Originally Posted by
dmhpilot
A little secret:
All VNAV paths are curved. This is why there are temperature limits. The curve (because all GPS satellite orbits are a curve when considered two dimensionally) is negligible on a standard day but steepens on a hotter day and shallows on a cooler day.
Once you go past the approved temperature limits, the curve is either too steep or too shallow to make a safe transition to landing at the DA/MDA.
I don't think the VNAV on the 737 uses GPS to calculate it. It just uses math and barometric altitudes. VNAV should work even without GPS signal I would think.