The helicopter pilot entered an area of dense clouds and experienced spatial disorientation due to weather, according to investigators. Spatial disorientation is an aviator’s inability to determine angle, altitude or speed. AdNTSB accident data suggests that spatial disorientation may be a precursor to many general aviation accidents, particularly in night or limited visibility weather conditions. Instrument and VFR pilots are subject to spatial disorientation and optical illusions that may cause loss of aircraft control. It’s unsettling to think about, but the NTSB says all pilots at sometime or another will experience spatial disorientation.