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The road to zero-zero


Next-generation HUD and EFVS with Saab and Vu Systems.

Saab’s new HUD and EFVS with Vu Systems passive millimeter wave sensor will enable takeoff and landing in low visibility. It will provide reliable airport access in all weather, even for non-precision approaches, or approaches with high minimums.
By Glenn Connor
ATP. Cessna 425 President, Discover Technology Intl

Saab Avionics, a relatively new face in the bizjet world, made a splash at NBAA-BACE 2019. The company stepped out into the competition ring with several innovations and pioneering spirit.

Alongside Saab was the unveiling of a strategic partnership with Vu Systems, a technology startup with advanced passive millimeter wave sensors created to supply the customer demand for better and more reliable enhanced flight vision system (EFVS) weather performance.

The teaming of the 2 companies is said to have a single focus – the domination of the airborne market with the next generation of vision-based avionics systems. Announced by Saab were 3 significant new commercial avionics programs – a new line of commercial head-up displays (HUDs), a new and next-generation EFVS, and a radical new product and technology for aircraft overheat detection systems.

With so much emphasis by OEMs on performance for range and fuel efficiency, there seemed to be an unfulfilled need for out-of-the-box competitive avionics ideas keeping pace with the aircraft, so Saab brought its “Thinking Edge” motto and a new solution for the road to zero-zero.

Saab Aviation’s current customers

Saab’s customer base in aviation today ranges from Boeing and Airbus for large commercial transport aircraft with high-lift devices, flight control actuators and other electromechanical actuators, to international markets for fighter jets, air traffic control towers, and MRO activities supporting the Saab 340 and 2000 aircraft.

However, Saab is expansive and deep in technology beyond aerospace. The company manufactures not only aircraft but also submarines, ships, and tracked vehicles. A unique aspect of Saab is that it is an aircraft company that happens to have its own avionics company – and that’s where some serious magic takes place, beginning with the Saab’s new HUDs, flight displays and synthetic vision systems (SVS).

Comparison of infrared and passive millimeter wave sensor performance in terms of range and ability to see the runway. The goal of an integrated HUD EFVS is to enable reliable operations in weather, and alleviate safety concerns related to CFIT, LOC-I, and runway excursions.

New avionics

The entry into the SVS market is based on technology that is far ahead of conventional systems of today. Saab SVS is a very detailed high-resolution display that is more virtual than synthetic to the eye, and, when integrated with either a primary flight display (PFD) or a HUD, will provide a significant increase in situational awareness for the flightcrew in all phases of flight.

Saab’s new Over Heat Detection System (OHDS) is a lightweight high-tech instrument that can detect overheating due to bleed air leakage in an aircraft. The traditional method is to use a special type of electrical wiring filled with eutectic salt, which has a certain melting temperature.

Saab, however, developed a fiber-optical sensor that is placed throughout the bleed air ducts (and possible other areas) to provide an alert to high temperatures anywhere along the path of the fiber optic line. In addition, a special optical interrogator has been developed that reads the optical signals converted to temperatures, alerts, and warnings.

These developments result in ~90% weight savings and a drastically reduced number of components from conventional overheating detection systems, plus the ability to obtain instrumentation data almost anywhere in the aircraft. With a simplified low-weight, reliable system, aircraft and engine OEMs will be able to detect and measure fire hazzards, strain, and pressure within the structure of the aircraft.

Images from Saab’s aeronautical terrain elevation database and rendering software.

HUD offerings by Saab

Saab’s new HUD line offers an innovative solution. These HUDs are different in that the pilot sees a much larger total field of view, making it seen much easier on the eyes. The HUD eye box is a general area with the best viewing angle. From an optics perspective, it’s actually where all the light is being reflected by the combiner from the HUD projector, ideally at the pilot’s design eye position for the aircraft.

Most HUDs have a curved combiner glass, so the top part of the light reflected from the combiner and the bottom of the combiner need to be focused at this one point to provide the optimal field of view. However, some HUDs are lacking in terms of what is called instantaneous and total field of view. You can easily test this by closing one eye to compare how much of the total field of view you can see.

In the Saab HUD, the instantaneous and total field of view are practically the same. Another tech trick in Saab’s HUDs is a much larger eye motion box, which relaxes the viewer from a more typical rigid sitting position. This really helps during long periods of use. As a pilot, you are constantly scanning not only the HUD and EFVS, but the rest of the flightdeck.

With the Saab HUD, it seems that during the course of any cockpit routine, just sitting up naturally and looking back out of the cockpit window puts you into a position to see all that is in the HUD. Saab HUDs are specifically designed to integrate multiple EFVS and SVS images, supporting the move to combined vision that is now in play in the market.

The symbology requirements begin with a baseline, as required for certification, but Saab offers options for customer innovations as well. Other options are available for combiner size and type of HUD. Saab claims that its business and market goals are to provide affordable and highly capable HUDs, specifically dual-HUD configurations for new aircraft and aftermarket retrofit.

The company is aiming at the large-cabin bizjet and airline markets. Large aircraft numbers are in the thousands, and production rates for single-aisle planes over the next 20 years are expected to be very large.

A new-generation EFVS

The growth in global passenger demand and need for expanded airports for commercial use is also driving the EFVS market. New FAA regulation for commercial carriers went into effect in Mar 2018, followed by what seems to be a serious look by many air carriers.

With the publication of a new regulation in 2016 that allows landings without natural vision using EFVS, and now the transition for EFVS to Part 135 and Part 121 operations, the opportunity is there.

