FAA Proposes New Rules For Enhanced Vision System Approaches

 - July 1, 2013, 4:05 AM
The proposed rule could make it possible for suitably equipped and trained operators to continue approaches below current conventional minimums.

A new set of FAA regulations signals the agency’s intent to make installation of an enhanced flight vision system (EFVS) far more worthwhile and less burdensome, with new capabilities such as flight to touchdown in below-minimums visibilities, dispatch to below-minimums airports for commercial operators and a framework for certification that eliminates the need for special conditions.

The notice of proposed rulemaking (NPRM) would allow many more operators to enjoy the chief advantage of purchasing a new business jet with EFVS or negotiating for inclusion of EFVS in an airliner fleet: the ability to continue flying below decision altitude/decision height or minimum descent altitude (DA/DH or MDA) during IMC without the pilot being able to see visual references using natural vision.

Most significantly, the new rules would allow commercial operators flying EFVS-equipped aircraft to dispatch and depart, then fly approaches even if the visibility at the destination is below authorized minimums, providing a major incentive for airlines, charter and fractional operators to install EFVS. There could also be benefits for takeoff in visibility lower than currently permitted; however, this is something that the FAA can already allow on a case-by-case basis for EFVS-equipped operators. The NPRM might open the door to more of these types of operation as it seems to signal the agency’s increasing comfort with the use of EFVS.

The benefits of this NPRM may even cascade into the retrofit market and give new incentives to manufacturers to offer competitive products. For the most part, EFVS is available on new aircraft and not as a retrofit on existing business jets. Rockwell Collins’s Head-up Guidance Systems division in Portland, Ore., is the primary source of the head-up display that is a key element in EFVS, but HUD manufacturers Elbit and Saab may find that the new regulatory framework proposed by the FAA ushers in a newly competitive landscape. In fact, HUD isn’t the only means of presenting EFVS imagery to pilots, and the NPRM could accelerate the adoption of new technologies into non-military cockpits.

The proposed new rules define EFVS as an “installed aircraft system, which uses an electronic means to provide a display of the forward external scene topography (the applicable natural or man-made features of a place or region especially in a way to show their relative positions and elevation) through the use of imaging sensors, such as forward-looking infrared, millimeter-wave radiometry, millimeter-wave radar or low-light-level image intensification.” The broad description of the technologies involved holds open the possibility for future innovations that might lead to further improvements in the ability to “see” through dense fog. Current infrared-based sensor technology has some limits in areas of dense moisture such as heavy fog.

Performance-based Rulemaking

In a major departure from the way it normally does business, the FAA wrote the NPRM using “regulatory language that is performance-based and not limited to a specific sensor technology.” According to the FAA, “this action would accommodate future growth in real-time sensor technologies used in most enhanced vision systems. The proposal would maximize the benefits of rapidly evolving instrument approach procedures and advanced flight-deck technology to increase access and capacity during low-visibility operations.”

EFVS generally use infrared sensors to deliver real-time images of the external view to cockpit displays, and the new rules would not apply to synthetic vision systems, which rely on database-, navigation- and attitude-derived depictions of the outside world. The NPRM further defines EFVS as displaying imagery from sensors on a HUD “or an equivalent display, so that the imagery and symbology is clearly visible to the pilot flying in his or her normal position with the line of vision looking forward along the flight path. An EFVS includes the display element, sensors, computers and power supplies, indications and controls.”

The words “an equivalent display” may also offer opportunities for development of other methods of displaying information to pilots. Honeywell, for example, doesn’t manufacture HUDs and is focused on delivering sensor imagery on head-down displays mounted in the instrument panel. If it can be shown that the use of head-down displays is equivalent to a HUD, then it may be possible someday to offer similar capabilities without a HUD.

The impetus behind issuing this proposed set of rule changes, according to the FAA, is to “take advantage of advanced vision capabilities, thereby achieving the NextGen goals of increasing access, efficiency and throughput at many airports when low visibility is the limiting factor. Additionally, it would enable EFVS operations in reduced visibilities on a greater number of approach procedure types while maintaining an equivalent level of safety.”

The rule does not, as some believe, sanction landing in zero-zero conditions; the visibility that applies to the approach is still a limitation, although efforts are under way to reduce the lower limit to 300 feet RVR at some point. All that changes is that pilots flying EFVS-equipped aircraft will use that equipment to determine that visibility is at or above minimums to fly the approach and to identify required visual references to continue descending below DA/DH or MDA all the way to the ground, as long as the pilot can see these visual references using EFVS. Essentially, the pilot flying will be using EFVS instead of natural vision. The FAA calls this “enhanced flight visibility.”

Currently, in aircraft equipped with EFVS pilots can descend below minimums using visual references viewable on EFVS, but only when operating under Part 91 to 100 feet above touchdown-zone elevation. Natural vision is required for the remaining 100 feet and landing. In aircraft without EFVS, of course, pilots must use natural vision for all segments of the approach, and especially by looking outside during the final 200 feet above touchdown.

Only approaches with published straight-in minimums, a published vertical path and DA or DH will qualify for EFVS operations to touchdown and rollout, and non-precision approaches would not be permitted. While current Part 121 and 135 regulations require tire contact within the touchdown zone, the new rules add that requirement for all EFVS operators. As the NPRM states, “the descent rate would allow touchdown to occur within the touchdown zone of the runway of intended landing.”

The FAA would also mandate specific training and recency of flight experience requirements for conducting EFVS operations, applicable to all types of operator. Additionally, EFVS would be permitted for use during Category II and III approaches. HUD systems would also be subject to new regulations covering HUD installations. This would eliminate the need to apply special conditions to certify HUD installations as is currently done, a process that makes certification more costly and time-consuming.

Combined Vision Applications

This NPRM holds out hope for makers of so-called combined vision systems, which overlay infrared sensor and synthetic vision imagery on one display. While the NPRM covers only EFVS with a “transparent display surface located in the pilot’s outside view, such as a head-up display, head-mounted display or other equivalent display,” Honeywell still sees opportunities for its technological approach.

Honeywell has been working on combined vision for many years, shown on a head-down display instead of a HUD. “Honeywell is working closely with the FAA to extend the use of our head-down combined vision system [CVS] to 100 feet above the threshold elevation,” Honeywell vice president of government relations Chris Benich told AIN. “We will continue to work with the FAA and our customers to expand operational benefits as these technologies evolve. Honeywell’s CVS incorporates all the information required for the pilot to have an unobstructed view of the environment in his normal seating position along the line of sight looking forward along the flight path, on the head-down display. CVS will allow the pilot always to have a clear view to enhance safety and operational efficiency.

“Honeywell has been working on CVS for several years collecting data in the aircraft and in level-D simulators, and those research findings indicate that pilot performance down to 100 feet is equivalent with head-up EFVS and the head-down CVS display. In addition, CVS provides improved situational awareness, with a clear indication of terrain, obstacles, landmarks and threats on the flight display for an enhanced flight experience.”

Comments on the NPRM are due by September 9. The NPRM can be viewed at www.regulations.gov; search for Docket No. FAA–2013–0485.