Capn Bloggs
Quote:
Originally Posted by A Squared
Turns out that a obstacle clearance plane of 2.2degrees would give a clearance of about 65 feet to an airplane exactly on a 3.2 degree PAPI, 3700 ft from the threshold. That's remarkably close to the clearance from the terrain which JC figured using Google earth. Granted, the first point of impact was quite a bit further out and lower than this, so this is only peripherally related to the accident. However it is interesting to note how little clearance you might have over a half mile from the threshold and perfectly centered on the PAPI.
This is ridiculous. How could such an approach be allowed, especially at night, with such little terrain clearance? The threshold crossing height is 50ft; 6000ft/1nm further back, you only have another 50ft higher (100ft in total) to give 2W/2R on the PAPI, with wheels hanging probably 30ft below that?
And as Airbubba raised a lot earlier in the thread, the small vertical error margin does make altimeter setting something to return to - the difference between 29.92 and BHM QNH 29.97 just happens to be 50ft low - "with wheels hanging 30ft below that".