Aeronautical Information Manual (AIM), page 355
11/10/16 12/10/15 AIM is not authorized due to an obstacle penetration that VDA. The VDA and TCH information are charted on would require a pilot to deviate from the VDA the profile view of the IAP following the fix between MDA and touchdown, the VDA/TCH will (FAF/stepdown) used to compute the VDA. If no be replaced with the note "Visual Segment- PA/APV IAP is established to the same runway, the Obstacles" in the profile view of the IAP (See VDA will be equal to or higher than the glide path FIG 5-4-13). Accordingly, pilots are advised to angle of the VGSI installed on the same runway carefully review approach procedures to identify provided it is within instrument procedure criteria. A where the optimum stabilized descent to landing can chart note will indicate if the VGSI is not coincident be initiated. Pilots that follow the previously with the VDA. Pilots must be aware that the published descent angle below the MDA on published VDA is for advisory information only and procedures with this note may encounter obstacles in not to be considered instrument procedure derived the visual segment. vertical guidance. The VDA solely offers an aid to 2. The threshold crossing height (TCH) used to help pilots establish a continuous, stabilized descent compute the descent angle is published with the during final approach.FIG 5-4-13 Example of a Chart Note 3. Pilots may use the published angle and rate based on the VDA may exceed the capabilities of estimated/actual groundspeed to find a target rate of the aircraft and the pilot must determine how to best descent from the rate of descent table published in the maneuver the aircraft within the circling area in order back of the U.S. Terminal Procedures Publication. to land safely. This rate of descent can be flown with the Vertical l. In isolated cases, an IAP may contain a pub- Velocity Indicator (VVI) in order to use the VDA as lished visual flight path. These procedures are an aid to flying a stabilized descent. No special annotated "Fly Visual to Airport" or "Fly Visual." A equipment is required. dashed arrow indicating the visual flight path will be included in the profile and plan views with an approx- 4. A straight-in aligned procedure may be imate heading and distance to the end of the runway. restricted to circling only minimums when an excessive descent gradient necessitates. The descent 1. The depicted ground track associated with the angle between the FAF/stepdown fix and the Circling "Fly Visual to Airport" segment should be flown as MDA must not exceed the maximum descent angle a "Dead Reckoning" course. When executing the allowed by TERPS criteria. A published VDA on "Fly Visual to Airport" segment, the flight visibility these procedures does not imply that landing straight must not be less than that prescribed in the IAP; the ahead is recommended or even possible. The descent pilot must remain clear of clouds and proceed to the Arrival Procedures 5-4-19
Page 355 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures