All we need to solve these problems are the indices of refraction. Air has n1 = 1.00, water has n2 = 1.333, and crown glass has n′2=1.520. The equation [latex]\tan\theta_{\text{b}}=\frac{n_2}{n_1}\\[/latex] can be directly applied to find θb in each case.

To examine this further, consider the transverse waves in the ropes shown in Figure 3. The oscillations in one rope are in a vertical plane and are said to be vertically polarized. Those in the other rope are in a horizontal plane and are horizontally polarized. If a vertical slit is placed on the first rope, the waves pass through. However, a vertical slit blocks the horizontally polarized waves. For EM waves, the direction of the electric field is analogous to the disturbances on the ropes.

Figure 6. The effect of rotating two polarizing filters, where the first polarizes the light. (a) All of the polarized light is passed by the second polarizing filter, because its axis is parallel to the first. (b) As the second is rotated, only part of the light is passed. (c) When the second is perpendicular to the first, no light is passed. (d) In this photograph, a polarizing filter is placed above two others. Its axis is perpendicular to the filter on the right (dark area) and parallel to the filter on the left (lighter area). (credit: P.P. Urone)

Figure 6 shows the effect of two polarizing filters on originally unpolarized light. The first filter polarizes the light along its axis. When the axes of the first and second filters are aligned (parallel), then all of the polarized light passed by the first filter is also passed by the second. If the second polarizing filter is rotated, only the component of the light parallel to the second filter’s axis is passed. When the axes are perpendicular, no light is passed by the second.

Light is one type of electromagnetic (EM) wave. As noted earlier, EM waves are transverse waves consisting of varying electric and magnetic fields that oscillate perpendicular to the direction of propagation (see Figure 2). There are specific directions for the oscillations of the electric and magnetic fields. Polarization is the attribute that a wave’s oscillations have a definite direction relative to the direction of propagation of the wave. (This is not the same type of polarization as that discussed for the separation of charges.) Waves having such a direction are said to be polarized. For an EM wave, we define the direction of polarization to be the direction parallel to the electric field. Thus we can think of the electric field arrows as showing the direction of polarization, as in Figure 2.

Flying Garmin’s G1000 suite, with Synthetic Vision, “you only miss it when you don’t have it. By that, I mean it becomes as natural to you as looking out the window and seeing terrain on a VFR day. You don’t realize you are using it.” He explains that SV is “particularly comforting” on an instrument approach on a dark night. “We see the bull’s-eye on the end of the runway and see the runway number as you approach it. With no approach lights you can still see it just as clearly as if it were daylight,” he says.

Brewster’s angle: [latex]{\theta }_{\text{b}}={\tan}^{-1}\left(\frac{{n}_{2}}{{n}_{1}}\right)\\[/latex], where n2 is the index of refraction of the medium from which the light is reflected and n1 is the index of refraction of the medium in which the reflected light travels

17. (a) 2.07 × 10−2 °C/s; (b) Yes, the polarizing filters get hot because they absorb some of the lost energy from the sunlight.

What angle is needed between the direction of polarized light and the axis of a polarizing filter to reduce its intensity by 90.0%?

Figure 1. These two photographs of a river show the effect of a polarizing filter in reducing glare in light reflected from the surface of water. Part (b) of this Figure was taken with a polarizing filter and part (a) was not. As a result, the reflection of clouds and sky observed in part (a) is not observed in part (b). Polarizing sunglasses are particularly useful on snow and water. (credit: Amithshs, Wikimedia Commons)

If you hold your Polaroid sunglasses in front of you and rotate them while looking at blue sky, you will see the sky get bright and dim. This is a clear indication that light scattered by air is partially polarized. Figure 11 helps illustrate how this happens. Since light is a transverse EM wave, it vibrates the electrons of air molecules perpendicular to the direction it is traveling. The electrons then radiate like small antennae. Since they are oscillating perpendicular to the direction of the light ray, they produce EM radiation that is polarized perpendicular to the direction of the ray. When viewing the light along a line perpendicular to the original ray, as in Figure 11, there can be no polarization in the scattered light parallel to the original ray, because that would require the original ray to be a longitudinal wave. Along other directions, a component of the other polarization can be projected along the line of sight, and the scattered light will only be partially polarized. Furthermore, multiple scattering can bring light to your eyes from other directions and can contain different polarizations.

