Capn Bloggs Re GS check – “That happens at the OM …”
The primary purpose of markers / fix (or distance) checks during an approach is to determine the ‘acceptability’ of the vertical approach path / confirm your location with respect to that path. For safety, where a check involves altitude and distance, the altitude must take priority – it’s the early contact with ground that you wish to avoid, not the determination of distance to the airfield.
Dream Land states the required safety defence, check the altitude first and do not descend below it until the appropriate ‘fix’. In the specific case of an ILS I would suggest a climb, then determine the cause of the discrepancy – don’t trouble shoot at minimum altitudes, and don’t continue with an alternative procedure by assuming that the LOC (and your position relative to the airport) is correct – climb, check, rebrief, and recommence the approach. Beware the unexpected / unexplained; if the EGPWS alerts / warns - climb.
uncle dickie, you probably meant the above, but stating the check correctly (altitude vs distance tables) might aid correct use as well as recalling the check from memory, thus avoiding any complacency / omission of routine actions and checks.
Safety examples
‘EPGWS events and analysis’.
Also see
‘Thai Air B777 Melbourne NDB approach’.