This
report to EASA argues that the regulators should consider requiring helicopter pilots to wear helmets and visors to mitigate the effects of windshield bird strike penetrations.
This is because 5 to 8% of bird strike on large, Part 29 rotorcraft are occurring above the current test criteria, many of the other strikes are still resulting in windscreen penetration and there are actually no bird impact tests currently required for Part 27 rotorcraft.