Effects of lightning on UAM aircraft: Complex zoning and direct effects on composite prop-rotor blade

Abstract

A UAM is a small to medium-distance air transportation system that carries passengers in and out of the city by flying at low altitudes. UAMs are based on eco-friendly electric propulsive systems to enhance mobility and maximize the use of three-dimensional airspace. However, UAM aircraft are very vulnerable to lightning strikes due to their relatively small size and flight characteristics, flying close to the ground. To tackle this problem, the present study developed a lightning zoning method for UAM aircraft with complex configurations and investigated the direct effects of lightning strikes on the prop-rotor blade of a UAM aircraft. First, computational simulation models for zoning analysis were developed for four representative UAM aircraft (one wingless multi-copter, one winged lift/cruise, and two winged vectored thrust types). The lightning zoning analysis identified the prop-rotor blade tips as Zone 1A, which has a high probability of initial lightning attachment. The direct effects of lightning strikes on a prop-rotor blade made of woven carbon/epoxy laminate were then investigated using both experimental and numerical methods. In general, the damage pattern of the simulation results agreed fairly well with the damage pattern in the experimental results. Moreover, it was shown that the prop-rotor blade of a relatively small UAM aircraft can suffer more damage, even after being struck by the lightning of the same intensity. In the future, since batteries, electric motors, inverters, and hydrogen fuel tanks, which are required by the new propulsion systems in UAM aircraft, will be increasingly used, designing a lightning protection system that properly reflects these changes will emerge as an important issue.