Glass and plastic become optically active when stressed; the greater the stress, the greater the effect. Optical stress analysis on complicated shapes can be performed by making plastic models of them and observing them through crossed filters, as seen in Figure 14. It is apparent that the effect depends on wavelength as well as stress. The wavelength dependence is sometimes also used for artistic purposes.

Astronics Corp’s Max-Vis-1500 EVS and its Max-Vis 600 are in service and being installed on a number of smaller corporate and GA twin and single-engine aircraft. It has supplemental type certificates (STCs) for King Air, Cessna 206 and several Falcon models (whose STC is owned by Duncan Aviation), and also for the Gulfstream G-3, 4,5 and Bombardier Global Express. Some are forward-fit, including those on the AgustaWestland helicopter. The company’s Max-Viz 600, a legacy system designed for smaller piston-type airplanes, is being flown on Challengers and is an option on the Cirrus and the Cessna Caravan. An STC is pending for the Pilatus PC-12.

Polaroid sunglasses are familiar to most of us. They have a special ability to cut the glare of light reflected from water or glass (see Figure 1). Polaroids have this ability because of a wave characteristic of light called polarization. What is polarization? How is it produced? What are some of its uses? The answers to these questions are related to the wave character of light.

When the intensity is reduced by 90.0%, it is 10.0% or 0.100 times its original value. That is, I = 0.100I0. Using this information, the equation I = I0 cos2 θ can be used to solve for the needed angle.

Mike McGraw, chairman and founder of Data Systems International, has been flying for 25 years and currently owns and operates a KingAir 350, “two-thirds for business and one-third for personal and charity,” he says.

Figure 15. Birefringent materials, such as the common mineral calcite, split unpolarized beams of light into two. The ordinary ray behaves as expected, but the extraordinary ray does not obey Snell’s law.

Honeywell’s SmartView Synthetic Vision System is certified and currently in use with a number of platforms, including  Gulfstream’s larger jets, the G450, 550 and 650 as part of Gulfstream’s PlaneView flight deck. It is also part of Dassault Falcon Jet’s EASy II platform available on the newer Falcon jets and is being integrated into the Pilatus PC-12. “SmartView combines terrain features, energy management, flight path vectors and runway approaches in 3-D format right in front of you on your display. You’re taking the HUD symbology and moving it head-down,” says Trish Ververs, Honeywell engineering fellow, advanced technology.

There is a range of optical effects used in sunglasses. Besides being Polaroid, other sunglasses have colored pigments embedded in them, while others use non-reflective or even reflective coatings. A recent development is photochromic lenses, which darken in the sunlight and become clear indoors. Photochromic lenses are embedded with organic microcrystalline molecules that change their properties when exposed to UV in sunlight, but become clear in artificial lighting with no UV.

Figure 13. Optical activity is the ability of some substances to rotate the plane of polarization of light passing through them. The rotation is detected with a polarizing filter or analyzer.

Figure 12. (a) Polarized light is rotated 90º by a liquid crystal and then passed by a polarizing filter that has its axis perpendicular to the original polarization direction. (b) When a voltage is applied to the liquid crystal, the polarized light is not rotated and is blocked by the filter, making the region dark in comparison with its surroundings. (c) LCDs can be made color specific, small, and fast enough to use in laptop computers and TVs. (credit: Jon Sullivan)

While you are undoubtedly aware of liquid crystal displays (LCDs) found in watches, calculators, computer screens, cellphones, flat screen televisions, and other myriad places, you may not be aware that they are based on polarization. Liquid crystals are so named because their molecules can be aligned even though they are in a liquid. Liquid crystals have the property that they can rotate the polarization of light passing through them by 90º. Furthermore, this property can be turned off by the application of a voltage, as illustrated in Figure 12. It is possible to manipulate this characteristic quickly and in small well-defined regions to create the contrast patterns we see in so many LCD devices.

