Assault helos were a form of helicopter used by the GLOCK during Der Lange Krieg.
Assault helos are Blackhawk sized helicopters armed with 3 30mm cannons that are capable of firing downwards. There have 4 crewmembers, a pilot, a copilot/gunner and two dedicated gunners.
There is also room for a small number of troops onboard. The assault helo will fly at over 10,000ft or more. Unless major anti-aircraft systems are present, an assault helo can hover beyond the range of small arms, heavy machine guns, and small anti-aircraft missiles. Keep in mind that the vertical range of projectiles fired from below is much less than their horizontal range due to gravity.
Most gun mounts cannot elevate to fire vertically anyway. The bottom of the helo has extra armour to provide protection from small arms fire at lower levels or large caliber rounds weakened by extreme ranges. They are also equipped with unguided rocket packs that they fire in volleys. Using GPS to locate and computers to calculate firing data, accuracy is fairly high.