extending the centre line

[cheakymunkie]

Hi guys...

In the 737NG, after extending the centre line in the FMC what does the vertical path indicator show exactly. Is it how high or low you are relative to a 3 degree glide path from the runway to the point from which you extended, then from that point to your current position?

When I extend the centreline on base it aways seems to show a few hundered feet high when this is not the case. It's got me wondering if maybe I'm not understanding this function properly.

Thanks...

[airborneforever]

what i understand is that it shows you a descent path from your present position to the first point in the fmc at the active descent speed in the fmc and thereon to the runway at the glide angle specified.