Story ID: 459
Millimeter Wave Tech Powers Saab HUD
By: Matt Thurber
Caption: Landing in fog, rain, and clouds may become much easier with development of a new EFVS from Saab and Vu Systems.
Word Count: 824
The dream of marrying passive millimeter-wave (PMMW) technology with a head-up display is about to become reality with Vu Systems’s launch of a new enhanced flight vision system (EFVS) sensor in a partnership with avionics manufacturer Saab (Booth C11333). The Vu Cube PMMW sensor promises much better performance in low visibility compared to traditional enhanced vision system (infrared) sensors.

“We will be the first to market with this PMMW technology,” said Vu Systems CEO Stedman Stevens. “This allows aircraft access that we normally wouldn’t have to maintain a schedule in low-visibility conditions.”

Saab plans to use the Vu Cube as one of the sensors for its EFVS, which it has flight tested in a King Air 200 during more than 100 instrument approaches. Saab has also done extensive testing in a simulator with a variety of pilots. “We are talking with several aircraft manufacturers about different platforms,” said Jan Widerström, head of Avionics Systems at Saab.

Compared to infrared- and visible-sensor-based EFVS, the PMMW sensor offers many advantages, according to Stevens. The key to an EFVS is that it provides a “visual advantage” to pilots, helping them “see” further through clouds or visibility-obscuring phenomena than they can with normal eyesight. The greater the visual advantage, the further from the runway the pilots can see the runway and its environment and the greater the opportunity to be able to land despite the reduced visibility.

Basically, the one- to five-micron wavelength of infrared energy is smaller than the size of most fog (10 to 15 microns) and cloud (one to 100 microns) particles, according to Vu Systems. “The [fog or cloud] particles don’t have a chance to be attenuated or refracted because of the longer length of the wavelength” of about 3,000 microns, said Stevens. The result is that with the Vu Systems sensor, pilots can see the runway on the HUD from two for four miles, much further away than with infrared—affording a greater visual advantage.

“Today’s technology is based on [systems] that can’t see through water,” Widerström said. “Ours can see through clouds, rain, and fog, in miles [not feet]."

PMMW works because objects emit millimeter wave energy, and millimeter wave energy is reflected from the sky, according to Vu Systems. Ground objects have “warmer” emissions compared to the “cold” energy reflected from the sky, and a PMMW sensor can detect the difference in temperature between the runway environment and the surroundings.

A caveat that comes with PMMW technology is lower resolution. “That’s the nature of millimeter wave,” said Stevens. “It is not as crisp as a photograph or the eye [natural vision], but you can see through moisture without attenuation or diffraction. The resolution is less crisp so you need image enhancement on the edge to get the corners of the runway [more clear].”

A benefit of the Vu Systems PMMW sensor is that it isn’t subject to International Traffic in Arms Regulations restrictions, according to Stevens. And the timing that is bringing it to market is perfectly aligned with the FAA’s new EFVS regulations allowing lower landing minimums with advanced technology EFVS.

“The huge step that Vu Systems has taken is to take that research technology into something which is a product, to a size that can fit into aircraft,” said Saab’s Widerström. “We for sure haven’t done it, and I’m not aware of anyone else who has.”

Saab had been looking for opportunities to expand into the business aviation market, and the new FAA EFVS rules and Vu Systems developments matched Saab’s HUD developments. “We’re looking forward to taking this out on the market,” he said.

“We had heard Saab was developing a commercial version of their HUD,” Stevens said. And Saab has the qualifications and experience to manufacture the Vu Cube for Vu Systems.

The Vu Cube weighs less than 30 pounds and measures 17.75 by 9.5 by 10 inches. It mounts inside the airplane’s radome, but must not be too close to the radar antenna and needs to have a clear forward view at typical approach path angles.

The Saab EFVS would be a dual-sensor system, combining EVS and PMMW and displaying the imagery on a head-up display (HUD). “There is also the possibility to overlay synthetic vision where we get a total information situational awareness picture,” Widerström said. A Saab EFVS solution could have one or two HUDs, and its HUDs have a large field of view of 42 by 28 degrees. The system can be useful not just for takeoff and landing but in other flight regimes where a high visual advantage is useful.

“The goal together is to deliver an integrated, affordable system that [meets the new] EFVS [regulations],” said Stevens. “We’re creating a truly affordable integrated system.”