Good point, FD - I always get that 'pressure decreasing / altitude increasing' thing mixed up! It's amazing I'm allowed anywhere near an aeroplane in the first place...
MnT - I wondered if that might be the answer, but I'm pretty sure that the static port on a C152 isn't at a stagnation point... it's in the prop-wash, for a start. Looking forward to hearing from Genghis....
cbl.