Vision in Vogue: Synthetic vision systems the new norm

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Gulfstream's Synthetic Vision, primary flight display for high-end Gulfstream business jets, gives pilots a day-time computer-generated view of terrain ahead

Avisual landing in mountainous terrain on a blustery, moonless, wintry night, with smoke from nearby wildfires thrown in, can be a compelling sales case for a computer-generated daylight visual scene in the cockpit.

Flight International experienced how such a synthetic vision system (SVS) enhanced comfort levels and situational awareness during a night flight on 11 February in just such conditions aboard a Gulfstream G450 equipped with the company's Synthetic Vision Primary Flight Display (SV-PFD), an exotic tool that greatly eased the task at hand. SV-PFD is based on Honeywell's synthetic vision product, known as the Integrated Primary Flight Display (IPFD).

gulfstream synthetic vision
 © Gulfstream

Although difficult to quantify, there was no question the operation was aided by being able to see mountains and valleys out to 65km (35nm) ahead lit in synthetic midday sun on a 14in (355mm) flat-panel display showing a 44° wide side-to-side field-of-view display front and centre.

Siren Song

The real estate outside the windscreen might as well have been non-threatening dark open space, a potential siren song for a controlled flight into terrain accident. Adding to the presence of mind on the SV-PFD were "breadcrumbs", dots leading along a 28km path to a runway that did not yet appear in the windscreen, and green lines showing the orientation of our destination runway.

Such tranquillity will soon have a much broader audience than the relatively few owners of large Gulfstream jets equipped with the SV-PFD,as a flurry of SVS activity in the business and general aviation sectors.

Close behind Honeywell's success on the Gulfstream is competitor Rockwell Collins with its Pro Line Fusion integrated avionics system, which includes SVS. As of June, Rockwell Collins had sold the system to five airframers, including Embraer for the Phenom 450 and 500, Bombardier for the Global 5000 series and new Learjet 85, and Cessna for the Citation Columbus.

Also making inroads is Garmin, whose portable and panel-mounted GPS navigation units are ubiquitous in GA cockpits. An SVS-capable version of the company's G1000 integrated avionics display, certificated with SVS in April, is available in Cirrus SR22 cockpits from this month as part of the new Cirrus "Perspective" avionics platform, which costs $48,000 more than the baseline Avidyne avionics package, which does not yet include SVS.

Knocking at the door at the entry level of the market are companies such as Blue Mountain, with portable SVS units in the $10,000 price range for experimental aircraft. Even Honeywell is delving into the lower-cost end of the sector with its recent acquisition of Mercury Computer Systems' VistaNav SVS-capable electronic flight bag, priced at less than $10,000 for a turnkey unit.

Honeywell plans to announce pricing for the reintroduced system in late July.

Regulatory Interest

Eyeing the commotion with keen interest is the US Federal Aviation Administration and its European counterparts. The US agency is considering a wide range of guidance or regulatory changes in the future, depending on the output of RTCA special committee 213 (SC213), a government/in­dus­try consensus-based group that is, at the request of the FAA, developing minimum aviation system performance standards (MASPS) for both the SVS and enhanced flight vision systems (EFVS) for smaller (Part 23) and transport-category (Part 25) aircraft that generally have more than a 5,670kg (12,500lb) maximum take-off weight.

As the body of knowledge the FAA draws upon to approve such systems is growing and becoming more streamlined, the process continues to evolve. Gulfstream, when seeking approval for its Part 25 SVS, chose to demonstrate that the vision system fits within the existing definitions for an attitude indicator, part of the FAA's regulatory guidance dealing with primary flight displays.

The airframer also worked with the FAA to develop an "issue paper" that addressed "the unique features of our new system", says Gulfstream. The paper included the definition of the intended function for the SV-PFD: terrain awareness, obstacle awareness and runway positioning. "This issue paper served as the basis for demonstrating SV-PFD and was found acceptable in the certification process for our Part 25 aircraft," Gulfstream adds.

 © Honeywell

The RTCA products are designed to streamline the process and make it definitive.

"Today there is a set of special conditions and set of letters against regulations you don't meet to gain certification," says Tim Etherington, a principal engineering manager in Rockwell Collins' advanced technology centre. "It is hoped that the MASPS will help replace or generalise the special conditions - in effect, make certification criteria known to the whole industry. We also hope to harmonise the rules between the European Aviation Safety Agency and the FAA."

