In the "real world" you need a "general safety rule", and that is that you can't commit the aircraft to IMC until you know what is providing your terrain clearance guarantee.
LSALT provides your terrain clearance en route.
The mnemonic "25, 30, VIRD" gives you your terrain clearance for your descent.
within 25 miles I can use the MSA, within 30 miles by day I can proceed visually, on VASI within 5/7 miles, on an Instrument approach, on Radar vectors, on a DME/GPS arrival.
In the real world, however, a lot of people forget about what is providing terrain clearance on their departure.
At a major airport, the SID gives you terrain clearance, at a standard 3.3% (unless specified otherwise on the chart). At, say 90 knots, that's a required vertical speed of 300 fpm.
At a typical bush aerodrome (say with an aid and approach) on a bad weather day with an IFR plan, many pilots take off into cloud (because they are "IFR") and climb out en route, not thinking about what is guaranteeing their terrain clearance up to the LSALT.
Last edited by Checkboard; 13th June 2012 at 13:33.