So which system is best? Harpster has asked that question to pilots before, and he says it really depends on the runway they fly into. “Some are very concerned flying into airports where there are animals on the runway and so EVS would be beneficial since you can see aircraft ahead of you that may not have their lights on. But as far as making sure you are in proper alignment to an airport, then the SV would kick in,” says Harpster. “I’d have a tough time picking between the two — I might just go for both of them — like on the Universal solution (on the Falcon 900B) we put the SV on there and gave you the EVS system as well,” says Harpster.

Figure 8 illustrates what happens when unpolarized light is reflected from a surface. Vertically polarized light is preferentially refracted at the surface, so that the reflected light is left more horizontally polarized. The reasons for this phenomenon are beyond the scope of this text, but a convenient mnemonic for remembering this is to imagine the polarization direction to be like an arrow. Vertical polarization would be like an arrow perpendicular to the surface and would be more likely to stick and not be reflected. Horizontal polarization is like an arrow bouncing on its side and would be more likely to be reflected. Sunglasses with vertical axes would then block more reflected light than unpolarized light from other sources.

Light reflected at these angles could be completely blocked by a good polarizing filter held with its axis vertical. Brewster’s angle for water and air are similar to those for glass and air, so that sunglasses are equally effective for light reflected from either water or glass under similar circumstances. Light not reflected is refracted into these media. So at an incident angle equal to Brewster’s angle, the refracted light will be slightly polarized vertically. It will not be completely polarized vertically, because only a small fraction of the incident light is reflected, and so a significant amount of horizontally polarized light is refracted.

Tpl vision

“When I fly corporate, I fly with someone in the right seat. I still do all my personal flying and charitable stuff single pilot. I fly into high-density places like Los Angeles, San Francisco and New York City all the time as a single pilot. And it’s the best co-pilot you could ever have.” He cites the improved situational awareness of the SV combined with Garmin’s moving map display as providing “that security — plus the warning with the ground proximity warning system — all those features integrated together. It’s a great system,” he says.

Found a few years ago only on high-end, long-range business jets, EVS and SVS are now found in the cockpits of smaller jets, and single and twin-engine utility aircraft and helicopters. They are even making their way into the regional airline market. For the avionics providers, EVS and SVS are an integral part of new and upgraded avionics suites available in the aftermarket. Aircraft OEMs, responding to customer demands, are incorporating them as forward-fit in new business aircraft and in updates for their in-service aircraft. Completion centers are seeing a steady business in retrofitting earlier avionics platforms with these new features. The one territory not yet embarked upon is an EVS-SVS technology merge in a Combined Vision System (CVS), which would offer the safety and situational awareness benefits of both systems.

Figure 14. Optical stress analysis of a plastic lens placed between crossed polarizers. (credit: Infopro, Wikimedia Commons)

Figure 7. A polarizing filter transmits only the component of the wave parallel to its axis, , reducing the intensity of any light not polarized parallel to its axis.

“Compared to SV, which provides a nice overview of the terrain, we give you the details of the terrain,” Sumpter says. “We’re in the ‘what if’ business — what if you had to put down at night — in that field are trees, rocks and maybe a pond. SV doesn’t show that. EV can show you a fuel truck, or construction equipment, somewhere on the field. And wildlife is something people are telling us a lot about. There may be a deer or something on that runway — I can see that,” he says. However, SVS and EVS work in concert, he believes, and many operators are opting for a combined system.

Duncan Aviation, a major service and completion center, has completed a Falcon 900B retrofit with the new Universal EFI-890 cockpit, adding the Max-Viz EVS 1500 sensor along with Synthetic Vision. Duncan has completed some 15 EVS installations on F900s and Challengers, according to Gary Harpster, senior avionic sales rep. for Duncan. Harpster cited an operator flying an EVS-equipped Falcon 900B out of a Mexican airport in an area with frequent heavy fog. “With a lot of moisture in it, EVS doesn’t work so well. But the customer told me ‘it just works great’ helping pilots get in and out of that airport. … [pilots] tell you that Synthetic Vision is great for showing situational awareness in relationship to the terrain, but the EVS shows you the ‘real life’ situation,” Harpster says.

