Calculated and measured in-flight antenna patterns on an ATR 72 aircraft

The certification of antenna installations on aircraft typically comprises an element of flight testing to ensure the system performance of the avionics installations e.g. for VHF communications one verifies adequate reception when one flies circuits at 80% of the geometric radio horizon. In addition to these tests it is important to verify that the antenna radiation pattern provides adequate coverage over the full range of angles. The antenna pattern is traditionally characterised by scaled model measurements, which unfortunately present a certain number of disadvantages: The models are relatively expensive and inflexible, they can oversimplify the aircraft geometry and one is limited in the range of antennas and materials that can be modelled. With advances in computing and aircraft navigation two alternative approaches have become viable to provide the antenna radiation patterns: Numerical modelling and in-flight measurements. In this presentation we cross-validate these two approaches.