Definition
A notation on an instrument approach chart indicating that a published vertical descent angle (VDA) is not authorized or not provided for the non-precision approach procedure. When 'Descent Angle NA' appears, pilots cannot use a stabilized constant-angle descent path computed from the chart and must instead fly the approach using the published step-down fixes and minimum altitudes.
Plain English
It means the chart is telling you: there's no published descent angle for this approach. You have to fly it the old-fashioned way, stepping down from one minimum altitude to the next at the points shown on the chart.
Context Anchor
Seen on instrument approach charts and in vertical navigation discussions, especially when reviewing the profile view of an approach.
Derivation
Descent means going downward, and angle means the slant of a path. On FAA procedures, NA means Not Authorized. Together, the phrase means the downward slant path is not approved for use on that procedure.
Why Pilots Care
Using a descent angle marked NA can result in loss of obstacle clearance or deviation from the protected path.
Grounding Statement
If the chart says Descent Angle NA, fly the published altitude steps instead of inventing a smooth glide path.
Intuition Check
NA does not mean “not available, but you can make your own.” In this context, it means the descent angle is not authorized for use.
Example Sentence 1
During the approach briefing, the captain noted 'Descent Angle NA' on the plate and reminded the first officer they would fly step-downs to each fix rather than a constant-angle descent.
Example Sentence 2
Pilots must select an alternate descent method when the chart indicates Descent Angle NA.