Figure 10 illustrates how the component of the electric field parallel to the long molecules is absorbed. An electromagnetic wave is composed of oscillating electric and magnetic fields. The electric field is strong compared with the magnetic field and is more effective in exerting force on charges in the molecules. The most affected charged particles are the electrons in the molecules, since electron masses are small. If the electron is forced to oscillate, it can absorb energy from the EM wave. This reduces the fields in the wave and, hence, reduces its intensity. In long molecules, electrons can more easily oscillate parallel to the molecule than in the perpendicular direction. The electrons are bound to the molecule and are more restricted in their movement perpendicular to the molecule. Thus, the electrons can absorb EM waves that have a component of their electric field parallel to the molecule. The electrons are much less responsive to electric fields perpendicular to the molecule and will allow those fields to pass. Thus the axis of the polarizing filter is perpendicular to the length of the molecule.

Elliott Aviation, based in Moline, Ill., has retrofitted more than 100 KingAir 90, 200 and 350 series aircraft with the Garmin G1000 avionics suite, which has SV as an option. “Out of the 110 airplanes we have converted with G1000, 99 percent accepted the SV option,” says Mark Wilken, director of avionics sales. Garmin’s G1000 flight deck integrates flight information features on a 15.1-inch MFD and two 10.4-inch PFDs. Customers include owner-operators, corporate flight departments, government special mission and medevac operators, and owners with aircraft to be sold.

Surace says that as SVS and EVS evolve, training is key. “Pilots today are different,” he says. “Folks coming into the cockpit in the next five to seven years are going to be coming out of the training schools having been trained in SV and coming to realize it and accept it.”

Figure 2. An EM wave, such as light, is a transverse wave. The electric and magnetic fields are perpendicular to the direction of propagation.

Gulfstream has chosen to present its EVS on a Rockwell Collins (Flight Dynamics unit) HUD, while others display it head-down. “Right now it is the same HUD for the entire fleet and the HUD-EVS is even available on the (midsize) G280 as an option,” Mena says. He prefers the EVS on the HUD because the pilot can look out the window while still taking in airspeed, altitude and the flight path vector guidance for precision control, in addition to the enhanced vision.

Another interesting phenomenon associated with polarized light is the ability of some crystals to split an unpolarized beam of light into two. Such crystals are said to be birefringent (see Figure 15). Each of the separated rays has a specific polarization. One behaves normally and is called the ordinary ray, whereas the other does not obey Snell’s law and is called the extraordinary ray. Birefringent crystals can be used to produce polarized beams from unpolarized light. Some birefringent materials preferentially absorb one of the polarizations. These materials are called dichroic and can produce polarization by this preferential absorption. This is fundamentally how polarizing filters and other polarizers work. The interested reader is invited to further pursue the numerous properties of materials related to polarization.

The Sun and many other light sources produce waves that are randomly polarized (see Figure 4). Such light is said to be unpolarized because it is composed of many waves with all possible directions of polarization. Polaroid materials, invented by the founder of Polaroid Corporation, Edwin Land, act as a polarizing slit for light, allowing only polarization in one direction to pass through. Polarizing filters are composed of long molecules aligned in one direction. Thinking of the molecules as many slits, analogous to those for the oscillating ropes, we can understand why only light with a specific polarization can get through. The axis of a polarizing filter is the direction along which the filter passes the electric field of an EM wave (see Figure 5).

While Combined Vision Systems (CVS) of a SVS-EVS fusion are envisioned in the future, Peterson says the Global G5000 and 6000 aircraft are equipped with SV both on the HUD and HDD, as well as an EV camera depicted on the HUD. This allows the crews to either look at the SV outside world or the EV world — however not in a combined system, but switching from one to the other. He says his company is following a roadmap that leads ultimately “to bringing a fused IR image and SV image together on a HUD — realizing the benefits of both systems.”

Figure 5. A polarizing filter has a polarization axis that acts as a slit passing through electric fields parallel to its direction. The direction of polarization of an EM wave is defined to be the direction of its electric field.

