Towards a Wireless Aircraft

The replacement of many of of an aircraft’s wired interconnects with wireless data connections would offer a number of benefits. These include: weight reduction, easier maintenance, faster aircraft design, simpler retrofitting and greater redundancy. However, attempting to do this produces a lot of challenges and risks because data connections on an aircraft must meet very high standards for reliability. This PhD Thesis lays out the main challenges of the propagation environment explaining that large sections of an aircraft may be highly resonant and explain- ing the difficulties this presents for wireless receivers. Modern wireless standards are explored and the question of how suitable they would be for this application is addressed. Two standards are recommended: 802.11n and ZigBee and these are tested in a variety of environments such as a reverberation chamber and avionics bays in a Tornado, to demonstrate the levels of time delay spread needed to prevent a wireless system from working. In particular, the sta- tistical distribution of the channel is emphasised and we show how one must expect Rayleigh fading of the signal even over short distances which has implications when the channel is time varying, such as in an aircraft wing. A variety of approaches are suggested for reducing the probability of system failure by adding redundancy in various forms to boost link availability. As well as the detailed study of propagation in an airframe some of the general issues of a wireless aircraft are addressed such as data rates, what types of system could be made wireless and what types of data bus would wireless be replacing. As this work was done under the Flaviir UAV program, some of the collaborative work is presented showing the design of a novel patch antenna written onto the aircraft skin by a genetic algorithm.