Altimeter Checks
With reference to ENR 1.5 and the issue of Altimeter Checks for an ILS. AIP states:
"If the check indicates an unexplained discrepancy, the ILS should be discontinued."
My question is, how much is considered to be abnormal? Assuming of course you apply common sense and say, "well I'm half a dot high therefore I expect the altimeter wont read exactly the altimeter reading as marked on the plate" I'm aware of the effect of very low temperature and the old "if you're low you're good to go" adage but just saying an unexplained discrepancy is a little vague an answer to give to my IRE.