Re: Odd approach with LNAV/VNAV minima higher than LNAV mini
AIM 5-4-5. Instrument Approach Procedure Charts
i. Vertical Descent Angle (VDA) on Nonprecision Approaches.
5. In rare cases the LNAV minima may have a lower HAT than minima with a glide path due to the location of the obstacles. This should be a clear indication to the pilot that obstacles exist below the MDA which the pilot must see in order to ensure adequate clearance. In those cases, the glide path may be treated as a VDA and used to descend to the LNAV MDA as long as all the rules for a nonprecision approach are applied at the MDA. However, the pilot must keep in mind the information in this paragraph and in paragraph 5-4-5j.
k. Area Navigation (RNAV) Instrument Approach Charts.
1. The minima lines are:
(b) LPV. "LPV" is the acronym for localizer performance with vertical guidance. LPV identifies WAAS APV approach minimums with electronic lateral and vertical guidance. The lateral guidance is equivalent to localizer and the protected area for LPV procedures is now the same as for an ILS. The obstacle clearance area is considerably smaller than the LNAV/VNAV protection, allowing lower minima in many cases. Aircraft can fly this minima line with a statement in the Aircraft Flight Manual that the installed equipment supports LPV approaches. This includes Class 3 and 4 TSO-C146 WAAS equipment.
(c) LNAV/VNAV. LNAV/VNAV identifies APV minimums developed to accommodate an RNAV IAP with vertical guidance, usually provided by approach certified Baro-VNAV, but with lateral and vertical integrity limits larger than a precision approach or LPV. LNAV stands for Lateral Navigation; VNAV stands for Vertical Navigation. This minima line can be flown by aircraft with a statement in the Aircraft Flight Manual that the installed equipment supports GPS approaches and has an approach-approved barometric VNAV, or if the aircraft has been demonstrated to support LNAV/VNAV approaches. This includes Class 2, 3 and 4 TSO-C146 WAAS equipment. Aircraft using LNAV/VNAV minimums will descend to landing via an internally generated descent path based on satellite or other approach approved VNAV systems. Since electronic vertical guidance is provided, the minima will be published as a DA. Other navigation systems may be specifically authorized to use this line of minima, see Section A, Terms/Landing Minima Data, of the U.S. Terminal Procedures books.
(e) LNAV. This minima is for lateral navigation only, and the approach minimum altitude will be published as a minimum descent altitude (MDA). LNAV provides the same level of service as the present GPS stand alone approaches. LNAV minimums support the following navigation systems: WAAS, when the navigation solution will not support vertical navigation; and, GPS navigation systems which are presently authorized to conduct GPS approaches. Existing GPS approaches continue to be converted to the RNAV (GPS) format as they are revised or reviewed.