[singpilot]

An interesting thread came up on one of the airline sites the other day.

When the 747 frst came out, the specifications for the technical standards for an instrument approach on the ILS (precision) landing system had to be rewritten. Seems the glidepath clearance zone (both vertical and lateral) needed to be 'adjusted'.

The glidepath was flown assuming maximum observable deviation, and a fudge factor thrown in. All the physical obstructions were charted and/or cleared so that a slightly below course aircraft would still not hit anything reasonably under the electronic glidepath. In landing attitude, the largest then aircraft had a pilot's eye to landing gear height of 25 feet, give or take. Sitting on the ramp, the 747 was 55 feet to the pilots' eye. In landing attitude, that grew to almost 70 feet in height for the -400.

Along comes the (long) A340 and now (long and big) A380. It was time for another 'adjustment'.

Airports all over the world are 'adjusting' their procedures and minimums to be ready.

Yes, some adjustment is cranked in electronically to the displayed glidepath in the jumbos in accordance to some spec somewhere.