Originally Posted by
EK773ER
For example, if the minimum visibility required for the approach is 5km from the approach plate, then how do you calculate actual slant range required at minimums?
Well, there's some things that don't quite add up about your question, but as a practical matter, for approaches the difference between horizontal distance and slant range is too small to even be displayed on cockpit displays.
If you had a required visibility of 5km for an approach (what sort of approach is that?) If you were 5 km from the runway , you should be at an altitude fairly close to a 3 degree glideslope. That would mean that you'd be at about 262 meters altitude, the slant range from your airplane to the runway would be 5006.8 meters ( the square root of 5000 squared plus 262 squared) So the difference between horizontal and slant distance is 6.8 meters or about 0.003 NM. Cockpit displays of distance are typically only to a tenth of a NM ( XXX.1 NM) so the difference it not only too small to worry about, it's too small to even *see* when you're flying.