Combined aircraft magnetometer for in-flight calibration and emergency use.

The instrument (10) has a calculator for determining and displaying an altitude (42), speed (40), an attitude (14) and a current heading (48) of an aircraft on a color screen (12) from air data sensors, inertial sensors and a magnetic field sensor. The calculator calibrates the magnetic field sensor, and displays a guide on the screen for the calibration of the magnetic field sensor. The calculator determines and displays already attained heading indications (50) and remaining heading indications to be attained (52) to complete the calibration of the magnetic field sensor. An independent claim is also included for a method for calibrating a backup instrument.