Have to quibble with BPs statement re relationship between 1 mb and vertical distance:
Quote:
1 mb = 30 feet (actually a little less than that, and a lot less once you go higher up)
BP is right that 1 mb (15 C, 1013.2 mb) is a little less than 30 FT (27 FT), but the vertical distance per mb becomes greater with increasing altitude:
1 mb = 37 FT @ 10000 FT,
1 mb = 48 FT @ 18000 FT,
1 mb = 58 FT @ 24000 FT,
1 mb = 104 FT @ 39000 FT, all of course assuming ISA applies through the depth.
Of course, if BP meant that for a constant depth of 30 FT, the pressure difference becomes less with increasing height, then BP would be correct - but I didn't quite read it like that.
I recall in ATPL, the relationship 96T/P (T= temperature in Kelvin, P = Pressure in millibars) would give the vertical distance in feet for 1 mb. Multiply by however many millibars you want a vertical distance for, but it is only valid for 'small changes in pressure' - so should be valid for 1 or 2 mb difference I would have thought.
Cheers,