs begin to calculate the aircraft’s orientation relative to the earth's surface. This involves gyroscopic precession, where the system accounts for the Earth’s rotation. The time taken for full alignment can vary, typically between 5 to 17 minutes, depending on the type of aircraft and the IRUs’ capabilities.