ILS App. Outer marker - glide slope, altimeter checked!
During an ILS approach, the outer marker is used as a check of the pressure altimeter, assuming one is on loc and on slope...agreed?
I understand that the nominated height is predicated on an ISA day.
If the height over the OM is, say, 100 feet low - let's use the figure on the Jepps as 1500', and the actual on the Press Alt reads 1400 - by how much should the minima be adjusted? Let's use a minimum of 300'.
Should it be adjusted by 100', or 1/5 of 100'? [ie. 300' is 1/5 of the check height of 1,500', therefore the 100' difference @ 1,500'= 20'@300']