Somatogravic illusion and Spatial disorientation.
2000 hrs night-ag tends to expose one to the dangers of both these perils more often than is considered comfortable. Typically operating ag aircraft with the max fuel and load possible every takeoff does not preclude the possibility of SI onset, indeed I found it increased it, when, for whatever reason, performance was improved, both on takeoff, and during spray operations. It's the unexpected that will get you everytime, and no amount of training will prevent it. Remember, both are cerebral perceptions, caused by physical stimuli, which without the benefit of our strongest sense (sight), can be overwhelming. On a dark night, while spraying, I once experienced SD, simply by reversing my turn faster than I had the previous 4 or 5 times, while turning over a black hole. I can tell you all that the noise approximating acceleration in my ears, would beat any rock concert I have ever attended. Terrifying! What to do? I froze on the stick, eyes inside to check ASI and Alt, (elect T&B are useless), then back outside to regain horizon. I knew I was climbing, I knew I had checked roll, I was at 400' agl before I had a positive horizon, and could continue to treat the field. With 8/8 overcast, a very dark night, we perhaps should have been in the stubby-hut, enjoying the fruits of the brewers toils, and the sight of rain in the worklights while clearing the strip for continued ops was a welcome sight indeed.
How do we combat these accidents? The only mitigation available IMHO, is education, and experience. It is clear, we cannot hope to survive all the experiences of others, (mortality is a bitch) so we must learn from the experience and unfortunate misadventures of others. So keep your own experiences coming. If we are reading them, you have survived, and have the best knowledge available for the betterment of your fellows.
RIP the folk in the C210, so very sad.
Heed their experience, could save your own life one day.