After changing the rules to allow the use of enhanced flight vision systems (EFVS) instead of natural vision to descend below 100 feet above touchdown zone elevation (TDZE) then land and roll out, the FAA has now published Advisory Circular (AC) 90-106A to explain how operators can use the new regulations. EFVS was first allowed in January 2004, allowing pilots to fly to 100 feet above TDZE using approved EFVS, typically infrared sensor-derived imagery projected on a head-up display (HUD). The pilot then had to use natural vision to land and roll out.
The original rule offered a huge advantage for EFVS-equipped airplanes, as pilots could often land in poor weather using ordinary Cat I ILS approaches, without having to meet the complex training and equipage requirements for Cat II and III approaches.
The new rule, issued on December 16 last year, makes EFVS equipment even more valuable, because it allows pilots to continue past 100 feet to touchdown and rollout, flying the airplane, but looking through the HUD and seeing the approach lights and runway lights and markings as EFVS imagery. Notably, the new rule does not specify the type of sensor required in an EFVS, leaving it to industry to develop and certify new technology that may replace infrared sensors or use them in new ways, or married to other sensors that help the pilot see the runway and its environment. While the old rule required a HUD, the new rule allows other types of image-delivery mechanisms, leaving the door open for new products such as wearable HUDs. Head-down displays (instrument panel displays) cannot be used for EFVS operations, however, except that the copilot in a two-pilot aircraft can use a head-down display to monitor the pilot’s view through the HUD.
According to the AC, “We have made every attempt to write EFVS regulations that are performance-based and not limited to a specific sensor technology. The regulations accommodate future growth in real-time sensor technologies used in most EFVSs and maximize the benefits of rapidly evolving instrument approach procedures (IAP) and advanced flight-deck technology to improve safety and access during low-visibility operations.”
Approaches that meet the criteria for EFVS operations to touchdown and rollout include standard IAP or special IAP with a decision altitude (DA) for precision approaches, or decision height (DH) for approach procedures with vertical guidance (APV). In some cases, pilots may also fly certain non-precision approaches (those that use a minimum descent altitude as a DA/DH) using EFVS, with OpSpec C073, MSpec MC073 or LOA C073 approval.
EFVS operations are not permitted for circling approaches, so pilots can’t use EFVS to view “an identifiable part of the airport” to descend below minimum descent altitude (MDA); they must use natural vision. However, the AC does go on to note that pilots can use the EFVS “to supplement natural vision and improve situational awareness at any time.”
It should be noted that the enhanced visibility facilitated by the EFVS cannot be less than the visibility specified for the particular approach procedure.
Operators might need specific approvals for EFVS operations. Part 91 operators are not required to obtain approval for operations to 100 feet above TDZE, but they will need approval—OpSpec, MSpec or letter of authorization (LOA)—for EFVS operations to touchdown and rollout. Commercial operators (91K, 121, 125, 129 or 135) need OpSpec, MSpec or LOA approval for both types (to 100 feet and rollout/touchdown).
An added benefit for commercial operators is that they can receive approval for dispatching or releasing a flight with low takeoff minimums and “beginning or continuing an approach when the visibility is reported to be less than the visibility minimums prescribed for the IAP to be flown.”