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procedures also may have nonstandard features such as nonstandard final approach course alignment, nonstandard descent gradients, or other features that may or may not be compatible with the conduct of EFVS operations. 

Under § 91.176(a), operators who have been issued OpSpec C073, MSpec MC073, or LOA C073, may conduct EFVS operations to touchdown and rollout on certain vertical navigation (VNAV) IAPs that use an MDA as a DA/DH in accordance with C073. Additionally, §§ 91.176 and 91.189 permit an authorized EFVS operation to be conducted during an authorized Category II or Category III operation. 

Currently, EFVS operations in rotorcraft can be conducted only on IAPs that are flown to a runway. Instrument approach criteria, procedures, and appropriate visual references have not yet been developed for straight-in landing operations below DA/DH or MDA under IFR to heliports or platforms. EFVS cannot be used in lieu of natural vision to descend below published minimums on copter approaches to a point-in-space (PinS) followed by a “proceed visual flight rules (VFR)” visual segment, or on approaches designed to a specific landing site using a “proceed visually” visual segment. 

## Vertical Navigation 

One of the advantages of some GPS and multi-sensor FMS RNAV avionics is the advisory VNAV capability. Traditionally, the only way to get vertical path information during an approach was to use a ground-based precision NAVAID. Modern RNAV avionics can display an electronic vertical path that provides a constant-rate descent to minimums. 

Since these systems are advisory and not primary guidance, the pilot must continuously ensure the aircraft remains at or above any published altitude constraint, including step ­ down fix altitudes, using the primary barometric altimeter. The pilots, aircraft, and operator must be approved to use advisory VNAV inside the FAF on an instrument approach. 

VNAV information appears on selected conventional nonprecision, GPS, and RNAV approaches (see “Types of Approaches” later in this chapter). It normally consists of two fixes (the FAF and the landing runway threshold), a FAF crossing altitude, a vertical descent angle (VDA), and may provide a visual descent point (VDP) [Figure 4-11A]. 

The VDA provides the pilot with advisory information not previously available on nonprecision approaches. It provides a means for the pilot to establish a stabilized descent from the FAF or step-down fix to the MDA. Stabilized descent is a key factor in the reduction of 

controlled flight into terrain (CFIT) incidents. However, pilots should be aware that the published angle is for information only − it is strictly advisory in nature. There is no implicit additional obstacle protection below the MDA. Pilots must still respect any published stepdown fixes and the published MDA unless the visual cues stated 14 CFR § 91.175 are present, and they can visually acquire and avoid both lit and unlit obstacles once below the MDA. The presence of a VDA does not guarantee obstacle protection in the visual segment and does not change any of the requirements for flying a nonprecision approach. 

Pilots may use the published angle and estimated/actual groundspeed to find a target rate of descent from the rate of descent table published in the back of the U.S. Terminal Procedures Publication. This rate of descent can be flown with the Vertical Velocity Indicator (VVI) in order to use the VDA as an aid to flying a stabilized descent. No special equipment is required. 

In rare cases, the LNAV minima may have a lower HAT than minima with a glide path, due to the location of the obstacles and the nonprecision MAP. This should serve as a clear indication to the pilot that obstacles exist below the MDA, which must be seen 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 of the rules for a nonprecision approach are applied at the MDA. 

When there are obstacles in the visual area that could cause an aircraft to destabilize the approach between the MDA and touchdown, the IAP will not show a vertical descent angle in the profile view. The charts currently include the following statement: “Descent Angle NA” or “Descent Angle NA-Obstacles” [Figure 4-11B ]. 

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