While synthetic vision creates virtual terrain from a database, enhanced vision (EV) is the real thing enhanced by thermal infrared imaging.
A hull-mounted IR sensor provides the EV video to a cockpit display that will support the technology.
All the pilot need then do is fly the aircraft by reference to the video screen, which should be showing them exactly what they would see outside if the viz was good enough.
As most EFIS systems that support video do so through the MFD, EV is most compatible with systems that enable the MFD to be in front of the handling pilot.
In some instances, these systems are good enough to be used in SAR operations and one of them has been credited with assisting in a rescue.
EV systems will prove to be most valuable at night and in some poor visibility conditions.
The capabilities of the unit should be checked first so you know in what situations it is unlikely to be of value.
Kollsman GAViS
Kollsman’s General Aviation Vision System (GAViS) consists of an IR sensor that provides analogue video to the cockpit display.
The pilots use that video as if they were looking out the window and fly the path or approach as they normally would.
The sensor is hull-mounted on the top or bottom of the aircraft at the front.
Naturally, the arc of view needs to be clear for unobstructed vision.
It mounts similar to a standard antenna and is covered by a fairing with a forward-looking window.
There are no modifications to the air frame, so certification is a lot easier to get.
A mounting plate between the fuselage and the fairing enables easy adaptation to most aircraft.
The sensor provides a 30 deg horizontal and 22 deg nominal field of view (FOV).
Anything outside this field will not appear on the screen.
It is sufficient, however for the operations where EV is needed the most: taxying, taking-off and landing at night.
GAViS can only be installed on aircraft that run a 28-volt electrical system.
Largely, that’s all there is to the system; it’s simple and effective but has huge advantages, particularly for night approaches.
Max-Viz
The MaxViz system displayed on a Garmin Cirrus Perspective MFD.
Max-Viz manufacture two basic types of enhanced vision system, the EVS 100 and the EVS 1500.
The EVS 100 is made to suit piston GA aircraft, low altitude turbo-props and piston helicopters, being restricted to use below 250 KTAS and FL250.
It consists of a long wavelength infrared (LWIR) sensor mounted externally and an internal monitor.
The sensor is mounted like a standard antenna on a forward part of the fuselage and covered by a fairing.
It can be mounted behind the prop without fear of the prop degrading the image.
A heating system is supplied so the fairing window is kept clear even in icing conditions, and a sun sensor protects the IR sensor from damage when the sun is in the direct field of view.
The EVS 100 has a healthy 40 deg horizontal and 30 deg vertical FOV, and integrated software optimises the received image through all phases of flight.
Max-Viz states that the mean time between failures for the EVS 100 is 10,000 hours, which means it may even outlast the air frame to which it is mounted.
The EVS 1500 is a more advanced system based on an uncooled microbolometer camera, which is reputed to provide better penetration of smoke, smog and water vapour.
This system can also be zoomed from telephoto to wide angle without loss of resolution, the wide angle being better for ground operations and the telephone enabling the pilot to pick up the runway earlier than usual.
Telephoto mode may even prove handy for checking for runway incursions when you are on final at night.
FOV ranges from 53 deg horizontal and 40 deg vertical in wide angle, to 30 deg x 22.5 deg in optical telephoto mode.
Given that Max-Viz are certifying the system for larger high-speed aircraft like the Gulfstream GIII, Falcon EX and Lear 60, it is fair to presume that it is not hampered by speed and altitude restrictions of the EVS 100.