The strategic partnership with Vu Systems and Saab Avionics’ new HUD and EFVS with combined vision may be a game changer. Vu Systems has pushed the door wide open on a new generation of EFVS with its airborne passive millimeter wave camera. Operating at radio frequencies rather than on infrared, the Vu Cube actually penetrates or “sees through” clouds and fog at ranges of 2–4 miles, according to Vu Systems CEO Stedman Stevens.

Physics of millimeter wave sensors operating without limitations in weather has been known for some time. In the past, several development programs, beginning with the Bendix microwave sensor, the Texas Instruments independent landing monitor and, more recently, the USAF millimeter wave radar, proved that point.

However, after the research and test­ing proved successful, there was no commercial millimeter wave EFVS product. Consequently, the Vu Cube was developed as a commercial product. Unlike radiating or emitting devices such as radar, Vu Cube is passive, and views the forward scene much like a thermal camera.

The product is able to sense differences in temperature between both terrain and manmade objects such as runways, taxiways, vehicles, or hangars. Because it operates at the longer millimeter wavelength, Vu Cube sees through clouds and fog, as demonstrated in the company’s extensive flight tests.

When considering the best way to provide new EFVS products, Vu Systems does it differently, augmenting the current IR sensor products with a capability to penetrate weather to get the aircraft close enough in dense fog or hard deck ceilings so that the IR could offer some benefit.

The knowledge that weather (ceilings and visibility) is no longer a factor brings new possibilities to anyone who wants to be on time and improve the safety of the operation, especially scheduled air carriers and Part 135 operators. This new EFVS technology and performance capability removes the need for Cat II/III operations.

Now all you need is a long enough runway and a charted instrument approach. Saab had its eyes on both EFVS development and the market demands for a HUD packing something better than the conventional and costly products. As an integrated system that includes HUDs and a new EFVS camera, Saab and Vu concur that ceilings or low visibility become things of the past.

The cost benefit is an EFVS that performs reliably in weather, avoiding delays and maintaining schedule, which is what all flight de­partments want to offer to company executives.

Saab’s new SVS technology provides a very high-resolution depiction of the airport and terrain through the company’s HUD that is ahead of today’s conventional SVS.

The need for a visual advantage

The development by FAA of EFVS operational rules is based on compliance with the visual segment of the approach. In plain words, this means the ability of the EFVS sensor to view as the natural eye would see the typical visual cues such as approach lights, sequence flashers, the runway terminator light bar, runway, and touchdown zone.

When you look at every runway, the visual aids are present based on the type of instrument approach available – the more classic being an ILS. But with the GPS world and a hefty push by FAA for more GPS approaches, we now have thousands of LPV and RNAV approaches to runways that have very modest infrastructure, and the result is often higher minimums than a conventional ILS.

The challenge for approaches with high minimums is being able to see the required visual references with the naked eye or seeing with current EFVS equipment, which becomes difficult with the 1st-gener­ation of infrared products.

For example, say the RNAV minimums to a field with a DA were 500 ft and ¾ miles, but the weather was less than 100 ft ceiling and ¼ mile visibility. In this case, the pilot would need to see the standard visual references with EFVS at the 500 ft DA point, regardless of the weather. With today’s 1st generation infrared EFVS, success is based on what’s in the air.

In other words, it depends on how much water vapor there is between you and the runway. Often, in the case of 100–¼, with IR alone, it may not be your day. But with the Vu Cube passive millimeter wave EFVS, the ability to see and continue is now similar to that for an ILS: weather is never a factor. Moving to aircraft-centric capability is where many OEMs recognize an advantage, instead of relying on how the airport is equipped.

Safe access to places anywhere in the world is an important selling point, and is no doubt one of the reasons why EFVS today is standard equipage with all major bizjet OEMs. However, it is noteworthy that, even though EFVS has been around for more than 15 years, the vision systems concept is relatively new in the air transport segment.

FAA recently introduced the requirement for proof of a visual advantage for EFVS operations to land and dispatch under LOA or OPSPEC C048. The visual advantage demonstration is part of the certification process by the aircraft OEM or EFVS supplier, and is merely the difference in what the pilot can see with the natural eye versus what the EFVS sensor can see.

Results are used by FAA Flight Standards to establish in your OPSPEC or LOA the level of approval for an EFVS to land operation. FAA also factors the EFVS sensors’ performance into the dispatch approval of the operator, also part of the LOA. The goal of the Vu Cube is to enable reliable operations in all-weather visibility conditions at ranges measured in miles, according to Stevens.

His company’s analysis of the EFVS sensors visual advantage is that, “with the Vu Cube, all approaches will be available under all ceiling and visibility conditions.”

The next-generation flightdeck

Also at NBAA-BACE 2019, both companies laid out the integration of their products and how the combination will make a formidable team. The strategy, as argued by both Saab’s Jan Widerstrom and Vu System’s Stevens, is the economic value and reliable performance desired in all segments of aviation.

The move to the next generation EFVS with Saab’s HUD products looks to be a gamechanger. The ability to see through clouds and fog 100% of the time is not a claim, but a demonstrated capability by the company. New and affordable HUDs on the market with the new SVS capability are another significant consideration for the modern flightdeck.

Saab is well established around the world. And with its partnership with Vu Systems, a high-tech start up in North Carolina, there will be even more fun to watch.

Glenn Connor is president of Discov­er Technology Intl. He is a pilot and a researcher specializ­ing in the develop­ment of enhanced vision systems and advanced avionics.