Smart vision Ring Light

Many crystals and solutions rotate the plane of polarization of light passing through them. Such substances are said to be optically active. Examples include sugar water, insulin, and collagen (see Figure 13). In addition to depending on the type of substance, the amount and direction of rotation depends on a number of factors. Among these is the concentration of the substance, the distance the light travels through it, and the wavelength of light. Optical activity is due to the asymmetric shape of molecules in the substance, such as being helical. Measurements of the rotation of polarized light passing through substances can thus be used to measure concentrations, a standard technique for sugars. It can also give information on the shapes of molecules, such as proteins, and factors that affect their shapes, such as temperature and pH.

Figure 9. Long molecules are aligned perpendicular to the axis of a polarizing filter. The component of the electric field in an EM wave perpendicular to these molecules passes through the filter, while the component parallel to the molecules is absorbed.

By now you can probably guess that Polaroid sunglasses cut the glare in reflected light because that light is polarized. You can check this for yourself by holding Polaroid sunglasses in front of you and rotating them while looking at light reflected from water or glass. As you rotate the sunglasses, you will notice the light gets bright and dim, but not completely black. This implies the reflected light is partially polarized and cannot be completely blocked by a polarizing filter.

polarization: the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave

Only the component of the EM wave parallel to the axis of a filter is passed. Let us call the angle between the direction of polarization and the axis of a filter θ. If the electric field has an amplitude E, then the transmitted part of the wave has an amplitude E cos θ (see Figure 7). Since the intensity of a wave is proportional to its amplitude squared, the intensity I of the transmitted wave is related to the incident wave by I = I0 cos2 θ, where I0 is the intensity of the polarized wave before passing through the filter. (The above equation is known as Malus’s law.)

ProLine 21, Collins’ earlier platform, is in service worldwide on more than 6,000 aircraft, he says, and adds that the company is in the process of certifying a ProLine 21 retrofit solution that would offer SV to those aircraft, as well as on ProLine 21 systems still in production.

Figure 4. The slender arrow represents a ray of unpolarized light. The bold arrows represent the direction of polarization of the individual waves composing the ray. Since the light is unpolarized, the arrows point in all directions.

[latex]\tan\theta_{\text{b}}=\frac{n_2}{n_1}\\[/latex] gives [latex]\tan\theta_{\text{b}}=\frac{n_2}{n_1}=\frac{1.333}{1.00}=1.333\\[/latex].

A fairly large angle between the direction of polarization and the filter axis is needed to reduce the intensity to 10.0% of its original value. This seems reasonable based on experimenting with polarizing films. It is interesting that, at an angle of 45º, the intensity is reduced to 50% of its original value (as you will show in this section’s Problems & Exercises). Note that 71.6º is 18.4º from reducing the intensity to zero, and that at an angle of 18.4º the intensity is reduced to 90.0% of its original value (as you will also show in Problems & Exercises), giving evidence of symmetry.

Polarizing filters have a polarization axis that acts as a slit. This slit passes electromagnetic waves (often visible light) that have an electric field parallel to the axis. This is accomplished with long molecules aligned perpendicular to the axis as shown in Figure 9.

Spectrum illumination

“We do a lot of ILS, and GPS/LPV with lateral guidance down to 250 feet ILS down to 200 feet. It’s just a great tool to have. And now that I’ve had it for these several years, I would certainly not have an airplane without it.

Figure 3. The transverse oscillations in one rope are in a vertical plane, and those in the other rope are in a horizontal plane. The first is said to be vertically polarized, and the other is said to be horizontally polarized. Vertical slits pass vertically polarized waves and block horizontally polarized waves.

Figure 11. Polarization by scattering. Unpolarized light scattering from air molecules shakes their electrons perpendicular to the direction of the original ray. The scattered light therefore has a polarization perpendicular to the original direction and none parallel to the original direction.