Etherington says SC213 will complete the MASPS for SVS and EFVS by December, after which the group will consider how combined vision systems, some mix of synthetic and enhanced vision technologies, might be used to gain credit for lower approaches than currently allowed (see box). "I think our work will not be complete until we produce minimum operational performance standards that the FAA can use in a technical standard order for the equipment," says Etherington. The FAA has not yet tasked the group to develop the minimum operational performance standards, however.

Harmony Effort

In an effort to harmonise eventual FAA and EASA developments, Etherington says SC213 is likely to become a joint committee with Working Group 79 (WG79) of the European organisation for civil aviation equipment (Eurocae), a team tasked with developing similar synthetic and enhanced vision standards.

Etherington says the two are scheduled to have their first joint meeting in Bordeaux, France, in September.

Industry Considers Zero Zero VFR

A small group of government and industry representatives has begun crafting a concept of operations (conops) for how synthetic vision systems and infrared sensor-based enhanced flight vision systems (EFVS) might be combined to allow pilots to fly low-level, foul-weather, visual-flight-rules approaches, perhaps to the ground, with no supporting airport infrastructure, such as instrument lighting systems, to help in identifying the runway environment.

A subset of RTCA special committee 213, a consensus-based group charged with devising minimum performance standards for SVS and EFVS aids by December, the combined vision system working group is contemplating how the tools might be used to make Category 1-type approaches without relying on ground-based landing aids, including approach lights.

For Cat 1 instrument approaches, pilots depend on instruments with either satellite or ground-based input to fly within 200ft (60m) of the ground, but must then acquire a visual picture of the runway environment, which usually includes approach lighting systems, before descending.

Part 91 general aviation operators can obtain special approvals to go down to 100ft above ground with EFVS equipment and special training, but Part 135 and Part 121 operators cannot descend below 200ft if the airport is reporting visibility less than a required minimum regardless of the equipment on the aircraft or the crew's training.

"The FAA is looking to change that, but they don't know what they're going to do yet," says Tim Etherington, a principal engineering manager in Rockwell Collins' advanced technology centre. Rockwell Collins is developing an SVS-capable integrated avionics suite called Fusion, first due out in 2011 on Bombardier's Global family of aircraft. Etherington co-chairs RTCA SC213 with Patrick Krohn of Universal Avionics, which itself has a Part 25 certificated synthetic vision system called Vision-1.

In Europe, no credit is currently given to aircraft with EFVS, although industry observers in the USA expect European rules to be issued within six months, allowing properly trained crews to descend below 200ft using the equipment. Unlike the USA, Europe's rules do not distinguish between Part 91, Part 135 and Part 121 operations, leading to speculation that the FAA will alter the regulations to allow air taxis and airlines to do the same.

RTCA's combined vision system group hopes to take lowered minima to the next stage by combining hybrid vision technologies, augmented with millimetre-wave radar or other database- and real-time traffic verification tools, to allow pilots to land and take off under "equivalent" visual operations, a term coined by FAA associate administrator for aviation safety, Nicholas Sabatini.

"Our goal is the electronic VFR cockpit," says NASA Langley Research Center's Randy Bailey, the combined vision system working group lead. The group had originally intended to develop conops for combined vision systems to fly "VFR" all the way to landing, with the intention to determine the most realistic minimum altitude if using the system all the way to touchdown proved unworkable.

But, given that RTCA is consensus-based, the sense of the group during its first meeting in May was to see how combined vision systems might be used to get "credit" for lower than Cat 1 minimum descent altitudes, with an eye to eventually using the systems all the way to touchdown. Gulfstream and Bombardier have approvals that allow Part 91 operators of their certificated systems to use EFVS to reduce Cat 1 minimum altitudes to 100ft from 200ft, after which the pilots must be able to see the approach lights and runway.

"Today's ILS has a significant amount of lights and airport infrastructure," says Bailey. "We want to use combined vision systems to offload the airport requirements."

Included in the group's output, to be presented at a joint US and European RTCA 213 meeting in Bordeaux, France, in September, is what the combined vision system equipment will need to do to reduce minima and ease airport infrastructure burdens.

Enhanced vision (top left) provides a cloudless view of the runway, made all the more safe when combined with Gulfstream's synthetic vision (bottom left). Actual view from the windscreen is top right