Mutt,
Yep, nearly added cheeky remark 'bout your location to original post
- not really that much of a prob around that corner of the world.
Regarding the altimeter correction - well, ISA-10 deg. equals 4% of the height AAL, so 1000 ft. would give you round 40 ft. The reason it divergers so quickly is - as I'm sure you know (not teaching anyone to suck eggs here
) - that the surface does not contract perceptibly with lower temp, but air does. So even down to ISA-50, your altimeter should still indicate corretly on the ground, but when you passed 1000 ft. AAL indicated, you would actually only be 800 ft. AAL geometrically (4% /10 deg. x 5 = 200 ft.).
vikena,
Only applies in mountaineous (sp?) areas - when the wind moves over a range at high speed, local areas of low pressure may be formed behind, between or over ridges (depending on their actual shape). If transiting such an area, you could be somewhat lower than what your altimeter indicates. I don't think that the effect propagates all the way to a typical cruise level, but if you had to descent into such an area (e.g. decompress), you would feel the effect when approaching the MEA/MORA.
...eeeerrrr....I...eerrr...think
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