What's this spatial D? Disorientation?
You got it. Or vertigo. It can happen in all kinds of different situations, but flying at night over water is a particularly good way to get it. Your body screams to you that the aircraft is doing one thing, when in fact it is doing another. It is very dangerous if you don't learn to trust what your instruments are telling you. I've had it three times..each leaves an impression on you.
It can also be particularly vicious on the wing in the weather. I've had it several times in that situation, to the point where it is almost a foregone conclusion.
Imagine flying 3 foot wingtip spacing, and the cloud deck is a couple of thousand feet thick. Basically, all you can see is the wingtip light, with the fuselage just being a shadow (if you see it at all). And that's ALL you can see...no ground, no sky, not even passing clouds...just a solid 'inside the egg' shade of grey (or darker).
Now add to this several turns by lead at slow roll rates following radar vectors to an instrument final. And since you're flying on the wing, your head is turned toward lead, therefore your otolith organs and semi circular canals are no longer aligned in the proper orientation to the acceleration and roll forces.
Add that all up, mix it together and it's a perfect setup for spatial D. Usually, when I've had it, it feels like you're in some extreme bank angle (90+ degrees) but are actually straight and level. It's a weird feeling, but you can deal with it IF you have sufficient brain bytes left over to do so.
Now, be aware, that you can KNOW you are spatial D and still become a victim of it. There is a harrowing video of an F-16 student's HUD, where a student flying on the wing at night, becomes spatial D when he goes lost wingman (loses sight of lead and so has to separate). He turns away, rotates his head forward...and immediately gets spatial D, to the point where he starts doing aileron rolls...even though he's looking through the HUD actively trying not to. He was smart enough to transmit to lead (his IP) that he was SD, and his IP very calmly but firmly was able to direct him to his standby attitude indicator, where at that point he was able to recover.
I've had friends tell me about being spatial D on the tanker...thinking they were refueling inverted. It takes a LOT of effort to deliberately override what you feel when your outside references are fuzzy or non-existent.
FC
