A little clarification requested here WRT an ILS...
AIP ENR1.5.5.1.1 (!)
A pilot must not take off or, except in an emergency, land or continue an approach below the prescribed DA, MDA or RH for the approach being conducted when any element of the prescribed meteorological criteria is continuously less than the minima for the aircraft performance category (CAR 257).
(my bold)
There is no definition for RH in
AIP GEN 2.2.2 There is however a defintion of Radio Height in the definitions of
AIP GEN 2.2.1
Now if we were to use this RH (published on our DAP IAL charts in non bold to the right of the DH) as our DH (as the first quoted reg implies) and:
1. This RH is the height above ground
beneath the aircraft
2. The RH appears to be predicated on the difference between the threshold elevation and the DH
3. The DH is displaced (for cat 1 anyway) about .5nm from the threshold of the runway.
What about the case where the ground slopes down from the threshold of the runway? Could not this lead you to initiate your missed approach below the DH? Or is this already factored in? Or am I splitting hairs?
Then I ask the question again with respect to an non-precision approach. There the MDA is often a mile or more from the threshold where there is every chance that the terrain slopes up or down from the airport.
CS