I've noticed check altitudes being added to some FAA and foreign LPV and GLS Instrument approaches. I can understand the purpose of a check altitude on an ILS where an independent Glide Slope intersects a geographical fixed point and the altitude over this point should never change. So your barometric altimeter should closely correspond to that altitude at that point if you are on Glide Slope. But with the LPV and GLS approaches the Glide Slope is derived internally within the aircraft. Integrity checks are constantly comparing satellite altitude to barometric altimeter altitude and monitoring for deviation. Since the Aircraft GPS box is computing the altitude along your route of flight and with auto pilot engaged flying to the computed fix points and maintaining the altitude associated with each fix, what is the purpose of a Check Altitude along final approach? Without any warning flags indicating a deviation, your system should put you at that fix and at that altitude every time.
Comments?
Comments?