Since the part of the light that is not reflected is refracted, the amount of polarization depends on the indices of refraction of the media involved. It can be shown that reflected light is completely polarized at a angle of reflection θb, given by [latex]\tan\theta_{\text{b}}=\frac{n_2}{n_1}\\[/latex], where n1 is the medium in which the incident and reflected light travel and n2 is the index of refraction of the medium that forms the interface that reflects the light. This equation is known as Brewster’s law, and θb is known as Brewster’s angle, named after the 19th-century Scottish physicist who discovered them.

Photographs of the sky can be darkened by polarizing filters, a trick used by many photographers to make clouds brighter by contrast. Scattering from other particles, such as smoke or dust, can also polarize light. Detecting polarization in scattered EM waves can be a useful analytical tool in determining the scattering source.

Initial deliveries of Garmin’s new G5000 platform were expected by the end of last year (2013) with Synthetic Vision standard on new aircraft. Its earlier G1000, G2000 and G3000 suites have been offered with SVS either standard or as an option. “What we see is that on the higher-end aircraft like Gulfstreams, Citation Sovereign, M2 and Lear 70/75, and the new Cessna Longitude and Latitude, [the aircraft OEM] make that standard. On the lower end, it is an option,” says Bill Stone, Garmin’s senior business development manager for avionics products.

Peterson believes that SV technology promises to provide additional benefits in the form of lower approach minima necessary for airlines in making a value case for use of SV, and that the certification basis will need to be employed on a HUD.

Rockwell Collins makes a similar case for using EVS in combination with the HUD. “EVS brings the benefits of real-time thermal detection of the environment. But its downside,” he says, is that it is limited during heavy precipitation or other shrouding, and that in some cases newer (LED) technology runway lights requiring less power become “thermally invisible” to IR cameras. Rockwell Collins recently announced availability of a new product called EVS-3000 IR that is able to see into the energy spectrum emitted by LED lights.

The EVS “is an IR sensor that detects differences in temperature, so if you are flying at night, a mountain range heated during daytime will be visible to IR — so what we do is turn night into day,” says Grant Sumpter, MRO sales manager for Max-Vis, the Portland, Ore.-based unit of Astronics Corp. “But what we don’t do is see through a thick layer of marine fog, because we are an uncooled IR system.”

EFFILUX

Gulfstream has also worked with its large cabin avionics partner Honeywell to develop SVS that Honeywell calls Smart Vision, which displays on a 14-inch head-down Primary Flight Display (PFD) as part of Gulfstream’s Plane View avionics suite.

In flat screen LCD televisions, there is a large light at the back of the TV. The light travels to the front screen through millions of tiny units called pixels (picture elements). One of these is shown in Figure 12 (a) and (b). Each unit has three cells, with red, blue, or green filters, each controlled independently. When the voltage across a liquid crystal is switched off, the liquid crystal passes the light through the particular filter. One can vary the picture contrast by varying the strength of the voltage applied to the liquid crystal.

Enhanced Vision Systems (EVS) and Synthetic Vision Systems (SVS) have moved beyond the Sci-Fi realm where they were first imagined. Today, they are necessary situational awareness and safety features in modern cockpits of General Aviation (GA) aircraft almost ready to move into the air transport arena.

Rockwell Collins has certified Synthetic Vision on is latest ProLine Fusion suites on Bombardier Global 5000 and 6000 platforms (both on the captain’s HUD and also on HDD as basic equipment), while some other 120 aircraft are in the certification process says Craig Peterson, director of avionics and flight controls for Rockwell Collins.

Honeywell traces its heritage in Synthetic Vision to its Enhanced Ground Proximity Warning System (EGPWS) product that now is a staple in the aviation world. As the product line evolved, “we put it on a PFD to provide a real-world, out the window view, so the pilot could have better situational awareness, especially at night and in the weather,” says Larry Surace, director of advanced safety features for Honeywell Aerospace.

While SVS uses an upgradable database to portray recorded terrain features along and ahead of the aircraft’s flight path, EVS provides output from an infrared camera to penetrate fog and darkness, presenting a real-time picture of what is ahead of the plane. Although there are more SVS systems installed today on business and GA aircraft, EVS technology is just as mature. Gulfstream was the first to certify it for any civil aircraft back in 2001 — on a G-5.

