Definition
In VNAV procedures, the published descent angle of a glidepath measured between the descent track and the horizontal plane, expressed in degrees and tenths (for example, 3.00°). It defines the rate at which the aircraft descends along the geometric path between two specified altitudes or fixes.
Plain English
It is the steepness of the descent path, given as an angle below level flight. A larger number means a steeper descent; a smaller number means a shallower one.
Context Anchor
Seen in VNAV planning, especially when checking a planned descent path from one altitude to another.
Derivation
From Latin verticalis, meaning 'overhead' or 'relating to the highest point,' and angulus, meaning 'corner' or 'angle.' Together the phrase describes an angle measured against the up-and-down reference of the horizon, which is exactly how a descent path's steepness is specified.
Why Pilots Care
It lets the pilot or automation calculate the exact descent rate needed to stay on the safe vertical profile to the runway.
Grounding Statement
Picture the descent path as a straight sloping line from the airplane to a lower point ahead; the vertical angle is the steepness of that line.
Intuition Check
Vertical angle does not mean a straight-up-and-down path. In this context, it means the angle of a sloped flight path compared with level flight.
Example Sentence 1
The approach chart shows a vertical angle of 3.00° from the final approach fix to the runway threshold.
Example Sentence 2
Entering the correct vertical angle into the FMS allowed the aircraft to meet the crossing restriction at the next waypoint.