Originally Posted by
Fareastdriver
Point taken on ACR 7s, internal radar approaches,, etc, but they don't do that any more, do they?????
Quite although we did practise internal approaches even less than 20 years ago. No, I was trying to find an historic rationale rather than justify its use now.
Another reason could be the lack of good mapping and consequently an inaccurate calculation of surface pressure. Set the altimeter to zero and at least you know it will read the same when you get back - slow moving weather systems.
Or how about air-to-ground weaponry? Again you needed to know your height above the target.