While the Garmin upgrade costs about $350,000 the SV option costs $25,000. Being converted with the Universal EFI-890 suite, the Universal Vision One (SV) computer box is in the $60-$70,000 range according to Wilken, who is looking forward to Rockwell Collins’ introduction of Synthetic Vision for its ProLine 21 series cockpits in 2014. He said he is also awaiting the new Garmin G5000 cockpit scheduled for first retrofit on the Hawker 400XP scheduled for mid-2015.

Brewster’s law: [latex]\tan\theta_{\text{b}}=\frac{{n}_{2}}{{n}_{1}}\\[/latex], where n1 is the medium in which the incident and reflected light travel and n2 is the index of refraction of the medium that forms the interface that reflects the light

Figure 10. Artist’s conception of an electron in a long molecule oscillating parallel to the molecule. The oscillation of the electron absorbs energy and reduces the intensity of the component of the EM wave that is parallel to the molecule.

Find Polaroid sunglasses and rotate one while holding the other still and look at different surfaces and objects. Explain your observations. What is the difference in angle from when you see a maximum intensity to when you see a minimum intensity? Find a reflective glass surface and do the same. At what angle does the glass need to be oriented to give minimum glare?

Advanced illumination

One advantage going forward with Enhanced and Synthetic Vision is the “credit” given by the Federal Aviation Administration (FAA) to pursue lower landing minimums. In a recent notice of proposed rule making, the FAA would allow those operators with a qualified EFDS II (Enhanced Flight Display System) — which Gulfstream has — to continue the approach solely on the EFDS image and land using the system. “By using EVS on the HUD, you can continue below normal decision altitude — down to 100 feet using the EVS image alone — and then complete the landing with natural vision. However, with synthetic vision, which is not based on a real-time sensor, you cannot descend below published minimums,” Mena says.

Figure 8. Polarization by reflection. Unpolarized light has equal amounts of vertical and horizontal polarization. After interaction with a surface, the vertical components are preferentially absorbed or refracted, leaving the reflected light more horizontally polarized. This is akin to arrows striking on their sides bouncing off, whereas arrows striking on their tips go into the surface.

Another example is Dassault’s Falcon Jet, which has Synthetic Vision as an option on its head-down display (HDD) on all production Falcon 900 series, and its 2000 and 7X business jets as part of its EASy II avionics suite, says Woody Salant, director of avionics programs and pilot training for Dassault Falcon Jet. There are some 600 Falcons in service around the world with the EASy platform, he says. “Synthetic Vision is a game changer in terms of situational awareness,” Salant says. Even though displayed on the HDD, Dassault has chosen to harmonize it with the HUD. “You should be looking outside the cockpit when you are doing landings,” he says. He adds that in the new Falcon 5X, expected to enter service in 2017, SVS will be standard with the HUD. (Dassault is also known to be working on a combined EV-SV system that may be an option on the 5X or future aircraft.)

Honeywell is moving ahead on a CVS. “We have the depicted terrain from the database seamlessly interfacing it with the ‘out the window’ camera view, and we put that on our PFD with the navigational information,” Ververs says. “We’re working on it now and rapidly getting into a maturity state for both fixed-wing and helo.” The manufacturer is currently test flying the system on one of it planes. “I have seen the HW system — in fact I flew this week on their test aircraft. They are able to take the EV image almost like a picture within the SV,” Gulfstream’s Mena says.

“Initially we sold it as an STC [Supplemental Type Certificate], but once we understood the value of it, we elected to make it standard on all our large cabin aircraft,” says Mike Mena, director of advanced cockpit programs for Gulfstream Aerospace. The infrared camera, installed in the nose of the aircraft, projects an image onto the pilot’s Head-Up Display (HUD) that is conformal to the outside world. “It gives an outstanding image of the terrain in front of you and in low visibility conditions is able to cut through the fog and provide the image to the pilot in the event he can’t see,” Mena says.

Honeywell is currently working with the FAA and the European Aviation Safety Agency (EASA) on certification of SmartView to lower landing minimums with a goal of getting down to a 150-foot decision altitude initially. “That would allow a lot more landings than are currently being made,” Surace says.