Although they look alike, there is a world of difference between ILS, LNAV+V and LNAV/VNAV glidepaths. It turns out that not all glidepaths are created equal.
Advisory glidepaths on non-precision approaches (LNAV+V) are not guaranteed obstacle-clear below the Minimum Descent Altitude (MDA), posing a safety risk if pilots mistake them for precision approach glidepaths.
The FAA is addressing this hazard by removing Visual Descent Angle (VDA) information from approach charts where obstacle clearance below the Missed Approach Point (MAP) is not assured, impacting the availability of continuous descent operations.
Pilots must recognize that advisory glidepaths are purely advisory below the MDA and they retain full responsibility for obstacle clearance, as GPS navigators display the glidepath to the runway threshold without knowledge of minimums.
In March, we examined the hazard of following a non-precision visual descent angle (VDA) below the MDA. This is easy to do because flying a non-precision approach with an advisory glidepath looks similar to an ILS, LPV or LNAV/VNAV with a real glidepath.
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