Originally Posted by
C130driver
Nope, VDP (visual decent point,) often published on a non precision approach indicating the point from which you should start your decent from MDA to assume a normal glidepath to the runway. Lack of a VDP means that there are obstacles in the protected zone of that glide path. It's a lawyerism for sure.
Just to be sure that everyone else reading this thread gets the difference too:
VDP (from the 8260.3G TERPS)
253. VISUAL DESCENT POINT (VDP). The VDP
defines a point on an NPA procedure from which
normal descent from the MDA may be commenced
provided the required visual references have been
acquired.
ESTABLISH A VDP FOR ALLSTRAIGHT-IN NPA PROCEDURES (to include those combined with a PA/APV procedure), with the
following exceptions/limitations:
�� Do not publish a VDP when the primary
altimeter setting comes from a remote
source.
�� Do not publish a VDP located prior to a
stepdown fix.
�� If the VDP is between the MAP and the
runway, do not publish a VDP.
�� Do not publish a VDP when the 20:1 surface
is penetrated (Vol. 1, chapter 3, paragraph
3.3.2d).
�� When feasible, the VDP should be ≥ 1NM
from any other final segment fix (e.g., MAP,
stepdown). When not feasible, the VDP
must be at least 0.5 NM from any other final
segment fix. If < 0.5 NM and the other fix
cannot be relocated, do not publish a VDP.
DO NOT increase the MDA to achieve the
≥ 0.5 NM distance.
Also - limitations:
3.3.2 c. (2) (b) 20:1 OIS. If penetrated, take the following action:
Lighted Obstacles: Do not publish a VDP and limit visibility to no lower than 5000 RVR or 1 SM.
Unlighted Obstacles: Do not publish a VDP, limit visibility to no lower than
5000 RVR or 1 SM, and annotate the chart denying the approach or applicable
minimums at night.
VDA (from the same reference)
252. VERTICAL DESCENT ANGLE. Vertical
descent angle (VDA) is normally used in this segment
for non-precision procedures. Determine the VDA for
all NPA procedures except those published in
conjunction with vertically-guided minima or no-FAF
procedures w/out stepdown fix(es). See applicable
chapters/directives for guidance on no-FAF or
procedures published with PA and APV minima.
Optimum VDA is 3.00 degrees. Where operationally
feasible, design straight-in NPA procedures (all CATs)
to achieve a VDA equal to the commissioned angle of
an installed visual glideslope indicator (VGSI) if within
the standard VDA range. When a VGSI is not
installed or not within the standard range, or final is
circling aligned, design procedures at the optimum
VDA when possible or within the following range:
STANDARD VERTICAL DESCENT ANGLES
FAA 2.75°-3.77° (IAPS w/ ≤ CAT C mins)
2.75°-3.50° (IAPS w/ CAT D/E mins)
USAF 2.50°-3.50° (All IAPS)
USN 2.50°-3.77° (All IAPS)
Note 1: Minimum VDA N/A to circling only
procedures.
Realize that these VDA are mathematical calculations and do not necessarily provide obstacle clearances in the visual segment of the approach.
From the 8260.19G
(a) Do not publish a VDA/TCH when Flight Inspection has requested that one not be established due to an obstacle that would require an aircraft to deviate from its vertical flight path prior to reaching the TCH.
(b) When the condition in paragraph 8-6-8.s(1)(a) has occurred, a chart note must be placed in the profile view of the chart to alert the pilot that should an avionics manufacturer provide an advisory vertical angle in the database, the path below the MDA to the runway is not clear of obstacles; use "Chart profile note: Visual Segment – Obstacles."
Note that the VDA will still be coded into the database, but the requirement (which it always was) to avoid obstacles is the pilot's responsibility.