If you really want to know what happens when a drone hits a plane, then the obvious answer is to create a collision between a real aircraft and a drone under controlled circumstances. And that’s precisely what a bunch of enthusiasts in Hungary just did.
They staged a series of collisions using a Russian-built Antonov AN-2. One of them hit the biplane’s strut, another the bottom surface of the lower airfoil, and a third was thrown at the propellers.
YouTube User Joe Morales commented:
I worked on an AN-2. It is built like a tank. I think it gets into the air at about 70 mph. We’ve seen other demos like this at simulated speeds over 200 mph with much different results. Even though the damage to the AN-2 seems superficial, it would still take several hours to repair taking this aircraft out of service. The same situation with a strike on a Cessna 172 windshield has the potential of killing the pilot/ passenger. More than likely an aircraft of this size would receive superficial damage if it was to strike a drone but the potential is there to cause catastrophic damage.
Source: YouTube