Recent in-flight instances of aircraft engine power loss involving hail ingestion have forced the
manufacturers to demonstrate successful engine operation whilst ingesting hail. The main
objective of this research project has been to obtain an understanding of the basic
characteristics of hailstone impacts. A hail gun was designed to fire simulated hailstones at
speeds up to 175 m/s. Three measurement techniques were used to determine the impact
characteristics of the hailstones, i.e: patternator, high speed cine-photography, and still
photography with short duration flashes. Using these techniques, the basic impact
characteristics in terms of post-impact particle size, velocity and mass distribution were
obtained for a variety of target configurations. The influence of seemingly important
parameters on the impact characteristics were investigated, including approach angle and
velocity, target curvature, and target rotation. Studies were further made into multiple impacts,
and the effect of target curvature and rotation on the impact characteristics. Based on the
experimental results, a set of empirical rules and a mathematical model describing hailstone
break-up were defined.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy at Loughborough University.