The flight test engineer constantly strives to provide solutions to the problems of testing, developing and proving the progressively more complex and accurate navigation and attack systems of modern military aircraft. The biggest such challenge in Europe for some time was probably the flight trials programme on the swing-wing Tornado aircraft which has a digitally based, self contained, al-lweather NAV/ATTACK avionics system. This paper covers the philosophy and techniques adopted for the flight testing and subsequent analysis of major elements of this system.